Causes of shock in the cardiac surgical patient

The below summary is directed at all the similarly themed CICM written questions. "Why is this post-bypass patient so hypotensive", they whinge. Typically, an approach to the haemodynamically unstable cardiac surgical patient is being tested.

Such questions have included the following:

The candidate is expected to regurgitate a list of sensible differentials. The easiest way to organise these? Anybody's guess. Additionally, not only hypotension, but also hypertension can complicate post-op recovery, and it is included here because it also fits the definition of "haemodynamic instability".

The following table is presented as an alternative to the official college answer for Question 5 from the first paper of 2006.

Causes of Shock in the Post-Bypass Patient
Type of shock Cause Diagnostic strategy Management
Artifact of measurement Arterial blood pressure measurement is inaccurate Compare with non-invasive measurement and physical examination
  • Re-zero and recalibrate the arterial line
  • Resite arterial line or change the transducer
Cardiogenic Post-operative stunning of the myocardium TTE, ECG, cardiac output measurement by PiCCO or PA catheter
  • Fluid resuscitation
  • Commence inotrope infusion
  • Correct rhythm if in AF
  • Return to theatre, recommence cardiopulmonary bypass
  Myocardial infarction TTE, ECG, cardiac enzymes
  • Consider IABP
  • Thrombolysis or anticoagulation likely contraindicated given recent cardiac surgery
  • Return to theatre
Obstructive Cardiac tamponade TTE, CVP trace
  • Fluid resuscitation
  • Emergency pericardiocentesis
  • Return to theatre
  Massive pulmonary embolism TTE, CVP trace, ECG, CTPA
  • Consider emergency embolectomy
  • Thrombolysis or anticoagulation likely contraindicated given recent cardiac surgery
  Tension pneumothorax

Physical examination;


  • Emergency decompression
  • Chest drain
Neurogenic Infarction of spinal cord due to ischaemia or embolic events Physical examination features, CT, MRI
  • Thrombolysis or anticoagulation likely contraindicated given recent cardiac surgery
  • commence vasopressor infusion
Hypovolemic Blood loss post operatively Examination of drains, FBC,
  • Replace blood products and red cells
  • Fluid resusiciation
  • Maintain normal acid-base balance and normothermia
  • return to theatre
  Massive diuresis Observation of fluid balance charts
  • Replace lost fluid volume
  • Rewarm patient to normal temperature
Distributive Vasoplegia SVRI measurements by PiCCO
  • commence vasopressor infusion; consider vasopressin or methylene blue
  Anaphylaxis Physical examination findings suggestive of angioedema
  • Adrenaline IM or as infusion
  • Withdrawal of the trigger substance
  • Corticosteroids and antihistamines

Causes of post-cardiotomy instability, organised by alphabetical mnemonic order

A - Artifactual; art line is incorrectly zeroed

B - Tension pneumothorax

C - Cardiac tamponade

   - Myocardial ischaemia

   - Acute valvular failure (eg. of grafted valve)

   - LVOT obstruction

   - Post-bypass myocardial depression

   - Arrhythmia (eg. AF)

D - Excess sedative (eg propofol)

E - Post-bypass hypocalcemia

F - Inadequate preload - need more fluid


H - Haemorrhage - inadequately reversed heparinisation or DIC

   - could be into pericardial sack or pleural space

I - Anaphylaxis; reaction to anaesthetic agents

   - Vasoplegia due to circuit-induced SIRS

Causes of post-cardiotomy instability, organised by affected haemodynamic variable

  • Preload
    • Inadequate intraoperative fluid
    • Haemorrhage
    • Valve failure (mitral / tricuspid)
  • Rate
    • Bradycardia (or excessive tachycardia!)
  • Rhythm
    • AF or other arrhythmia
  • Contractility
    • Post-bypass myocardial depression
    • Myocardial ischaemia
  • Afterload
    • Artifact: art line is incorrectly zeroed
    • LVOT obstruction
    • Anaphylaxis
    • Vasoplegia
    • Valve failure (aortic or pulmonic)

Post-cardiothoracic surgical bleeding complications

Sadly, bleeding complications are common enough to merit their own chapter. Excessive bleeding is usually due to one or more of the following factors:

  • incomplete surgical hemostasis
  • residual heparin effect after cardiopulmonary bypass
  • platelet abnormalities (platelet dysfunction and thrombocytopenia – from bypass circuit consumption , antiplatelet agents etc)
  • hypothermia
  • postoperative hypertension
  • clotting factor depletion
  • hemodilution (dilutional thrombocytopenia and coagulopathy)


Frederick A. Hensley, Jr., M.D., Donald E. Martin, M.D.,  Glenn P. Gravlee, M.D. A Practical Approach to Cardiac Anaesthesia, 3rd ed. Sibylle A. Ruesch and Jerrold H. Levy. CHAPTER 9. The Postcardiopulmonary Bypass Period: A Systems Approach. 2003 by LIPPINCOTT WILLIAMS & WILKINS

André, Arthur C. St, and Anthony DelRossi. "Hemodynamic management of patients in the first 24 hours after cardiac surgery." Critical care medicine 33.9 (2005): 2082-2093.

Eagle, Kim A., et al. "ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery).Circulation 110.14 (2004): e340.

Goepfert, Matthias SG, et al. "Goal-directed fluid management reduces vasopressor and catecholamine use in cardiac surgery patients." Intensive care medicine 33.1 (2007): 96-103.

Marik, Paul E. "Hemodynamic parameters to guide fluid therapy." Transfusion Alternatives in Transfusion Medicine 11.3 (2010): 102-112.

Almassi, G. Hossein, et al. "Atrial fibrillation after cardiac surgery: a major morbid event?." Annals of surgery 226.4 (1997): 501.

Maisel, William H., James D. Rawn, and William G. Stevenson. "Atrial fibrillation after cardiac surgery.Annals of Internal Medicine 135.12 (2001): 1061-1073.

BUCKLEY, MORTIMER J., et al. "Intra-aortic balloon pump assist for cardiogenic shock after cardiopulmonary bypass." Circulation 48.1S3 (1973): III-90.

Licker, Marc, et al. "Clinical Review: Management of weaning from cardiopulmonary bypass after cardiac surgery.Annals of cardiac anaesthesia15.3 (2012).

Lavana JD, Fraser JF, Smith SE, Drake L, Tesar P, Mullany DV. Influence of timing of intraaortic balloon placement in cardiac surgical patients. J Thorac Cardiovasc Surg 2011;140(1):80-5.

Maas, Jacinta J., et al. "Cardiac Output Response to Norepinephrine in Postoperative Cardiac Surgery Patients: Interpretation With Venous Return and Cardiac Function Curves*." Critical care medicine 41.1 (2013): 143-150.

Hajjar, L., et al. "Vasopressin Versus Norepinephrine for the Management of Shock After Cardiac Surgery (VaNCS study): a randomized controlled trial." Critical Care17.Suppl 2 (2013): P222.