Efficacy and safety of milrinone in preventing low cardiac output syndrome in infants and children after corrective surgery for congenital heart disease

Postoperative course in the cardiac intensive care unit following the first stage of Norwood reconstruction

The medical records of all patients born between 1 September, 2000, and 31 August, 2002, and undergoing the first stage of Norwood reconstruction, were retrospectively reviewed for details of the perioperative course. We found 99 consecutive patients who met the criterions for inclusion. Hospital mortality for the entire cohort was 15.2%, but was 7.3%, with 4 of 55 dying, in the setting of a "standard" risk profile, as opposed to 25.0% for those with a "high" risk profile, 11 of 44 patients dying in this group. Extracorporeal membrane oxygenation was utilized in 7 patients, with 6 deaths. Median postoperative length of stay in the hospital was 14 days, with a range from 2 to 85 days, and stay in the cardiac intensive care unit was 11 days, with a range from 2 to 85 days. Delayed sternal closure was performed in 18.2%, with a median of 1 day until closure, with a range from zero to 5 days. Excluding isolated delayed sternal closure, and cannulation and decannulation for extracorporeal support, 24 patients underwent 33 cardiothoracic reoperations, including exploration for bleeding in 12, diaphragmatic plication in 4; shunt revision in 4, and other procedures in 13. The median duration of total mechanical ventilation was 4.0 days, with a range from 0.7 to 80.5 days. Excluding those who died, the median total duration of mechanical ventilation was 3.8 days, with a range from 0.9 to 46.3 days. Reintubation for cardiorespiratory failure or upper airway obstruction was performed in 31 patients. Postoperative electroencephalographic and/or clinical seizures occurred in 13 patients, with 7 discharged on anti-convulsant medications. Postoperative renal failure, defined as a level of creatinine greater than 1.5 mg/dl, was present in 13 patients. Eleven had significant thrombocytopenia, with fewer than 20,000 platelets per microl, and injury to the vocal cords was identified in eight patients. Risk factors for longer length of stay included lower Apgar scores, preoperative intubation, early reoperations, reintubation and sepsis, but not weight at birth, genetic syndromes, the specific surgeon, or the duration of surgery. Although mortality rates after the first stage of reconstruction continue to fall, the course in the intensive care unit is remarkable for significant morbidity, especially involving the cardiac, pulmonary and central nervous systems. These patients utilize significant resources during the first hospitalization. Further studies are necessary to stratify the risks faced by patients with hypoplasia of the left heart in whom the first stage of Norwood reconstruction is planned, to determine methods to reduce perioperative morbidity, and to determine the long-term implications of short-term complications, such as diaphragmatic paresis, injury to the vocal cords, prolonged mechanical ventilation, and postoperative seizures.

Peri-operative management of paediatric patients undergoing cardiac surgery--focus on respiratory aspects of care

Children requiring cardiac surgery present particular challenges in peri-operative respiratory management. The wide variety of conditions and operations and their varied impact on respiratory function makes dialogue with related medical staff essential. In most circumstances, cardiac performance is the main determinant of respiratory outcomes. Changing cardiologic and surgical approaches have combined to diminish the severity and frequency of pulmonary hypertensive issues and new treatment modalities are simplifying the intensive care approach. Patients with Down's syndrome and 22q11 deletion syndrome present particular issues related to anatomy, physiology and respiratory function. Certain conditions, including tetralogy of Fallot and cavopulmonary connections, present unique circumstances where respiratory management, sometimes including extubation, may assist in optimisation of cardiac performance. These and other conditions highlight the complexities of cardiopulmonary interactions. Cardiac performance remains the principal determinant of outcome after paediatric cardiac surgery and has the biggest impact on respiratory function.

Medical management of the failing Fontan

The Fontan operation accomplishes complete separation of systemic venous blood from pulmonary venous circulation in patients with single ventricle anatomy. Operative survival since the first description of the Fontan operation is excellent in the current era through modifications in surgical techniques, identification of patient-specific risk factors, and advances in postoperative care. Improved early outcomes have also resulted in a decline in late mortality for patients who have undergone staged palliation with the Fontan operation. As the number of late survivors from the Fontan operation increases, caregivers will be evermore faced with the challenge of recognizing and managing the patient with failing Fontan physiology. Even after excellent early results, patients with single ventricle lesions remain at risk of progressive ventricular dysfunction, dysrhythmias, progressive hypoxemia, elevated pulmonary vascular resistance, and protein-losing enteropathy, which can result in morbidities including but not limited to, myocardial failure, thromboembolism, and stroke. Consequently, continued long-term survival of patients who undergo the Fontan operation is dependent upon preservation of single ventricle function, avoidance of late complications, and, in the patient with a failing Fontan, recognition and treatment of the underlying pathophysiologic process that has resulted in Fontan failure.

