Clinical and metabolic responses to different types of premedication

Clinical and metabolic responses to three types of premedication were studied in ASA physical status I patients given any one of the following: (a) 0.5 mg of atropine and 50 mg of meperidine given intramuscularly plus an oral placebo tablet (n = 14), (b) 10 mg of oral diazepam and an intramuscular placebo (2 mL NaCl, concentration = 0.9) (n = 14), or (c) oral and intramuscular placebo (n = 14). Based both on subjective estimates (tiredness, fear, anxiety, dryness of mouth) and, especially, on metabolic responses (energy expenditure, oxygen consumption), oral diazepam appears to be superior to the combination of an opiate (meperidine) plus an anticholinergic (atropine). Atropine plus meperidine significantly increased energy expenditure above predicted values (2061 +/- 365 vs 1714 +/- 361 kcal/24 h, P = 0.004), calculated using the Harris-Benedict equation, based on sex, weight, height, and age, as well as increased oxygen consumption above levels seen with diazepam premedication (160 +/- 29 vs 137 +/- 17 mL.min-1. m-2). These findings indicate an iatrogenic stress factor induced by premedication with atropine plus meperidine.