Comparação dos efeitos da dobutamina e da milrinona sobre a hemodinâmica e o transporte de oxigênio em pacientes submetidos à cirurgia cardíaca com baixo débito cardíaco após indução anestésica / Comparison of the effects of dobutamine and milrinone on hemodynamic parameters and oxygen supply in patients undergoing cardiac surgery with low cardiac output after anesthetic induction

JUSTIFICATIVA E OBJETIVOS: Diversas classes de fármacos inotrópicos, com efeitos hemodinâmicos diferentes, são utilizadas no tratamento do baixo débito cardíaco em pacientes com disfunção sistólica submetidos a procedimento cirúrgico cardíaco. O objetivo deste estudo foi comparar o efeito da dobutamina e da milrinona sobre a hemodinâmica e o transporte de oxigênio nessa população de pacientes. MÉTODO: Após aprovação do Comitê de Ética institucional e obtenção do consentimento escrito pós-informado, 20 pacientes submetidos à cirurgia cardíaca e com índice cardíaco < 2 L.min-1.m-2 pós-indução anestésica e instalação de cateter de artéria pulmonar foram distribuídos aleatoriamente para receber dobutamina 5 µg.kg-1.min-1 (n = 10) ou milrinona 0,5 µg.kg-1.min-1 (n = 10). Medidas hemodinâmicas foram obtidas pós-indução, 30 e 60 minutos após, e gasometrias arterial e venosa nos momentos basal e 60 minutos. Os dados foram comparados usando teste t de Student não pareado ou ANOVA de duas vias para medidas repetidas. RESULTADOS: A dobutamina e a milrinona promoveram aumentos significativos no índice cardíaco (56 por cento e 47 por cento) e no transporte de oxigênio (53 por cento e 45 por cento), redução nos índices de resistência vascular sistêmica (33 por cento e 36 por cento) e pulmonar (34 por cento e 19 por cento), respectivamente. Contudo, não foram observadas diferenças entre os fármacos. CONCLUSÕES: Ambos os fármacos inotrópicos foram igualmente efetivos em restaurar o fluxo tecidual sanguíneo e a oferta tecidual de oxigênio para valores adequados em pacientes com baixo débito cardíaco submetidos à cirurgia cardíaca.

BACKGROUND AND OBJECTIVES: Several classes of inotropic drugs with different hemodynamic effects are used in the treatment of low cardiac output in patients with diastolic dysfunction undergoing cardiac surgery. The objective of the present study was to compare the effects of dobutamine and milrinone on hemodynamic parameters and oxygen supply in this population of patients. METHODS: After approval by the Ethics Committee of the institution and signing of the informed consent, 20 patients undergoing cardiac surgery with cardiac index < 2 L.min-1.m2 after anesthetic induction and place ment of a pulmonary artery catheter were randomly divided to receive dobutamine 5 µg.kg-1. min-1 (n = 10), or milrinone 0.5 µg.kg-1.min-1 (n = 10). Hemodynamic parameters were measured after anesthetic induction and after 30 and 60 minutes, and arterial and venous blood gases were measured at baseline and 60 minutes. Non-paired Student t test or two-way ANOVA for repeated measurements was used to compare the data. RESULTS: Dobutamine and milrinone promoted significant increases in cardiac index (56 percent and 47 percent) and oxygen supply (53 percent and 45 percent), and reduction in systemic (33 percent and 36 percent) and pulmonary (34 percent and 19 percent) vascular resistance, respectively. However, statistically significant differences were not observed between both drugs. CONCLUSIONS: Both inotropic drugs were similarly effective in restoring tissue blood flow and oxygen supply to adequate levels in patients with low cardiac output undergoing cardiac surgery.

