The effects of iv succinylcholine (SCh) on the electroencephalogram (EEG), cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), intracranial pressure (ICP), central venous pressure (CVP), and mean arterial pressure (MAP) were tested in halothane-anesthetized dogs. Six dogs were maintained at 0.87 +/- 0.00% (mean +/- SE) expired halothane (1.0 MAC) and received both SCh 1.0 mg X kg-1 and lactated Ringer's solution placebo 0.05 ml X kg-1. Fasciculations began 24 +/- 4 s after iv SCh. Fasciculations were followed by immediate EEG arousal in five of six dogs and increases in CBF in all six. Average CBF was 151 +/- 14% of control for the 0-15 min measurement period and 127 +/- 7% of control for the 15-30 min period. Both were significantly greater than pre-SCh control values and placebo group values. Peak CBF of 177 +/- 19% of control occurred 3 min after iv SCh and was accompanied by a peak ICP of 435 +/- 131% of control. ICP values were significantly different between SCh and placebo treatments only during the periods of greatest CBF (1 to 5 min after iv SCh). Average PaCO2 values after iv SCh were significantly greater than pre-SCh control values and placebo values during each 15-min measurement interval. Average PaCO2 was 116 +/- 2% of control during the 0-15 min measurement period, 114 +/- 2% of control during the 15-30 min period, and 109 +/- 1% of control during the 30-45 min period. CVP, MAP, and CMRO2 did not significantly change after iv SCh.(ABSTRACT TRUNCATED AT 250 WORDS)