ELEVATION OF END-TIDAL CARBON DIOXIDE TENSION AFTER ORAL MUCOSAL EPINEPHRINE INJECTION MAY BE A USEFUL NONINVASIVE MONITOR FOR CARDIAC OUTPUT IN HUMANS

Abstract

S213 INTRODUCTION: End-tidal carbon dioxide tension(PETCO2: may change by several mechanisms including increase in cardiac output(CO), metabolic rate, and/or physiological deadspace (VD/VT) after epinephrine injection [1]. Further it has been reported that PETCO2 changes are directly correlated with CO changes [2]. In the present study, we sought to determine whether a relationship exists between PETCO2 elevation and CO increase after oral mucosal epinephrine injection. METHODS: Following institutional approval and informed consent, 15 ASA I patients (19-35 yrs) scheduled for orthognathic surgery were studied. Anesthesia was induced with IV propofol (2.5 mg/kg) and fentanyl (2 [micro sign]g/kg), and nasotracheal intubation was facilitated with vecuronium bromide (0.2 mg/kg). Anesthesia was maintained with continuous infusion of propofol (12 mg/kg/hr) and mechanically ventilated (FiO2: 0.3). Before the beginning of surgery, 1% lidocaine solution containing 10 [micro sign]g/ml epinephrine (total dose: 0.5-2.0 [micro sign]g/kg) was injected into the oral mucosa in over two minutes. The following variables were measured plasma epinephrine concentration (high performance liquid chromatography), PETCO2(Capnomac[registered sign]; Datex), PaCO2, PaO2, CO (NCCOM3-R7[registered sign]; CDIC), carbon dioxide output(VCO2), oxygen consumption(VO2) (DELTATRAC[registered sign]; Datex), arterial blood pressure, and heart rate. The operation was started 15 minutes after the completion of epinephrine injection. RESULTS: The maximum increase in plasma epinephrine concentrations were significantly correlated with PETCO2 elevation (r=0.68, p<0.01) and CO increase (r=0.62, p<0.01). Figure 1 shows the time course of the measured variables. Both PETCO2 and CO showed a precipitous increase up to 6 minutes after epinephrine injection. Further, there was a significant correlation between PETCO2 elevation and CO increase (r=0.62, p<0.01, Figure 2).Figure 1Figure 2DISCUSSION: The changes in CO, metabolic rate, and VD/VT may modify PETCO2 and PaCO2. Our results seem to indicate that the increase in metabolic rate caused PETCO2 elevation. PETCO2 elevation and CO increase also did have a significant correlation which occurred concomitantly. The clinical significance is that PETCO2 elevation after oral mucosal epinephrine injection may be a useful noninvasive monitor for CO.