Mixed Review
What colloid solution exerts the strongest colloidal osmotic effect?
10% Dextran 40, able to retain 30 mL of fluid for each gram administered, exerts the highest colloidal osmotic effect followed by 25% albumin, 6% hetastarch, and finally, plasma.
Which prostanoid is implicated in the rebound prothrombotic state often seen following discontinuation of antiplatelet therapy?
An increased thromboxane A2 (TxA2) activity is seen during the rebound prothrombotic period following discontinuation of antiplatelet therapy.
Antiemetic agents typically block one (or more) of six receptors—list these six receptors.
Antiemetic agents are usually antagonists at: (1) dopamine receptors (D2); (2) histamine receptors (H1); (3) muscarinic ACh receptors; (4) serotonin receptors (5-HT3); (5) GABAA receptors; and, (6) NK1 (neurokinin-1) receptors.
You are preparing to anesthetize a pediatric patient with Arnold-Chiari malformation. What is true regarding the care of a patient with this condition?
Arnold-Chiari malformation almost always coexists with myelodysplasia and involves the caudal displacement of the cerebellar vermis, fourth ventricle, and lower brainstem below the level of the foramen magnum. Medullary cord compression can occur, particularly with extension of the neck and patients may present with symptoms such as vocal cord paralysis, swallowing dysfunction, and chronic pulmonary aspiration. Surgical correction is usually performed by a decompressive suboccipital craniectomy with cervical laminectomies to relieve the compression. Because of cranial nerve and brainstem dysfunction, children with this disorder may have abnormal responses to hypoxia and hypercarbia.
What is not a standard ASA monitor during MAC?
According to the standards set forth by the ASA, the patient's oxygenation, ventilation, circulation, and temperature shall be continually monitored. This includes pulse oximetry, ECG, and blood pressure (which must be assessed at least every five minutes). During monitored anesthesia care cases, capnography is not required, but ventilation must be assessed, at least, by continual observation of qualitative clinical signs (e.g. chest rise and breath sounds).
What action do leukotrienes (LT) have on the lungs? What cells synthesize and release LTs?
Activated mast cells and basophils synthesize and release leukotrienes. Leukotrienes evoke inflammatory responses in the lungs including intense bronchoconstriction and increased pulmonary vascular permeability. Leukotrienes also promote eosinophil degranulation and attract neutrophils, both key players in the inflammatory response.
List seven (7) common adverse effects of metoclopramide.
Adverse effects of metoclopramide are: (1) treatable hypotension and tachycardia (most common adverse effects, according to Miller); (2) sedation; (3) restlessness or 'nervousness'; (4) extrapyramidal symptoms; (5) abdominal cramping following rapid intravenous injection; (6) inhibition of plasma cholinesterase; and, (7) galactorrhea.
What type of sepsis is most associated with DIC?
Although DIC may occur in relation to gram-positive or even viral or fungal infections, it is most strongly associated with gram-negative sepsis. Placenta previa, abruption, amniotic fluid embolism, or the presence of a dead fetus late in pregnancy can result in DIC. Tumor lysis syndrome can precipitate DIC. Prolonged surgery and surgery for certain procedures such as prostatectomy for carcinoma, liver transplantation, and coronary bypass surgery are associated with significant bleeding abnormalities.
Which pulse oximetry site would respond the slowest to changes in oxygen saturation?
Although it is the most commonly used location, the fingers respond slower to changes in oxygen saturation than more centrally placed locations such as the ear, nose, or forehead. The more central locations are also more resistant to vasoconstriction from cold or reduced perfusion.
Hepatic dysfunction due to biliary tract obstruction would be consistent with which laboratory finding?
Biliary stones are considered a posthepatic cause of hepatic dysfunction and are associated with an increased conjugated fraction of bilirubin, normal to slightly increased aminotransferase enzymes, and most notably, markedly increased alkaline phosphatase levels.
An important early step in hemostasis is vasoconstriction of the damaged vessel. Platelets play a key role in this initial vasoconstriction by release of what substances?
Blood vessel walls immediately contract following injury thus decreasing blood flow. The vascular contraction is a result of autonomic nervous system reflexes and the release of thromboxane A2 (TxA2) and ADP from platelets.
What is brachytherapy?
Brachytherapy derives from the Greek meaning 'short distance' and involves the placement of radioactive materials close to the site of a tumor to treat cancer. An interstitial perineal template implant is a form of brachytherapy used to treat gynecologic cancer, as is intracavitary insertion. External-beam radiation therapy is often combined with brachytherapy in the treatment of the cancer, but is not a 'short distance' treatment. Neither rib resection nor stellate ganglion block are related to brachytherapy.
At what age (months) is the mean alveolar concentration (MAC) highest? Which agent is the exception to this rule?