B-type natriuretic peptide levels predict outcome after neonatal cardiac surgery

OBJECTIVES

Neonates undergoing cardiac surgery are at high risk for adverse outcomes. B-type natriuretic peptide is used as a biomarker in patients with cardiac disease, but the predictive value of B-type natriuretic peptide after cardiac surgery in neonates has not been evaluated. Therefore, the objective of this study was to determine the predictive value of perioperative B-type natriuretic peptide levels for postoperative outcomes in neonates undergoing cardiac surgery.

METHODS

Plasma B-type natriuretic peptide determinations were made before and 2, 12, and 24 hours after surgery in 36 consecutive neonates. B-type natriuretic peptide levels and changes in perioperative B-type natriuretic peptide were evaluated as predictors of postoperative outcome.

RESULTS

B-type natriuretic peptide levels at 24 hours were lower than preoperative levels (24-h/pre B-type natriuretic peptide ratio < 1) in 29 patients (81%) and higher (24-h/pre B-type natriuretic peptide ratio > or = 1) in 7 patients (19%). A 24-hour/pre B-type natriuretic peptide level of 1 or greater was associated with an increased incidence of low cardiac output syndrome (100% vs 34%, P = .002) and fewer ventilator-free days (17 +/- 13 days vs 26 +/- 3 days, P = .002), and predicted the 6-month composite end point of death, an unplanned cardiac operation, or cardiac transplant (57% vs 3%, P = .003). A 24-hour/pre B-type natriuretic peptide level of 1 or greater had a sensitivity of 80% and a specificity of 90% for predicting a poor postoperative outcome (P = .003).

CONCLUSION

In neonates undergoing cardiac surgery, an increase in B-type natriuretic peptide 24 hours after surgery predicts poor postoperative outcome.

Hypoplastic left heart syndrome: consensus and controversies in 2007

Variability in practice can be considered to foster clinical innovation, and allow for individualized therapeutic plans and independence of practitioners. The Institute of Medicine, however, has issued a report suggesting that variability in patterns of practice are "illogical", and should be avoided whenever possible. Perhaps nowhere in the field of congenital cardiac disease is variability in practice more apparent than in the management of hypoplastic left heart syndrome. This review assesses the variability in practice at a large number of centres that manage neonates with hypoplastic left heart syndrome, with an emphasis on practice before, during, and after the first stage of the Norwood sequence of operations. We also suggest changes in future strategies for research. In March, 2007, colleagues were contacted to respond to an internet-based survey using commercially available software (www.surveymonkey.com) to collect responses about the management practices for neonates with "straight-forward" hypoplastic left heart syndrome. No attempt was made to correlate management practices with any measures of outcome, as neither the practices themselves, nor the outcomes of interest, could be externally validated. Data is reported from 52 centers thought to manage over 1000 neonates with hypoplastic left heart syndrome on an annual basis. The first stage of the Norwood sequence was "recommended" to families by approximately five-sixths (86.5%) of the centres. No centre recommended primary cardiac transplantation, a "hybrid" approach, or non-intervention. In 7 centres (14.5%), it was reported that there was discussion of some or all of the above options, but ultimately the families decided upon the appropriate strategy. Most centres preferentially used antegrade cerebral perfusion (54%) in contrast to deep hypothermia with circulatory arrest (24%), albeit that 11% of centres used a combination of these techniques and in 9% the support strategy was based on surgeon preference. The source of flow of blood for the lungs following the first stage of reconstruction was also highly variable. Of the 51 centres that responded to the question, 13 (25.5%) were participating in a multi-centric randomized clinical trial comparing the modified Blalock-Taussig shunt to the conduit placed from the right ventricle to the pulmonary arteries, the so-called "Sano" modification. Of the remaining 38 centres, 18 "usually" placed a conduit from the right ventricle to the pulmonary artery, 14 "usually" placed a modified Blalock-Taussig shunt, and at six centres, the decision was made "based upon the preference of the surgeon and/or the cardiologist". Similarly, significant variability in practice was evident in preoperative management, other surgical strategies, postoperative medical support, monitoring and discharge planning. Other than the randomized clinical trial of shunt type, no other medical or surgical management strategy was currently under investigation in a multi-centric or randomized trial in the centres who responded to the survey. The survey emphasises the extreme variability in our current practices for treatment of children with hypoplastic left heart syndrome. While there are some areas for which there is consensus in management, the majority of our practices are variable between and within centres. These results emphasize that large multicentric trials and registries are necessary to improve care, and to answer important clinical questions, emphasizing the need to shift from analysis of experiences of single centres to multi-centric and multi-disciplinary collaboration.

