Physiological Model

Mild to moderate hypotension is a very common event, but must not be ignored.

Management includes:

Correcting the cause (if possible)
Intravenous fluids
Sympathomimetic drugs
Decreasing anaesthetic depth (if GA)

One way to consider the causes of intra-operative hypotension is to think about the factors contributing to BP, Fig 1.

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Fig 1 From Ohm’s Law, pressure = flow × resistance, and for the cardiovascular system, flow is the same as cardiac output (= HR × SV). Resistance can be taken as systemic vascular resistance (SVR)