Physiology 1

Question 1

Which of the following would result in INCREASED oxygen delivery to the tissues?

Answer 1

Oxygen delivery is dependent on cardiac output and arterial oxygen content, but is also affected by factors influencing the P50, the partial pressure of oxygen at which hemoglobin is 50% saturated. A left-shift in the oxygen-hemoglobin desaturation curve results in increased oxygen affinity and decreased oxygen delivery, whereas a right-shift results in decreased oxygen affinity and increased oxygen delivery to tissues.

Question 2

Which of following MOST likely occurs in the brain after prolonged fasting?

Answer 2

During prolonged fasting the brain uses ketone bodies as an alternate source of energy. The other organs use fatty acids.

TrueLearn Insight : Fasting Period
10-12 hours: Decrease insulin; stimulate glucagon; increase fatty acid oxidation for energy
2-3 days: Increase in ketone bodies for brain to use as alternate energy
3 weeks: Protein breakdown/amino acid utilization for energy

Question 3

Which of the following factors is MOST LIKELY responsible for the release of arginine vasopressin?

Answer 3

AVP is the main physiologic factor in water resorption. It is released from the pituitary in response to hyperosmolality, reduced effective circulating volume, angiotensin II, stress, pain, nausea, hypoglycemia, pregnancy, and certain drugs.

Question 4

Which of the following occurs during ventricular diastole?

Answer 4

The cardiac cycle, discussed mainly from the standpoint of the ventricles, consists of diastole and systole. Ventricular diastole starts with isovolumetric relaxation following by rapid filling, diastasis (slow filling), and atrial systole. Ventricular systole starts with isovolumetric contraction followed by ejection of the blood from the ventricles.

Question 5

Which of the following hormones is cleaved intravascularly during passage through the pulmonary circulation?

Answer 5

Angiotensin I is converted to AII by intravascular ACE in the pulmonary circulation. Circulating norepinephrine is inactivated and degraded within pulmonary endothelium.

Question 6

Which of the following statements about adult brain metabolism is TRUE?

Answer 6

Under normal circumstances, the brain exclusively utilizes glucose for energy. During periods of fasting, exercise, or starvation, the brain also uses ketone bodies for energy.

Question 7

An alteration of which of the following parameters MOST significantly stimulates the carotid body chemoreceptors?

Answer 7

The carotid body chemoreceptors are located at the bifurcation of the common carotid arteries bilaterally. The chemoreceptors are stimulated to increase minute ventilation in response to decreases in PaO2 below 60-65 mm Hg.

Question 8

Which of the following will INCREASE pulmonary vasoconstriction?

Answer 8

Hypercapnia, hypoxia, and acidosis all contribute to pulmonary vasoconstriction. Inhaled nitric oxide is a selective pulmonary vasodilator that can be used to treat severe pulmonary hypertension.

Question 9

Carbon dioxide is primarily transported in blood in which of the following three forms?

Answer 9

Carbon dioxide is transported in the blood as dissolved CO2, bicarbonate, and carbamino compounds.

Question 10

Which option below would cause a DECREASE in a patient’s mixed venous oxygen saturation (SvO2)?

Answer 10

The Fick equation states: SvO2 = SaO2 – [VO2 ÷ (CO x Hgb x 1.36)]
Based on the Fick equation, SvO2 is DECREASED in the following settings:
- Increased oxygen consumption (e.g. hyperthermia, shivering, or pain)
- Decreased cardiac output (e.g. myocardial infarction or hypovolemia)
- Decreased hemoglobin concentration
- Decreased arterial oxygen saturation

Mixed venous oxygen saturation levels are INCREASED in the following settings:
- Increasing the hemoglobin concentration via blood transfusions
- Increased SaO2
- Decreased VO2 (e.g. cyanide toxicity, sepsis, carbon monoxide poisoning, methemoglobinemia, hypothermia)
- Increased CO (e.g. sepsis)
A left to right intracardiac shunt, in addition to increasing cardiac output, also shifts oxygenated blood from the left side of the heart to mix with deoxygenated blood on the right side, thereby falsely elevating the SvO2.

Question 11

A 68-year-old alcoholic male comes in for emergent evacuation of subdural hematoma after a fall while intoxicated 1 hour ago. He is agitated, not following commands, and icteric on exam. The family states he has a history of cirrhosis and is noncompliant with medication therapy. He has no other medical history and is not taking any other medications. Which of the following is MOST likely true regarding his liver disease?

Answer 11

Synthetic liver function is best assessed via the PT/INR, which most closely correlates with factor VIIa levels.

Question 12

A 60-year-old male is scheduled to undergo laparoscopic cholecystectomy. The patient has a history of type I diabetes mellitus complicated by gastroparesis and peripheral neuropathy. Which of the following is TRUE?