Cardiopulmonary resuscitation: special considerations for infants and children with cardiac disease

Pulseless cardiac arrest, defined as the cessation of cardiac mechanical activity, determined by unresponsiveness, apneoa, and the absence of a palpable central pulse, accounts for around one-twentieth of admissions to paediatric intensive care units, be they medical or exclusively cardiac. Such cardiac arrest is higher in children admitted to a cardiac as opposed to a paediatric intensive care unit, but the outcome of these patients is better, with just over two-fifths surviving when treated in the cardiac intensive care unit, versus between one-sixth and one-quarter of those admitted to paediatric intensive care units. Children who receive chest compressions for bradycardia with pulses have a significantly higher rate of survival to discharge, at 60%, than do those presenting with pulseless cardiac arrest, with only 27% surviving to discharge. This suggests that early resuscitation before the patient becomes pulseless, along with early recognition and intervention, are likely to improve outcomes. Recently published reports of in-hospital cardiac arrests in children can be derived from the multi-centric National Registry of Cardiopulmonary Resuscitation provided by the American Heart Association. The population is heterogeneous, but most arrests occurred in children with progressive respiratory insufficiency, and/or progressive circulatory shock. During the past 4 years at the Children's Hospital of Philadelphia, 3.1% of the average 1000 annual admissions to the cardiac intensive care unit have received cardiopulmonary resuscitation. Overall survival of those receiving cardiopulmonary resuscitation was 46%. Survival was better for those receiving cardiopulmonary resuscitation after cardiac surgery, at 53%, compared with survival of 33% for pre-operative or non-surgical patients undergoing resuscitation. Clearly there is room for improvement in outcomes from cardiac resuscitation in children with cardiac disease. In this review, therefore, we summarize the newest developments in paediatric resuscitation, with an expanded focus upon the unique challenges and importance of anticipatory care in infants and children with cardiac disease.

Time course and prognostic value of plasma B-type natriuretic peptide concentration in neonates undergoing the arterial switch operation

BACKGROUND

Plasma B-type natriuretic peptide (BNP) can predict postoperative complications after cardiac surgery in adults. Our aim was to investigate BNP kinetics and prognostic value in neonates undergoing the arterial switch operation (ASO) for transposition of the great arteries (TGA).

METHODS

We measured BNP concentrations in 30 neonates before, immediately after, and 6, 12, 24, and 48 h after ASO for TGA. Complicated postoperative evolution was defined as patients requiring mechanical ventilation or presenting low cardiac output syndrome for more than 72 h. We studied the ability of postoperative BNP concentrations to predict complicated evolution.

RESULTS

Intubation duration, inotropic support duration, and intensive care unit stay were 68 (48-121) h, 78 (69-141) h, and 96 (76-149) h respectively. Patients with complicated evolution had higher 6 and 12-h BNP concentrations than patients with simple evolution (459 (210-897) vs 137 (67-248) ng/L and 547 (193-868) vs 185 (79-354) ng/L respectively; P < 0.05) and had longer intubation, inotropic support, and intensive care unit stay (96 (70-190) vs 50 (48-66) h, 100 (83-190) vs 70 (59-72) h, and 120 (90-240) vs 84 (72-96) h, P < 0.05). A 6-h BNP concentration >160 ng/L was able to predict complicated evolution with a sensitivity of 93% and a specificity of 67%.

CONCLUSION

In neonates, BNP concentrations can predict adverse outcome in the postoperative period after ASO for TGA. This marker has potential clinical applications.

