Question 13 and Question 14 both relate to the following clinical scenario:
A 71-year-old man is transferred to your intensive care unit following a mechanical aortic valve replacement and coronary artery bypass surgery.
The anaesthetist reports that he came off bypass readily, has not required any inotropic support, and has epicardial pacing wires in situ. However, shortly after arrival his blood pressure falls to 60/30.
a) Outline your differential diagnosis for his hypotension
His blood pressure improves rapidly with a fluid bolus, and examination is otherwise unremarkable. However, he is noted to lose 250ml of blood from his mediastinal drains over the next 30 minutes.
b) List 4 likely causes of, or contributors to, excessive post-operative bleeding in this setting, and outline your immediate management.
a) Differential diagnosis for hypotension
b) Causes of post-operative bleeding and management
This question revisits the topic of post-cardiothoracic surgery complications. Ruesch and Levy, in their chapter from Practical Approach to Cardiac Anaesthesia have nice point-form guides which calmly deal with the stressful situation of haemodynamic instability after bypass. (in general, that book is awesome). I have made my own notes on this subject, but I claim no special expertise in it. There I categorise the differential diagnosis for hypotension in the post-bypass patient, as well as the various steps one needs to take in assessing the medical and surgical causes of bleeding.
In general, it is good to organise the answer to these in the system of "measurement error, preload, contractility, afterload, rate and rhythm"; or any other system (any is better than none).
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
...Or: excessive preload in the failing left heart - causing diastolic dysfunction of the left heart
G - Arterial embolism of the mesenteric vessels (chaos ensues)
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
Excessive bleeding is usually due to one or more of the following factors:
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.
Estafanous, Fawzy G., and Robert C. Tarazi. "Systemic arterial hypertension associated with cardiac surgery." The American journal of cardiology 46.4 (1980): 685-694.
Roberts, A. J., et al. "Systemic hypertension associated with coronary artery bypass surgery. Predisposing factors, hemodynamic characteristics, humoral profile, and treatment." The Journal of thoracic and cardiovascular surgery 74.6 (1977): 846-859.
Ilabaca, Patricio A., John L. Ochsner, and Noel L. Mills. "Positive end-expiratory pressure in the management of the patient with a postoperative bleeding heart." The Annals of thoracic surgery 30.3 (1980): 281-284.