Plasma catecholamine levels in porcine Escherichia coli septicaemia and following treatment with buprenorphine or naloxone.

Changes in plasma catecholamine levels in response to the induction of shock and following treatment with buprenorphine or naloxone were determined in a porcine model of Escherichia coli septicaemia. Thirty animals were anaesthetised with alpha-chloralose and infused with live E. coli over 2 hr. One hour after starting the infusion, cardiac index, mean arterial pressure, and pH had decreased significantly (P < 0.001), and there was a significant increase in mixed venous blood lactate concentrations (P < 0.001). This was associated with significant increases in plasma concentrations of adrenaline and noradrenaline (P < 0.001). There was a strong correlation between the extent of the increase in circulating catecholamines and the severity of shock (as reflected by haemodynamic changes and lactic acidosis) as well as significantly higher peak plasma catecholamine concentrations (P < 0.01) and dramatic terminal increases in circulating catecholamines in nonsurviving animals. Animals were randomly divided into three groups and received either naloxone or buprenorphine or an equivalent volume of normal saline and were monitored for a further 3 hr. Both naloxone and buprenorphine produced significant improvements in cardiac index (P < 0.05) and limited the development of acidosis (P < 0.05). This was not associated with any further increase in plasma catecholamine concentrations; indeed, catecholamine levels tended to decrease in treated animals but continued to increase in controls. In summary, we have shown a correlation between the increase in plasma catecholamines and the severity of shock in this model. In addition, we observed that the beneficial effects of treatment with buprenorphine or naloxone were not accompanied by any further increase in plasma catecholamine concentrations.