Local anaesthetics and additives for spinal anaesthesia--characteristics and factors influencing the spread and duration of the block.

Different characteristics of patients and local anaesthetic formulations will influence the spread of spinal anaesthesia. The predictability of the spread of spinal anaesthesia can be improved by altering both baricity of the solution, and the position of the patient during the intrathecal local anaesthetic injection. The role of adrenaline and clonidine in prolonging the block and associated side effects is discussed. The role of opioids added to local anaesthetic solutions is discussed from a cost/benefit point of view.