Immunomodulation: an important concept in modern anaesthesia

This review summarises evidence for immunomodulatory effect of drugs administered peri-operatively. The clinical significance of the balance of pro- and anti-inflammatory cytokines may be seen in certain disease states, for example, meningococcal meningitis and Lyme arthritis. This balance may be altered peri-operatively. Traditionally, these changes are considered to be due to the stress response of surgery, the response to cardiopulmonary bypass, or endotoxaemia. This review presents in vitro evidence suggesting that drugs modulating this cytokine balance include non-steroidal anti-inflammatory agents, phosphodiesterase inhibitors and opioids, acting through effects on intracellular cyclic nucleotide messenger systems. An important consequence of the pro-inflammatory cytokine activity is increased adhesion of neutrophils. Aspects of this process may be inhibited by avoiding low blood flow states, by reducing adhesion molecule expression (for example by use of pentoxifylline), or by use of negatively charged anions such as heparin. Neutrophil activity is generally depressed by intravenous anaesthetic induction agents, but is enhanced by opioids. Natural killer cell activity, which is involved in immunity against tumour cells and virally infected cells is transiently depressed by volatile anaesthetic agents and opioids. In contrast catecholamines enhance natural killer cell activity. Whereas decrease in immunoglobulin levels occur peri-operatively, this is not thought to be as a result of drugs at clinically used concentrations but rather due to haemodilution.