Anaes · Vascular anaesthesia
Aortic cross-clamp physiology: clamp-on and clamp-off
Also known as Aortic cross-clamp physiology: clamp-on and clamp-off · Declamping shock · Infrarenal clamp physiology
Exam-exhaustive aortic cross-clamp on and off physiology for vascular and major aortic anaesthesia: afterload and cardiac output vectors, myocardial ischaemia risk, organ ischaemia by clamp level, declamping shock, potassium and lactate washout, drug preparation, monitoring and RCRI context for ANZCA Final and equivalents.
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Target exams
Red flags
- Clamp-on: ↑SVR, ↑BP, ↓CO risk, LV strain.
- Clamp-off: ↓SVR, acidosis washout, hypotension.
- Suprarenal clamp worsens renal ischaemia.
- Prepare drugs before each transition.
- Cardiac disease multiplies risk (RCRI).
Meet the patient
A 72-year-old smoker with hypertension and a 6 cm infrarenal abdominal aortic aneurysm presents for open repair. His creatinine is slightly raised, he has a 40-pack-year history, and his exercise tolerance is four flights before angina. The surgeon plans an infrarenal cross-clamp. Your job is to manage two violent haemodynamic transitions — moment clamp goes on and the moment it comes off — without losing the heart or the kidneys.[1]
The two questions that own this case: can the left ventricle tolerate the sudden afterload jump when the clamp closes? and can the circulation survive the vasodilatory washout when it opens? Everything below is preparation for those two moments — the clamp-on/clamp-off pathophysiology scope.[3]
References6ShowHide
- [1]Lee TH, Marcantonio ER, Mangione CM, et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation, 1999.PMID 10477528
- [2]Devereaux PJ, Yang H, Yusuf S, et al. Effects of extended-release metoprolol succinate in patients undergoing non-cardiac surgery (POISE trial): a randomised controlled trial. Lancet, 2008.PMID 18479744
- [3]Gelman S The pathophysiology of aortic cross-clamping and unclamping. Anesthesiology, 1995.PMID 7717537
- [4]Gelman S, McDowell H, Varner PD, Pearson J The reason for cardiac output reduction after aortic cross-clamping. Am J Surg, 1988.PMID 3128132
- [5]Colson P, Ribstein J, Séguin JR, et al. Mechanisms of renal hemodynamic impairment during infrarenal aortic cross-clamping. Anesth Analg, 1992.PMID 1616156
- [6]Loggi S, Mininno N, Damiani E, et al. Changes in the sublingual microcirculation following aortic surgery under balanced or total intravenous anaesthesia: a prospective observational study. BMC Anesthesiol, 2019.PMID 30611197