Lighter general Anesthesia causes less decrease in arterial pressure induced by epinephrine scalp infiltration during neurosurgery

Scalp infiltration with epinephrine-containing lidocaine solution can elicit significant hypotension before craniotomy under general anesthesia.. A prospective randomized controlled study was designed to observe whether a lighter depth of general anesthesia could prevent the unintentional hypotension induced by the epinephrine scalp infiltration during neurosurgery or not. Fifty patients undergoing scheduled neurosurgery involving craniotomy were randomly allocated into 2 groups. After anesthesia induction, anesthesia was maintained with propofol 2 mu g/mL and rimifentanil 2 ng/mL by target-controlled infusion in group 1, and propofol 4 mu g/mL and rimifentanil 4 ng/mL in group 2 (control group), respectively. All the patients received epinephrine scalp infiltration with 1% lidocaine 16mL containing epinephrine 5 mu g/mL. Mean arterial pressure (MAP) and heart rate were recorded at 30-second interval from the baseline to 5 minutes after the beginning of local infiltration. Bispectral index readings indicated group I had the lighter general anesthesia than group 2 (P < 0.05). MAP was higher (P < 0.05) and heart rate was lower (P < 0.05) at 1.5 minutes time point in group I than group 2. The mean percentage of maximal decrease in MAP was group 1 (13%) < group 2 (24%) (P < 0.05). The mean percentage of maximal increase in MAP was group 1 (10%) > group 2 (4%) without significant difference (P > 0.05). The results implied that keeping a lighter general anesthesia caused less decrease in arterial blood pressure and was a relative effective method to prevent hypotension episode induced by epinephrine scalp infiltration.