THE HEMODYNAMIC-RESPONSES TO AN INTRAVENOUS TEST DOSE IN VASCULAR SURGICAL PATIENTS

The study was designed to investigate the hemodynamic responses to int ravenous (IV) injections of various epidural test doses in vascular su rgical patients to determine whether previously established criteria i n healthier populations were valid in this inherently sicker populatio n. A double-blind, prospective randomized study was performed on 50 pa tients, not receiving beta-adrenergic antagonists, presenting for vasc ular surgery and requiring an arterial line. Patients were randomly as signed to receive a 3-mL injection of one of five solutions, either sa line (Group 1), lidocaine 45 mg (Group 2), Lidocaine 45 mg and epineph rine 5 mu g (Group 3), lidocaine 45 mg and epinephrine 10 mu g (Group 4), or lidocaine 45 mg and epinephrine 15 mu g (Group 5). After inject ion, a blinded observer recorded arterial blood pressure and heart rat e (HR) every 15 s for 3 min. The changes in HR, systolic (SBP), mean ( MBP), and diastolic (DBP) blood pressure as well as time to maximum ch ange were analyzed both within and between groups. Only Group 5 had si gnificant within-group changes for all hemodynamic variables measured. Only in the comparison between Groups 1 and 5 and between Groups 2 an d 5 were there significant changes in both HR and SBP. The mean increa se in HR and SBP within Group 5 was 17.0 +/- 5.9 bpm and 31.0 +/- 10.5 mm Hg, respectively. No differences were found between groups for tim e to maximum change for HR and SEP which for Group 5 were 64.5 +/- 37. 4 s and 90.0 +/- 56.7 s, respectively. To achieve 100% sensitivity and specificity for HR increase, the criterion established was greater th an or equal to 9 bpm. A criterion with 100% sensitivity and specificit y could not be established for SBP. The authors conclude that a test d ose containing epinephrine 15 mu g is a reliable test dose for identif ication of intravascular injection in the vascular surgical population when associated with an increase in HR of greater than or equal to 9 bpm. This criterion for HR increase is less than that previously estab lished in healthier populations.