, Chapter 26: Acid–Base Disorders
CHAPTER LIST Chapter 27: Physiology of Blood and
Hemostasis
Chapter 28: Blood Products and Blood
Chapter 1: Basic Principles of Components
Physiology Chapter 29: Procoagulants
Chapter 2: Basic Principles of Chapter 30: Anticoagulants
Pharmacology Chapter 31: Physiology and
Chapter 3: Neurophysiology Management of Massive Transfusion
Chapter 4: Inhaled Anesthetics Chapter 32: Gastrointestinal Physiology
Chapter 5: Intravenous Sedatives and Chapter 33: Metabolism
Hypnotics Chapter 34: Antiemetics
Chapter 6: Pain Physiology Chapter 35: Antacids and
Chapter 7: Opioid Agonists and Gastrointestinal Motility Drugs
Antagonists Chapter 36: Nutrition
Chapter 8: Centrally Acting Nonopioid Chapter 37: Normal Endocrine Function
Analgesics Chapter 38: Drugs that Alter Glucose
Chapter 9: Peripherally Acting Regulation
Analgesics Chapter 39: Drugs for the Treatment of
Chapter 10: Local Anesthetics Hypothyroidism and Hyperthyroidism
Chapter 11: Neuromuscular Physiology Chapter 40: Other Endocrine Drugs
Chapter 12: Neuromuscular-Blocking Chapter 41: Antimicrobials, Antiseptics,
Drugs and Reversal Agents Disinfectants, and Management of
Chapter 13: Neurologically Active Drugs Perioperative Infection
Chapter 14: Circulatory Physiology Chapter 42: Chemotherapeutic Drugs
Chapter 15: Cardiac Physiology Chapter 43: Psychopharmacologic
Chapter 16: Renal Physiology Drugs
Chapter 17: Intravenous Fluids and Chapter 44: Physiology of the Newborn
Electrolytes Chapter 45: Maternal and Fetal
Chapter 18: Sympathomimetic Drugs Physiology and Pharmacology
Chapter 19: Sympatholytics Chapter 46: Physiology and
Chapter 20: Vasodilators Pharmacology of the Elderly
Chapter 21: Antiarrhythmic Drugs Chapter 47: Physiology and
Chapter 22: Diuretics Pharmacology of Resuscitation
Chapter 23: Lipid-Lowering Drugs
Chapter 24: Gas Exchange
Chapter 25: Respiratory Pharmacology
,Chapter 1: Basic Principles of Physiology
Question 1
A trauma patient under general anesthesia develops acute hemorrhage. Mean arterial
pressure begins to fall. Which compensatory response occurs first in an otherwise
healthy adult?
A. Decreased renal sodium excretion
B. Increased sympathetic nervous system activity
C. Increased aldosterone secretion
D. Increased erythropoietin release
Answer: B
Very Deep Rationale:
The fastest compensatory mechanism for acute hypotension is baroreceptor-
mediated sympathetic activation, which occurs within seconds. Hormonal responses
(aldosterone, erythropoietin) take minutes to hours. Renal sodium retention is secondary
and delayed. Under anesthesia, sympathetic tone may be blunted, increasing
hypotension risk.
Key words: Baroreceptors, sympathetic response, hemorrhage, acute hypotension
Question 2
During induction of anesthesia, systemic vascular resistance decreases abruptly. Which
variable is most immediately affected?
A. Cardiac output
B. Mean arterial pressure
,C. Hemoglobin concentration
D. Arterial oxygen content
Answer: B
Very Deep Rationale:
Mean arterial pressure (MAP) is directly proportional to cardiac output × systemic
vascular resistance. A sudden drop in SVR produces an immediate drop in MAP.
Cardiac output may increase reflexively, hemoglobin remains unchanged, and oxygen
content depends primarily on hemoglobin and saturation.
Key words: SVR, MAP, induction hypotension
Question 3
A patient with severe metabolic acidosis is anesthetized and mechanically ventilated.
Which physiologic compensation is lost due to anesthesia?
A. Renal hydrogen ion secretion
B. Increased bicarbonate generation
C. Hyperventilation to lower PaCO₂
D. Cellular buffering
Answer: C
Very Deep Rationale:
Metabolic acidosis is normally compensated by respiratory hyperventilation to reduce
PaCO₂. Anesthesia and mechanical ventilation remove this spontaneous compensatory
response unless deliberately adjusted. Renal and cellular buffering remain intact but act
more slowly.
