University of Toronto | Clinical Medicine & Advanced Nursing Series
Unit 3: Advanced Hemodynamic Monitoring &
Management of Shock States
Course Context: High-Acuity / Critical Care Clinical Rotation Reference Notes Shock
is fundamentally a state of cellular and tissue hypoxia due to either reduced oxygen
delivery, increased oxygen consumption, or inadequate oxygen utilization. This unit
covers the precise physiological mechanisms, monitoring tools, and critical interventions
required to manage these life-threatening states in an intensive care setting.
1. Pathophysiology and Stages of Shock
Regardless of the etiology, shock progresses through four distinct physiological stages if
left untreated:
● Initial Stage: Cellular-level changes occur. Decreased cardiac output leads to
tissue perfusion insufficiency, forcing cells to switch from aerobic to anaerobic
metabolism. This results in the production of lactic acid. Clinical signs are often
absent or subtle.
● Compensatory Stage: The body attempts to maintain homeostasis. The
sympathetic nervous system (SNS) releases epinephrine and norepinephrine,
increasing heart rate and vasoconstriction to maintain Mean Arterial Pressure
(MAP). The Renin-Angiotensin-Aldosterone System (RAAS) is activated to retain
water and sodium. Clinical presentation: Tachypnea, tachycardia, cool/pale skin
(except in early septic shock), and normal or slightly low blood pressure.
● Progressive Stage: Compensatory mechanisms fail. Tissue perfusion becomes
severely compromised, leading to widespread cellular hypoxia. Cell membranes
fail, lysosomal enzymes leak, and the inflammatory cascade triggers capillary
permeability, resulting in peripheral edema. Clinical presentation: Hypotension,
altered mental status, metabolic acidosis, tachypnea, and early signs of organ
dysfunction (e.g., rising creatinine, elevated liver enzymes).
● Refractory Stage: Total cellular and tissue destruction. Widespread organ failures
are irreversible. Bradycardia, severe hypotension, and profound hypoxemia
culminate in Multiple Organ Dysfunction Syndrome (MODS) and death.
, 2. Comprehensive Matrix of Shock States
Shock Primary Etiology Cardiovascular Key Clinical
Classification Profile Indicators
Hypovolemic Hemorrhage, ↓ CO/CI, ↓ CVP, ↓ Flat neck veins,
severe PCWP, ↑ SVR prolonged capillary
dehydration, third- refill, high urine
spacing, severe specific gravity,
burns. tachycardia.
Cardiogenic Acute MI, severe ↓ CO/CI, ↑ CVP, ↑ Jugular venous
cardiomyopathy, PCWP, ↑ SVR distension (JVD),
valvular failure, pulmonary
dysrhythmias. crackles, S3
gallop,
cool/clammy
extremities.
Septic Dysregulated host Early: ↑ CO/CI, ↓ Hyperthermia/Hyp
(Distributive) response to SVR, ↓ CVP othermia, flushed
systemic infection. warm skin initially,
Late: ↓ CO/CI, ↑ bounding pulses,
SVR tachypnea,
leukocytosis.
Neurogenic Spinal cord injury ↓ CO/CI, ↓ SVR, ↓ Bradycardia
(Distributive) (T6 or above), CVP, ↓ PCWP combined with
spinal anesthesia, hypotension,
severe brain injury. warm/dry/flushed
skin below the
level of injury, loss
of reflex activity.
Unit 3: Advanced Hemodynamic Monitoring &
Management of Shock States
Course Context: High-Acuity / Critical Care Clinical Rotation Reference Notes Shock
is fundamentally a state of cellular and tissue hypoxia due to either reduced oxygen
delivery, increased oxygen consumption, or inadequate oxygen utilization. This unit
covers the precise physiological mechanisms, monitoring tools, and critical interventions
required to manage these life-threatening states in an intensive care setting.
1. Pathophysiology and Stages of Shock
Regardless of the etiology, shock progresses through four distinct physiological stages if
left untreated:
● Initial Stage: Cellular-level changes occur. Decreased cardiac output leads to
tissue perfusion insufficiency, forcing cells to switch from aerobic to anaerobic
metabolism. This results in the production of lactic acid. Clinical signs are often
absent or subtle.
● Compensatory Stage: The body attempts to maintain homeostasis. The
sympathetic nervous system (SNS) releases epinephrine and norepinephrine,
increasing heart rate and vasoconstriction to maintain Mean Arterial Pressure
(MAP). The Renin-Angiotensin-Aldosterone System (RAAS) is activated to retain
water and sodium. Clinical presentation: Tachypnea, tachycardia, cool/pale skin
(except in early septic shock), and normal or slightly low blood pressure.
● Progressive Stage: Compensatory mechanisms fail. Tissue perfusion becomes
severely compromised, leading to widespread cellular hypoxia. Cell membranes
fail, lysosomal enzymes leak, and the inflammatory cascade triggers capillary
permeability, resulting in peripheral edema. Clinical presentation: Hypotension,
altered mental status, metabolic acidosis, tachypnea, and early signs of organ
dysfunction (e.g., rising creatinine, elevated liver enzymes).
● Refractory Stage: Total cellular and tissue destruction. Widespread organ failures
are irreversible. Bradycardia, severe hypotension, and profound hypoxemia
culminate in Multiple Organ Dysfunction Syndrome (MODS) and death.
, 2. Comprehensive Matrix of Shock States
Shock Primary Etiology Cardiovascular Key Clinical
Classification Profile Indicators
Hypovolemic Hemorrhage, ↓ CO/CI, ↓ CVP, ↓ Flat neck veins,
severe PCWP, ↑ SVR prolonged capillary
dehydration, third- refill, high urine
spacing, severe specific gravity,
burns. tachycardia.
Cardiogenic Acute MI, severe ↓ CO/CI, ↑ CVP, ↑ Jugular venous
cardiomyopathy, PCWP, ↑ SVR distension (JVD),
valvular failure, pulmonary
dysrhythmias. crackles, S3
gallop,
cool/clammy
extremities.
Septic Dysregulated host Early: ↑ CO/CI, ↓ Hyperthermia/Hyp
(Distributive) response to SVR, ↓ CVP othermia, flushed
systemic infection. warm skin initially,
Late: ↓ CO/CI, ↑ bounding pulses,
SVR tachypnea,
leukocytosis.
Neurogenic Spinal cord injury ↓ CO/CI, ↓ SVR, ↓ Bradycardia
(Distributive) (T6 or above), CVP, ↓ PCWP combined with
spinal anesthesia, hypotension,
severe brain injury. warm/dry/flushed
skin below the
level of injury, loss
of reflex activity.