By 6 months of age, the mean alveolar concentration (MAC) is 50% greater compared to adult MAC (1.5x). For example, the MAC of desflurane for a 6-month old is 9.9% compared to 5.8% for the adult. The exception to this rule is sevoflurane: the MAC of sevoflurane is greatest in the neonate (3.3%), compared to 2% for the adult.
What causes EXTRINSIC restrictive lung disease?
Chronic extrinsic restrictive lung disease is often due to deformities of the thoracic cage such as pectus carinatum, pectus excavatum, kyphosis, scoliosis, and flail chest as well as obesity and neuromuscular disorders. Sarcoidosis is a cause of chronic intrinsic restrictive lung disease.
Dressler's syndrome is?
Dresslers syndrome is a form of pericarditis seen following myocardial infarction.
The endothelium releases many procoagulant factors following vascular injury: name two key procoagulants released by the endothelium.
Endothelial damage following vascular injury initiates release of many procoagulant factors including tissue factor (FIII, TF) and factor VIII:vWF (von Willibrand's factor).
The lungs have a dual blood supply, bronchial arteries and pulmonary arteries. Where do the bronchial arteries arise and which lung tissues are supplied by bronchial arteries?
High-pressure, low-flow bronchial arteries arise from the descending thoracic aorta and supply systemic arterial (oxygenated) blood to bronchi and bronchioles, terminating at the respiratory bronchioles. The bronchial arteries also supply the supporting tissues of the lungs including nerves, pulmonary vessels and visceral pleura.
Rank the three major sensory-evoked responses — somatosensory (SSEP), visual (VEP), and brainstem/auditory (BAPE) — based upon sensitivity to anesthetic agents.
In general, cortical evoked potentials with long latency involving multiple synapses are exquisitely sensitive to the influence of anesthetic while short latency brainstem and spinal components are resistant to anesthetic influence. Thus, BAEP can be recorded under any anesthetic technique, whereas VEP and SSEP are very sensitive to anesthetic agents. Mnemonic: Visual are Very, Somatosensory are Somewhat, and Brainstem are Barely sensitive.
How soon following the removal of an epidural may LMWH be given?
If LMWH is planned postoperatively the epidural catheter should be removed no sooner than 2 hours before the first dose. If the patient is already on LMWH, the catheter should be removed at least 10 hours after the most recent dose and at least 2 hours before the next dose.
Describe type I allergic (hypersensitivity) reactions: include participating cells and antibody(ies) and list common examples of type I reactions.
In type I allergic reactions (immediate-type, anaphylactic), a specific antigen — called an allergen — interacts with specific IgE antibodies on tissue mast cells or circulating basophils to trigger mediator release. The key mediator of type I reactions is histamine. Examples of type I reactions are allergic rhinitis, extrinsic asthma, and anaphylaxis.
What 12-lead electrocardiographic changes would be consistent with inferior subendocardial injury?
Injury to the myocardial cells results when the ischemic process is more severe. Subendocardial injury on a surface ECG is manifested by ST segment depression, and subepicardial or transmural injury is manifested as ST segment elevation. The leads that represent the inferior aspect of the heart are leads II, III, and aVF. The leads that represent the anterior aspect of the heart include leads V1-V4, and leads I, aVL, V5, and V6 represent the lateral aspect.
How are leukotrienes related to eicosanoids?
Leukotrienes are metabolic derivatives of arachidonic acid, therefore leukotrienes (LT) are a category of eicosanoids. Lipoxygenase (LOX) acts on arachidonic acid to produce the leukotriene family. Leukotrienes LTC4, LTD4, LTE4, and LTB4 increase smooth muscle contraction, microvascular permeability, and airway mucus secretion.
Local anesthetics exert their action by blocking what?
Local anesthetics bind to the alpha-subunit on sodium channels on the INSIDE of the cell membrane and block the large influx of sodium into the cell associated with depolarization.
Which patients are at an increased risk for the development of latex allergy than the general population?
People with frequent exposure to latex are at an increased risk for the development of latex allergy. A higher than normal association with this risk is exhibited in hospital and healthcare workers, patients with spina bifida and spinal cord abnormalities, and patients with genitourinary defects.
You have just intubated a 70 Kg patient suffering from severe burns of the face and head and entire anterior torso. You start an intravenous line and begin administering fluids. You know that the initial fluid resuscitation volume to be infused over the first 24 hours is about what?
The formula for determining the amount of fluid to administer in the first 24 hours is % body surface area X Kg X 2 to 4. This patient has suffered a 27% burn (18% for the anterior trunk and 9% for the face and head). This creates a range of fluid administration between and 3780 and 7560 mLs, making 5,000 mLs the best answer.
