Carbocations are species bearing a formal + charge on carbon. The have sp2 hybridization and trigonal planar geometry, with an empty p orbital on carbon, perpendicular to the plane containing the substituents (see diagrams shown to the right).
Aortic cross-clamp. An aortic cross-clamp is a surgical instrument used in cardiac surgery to clamp the aorta and separate the systemic circulation from the outflow of the heart. An aortic cross-clamping procedure serves, for example, in the repairing of coarctation of the aorta.
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).