Plasma catecholamine response to tracheal intubation after midazolam and vecuronium in elderly patients with hypertension

This study was undertaken to determine whether midazolam alleviates sympathoadrenal response evoked by tracheal intubation in elderly patients with hypertension. Anesthesia was induced with midazolam in a sleep dose followed by vecuronium 0.1 mg.kg-1. Heart rate and blood pressure were recorded before, 1 and 3 minutes after induction with intubation. Free and total catecholamine (CA) in plasma were measured at each time. Dopamine, norepinephrine and epinephrine (EN) were determined using fluorescence derivatization with diphenylethylenediamine by HPLC. Although heart rate and diastolic pressure rose in some degree 1 min after intubation, free and total CA concentrations did not increase during study period. Free and total EN levels decreased significantly 3 min after intubation. The absence of elevation in plasma CA concentrations, especially in free CA, which is physiologically active, would contribute to produce circulatory stability on laryngoscopy and tracheal intubation. However, the mystery of why hyperdynamic state was produced without the increase in CA concentrations remains to be solved, even though it occurred for a short period of time.