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Ambika K's List: MEDEDU

Proteinuria: how to evaluate an important finding. — Cleveland Clinic Journal of Medicine

approach to a patient with proteinuria

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med-algorithm on 2009-11-09
Is digoxin a drug of the past? — Cleveland Clinic Journal of Medicine

digoxin MOA diagram
digoxin blocks sodium-pot atpase pump & thus prevents removal of sodium ions from cell . this low ECF sodium inturn stops sodium-calcium exchanger to remove calcium from cell.

www.ccjm.org/...821.full.pdf+html - Preview

pharmacology on 2009-11-09
Skin Lesion Nomenclature Tutorials

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clinicalmed dermatology on 2009-11-09
Demonstrations - Thyroid Exam - Physical Diagnosis Skills - University of Washington School of Medicine

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clinicalmed thyroid on 2009-11-09
Neurological Examination

great detail

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clinicalmed Neurology starred on 2009-11-09
AUDITORY AND VESTIBULAR PATHWAYS

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ENT clinicalmed on 2009-11-07 and saved by 4 people
- Endolymph is very similar to intracellular
  fluid: it is high in potassium and low in sodium. The ionic composition
  is necessary for vestibular and auditory hair cells to function
  optimally. The space between the membranous and bony labyrinths
  is filled with perilymph, which is very much like normal
  cerebral spinal fluid.
- 27 more annotations...
- - As the stapes vibrates the oval window, the perilymph
    sloshes back and forth, vibrating the round window in a complementary
    rhythm. The membranous labyrinth is caught between the two, and
    bounces up and down with all this sloshing
  - As with almost all sensory neurons (the exception is in the retina),
    its cell body lies outside the CNS in a ganglion. In this case,
    the ganglion is stretched out along the spiralling center axis
    of the cochlea, and is named the spiral ganglion.
  - basilar membrane is actually thinner and narrower
    at the base of the cochlea than at the tip (apex), which seems
    backwards given that the cochlea is widest at the base. The properties
    of the basilar membrane change as its shape changes; just as with
    guitar strings, thin things vibrate to high pitches, and thick
    things vibrate to low pitches. This means that the basilar membrane
    vibrates to high frequencies at the base of the cochlea and to
    low frequencies at the apex. A hair cell at the base of the cochlea
    will respond best to high frequencies, since at those frequencies
    the basilar membrane underneath it will vibrate the most. The
    key idea is that although the hair cells are arranged in order
    along the basilar membrane, from high-frequency to low-frequency,
    it is the properties of the basilar membrane that set up this
    gradient, not the properties of the hair cells.
  - outer hair cells help to "sharpen the tuning".
    Outer hair cells can actually move (change length) in response
    to nerve stimulation. If they could push the basilar membrane
    up and down, they could amplify or damp vibrations at will, making
    the inner hair cells more or less responsive. (Just like you
    can push a child higher and higher on a swing or bring her to
    a halt - it's all in when you push.)
  - Something about this tight connection allows the timing of the
    signal to be preserved to the microsecond (action potentials are
    on the order of milliseconds, so it is no mean feat). The ventral
    cochlear nucleus cells then project to a collection of nuclei
    in the medulla called the superior olive. In the superior
    olive, the minute differences in the timing and loudness of the
    sound in each ear are compared, and from this you can determine
    the direction the sound came from. The superior olive then projects
    up to the inferior colliculus via a fiber tract called
    the lateral lemniscus.
  - The second stream of information starts in the dorsal
    cochlear nucleus. Unlike the exquisitely time-sensitive localization
    pathway, this stream analyzes the quality of sound. The dorsal
    cochlear nucleus, with fairly complex circuitry, picks apart the
    tiny frequency differences which make "bet" sound different
    from "bat" and "debt". This pathway projects
    directly to the inferior colliculus, also via the lateral lemniscus.
  - Notice that both pathways are bilateral. The consequence
    of this is that lesions anywhere along the pathway usually have
    no obvious effect on hearing. Deafness is essentially only caused
    by damage to the middle ear, cochlea, or auditory nerve.
  - From the inferior colliculus, both streams of information
    proceed to sensory thalamus. The auditory nucleus of thalamus
    is the medial geniculate nucleus. The medial geniculate
    projects to primary auditory cortex, located on the banks
    of the temporal lobes.
  - Fibers from the cochlear nuclei
    and the superior olive (not the inferior) travel up the
    lateral lemniscus (not the medial) to the inferior
    colliculus (not the superior), and then to the medial geniculate
    (not the lateral). Try remembering the mnemonic,
    