Glucocorticoid therapy for hypotension in the cardiac intensive care unit

In recent years, it has been our practice to treat persistent hypotension in the cardiac intensive care unit with glucocorticoids. We undertook a retrospective review in an attempt to identify predictors of a hemodynamic response to steroids and of survival in these patients. Patients who had received glucocorticoids for hypotension over a 2-year period were identified retrospectively. Summary measures of blood pressure, heart rate, urine output, inotrope score, and volume of infused fluid were calculated for the 12 hours before and the 24 hours following initiation of glucocorticoid therapy. A hemodynamic response was defined as a > or =20% increase in mean blood pressure without an increase in inotrope score following initiation of steroid therapy. Fifty-one patients were included, of whom 6 (11.8%) died. Serum cortisol was measured in 43 patients (84.3%) and was below the lower limit of normal (<5 microg/dl) in 20 of these (46.5%). Following initiation of steroid therapy, blood pressure and urine output increased, whereas heart rate, inotrope score, and infused volume decreased. There were 21 (41.1%) hemodynamic responders, all of whom survived, whereas 6 of 30 (20%) nonresponders died (p = 0.036). No predictors of a hemodynamic response to steroid were identified. Some critically ill children with cardiac disease and inotrope refractory hypotension demonstrated hemodynamic improvement following glucocorticoid administration. An improvement in blood pressure following administration of glucocorticoid was associated with survival, but we were unable to identify predictors of that response.

Population pharmacokinetics and dosing regimen design of milrinone in preterm infants

AIMS

To define the pharmacokinetics of milrinone in very preterm infants and determine an optimal dose regimen to prevent low systemic blood flow in the first 12 h after birth.

METHODS

A prospective open-labelled, dose-escalation pharmacokinetic study was undertaken in two stages. In stage one, infants received milrinone at 0.25 microg/kg/min (n = 8) and 0.5 microg/kg/min (n = 11) infused from 3 to 24 h of age. Infants contributed 4-5 blood samples for concentration-time data which were analysed using a population modelling approach. A simulation study was used to explore the optimal dosing regimen to achieve target milrinone concentrations (180-300 ng/ml). This milrinone regimen was evaluated in stage two (n = 10).

RESULTS

Infants (n = 29) born before 29 weeks gestation were enrolled. Milrinone pharmacokinetics were described using a one-compartment model with first-order elimination rate, with a population mean clearance (CV%) of 35 ml/h (24%) and volume of distribution of 512 ml (21%) and estimated half-life of 10 h. The 0.25 and 0.5 microg/kg/min dosage regimens did not achieve optimal milrinone concentration-time profiles to prevent early low systemic blood flow. Simulation studies predicted a loading infusion (0.75 microg/kg/min for 3 h) followed by maintenance infusion (0.2 microg/kg/min until 18 h of age) would provide an optimal milrinone concentration profile. This was confirmed in stage two of the study.

CONCLUSION

Population pharmacokinetic modelling in the preterm infant has established an optimal dose regimen for milrinone that increases the likelihood of achieving therapeutic aims and highlights the importance of pharmacokinetic studies in neonatal clinical pharmacology.

Effects of low-dose milrinone on weaning from cardiopulmonary bypass and after in patients with mitral stenosis and pulmonary hypertension

The phosphodiesterase inhibitor milrinone is usually preferred in patients with pulmonary hypertension and myocardial dysfunction after cardiopulmonary bypass. We investigated the effects of low-dose milrinone on pulmonary hypertension in the immediate pre- and postoperative period. Forty-seven patients were randomized to the control and milrinone groups. All patients had mean pulmonary artery pressure greater than 30 mmHg and pulmonary capillary wedge pressure greater than 20 mmHg and were candidates for mitral valve replacement for rheumatic mitral stenosis. Twenty-four patients received a loading dose of milrinone 25 microg/kg(-1) during weaning from cardiopulmonary bypass, followed by a maintenance dose of 0.25 microg/kg(-1)/min(-1) to the end of the surgery. Cardiac output and other hemodynamic variables were noted at induction, weaning from bypass, and postoperative 1 h. Pulmonary artery pressure, capillary wedge pressure, and central venous pressure were significantly lower in the milrinone group during weaning after cardiopulmonary bypass, while other variables were roughly similar. However, patients in the control group required higher doses of vasodilators, inotropes, and antiarrhythmic agents. Mean arterial pressure in the milrinone group was significantly lower at 1 h postoperatively than in the control group; however, the patients did not need many more vasopressors. Fluid restriction and diuretic agent use were more significant in the control group. Systemic arterial hypotension and vasopressor requirements with milrinone use at inotropic doses were not observed at the doses used for the study. A total of 21.7% of the patients in the control group required vasopressors in the perioperative period. Both groups demonstrated similar hematologic variables except that the hemoglobin level in the control group was significantly lower during postoperative days 1 and 7. Low-dose milrinone for a short-term during weaning from cardiopulmonary bypass may be used in patients with mitral stenosis and pulmonary hypertension for its effects on pulmonary artery pressures, less inotropic and vasopressor requirements, and fluid balance.

