Postcardiopulmonary bypass lung edema. A preventable complication?

Is crystalloid cardioplegia a strong predictor of intra-operative hemodilution?

INTRODUCTION

Complications due to hemodilution (hematocrit value less than 22%) after cardiopulmonary bypass inevitably resulted with significantly greater intensive care requirements, long hospital stays, more operative costs, and increased mortality rates. We tried to identify whether crystalloid cardioplegia is the strongest predictor of intraoperative hemodilution or not.

MATERIALS AND METHODS

One hundred patients were included into this randomized prospective study. Patients were divided into the two groups. Crystalloid cardioplegia were given to the odd-numbered patients (Group 1, n=50 patients) and blood cardioplegia were given to the even-numbered patients (Group 2, n=50 patients). St. Thomas-II solution was used in Group-1 and Calafiore cold blood cardioplegia was in Group-2.

RESULTS

Average intraoperative hematocrit value was 18.4% ± 2.3 in crystalloid group 24.2% ± 3.4 in blood cardioplegia group (p<0.001). The lowest hematocrit value was 15% and 20% in two groups respectively (p<0.001). In crystalloid group average intraoperative packed red blood cell (RBC) transfusion was 2.3 ± 0.41 units, 0.7 ± 0.6 units blood cardioplegia group (p=0.001). Average transfused RBC was 2.7 ± 0.8 units in crystalloid group, 0.9 ± 0.4 units blood cardioplegia group (p<0.001). Multivariate analyses confirmed age (p = 0.005, OR = 3.78), female gender (p = 0.003, OR = 2.91), longer cross-clamp time (>60 minutes) (p = 0.001, OD = 0.97), body surface area <1.6 m2 (p = 0.001, OR = 6.01) and crystalloid cardioplegia (p < 0.001, OR = 0.19) as predictor of intraoperative hemodilution.

CONCLUSION

Crystalloid cardioplegia, compared to blood cardioplegia not only causes much more intra-operative hemodilution but also increases the blood transfusion requirement. Hemodilution and increased transfusion increases the intensive care unit and hospital stay, in the early postoperative period.

Cardiorespiratory effects of venous lipid micro embolization in an experimental model of mediastinal shed blood reinfusion

BACKGROUND

Retransfusion of the patient's own blood during surgery is used to reduce the need for allogenic blood transfusion. It has however been found that this blood contains lipid particles, which form emboli in different organs if the blood is retransfused on the arterial side. In this study, we tested whether retransfusion of blood containing lipid micro-particles on the venous side in a porcine model will give hemodynamic effects.

METHODS

Seven adult pigs were used. A shed blood surrogate containing 400 ml diluted blood and 5 ml radioactive triolein was produced to generate a lipid embolic load. The shed blood surrogate was rapidly (<2 minutes) retransfused from a transfusion bag to the right atrium under general anesthesia. The animals' arterial, pulmonary, right and left atrial pressure were monitored, together with cardiac output and deadspace. At the end of the experiment, an increase in cardiac output and pulmonary pressure was pharmacologically induced to try to flush out lipid particles from the lungs.

RESULTS

A more than 30-fold increase in pulmonary vascular resistance was observed, with subsequent increase in pulmonary artery pressure, and decrease in cardiac output and arterial pressure. This response was transient, but was followed by a smaller, persistent increase in pulmonary vascular resistance. Only a small portion of the infused triolein passed the lungs, and only a small fraction could be recirculated by increasing cardiac output and pulmonary pressure.

CONCLUSION

Infusion of blood containing lipid micro-emboli on the venous side leads to acute, severe hemodynamic responses that can be life threatening. Lipid particles will be trapped in the lungs, leading to persistent effects on the pulmonary vascular resistance.

Does cold blood cardioplegia solution cause deterioration in clinical pulmonary function following coronary artery bypass graft surgery?

