Plasma concentrations and hemodynamic changes after repeated interpleural injections of bupivacaine-epinephrine.

BACKGROUND AND OBJECTIVES

The purpose of this investigation was to study the arterial plasma concentrations of bupivacaine and the hemodynamic changes after interpleural injection of 20 ml 0.5% bupivacaine with epinephrine in patients treated by chest drainage for spontaneous pneumothorax.

METHODS

Twenty-two patients with spontaneous pneumothorax planned to be treated by chest drainage were randomly allocated to a bupivacaine group and a control group receiving saline. After introduction of the chest drain and evacuation of the pneumothorax, 10 injections through an interpleural catheter were given at 8-hour intervals in a double-blind fashion. Plasma concentrations were determined at 5, 10, 20, 30, 240, and 480 minutes after the first injection and before and at 15 and 30 minutes after the 4th, 7th, and 10th injections. Heart rate and mean arterial pressure was registered before and at 15 and 30 minutes after each injection.

RESULTS

Mean Cmax after the first injection was 1.02 +/- 0.24 microgram/ml at 15 minutes, the highest individual Cmax after 20 minutes being 1.56 micrograms/ml. Mean plasma concentrations increased up to and after the 4th injection but did not rise further after the 7th and 10th injections. The highest individual Cmax was 1.92 micrograms/ml at 15 minutes after the 10th injection. The injections were accompanied by a small but statistically significant reduction in mean arterial blood pressure and a rise in heart rate 15 minutes after injection in the bupivacaine group compared with the control group.

CONCLUSIONS

Repeated interpleural bolus injections of 20 ml 0.5% bupivacaine-epinephrine at 8-hour intervals are safe regarding plasma concentrations of bupivacaine. Small but statistically significant hemodynamic changes can be noticed, probably the result of beta- adrenergic stimulation by epinephrine.