Key words: Acid–base compensation, respiratory control, anesthesia
Question 4
Which variable best reflects global tissue oxygen delivery?
,A. PaO₂
B. Hemoglobin concentration
C. Cardiac output
D. Oxygen delivery (DO₂)
Answer: D
Very Deep Rationale:
Oxygen delivery (DO₂) integrates cardiac output × arterial oxygen content. PaO₂
alone does not reflect delivery, especially in anemia or low-flow states. Anesthesia
frequently impairs multiple components simultaneously.
Key words: Oxygen delivery, DO₂, perfusion
Question 5
A hypothermic patient under anesthesia develops ventricular arrhythmias. Which
physiologic mechanism contributes most?
A. Increased metabolic rate
B. Slowed myocardial conduction velocity
C. Increased catecholamine sensitivity
D. Enhanced oxygen unloading
Answer: B
Very Deep Rationale:
Hypothermia slows ion channel kinetics, prolonging depolarization and repolarization,
predisposing to arrhythmias. Metabolic rate decreases, catecholamine sensitivity falls,
and oxygen unloading is impaired (left-shifted dissociation curve).
Key words: Hypothermia, cardiac conduction, arrhythmia
Question 6
Which change most directly explains hypotension after spinal anesthesia?
,A. Decreased preload from venodilation
B. Reduced myocardial contractility
C. Increased pulmonary vascular resistance
D. Increased vagal tone only
Answer: A
Very Deep Rationale:
Spinal anesthesia causes sympathetic blockade, leading to venous pooling and
decreased preload. Contractility is usually preserved unless high block affects cardiac
accelerator fibers. Reduced preload is the dominant mechanism.
Key words: Spinal anesthesia, venodilation, preload
Question 7
In acute hypoxia, which variable changes first?
A. Hemoglobin concentration
B. Oxygen saturation
C. PaO₂
D. Oxygen consumption
Answer: C
Very Deep Rationale:
PaO₂ drops immediately when hypoxia occurs. Oxygen saturation follows depending on
hemoglobin dissociation curve characteristics. Hemoglobin concentration and oxygen
consumption change later or not at all.
Key words: Hypoxia, PaO₂, oxygen cascade
Question 8
Why does anemia increase anesthetic risk even with normal PaO₂?
,A. Reduced PaCO₂ buffering
B. Reduced oxygen-carrying capacity
C. Increased shunt fraction
D. Increased alveolar dead space
Answer: B
Very Deep Rationale:
Oxygen delivery depends primarily on hemoglobin-bound oxygen, not dissolved
oxygen. Normal PaO₂ does not compensate for low hemoglobin. Anesthesia reduces
cardiac reserve, magnifying this deficit.
Key words: Anemia, oxygen content, anesthesia risk
Question 9
Which physiologic variable is most tightly regulated under normal conditions?
A. Cardiac output
B. Blood pressure
C. Arterial pH
D. Oxygen consumption
Answer: C
Very Deep Rationale:
Arterial pH is maintained within a narrow range via respiratory and renal mechanisms.
Anesthesia disrupts these controls, making acid–base disorders particularly dangerous.
Key words: Acid–base homeostasis, pH regulation
Question 10
Which factor most strongly shifts the oxyhemoglobin dissociation curve to the right?
A. Hypothermia
B. Alkalosis
, C. Increased PaCO₂
D. Decreased 2,3-DPG
Answer: C
Very Deep Rationale:
Increased PaCO₂ (Bohr effect) promotes oxygen unloading at tissues. Hypothermia and
alkalosis shift the curve left, impairing oxygen delivery—an important anesthetic
concern.
Key words: Oxyhemoglobin dissociation curve, Bohr effect
Question 11
During septic shock, why may blood pressure remain low despite high cardiac output?
A. Myocardial depression
B. Loss of vascular tone
C. Reduced oxygen extraction
D. Increased blood viscosity
Answer: B
Very Deep Rationale:
Sepsis causes profound vasodilation, reducing SVR. Even high cardiac output cannot
maintain MAP when vascular tone is lost. Anesthesia compounds this effect.
Key words: Septic shock, SVR, vasodilation
Question 12
Which organ is most sensitive to reductions in perfusion pressure?
