S&P Lecture 5: Shock and Sepsis

What is shock, at its most basic definition?

Failure to meet the metabolic needs of the cell, and the consequences that follow

Shock is widespread cellular metabolic dysfunction or injury resulting from what two processes?

Hypoperfusion and/or severe inflammation

What happens at the cellular level when tissue perfusion/oxygen delivery is reduced in shock?

Cellular hypoxia → ion pump dysfunction, intracellular edema, leakage of intracellular contents, and poor pH regulation

What are the four main types of shock? (select all that apply)

1. Hypovolemic 2. Cardiogenic 3. Obstructive 4. Distributive

What are the three subtypes of distributive shock? (select all that apply)

1. Septic 2. Neurogenic 3. Anaphylactic

Which types of shock are most common in the surgical patient due to HYPOPERFUSION? (select all that apply)

1. Hypovolemia 2. Cardiogenic

Which types of shock are most common in the surgical patient due to SEVERE INFLAMMATION? (select all that apply)

1. Sepsis 2. SIRS 3. Anaphylaxis

What are the five common causes of shock? (select all that apply)

1. Depletion of intravascular volume 2. Compression of the heart or great vessels 3. Intrinsic failure of the heart 4. Loss of autonomic control of the vasculature 5. Severe untreated systemic inflammation

What is the most common cause of hypovolemic shock?

Bleeding

Besides bleeding, what are other causes of hypovolemic shock? (select all that apply)

1. Diarrhea 2. Vomiting 3. Fluid sequestered in gut (obstruction) 4. Redistribution of fluids (burn - 3rd spacing)

What is the basic pathophysiology of hypovolemic shock?

Reduced intravascular volume → less ventricular filling → reduced cardiac output

What are the signs/symptoms of hypovolemic shock? (select all that apply)

1. Tachycardia 2. Tachypnea 3. Hypotension 4. Hypoperfusion

What is often the most sensitive and earliest sign of hypoperfusion in hypovolemic shock?

Decreased blood flow to the skin - delayed capillary refill

What defines ABSOLUTE hypotension?

SBP < 90 or MAP < 65

What defines RELATIVE hypotension?

A drop of > 40 mmHg from baseline

How is MAP calculated?

MAP = 1/3(SBP) + 2/3(DBP) [i.e., (SBP+ 2DBP) ÷ 3]

What is a normal MAP range per the lecture?

70-110 mmHg

How much volume is in 1 unit of PRBCs?

~350 mL

Hemorrhagic shock Class I: blood loss, HR, BP, pulse pressure, RR, mental status?

<750 mL (<15%); HR <100; normal BP; normal pulse pressure; RR 14-20; slightly anxious

Hemorrhagic shock Class II: blood loss, HR, BP, pulse pressure, RR, mental status?

750-1500 mL (15-30%); HR 100-120; normal BP; narrowed pulse pressure; RR 20-30; mildly anxious

Hemorrhagic shock Class III: blood loss, HR, BP, pulse pressure, RR, mental status?

1500-2000 mL (30-40%); HR 120-140; decreased BP; narrowed pulse pressure; RR 30-40; anxious, confused

Hemorrhagic shock Class IV: blood loss, HR, BP, pulse pressure, RR, mental status?

> 2000 mL (> 40%); HR > 140; decreased BP; narrowed pulse pressure; RR > 35; confused, lethargic

At what class of hemorrhagic shock does blood pressure first DECREASE?

Class III (1500-2000 mL, 30-40% blood loss)

What is pulse pressure?

The difference between systolic and diastolic blood pressure (SBP - DBP)

What does a NARROW/reduced pulse pressure indicate, and in which shock types is it seen?

Low stroke volume and vasoconstriction - most types of shock

What does a WIDE/increased pulse pressure indicate, and in which shock type is it seen?

High stroke volume and vasodilation - distributive shock

How does cardiac output change over time in hypovolemic shock?

Initially increased, then starts dropping over time

What is cardiogenic shock?

Inadequate perfusion from diminished cardiac output - pump failure

What are the hemodynamic findings in cardiogenic shock? (select all that apply)

1. Hypotension 2. Tachycardia 3. Decreased CO 4. Increased SVR

What is the formula for systemic vascular resistance (SVR)?

SVR = (MAP - CVP) ÷ CO - resistance to blood flow by the systemic vasculature (excluding pulmonary)

What are common causes of cardiogenic shock? (select all that apply)

1. AMI 2. End-stage cardiomyopathy 3. Advanced valvular heart disease 4. Myocarditis 5. Arrhythmias

Which arrhythmias can cause cardiogenic shock? (select all that apply)

1. AFib 2. SVT 3. VTach 4. Heart block 5. AFlutter

What is the management of cardiogenic shock? (select all that apply)

1. Inotropic support (dobutamine) 2. Vasopressor (norepinephrine) 3. Revascularization 4. Mechanical circulatory support (MCS)

What are the common causes of obstructive shock? (select all that apply)

1. PE 2. Tension pneumothorax 3. Tamponade

What is the mechanism of obstructive shock, and what is the treatment approach?

