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Correspondence |
Sakuragaoka, Japan
To the Editor:
It has been suggested that a left SGB is not associated with hemodynamic alterations, whereas a right SGB significantly alters hemodynamics. Yet, clinical studies evaluating the hemodynamic effects of unilateral right and left stellate ganglion block (SGB) in humans are lacking. The thermodilution technique is the most accepted clinical method to estimate cardiac output, but a pulmonary artery catheter is required for as long as cardiac output monitoring is needed. The Portapres Model-2 (TNO Biomedical Instrumentation, Amsterdam, The Netherlands) is a continuous non-invasive hemodynamic monitor. Stroke volume is calculated by the Modelflow method that estimates beat-to-beat cardiac output from the arterial pressure wave by simulating a non-linear three-element model of aortic input impedance.1,2 The tracking of changes in cardiac output is precise.3,4 We investigated the real time changes in hemodynamic variables after SGB in patients free of cardiovascular disease.
The study group comprised 21 patients with peripheral facial palsy. A right SGB was induced in ten patients and a left SGB in 11 patients. Hemodynamic variables included blood pressure, stroke volume, cardiac output, heart rate and total peripheral resistance. After the subject had rested in the supine position for ten minutes, left or right SGB was induced with 6 mL of 1% mepivacaine hydrochloride using the paratracheal anterior technique with the needle aimed at the transverse process of the sixth cervical vertebra. Hemodynamic variables were measured for 30 min after SGB.
SGB was successful in all patients. Stroke volume and cardiac output increased slightly but not significantly after left SGB. The average systolic blood pressure decreased by 13.6 mmHg 10–20 min after right SGB and the average mean blood pressure decreased by 6.9 mmHg 15 min after the block. The average stroke volume and cardiac output decreased by 9.4 mL and 0.790 L•min–1 respectively five to 30 min after the block (Figure
). As a result, the total peripheral resistance increased at ten minutes and at 20–30 min after the block. The heart rate decreased slightly but the difference was not statistically significant.
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References
1 Toorop GP, Westerhof N, Elzinga G. Beat-to-beat estimation of peripheral resistance and arterial compliance during pressure transients. Am J Physiol 1987; 252: H1275–83.
2 Jellema WT, Wesseling KH, Groeneveld ABJ, Stoutenbeek CP, Thijs LG, van Lieshout JJ. Continuous cardiac output in septic shock by simulating a model of the aortic input impedance: a comparison with bolus injection thermodilution. Anesthesiology 1999; 90: 1317–28.[Medline]
3 Wesseling KH, Jansen JR, Settels JJ, Schreuder JJ. Computation of aortic flow from pressure in humans using a nonlinear, three-element model. J Appl Physiol 1993; 74: 2566–73.
4 Schreuder JJ, van der Veen FH, van der Velde ET, et al. Beat-to beat analysis of left ventricular pressure-volume relation and stroke volume by conductance catheter and aortic Modelflow in cardiomyoplasty patients. Circulation 1995; 91: 2010–7.
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P < 0.05 right vs left SGB as assessed by unpaired t test.