The Effect of Lidocaine on the Ventilatory Response to Carbon Dioxide

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Abstract
The effect of i.v. lidocaine, both as a bolus and as an infusion, on the ventilatory response to CO2 was determined in humans. Bolus injection of 1.5 mg/kg lidocaine caused a decrease in the slope of the CO2 ventilatory response curve from 2.66 .+-. 0.30 (.hivin.x .+-. SEM [mean .+-. standard error of the mean]) to 1.31 .+-. 0.44 l/min per mm Hg within 90 s; the effect was transient with slope returning to 2.39 .+-. 0.83 l/min per mm Hg 150 s after injection. The transient, subconvulsive lidocaine concentrations present during ventilatory depression (8.9 .+-. 2.0 .mu.g/ml) may be sufficient to desensitize the medullary ventilatory control centers. Lidocaine infusion at the rate of 60 .mu.g/kg per min (serum lidocaine concentrations of 3.5 .+-. 0.2 .mu.g/ml) increased the slope of steady state CO2 response curves from 2.89 .+-. 0.29 to 4.17 .+-. 0.44 l/min per mm Hg (P < 0.05); with discontinuation of the infusion, slope returned to 3.18 .+-. 0.33 l/min per mm Hg (P < 0.05). Apparently, bolus injection of lidocaine transiently can depress ventilatory control. Rapid redistribution of lidocaine makes this a transient phenomenon that can be treated with supplemental O2 if necessary. The increased CO2 sensitivity observed during lidocaine infusion suggests that studies of ventilatory control in patients receiving conduction anesthetics must take into account the direct effect of absorbed anesthetics on ventilatory control.