The cardiovascular effects of a large dose of meperidine (8 mg/kg IV) followed by continued slower infusion of the drug (4 mg/kg/hr) and then addition of increasing concentrations (10 to 70 percent) of N2O or nitrogen during continued meperidine infusion were determined in 18 dogs. Meperidine (8 mg/kg) produced a marked (p<0.01) decrease in stroke volume (SV), cardiac output (T), systemic vascular resistance (SVR), mean arterial blood pressure
mean pulmonary artery pressure
and also reduced (p<0.05) mean right atrial pressure
but did not significantly change heart rate (HR). During continued meperidine infusion, SV, T, and
increased until they became similar to premeperidine controls, while HR increased so that it was higher (p<0.05) than controls.
and SVR also increased during continued meperidine infusion; however, they remained less than control values. Addition of N2O did not significantly change SV or
but produced reductions in HR and T and increases in
and SVR when compared to similar concentrations of nitrogen.
These data demonstrate that rapid infusions of large doses of meperidine produce marked depression in cardiovascular dynamics which recover when the meperidine infusion is slowed. Addition of Na2O during meperidine infusion results in significant reductions in HR and T and increases in
and SVR. Our findings indicate that N2O-meperidine anesthesia tends to preserve systemic blood pressure but at the expense of a reduced T and increased SVR.
Presented in part at the 1976 annual meeting of the American Society of Anesthesiologists in San Francisco, California, October 1976.
© 1977 International Anesthesia Research Society