1. Shock is defined as cellular hypoxia due to reduced oxygen delivery, increased oxygen consumption, or inadequate utilization and can progress from cellular to systemic effects if unchecked. 2. Shock is classified based on pathophysiology into hypovolemic, cardiogenic, obstructive, distributive, and neurogenic types. 3. The document provides an overview of the pathogenesis, classification, treatment goals and strategies for each shock type to guide clinical management.

1. Shock: Pathophysiology
& Current Management
Dr. Fiifi Brakatu
Surgical Resident

2. Outline
Definition
Pathogenesis
Classification of Shock - Pathophysiology and Management Strategies
Approach to Unexplained Shock
Scenarios

3. Definition
Shock is a state of cellular and tissue hypoxia due to either:
● Reduced oxygen delivery
● Increased oxygen consumption
● Inadequate oxygen utilization
Or a combination of these processes
NB: A patient can be hypertensive or normotensive and still be in shock!

4. Pathogenesis
Cellular Hypoxia results in:
● Cell membrane ion pump dysfunction
● Intracellular edema
● Leakage of intracellular content into extracellular space
● Inadequate regulation of intracellular pH

5. Pathogenesis
If shock is unchecked progresses to a systemic level resulting in:
● Acidosis
● Endothelial dysfunction
● Further stimulation of the Inflammatory and Anti-inflammatory pathway
● Further impairment of regional blood flow from complex humoral and
microcirculatory processes

6. General Management Strategies

7. Classification of Shock

8. Hypovolemic Shock
Hemorrhagic
● Trauma
● GI bleeding
● Tumor erosion into vessels
Non-hemorrhagic
● GI losses
● Renal losses
● 3rd space losses

9. Classification of Haemorrhagic Shock

10. Treatment Goals
Restore adequate organ perfusion and tissue oxygenation
● Early control of haemorrhage - employ damage control principles
● Adequate volume resuscitation - correct IVFs + blood products; massive
transfusion protocol (1:1:1)
● Avoid the lethal triad - acidosis, coagulopathy and hypothermia
Resus is complete when O2 debt is repaid, tissue acidosis corrected and aerobic
metabolism restored

11. Endpoints in resuscitation
Arterial BP (MAP), Heart rate, Urine output, CVP and Pulmonary artery occlusion
pressure are poor indicators of tissue perfusion

12. Obstructive Shock
Mechanical:
● Tension pneumothorax
● Massive Hemothorax (eg,
trauma, iatrogenic)
● Pericardial tamponade
● Severe dynamic hyperinflation
(eg, elevated intrinsic PEEP)
● Left or right ventricular outflow
tract obstruction
● Abdominal compartment
syndrome
● Aorto-caval compression (eg,
positioning, surgical retraction)
Pulmonary Vascular:
● Hemodynamically significant
pulmonary embolus
● Severe pulmonary hypertension
● Severe or acute obstruction of the
pulmonic or tricuspid valve
● Venous air embolus

13. Pathophysiology of Obstructive Shock
Mechanical obstruction of venous return
● Increased intrapleural pressure(tension pneumothorax)
● Increased intrapericadial pressure (cardiac tamponade) resulting in impeding
right atrial filling
Results in decreased CO with increased CVP

14. Rx
Tension Pneumo - Needle decompression (8cm needle depth) + ICD
Massive Haemothorax - ICD +/- urgent thoracotomy if initial drainage >1.5L or
200ml/hr for 2 to 4hrs or persistent need for blood transfusion
Pericardial tamponade - Pericardiocentesis or Pericardial window (subxiphoid or
transdiaphragmatic approach +/- exploration of heart (anterior thoracotomy, median
sternotomy or clamshell thoracotomy)