The lungs have a dual blood supply, bronchial arteries and pulmonary arteries. Where do the pulmonary arteries arise and what lung tissues are supplied by pulmonary arteries?
The low-pressure, high-flow pulmonary arteries supply venous blood flow to the structures distal to the terminal bronchioles, including distal nonrespiratory tissues and the alveolar capillaries where gas exchange occurs. The pulmonary artery arises from the right ventricle and branches into the right and left pulmonary arteries, which further branch to accompany the bronchi.
A lumbar sympathetic block should be performed at which spinal level?
The sympathetic nerves to the lower extremities leave the spinal cord above the L2 level and pass through a 'gateway' sympathetic ganglion at the L2 level. A lumbar sympathetic block can be achieved by performing a single local anesthetic injection just below that at the L3 level.
During the perioperative evaluation, you discover that a patient with a pacemaker occasionally experiences dizziness while exercising his chest muscles. Based on this finding, which of the following would you avoid during his anesthetic?
This indicates that myopotentials may be inhibiting the pacemaker. From this information, you know that muscle fasciculations from succinylcholine should be avoided to prevent inadvertent pacemaker inhibition.
Which prostanoid produces vascular smooth muscle contraction and is thus a potent vasoconstrictor?
Thromboxane A2 (TxA2) produces contraction of vascular smooth muscle and is a potent vasoconstrictor. TxA2 has local effects at the systemic vasculature, coronary vasculature, and renal vasculature (decreased RBF and decreased GFR).
Drugs that antagonize what receptors increase gastric pH and decrease gastric volume?
h-2 blockers raise gastric pH AND decrease gastric volume three examples: cimetidine (Tagamet) ranitidine (Zantac) famotidine (Pepcid)
What is the MOA of most diuretics (except mannitol)?
inhibit the reabsorption of Na+ NaCl excretion increases H2O excretion increases plasma volume decreases plasma osmolality should remain unchanged
Which H2 receptor antagonist produces the largest decrease in gastric volume and increase in pH?
ranitidine is 5-8x more potent and longer lasting
What properties of mannitol permit it to produce an osmotic diuresis?
although small, mannitol is IMPERMEABLE because it is highly polar --> rapid osmotic shift of water from the ICF to the ECF
Which diuretic is commonly used to decrease IOP?
acetazolamide (Diamox) is a CAI and the most common medication used to decrease IOP
Where do carbonic anhydrase inhibitors work?
act at the proximal tubules
Where does spironolactone work and how?
acts as a competitive antagonist of aldosterone primarily at sites on the COLLECTING DUCT
What type of metabolic disturbances may result from lasix? How about acetazolamide (Diamox)?
lasix = hypokalemia and metabolic ALKALOSIS diamox = hyperchloremic metabolic ACIDOSIS
Where does lasix exert its action? How?
lasix: Loop diuretic thick ascending limb of the loop of Henle blockade of the sodium-potassium-chloride symporter causing a profound increase in urinary excretion of sodium and chloride
Define "MET." as used in a preop eval
A MET is a Metabolic EquivalenT and is defined as the amount of oxygen consumed while sitting at rest. MET are used to evaluate functional capacity and reserve. A standard MET is equal to 3.5 mL O2/kg/min.
Which areas of the lower leg would still have sensation after the successful performance of a popliteal block on a patient?
A popliteal fossa blockade can anesthetize the nerves of the lower leg. However, a supplementary femoral nerve block is required to block its terminal saphenous branch which innervates the medial anterior calf and the dorsum of the foot.
What is anaphylaxis?
Anaphylaxis is a severe, generalized, life-threatening immediate hypersensitivity reaction marked by interstitial edema—particularly laryngeal edema—bronchospasm, and cardiovascular collapse. The most common type of immune-mediated anaphylaxis results when previous exposure to antigens in drugs or foods evokes production of antigen-specific IgE antibodies. Subsequent exposure to the same or a chemically similar antigen results in antigenantibody interactions that initiate marked degranulation of mast cells and basophils. Urticaria and pruritus are common.
Define autacoid. List examples of autacoids.
Autacoids (or autocoids) are biological factors that act like local hormones, that is they have a paracrine (neighboring) effect. Unlike hormones, autacoids are produced in minute quantities and have local, evanescent (brief) effects. Notable human autacoids include eicosanoids, angiotensin, nitric oxide (NO), kinins, histamine, serotonin, and endothelins.
State four (4) contraindications to administration of metoclopramide.
Because of its antidopaminergic activity, metoclopramide should be used with caution if at all in patients with: (1) Parkinson's disease; (2) restless leg syndrome; (3) or who have movement disorders related to dopamine inhibition or depletion. Metoclopramide is contraindicated in patients with (4) intestinal obstruction, due to metoclopramide's prokinetic effects.