OBJECTIVE

Deterioration in pulmonary function is a common complication following coronary artery bypass graft surgery and there is still speculation to the precise causative factors thereof. Cardioplegia solution not drained by the atriocaval cannula enters the lung parenchyma unless removed by a pulmonary artery (PA) vent. The hypothesis of the present study was that cold blood cardioplegia solution damages the lung parenchyma, resulting in an observed deterioration of clinical lung function.

METHODS

A prospective, double-blind, randomised trial was conducted on 142 patients. The study group of 71 patients had a PA vent inserted at the time of cannulation, preventing cardioplegia from going through the lungs. In addition, positive end expiratory pressure (PEEP) was applied and low-volume lung ventilation carried out during cardiopulmonary bypass (CPB). The control group (n =71) had cardioplegia enter the lung parenchyma during cardiopulmonary bypass. Clinical parameters of arterial blood gases, including estimated shunt fraction, spirometry tests and radiographic analysis was made preoperatively and at set times through the postoperative period.

RESULTS

Baseline demographics and intraoperative and postoperative management was the same in both groups, thus, yielding a homogenous sample for analysis. Significant changes were noted in arterial blood gases, spirometry, and radiographic analysis of effusion and atelectasis over the time periods studied (p<0.001). There was, however, no significant difference between the study and control groups at any point (p > 0.05).

CONCLUSIONS

The data, therefore, suggest that allowing cold blood cardioplegia solution to circulate the lungs during cardiopulmonary bypass does not have any (beneficial or detrimental) effect on clinical lung function postoperatively.

Early continuous venovenous hemodialysis in dialysis-dependent patients after cardiac surgery: safety and efficacy

OBJECTIVES

The present study assessed the safety and efficacy of continuous venovenous hemodialysis (CVVHD) early after cardiac surgery.

DESIGN

Retrospective database and medical record review.

SETTING

University teaching hospital.

PARTICIPANTS

Forty-five dialysis-dependent patients who underwent cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

CVVHD was begun postoperatively after confirmation of hemostasis, irrespective of circulatory status. In the last 5 patients, the ratio of extravascular lung water (EVLW) to intrathoracic blood volume (ITBV) was measured using a single-indicator thermodilution catheter and compared with patients of normal renal function undergoing cardiac surgery.

MEASUREMENTS AND MAIN RESULTS

CVVHD was started at 4 hours after ICU admission. The maximum decrease in blood pressure within 60 minutes after initiation of CVVHD was 11 +/- 9 mmHg in the unstable hemodynamics group (defined as patients who required continuous intravenous adrenaline or intra-aortic balloon pump on admission to the ICU [n = 15]) and 7 +/- 8 mmHg in the stable hemodynamics group (n = 30, not significant). Circulatory status and oxygenation improved significantly 12 hours after CVVHD initiation in the unstable hemodynamics group. Blood volume from the chest tube did not increase after CVVHD. Early mortality (2.2%) was lower than that reported previously. The EVLW/ITBV ratio after ICU admission in dialysis-dependent patients was significantly higher than in patients with normal renal function.

CONCLUSIONS

Early CVVHD after cardiac surgery in dialysis-dependent patients was safe and effective. There was no associated increased postoperative bleeding or hemodynamic instability. Fluid removal improved respiratory status, particularly in patients requiring circulatory assistance, and overall early morality rates were lower that those previously published.

Pulmonary abnormalities after cardiac surgery are better explained by atelectasis than by increased permeability oedema

BACKGROUND

Cardiac surgery can be complicated by pulmonary abnormalities, but it is unclear how various manifestations interrelate.

METHODS

A prospective study in the intensive care unit was performed on 26 mechanically ventilated patients without cardiac failure within 3 h after elective cardiac surgery involving cardiopulmonary bypass. Oedema (extravascular lung water, EVLW) was measured by the thermal-dye technique and permeability by a dual radionuclide technique, yielding a pulmonary leak index (PLI). Radiographic, mechanical and gas exchange features were used to calculate the lung injury score (LIS), ranging between 0 and 4. Evidence for left lower lobe atelectasis was obtained from plain radiographs. The plasma colloid osmotic pressure (COP) was measured by an oncometer.