    "S-L-I-M" .
  - You must be able
    to detect rotation, such as what happens when you shake or nod
    your head. In physics, this is called angular acceleration.
    You must also be able to detect motion along a line - such as
    what happens when the elevator drops beneath you, or on a more
    subtle note, what happens when your body begins to lean to one
    side. This is called linear acceleration. The vestibular
    system is divided into two receptor organs to accomplish these
    tasks.
  - semicircular canals detect angular acceleration
  - continuous endolymph-filled
    hoop. The actual hair cells sit in a small swelling at the base
    called the ampula.
  - hair cells are arranged as a single tuft that
    projects up into a gelatinous mass, the cupula. When you
    turn your head in the plane of the canal, the inertia of the endolymph
    causes it to slosh against the cupula, deflecting the hair cells.
    Now, if you were to keep turning in circles, eventually the fluid
    would catch up with the canal, and there would be no more pressure
    on the cupula. If you stopped spinning, the moving fluid would
    slosh up against a suddenly still cupula, and you would feel as
    though you were turning in the other direction.
  - Each tuft of hair cells is polarized
    - if you push it one way, it will be excited, but if you push
    it the other way, it will be inhibited. This means that the canals
    on either side of the head will generally be operating in a push-pull
    rhythm; when one is excited, the other is inhibited
  - if both sides push at once,
    then you will feel debilitating vertigo and nausea. This is the
    reason that infections of the endolymph or damage to the inner
    ear can cause vertigo. However, if one vestibular nerve is cut,
    the brain will gradually get used to only listening to one side
    - this can actually be a treatment for intractable vertigo.
  - semicircular canals exert direct control over
    the eyes, so they can directly compensate for head movements.
    Recall that the eye is controlled by three pairs of muscles;
    the medial and lateral rectus, the superior and inferior rectus,
    and the inferior and superior oblique. You may also remember
    that their directions of motion seemed to be at crazy diagonals.
    Those same crazy diagonals are matched closely by the three planes
    of the semicircular canals, so that a single canal (in general)
    interacts with a single muscle pair. The entire compensatory
    reflex is called the vestibulo-ocular reflex (VOR).
  - If you move your head to the left, you will excite
    the left horizontal canal, inhibiting the right. To keep
    your eyes fixed on a stationary point, you need to fire the right
    lateral rectus and the left medial rectus, to move the eyes to
    the right.
  - The pathway is as follows: the vestibular nerve
    enters the brainstem and synapses in the vestibular nucleus.
    Cells that received information from the left horizontal canal
    project to the abducens nucleus on the right side, to stimulate
    the lateral rectus. They also project to the oculomotor nucleus
    on the left side, to stimulate the medial rectus. Although not
    shown on the diagram, the same vestibular cells also inhibit the
    opposing muscles (in this case, the right medial rectus, and the
    left lateral rectus).
  - right horizontal
    canal is wired to the complementary set of muscles. Since it
    is inhibited, it will not excite its target muscles (the right
    medial rectus and the left lateral rectus), nor will it inhibit
    the muscles you want to use
  - A great deal of the VOR axon traffic travels via
    a fiber highway called the MLF (medial longitudinal fasciculus).
    The integrity of this tract is crucial for the VOR to work properly.
    It is occasionally damaged by medial brainstem strokes.
  - The utricle and saccule detect linear acceleration.
    Each organ has a sheet of hair cells (the macula) whose cilia
    are embedded in a gelatinous mass, just like the semicircular
    canals. Unlike the canals, however, this gel has a clump of small
    crystals embedded in it, called an otolith (yes, all along you've
    had rocks in your head). The otoliths provide the inertia, so
    that when you move to one side, the otolith-gel mass drags on
    the hair cells. Once you are moving at a constant speed, such
    as in a car, the otoliths come to equilibrium and you no longer
    perceive the motion.
  - single
    sheet of hair cells can detect motion forward and back, side to
    side. Each macula can therefore cover two dimensions of movement.
    The utricle lays horizontally in the ear, and can detect any
    motion in the horizontal plane. The saccule is oriented vertically,
    so it can detect motion in the sagittal plane (up and down, forward
    and back).
    
    A major role of the saccule and utricle is to keep
    you vertically oriented with respect to gravity. If your head
    and body start to tilt, the vestibular nuclei will automatically
    compensate with the correct postural adjustments. This is not
    just something that happens if the floor tilts - if you watch
    someone trying to stand still, you will notice constant small
    wavers and rocking back and forth.
Receptive field - Wikipedia, the free encyclopedia

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ophthalmology on 2009-11-06
- There are two types of bipolar cells: "on-center" and "off-center". An on-center cell is stimulated when the center of its receptive field is exposed to light, and is inhibited when the surround is exposed to light. Off-center cells have just the opposite reaction.
- 3 more annotations...
- - Stimulation of the center of an on-center cell's receptive field produces depolarization and an increase in the firing of the ganglion cell, stimulation of the surround produces a Hyperpolarization and a decrease in the firing of the cell, and stimulation of both the center and surround produces only a mild response (due to mutual inhibition of center and surround). This prevents an overload of signals to the brain. An off-center cell is stimulated by activation of the surround and inhibited by stimulation of the center
  - The center-surround receptive field organization allows ganglion cells to transmit information not merely about whether photoreceptor cells are exposed to light, but also about the differences in firing rates of cells in the center and surround. This allows them to transmit information about contrast.
  - The receptive field tends to favor movement (such as a light or dark spot moving over the field, as in center-to-periphery (or vice versa)), as well as contours (due to their nonuniformity in the receptive fields).
Eye and Retina

