Epinephrine increases the effectiveness of tetracaine spinal anesthesia

The effect of epinephrine on the need for supplementation of spinal anesthesia produced with hyperbaric tetracaine was assessed in 60 patients undergoing transurethral resection of the prostate. Patients were randomly assigned to receive either 6 mg tetracaine alone (n = 20), 6 mg tetracaine with 0.2 mg epinephrine (n = 20), 10 mg tetracaine alone (n = 10), or 10 mg tetracaine with 0.2 mg epinephrine (n = 10). Observers were blinded to the presence or absence of epinephrine. Sensory level of anesthesia was assessed by pin prick, and surgery did not start until the level reached T10. Anesthesia was considered successful if the patient had no pain at the operative site. The success rate of low-dose tetracaine (6 mg) with epinephrine was 95% compared with 65% in patients receiving low-dose tetracaine alone (P = 0.04). All patients receiving 10 mg had successful anesthesia. Compared with patients receiving 6 mg tetracaine, those given 10 mg had higher dermatomal levels of anesthesia (P = 0.0001) and a higher incidence of nausea (P = 0.04). Thus, epinephrine can increase the effectiveness of low-dose tetracaine.