Hypoperfusion due to elevated resistance - treatment is immediate intervention

In distributive shock, where does the deficit lie?

In the periphery - decreased SVR and altered oxygen extraction

What is cardiac output typically in distributive shock?

High

What is septic shock (in terms of perfusion)?

Inadequate perfusion from redistribution of blood volume due to sepsis (severe inflammation from infection)

What are the hemodynamic findings of septic shock? (select all that apply)

1. Increased CO 2. Tachycardia 3. Decreased SVR 4. Relative hypovolemia

Why is there 'relative' hypovolemia in septic shock?

Volume is not leaving the body - it is redistributed in the vasculature (periphery, 3rd spacing, capillary permeability)

How many organ systems must be involved to diagnose anaphylactic shock?

Two

What organ system findings can be seen in anaphylactic shock? (select all that apply)

1. Airway compromise 2. Rash 3. GI symptoms 4. Respiratory symptoms

What causes neurogenic shock?

Loss of vasomotor tone → peripheral vasodilation

Which vital sign finding distinguishes neurogenic shock from other types of shock?

Bradycardia (blunted response) - other shock types are tachycardic

What findings are seen in neurogenic shock? (select all that apply)

1. Hypotension 2. Bradycardia 3. Decreased SVR 4. Relative hypovolemia

What does the VIP approach to shock stand for?

Ventilate, Infuse, Pump

What is the 'Ventilate' step of the VIP approach?

Supplement O2 early to prevent/improve hypoxia

What is the 'Infuse' step of the VIP approach, and what is the main caution?

Fluid resuscitation with crystalloid - avoid over-infusing, which can lead to serious consequences

What is the first-line vasopressor in shock?

Norepinephrine (α + β activity)

Which inotrope is used in shock and what does it do?

Dobutamine - increases cardiac output

When are vasodilators (nitrates) used in shock, and what is the risk?

Not often - only when afterload needs to be reduced; may reduce BP

Case: 47M POD #2 hemicolectomy, BP 88/40, HR 122, new confusion, firm tender abdomen. What type of shock is most likely?

Hypovolemic (hemorrhagic) shock - postop bleeding

Case: 47M POD #2 hemicolectomy, BP 88/40, HR 122, new confusion, firm tender abdomen. What are the initial steps? (select all that apply)

1. Airway 2. Large-bore IV access and IV fluids (1 L crystalloid) 3. CBC, CMP 4. CT abd/pelvis 5. Transfuse 6. ICU 7. Likely ex-lap

What is the role of INFLAMMATION in shock?

Pathogens or cellular injury → cytokine cascade/inflammatory mediators → vascular permeability, vasodilation, leukocyte recruitment

In which shock states is hypoperfusion found?

All shock states - it is part of the definition of shock

What are the signs/symptoms of hypoperfusion? (select all that apply)

1. Cold, clammy skin 2. Oliguria 3. AMS 4. Hyperlactatemia

Why can't shock be treated with vasopressors alone?

You must find the root cause and fix it

A trauma patient may have more than one cause of shock - give the example from lecture.

Hypovolemia from blood loss AND neurogenic shock from spinal cord injury

What is ISCHEMIA in shock?

The result of prolonged hypoperfusion - shift from aerobic to anaerobic metabolism → lactic acidosis

What is the primary goal of resuscitation in shock?

Not only to restore BP but to provide adequate cellular metabolism - correcting hypotension is a prerequisite

What is the starred MAP goal during resuscitation?

MAP 65-70

What are the early resuscitation endpoints listed in lecture? (select all that apply)

1. Radial pulse 2. SBP 80 3. MAP 65-70 4. Bleeding controlled

What are the later resuscitation endpoints (restoration of organ perfusion)? (select all that apply)

1. Normal CO 2. Normal organ function 3. Tissue acidosis resolved 4. Restoration of tissue perfusion

What are the consequences of excessive IV crystalloid fluids?

Edema, 3rd spacing, CHF

Where should an actively bleeding patient be stabilized?

In the operating room - any delay to the OR for hemorrhage control increases mortality

What does lactate measure in shock?

It is an INDIRECT measurement of oxygen debt - approximates the magnitude of shock

What does a persistently elevated lactate suggest?

Ineffective resuscitation / ongoing hypoperfusion

What is base deficit?

The amount of base required to titrate blood to a normal pH - surrogate for severity of metabolic acidosis and O2 debt

What does a more negative base deficit indicate?