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ophthalmology on 2009-11-06
- retina, seven
  layers of alternating cells and processes which convert a light
  signal into a neural signal ("signal transduction").
  The actual photoreceptors are the rods and cones,
  but the cells that transmit to the brain are the ganglion cells.
  The axons of these ganglion cells make up the optic nerve
- pupillary sphincter muscle constricts the pupil like a purse-string, and is under the control of the parasympathetic system. Therefore it is innervated by fibers from the oculomotor nerve which originate in the Edinger-Westphal nucleus of the midbrain.
- 15 more annotations...
- - pupillary dilator muscle is composed of radial fibers which pull the pupil open, and is controlled by the sympathetic system. Therefore it is innervated by post-ganglionic sympathetics from the superior cervical ganglion.
  - zonule fibers - hold the lens stretched out into
    a more disc-like shape. This shape allows for far-focusing. What
    happens when you need to near-focus? At this point the ciliary
    body, a hoop-like structure that supports the zonule fibers,
    comes into play. Imagine a spiderweb built into the opening of
    a drawstring purse, suspending a disk in the opening. When the
    purse is open, the spiderweb is taut. If you pull the drawstring,
    however, the web will go slack and collapse on itself. The ciliary
    body is the drawstring purse, in this analogy. The ciliary
    muscle within it is the drawstring. When the ciliary muscle
    contracts (this is also under parasympathetic control), the zonule
    fibers go slack, the suspended lens is released from their tension,
    and it is free to round up. This change is necessary for near-focusing.
    The entire process of adjusting the focus to different distances
    is called accommodation.
  - retina is a seven-layered structure
    involved in signal transduction. In general, dark "nuclear"
    or "cell" layers contain cell bodies, while pale "plexiform"
    layers contain axons and dendrites.
  - In the OPL photoreceptor axons
    contact the dendrites of bipolar cells and horizontal cells. Horizontal
    cells are interneurons which aid in signal processing.
  - In the IPL, bipolar axons contact
    ganglion cell dendrites and amacrine cells, another class of interneurons
  - The ganglion cells of the GCL send
    their axons through the OFL to the optic disk to make up the optic
    nerve. They travel all the way to the lateral geniculate nucleus.
  - fovea defines the center of the retina, and is the region of highest visual acuity. The fovea is directed towards whatever object you wish to study most closely - this sentence, at the moment. In the fovea there are almost exclusively cones, and they are at their highest density.
    The ratio of ganglion cells : photoreceptors is about 2 :1 here, the highest in the eye. In addition, at the fovea all of the other cell types squeeze out of the way to allow the most light to hit the cones. This makes the fovea visible microscopically. The blood vessels also skirt a wide margin around the fovea. The area in and around the fovea has a pale yellow pigmentation that is visible through an ophthalmoscope, and is called the macula.
  - ganglion cell axons all leave
    the eyeball at one location, the optic disk. At the optic
    disk all photoreceptors and accessory cells are pushed aside so
    the axons can penetrate the choroid and the sclera. This creates
    a hole in our vision, the blind spot. Normally each eye covers
    for the blind spot of the other, and the brain fills in missing
    information with whatever pattern surrounds the hole. Therefore
    we are not conscious of the blind spot.
  - Most cones lie in the fovea, whereas
    peripheral vision is dominated by rods. Overall, rods greatly
    outnumber cones. Review the characteristics of rods (black and
    white vision, very sensitive to low light) and cones (color vision,
    not so sensitive) and explain these phenomena:
    
    1. To see a faint star, you cannot
    look directly at it, but must look slightly to the side.
    
    2. A person with macular degeneration
    can become functionally blind, yet their night vision is not really
    affected. How would their color perception be?
  - - The cornea is continuous
    with the sclera, which in turn is continuous with the dura.
    
    - The choroid, a highly vascular,
    highly pigmented layer between the sclera and the retina, is continuous
    with the ciliary body and the iris. Do not confuse it with the
    pigment epithelium.
    
    - The pigment epithelium is
    a single cell layer thick, and comes from the outer layer of the
    original optic cup (a classic embryological "pushed-in
    ball"). In the mature retina it is pushed directly up next
    to the neural retina, which came from the inner layer of the optic
    cup. They are not fused together, however, and can separate along
    the old plane - a "separated" or "detached"
    retina.
  - If you were to record from a photoreceptor,
    you would find that it was "ON" (hyperpolarized, paradoxically)
    whenever light shone on it. If you recorded from a ganglion cell
    instead, you would find that diffuse light did little to the cell.
    However, the cell would respond well to a small spot of light,
    a small ring of light, or a light-dark edge. We say that this
    cell has a center-surround receptive field - the center
    must be mainly light and the surround mainly dark, or vice versa.
    What happens between the outer segment and the ganglion cell?
    This complex receptive field is created by the interneurons of
    the retina: the bipolar cells and the horizontal cells, primarily.
  - neighbor cones also excite horizontal cells. The horizontal cells send processes laterally and inhibit the center bipolar cell.
    
    So, what does diffuse light do? It excites the central bipolar cell, but also inhibits it via the neighbors. Result - the ganglion cell does not get excited. It continues to tick along at its normal, tonic rate.
  - our entire
    visual system exists to see borders and contours. We see the world
    as a pattern of lines, even things as complex as a face. We judge
    colors and brightness by comparison, not by any absolute scale.
    (Don't believe it? Put that teal scarf next to a blue shirt, you'll
    call it green. On a green coat, you'll call it blue.) This system
    of lateral inhibition in the retina is the first step towards
    sharpening contours and picking up on borders between light and
    dark. Diffuse light is ignored by the ganglion cell, but a sharp
    dot will really turn it on. Higher up in the cortex, all these
    dots will be combined into lines, which will be combined into
    curves, etc, etc.
Eye, Brain, and Vision

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ophthalmology clinicalexEYE on 2009-11-06
- Left:
  Four recordings from a typical on-
  
  center retinal ganglion cell. Each record is a
  
  single sweep of the oscilloscope, whose
  
  duration is 2.5 seconds. For a sweep this
  
  slow, the rising and falling phases of the
  
  impulse coalesce so that each spike appears
  
  as a vertical line. To the left the stimuli are
  
  shown. In the resting state at the top, there
  
  is no stimulus: firing is slow and more or
  
  less random. The lower three records show
  
  responses to a small (optimum size) spot, a
  
  large spot covering the receptive-field cen-
  
  ter and surround, and a ring covering the
  
  surround only. Right: Responses of an off-
  
  center retinal ganglion cell to the same set
  
  of stimuli shown at the left.
- 2 more annotations...
- - The
    two main types of retinal-ganglion-cell
    
    receptive fields are on center, with inhibi-
    
    tory surround, and off center, with excita-
    
    tory surround. "+" stands for regions giv-
    
    ing on responses, "—" for regions giving
    
    off responses.
    
    A
    cross section of the retina, about mid-
    
    way between the fovea and far periphery,
    
    where rods are more numerous than cones.
    
