Plasma concentrations of lidocaine (lignocaine) after cranial subcutaneous injection during neurosurgical operations.

After cranial subcutaneous injection of lidocaine 0.8-3.7 mg/kg+adrenaline (epinephrine) 1:200,000 in neurosurgical patients, fast drug absorption was found with peak plasma concentrations of 0.6-1 microgram/ml in 5-10 min. However, the concentrations remained above the lowest effective antiarrhythmic level of 0.6 microgram/ml for only about 10 min. In one patient, simultaneously administered intravenous lidocaine had an additive effect on those levels. Induced hypotension (sodium nitroprusside) during aneurysm operations decreased the arterial plasma level of lidocaine and was followed by a new peak after discontinuation. Thus the absorption of a drug during induced hypotension from subcutaneous tissue is often erratic.