JUSTIFICATIVA Y OBJETIVOS: Diversas clases de fármacos inotrópicos con efectos hemodinámicos diferentes, se usan en el tratamiento del bajo débito cardíaco en pacientes con disfunción sistólica sometidos al procedimiento quirúrgico cardíaco. El objetivo de este estudio, fue comparar el efecto de la dobutamina y de la milrinona sobre la hemodinámica y el transporte de oxígeno en esa población de pacientes. MÉTODO: Después de la aprobación del Comité de Ética institucional y de la obtención del consentimiento informado, 20 pacientes sometidos a la cirugía cardíaca y con índice cardíaco < 2 L.min-1.m-2 postinducción anestésica e instalación de catéter de arteria pulmonar, fueron distribuidos aleatoriamente para recibir dobutamina 5 µg.kg-1. min-1 (n = 10) o milrinona 0,5 µg.kg-1.min-1 (n = 10). Medidas hemodinámicas se obtuvieron postinducción, entre 30 y 60 minutos después de las gasometrías arterial y venosa en los momentos basales y 60 minutos. Los datos se compararon usando el test t de Student no pareado o Anova de dos vías para medidas repetidas. RESULTADOS: La dobutamina y la milrinona produjeron aumentos significativos en el índice cardíaco (56 por ciento y 47 por ciento) y en el transporte de oxígeno (53 por ciento y 45 por ciento), una reducción en los índices de resistencia vascular sistémica (33 por ciento y 36 por ciento) y pulmonar (34 por ciento y 19 por ciento) respectivamente. Sin embargo, no fueron observadas diferencias entre los fármacos. CONCLUSIONES: Ambos fármacos inotrópicos fueron igualmente efectivos en la restauración del flujo tisular sanguíneo y en la oferta tisular de oxígeno para valores adecuados en pacientes con bajo débito cardíaco sometidos a la cirugía cardíaca.

Treating metabolic impairment and myocardial stunning with phosphodiesterase inhibitor type III, milrinone, administered prior to coronary artery occlusion in the presence of calcium channel blockade in pigs.

This study examined milrinone effects on ischaemic myocardial metabolism and function with calcium blockade. We studied 15 pigs in 3 groups: group C received no drugs; group D received diltiazem 5 mg bolus followed by infusion; group D+M received diltiazem and milrinone (50microg/Kg). The left anterior descending (LAD) artery was then occluded for 15 minutes. Left ventricular (LV) function data obtained included rate, pressures, output, Emax, and dP/dT. Blood lactate was obtained from the LAD and circumflex vessels at baseline, end of occlusion, early (15 min) and late (1 hour) reperfusion. In group D+M, less depression of LV function occurred during ischaemia and early reperfusion. Lactate extraction in the LAD region was less negative in D+M group than in the group without milrinone during ischaemia and late reperfusion. We conclude the preemptive administration of milrinone prior to ischaemia added to calcium blockade improved myocardialfunction and ischaemic metabolic effects.

The Effect of Milrinone on the Right Ventriclular Function in Patients with Reduced Right Ventricular Function Undergoing Off-pump Coronary Artery Bypass Graft Surgery

This investigation evaluated the effect of continuous milrinone infusion on right ventriclular (RV) function during off-pump coronary artery bypass graft (OPCAB) surgery in patients with reduced RV function. Fifty patients scheduled for OPCAB, with thermodilution RV ejection fraction (RVEF) <35% after anesthesia induction, were randomly allocated to either milrinone (0.5 microgram/kg/min) or control (saline) group. Hemodynamic variables and RV volumetric data measured by thermodilution method were collected as follows: after anesthesia induction (T1); 10 min after heart displacement for obtuse marginal artery anastomosis (T2); after pericardial closure (T3). Cardiac index and heart rate increased and systemic vascular resistance significantly decreased in milrinone group at T2. Initially lower RVEF of milrinone group was eventually comparable to control group after milrinone infusion. RVEF did not significantly change at T2 and T3 in both groups. RV end-diastolic volume in milrinone group consistently decreased from the baseline at T2 and T3. Continuous infusion of milrinone without a bolus demonstrated potentially beneficial effect on cardiac output and RV afterload in patients with reduced RV function during OPCAB. However, aggressive augmentation of intravascular volume seems to be necessary to maximize the effect of the milrinone in these patients.