    From top to bottom is about one-quarter
    
    millimeter.
Central Visual Pathways

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clinicalexEYE ophthalmology on 2009-11-06 and saved by 2 people
- ganglion cell axons leave the retina, they
  travel through the optic nerve
- optic tract wraps around the cerebral
  peduncles of the midbrain to get to the lateral geniculate
  nucleus (LGN). The LGN is really a part of the thalamus,
  and remember that nothing gets up to cortex without synapsing
  in thalamus first (if the cortex is the boss, the thalamus is
  an excellent secretary). Almost all of the optic tract axons,
  therefore, synapse in the LGN. The remaining few branch off to
  synapse in nuclei of the midbrain: the superior colliculi
  and the pretectal area.
- 8 more annotations...
- - LGN send their axons directly
    to V1 (primary visual cortex, striate cortex, area 17)
    via the optic radiations. This highway of visual information
    courses through the white matter of the temporal and parietal
    lobes, and can be very vulnerable to strokes.
  - What we see can be divided into several categories
    of vision: color, linear pattern, motion, etc.
  - rods see only black and white, and can function in dim
    light, whereas cones can see all colors but require full light.
  - small ganglion cells that dominate in the fovea: they are
    color sensitive and are "fine-grained", meaning their
    receptive fields are small enough that they can pick up a high
    level of detail. These small cells are called P cells
    (P for parvo for small). The second type of ganglion
    cells have large dendritic arrays, and receive information from
    a wide radius of bipolar cells. They are mostly found in the
    peripheral retina, are not color-sensitive, and are "coarse-grained"
    and relatively insensitive to detail. Their main asset is that
    they are sensitive to motion - you can imagine that due to their
    width they can track a signal flashing across several bipolar
    cells. These are the M cells (M for magno ).
  - These two types of information, motion vs. color
    and form, are maintained in separate compartments all the way
    up the visual pathway. They are kept in separate layers in the
    LGN, enter V1 via separate sublayers (4Ca vs. 4Cb), and after
    passing through V2, go on to separate areas of associative cortex.
    In the end, the parietal visual cortical areas (such as
    MT and PP) end up dealing with motion of objects, navigation through
    the world, and spatial reasoning (which is essentially moving
    things around in your head). Temporal visual areas (such
    as V4 and IT) are involved with the complex perception of patterns
    and forms as recognizable objects.
  - few optic tract fibers which bypassed the LGN
    entirely, traveling instead to the less glamorous but equally
    essential midbrain. One of their targets in the midbrain is the
    pretectal area, which mediates the pupillary light reflex.
    This reflex can be demonstrated by shining a light in one eye;
    if all is working correctly, both pupils will constrict.
  - directly
    to the pretectal area. After synapsing, the information is sent
    to the Edinger-Westphal nuclei on both sides of
    the midbrain - this is the crucial step in ensuring that both
    eyes react to light. The Edinger-Westphal nuclei, via the IIIrd
    nerve, control the pupillary constrictors that narrow the
    pupils
The W.U.S.M. Neuroscience Tutorial

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Neurology on 2009-11-06 and saved by 39 people
Welcome to Hansen Nursing

acid-base balance

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clinicalmed on 2009-11-04
Human Embryology Animations

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precinicalmed embryology animation on 2009-11-04
Basic visual pathway

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clinicalexEYE ophthalmology on 2009-11-06 and saved by 2 people
- lateral geniculate
  nucleus (LGN), where all the axons must synapse. From there,
  the LGN axons fan out through the deep white matter of the brain
  as the optic radiations, which will ultimately travel to
  primary visual cortex
- The image projected onto your retina can be cut
  down the middle, with the fovea defining the center.
- 9 more annotations...
- - right nasal retina and
    the left temporal retina see pretty much the same thing. If you
    drew a line through the world at your nose, they would see everything
    to the right of that line. That field of view is called the right
    hemifield.
  - left half of the brain is only interested in visual
    input from the right side of the world. To insure that the brain
    doesn't get extraneous information, the fibers from the retina
    sort themselves out to separate right hemifield from left hemifield.
    Specifically, fibers from the nasal retinas cross over at
    the optic chiasm - whereas the temporal retinas, already positioned
    to see the opposite side of the world, do not cross.
  - before the chiasm will affect one
    eye, both hemifields - analogous to closing one eye. Damaging
    the pathway after the chiasm, though, will damage parts of both
    eyes, and only one hemifield. There is no easy way to imagine
    what this would look like. Your field of view would be only 90°,
    from straight ahead to one side.
  - strike through a pathway, follow the fibers back
  - record a loss of visual field
    is with two circles, called "perimetry charts" as below.
    You can think of these circles as a pair of goggles that the
    patient is looking through, and you blacken those parts of the
    goggles where vision is lost.
  - longer loop actually dives into
    the temporal lobe before it heads back to the occipital lobe.
    This group of fibers is called Meyer's loop. Recall that, since
    the lens inverts all images, the lower half of the retina sees
    the upper half of the world. This orientation is preserved through
    the pathway, so that the lower optic radiations, or Meyer's loop,
    are carrying information from the upper visual world.
  - calcarine sulcus on the medial surface
    of the occipital lobe. Primary visual cortex, or V1, is
    buried within this sulcus. In a fortuitous section, you may be
    able to see a fine white stripe running within the grey matter
    inside the sulcus. This stripe marks V1, and gives it a third
    name, striate cortex.
A Practical Guide to Clinical Medicine