RESULTS

The EVLW (normal, <7 ml/kg) was elevated in 36% of patients and the PLI (normal, <14.1 x 10(-3)/min) in 44%, but the variables did not interrelate directly. Patients with a supranormal EVLW had a lower COP than patients with normal EVLW. The duration of mechanical ventilation was prolonged in patients (20%) with EVLW > 10 ml/kg. There was no difference in EVLW and PLI in patients with LIS < 1 and LIS > 1 (31% of patients). In patients with radiographic evidence for atelectasis (46%), the positive end-expiratory pressure and inspiratory O2 fraction to maintain oxygenation were higher than in those without.

CONCLUSIONS

After cardiac surgery, mild pulmonary oedema is relatively common, even in the absence of high filling pressures, and is mainly attributable to a low COP, irrespective of increased permeability in about one-half of patients. It may prolong mechanical ventilation at EVLW > 10 ml/kg. However, pulmonary radiographic and ventilatory abnormalities may result, at least in part, from atelectasis rather than increased permeability oedema.

Intrapulmonary shunt after cardiopulmonary bypass: the use of vital capacity maneuvers versus off-pump coronary artery bypass grafting

OBJECTIVES

It has been proved in human subjects and animals that atelectasis is a major cause of intrapulmonary shunting and hypoxemia after cardiopulmonary bypass. Animal studies suggest that shunting can be prevented entirely by a total vital capacity maneuver performed before termination of bypass. This study aimed to test this theory in human subjects and to evaluate possible advantages of off-pump coronary artery bypass grafting.

METHODS

Twenty-four patients scheduled for coronary artery bypass grafting were randomly assigned to receive no total vital capacity maneuver (control group, n = 12) or standard total vital capacity maneuvers (TVCM group, n = 12). Additionally, 12 consecutive patients undergoing off-pump coronary artery bypass grafting (off-pump group) were studied. Systemic and central hemodynamics, the pattern of breathing, and ventilatory mechanics were evaluated after induction of anesthesia, after sternotomy, after cardiopulmonary bypass and skin closure, and 4 hours after extubation.

RESULTS

The use of total vital capacity maneuvers reduced (P <.05) intrapulmonary shunting after termination of cardiopulmonary bypass. However, shunting increased (P <.05) in all groups (control group, 8.2% +/- 3.3% vs 25.6% +/- 8.1%; TVCM group, 8.7% +/- 3.4% vs 24.4% +/- 8.5%; and off-pump group, 7.8% +/- 2.8% vs 14.0% +/- 5.3%) after extubation, but the increase was significantly (P <.05) less pronounced in the off-pump group. Furthermore, pulmonary compliance decreased (P <.05) in all groups except the off-pump group after extubation. Duration of hospital and intensive care unit stay was significantly shorter (P <.05) in the off-pump group than in the other groups.

CONCLUSION

The development of intrapulmonary shunting and hypoxemia after coronary artery bypass grafting can be substantially reduced by performance of total vital capacity maneuvers while patients are mechanically ventilated. However, off-pump coronary artery bypass surgery is superior in preventing shunting and hypoxemia after bypass grafting in the immediate and early postoperative periods, probably leading to substantially shorter intensive care unit and hospital stays.

Effects of normothermia versus hypothermia on extravascular lung water and serum cytokines during cardiopulmonary bypass: a randomized, controlled trial

OBJECTIVE

To evaluate the influence of perfusion temperature on the systemic effects of cardiopulmonary bypass (CPB), including extravascular lung water index (EVLWI), and serum cytokines.

DESIGN

Prospective, randomized, controlled study.

SETTING

Cardiothoracic intensive care unit of a university hospital.

PATIENTS

Patients undergoing elective coronary artery bypass grafting.

