Beta-endorphin and catecholamine concentrations during chronic and acute stress in intensive care patients

Only little information is available on the effects of acute and chronic stress on the opioid and adrenergic systems in patients at intensive care units. Animal models showed a stimulation of beta-endorphin and catecholamines.

In the present study, in 12 patients who were intubated and were receiving artificial respiration because of cardiopulmonary resuscitation or primary respiratory failure, venous plasma concentrations of adrenaline, noradrenaline and beta-endorphin immuno-reactive material (IRM) were determined by a radioimmunoassay. In these patients, regular endobronchial suctioning was necessary. For inducing acute stress patients underwent three different methods of endobronchial suctioning or lavage.

In all patients concentrations of both adrenaline (529 +/- 117 pg/ml) and noradrenaline (2694 +/- 262 pg/ml) were increased above normal resting values. In 5 patients plasma beta-endorphin IRM concentration was below the detection limit, the other patients had beta-endorphin IRM concentrations above normal (26.65 +/- 3.80 pg/ml). Epinephrine (227 +/- 33 vs. 743 +/- 189 pg/ml; p < 0.01) and norepinephrine (1673 +/- 161 vs. 3423 +/- 368 pg/ml; p < 0.001) were significantly lower in the group with undetectable beta-endorphin IRM concentrations than in the group with detectable beta-endorphin IRM whereas heart rate was significantly higher (120/min vs. 99/min; p < 0.0003). beta-endorphin IRM concentrations were correlated negatively to heart rate (-0.55; p < 0.0005) and positively to the noradrenaline concentration (0.56; p < 0.0004). Artificially ventilated patients showed increased levels of beta-endorphin (19.27 +/- 3.16 pg/ml) as compared to the spontaneously breathing patients (13.29 +/- 4.34 pg/ml). Following acute stress due to endobronchial suctioning or lavage, blood pressure (150/70 mmHg vs. 172/81 mmHg; p < 0.01) and heart rate (107/min vs. 119/min; p < 0.005) increased in all patients, the other parameters did not.

It is concluded that beta-endorphin IRM concentration in the plasma is linked to epinephrine and norepinephrine concentrations under intensive care conditions. Endobronchial lavage or suctioning does not influence beta-endorphin IRM levels in plasma.