Inhaled milrinone: a new alternative in cardiac surgery?

The administration of milrinone through inhalation has been studied in only a few animal and human studies. Compared to the intravenous administration, inhaled milrinone has been shown to reduce pulmonary artery pressure without systemic hypotension. Therefore, this approach could represent an alternative to nitric oxide. This current state of knowledge of intravenous and inhaled milrinone is presented and summarized.

Neurodevelopmental outcomes following congenital heart surgery

Advances in both surgical techniques and perioperative care have led to improved survival outcomes in infants and children undergoing surgery for complex congenital heart disease. An awareness is emerging that early and late neurological morbidities complicate the outcome of these operations. Adverse neurological outcomes after neonatal and infant cardiac surgery are related to both fixed and modifiable mechanisms. Fixed factors include many variables specific to the individual patient, including genetic predisposition, gender, race, socioeconomic status, and in utero central nervous system development. Modifiable factors include not only intraoperative variables (cardiopulmonary bypass, deep hypothermic circulatory arrest, and hemodilution) but also such variables as hypoxemia, hypotension, and low cardiac output. The purpose of this review is to examine these mechanisms as they relate to available outcome data.

Left ventricular contractility in extremely premature infants in the first day and response to inotropes

The aim was to assess myocardial contractility in infants born <30 wk gestation developing low systemic blood flow (SBF) in the first day, and the effect of dobutamine versus dopamine. Superior vena cava (SVC) flow was used as a measure of SBF at 3, 10, and 24 h (n = 106). Infants with low SVC flow randomized to dopamine or dobutamine. Myocardial contractility was determined by the relationship between left ventricular (LV) mean velocity of circumferential fiber shortening (mVcfs) and wall stress. Infants who developed low SVC flow had significantly worse myocardial contractility at 3 h, but not 10 h. At 24 h, low-flow infants had lower than expected mVcfs for any given LV stress. In 37 infants randomized to inotrope, there was no significant difference in contractility at 10 microg/kg/min. At 20 microg/kg/min (n = 21), dopamine increased whereas dobutamine decreased LV stress. Infants on dobutamine had significantly lower than expected mVcfs for any given LV stress compared with infants on dopamine. Contractility was not improved by either inotrope at either dose. In conclusion, infants developing low SVC flow in the first day have worse myocardial contractility at 3 h. Neither inotrope increased contractility, but dopamine increased LV stress at 20 microg/kg/min.

Mechanisms of a reduced cardiac output and the effects of milrinone and levosimendan in a model of infant cardiopulmonary bypass

OBJECTIVES

A low cardiac output state is an important cause of morbidity after pediatric cardiopulmonary bypass. The objectives of our study were to define the early precipitants of the reduced cardiac output and to investigate the effects on these of milrinone and levosimendan in a model of pediatric cardiopulmonary bypass.

DESIGN

Experimental study.

SETTING

: Research laboratory at a university-affiliated, tertiary pediatric center.

SUBJECTS

Eighteen piglets.

INTERVENTIONS

Piglets, instrumented with systemic, pulmonary arterial, and coronary sinus catheters, pulmonary and circumflex arterial flow probes, and a left ventricular conductance-micromanometer-tipped catheter, underwent cardiopulmonary bypass with aortic cross-clamp and cardioplegic arrest. At 120 mins, they were assigned to control, milrinone, or levosimendan groups and studied for a further 120 mins.

MEASUREMENTS AND MAIN RESULTS

In controls, between 120 and 240 mins, cardiac output decreased by 15%. Systemic vascular resistance was unchanged, but pulmonary vascular resistance increased by 19%. Systemic arterial elastance increased by 17%, indicating increased afterload. End-systolic elastance was unchanged, and coronary sinus oxygen tension decreased by 4.0 +/- 1.7 mm Hg. In animals receiving milrinone cardiac output was preserved, and in animals receiving levosimendan cardiac output increased by 14%. Both drugs prevented an increase in arterial elastance and pulmonary vascular resistance after cardiopulmonary bypass. Systemic vascular resistance decreased by 31% after levosimendan, and end-systolic elastance increased by 48%, indicating improved contractility. Both agents prevented a decrease in coronary sinus oxygen tension.