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clinicalexEYE ophthalmology on 2009-11-04
- Damage to the nerves controlling these structures (Cranial Nerves
  3 and 7) can cause the upper or lower lids on one side to appear lower then
  the other.
- 33 more annotations...
- - invisible except for the fine blood vessels that run through
    it. When infected or otherwise inflamed, this layer can appear quite red,
    a condition known as conjunctivitis. Alternatively, the conjunctiva can appear
    pale if patient is very anemic. By gently applying pressure and pulling down
    and away on the skin below the lower lid, you can examine the conjunctival
    reflection, which is the best place to identify this finding.
  - minor
    trauma (cough, sneeze, or direct blow), a bleeding disorder or idiopathic.
    The resulting collection of blood is called a subconjunctival hemorrhage.
    While dramatic, it is generally self limited and does not affect vision.
  - patient is seated at a height
    such that their eyes are essentially on the same level as your own when you are
    standing next to them.
    Testing Extra-Occular Movements: Instruct the patient to follow your
    index finger with their eyes only (i.e. their head remains in one position)
    as you first move it to either the extreme right or left. Then, once you have
    the patient looking out laterally, have them follow your finger as you move
    it first up, then down. Now move your finger across to the other side and repeat.
    Your path should trace out the letter H. At the end, bring your finger directly
    in towards the patient's nose. This will cause the patient to look cross-eyed
    and the pupils should constrict, a response referred to as accommodation.
    Tracing out this path allows you to test each of the extra-occular muscles
    individually and avoids movements that are dependent on more then one muscle,
    as occurs if you have the patient look up or down while the pupil is oriented
    straight ahead. Assessments of both extra-occular movements and visual acuity
    are actually tests of cranial nerve (CN) function. CNs 3, 4, and 6 control movement
    and CN 2 vision
  - Disorders of eye movement can also be due to problems with the extraocular
    muscles themselves. For example, pictured below is a patient who has suffered
    a traumatic left orbital injury. The inferior rectus muscle has become entrapped
    within the resulting fracture, preventing the left eye from being able to
    look downward.
  - when the transmitted visual impulse is interrupted at
    some point in its path from the retina to the visual cortex in the back of
    the brain. You would, in general, only include a visual field assessment if
    the patient complained of loss of sight; in particular "blind spots" or "holes"
    in their vision.Visual fields can be crudely assessed as follows:
    
    The examiner should be nose to nose with the patient, separated by approximately
    8 to 12 inches.
    Each eye is checked separately. The examiner closes one eye and the
    patient closes the one opposite. The open eyes should then be staring
    directly at one another.
    The examiner should move their hand out towards the periphery of his/her
    visual field on the side where the eyes are open. The finger should be
    equidistant from both persons.
    The examiner should then move the wiggling finger in towards them, along
    an imaginary line drawn between the two persons.The patient and examiner
    should detect the finger at more or less the same time.
    The finger is then moved out to the diagonal corners of the field and
    moved inwards from each of these directions. Testing is then done starting
    at a point in front of the closed eyes. The wiggling finger is moved towards
    the open eyes.
    The other eye is then tested.
  - The normal pupil constricts when either exposed directly to bright light or
    when that same light is presented to the other eye, referred to as the consensual
    response. This is due to the fact that stimulation of the afferent (i.e. sensory,
    carried with CN 2) nerves in one eye will trigger efferent (i.e. motor, carried
    with CN 3) activation and subsequent constriction of the pupils of both eyes.
    Disease affecting either the efferent or afferent limbs will alter these responses
    accordingly. Also, processes which raise intracranial pressure (e.g. brain
    tumors, collections of blood) can cause CN 3 dysfunction, resulting in dilatation
    of the pupils and uresponsiveness to direct stimulation by light. To assess
    pupillary reactions, proceed as follows:
  - Instruct the patient to look towards a distant area in the room (e.g.
    the corner where the wall and ceiling meet) while keeping both of their
    eyes open. You may need to gently remind them throughout the exam to continue
    looking in that direction as it is very difficult to examine a roving eyeball.
    Do not ask them to focus on a specific object as this will lead to pupillary
    constriction.
  - adjust the light intensity to mid-range
    power. The cone of light produced should be a white, medium sized circle
  - size and shape of each pupil
  - assess whether each
    pupil constricts appropriately in response to direct and indirect stimulation
  - It may be hard to detect the consensual
    response if the lighting in your room is sub-optimal (i.e. if it's too dark,
    you won't be able to see the other eye). Note that you do not need to look
    through the viewing window of the scope to perform this part of the exam
    as you are essentially using it as a flashlight.
  - lenses vary in their ability to bend light and are numbered and color coded.
    The specific lens that allows you to see something in focus will vary with
    your distance from that structure as well as the refractive error of both
    your eyes and the patients. To better examine the sclera, conjunctiva, pupil,
    cornea or iris, start with the lens identified by a green 4 or 6.
    
    Now grasp the handle with your right hand (the following instructions
    are for examining the patient's right eye) such that your middle finger
    is resting on the lower, front aspect of the head of the opthalmoscope.
    
    Bring your right eye up to the viewing window. While you can either wear
    or remove your own glasses, the patient's should be taken off. It's OK to
    leave contacts in place.
    
    Take your left hand and place it on the patient's forehead and gently
    apply upward traction on the top lid with your thumb. This will "remind"
    them not to blink and let you know their precise location. Obviously, try
    not to poke them in the eye with this finger! Alternatively, you can place
    your left hand on the patient's shoulder as a means of keeping track of
    their location. Try to keep both of your eyes open when performing the exam
    as you might find it quite tiring to continually squint with the non-examining
    eye.
    
    Start approximately 15 cm from the patient and approach from about 15
    or 20 degrees to the left of center. When you look through the viewing window,
    the outer structures of the eye should come into sharp focus. If not, slowly
    move closer or further from the patient until these structures become clear.
    It takes a bit of experimentation to find the lens that is right for any
    given distance, so make lens changes slowly by rotating the adjustment wheel.
    There is no magic way of guessing which lens will allow the sharpest view.
    
