The Efficacy of Epinephrine Test Doses During Spinal Anesthesia in Volunteers

Abstract

Epinephrine test doses may be administered during combined spinal-epidural anesthesia to determine intravascular placement of epidural catheters. This study was designed to determine systolic blood pressure (SBP) and heart rate (HR) responses to intravenous injection of epinephrine (15 microg) during spinal anesthesia. Twelve volunteers received three spinal anesthetics (lidocaine 100 mg, tetracaine 15 mg, and bupivacaine 15 mg) in a randomized, double blind, cross-over fashion. Epinephrine was administered prior to spinal anesthesia (control), 30 min after injection of spinal anesthesia, and at regression of sensory block to T-10. SBP was measured with a radial arterial catheter and HR with an electrocardiogram. Positive responses were defined as peak increase in SBP > or = 15 mm Hg or HR > or = 20 bpm after injection of epinephrine. Compared with control, peak SBP responses decreased by a mean of 12 mm Hg during spinal anesthesia with tetracaine and bupivacaine (P < 0.05). Peak HR responses decreased by 11 bpm during all three spinal anesthetics (P < 0.05). Incidences of detection of intravenous injection by positive SBP and HR responses ranged from 50% to 100% and were not significantly affected by spinal anesthesia. Spinal anesthesia reduces hemodynamic responses to intravenous epinephrine injection but is unlikely to reduce detection by positive SBP and HR criteria.

Changes of the T-wave on range of spinal blockade after low dose epinephrine administration

“…This differs from a report showing that spinal anesthesia reduces hemodynamic responses to IV epinephrine injection [12]. However, Liu et al reported that epinephrine injection is unlikely to reduce detection by positive SBP and HR criteria [12]. We believe that this discordance can be explained by methodological variations between these studies.…”

“…The responses to the circulating adrenergic activity may not be affected by spinal block. This differs from a report showing that spinal anesthesia reduces hemodynamic responses to IV epinephrine injection [12]. However, Liu et al reported that epinephrine injection is unlikely to reduce detection by positive SBP and HR criteria [12].…”

“…aging [3], previous administration of -adrenergic blocking drugs [4], the combination of midazolam and fentanyl [5], volatile anesthetics [6], spinal block [12], or high (T5) thoracic epidural anesthesia combined with general anesthesia [14]. It has been reported that the change in T wave amplitude is unaffected by the combination of midazolam and fentanyl [5], sevoflurane anesthesia [9], and the ECG lead monitored [15].…”

The Epidural Test Dose: A Review

“…The amplitude of an epinephrine response is attenuated by the following factors for HR: aging (18), previous administration of ␤-adrenergic blocking drugs (selective or nonselective) (15), the combination of midazolam (arousable by verbal command) and fentanyl (2 g/kg IV) (29), isoflurane (hemodynamic responses to intravascular injection of test doses vary with dose of epinephrine and depth of anesthesia) (30), sevoflurane (2% end-tidal concentration) (20), spinal blockade (31) or high (T 5 ) thoracic epidural anesthesia combined with general anesthesia (32) but not by IV atropine (administered just before the test dose) (33), midazolam alone (29), oral clonidine (24), or low (T 10 ) thoracic epidural anesthesia (32). The increase in SBP is affected by isoflurane (30), spinal (31) or high thoracic (T 5 ) epidural anesthesia (32) but not by aging (18,34), ␤-adrenergic blocking drugs (15), the combination of midazolam and fentanyl (29), oral clonidine (24), sevoflurane (20), or low (T 10 ) thoracic epidural anesthesia (32).…”

“…The increase in SBP is affected by isoflurane (30), spinal (31) or high thoracic (T 5 ) epidural anesthesia (32) but not by aging (18,34), ␤-adrenergic blocking drugs (15), the combination of midazolam and fentanyl (29), oral clonidine (24), sevoflurane (20), or low (T 10 ) thoracic epidural anesthesia (32). The T wave amplitude decrease is not affected by the combination of midazolam and fentanyl (29), sevoflurane anesthesia (21), or the electrocardiogram lead (I, II, III, or V (5)) monitored (35).…”