In relation to cardiac surgery:
a) What are the complications of aortic cross clamping and cardiopulmonary bypass that may affect the post-operative ICU management? (80% marks)
b) What are the major risks from internal mammary artery grafting? (10% marks)
c) What are the major risks from radial artery grafting? (10% marks)
ALTERNATIVE TEMPLATE BASED ON PATHOPHYSIOLOGY
Artery spasm/kinking/thrombosis - resultant myocardial ischaemia/LVF
Increased risk of sternal devascularisation-> sternal non-union and infection especially with bilateral IMA grafts
Increased post-op bleeding with bilateral IMA harvesting Aneurysm/pseudo-aneurysm of artery formation
Spasm -> cardiac ischaemia
Arm complications-> haematoma/haemorrhage, infection, motor impairment (usually temporary), sensory impairment, pain, distal ischaemia (rare)
Answers generally lacked structure and detail.
|Bypass circuit mechanism||Hemodilution|
|Blood loss into the circuit|
|SIRS due to bypass|
|SIRS due to bypass||Coagulopathy due to coagulation cascade activation and clotting factor depletion|
|Platelet dysfunction and platelet depletion|
|Renal failure due to SIRS|
|Acute lung injury due to SIRS, "pump lung"|
|Anticoagulation and reversal||Bleeding from residual heparin|
|Anaphylaxis to protamine|
|Increased pulmonary resistance due to protamine|
|Right ventricular failure due to protamine-induced pulmonary hypertension|
|Prolonged hypothermia||Heart block|
|Ventricular and atrial arrhythmias|
|Hyperglycaemia (decreased insulin production as well as insulin insensitivity)|
|Decreased tubular resorption in the kidney (thus diuresis)|
|Phrenic nerve palsy (“cold slush cardioplegia”)|
|Prolonged ischaemia||Renal failure due to ATN|
|Encephalopathy and neurocognitive deterioration|
|Hepatic dysfunction and delayed drug clearance|
|Mechanics of surgery||Atelectasis (especially of the LLL) due to mechanical compression|
|Embolic complications||Myocardial infarction|
|Stroke (eg. air or cholesterol emboli)|
Complications of internal mammary artery grafting (von Segesser et al, 1990)
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.
von Segesser, Ludwig K. "Complications of Internal Mammary Artery Grafting." Arterial Grafting for Myocardial Revascularization. Springer, Berlin, Heidelberg, 1990. 102-108.
Budillon, Alessandro Maria, et al. "Complications after radial artery harvesting for coronary artery bypass grafting: our experience." Surgery 133.3 (2003): 283-287.
Buxton, Brian, et al. "The radial artery as a bypass graft." Current opinion in cardiology 11.6 (1996): 591-598.