Greater tissue hypoperfusion

In what setting is base deficit most useful, and what does continued elevation mean?

Trauma with hemorrhagic shock - continued elevation likely = ongoing bleeding

What mortality was associated with a base deficit > 15 mmol/L in trauma patients?

70%

When does increasing RVEDVI help, and what is the risk?

RVEDVI predicts preload - increasing it only helps if the pt is preload (fluid) responsive; too much fluid can be deleterious

What test is used to assess fluid responsiveness?

Passive leg raise → look for an increase in SV or CO (measured with ECHO, pulse pressure change, or invasive monitor)

How well do physical exam findings (dry MM, cap refill, tachycardia, low JVP) and CVP predict fluid responsiveness?

Poorly - all performed poorly; even CVP was unreliable

What are the monitoring methods used in shock? (select all that apply)

1. Central line 2. Arterial line 3. Swan-Ganz catheter 4. Intra-abdominal (bladder) pressure 5. UOP 6. Mental status 7. POCUS / IVC collapsibility 8. Pulse pressure & stroke volume variation 9. Lactate & base deficit 10. FloTrac/Vigileo

On FloTrac/Vigileo, what does a higher stroke volume variation (SVV) mean?

The patient is fluid responsive

What shock types have a HIGH SVR?

Cardiogenic and hypovolemic shock

What shock type has a LOW SVR?

Distributive shock

What is SvO2 and its normal range?

Concentration of oxygen in blood returning to the heart - normal 60-80

What causes a low SvO2? (select all that apply)

1. Decreased CO 2. Anemia/blood loss 3. Hypoxemia 4. Increased metabolic demand

What are the five hypoperfusion states covered in lecture? (select all that apply)

1. Hypovolemia 2. Pericardial tamponade 3. Tension pneumothorax 4. Increased intra-abdominal pressure 5. Cardiogenic shock

Hypovolemia in the post-surgical patient: what is the starred etiology and starred management?

Etiology: bleeding. Management: find and stop the bleeding

What is the management of hypovolemia? (select all that apply)

1. Find and stop bleeding 2. Replace products 3. IVF 4. Ventilation support

How is hypovolemia diagnosed? (select all that apply)

1. BP, HR, fluid response, lactate 2. End-organ hypoperfusion - oliguria, AMS, cool extremities

What is the etiology of pericardial tamponade?

Accumulation of blood in the pericardial sac - trauma or chronic conditions

How is pericardial tamponade diagnosed? (select all that apply)

1. BP, HR, CO 2. ECHO/POCUS 3. CT/CXR 4. Clinical exam (starred)

What is the management of pericardial tamponade? (select all that apply)

1. Pericardiocentesis 2. Pericardial window 3. Determine underlying cause if not trauma

What is the mechanism of tension pneumothorax?

One-way valve in the chest wall - air in but not out (usually trauma: stab, fall)

What are the clinical exam findings of tension pneumothorax? (select all that apply)

1. Respiratory distress 2. Hypotension 3. Diminished breath sounds over hemithorax 4. Hyperresonance 5. Mediastinal shift 6. JVD

Respiratory distress with hypotension → think what?

Tension pneumothorax

What is the management of tension pneumothorax? (select all that apply)

1. Needle decompression 2. Chest thoracostomy tube 3. Airway monitoring 4. Pain control

What are the causes of increased intra-abdominal pressure? (select all that apply)

1. Excess fluid admin → gut edema 2. Trauma 3. Burn 4. Liver transplant 5. Massive ascites, abd surgery 6. Ruptured AAA 7. Pelvic fracture w/ bleeding 8. Pancreatitis

What intra-abdominal pressure suggests intra-abdominal hypertension with organ dysfunction?

IAP > 20-30 with acute organ dysfunction

What are the signs of increased intra-abdominal pressure? (select all that apply)

• Difficult to find as many are already critically ill

• Tense, distended abd

• Progressive oliguria

• Hypotension, tachycardia, JVD, acute pulmonary decompensation

What is the management of increased intra-abdominal pressure? (select all that apply)

1. Pain control, sedation 2. Improved positioning (supine) 3. Paralysis 4. Reduce intra-abdominal volume (drainage) 5. Abdominal decompression

Is SIRS part of the definition of sepsis?

No - SIRS may be caused by other entities

What are the SIRS criteria? (select all that apply)

1. Temp > 100.4°F or < 96.8°F 2. HR > 90 bpm 3. RR > 20 breaths/min 4. WBC > 12k or < 4k

How many SIRS criteria are needed for positive SIRS?

≥ 2

Can SIRS occur without infection?

Yes - it can occur just from having surgery (postop abnormal vitals without infection)

What are the risk factors for postoperative SIRS? (select all that apply)

1. Major surgery 2. Elderly 3. Longer operative times 4. Multiple comorbidities