Answer 12

Metoclopramide is a dopamine antagonist that increases lower esophageal sphincter tone, enhances gastric emptying in patients who have slowed gastric emptying, and decreases gastric fluid volume. Unfortunately, its antiemetic properties are weak.

Question 13

Which lung volume/capacity is defined as the amount of air in a patient’s lungs at end of exhalation during a normal volume breath, when air movement stops?

Answer 13

FRC is the volume of gas left in the lungs at the end of a tidal volume breath. FRC is essential to the effectiveness of preoxygenation.

TrueLearn Insight : Causes of low FRC are PANGOS: Pregnancy, Ascites, Neonates, General anesthesia, Obesity, Supine position.
Factors that increase closing capacity are ACLS-SO: Age, Chronic bronchitis, LV failure, Smoking, Surgery, Obesity.

Question 14

Which of the following describes the volume of gas remaining in the lungs at passive end expiration?

Answer 14

Functional residual capacity is the volume of gas remaining in the lungs at passive end expiration. Furthermore, FRC is the primary determinant of oxygen reserve in humans when apnea occurs.

Question 15

Which of the following is NOT a true statement regarding anesthetic uptake and blood:gas solubility?
(FA= fractional concentration of alveolar anesthetic, FI= fractional concentration of inspired anesthetic)

Answer 15

Volatile anesthetic uptake is proportional to blood:gas solubility, whereby those agents with higher blood:gas partition coefficients have a slower rate of rise of FA/FI as compared to less soluble agents. Volatile agent blood:gas solubility in order of least to greatest is: Desflurane < N2O < Sevoflurane < Isoflurane.

Question 16

A patient presents to the emergency department with an acute ischemic stroke. An angiogram shows occlusion of the left anterior cerebral artery. What is the most likely presenting symptom?

Answer 16

Anterior cerebral artery strokes tend to lead to behavioral abnormalities, aphasia (if dominant cortex is involved), and contralateral lower limb weakness and sensory deficits.

Question 17

Which of the following decreases the affinity of hemoglobin for oxygen?

Answer 17

Factors that decrease hemoglobin’s affinity for oxygen and therefore increase oxygen unloading to tissues include hyperthermia, acidosis, hypercarbia, and increased 2,3-BPG.

TrueLearn Insight : The Haldane effect describes the relationship between the content of carbon dioxide in the blood and the concentration of oxyhemoglobin. A mnemonic to help remember what shifts the curve to the right is: “CADET, face Right!” for CO2, Acid, 2,3-DPG, Exercise, and Temperature.

Question 18

Which of the following explains the relationship between the carbon dioxide dissociation curve in blood and oxyhemoglobin?

Answer 18

The Haldane effect illustrates that the oxygenation of hemoglobin lowers the affinity of hemoglobin for carbon dioxide.

Question 19

A 54-year-old male presents to the emergency department with a lower gastrointestinal bleed. The patient’s blood pressure is 82/51 mm Hg. What is the mechanism of action for renin in this patient?

Answer 19

A decrease in blood pressure stimulates the release of renin into the serum from the renal tubules. Renin converts angiotensinogen to angiotensin I, which is then converted to angiotensin II by ACE. Angiotensin II causes an increase in blood pressure by direct vasoconstriction, enhancing the sympathetic nervous system, and causing an increase of aldosterone.

Question 20

Which of the following is the single best choice in providing an assessment of hepatic protein synthesis?

Answer 20

Hepatic protein synthesis is best assessed by measuring coagulation factors.

Question 21

In a healthy young adult, plasma volume comprises approximately what percentage of extracellular volume?

Answer 21

The ECV contains one-third of TBW, represents 20% of total body weight and is composed of plasma volume (20-25%) and interstitial fluid volume (75-80%).

Question 22

Which of the following is the primary determinant of myocardial oxygen consumption?

Answer 22

Heart rate is the primary determinant of myocardial oxygen consumption. The heart maximally extracts arterial oxygen and therefore relies on increased oxygen delivery via metabolically mediated vasodilation, coronary autoregulation, and reactive hyperemia.

Question 23

Which of the following points represents INCREASED lusitropy on the left ventricular pressure-volume loop below?

Answer 23

Pressure-volume loops can be used to illustrate changes in cardiac work as a result of various changes to ventricular pressure as a function of the ventricular volume. Positive lusitropy is depicted by a rightward and downward shift of diastolic filling, which illustrates a compliant ventricle that is able to accommodate a larger volume at a decreased ventricular pressure.

Question 24

Which of the following phases contributes the LARGEST volume of blood to the left ventricle during diastole?

Answer 24

Early rapid filling contributes the largest volume of blood during diastole. The phases of diastole are: isovolumetric relaxation, early rapid filling, diastasis, and atrial contraction.

