Systemic atropine administration during cardiac arrest does not cause fixed and dilated pupils. OBJECTIVES: Systemic administration of atropine during CPR may postpone brain death determination because of its reputed ability to produce fixed and dilated pupils. We studied the effect of atropine administered in the usual doses as an adjunct to endotracheal intubation and for cardiac arrest to determine if it would interfere with neurological assessment. DESIGN: Two groups of children were studied. Group 1 consisted of 28 patients who received atropine (0.03 +/- 0.003 mg/kg) prior to endotracheal intubation. Group 2 consisted of 21 patients previously without evidence of brainstem disease who suffered a witnessed arrest and had prompt return of spontaneous circulation and received an atropine dose of 0.03 +/- 0.01 mg/kg. RESULTS: In group 1, pupillary size averaged 4.02 +/- 0.78 mm before and 4.75 mm +/- .84 mm after atropine (P less than .001). In group 2, the pupillary examination was conducted 30 minutes after return of spontaneous circulation. The pupillary diameter was 4.80 +/- 0.91 mm. All pupils were reactive to light in both groups. CONCLUSION: Atropine administration in conventional dose causes slight pupillary dilation but does not abolish pupillary light reactivity. 