    *Most clinicians don't perform a detailed examination of the outer
    structures of the eye if the patient has neither obvious abnormalities nor
    complaints referable to this region.
  - Viewing the Fundus (the retina and associated structures):
  - Repeat steps 1 thru 5 as above. Adjust the lens selection wheel
    so that 0 appears in the display window.
  - You should see a sparkly, orange-red
    color known as the red reflex. This is caused by light reflecting
    off of the retina
  - translucent structures which
    allow light to pass unimpeded from outside the eye to the retina become
    opacified and the red reflex is lost. In adults, this is most commonly
    associated with cataracts
  - Your middle finger, the one resting
    on the low front of the head piece, should be on or near the patient's cheek.
    Starting with the 0 lens in place, rotate the adjustment wheel counter clockwise.
    If you change lenses too quickly, you'll probably whizz right by the one
    that gives the sharpest picture, so be patient. In the event that this does
    not bring anything into focus, trying rotating the adjustment wheel in the
    opposite direction. It doesn't really matter what number lens is required
    to achieve the clearest view. Again, this will vary with the refractive
    error of both you and the patient.
  - Once you're close in and have the retina
    in clear view, you should only need to change the lens one or two clicks
    in order to keep all structures in focus as you scan across.
    
    You will only be able to see a relatively small segment of the retina
    at any one time. Your initial view will probably be of blood vessels on
    a random patch of retina
  - The retina has a refractile, orange-red appearance, varying a bit with the skin
    color and age of the patient. Fundoscopy provides important information as it
    not only enables you to detect diseases of the eyes but is also the only area
    of the body where small blood vessels can be studied with relative ease. There
    are a number of chronic systemic diseases (most commonly hypertension, diabetes
    and atherosclerosis) that affect vessels of this size
  - When you first visualize the retina, you will note branching blood vessels.
    The bigger, darker ones are the veins and the smaller, brighter red structures
    the arteries. Changes in the appearance of the arteries (copper wiring)
    as well as alterations in the arterial-venous crossing pattern (a-v nicking)
    occur with atherosclerosis and hypertension respectively (see any text for
    pictures). These vessels are more obvious in the superior and inferior aspects
    of the retina, with relative sparing of the temporal and medial regions.
  - Follow them
    in a direction that leads to less branching (i.e. towards the trunk). This
    will direct you towards the optic disc, the point at which the vessels enter
    the retina along with the head of the optic nerve. The edges of this round
    disc are sharp and well defined in the normal state. It should be a bit
    more yellow/orange when compared to the rest of the retina. At the center
    of the disc is the optic cup, a distinct circular area from which the blood
    vessels actually emerge. The disc is not located in the exact center of
    the retina but rather towards its medial/nasal aspect.
  - If you are unable to locate the disc after following the vessels
    in one direction, simply head the other way.
  - The macula is a region located lateral to the optic disc. It looks somewhat
    darker then the rest of the retina and, as opposed to the disc, has no distinct
    borders. The macula provides the sharpest vision. It can be best visualized
    by asking the patient to stare directly at the light of the opthalmoscope
    while you remain focused on a fixed area of the retina.
  - To view different areas, you'll have
    to shift the angle with which you peer through the pupil. This requires
    very small movements. Try to examine the entire structure systematically,
    looking up, down, left and right. You will undoubtedly have to remind the
    patient to continue looking straight ahead, else the fundus will be in continual
    motion and you will have no chance of finding anything.
Eye Simulation Page

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clinicalexEYE ophthalmology on 2009-11-04
Current therapies to shorten postoperative ileus — Cleveland Clinic Journal of Medicine