What are two (2) side effects of giving mannitol?
Because the administration of mannitol results in an acute increase in plasma and extracellular osmolality, fluid shifts from the intracellular space into the extracellular space and eventually the intravascular compartment resulting in congestive heart failure. Additionally, the increase in plasma volume results in hemodilution which can present as transient hyponatremia and a drop in hematocrit.
Which diuretic works by decreasing sodium reabsorption and hydrogen ion secretion in the proximal tubules?
Carbonic anhydrase inhibitors such as acetazolamide decrease sodium reabsorption and H+ secretion in the proximal tubules. They can result in a mild hyperchloremic metabolic acidosis.
A patient undergoes a six hour long abdominal surgery in the dorsal decubitus (supine) position. On awakening, the patient exhibits weak thumb abduction, inability to extend the metacarpophalangeal joints, and loss of sensation in the web space between the thumb and index finger. You suspect damage to what nerve?
Damage to the radial nerve (arising from the C6-T1 nerve roots) can result in weak thumb abduction, inability to extend the metacarpophalangeal joints, and loss of sensation in the web space between the thumb and index finger. Common causes include pressure from the vertical bar of an anesthesia screen and excessive cycling of an automatic blood pressure cuff.
List 4 reasons why dextrans are of limited use nowadays.
Dextrans are relatively inexpensive (dextrans are produced by bacteria), but their range of toxicities limits their use. Dextran toxicities include: (1) antithrombotic effects, particularly inhibition of platelet aggregation; (2) interference with blood cross-matching — dextrans coat RBC membranes; (3) anaphylactic and anaphylactoid reactions; and, (4) renal dysfunction resulting from osmotic nephrosis.
List two anesthetic techniques to abolish the obturator reflex during transurethral resection of the bladder tumors (TURBT).
During transurethral resection of a laterally located bladder tumors (TURBT), every use of the cautery resectoscope results in stimulation of the obturator nerve producing violent contraction of the ipsilateral thigh muscles and consequent adduction of the thigh (lower extremity). "Urologists rarely derive amusement from having their ear struck by the patient's knee ..." (Butterworth). Therefore, in contrast to TURP, TURBT procedures are more commonly performed with (1) general anesthesia and neuromuscular blockage or (2) neuraxial anesthesia to T9-T10 providing adequate anesthesia and preventing the obturator reflex.
What is the cause of edema in a head up position?
Edema of the face, neck, and tongue in head up positions, including severe postoperative macroglossia, is purportedly due to venous and lymphatic obstruction caused by prolonged, marked neck flexion.
Metabolic equivalents (METs) range from 1 to 12 (in whole numbers). Correlate equivalent levels of exercise with 5, 6, 7, and 8 METs.
Five metabolic equivalents (5 METs) correlates with climbing one flight of stairs, bicycling or dancing. Six metabolic equivalents (6 METs) is equal to playing golf or carrying golf clubs. 7 METs correlates to playing singles tennis. Rapidly climbing stairs or slowly jogging is equivalent to 8 METs.
The patient with chronic renal failure is taking antacids for "gastric distress." The EKG shows a shortened QT interval and a widened QRS complex. What has caused these EKG changes?
Hypercalcemia. EKG changes with hypercalcemia = shortened QT interval and a widened QRS complex
Which of the following is a cause of polycythemia without an increase in total red cell mass?
Hypovolemia results in an elevated hematocrit because of the decreased volume in which the red cell mass resides without an actual increase in red cell mass. Chronic lung disease and living at high altitudes both result in a compensatory increase in red cell mass and an increased hematocrit as a compensatory mechanism to increase tissue perfusion in the face of decreased blood oxygen levels. Hypoxia is associated with an increased red cell mass.
How long does spinal shock last?
In patients who survive, spinal shock can last 1-3 weeks.
Which unipolar lead in the 5-lead monitoring system is preferred when arrhythmias are anticipated? Which unipolar leads are preferred for monitoring ischemia?
In the 5-lead system, V1 is preferred for special arrhythmia monitoring, whereas V3 to V5 are the preferred leads for monitoring ischemia.
Left bundle branch block (LBBB) and right bundle branch block (RBBB) are both characterized by a heart rate <100 bpm, regular rhythm, normal PR interval, QRS complex >120 ms (0.12 s), and ST-segment and T waves in the opposite direction of the R wave. What features uniquely identify LBBB?
Left bundle branch block (LBBB) is uniquely characterized by: (1) a broad, sometimes notched R wave in left side leads (I, aVL, V5, V6); (2) deep S waves in the right precordial leads; (3) absent septal Q waves.