INTERVENTIONS

Twenty-one patients undergoing elective coronary artery bypass grafting were randomly assigned to receive either normothermic bypass (36 degrees C, n = 8) with intermittent antegrade warm blood cardioplegia (IAWBC), or hypothermic (32 degrees C, n = 13) CPB with cold crystalloid cardioplegia.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure, heart rate, cardiac output, systemic vascular resistance, mean pulmonary arterial pressure, and pulmonary vascular resistance were determined at baseline, i.e., after induction of anesthesia but before sternal opening (T-1), at arrival in the intensive care unit (T0), and 4 hrs (T4), 8 hrs (T8), and 24 hrs (T24) after surgery. EVLWI, intrathoracic blood volume index (ITBVI), and EVLW/ITBV ratio were obtained by using thermal dye dilution utilizing an arterial thermistor-tipped fiberoptic catheter and were recorded at T-1, T0, T4, T8, and T24. Serial blood samples for cytokine measurements were obtained at each hemodynamic measurement time point. Before, during, and after CPB, there were no differences in the conventional hemodynamic measurements between the groups. There were no changes in EVLWI up to T8 in either group. Furthermore, no change in the ratio EVLW/ITBW was observed between the groups at any time, further indicating the absence of a change in pulmonary permeability. Plasma levels of interleukin-6, tumor necrosis factor-alpha, and interleukin-10 increased during and after CPB, independently of the perfusion temperature.

CONCLUSION

Normothermic CPB is not associated with additional inflammatory and related systemic adverse effects regarding cytokine production and EVLWI as compared with mild hypothermia. The potential temperature-dependent release of cytokines and subsequent inflammation has not been observed and normothermic CPB may be seen as a safe technique regarding this issue.

High oxygen concentration exacerbates cardiopulmonary bypass-induced lung injury

OBJECTIVE

To investigate the effect of ventilation with 100% oxygen on lung injury associated with surgery involving cardiopulmonary bypass (CPB).

DESIGN

A prospective randomized study.

SETTING

University hospital.

PARTICIPANTS

Thirty patients undergoing coronary artery bypass graft surgery with CPB.

INTERVENTIONS

Patients were randomized to receive 100% oxygen (Oxygen group) or 50% oxygen (Air group) throughout surgery. During CPB, patients' lungs in the Air group were flushed with air and in the Oxygen group with 100% oxygen.

MEASUREMENTS AND MAIN RESULTS

Lung injury was evaluated by arterial oxygen tension-inspired oxygen concentration (PaO2-FIO2) ratio and cytokine levels (tumor necrosis factor-alpha and interleukin-8) in blood and bronchoalveolar lavage fluid measured before and after CPB. The lowest PaO2-FIO2 value was observed after 40 minutes following the completion of CPB in both groups. PaO2-FIO2 values 6 hours after CPB were not different from baseline in the Air group but remained lower (359+/-63 mmHg and 298+/-78 mmHg; p = 0.013) in the Oxygen group. Blood cytokine levels rose during surgery in both groups. Bronchoalveolar lavage levels of interleukin-8 did not change, whereas tumor necrosis factor-alpha increased only in the Oxygen group (p = 0.035).

CONCLUSIONS

A significant decrease of oxygenation was observed in the early post-CPB period in both groups of patients, with delay in recovery in patients treated with 100% oxygen. A larger increase of the proinflammatory cytokines was found in patients treated with 100% oxygen. High oxygen concentrations during surgery with CPB should be used only when specifically required.

Postcardiopulmonary bypass hypoxemia: a prospective study on incidence, risk factors, and clinical significance

OBJECTIVE

To evaluate the clinical significance of low arterial oxygen tension-inspired oxygen concentration (PaO2-FIO2) ratio, as a measure of hypoxemia, in the early period after cardiac surgery with cardiopulmonary bypass (CPB); and to evaluate the preoperative, intraoperative, and postoperative factors contributing to the development of hypoxemia within the first 24 hours after cardiac surgery with CPB.

DESIGN

Prospective observational study.

SETTING

University hospital.

PARTICIPANTS

Patients who underwent elective or emergency cardiac surgery with CPB (n = 466).