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surgery on 2009-11-03
- (colonic ileus) is often seen in elderly hospitalized patients with multiple medical comorbidities. Of note, it often occurs
  after surgery to parts of the body other than the abdomen, such as after orthopedic procedures.
- The small bowel normally resumes activity several hours after surgery, the stomach 24 to 48 hours after surgery, and the colon
  3 to 5 days after surgery.⁴ When postoperative ileus persists longer than this, it can be considered pathologic and is sometimes called paralytic ileus.^4,5
- 25 more annotations...
- - sympathetic nervous system inhibits the small bowel; the parasympathetic nervous system stimulates
  - Vagus nerve activity appears to be more important in the stomach, where it promotes receptive relaxation of the fundus and
    contraction of the antrum, facilitating gastric emptying.¹⁰ After vagotomy, emptying of liquids may be normal or accelerated, but emptying of solids is impaired. This can occur after
    peptic ulcer surgery but is more likely after gastric resection for malignancy or after inadvertent vagal nerve injury during
    antireflux surgery.
  - enteric nervous system in the small bowel is fundamentally different than the one in the colon in that the former contains
    gap junctions, allowing for coordinated electrical activity. Lacking these gap junctions, the colon depends more on input
    from the autonomic nervous system, perhaps explaining the longer recovery
  - most important nonadrenergic inhibitor of gastrointestinal
    motility is nitric oxide.
  - vasoactive intestinal peptide, substance P, calcitonin gene-related peptide, and
    endogenous opioids.¹³ Lack of duodenal-derived motilin is thought to be one cause of delayed gastric emptying after pancreaticoduodenectomy
  - surgical manipulation of the bowel induced an inflammatory cellular infiltrate in the bowel wall and diminished
    the response of smooth muscle to cholinergic stimulation. Cyclooxygenase-2, the enzymatic precursor to prostaglandins
  - Opiates delay colonic transit in postoperative patients, an effect that can be reversed by the narcotic antagonist naloxone
    (Narcan).¹⁸ This inhibitory effect is mediated by peripheral mu-opioid receptors. In a study of patients undergoing colectomy, the more
    morphine given, the longer the time to the return of bowel sounds and flatus and the first bowel movement.¹⁹
  - Nonsteroidal anti-inflammatory drugs such as ketorolac (Toradol) are attractive alternatives to opiate analgesics, both for
    their anti-inflammatory effect and for their opiatesparing properties. However, they can cause bleeding, renal insufficiency,
    and gastritis, drawbacks that limit their applicability and duration of use.
  - diagnosis of ileus is presumed
    once obstruction has been excluded.
  - Postoperative gastroparesis is usually suspected by its symptoms of early satiety, nausea, vomiting, eructation, and gastroesophageal
    reflux. Abdominal distention is usually not a prominent sign, but a succussion splash may be detected, indicating retention
    of food and liquid in the stomach.
  - meal of egg white labelled with technetium 99m sulfur colloid, and scanning is performed at specified intervals to measure
    the percent retention of the isotope. Retention of more than 10% at 4 hours is considered abnormal
  - Small-bowel ileus often presents like gastroparesis, except that it more often causes abdominal distention. Plain radiographs
    reveal air-fluid levels and dilated loops of bowel.
  - crampy abdominal pain, bowel sounds, and some bowel function implies a degree of mechanical obstruction. Plain radiographs
    showing “step-ladder” air-fluid levels also suggest obstruction. CT is more definitive in diagnosing obstruction by the presence
    of distended and decompressed bowel loops and may also reveal a source of obstruction (eg, postoperative interloop abscess).
  - Colonic ileus is also characterized by abdominal distention, sometimes marked. Although it is the colon that is primarily
    involved, upstream small-bowel dilatation can also be seen if the ileocecal valve is incompetent. The cecum often shows the
    greatest degree of dilatation on plain radiographs and is at the greatest risk of perforation. CT, contrast enema studies,
    and endoscopy help rule out mechanical obstruction due to volvulus or a mass lesion.
  - epidural catheter before surgery, which is left in place for postoperative
    pain control, or are given patient-controlled analgesia with a narcotic. Generally, the surgeon chooses the pain control method.
  - epidural anesthesia interferes with the afferent and efferent sympathetic reflex arcs.
  - systemic inflammatory response appears to be less vigorous after laparoscopic surgery
  - nothing by mouth or only minimal oral intake immediately after abdominal surgery, with or without
    nasogastric decompression. The role of nasogastric decompression has long been a topic of controversy. In a meta-analysis
    of 26 trials with 3,964 patients, the groups in which all patients routinely received a nasogastric tube had higher rates
    of pneumonia, fever, and atelectasis and longer duration to resumption of oral feeding
  - However, in selected
    cases they are useful for managing intractable vomiting and for preventing aspiration of gastric contents
  - feeding
    patients early in the course of their recovery is not detrimental and may in fact be beneficial.
  - Gum-chewing has been studied over the last decade as a form of sham feeding to stimulate bowel recovery after surgery. The
    presumed mechanism of action is vagal cholinergic (parasympathetic) stimulation of the gastrointestinal tract, similar to
    oral intake but with theoretically less risk of vomiting and aspiration.
  - Erythromycin is a macrolide antibiotic that is also a motilin receptor agonist
  - colonic ileus is highly responsive to drug therapy.
  - In cases in which neostigmine fails, decompressive colonoscopy can be done as a second-line measure.
  - Alvimopan (Entereg), a peripherally acting, mu-opioid receptor antagonist,
Diabetic Microvascular Complications: Slideshow

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endocrinology clinicalmed on 2009-10-29
Browse by Topic - American Family Physician® -- American Academy of Family Physicians

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medreference on 2009-10-28
Conjunctivitis - February 15, 1998 - American Family Physician

great briefing!

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ophthalmology conjunctivitis on 2009-10-27 and saved by 2 people
- . Sebaceous cell
  carcinoma that is invading the conjunctiva and the superficial cornea
- collagen vascular disease or the use of diuretics or
  antidepressant medications should alert the physician to the possibility of dry
  eyes.
- 48 more annotations...
- - Viral or chlamydial inclusion conjunctivitis typically presents with a
    small, tender, preauricular or submandibular lymph node. Toxic conjunctivitis
    secondary to topical medications can also produce a palpable preauricular node.
    Palpable adenopathy is rare in acute bacterial conjunctivitis. The exception is
    hyperacute conjunctivitis caused by infection with Neisseria species.
    
    Other facial clues to the etiology of conjunctivitis include the
    presence of herpes labialis or a dermatomal vesicular eruption suggestive of
    shingles.
  - cultures should be obtained in patients who have severe inflammation
    (e.g., hyperacute purulent conjunctivitis) or chronic or recurrent
    conjunctivitis. Cultures also should be obtained in patients who do not respond
  - copious yellow-green purulent discharge that
    reaccumulates after being wiped
  - rapidly progressive
  - Infected infants may also have other
    localized gonococcal infections, such as rhinitis or proctitis, or they may
    have disseminated gonococcal infection, such as arthritis, meningitis,
    pneumonia or sepsis.
  - eyelids are matted together on
    awakening. Conjunctival swelling and mild eyelid edema may be noted
  - S. pneumoniae and H. influenzae are
    more common in children, while S. aureus most frequently affects
    adults
  - Cultures should be obtained in certain patients, including young
    children and debilitated
  - Since most
    adult cases of acute bacterial conjunctivitis are caused by gram-positive
    organisms, it is best to choose an antibiotic with adequate gram-positive
    coverage (in particular, good staphylococcal coverage).
  - Streptococcus
    species
    