What three (3) maternal catastrophes pose the greatest acute risks to the fetus during nonobstetric surgery during pregnancy?
Maternal catastrophes involving severe hypoxia, hypotension, and acidosis pose the greatest acute risk to the fetus during nonobstetric surgery during pregnancy.
You are evaluating a patient who has survived breast cancer and is now presenting for a mammoplasty. What chemotherapy agent would warrant further investigation into her current hepatic function?
Methotrexate can produce renal and hepatic dysfunction. Doxarubicin (Adriamycin) can result in cardiomyopathy and congestive heart failure. Cyclophosphamide is an alkylating agent that can produce pulmonary toxicity and pulmonary fibrosis. Paclitaxel is a taxane that can produce peripheral neuropathy.
Which dopamine antagonist is the only FDA-approved agent for treatment of diabetic gastroparesis?
Metoclopramide is the only drug approved by the FDA for diabetic gastroparesis. Metoclopramide, via cholinergic stimulation, acts as a gastrointestinal prokinetic drug that increases lower esophageal sphincter tone and stimulates motility of the upper gastrointestinal tract.
What is the only indication for intravenous levothyroxine?
Myxedema coma is the only true indication for intravenous administration of levothyroxine. It is administered as a 300-500 mcg loading dose followed by 50-200 mcg/day. A TSH level of 5.0 mU/L indicates a euthyroid state. Diastolic dysfunction in hypothyroid patients is often reversed by routine treatment with oral levothyroxine.
A patient undergoing surgical excision of an insulinoma is most likely to exhibit intraoperative what?
Neoplasm of the beta cells of the pancreas is referred to as insulinoma. The primary manifestation of this disorder is hypersecretion of insulin, resulting in severe hypoglycemia leading to mental depression, seizures, and coma. Surgical excision of the tumor is the primary form of treatment unless the patient has advanced metastatic disease.
Metabolic equivalents (METs) range from 1 to 12 (in whole numbers). Correlate equivalent levels of exercise with 9, 10, 11, and 12 METs.
Nine metabolic equivalents (9 METs) correlates with jumping rope slowly or moderate cycling. Ten metabolic equivalents (10 METs) is equal to swimming quickly, running or jogging briskly. 11 METs correlates to cross country skiing or playing full court basketball. Running rapidly for moderate to long distances is equivalent to 12 METs.
Which is a potential disadvantage of using nitroglycerin for controlled hypotension?
Nitroglycerin preserves cardiac perfusion well, but can increase intracranial pressure.
How does non-immune-mediated anaphylaxis (also known as anaphylactoid reaction) compare with anaphylaxis?
Non-immune-mediated anaphylaxis (also known as anaphylactoid reaction) is nearly identical to anaphylaxis; however, the triggering antigen directly stimulates mast cell and basophils— there is no IgE-mediated trigger. Symptoms of non-immune-mediated anaphylaxis are generally less severe than IgE-mediated anaphylaxis.
What diagnostic parameter is the most sensitive indicator of the effect of obesity on pulmonary function?
Obesity decreases respiratory compliance due to the accumulation of fat on the chest wall, diaphragm, and abdomen resulting in a decrease in functional residual capacity, vital capacity, and total lung capacity. The reduction in functional residual capacity is due to a reduction in the expiratory reserve volume, which is the most sensitive indicator of the effect of obesity on pulmonary function. Minute ventilation is increased in obese patients to meet the metabolic demand of excess fat.
Metabolic equivalents (METs) range from 1 to 12 (in whole numbers). Correlate equivalent levels of exercise with 1, 2, 3, and 4 METs.
One metabolic equivalent (1 MET) correlates with eating, working at a computer, or dressing. Two metabolic equivalents (2 METs) is equal to walking down stairs, walking in your house, or cooking. 3 METs correlates to walking one or two blocks on level ground. Raking leaves or gardening is equivalent to 4 METs.
What volume of anesthetic vapor is produced by 1 milliliter of volatile anesthetic liquid?
One milliliter of liquid volatile anesthetic produces ~200 milliliters of anesthetic vapor at 20 ºC and 1 atmosphere.
List two prostanoids that cause bronchodilation. List three prostanoids that cause bronchoconstriction.
PGE2 and PGI2 are bronchodilators, whereas PGF2α, PGD2, and TxA2 cause bronchoconstriction.
What surgical procedure would you expect to have the highest risk for the development of acute pancreatitis postoperatively?
Pancreatitis may occur postoperatively in association with abdominal and thoracic surgery, particularly after cardiopulmonary bypass.
What cardiovascular abnormalities are consistent with morbid obesity?
