Pain often accompanies
intravenous injection of 1%
methohexital. The aim of the present study was to test whether
pain on injection could be reduced by dissolving
methohexital in a
lipid emulsion (study A) and whether this would affect
anesthetic potency (study B). In study A, 24 healthy volunteers, 36 +/- 1 yr (mean +/- SE), were given 1 ml 1%
methohexital in saline, 1 ml 1%
methohexital in
lipid emulsion, and 5 ml 0.1%
methohexital in saline in random order. The
injections were given in a small vein in the forearm at 5-min intervals. One minute after each injection, the subject was asked to assess the injection
pain on a visual analog scale (0-100 mm). The
pain score (median [range]) was 44.5 (0-77) after 1%
methohexital in saline, 0.5 (0-26) after 1%
methohexital in a
lipid emulsion, and 1.0 (0-26) after 0.1%
methohexital in saline. The
pain score for 1%
methohexital in saline was significantly greater than those for the other two solutions (P less than 0.001 for each comparison). In study B, 42 patients, 41 +/- 3 yr, were given 1%
methohexital in
lipid emulsion (n = 22) or 1%
methohexital in saline (n = 20). A bolus of either
solution was administered over 10 s, and the patient was considered asleep if there was no gross movement or response to verbal command 40-70 s after injection.(ABSTRACT TRUNCATED AT 250 WORDS)