INTERVENTIONS

Preoperative clinical and laboratory data were recorded, as were intraoperative and postoperative data regarding the PaO2-FIO2 ratio, fluid and drug therapy, and chest radiograph. Data analysis evaluated hypoxemia as depicted by the PaO2-FIO2 ratios at 1, 6, and 12 hours after surgery. Thereafter, the effect of the PaO2-FIO2 ratios on time to extubation, lung injury, and length of hospital stay was evaluated. The risk factors were analyzed in 3 separate periods: preoperative, intraoperative, and postoperative. Univariate and multivariate analyses were performed on each period separately. All data were analyzed in 2 consecutive steps: univariate analysis and multivariate analysis.

MEASUREMENTS AND MAIN RESULTS

PaO2-FIO2 ratios after CPB were significantly lower compared with baseline values. Six patients (1.32%) met the clinical criteria compatible with acute lung injury. All 6 patients had prompt recovery. Significant risk factors for hypoxemia were age, obesity, reduced cardiac function, previous myocardial infarction, emergency surgery, baseline chest radiograph with alveolar edema, high creatinine level, prolonged CPB time, decreased baseline PaO2-FIO2, use of dopamine after discontinuation of CPB, coronary artery bypass grafting, use of left internal mammary artery, higher pump flow requirement during CPB, increased level of hemoglobin or total protein content, persistent hypothermia 2 and 6 hours after surgery, requirement for reexploration, event requiring reintubation, and chest radiograph with alveolar edema 1 hour after surgery. Six hours after surgery, a lower PaO2-FIO2 ratio correlated significantly with time to extubation and lung injury.

CONCLUSIONS

This study shows that despite improvements in the technique of CPB, hypoxemia depicted by low PaO2-FIO2 ratios is common in patients after CPB. It is short lived, however, and has minimal effect on the postoperative clinical course of these patients.

Ventilatory and diffusion abnormalities in long-term survivors after orthotopic heart transplantation

OBJECTIVE

To investigate the long-term development of pulmonary diffusion abnormalities after orthotopic heart transplantation (oHT).

DESIGN

Retrospective analysis of pulmonary function test results of different patient groups at different time intervals after oHT was performed.

PATIENTS

This investigation included 642 patients who had undergone oHT for chronic heart failure. Patients were grouped according to the time elapsed after transplantation (group 1: n = 164; age, 47 +/- 14 years; days after oHT, 324 +/- 101; group 2: n = 100; age, 48 +/- 15 years; days after oHT, 723 +/- 104; group 3: n = 106; age, 52 +/- 12 years; days after oHT, 1,092 +/- 98; group 4: n = 84; age, 51 +/- 13 years; days after oHT, 1,442 +/- 99; group 5: n = 61; age, 50 +/- 14 years; days after oHT, 1,819 +/- 105; group 6: n = 101; age, 53 +/- 12 years; days after oHT, 2,463 +/- 303; and group 7: n = 26; age, 54 +/- 14 years; days after oHT, 3,478 +/- 246). In 56 (group 8) of the 642 patients, follow-up measurements were performed with tests before and at two time points after oHT (6.5 +/- 1.7 and 12.5 +/- 9.3 months).

RESULTS

Of all patients, 39% showed restrictive and obstructive abnormalities with no differences between the groups. No significant differences in lung transfer factor for carbon monoxide (DLCO) were observed (61.2 vs 63.7 vs 65.5 vs 65.6 vs 64.5 vs 65.7 vs 67.6% predicted). Differences in transfer coefficient for carbon monoxide (Kco) were significant between group 1 and 4 (58.7 vs 64.1% predicted), and group 1 and 6 (58.7 vs 63.4% predicted). No differences occurred in the rate with which patients exhibited pathologic abnormalities for DLCO and KCO. After oHT, a marked reduction in diffusion capacity occurred in group 8. On follow-up, these measurements were only slightly restored in terms of the predicted DLCO percentage. No such improvement was observed in KCO or in the rate of pathologic changes for both DLCO and KCO. We conclude, therefore, that the impairment of diffusion does not improve even after a significant period has passed after the oHT. Whether this has any effect on symptoms and/or the prognosis for these patients is extremely unclear.

