Effects of caudal block with mepivacaine on resting ventilation and ventilatory response to carbon dioxide in sedated children

We examined the effects of caudal anaesthesia using 10 mg.kg-1 of one or two per cent mepivacaine without epinephrine on resting ventilation, arterial blood gas tensions and the ventilatory response to carbon dioxide in 27 sedated children. Expired minute volume and respiratory frequency decreased significantly after the caudal blocks in both groups. PaO2 and PaCO2 remained unchanged in both groups. The slope of the CO2 response curve increased significantly in both groups. The mean plasma mepivacaine levels were 4.6 +/- 1.6 (SD) and 4.6 +/- 1.0 micrograms.ml-1 20 minutes after the caudal blocks with one and two per cent mepivacaine, respectively. These results demonstrate that resting ventilation is impaired but the ventilatory response to carbon dioxide is improved similarly by caudal block with one or two per cent mepivacaine.