• M Tanaka.
• Department of Anesthesia/Critical Care Medicine, Tsuchiura Kyodo General Hospital, Ibaraki, Japan.
• Anesth. Analg. 1996 May 1;82(5):1056-9.

AbstractEpidural test doses containing more than 15 micrograms epinephrine are reliable for the detection of intravascular injection based on the conventional systolic blood pressure (SBP) criterion (positive if > or = 15 mm Hg increase) but not on the heart rate (HR) criterion (positive if > or = 20 bpm increase) in adult patients anesthetized with isoflurane. The present study was designed to test whether isoproterenol could be used as a reliable marker. Thirty adult patients were randomly assigned to one of two groups, each of which was anesthetized with 1% end-tidal isoflurane and nitrous oxide after endotracheal intubation. Isoproterenol group (n = 15) was given 3 mL of 1.5% lidocaine with 3 micrograms isoproterenol intravenously (i.v.) to simulate an i.v. administered test dose. The saline group (n = 15) was identical to the isoproterenol group but received 3 mL of normal saline. HR and arterial blood pressure were measured at 20-s intervals for 4 min after i.v. injection. Mean HR in the isoproterenol group was significantly higher than in the saline group from 40 to 240 s after i.v. test dose with a mean maximum HR increase of 32 +/- 7 bpm (mean +/- SD) occurring at 68 +/- 19 s. All 15 patients in the isoproterenol group developed HR increases > or = 20 bpm (sensitivity 100%). Since HR was essentially unchanged in the saline group, specificity and positive and negative predictive values were all 100%. On the other hand, 12 of 15 patients in the isoproterenol group and none in the saline group exhibited SBP increases > or = 15 mm Hg, resulting in 80% sensitivity and 83% negative predictive value. In the isoproterenol group, however, transient systolic hypotension ( < 80% of the preinjection value) occurred in five patients without untoward clinical sequelae. These results indicate that, based on the peak HR response, the epidural test dose containing 3 micrograms isoproterenol is a reliable marker for intravascular injection in adult patients during isoflurane anesthesia.

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