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Shock

Shock (usually hypotensive)

↓ O2 delivery (↓ perfusion) or ↑ O2 consumption or ↓ oxygen utilization ➔ tissue/cellular hypoxia
- Without O2 for electron transport chain ➔ ↓ ATP
  - Switch to anaerobic respiration (less effective ATP production) ➔ lactic acid production (Lactate level correlates with severity of shock)
- Without intervention ➔ systemic progression
  - Metabolic acidosis & endothelial dysfunction (stays constricted) with shunting of regional blood flow ➔ further tissue injury
  - Eventually resulting in irreversible organ failure

Shock index = HR/systolic BP (Normal 0.4 - 0.7)

Higher is bad: a pt with systolic BP of 90 and HR of 120...
- 120/90 = 1.3
Not for use in pediatric pts because KIDS COMPENSATE (look fine and then decline rapidly)

Body's response to shock

SSX

Compensated (cryptic/pre) shock
- Activate sympathetic nervous and inhibit parasympathetic:
  - ↑ HR and vasoconstriction of peripheral vessels to ↑ systemic vascular resistance
    - May only see slight tachycardia and ↑ BP in young/healthy pts
- RAAS activation ➔ ↑↑ vasoconstriction, urine retention, thirst
Shock
- Body isn't able to keep up ➔ sx of organ dysfunction
  - Cool, clammy, hypotensive
  - Restless with hypotension & oliguria
End-organ dysfunction
- Irreversible organ damage ➔ multiorgan failure (MOF) ➔ death
  - Acute renal failure ➔ anuria
  - Acidosis blunts nervous/RAAS system and likely causes a further ↓ CO
  - Irreversible shock/refractory hypotension
  - Obtundation, coma, death

Hemodynamic profiles - PAC

Pulmonary artery catheter (PAC/Swan-Ganz/right heart catheter)

Measures CO, pulmonary capillary wedge pressure (PCWP), systemic vascular resistance
- PCWP: left atria end diastolic pressure (preload)
  - Hypovolemia, obstructive shock (PE) ➔ ↓ preload ➔ ↓ PCWP
  - ↑ end diastolic pressure (MI ➔ systolic failure, cardiac tamponade ) ➔ ↑ preload ➔ ↑ PCWP

PCWP aka pulmonary artery occlusion pressure, pulmonary artery wedge pressure
- There are way more measurements in PAC than just CO, PCWP, and SVR
- Like mixed venous oxygen saturation (SvO2): Oxygen saturation in pulmonary artery (the end result of O2 consumption/delievery)
  - Indicates how well O2 is being delivered to periphery
  - Usually < 65% in cardiogenic shock and pericardial tamponade (Normal SvO2 = 65 - 70%)

Hypovolemic

Leaking blood or non-blood fluids

Causes

Hemorrhagic
- Trauma, intra/post-op bleeding
- AAA
- GI bleed - ruptured varices, PUD
- Ruptured ectopic/postpartum uterine/hemorrhage
- Bleeding disorders
Non-hemorrhagic
- GI losses vomiting/diarrhea
- Burns
- Drug/osmotic diuresis, salt-wasting, hypoaldosterone
- Third spacing: intestinal obstruction, pancreatitis

SSX

Shocky
cool/clammy or dry, thready pulse, hypotension, cap refill >2s

DX

CBC
- Dehydration ➔ hemoconcentration ➔ ↑ hemoglobin/hematocrit
- Blood loss ➔ ↓ h/h

TX

If there is a hole... plug it
Bilateral lage bore IVs (and locks) for IVF resuscitation (NS or LR)
O-negative or cross matched packed RBCs in severe bleeds
- (NS doesn't carry oxygen)

Cardiogenic

Pumping issue ➔ backup ➔ ↑ preload

Causes

MI
Arrhythmias
HF/Cardiomyopathy
Myocarditis
AR/MR
β-blockers, CCB

SSX

Shocky, dyspnea (pulm edema), abnormal HS (S3/4, AR/MR)
Chest pain/palpitations/syncope
JVD

DX

EKG, cardiac markers, ECHO

TX

Tx underlying cause (PCI for MI)
Avoid aggressive IVF (don't add more work for heart)
O2 and inotropes to ↑ CO (dobutamine, EPI)
- Amrinone or intra-aortic balloon pump when all else fails

Obstructive

Impaired RV diastolic filling

Causes

Directly impaired filling:
Obstructed venous return
- Tension pneumo
↑ RV afterload
- PE, pulmonary HTN

SSX

Shocky + JVD + ssx related to cause
Pulsus paradoxus
Beck triad (tamponade): Hypotension, Muffled HS, JVD
Tension pneumo: SQ emphysema ➔ crepitus, ↓ breath sounds, hyperresonance
PE: Chest pain, syncope, dyspnea, hemoptysis, ↓ O2 sat despite supplemental O2

DX

PE, CXR, CT-A, ECHO (but don't wait to decompress)

TX

Decompress heart (tamponade ➔ pericardiocentesis, tension pneumo ➔ needle/chest tube, PE ➔ thrombolysis)

Distributive

Fluid redistributed from intravascular to extravascular (sepsis)

Widespread vasodilation (anaphylaxis)

Septic shock (leakage issue)

Infxn ➔ deleterious response
Systemic vasodilation ➔ ↓ systemic vascular resistance
MCC pneumonia

SSX

Flushed/warm skin initially ➔ shocky
Wide pulse pressure, ↑ RR (from acidosis)
Typically fever

DX

SIRS with persistent hypotension
↑ ESR, ↑ lactate, cultures, CBC: leukocytosis or leukopenia

TX

IVF and pressors (NE), broad spectrum ABX

Infection, trauma, inflammation ➔ SIRS

Systemic Inflammatory Response Syndrome
- 2/4 required:
  - Temp > 38° C (100.4 F)
  - HR >90
  - RR >20
  - WBC < 4k or > 12k
Sepsis: (SIRS + suspected/confirmed infxn)
Severe sepsis: sepsis with organ failure
Septic shock: persistent hypotension

Watch this to understand SOFA, qSOFA, SIRS, Sepsis (especially before clinicals)

Anaphylaxis (vasodilation issue)

Type I hypersensitivity reaction
Systemic vasodilation ➔ flushed/warm skin and ↓ systemic vascular resistance
Rapid onset

SSX

Shocky, tachy
Wheezing/stridor, flushed/urticaria/pruritus
GI: N/V/D

DX

Clinical

TX

EPI & antihistamines ± glucocorticosteroid
IVF & O2 (airway)

Neurogenic

Lost sympathetic tone ↑ parasympathetic (vagal) tone
- Peripheral vasodilation ➔ ↓ systemic vascular resistance
- Spinal cord injury (MC above T6), TBI, head bleed
- Neuraxial anesthesia (anesthetic in subarachnoidepidural space)

SSX

Brady
Wide pulse pressure

DX

CT to look for bleed

TX

Atropine/pacing for brady, IVF, pressors (EPI if HR < 60)

Next: Hypertension

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