Patients with morbid obesity have a larger total blood volume than non-obese patients to supply the excess adipose tissue. The excess blood volume and resulting increase in preload causes ventricular dilation and increased left ventricular wall stress (eccentric hypertrophy). Obese patients have a faster rise in cardiac output in response to exercise than non-obese patients, fueled primarily by an increase in heart rate as the stroke volume changes little with exertion. The chronically elevated cardiac output and increased blood volume may result in an increase in the SVR over time.
What agents can produce burst suppression on an electroencephalogram?
Propofol, etomidate, and thiopental are both capable of producing burst suppression on an EEG as well as producing an isoelectric EEG and are, therefore, capable of providing a degree of neuroprotection. Neither midazolam or ketamine are capable of producing this effect.
What are the symptoms of hyperglycemic hyperosmolar syndrome?
Polyuria, polydipsia, hypotension, tachycardia, hyperosmolarity (>340 mOsm/L) and hypoperfusion of major organs. Intravascular coagulation and mesenteric thrombosis are a significant risk in hyperglycemic hyperosmolar syndrome.
Where do diuretics exert their action?
Potassium-sparing diuretics work in the collecting duct of the nephron where they inactivate an aldosterone-sensitive sodium channel which promotes retention of both sodium and potassium. Loop diuretics act in the thick ascending loop of Henle which is responsible for active reabsorption of 25% of the filtered sodium, potassium, and chloride as well as some passive reabsorption of magnesium and calcium. Thiazide diuretics act in the distal convoluted tubule which is responsible for actively absorbing a small amount of sodium and chloride as well as the calcium reabsorption that is under the control of the parathyroid gland. Carbonic anhydrase inhibitors act on the proximal convoluted tubule, which is responsible for reabsorption of almost 100% of glucose and amino acids and about 65% of filtered sodium, potassium, calcium and magnesium.
What indicates a proper understanding of how to apply the thumb and forefinger against the cricoid cartilage when performing the Sellick maneuver?
Proper application of the Sellick maneuver calls for application of the BURP method (Back, Upward, and Rightward Pressure) directly on top of the cricoid cartilage until the fingers blanch. The reason for the directional component of this technique is because in about 75% of patients, the esophagus is slightly to the right of the trachea, so moving the cricoid cartilage downward, upward, and to the right should occlude the esophagus in most patients.
Which form of airway gas analysis involves energizing the gas sample with a laser and analyzing the intensity of light emitted when it returns to the unexcited state?
Raman spectroscopy energizes the gas sample with a laser and measures the intensity of the light emitted when it returns to the unexcited state. Infrared monitors work in a manner similar to capnography monitors in that they detect gases based on the amount of infrared light that is absorbed by the sample. Mass spectrometers are typically very expensive and are shared among several operating rooms with samples analyzed and displayed every 1-2 minutes. The spectrometer uses a vacuum to draw a sample of the gas into the machine where it is ionized and passed through a magnetic field. The ions with the highest mass-to-charge ratio are deflected the least. The spectrum of deflection is used to determine the ratio of one gas to another.
Which is more prevalent, RBBB or LBBB? Which is more ominous?
Right bundle branch block (RBBB) is common in the general healthy population without clinical evidence of structural heart disease and has no prognostic significance in this group. RBBB occurs in about 1% of hospitalized patients and is much more common than left bundle branch block (LBBB). LBBB, however, is more ominous—LBBB does not occur in healthy individuals. LBBB is often associated with ischemic heart disease, hypertension, and valvular heart disease. LBBB obscures or simulates other ECG patterns. In the presence of LBBB, the diagnosis of LVH, acute ischemia, or myocardial infarction may be difficult or impossible.
Left bundle branch block (LBBB) and right bundle branch block (RBBB) are both characterized by a heart rate <100 bpm, regular rhythm, normal PR interval, QRS complex > 120 ms (0.12 s), and ST-segment and T waves in the opposite direction of the R wave. What features uniquely identify RBBB?
Right bundle branch block (RBBB) is uniquely characterized by: (1) prominent, notched R waves with "M" pattern (rabbit ears) and rsr', rsR' or rSR' on the right side leads (aVR, V1), and (2) wide S on left side leads.
List five (5) risk factors for vasa previa.
Risk factors for vasa previa are: (1) presence of placenta previa; (2) a low-lying placenta in the second trimester; (3) placental accessory lobes; (4) in vitro fertilization; and, (5) multiple gestations.
Multiple drugs used in the perioperative period can influence the ability to accurately monitor sensory-evoked responses (SER; e.g. somatosensory, visual, and brainstem (auditory) evoked potentials). Compare and contrast the effects of intravenous versus inhalational anesthetics on sensory evoked responses (evoked potentials).