TrueLearn Insight : Atrial contraction normally contributes approximately 15% of the preload. In patients with poor left ventricular filling, as in diastolic dysfunction, the atrial contraction becomes very important.

Question 25

Which of the following variables will result in an INCREASED functional residual capacity?

Answer 25

Functional residual capacity increases with age due to loss of elastic lung tissue which acts as an inward force pulling the lungs closed. An increase will also be seen with increased height secondary to the larger lungs compared to short counterparts. TrueLearn Insight : Other causes of low FRC are PANGOS: Pregnancy, Ascites, Neonatal, General anesthesia, Obesity, Supine position.

Question 26

Which of the following is the main goal of preoxygenation prior to induction?

Answer 26

Denitrogenation of the FRC allows a greater apneic oxygenation time during induction of anesthesia.

Question 27

Which of the following drugs used to treat hyperkalemia has the SLOWEST onset of action?

Answer 27

The mainstays of treatment for hyperkalemia include calcium chloride to stabilize the myocardium, insulin +/- dextrose to temporarily shift potassium intracellularly, and elimination of potassium via diuresis (usually loop diuretics such as furosemide), gastrointestinal loss (via the potassium binders patiromer or sodium zirconium cyclosilicate), or removal via hemodialysis. Intravenous insulin is the most rapid way to lower serum potassium, but this must be followed up by a method of eliminating the potassium, such as with furosemide, as the effects of insulin are only temporary.

Question 28

Which of the following does NOT have an effect on left ventricular myocardial oxygen supply?

Answer 28

Myocardial oxygen supply is affected by AoDP, LVEDP, heart rate, Hgb, and CVR. Left ventricular systolic pressure affects myocardial oxygen demand.

Question 29

Which of the following does NOT contribute to the termination of an action potential in a neuron?

Answer 29

A neuron action potential is terminated by membrane repolarization caused by the inactivation and then closing of voltage-dependent sodium channels and the opening of potassium channels that promote potassium efflux. TrueLearn Insight: Local anesthetics block nerve impulse transmission by reversibly binding to the intracellular portion of the voltage-gated sodium channels and thereby preventing sodium ion influx.

Question 30

Which of the following requires the highest concentration of isoflurane to prevent movement (MAC50) to that stimulus?

Answer 30

The minimum alveolar concentration (MAC) is the alveolar concentration of an anesthetic that prevents movement in response to surgical stimulation in 50% of patients. Endotracheal intubation requires the highest concentration of volatile anesthetic to prevent movement.

Question 31

Which of the following is NOT an effect or complication of sodium bicarbonate administration?

Answer 31

Sodium bicarbonate can cause a number of physiologic alterations including increased preload, decreased left ventricular contractility, and increased hemoglobin affinity for oxygen. Sodium bicarbonate administration is also associated with intracranial hemorrhage, especially with rapid administration in infants, and increased lactate production.

Question 32

Which of the following would INCREASE minimum alveolar concentration (MAC) requirements for an adult patient?

