Hemodynamic response to moderate dobutamine dose in OPCAB during acute normovolemic hemodilution

Abstract

Hemodynamic response to moderate dobutamine dose in OPCAB during acute normovolemic hemodilutionTo 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][2][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 ). 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 (DO 2 ; 391 ± 132 vs 444 ± 96 mL·min -1 ·m -2 , P < 0.05), while in the severe ANH group, CI and DO 2 did not change significantly after the administration of dobutamine (Table). Thus, dobutamine could not increase CI to compensate the reduced DO 2 after severe ANH while the moderate ANH group had favourable hemodynamic and oxygenation variables (Table).In conclusion, hemodynamic response to dobutamine is significantly better in moderate compared to severe ANH. Our results suggest OPCAB surgery patients should have hemoglobin values of 100 g·L -1 during ANH. These preliminary results should be evaluated in further studies. Data presented with mean ± standard deviation. ANH = acute normovolemic hemodilution; CI = cardiac index; DO 2 I = oxygen delivery index; VO 2 I = oxygen consumption index; O 2 ER = oxygen extraction rate; HGB = hemoglobin. *Significance within groups in comparison with previous measurement P < 0.05; **significance within groups in comparison with previous measurement P < 0.01; †significance between groups P < 0.05; ‡significance between groups P < 0.01. Perhaps one reason for lack of use of awake fibreoptic intubation is a lack of training or confidence on the part o...

Acute Normovolemic Hemodilution in Cardiac Surgery

“…11 However, any increase in myocardial O 2 demand in these conditions could be associated with the development of myocardial ischemia and cardiac dysfunction. Tonkovic et al 38 recently assessed before surgery the hemodynamic response to moderate dobutamine doses in hemodiluted CAD patients scheduled for off-pump surgery. Patients were hemodiluted to a target hemoglobin concentration of either 9.5 to 10.5 g/dL (moderate ANH) or 7.5 to 8.5 g/dL (severe ANH).…”

Normovolemic hemodilution and the heart

“…12 Dans le présent numéro, Tonkovic et coll. 13 ont évalué la réponse hémodynamique à des doses modérées de dobutamine chez des patients devant subir une opération de pontages coronaire à coeur battant. Les patients étaient sous hémodilution selon un taux cible de 95 à 105 g•L -1 [hémodilution normovolémique aiguë modérée (HNA)] ou de 75 à 85 g•L -1 (HNA sévère).…”

“…Cardiovascular disease patients with a lower preoperative hematocrit have an increased risk of death when compared to non-cardiovascular disease patients with the same preoperative hematocrit. 12 In the present issue, Tonkovic et al 13 evaluated the hemodynamic response to moderate dobutamine doses in hemodiluted coronary artery disease patients scheduled for off-pump surgery. Patients were hemodiluted to a target hemoglobin of either 95 to 105 g•L -1 [moderate acute normovelemic hemodilution (ANH)] or 75 to 85 g•L -1 (severe ANH).…”

Effects of moderate acute isovolaemic haemodilution on myocardial function in patients undergoing coronary surgery under volatile inhalational anaesthesia

“…As heart rate is a major determinant of the myocardial oxygen balance, tolerance to acute isovolaemic haemodilution may closely depend on the heart rate [1]. Several studies in volunteers and patients have indeed demonstrated that increased heart rate was associated with a decreased tolerance of the heart to haemodilution [2–4].…”