Acute care: Circulatory failure and use of inotropes
In the fifth part of our series about acute care, Nicola Cooper discusses circulatory failure and using inotropes
I bet you never realised that the dry physiology learnt at medical school would turn out to be so important later on. Let us start with blood pressure: Ohm's law has been adapted to demonstrate that blood pressure (BP) is the product of cardiac output (CO) and systemic vascular resistance (SVR)--that is, BP=CO*SVR. Therefore a low blood pressure can be due to a low cardiac output (low flow) or reduced systemic vascular resistance (vasodilatation) or both. Pressure and flow are not the same thing. There is no “normal” blood pressure. What matters is whether a low blood pressure is causing a problem.
Acute renal failure commonly results from hypotension leading to hypoperfusion of vital organs. The interesting thing is, some of this is preventable. At risk patients can be easily identified and observed closely. Acute renal failure carries a high mortality (around 50% unselected cases)--so it is better to prevent