Several general concepts summarize the influence of intravenous and inhalational agents on sensory-evoked responses. (1) Inhalational agents, including nitrous oxide, generally have a more depressant effect on evoked potentials than equipotent doses of intravenous agents. (2) Combinations of drugs generally produce additive effects. (3) Propofol and thiopental attenuate the amplitude of virtually all evoked potential modalities but do not obliterate them. (4) Opioids and benzodiazepines have negligible effects on the recording of all evoked potentials. (5) Ketamine and etomidate have been reported to enhance the quality of signals in patients with weak baseline somatosensory evoked potential (SSEP) signals.
Which two veins combine to form the hepatic portal vein?
The (hepatic) portal vein is formed by the union of the splenic vein and superior mesenteric vein posterior to the neck of the pancreas at the level of L2. The inferior mesenteric vein usually drains into the splenic vein but occasionally (10%) the inferior mesenteric vein joins the splenic and superior mesenteric veins at their confluence at portal vein. Tip: if a question asks for two vessels, the 'best' answer, in our opinion, is splenic and superior mesenteric veins.
The term C50 refers to what?
The C50 represents the site concentration at which a drug exhibits half of its maximal effect. The time it takes for 50% of a drug to be eliminated is referred to as its half-life. The LD50 is half of a drugs lethal dose.
You are evaluating a 5 month old child prior to undergoing general anesthesia for placement of myringotomy tubes. The mother tells you she breastfed the child one hour ago. You should delay the case for how long?
The case should be delayed for three hours as the NPO time for breast milk is 4 hours.
What is a potential side effect of the addition of clonidine to an epidural used for postoperative pain management?
The addition of clonidine to an epidural has been shown to significantly increase the quality and duration of pain relief. As it absorbs into the systemic circulation, it can produce bradycardia, hypotension, and sedation.
You are preparing to performing a high thoracic epidural for postoperative pain control in a patient undergoing general anesthesia for repair of a thoracoabdominal aneurysm. The appropriate landmark for this procedure is the?
The approach for a high thoracic epidural should be made at the C7-T1 interspace. The C7 spinous process is the most prominent and allows for easy determination of the C7-T1 level. A midthoracic approach is typically made using the root of the scapula, which lies at about T3 and the inferior angle of the scapula which lies at about T7.
How is the median nerve blocked?
The nerve distribution shown is that of the median nerve, which can be blocked by the injection of local anesthetic at the wrist between the flexor carpi radialis and the palmaris longus tendons. An injection of local anesthetic both at the wrist between the ulnar artery and flexor carpi ulnaris tendon or at the elbow just lateral to the medial epicondyle of the humerus will anesthetize the ulnar nerve.
Which nerve conduction pathway is most likely to be associated with the autonomic and emotional responses to pain?
The paleospinothalamic tract (medial spinothalamic tract) projects to the medial thalamic nuclei and is associated with autonomic and emotional responses to pain. The spinocervical tract possesses fibers that ascend to the lateral cervical nucleus and then cross to the contralateral thalamus. The spinomesencephalic tract projects to the midbrain reticular formation and may generate nondiscriminatory pain sensations. The neospinothalamic tract ( lateral spinothalamic tract) and sends fibers to the posterior nuclei of the thalamus. It is associated with discriminatory sensations such as location and intensity of pain.
Where in the popliteal fossa can the popliteal artery be found?
The popliteal artery may be found immediately lateral to the semitendinosus tendon.
Which of the following factors is common in all peripheral nerve injuries due to positioning?
The primary mechanisms responsible for peripheral nerve injury are transection, compression, stretch, and kinking, but the component that stems from these mechanisms and is common to all peripheral nerve injuries is ischemia.
What are the main components of a cervical plexus block?
The sensory and motor fibers of the cervical plexus originate from the cervical 2, 3, and 4 nerve roots and are unique in the the sensory fibers separate from the motor fibers early and can be blocked separately. The main potential risk of this procedure is vertebral artery injection, but if the needle is advanced too far medially into the vertebral foramen, epidural or even subarachnoid anesthesia is a potential risk as well, particularly because the the dural sleeves of the cervical nerves are longer on these branches. A cervical plexus block does not protect against the carotid sinus reflex and local injection of the carotid sinus at the point where the carotid artery bifurcates is often necessary.
State the threshold for fibrinogen replacement.
The traditional threshold for fibrinogen replacement is fibrinogen levels less than 80 to 100 mg/dL.
What is the single most sensitive indicator for VAE?
The transesophageal echocardiogram is the most sensitive device for detecting venous air embolism. The doppler is, however, the most sensitive non-invasive device for this purpose. The doppler should be positioned over the right sternal border between the 3rd and 6th intercostal spaces. The injection of mannitol through a central venous line may mimic the signal of a venous air embolism.
The risk associated with the development of CO2 emboli during laparoscopic surgery is potentially increased by what?
