Complications: If the cross-clamp is suprarenal, can have renal failure, hepatic ischemia and coagulopathy, bowel infarction, and paraplegia. Most consistent response is arterial hypertension above the clamp and hypotension below the clamp. Hypertension is due to increase in afterload (systolic ventricular wall tension). Other consequences of cross clamping include : increased segmental wall motion abnormalities, increased wedge pressure (PCWP) and CVP, increased coronary blood flow, increased mixed VO2 (decreased O2 consumption, decreased O2 extraction), increased epi/norepi, decreased EF, decreased CO, decreased RBF, decreased CO2 production, respiratory alkalosis, and/or metabolic acidosis. Heart rate and stroke work are not necessarily changed.
Confounding Variables: Variables affecting response to cross clamp include : myocardial contractility, preload, blood volume, and activation of the sympathetic nervous system.
Preparation/Treatment: Preparation for (and treatment of) clamping includes: increased depth of anesthesia, shunt by surgeon, branch artery perfusion, left-heart bypass, sodium nitroprusside, nitroglycerin, furosemide (Lasix), Mannitol, hypothermia, decreased minute ventilation, and sodium bicarbonate (HCO3).
When cross clamp comes off, have vasopressors ready (epi, norepi, etc.). Be prepared to give volume and manage hyperkalemia, acidosis, and possible cardiac arrhythmias.