    Gram-negative
    organisms
    
    Escherichia coli
    
    Pseudomonas species
    Moraxella species
  - ointments are better tolerated by young children, who are less apt to complain
    about associated blurring of vision. Solutions are preferred by most
    adolescents and adults.
  - Aminoglycosides, such as gentamicin (Garamycin), tobramycin (Tobrex)
    and neomycin are inexpensive choices for the treatment of acute bacterial
    conjunctivitis. These agents provide good gram-negative coverage, but they have
    relatively poor gram-positive coverage, including incomplete coverage of
    Streptococcus and Staphylococcus species. Furthermore, aminoglycosides are
    associated with a relatively high incidence of toxicity to the corneal
    epithelium (primarily with prolonged use). Neomycin, in particular, can cause
    local oculocutaneous allergic reactions. For this reason, topical ophthalmic
    preparations containing neomycin probably should be avoided as first-line
    therapy.
  - sulfacetamide solution (Bleph-10) is still a commonly
    prescribed topical antibiotic for conjunctivitis. This bacteriostatic agent has
    weak to moderate activity against many gram-positive and gram-negative
    organisms
  - Stevens-Johnson syndrome.
  - Tetracycline is available only
    in an ointment form.
  - Although
    chloramphenicol is generally well tolerated, topical application of this agent
    has been associated with a few cases of aplastic anemia
  - Given the generally benign, self-limited nature of acute bacterial
    conjunctivitis, the high cost of topical fluoroquinolones, their poor coverage
    of Streptococcus species and the potential for developing resistant pathogens
    with indiscriminate use of this antibiotic class, the fluoroquinolones
    generally should be reserved for use in more severe ocular infections,
    including bacterial keratitis.
  - Chronic
    bacterial conjunctivitis is most commonly caused by Staphylococcus species,
    although other bacteria are occasionally involved. This type of conjunctivitis
    often develops in association with blepharitis, which is a common but often
    unrecognized inflammatory condition related to bacterial colonization of the
    eyelid margins. Some cases of chronic bacterial conjunctivitis are also
    associated with facial seborrhea.
  - flaky debris, erythema and warmth along
    the lid margins, as well as eyelash loss
  - meibomian glands are sebaceous glands that line the posterior lid
    margin behind the eyelashes. These glands secrete an important oily component
    of the tear film. When inflamed, the meibomian glands malfunction, producing
    chronic inflammation of the eyelid margins and the conjunctiva (Figure 6),
    as well as irritating dry-eye symptoms.
  - gland
    plugging
  - Blepharoconjunctivitis and meibomianitis are common associated
    findings in patients with acne rosacea. This skin disorder typically affects
    adults between 25 and 50 years of age and occurs more commonly in women than in
    men. Diagnostic clues include a history of periodic facial flushing (usually in
    response to the consumption of certain foods or alcohol) and the presence of
    erythematous and telangiectatic skin changes on the forehead, cheeks, chin and
    nose. Some patients also have acneiform lesions and rhinophyma.² Ocular findings include recurrent chalazia and
    styes secondary to chronic blepharitis and meibomianitis, as well as keratitis
    and dry eyes
  - Acne rosacea, with a chalazion of
    the left lower
  - hygiene using warm compresses and eyelid margin
    scrubs and the application of appropriate topical antimicrobials (e.g.,
    erythromycin).⁵ Patients with meibomianitis
    and acne rosacea often benefit from oral tetracycline therapy. Systemic
    tetracyclines are contraindicated in nursing mothers, pregnant women and
    children. Topical metronidazole (Metrogel) is helpful in some patients with
    acne rosacea.
  - Old trachoma, with scarring of the
    superior tarsal
  - tearing, conjunctival
    inflammation, moderate discharge and eyelid swelling five to 12 days after
    birth.¹² Ophthalmic referral is essential.
    Neonatal inclusion conjunctivitis usually responds to topical antibiotics.
    However, this condition can be associated with otitis media, and respiratory
    and gastrointestinal tract infections. Such infants should be treated with a
    two-week course of systemic erythromycin.
  - subacute or chronic
    infection characterized by unilateral or bilateral redness, mucopurulent
    discharge, a foreign-body sensation and preauricular adenopathy.
  - Treatment consists of a two- to three-week course of oral
    tetracycline, doxycycline, minocycline (Minocin) or erythromycin. A single 1-g
    dose of azithromycin (Zithromax) is recommended for adults with lower genital
    tract infection, but a longer course may be necessary in patients with
    chlamydial conjunctivitis
  - Adenovirus is by far the most common
  - community epidemics, with the virus transmitted
    in schools, workplaces and physicians' offices.
  - Occasionally,
    patients also have subconjunctival hemorrhage
  - Some patients have an associated upper
    respiratory tract infection.
  - contagious for at least seven days,
    patients should be instructed to avoid direct contact with other persons
  - Cold
    compresses and topical vasoconstrictors may provide symptomatic relief. Topical
    antibiotics are rarely necessary, because secondary bacterial infection is
    uncommon
  - subconjunctival hemorrhage
  - follicular reaction
  - Herpes simplex virus keratoconjunctivitis can closely mimic the
    presentation of ocular adenovirus infection. In such patients, topical
    corticosteroid therapy can lead to severe ocular complications as a result of
    uncontrolled virus proliferation. Therefore, topical corticosteroids should not
    be used in the management of infectious conjunctivitis unless under the
    direction of an ophthalmologist. Furthermore, viral conjunctivitis is generally
    benign and self-limited. Treatment with corticosteroids can prolong the course
    of the disease and also place the patient at risk for other steroid-induced
    ocular complications, such as glaucoma and cataracts.
  - Ocular herpes simplex and herpes zoster are
    often managed with topical and/or systemic antiviral agents. Various topical
    agents, including trifluridine (Viroptic), may be helpful. Useful systemic
    antiviral agents include acyclovir (Zovirax), famciclovir (Famvir) and
    valacyclovir (Valtrex).
  - intermittent bouts of itching, tearing, redness and mild eyelid
    swelling. The personal or family history is often positive for other atopic
    conditions, such as allergic rhinitis, asthma or eczema.
  - allergen avoidance, cold compresses, vasoconstrictors, antihistamine drops,
    topical nonsteroidal anti-inflammatory agents and mast-cell stabilizers such as
    cromolyn sodium (Crolom) or lodoxamide
  - levocabastine (Livostin), which is a topical antihistamine, and with ketorolac
    tromethamine (Acular) and diclofenac sodium (Voltaren), which are topical
    nonsteroidal anti-inflammatory
  - severe
    cases, a short course of topical corticosteroids is often required for adequate
    symptomatic relief