CONCLUSIONS

Increased afterload, which is not matched by an equivalent elevation in contractility, contributes to the reduced cardiac output early after pediatric cardiopulmonary bypass in this model. This increase is prevented by milrinone and levosimendan. Both agents exert additional beneficial effects on pulmonary vascular resistance and myocardial oxygen balance, although levosimendan has greater inotropic properties.

The hemodynamically significant ductus arteriosus in critically ill full-term neonates. Two case reports?

In premature infants, the clinical effects and management of a hemodynamically significant patent ductus arteriosus (HSDA) are well-described. In full-term neonates the ductus arteriosus (DA) is rarely monitored except in cases of concomitant pulmonary hypertension or duct dependent congenital heart disease. Although systemic-pulmonary shunting commonly occurs in mature infants, coinciding with the normal postnatal fall in pulmonary vascular resistance, cardiac failure in the neonatal period is rarely attributed directly to the DA. In this case series, we report two full-term infants who were initially treated for pulmonary hypertension and myocardial dysfunction but developed clinical, radiographic and two-dimensional echocardiographic evidence of cardiac failure secondary to a large unrestrictive patent DA (PDA). One patient was treated with indomethacin, and, although transductal diameter decreased, there was no clinical benefit. Cardiac failure resolved and myocardial function improved in both cases after PDA ligation. We suggest that PDA be monitored closely in neonates recovering from PPHN who have ongoing oxygenation difficulties or myocardial failure. PDA ligation should be considered an option for full term neonates with cardiac failure secondary to a HSDA when other therapeutic options fail.

Intermittent warm blood cardioplegia in the surgical treatment of congenital heart disease: Clinical experience with 1400 cases

OBJECTIVE

To analyze our experience with warm blood cardioplegia in pediatric cardiac surgery.

METHODS

We used intermittent (every 15 minutes after initial injection) warm blood cardioplegia in the treatment of 1400 patients. Results were retrospectively compared with those of 950 patients treated with cold blood cardioplegia. The following parameters were analyzed: (1) hydric balance of cardioplegic solution; (2) resumption of rhythm after aortic crossclamp removal; (3) duration of mechanical ventilation, intensive care unit stay, and incidence of mortality in 4 selected diagnostic groups: ventricular septal defect, tetralogy of Fallot, atrioventricular septal defect, and transposition of the great arteries. These 4 groups, treated with warm or cold cardioplegia, were comparable with regard to age, weight, crossclamp times, and percent with Down syndrome; (4) troponin level at 12 hours after aortic crossclamping; and (5) duration of intensive care unit stay for the 1400 patients.

RESULTS

Warm versus cold cardioplegia: negligible fluid addition with warm cardioplegia compared with blood loss/prime dilution induced by cold cardioplegia; spontaneous resumption of sinus rhythm in 99% versus 77% of patients (P < .001); shorter duration of ventilatory support in each diagnostic group, significant in all cases; smaller increase in troponin in each group (P < .05). Incidence of early death was not different in the 2 groups. For the whole group, duration of the intensive care unit stay was less than 48 hours in 86% versus 75% (P < .001).

CONCLUSION

In our experience, normothermic cardioplegia has not generated any particular inconvenience and its use was contemporary, with improved outcomes.

Milrinone improves oxygenation in neonates with severe persistent pulmonary hypertension of the newborn

BACKGROUND

Many neonates with severe persistent pulmonary hypertension of the newborn (PPHN) are nonresponders to inhaled nitric oxide (iNO). Milrinone is a promising adjunctive therapy because of its pulmonary vasodilator properties and cardiotropic effects.

DESIGN

Case series of neonates with severe PPHN (defined as oxygenation index [OI] >20, failure of iNO therapy, and echocardiographic confirmation of PPHN).

SETTING

Tertiary neonatal intensive care unit.

SUBJECTS

Full-term (> or =37 weeks) neonates with severe PPHN who received intravenous milrinone.

MEASUREMENTS

The primary end point was the effect of intravenous milrinone on OI and hemodynamic stability over a 72-hour study period. Secondary end points examined included duration of iNO and degree of cardiorespiratory support.