Transition from cardiopulmonary bypass to the HeartMate left ventricular assist device

BACKGROUND

Safe transition from cardiopulmonary bypass to the HeartMate left ventricular assist device without periods of low output, air emboli, or injury to the right ventricle is vital to its successful implantation. A right atrial-to-left ventricular shunt has been developed to purge quickly and completely all air from the system and prevent its reentry, as well as to assist the right ventricle during the transition from cardiopulmonary bypass to the HeartMate.

METHODS

From January 1994 through July 1996, we used an extracorporeal membrane oxygenation right atrial-to-left ventricular shunt during 17 HeartMate implantations in 16 patients. The shunt consists of the existing right atrial two-stage cannula, the bypass circuit, and a separate aortic line that fills the left ventricle using a 21F cannula in the lateral ventricular wall. Air is monitored in the heart and aorta using transesophageal echocardiography.

RESULTS

Ten of the 16 patients are living and 8 have undergone transplantation. Two patients are still using the device and are awaiting transplantation. None of the patients have experienced postoperative neurologic events suggestive of air emboli.

CONCLUSIONS

The extracorporeal membrane oxygenation right atrial-to-left ventricular shunt is simple and inexpensive to construct. It provides for a smoother and safer transition from cardiopulmonary bypass to the HeartMate left ventricular assist device.

Upregulation of collagen messenger RNA expression occurs immediately after lung damage

BACKGROUND

Mortality of ARDS still exceeds 50%. Though pulmonary fibrosis is a marker of severe prognosis in the evolution of ARDS, its onset is not yet established. Cardiopulmonary bypass (CPB), usually utilized in patients with a previously normal lung, can cause ARDS and often causes alveolar damage, the earliest lesion observed in ARDS, thus providing a unique opportunity to study the molecular mechanisms of fibrogenesis.

OBJECTIVE

To measure immediately after CPB, at the onset of alveolar damage, the expression of messenger RNAs (mRNAs) for collagen type I.

METHODS

Pre-CPB and post-CPB lung biopsy specimens were obtained from patients submitted to myocardial revascularization for coronary artery disease. Alveolar damage was characterized by comparison between before and after specimens and quantified by point counting of polymorphonuclear cells (PMN). Type I collagen mRNAs were quantified by scanning densitometry of Northern blot autoradiographs, corrected for RNA loading by 18S ribosomal RNA hybridization.

RESULTS

Alveolar damage was characterized by lung interstitial edema and by polymorphonuclear cell infiltration after CPB (PMN pre-CPB 0.010+/-0.004xPMN post-CPB 0.052+/-0.022; n=7; p=0.0017, t test). Type I collagen mRNA increased 91.1+/-68.2% (Ln pre-CPBxLn post-CPB; n=15; p<0.00001, t test) immediately after CPB (mean CPB time, 108.8+/-37.2 min).

CONCLUSION

Fibrogenesis, as measured at the molecular level, is a very early event following diffuse alveolar damage, attributable mainly to resident fibroblast activation.

What is 'minimally invasive' coronary bypass surgery? Experience with a variety of surgical revascularization procedures for single-vessel disease

BACKGROUND

Although the use of small incisions is theoretically appealing, it has been argued that the true advantage of minimally invasive approaches to myocardial revascularization lies in the avoidance of cardiopulmonary bypass.

METHODS

Of 25 patients referred for surgical revascularization of single-vessel coronary disease, 20 elected to undergo a minimally invasive coronary artery bypass grafting (MICABG) procedure, while 5 opted to have conventional surgery with cardiopulmonary bypass (CPB). Patients having MICABG underwent single-vessel revascularization without CPB, via limited anterior thoracotomy, hemisternotomy, or median sternotomy. Intraoperatively, hemodynamics, anastomotic time, and total operative time were recorded. Postoperatively, length of hospital stay, incidence of myocardial infarction, indexes of end-organ function, and morbidity rates were recorded. In addition, patient questionnaires were used to assess subjective end points such as postoperative pain, wound drainage, and quality of life.