15. Cardiogenic Shock
Cardiomyopathic:
● Myocardial infarction
(involving >40% of the left
ventricle or with extensive
ischemia)
● Severe right ventricle
infarction
● Acute exacerbation of
severe heart failure from
dilated cardiomyopathy
● Stunned myocardium from
prolonged ischemia (eg,
cardiac arrest,
hypotension,
cardiopulmonary bypass)
● Advanced septic shock
● Myocarditis
● Myocardial contusion
● Drug-induced (eg, beta
blockers)
Arrhythmogenic:
● Tachyarrhythmia –
Atrial tachycardias
(fibrillation, flutter,
reentrant tachycardia),
ventricular tachycardia
and fibrillation
● Bradyarrhythmia –
Complete heart block,
Mobitz type II second
degree heart block
Mechanical:
● Severe valvular
insufficiency
● Acute valvular rupture
(papillary or chordae
tendineae rupture,
valvular abscess)
● Critical valvular stenosis
● Acute or severe
ventricular septal wall
defect
● Ruptured ventricular
wall aneurysm
● Atrial myxoma

16. Cardiogenic Shock
Failure of heart to deliver adequate cardiac output
Patient may have longstanding cardiac pathology
Rule out myocardial contusion in all chest trauma
● 12 lead ECG - if in keeping with MI changes, do cardiac enzymes and keep on monitor
Judicious use of IVFs followed by Inotropes - Dobutamine and Noradrenaline (or adrenaline
Infusion - titrate strength based on volume status)
Morphine
Anticoagulation
Broadspectrum anti-arrythymics (amiodarone)
Intra-aortic Balloon Pump, Impella Heart, ECMO

18. Distributive Shock
● Sepsis
● Inflammatory shock (SIRS) – Burns, trauma,
pancreatitis, postmyocardial infarction, post coronary
bypass, post cardiac arrest, viscus perforation, fat
embolism syndrome
● Neurogenic shock – TBI, SCI, neuraxial anesthesia
● Anaphylactic shock
● Other – Liver failure, transfusion reactions, vasoplegia
(eg, vasodilatory agents, cardiopulmonary bypass)

19. Pathophysiology of Distributive shock
Severe peripheral vasodilatation triggered by:
Septic shock - dysregulated host response to infection
SIRS - robust inflammatory response from a major body insult
Neurogenic shock - Interruption of autonomic pathways resulting in decreased
vascular resistance and altered vagal tone
Anaphylactic Shock -Severe IgE-mediated allergic response

20. Overview of the Autonomic Nervous System
Based on the reflex arc
● Afferent Limb - transmits info from periphery to spinal cord via dorsal root
ganglion to spinal cord or cranial nerves to brain
● Efferent Limb - pre- and post-ganglionic fibers + autonomic ganglion
● Central Integrating System - simple reflexes completed within organ system
and complex ones within hypothalamus and brain stem

21. Autonomic Ganglia
Parasympathetic - Craniosacral - CN3,7, 9, 10 and
S2-S4
Sympathetic
Pre-ganglionic -cell bodies in the grey matter of
lateral horns of T1 to L2/L3
Preganglionic fibers synapse with postganglionic
neurones in the ganglia of the sympathetic chain (2
paravertebral chains)
Postganglionic fibers leave ganglia to join spinal or
visceral nerves to innervate target organs

22. Paravertebral Sympathetic Chain
4 parts:
Cervical - 3 ganglia (superior, middle and inferior)
Inferior cervical ganglion fuses with T1 ganglion to form stellate ganglion
Thoracic - T1-T5 supply aortic, cardiac and pulmonary plexus
Lumbar - Prevertebral ganglia. Branches form the coeliac plexus
Pelvic - sacral ganglia

23. Neurogenic shock
Different from Spinal shock
SCI at or below T6 because of loss of thoracic sympathetic outflow
Decreased venous tone resulting in blood pooling in extremities and hypotension
Bradycardia - Decreased sympathetic tone to the heart
Core hypothermia with warm extremities - from peripheral pooling
Rx - Judicious IVFs + Inotropes (noradrenaline or adrenaline infusion) +/-atropine for
bradycardia

25. Combined (Mixed) Shock
Patient with sepsis/pancreatitis(distributive shock) may have a
hypovolemic component(decreased intake, vomiting, diarrhea, etc)
Polytrauma patient with SCI (neurogenic) and abdominal or
extremity trauma (hypovolemic)

26. APPROACH TO UNEXPLAINED
SHOCK IN TRAUMA
ATLS Series - C-spine, CXR, AP Pelvis X-Rays +/- Lodox scan
CT Brain
Rule out the Deadly Dozen with a checklist!
FAST!
CT Abdo if FAST positive
Repeat neuro exam and document spinal level if any.

