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Correspondence |
Zagreb, Croatia
To the Editor:
Acute normovolemic hemodilution (ANH) is a widespread practice during coronary artery surgery and numerous studies emphasize the safety of a low transfusion trigger in these patients.1–3 During off-pump coronary artery bypass surgery (OPCAB), periods of hemodynamic instability that require inotropic therapy may occur.4 However, no studies, except experimental, evaluate how hemodilution influences the hemodynamic response to inotropic therapy.5 Our study compared the hemodynamic response to dobutamine in patients with coronary artery disease (CAD) at two different levels of ANH.
After Ethical Board approval, 40 patients with CAD scheduled for OPCAB surgery were randomized to two groups after induction of anesthesia. Anesthesia was induced with midazolam (0.2 mg•kg–1), fentanyl (5 µg•kg–1), pancuronium-bromide (1 mg•kg–1) and maintained by halothane (concentrations up to 0.5%), fentanyl (in total up to 15 µg•kg–1) and pancuronium-bromide (bolus of 0.25 mg•kg–1). All patients were monitored with pulmonary artery and arterial catheters, 5-lead electrocardiogram, pulse oximeter, capnography and transesophageal echocardiography.
In the moderate group ANH was performed up to hemoglobin values of 95 to 105 g•L–1 and, in the severe group, up to hemoglobin values of 75 to 85 g•L–1. Calculated blood volume to obtain the required level of ANH was replaced with the same volume of 6% hydroxyethylstarch. After ANH, both groups were treated with dobutamine 5 µg•kg–1•min–1 for 15 min. Hemodynamic and oxygenation variables were measured using the thermodilution method after induction, 15 min after ANH and 15 min after starting the dobutamine infusion. Nonparametric tests were used for statistical analysis due to the small number of patients.
In the moderate ANH group, dobutamine infusion was associated with a significant increase in cardiac index (CI; 2.7 ± 1.1 vs 3.3 ± 1.1 L•min–1•m–2, P < 0.01) and oxygen delivery (DO2; 391 ± 132 vs 444 ± 96 mL•min–1•m–2, P < 0.05), while in the severe ANH group, CI and DO2 did not change significantly after the administration of dobutamine (Table
). Thus, dobutamine could not increase CI to compensate the reduced DO2 after severe ANH while the moderate ANH group had favourable hemodynamic and oxygenation variables (Table).
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References
1 Spahn DR, Casutt M. Eliminating blood transfusion: new aspects and perspectives. Anesthesiology 2000; 93: 242–55.[Medline]
2 Hebert PC, Yetisir E, Martin C, et al. Is a low transfusion threshold safe in critically ill patients with cardiovascular disease? Crit Care Med 2001; 29: 227–34.[Medline]
3 Bracey AW, Radovancevic R, Riggs SA, et al. Lowering the hemoglobin threshold for transfusion in coronary artery bypass procedures: effect on patient outcome. Transfusion 1999; 39: 1070–7.[Medline]
4 Couture P, Denault A, Limoges P, Sheridan P, Babin D, Cartier R. Mechanisms of hemodynamic changes during off-pump coronary artery bypass surgery. Can J Anesth 2002; 49: 835–49.
5 Shinoda T, Mekhail NA, Estefanous FG, Smith C, Khairallah PA. Hemodynamic responses to dobutamine during acute normovolemic hemodilution. J Cardiothorac Vasc Anesth 1994; 8: 545–51.[Medline]
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  P. Van der Linden and S. De Hert Normovolemic hemodilution and the heart/Le coeur et l'hemodilution normovolemique Can J Anesth, February 1, 2005; 52(2): 130 - 132. [Full Text] [PDF]
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