RESULTS

Fifteen of 20 patients undergoing MICABG underwent revascularization without CPB, while 4 were converted to standard coronary artery bypass grafting with CPB due to technical reasons and 1 for intraoperative ventricular fibrillation. Patients undergoing MICABG had no perioperative myocardial infarctions, while those having CPB had two infarctions (20%). Furthermore, there were no differences in length of stay or postoperative morbidity among the various approaches, while the MICABG procedures, especially via median sternotomy, were associated with shorter operative times.

CONCLUSIONS

The advantage of MICABG lies mainly in the avoidance of CPB. Thus, we advocate that surgeons initially utilize the median sternotomy and limited skin incision for MICABG to assure adequate exposure, technical precision, and patient safety. After a reasonable level of technical proficiency and experience are attained, the limited anterior thoracotomy approach can be used.

Cardiopulmonary effects of enoximone or dobutamine and nitroglycerin on mitral valve regurgitation and pulmonary venous hypertension

OBJECTIVE

To compare the cardiovascular and pulmonary effects of the phosphodiesterase III inhibitor enoximone (EN) or a combination of dobutamine (DOB) and nitroglycerin (NTG) before and after mitral valve repair or replacement.

DESIGN

Prospective, randomized, controlled clinical study.

SETTING

University hospital.

PARTICIPANTS

Twenty patients with mitral regurgitation and pulmonary venous hypertension scheduled for elective mitral valve surgery.

INTERVENTIONS

Patients fulfilling the inclusion criteria of the study were randomly allocated into a group treated with EN (group 1, n = 10) or DOB and NTG (group 2, n = 10). A cardiopulmonary status was obtained after induction of anesthesia and mechanical ventilation during stable hemodynamic conditions (control). Then the patients received either EN (bolus dose 1.0 mg/kg followed by a continuous infusion of 10 micrograms/kg/min) or DOB (8.0 micrograms/kg/min) and NTG (1.0 microgram/kg/min) according to the randomization. After a period of 20 minutes, all parameters were measured again. The study drugs were stopped, and cardiac surgery was performed. Infusions of EN (without additional loading dose) or DOB and NTG were started again in the above-described doses 10 minutes before separation from cardiopulmonary bypass (CPB). Respiratory and hemodynamic measurements were made 20 minutes after weaning from CPB and 60 minutes after admission of the patient to the intensive care unit.

MEASUREMENTS AND MAIN RESULTS

Both groups were comparable regarding preoperative and control data. Before mitral valve surgery, cardiac output (CO) and heart rate (HR) increased by 46% (p < 0.05) and 31% (p < 0.01) during infusion of EN with minor changes of mean systemic arterial pressure (PSA) and gas exchange. Mean pulmonary arterial pressure (PPA) decreased from 32 +/- 11 mmHg to 23 +/- 11 mmHg (p < 0.05). Similar alterations were observed in group 2 (delta CO + 26%, p < 0.05, delta HR + 39%, p < 0.01); however, PPA and calculated pulmonary vascular resistance remained unchanged. After separation from CPB, EN and DOB-NTG achieved comparable effects on CO, HR, and PSA, but PPA was significantly lower in group 1. In addition, venous admixture and alveolo-arterial oxygen tension gradient were lower in EN-treated patients.

CONCLUSION

Enoximone or DOB and NTG have comparable effects on CO, PSA, and HR in mitral regurgitation and pulmonary hypertension, but EN is more effective in reducing PPA without deterioration of gas exchange.

Extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation has now evolved into standard therapy for patients unresponsive to conventional ventilatory and pharmacological support. This article presents a clinical review of extracorporeal life support and its application to neonatal and pediatric patients as well as children requiring circulatory support after open heart surgery.