Milrinone modulates endotoxemia, systemic inflammation, and subsequent acute phase response after cardiopulmonary bypass (CPB)

Effects of olprinone, a new phosphodiesterase inhibitor, on gastric intramucosal acidosis and systemic inflammatory responses following hypothermic cardiopulmonary bypass

BACKGROUND

Phosphodiesterase (PDE) III inhibitors have both an inotropic and a peripheral vasodilatory effect, and also inhibit the activation of macrophages. Thus a newly developed PDE III inhibitor, olprinone, could modify gastric intramucosal pH (pHi), systemic oxygen consumption, and systemic inflammatory responses in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB).

METHODS

We studied 23 patients. In 15 patients, olprinone (0.1 or 0.2 microg x kg(-1) x min(-1)) was administered from the commencement of CPB until their admission to the ICU. The other 8 patients received placebo. The pHi and regional CO2 tension (PrCO2) were assessed by a capnometric air tonometry. Systemic inflammatory responses were evaluated by serum interleukin-6 (IL-6), IL-10, and leucocyte counts.

RESULTS

The pHi and PCO2-gap, the difference between PrCO2 and arterial CO2 tension (PaCO2), showed a transient decrease and an increase after CPB, respectively. Although olprinone did not affect pHi, olprinone at 0.2 microg x kg(-1) x min(-1) significantly lessened post-CPB increase in PCO2-gap. Olprinone at 0.2 microg x kg(-1) x min(-1) significantly increased IL-10 and reduced the extent of leucocytosis, while it did not affect IL-6 levels. At the same dosage, olprinone also lessened the surge in systemic oxygen uptake index (VO2) and augmented the increase in mixed oxygen saturation (SvO2) both of which occurred after CPB. At 0.1 microg x kg(-1) x min(-1), however, olprinone did not show any significant effect.

CONCLUSION

Our results suggest that olprinone at 0.2 microg x kg(-1) x min(-1) suppresses gastric intramucosal acidosis and systemic inflammation following CPB.

Effect of low-dose milrinone on gastric intramucosal pH and systemic inflammation after hypothermic cardiopulmonary bypass

OBJECTIVE

To investigate the usefulness of low-dose milrinone on gastric intramucosal pH (pHi) and systemic inflammation in patients undergoing hypothermic cardiopulmonary bypass (CPB).

DESIGN

Prospective randomized study.

SETTING

University hospital.

PARTICIPANTS

Twenty patients scheduled for cardiac surgery.

INTERVENTIONS

Ten patients were administered a low dose of milrinone, 0.25 microg/kg/min, from the initiation of CPB to 1 hour after admission to the intensive care unit. The other patients were administered saline. Supplemental inotropes and intravenous fluid were given to obtain adequate mean arterial blood pressure and pulmonary artery occlusion pressure.

MEASUREMENTS AND RESULTS

Gastric pHi and carbon dioxide pressure (PCO2) were assessed by capnometric air tonometry. The difference between PCO2 and arterial carbon dioxide pressure (PaCO2), PCO2-gap, was also examined. Systemic inflammatory responses were evaluated by serum interleukin-6 and leukocyte counts. Hemodynamics, oxygen delivery index, and oxygen uptake index were monitored with catheters in the radial and pulmonary arteries (thermodilution). The hepatic venous blood flow and left ventricular flow were measured using transesophageal echocardiography. Milrinone prevented gastric intramucosal acidosis, detected as a decrease in pHi or an increase in PCO2-gap, without affecting hepatic venous blood flow. Increases in interleukin-6, leukocyte count, and oxygen uptake index, all of which developed after CPB, were significantly less in the milrinone group than in the control group.

CONCLUSION

These results suggest that in patients undergoing hypothermic CPB, supplemental low-dose milrinone prevents gastric intramucosal acidosis and increases in some markers of systemic inflammation.

Milrinone improves intestinal villus blood flow during endotoxemia

PURPOSE

To determine whether the compromised intestinal villus blood flow in a rat model of endotoxemia could be improved by continuous infusion of the phosphodiesterase (PDE) inhibitor milrinone.

METHODS

Twenty-four anesthetized and ventilated rats were laparotomized and an ileal portion was exteriorized and opened by an antimesenteric incision. The ileal segment was fixed with the mucosal surface upward. Microcirculatory parameters were assessed by intravital videomicroscopy. The animals were randomly assigned to receive one of three treatments: infusion of Escherichia coli lipopolysaccharides without phosphodiesterase inhibitor pretreatment (=LPS group); or infusion of LPS with milrinone pretreatment (= milrinone group), or without infusion of LPS or milrinone (=control group). Macrohemodynamic parameters (MAP, HR) and microhemodynamic parameters of ileal mucosa (mean diameter of central arterioles = D(A) and mean erythrocyte velocity within the arterioles= V(E)) were measured 30 min before and at 0, 60, and 120 min after induction of endotoxemia. Mucosal villus blood flow was calculated from D(A) and V(E).

RESULTS

In the milrinone group MAP decreased 60 min after induction of endotoxemia whereas it remained stable in the control and the LPS group. In both groups given endotoxin V(E) decreased after start of LPS infusion. In contrast, D(A) decreased in the LPS group, but increased in the milrinone group after 120 min of endotoxemia. Thus, the endotoxin-induced decrease of intestinal villus blood flow was diminished but not fully restored by milrinone infusion.

CONCLUSION

Our results indicate that milrinone has some beneficial microcirculatory effects during endotoxemia. Although it contributed to systemic hypotension, it attenuated intestinal mucosal hypoperfusion.