The use of nitrous oxide during laparoscopic procedures can potentially increase the risk associated with CO2 emboli by diffusing into small emboli, making them larger and more hazardous.
Name two prostanoids that are potent inhibitors of platelet aggregation and thus promote and maintain an antithrombotic state in vessels?
The vascular endothelium releases prostacyclin (PGI2) and PGD2, along with nitric oxide (NO) and other factors to maintain an anticoagulant state.
If the immune system overreacts to an allergen, a hypersensitivity (allergic) reaction occurs. Immune-mediated hypersensitivity reactions are classified into four groups by mechanism of action: list each type of allergic reaction and give a one sentence description of the reaction.
Type I reactions are anaphylactic or immediate-type hypersensitivity reactions. Type II reactions are cytotoxic reactions (antibody-dependent cell-mediated cytotoxicity). Type III reactions are immune complex reactions that produce tissue damage by deposition of the immune complexes. Type IV reactions are delayed-type hypersensitivity reactions resulting from the interaction of sensitized lymphocytes with specific antigens.
Describe type II hypersensitivity (allergic) reactions: include participating cells and antibody(ies) and list common examples of type II reactions.
Type II cytotoxic reactions are mediated by IgM and IgG antibodies directed against antigens on the surface of foreign cells or extracellular tissue components. The cell damage in type II reactions is produced by (1) direct cell lysis after complete complement cascade activation, (2) increased phagocytosis by macrophages, or (3) killer T-cell lymphocytes producing antibody-dependent cell-mediated cytotoxic effects. Examples of type II reactions ABO-incompatible transfusion reactions, drug-induced immune hemolytic anemia, heparin induced thrombocytopenia (HIT), myasthenia gravis, and Goodpasture's syndrome.
Describe type III allergic (hypersensitivity) reactions: include participating cells and antibody(ies) and list more common examples of type III reactions.
Type III immune complex reactions result from circulating soluble antigens and antibodies that bind to form insoluble complexes which then deposit in the microvasculature. Protracted infections or autoimmune processes can lead to type III reactions. The mechanism of tissue injury is similar to that in type II reactions, involving activation of complement and recruitment of phagocytes. Systemic lupus erythematosus, rheumatoid arthritis, glomerulonephritis, and classic serum sickness are examples of immune complex diseases.
Describe type IV allergic (hypersensitivity) reactions: include participating cells and antibody(ies) and list common examples of type IV reactions.
Type IV delayed-hypersensitivity reactions result from the interactions of sensitized lymphocytes with specific antigens. Delayed hypersensitivity reactions are mainly mononuclear, manifest in 18 to 24 hours, peak at 40 to 80 hours, and disappear in 72 to 96 hours. Cytotoxic T cells are produced specifically to kill target cells that bear antigens identical with those that triggered the reaction. This form of immunity is important in tissue rejection, graft-versus-host reactions, contact dermatitis (e.g., poison ivy), tuberculin immunity, and Johnson-Stevens syndrome. Another form of type IV hypersensitivity is granulomatous hypersensitivity, in which chronic infection leads to the formation of granulomas in tissues. Granulomatous diseases include tuberculosis, sarcoidosis, and Crohn's disease.
Which drug, if administered prior to succinylcholine, will antagonize a depolarizing phase I block? succinylcholine?
Typically, small doses of nondepolarizing muscle relaxants will antagonize a phase I block produced by succinylcholine because by occupying some of the acetylcholine receptors, they inhibit depolarization. Acetylcholinesterase inhibitors such as edrophonium and neostigmine will POTENTIATE the effects of succinylcholine if administered prior.
Define vasa previa.
Vasa previa is defined as the velamentous insertion of the fetal vessels over the cervical os (i.e., the fetal vessels traverse the fetal membranes ahead of the fetal presenting part). Thus, the fetal vessels are not protected by the placenta nor the umbilical cord. (A velamentous cord insertion occurs when the umbilical cord inserts into the fetal membranes instead of into the middle of the placenta.) Rupture of the membranes is often accompanied by tearing of a fetal vessel, which may lead to exsanguination of the fetus. Vasa previa occurs rarely, 1 in 2500 to 1 in 5000 deliveries.
The amniotic sac has ruptured (amniorrhexis) in the parturient and is accompanied by bleeding and fetal heart rate deceleration. What should you suspect? Is this an emergency?
Whenever bleeding occurs with rupture of membranes in the parturient, particularly when accompanied by fetal heart rate deceleration or fetal bradycardia, vasa previa should be suspected. This is a true obstetric emergency as fetal mortality rates are high, ranging from 50% to 75%.
How does furosemide lower BP?
causes prostaglandins to be released from the kidney --> venodilation which reduces preload
