Effects of tramadol and meperidine on respiration, plasma catecholamine concentrations, and hemodynamics

To evaluate the effects of high analgesic doses of tramadol and meperidine on respiration, plasma catecholamine concentrations, and hemodynamic parameters.

Randomized, double-blind, cross-over, controlled volunteer study.

Laboratory at a university hospital.

8 healthy male volunteers.

Tramadol was given as a 150 mg bolus plus a succeeding 3-hour steady infusion of 250 mg (83.3 mg/hr). Meperidine was given in a similar manner as a bolus dose of 112.5 mg plus 187.5 mg in a 3-hour steady infusion (62.5 mg/hr). Experimental pain was induced using a tourniquet.

Respiration was studied noninvasively with respiratory inductive plethysmography and pulse oximetry. Arterial line was used for measurement of hemodynamics and blood sampling. Tramadol did not have any clinically significant effects on respiration, breathing pattern, or hemodynamics, but an increase in plasma epinephrine levels was noted. Meperidine bolus decreased tidal volume (p < 0.05, difference from baseline) and pulse oxygen saturation (from 97% to 94%, p < 0.05), but during the succeeding infusion, the respiratory drive, measured as mean inspiratory flow, was enhanced (p < 0.05 difference from baseline), and the respiratory parameters returned to baseline level. No change in hemodynamics was noted, but a significant increase in plasma norepinephrine and epinephrine levels (from 0.9 to 1.6 nmol/L and from 0.3 to 0.8 nmol/L, respectively; p < 0.05) was observed after meperidine administration. Tramadol caused nausea more often than meperidine (p < 0.05, between treatments).

Tramadol exhibited a minimal effect on respiration and breathing pattern in healthy volunteers. The respiratory effects of meperidine bolus were predictable with decreasing tidal volume and pulse oxygen saturation. In contrast, during meperidine infusion, adequate respiration was preserved despite the large amount of meperidine infused.