A. Liver
B. Skeletal muscle
C. Brain
D. Skin
CHAPTER LIST Chapter 27: Physiology of Blood and
Hemostasis
Chapter 28: Blood Products and Blood
Chapter 1: Basic Principles of Components
Physiology Chapter 29: Procoagulants
Chapter 2: Basic Principles of Chapter 30: Anticoagulants
Pharmacology Chapter 31: Physiology and
Chapter 3: Neurophysiology Management of Massive Transfusion
Chapter 4: Inhaled Anesthetics Chapter 32: Gastrointestinal Physiology
Chapter 5: Intravenous Sedatives and Chapter 33: Metabolism
Hypnotics Chapter 34: Antiemetics
Chapter 6: Pain Physiology Chapter 35: Antacids and
Chapter 7: Opioid Agonists and Gastrointestinal Motility Drugs
Antagonists Chapter 36: Nutrition
Chapter 8: Centrally Acting Nonopioid Chapter 37: Normal Endocrine Function
Analgesics Chapter 38: Drugs that Alter Glucose
Chapter 9: Peripherally Acting Regulation
Analgesics Chapter 39: Drugs for the Treatment of
Chapter 10: Local Anesthetics Hypothyroidism and Hyperthyroidism
Chapter 11: Neuromuscular Physiology Chapter 40: Other Endocrine Drugs
Chapter 12: Neuromuscular-Blocking Chapter 41: Antimicrobials, Antiseptics,
Drugs and Reversal Agents Disinfectants, and Management of
Chapter 13: Neurologically Active Drugs Perioperative Infection
Chapter 14: Circulatory Physiology Chapter 42: Chemotherapeutic Drugs
Chapter 15: Cardiac Physiology Chapter 43: Psychopharmacologic
Chapter 16: Renal Physiology Drugs
Chapter 17: Intravenous Fluids and Chapter 44: Physiology of the Newborn
Electrolytes Chapter 45: Maternal and Fetal
Chapter 18: Sympathomimetic Drugs Physiology and Pharmacology
Chapter 19: Sympatholytics Chapter 46: Physiology and
Chapter 20: Vasodilators Pharmacology of the Elderly
Chapter 21: Antiarrhythmic Drugs Chapter 47: Physiology and
Chapter 22: Diuretics Pharmacology of Resuscitation
Chapter 23: Lipid-Lowering Drugs
Chapter 24: Gas Exchange
Chapter 25: Respiratory Pharmacology
,Chapter 1: Basic Principles of Physiology
Question 1
A trauma patient under general anesthesia develops acute hemorrhage. Mean arterial
pressure begins to fall. Which compensatory response occurs first in an otherwise
healthy adult?
A. Decreased renal sodium excretion
B. Increased sympathetic nervous system activity
C. Increased aldosterone secretion
D. Increased erythropoietin release
Answer: B
Very Deep Rationale:
The fastest compensatory mechanism for acute hypotension is baroreceptor-
mediated sympathetic activation, which occurs within seconds. Hormonal responses
(aldosterone, erythropoietin) take minutes to hours. Renal sodium retention is secondary
and delayed. Under anesthesia, sympathetic tone may be blunted, increasing
hypotension risk.
Key words: Baroreceptors, sympathetic response, hemorrhage, acute hypotension
Question 2
During induction of anesthesia, systemic vascular resistance decreases abruptly. Which
variable is most immediately affected?
A. Cardiac output
B. Mean arterial pressure
,C. Hemoglobin concentration
D. Arterial oxygen content
Answer: B
Very Deep Rationale:
Mean arterial pressure (MAP) is directly proportional to cardiac output × systemic
vascular resistance. A sudden drop in SVR produces an immediate drop in MAP.
Cardiac output may increase reflexively, hemoglobin remains unchanged, and oxygen
content depends primarily on hemoglobin and saturation.
Key words: SVR, MAP, induction hypotension
Question 3
A patient with severe metabolic acidosis is anesthetized and mechanically ventilated.
Which physiologic compensation is lost due to anesthesia?
A. Renal hydrogen ion secretion
B. Increased bicarbonate generation
C. Hyperventilation to lower PaCO₂
D. Cellular buffering
Answer: C
Very Deep Rationale:
Metabolic acidosis is normally compensated by respiratory hyperventilation to reduce
PaCO₂. Anesthesia and mechanical ventilation remove this spontaneous compensatory
response unless deliberately adjusted. Renal and cellular buffering remain intact but act
more slowly.