Answer 32

``` Factors Increasing MAC: Drug - Amphetamine (acute use) - Cocaine - Ephedrine - Ethanol (chronic use) Age - Highest at age 6 months Electrolyte disturbance - Hypernatremia Hyperthermia Red hair ``` ``` Factors Decreasing MAC: Drugs - Propofol, etomidate, barbiturates, benzodiazepines, ketamine - Alpha2 agonists (clonidine, dexmedetomidine) - Ethanol (acute use) - Local anesthetics - Opioids - Amphetamines (chronic use) - Lithium - Verapamil Age - Elderly patients Electrolyte disturbance - Hyponatremia Others - Anemia (Hgb < 5 g/dL) - Hypercarbia - Hypothermia - Hypoxia Pregnancy ```

Question 33

Which of the following statements BEST describes cardiac perfusion?

Answer 33

Coronary blood flow is dependent on the gradient between aortic and ventricular pressures. The RCA and LCA maintain different blood flows throughout the cardiac cycle because of the differences between RV and LV pressures. The RV is continuously perfused throughout the cardiac cycle whereas the LV is primarily perfused during ventricular diastole.

Question 34

Which of the following BEST describes the mechanism of action of cytochrome p450?

Answer 34

Cytochrome p450 is involved in phase I metabolism by oxidizing many drugs. TrueLearn Insight : Chronic barbiturate use increases cytochrome p450 activity. As a result, the metabolism of drugs by p450 is increased (as seen with benzodiazepines).

Question 35

Which of the following substances does NOT have any metabolism by pulmonary tissues?

Answer 35

The lungs have multiple other functions besides gas exchange. Because the lung constitutes a huge interface between the outside environment and the body, it acts as a defense system. Additionally, the lungs are metabolic and play a large role in activating and inactivating a variety of substances. Adrenaline (epinephrine), isoprenaline (isoproterenol), and dopamine undergo no metabolism in the lungs.

Question 36

Which of the following statements about minimum alveolar concentration values is CORRECT?

Answer 36

MAC-awake < MAC < MAC-BAR.

Question 37

Which of the following increases minimum alveolar concentration of inhaled anesthetics?

Answer 37

Hyperthermia, hypernatremia, chronic ethanol abuse, and increased central neurotransmitter levels (e.g. MAOIs, amphetamine, cocaine, ephedrine, and levodopa use) increase MAC requirements for anesthetic agents.

Question 38

Which of the following left-ventricular mechanical events corresponds with the electrical R wave on ECG?

Answer 38

The closing of the mitral valve corresponds with the electrical R wave of the QRS complex.

Question 39

Which of the following causes a right shift in the oxyhemoglobin dissociation curve?

Answer 39

Hypercarbia, acidosis, hyperthermia, and high 2,3-DPG levels, all shift the oxygen-hemoglobin dissociation curve to the right and increase oxygen unloading to tissues. TrueLearn Insight : Red cell 2, 3-DPG in stored blood diminishes in storage and is effectively zero after 1-2 weeks (rate of decline depends on types of preservative used). After transfusion, red cell 2, 3-DPG returns to 50% after 7 hours and to normal level after 48 hours.

Question 40

Stimulation of which of the following is MOST likely to cause bronchoconstriction?

Answer 40

Bronchoconstriction occurs mainly due to the parasympathetic nervous system via the vagus nerve.

Question 41

A 70-year-old 80 kg male undergoes exploratory laparotomy for a perforated duodenum and is now in the ICU intubated on a FiO2 of 50%, PEEP of 5 cmH2O, respiratory rate of 20 breaths per minute, and tidal volume of 480 milliliters. His SpO2 is 80%, blood pressure is 100/50 mm Hg, pulse is 80 beats per minute, and temperature is 37.2 degrees Celsius. An arterial blood gas is drawn with the following results: pH: 7.30 PaO2: 55 mm Hg PaCO2: 52 mm Hg HCO3: 18 mEq/L A chest radiograph shows bilateral fluffy infiltrates. A pulmonary artery catheter is inserted with a pulmonary capillary wedge pressure of 10 mm Hg. Which of the following interventions is LEAST LIKELY to improve the patient's PaO2?

Answer 41

Oxygen therapy is of limited value with large intrapulmonary shunts due to limitation of gas exchange and requires alternative therapies to improve V/Q matching.

Question 42

A 21-year-old female at 32 weeks gestation requires general anesthesia for fixation of a femur fracture. Sodium citrate/citric acid 30 mL is given prior to induction of anesthesia. Induction is performed with propofol 2 mg/kg and rocuronium 1.2 mg/kg followed by rapid sequence intubation. At the end of the procedure, muscle relaxant antagonism is planned with neostigmine. Which of the following anticholinergics would be the MOST appropriate to administer with neostigmine if fetal bradycardia is a concern?

Answer 42

Atropine is a tertiary amine, which more easily crosses the placenta than does glycopyrrolate, a quaternary amine. Therefore atropine should be given in conjunction with neostigmine for reversal of pregnant patients to avoid fetal bradycardia. TrueLearn Insight : In extreme hemodynamic instability, such as multi-system trauma with refractory shock, scopolamine 5 mcg/kg IV (0.2-0.4 mg for an adult) is an option to provide amnesia. It is worth noting that this may interfere with subsequent neurologic examinations because of its long half-life.

Question 43

Oxygen unloading is decreased in which of the following scenarios?

Answer 43

Hyperthermia, acidosis, high pCO2, and high levels of 2,3-DPG cause a shift to the right. Fetal hemoglobin shifts the curve to the left.

Question 44

An obese 50-year-old male is undergoing laparoscopic gastric bypass surgery. To improve surgical visualization, the surgeon asks for steep Trendelenburg positioning. After this change, you note the following changes over a 20 minute period: ``` Before After SpO2 98% 90% ETCO2 32 mm Hg 41 mmHg PIP 25 cmH2O 32 cmH2O MAP 68 mmHg 74 mmHg ``` His blood pressure cuff is on the upper arm and the ventilator remains in pressure control mode. What is the most likely cause of his hypoxemia?

Answer 44

Laparoscopic insufflation causes a decrease in tidal volumes when using pressure-control ventilation. Hypoxemia can be due to atelectasis and decreased diaphragmatic excursion. TrueLearn Insight : During laparoscopic procedures it is best to use either volume-control or pressure-control volume-guaranteed modes of ventilation. Pressure control alone can assist with achieving appropriate tidal volumes, but at the risk of over-ventilation with position changes and desufflation.