27. THE DEADLY DOZEN
LETHAL SIX
● AIRWAY OBSTRUCTION
● TENSION PNEUMOTHORAX
● OPEN PNEUMOTHORAX
● MASSIVE HEMOTHORAX
● CARDIAC TAMPONADE
● FLAIL CHEST
HIDDEN SIX
● THORACIC AORTIC
DISRUPTION
● TRACHEOBRONCHIAL
DISRUPTION
● ESOPHAGEAL DISRUPTION
● MYOCARDIAL CONTUSION
● PULMONARY CONTUSION
● DIAPHRAGMATIC TEAR

29. Diaphragmatic Tear
Continuous diaphragm sign on CXR
Rx - Laparoscopic diaphragmatic repair

30. Tracheobronchial
Disruption
Continuous/unexplained pleural leaks
Persistent pneumothorax
Lobar atelectesis
Pneumomediastinum
Deep cervical subcutaneous
emphysema
Rx- bronchoscopy + primary
repair/pneumonectomy

32. Q1
34yo M unrestrained driver in RTA with scalp laceration, bloody otorrhea, battle’s
sign and racoon eyes, limb lacerations and abdominal abrasions. Darkened skin
around upper thigh and waist, GCS - 13/15. Spine cleared by xrays. BP - 116/72 HR -
123 SpO2- 92% NRM at 15L/min. Cold, clammy extremities. What type of shock is
this?
A. Neurogenic
B. Distributive
C. Hypovolemic
D. Cardiogenic
E. Obstructive

33. Q2
27yo M motorcyclist presents with bilateral femur fractures, rib fractures and right
haemothorax. He is combative. SpO2 - 88% NRM at 15L/min, BP - 106/73 HR - 123
Temp - 38.2. You notice a petechial rash over his chest. What type of shock is this?
A. Hypovolemic
B. Obstructive
C. Distributive
D. Combined Hypovolemic & Distributive
E. Neurogenic

34. Q3
42yo F, helmeted pillion rider who fell from motorcycle after sudden deceleration.
Abrasions on chest and right breast. GCS-15/15. 2 rib fractures on the right with mild
chest contusion. Rest of exam unremarkable. FAST - Negative. BP - 78/51 HR - 54
SpO2 - 100% on 4L INO2. HO gives adequate IVFs but BPS don’t improve and
patient arrests at TSEU. What type of shock is this?
A. Hypovolemic
B. Distributive
C. Cardiogenic
D. Neurogenic
E. Obstructive

35. Q4
44yo M fell from a 3m height while painting. Abrasions on his upper back. ℅ pain
on upper body. No obvious external injuries. GCS 15/15. Warm extremities but
temperature 35.8deg. BP - 86/58, HR - 52, SpO2 99% on NRM 10L/min. Power is
5/5 in upper limbs but 1/5 in lower limbs. Altered sensation on lower limbs. Absent
anal wink and bulbocavernosus tests. What type of shock is this?
A.Spinal
B. Neurogenic
C. Combined Spinal & Neurogenic
D. Hypovolemic
E. Cardiogenic

37. Resources
ATLS Manual - 10th Edition
Barber AE, Shires GT. Cell damage after shock. New Horiz. 1996 May;4(2):161-7. PMID: 8774792.
Cannon JW. Hemorrhagic Shock. N Engl J Med. 2018 Jan 25;378(4):370-379. doi: 10.1056/NEJMra1705649. PMID: 29365303.
Sabiston Textbook of Surgery - 21st Edition
Schwartz’s Principles of Surgery - 11th Edition