Key words: Acid–base compensation, respiratory control, anesthesia
Question 4
Which variable best reflects global tissue oxygen delivery?
,A. PaO₂
B. Hemoglobin concentration
C. Cardiac output
D. Oxygen delivery (DO₂)
Answer: D
Very Deep Rationale:
Oxygen delivery (DO₂) integrates cardiac output × arterial oxygen content. PaO₂
alone does not reflect delivery, especially in anemia or low-flow states. Anesthesia
frequently impairs multiple components simultaneously.
Key words: Oxygen delivery, DO₂, perfusion
Question 5
A hypothermic patient under anesthesia develops ventricular arrhythmias. Which
physiologic mechanism contributes most?
A. Increased metabolic rate
B. Slowed myocardial conduction velocity
C. Increased catecholamine sensitivity
D. Enhanced oxygen unloading
Answer: B
Very Deep Rationale:
Hypothermia slows ion channel kinetics, prolonging depolarization and repolarization,
predisposing to arrhythmias. Metabolic rate decreases, catecholamine sensitivity falls,
and oxygen unloading is impaired (left-shifted dissociation curve).
Key words: Hypothermia, cardiac conduction, arrhythmia
Question 6
Which change most directly explains hypotension after spinal anesthesia?
,A. Decreased preload from venodilation
B. Reduced myocardial contractility
C. Increased pulmonary vascular resistance
D. Increased vagal tone only
Answer: A
Very Deep Rationale:
Spinal anesthesia causes sympathetic blockade, leading to venous pooling and
decreased preload. Contractility is usually preserved unless high block affects cardiac
accelerator fibers. Reduced preload is the dominant mechanism.
Key words: Spinal anesthesia, venodilation, preload
Question 7
In acute hypoxia, which variable changes first?
A. Hemoglobin concentration
B. Oxygen saturation
C. PaO₂
D. Oxygen consumption
Answer: C
Very Deep Rationale:
PaO₂ drops immediately when hypoxia occurs. Oxygen saturation follows depending on
hemoglobin dissociation curve characteristics. Hemoglobin concentration and oxygen
consumption change later or not at all.
Key words: Hypoxia, PaO₂, oxygen cascade
Question 8
Why does anemia increase anesthetic risk even with normal PaO₂?
,A. Reduced PaCO₂ buffering
B. Reduced oxygen-carrying capacity
C. Increased shunt fraction
D. Increased alveolar dead space
Answer: B
Very Deep Rationale:
Oxygen delivery depends primarily on hemoglobin-bound oxygen, not dissolved
oxygen. Normal PaO₂ does not compensate for low hemoglobin. Anesthesia reduces
cardiac reserve, magnifying this deficit.
Key words: Anemia, oxygen content, anesthesia risk
Question 9
Which physiologic variable is most tightly regulated under normal conditions?
A. Cardiac output
B. Blood pressure
C. Arterial pH
D. Oxygen consumption
Answer: C
Very Deep Rationale:
Arterial pH is maintained within a narrow range via respiratory and renal mechanisms.
Anesthesia disrupts these controls, making acid–base disorders particularly dangerous.
Key words: Acid–base homeostasis, pH regulation
Question 10
Which factor most strongly shifts the oxyhemoglobin dissociation curve to the right?
A. Hypothermia
B. Alkalosis
, C. Increased PaCO₂
D. Decreased 2,3-DPG
Answer: C
Very Deep Rationale:
Increased PaCO₂ (Bohr effect) promotes oxygen unloading at tissues. Hypothermia and
alkalosis shift the curve left, impairing oxygen delivery—an important anesthetic
concern.
Key words: Oxyhemoglobin dissociation curve, Bohr effect
Question 11
During septic shock, why may blood pressure remain low despite high cardiac output?
A. Myocardial depression
B. Loss of vascular tone
C. Reduced oxygen extraction
D. Increased blood viscosity
Answer: B
Very Deep Rationale:
Sepsis causes profound vasodilation, reducing SVR. Even high cardiac output cannot
maintain MAP when vascular tone is lost. Anesthesia compounds this effect.
Key words: Septic shock, SVR, vasodilation
Question 12
Which organ is most sensitive to reductions in perfusion pressure?
A. Liver
B. Skeletal muscle
C. Brain
D. Skin
