Advanced practice note
Spinal anaesthesia is a haemodynamic intervention before it is a technique
Block height matters, but the more useful question is how sympathetic block, venous return, vascular tone, and baseline physiology will interact.
A technically uncomplicated spinal can still produce a difficult haemodynamic course. The important physiology is not limited to sensory level. Sympathetic block changes venous capacitance and vascular tone, and the effect of that change depends on baseline volume status, ventricular function, autonomic reserve, positioning, and the speed with which the block develops.
Preparation is therefore an exercise in anticipation. Decide what the patient is most likely to need before the pressure falls, choose a monitoring and vasopressor strategy that fits the context, and communicate when surgical positioning or uterine displacement may materially alter venous return.
Good regional anaesthesia is not passive observation after injection. It is continuous interpretation of a changing circulation, with interventions chosen for physiology rather than habit.