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Where does isovolumetric relaxation occur on the LV pressure-volume loop?
Closure of aortic valve to opening of the mitral valve
Where does isovolumetric contraction occur on the LV pressure-volume loop?
Closure of the mitral valve to opening of the aortic valve
Describe the effect of hypercapnia on the cerebral and systemic vasculature
Dilation (increased CBF, decreased ICP)
Which is the most potent vasoconstrictor angiotensin II or ADH?
ADH (vasopressin)
What Swan-Ganz catheter data suggest left ventricular failure?
Decreased cardiac output and increased preload (cardiac index < 2 L/min/m^2, PCWP > 15-18 mm Hg)
What pulmonary capillary wedge pressure is indicative of heart failure?
Greater than 18 mm Hg
List 4 compensatory responses in the patient with cardiac failure
1. Increased left ventricular preload
2. Increased sympathetic tone
3. Activation of the renin-angiotensin-aldosterone system
4. Release of AVP
5. Ventricular hypertrophy
What monitoring is indicated for managing the patient with a history of congestive heart failure secondary to diastolic dysfunction?
CVP or PAC
Describe the mechanism of action of inamrinone (Inocor) and milrinone (Primacor)
Selective PDE III inhibitors (increased cAMP in cells). Cardiac = increased inotropy, Vasculature = smooth muscle relaxation, vasodilation and thus decreased systemic vascular resistance
What potential side effect occurs with inamrinone, but not milrinone?
Thrombocytopenia
Sodium nitroprusside contains 5 cyanide ions and may cause cyanide toxicity. What 3 reactions may cyanide ions undergo?
1. Binding to methemoglobin to form cyanomethemoglobin
2. Reaction with thiosulfate in the liver to produce thiocyanates, catalyzed by rhodase
3. Binding to tissue cytochrome oxidase, which interferes with normal oxygen utilization by the tissues
How do cyanide ions interfere with oxygen utilization at tissue cytochrome oxidase?
Uncouples oxidative phosphorylation preventing the formation of ATP
List the 4 hallmark signs and symptoms of cyanide toxicity
1. Metabolic acidosis (base deficit)
2. Cardiac arrhythmias
3. Increased venous oxygen content due to inhibition of cytochrome oxidase and consequent inability of cells to utilize oxygen
4. Tachyphylaxis
The patient administered sodium nitroprusside continuously presents with the following arterial blood gases (pH = 7.21, PaCO2 = 32, PaO2 =104, base excess = -10. What is your next action?
Turn off the nitroprusside drip
What is your concern with giving Dilantin to the hyperglycemic patient?
It partially inhibits insulin release and may lead to increased blood glucose levels in patients who are hyperglycemic
Describe the metabolism and elimination of adenosine
Eliminated by enzymatic clearance in less than 1 minute
Metabolized in the plasma, RBCs or vascular endothelium to inosine (deamination) or adenosine monophosphate (by phosphorylation)
What muscle acts as a barrier to regurgitation in the conscious subject?
Cricopharyngeus muscle
Identify the 9 laryngeal cartilages by paired and single in order from superior to inferior
Epiglottis, thyroid, cuneiform (paired), corniculate (paired), arytenoids (paired), and cricoid
What intrinsic muscles close the laryngeal inlet?
The aryepiglottic muscle pair
Laryngospasm is caused by stimulation of which nerve?
Superior laryngeal nerve
What percentage of a tidal volume breath is contributed by the diaphragm in the upright subject during quiet breathing?
1/3 to 1/2 (Assume 75% if orientation is omitted)
Define alveolar dead space. What causes alveolar dead space?
The volume of inhaled gas that enters nonperfused or poorly perfused alveoli. Inadequate perfusion of ventilated alveoli causes alveolar dead space.
Which zone of West shows the greatest increase in blood flow over the distance of the zone?
Zone 2, or the "waterfall zone"
Which zone of West has the maximal blood flow of any zone?
Zone 3, or the "distention zone"
What happens to pulmonary blood flow in zone 4 of the lungs?
Blood flow is reduced by gravitational compression of the lung parenchyma or by interstitial edema formation
What happens to the P50 when the oxyhemoglobin dissociation curve shifts rightward? Leftward?
P50 increases with a right shift and decreases with a left shift
What is the volume percent carbon dioxide content in room air? What is the partial pressure of CO2 in room air?
0.03%; 0.23 mm Hg
What are pulmonary J receptors?
Located in the walls of the pulmonary capillaries or in the interstitium. They are stimulated by pulmonary vascular congestion or an increase in pulmonary interstitial fluid volume, leading to tachypnea. They are responsible for the dyspnea encountered during pulmonary vascular congestion and edema secondary to left ventricular failure.
Which nerve fiber type innervates pulmonary J receptors?
Afferent slow-conducting nonmyelinated C fibers in the vagal nerves
What is the primary mechanism of hypoxemia in the patient with chronic obstructive pulmonary disease?
Regional mismatch of ventilation and perfusion
The chronic bronchitis patient requires oxygen therapy. What is your concern and what PaO2 should not be exceeded?
Increased CSF bicarbonate resets the central medullary chemoreceptors and decreases the central respiratory drive sensitivity to CO2. PaO2 > 60 diminishes peripheral chemoreceptor respiratory drive and the patient will hypoventilate.
Is tracheal stenosis an example of obstructive or restrictive pulmonary disease?
Tracheal stenosis is an extreme example of chronic obstructive pulmonary disease. It becomes symptomatic when the lumen of the trachea becomes less than 5 mm in diameter.
Is tracheal stenosis an example of intrathoracic or extrathoracic obstruction?
Fixed extrathoracic obstruction
What airway event may lead to the development of negative pressure pulmonary edema? Describe the mechanism.
As the patient breathes against a closed glottis during a laryngospasm, a more negative intrathoracic pressure is created. This promotes movement of fluid from the blood to the tissue and into the alveoli.
How is negative pressure pulmonary edema treated?
PEEP ventilation
List and describe the 5 types of hypoxia?
1. Hypoxic hypoxia - PaO2 is abnormally low (diffusion hypoxia)
2. Anemic hypoxia
3. Venous to arterial cardiac shunts
4. Histotoxic hypoxia - impaired cellular oxygen use (cyanide poisoning)
5. Pulmonary disease
Which respiratory volume or capacity does not change in obstructive pulmonary diseases?
Tidal volume
Describe the pulmonary mechanics alterations that occur in the patient with end stage scoliosis.
Reduced lung volumes and reduced chest wall compliance. Late stage: V/Q mismatching with hypoxia, increased PAP, hypercapnia, abnormal ventilatory CO2 response curve, increased work of breathing and cor pulmonale occur, eventually leading to cardiorespiratory failure.
The patient is scheduled for lung resection. Identify 5 findings that would reflect "low risk" postoperative disability.
FEV1 >2 L, MVV >50% predicted, predicted postoperative FEV1 >0.8 L and is 40% of predicted value, RV/TLC
Describe the following neuron morphologies: unipolar, bipolar, pseudo-unipolar, and multipolar. What morphology is most common in the human nervous system?
Unipolar: Single large extension from cell body
Bipolar: Short axon and short dendrite on either side of the soma
Pseudo-unipolar: One short branch from soma which splits into axon and dendrite
Multipolar: One axon and multiple dendrites ( most common type in the brain and nervous system overall)
What is the morphology of motor neurons? Of sensory neurons? Of special sense neurons?
Motor: Multipolar
Sensory: Pseudo-unipolar (dorsal root ganglion)
Special sense: Bipolar neurons (eyes, ears, and nose)
Unipolar neurons are only found in the lower invertebrates
Which neurotransmitter is the most common excitatory neurotransmitter in the central nervous system?
Glutamate
List 3 common ionotrpic glutamate receptors in the central nervous system. Which electrolytes pass through these receptors upon activation?
Ligand-gated NMDA, AMPA and kainate (Na+ and Ca++ in, K+ out)
What enzyme catalyzes the synthesis of acetylcholine? Where does the synthesis occur?
Choline acetyltransferase (choline and Acetyl-CoA) in the cytoplasm of nerve terminals
What membrane receptor is an ion channel for chloride flux? Is this receptor a ligand- or voltage-gated channel?
GABAa (ligand-gated)
When a ligand-gated GABAa channel opens, will chloride move from serum into the cell or from the cell into the serum? In terms of membrane potential and excitability what is the usual result?
Chloride moves from serum to cytoplasm resulting in an inhibitory postsynaptic potential.
Identify the 7 ligand binding sites of the GABAa receptor
1. GABA
2. Barbiturates
3. Benzodiazepines
4. Propofol
5. Steroids
6. Anesthetic/alcohol
7. Picrotoxin
What is the conus medullaris? What is the filum terminalis?
The conus medullaris is the blunt, tapering tip of the spinal cord. The pia alone continues from the conus medullaris and after piercing the dural sac, continues with a covering of dura to the coccyx, forming the filum terminalis. This is comprised of the pia and the dura matter.
Describe the boundaries of the epidural space, especially the membrane boundaries.
The epidural space lies between the meninges and the side of the vertebral canal. It is bounded cranially by the foramen magnum, caudally by the sacrococcygeal ligament, anteriorly by the posterier longitudinal ligament, laterally by the vertebral pedicles, and posteriorly by the ligamentum flavum.
Describe the boundaries of the subdural space.
A potential space between the dura mater and arachnoid mater
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