RESULTS

Nine neonates at a mean gestation of 39.25 +/- 2.76 weeks, birth weight of 3668 +/- 649.1 g, and baseline OI of 28.1 +/- 5.9 received milrinone treatment after a poor initial response to iNO treatment. Intravenous milrinone was commenced at a median age of 21 hours (range, 18-49 hours), and patients were treated for median of 70 hours (range, 23-136). Oxygenation index was significantly reduced after milrinone treatment, particularly in the immediate 24 hours of treatment (8.0 +/- 6.6, P < .001). There was a significant improvement in heart rate (179 +/- 15.2 vs 149.6 +/- 22.4, P < .001) over the same period. Infants who received milrinone did not develop systemic hypotension; in fact, there was a nonsignificant trend toward improved blood pressure.

CONCLUSIONS

Intravenous milrinone produces early improvements in oxygenation without compromising systemic blood pressure.

Advances in cardiac intensive care

PURPOSE OF REVIEW

As surgical survival in children with congenital heart disease, particularly those with univentricular hearts, has improved in recent years, focus has shifted to reducing the morbidity of congenital cardiac malformations and their treatment. This review will focus on emerging therapies aimed at reducing these morbidities in the intensive care unit.

RECENT FINDINGS

A protracted stay in the intensive care unit after cardiac surgery is a risk factor for developing various morbidities. Therapies or interventions that may hasten postoperative recovery and minimize the length of stay are thus important to evaluate. Fluid overload, renal dysfunction, low cardiac output and neurological dysfunction remain major contributors to morbidity after cardiac surgery. In addition, the treatment of these adverse states can potentially compound the injury.

SUMMARY

The reduction in morbidity after cardiac surgery remains challenging. Recent insights have allowed us to recognize the impact of factors beyond the intraoperative period as significant contributors to morbidity. As our field continues to evolve, future studies should focus on emerging technologies and therapies that facilitate the prevention of physiological states that compound congenital morbidities.

Levosimendan for low cardiac output: a pediatric experience

This was a retrospective observational study in a pediatric intensive care unit, in which 19 patients received levosimendan. There were no adverse events attributable to levosimendan and no instances where the clinical condition worsened after administration. Arterial lactate levels decreased significantly following levosimendan administration during cardiopulmonary bypass for anticipated low cardiac output. In those with established low cardiac output, trends toward improved hemodynamics were seen, with heart rate reduction, an increase in mean blood pressure, a reduction in arterial lactate, and reduced conventional inotrope use. Levosimendan was safely used in a small number of pediatric patients with established low cardiac output state who demonstrated improved hemodynamics and tissue perfusion, with a tendency to reduced conventional inotrope usage, and this warrants its evaluation as an inotrope in the pediatric population.

Myocardial water handling and the role of aquaporins

Cardiac surgery is performed in approximately 770,000 adults and 30,000 children in the United States of America annually. In this review we outline the mechanistic links between post-operative myocardial stunning and the development of myocardial edema. These interrelated processes cause a decline in myocardial performance that account for significant morbidity and mortality after cardiac surgery. Factors leading to myocardial edema include hemodilution, ischemia and reperfusion as well as osmotic gradients arising from pathological change. Several members of the aquaporin family of water transport proteins have been described in the myocardium although their role in the pathogenesis and resolution of cardiac edema is not established. This review examines evidence for the involvement of aquaporins in myocardial water handling during normal and pathological conditions.

Recent developments in the perioperative management of the paediatric cardiac patient

PURPOSE OF REVIEW

Survival of infants born with complex cardiac anomalies has dramatically improved, and the growing population of patients with congenital heart disease reaching adulthood has resulted in an increased incidence of long-term complications related to the perioperative period. This review focuses on recent advances in strategies to prevent, detect, treat, or predict early and late complications arising from open heart surgery for congenital heart disease.

RECENT FINDINGS

Aprotinine and recombinant factor VIIa may effectively reduce the risk of excessive perioperative bleeding, and the use of steroids, complement component C4A, heparin-coated circuits, and modified ultrafiltration may play a role in the control of the postoperative inflammatory response. Milrinone is becoming increasingly popular in the prevention and treatment of the reduced postoperative cardiac output, and extracorporeal life support has become a well established and successful form of support for postoperative myocardial dysfunction, even in the functionally univentricular heart. In recent years interest increased in optimizing myocardial protection using contents-differentiated and temperature-differentiated blood cardioplegia and in optimizing cerebral protection using a higher haematocrit during bypass and by using selective regional perfusion in favour of circulatory arrest.

SUMMARY

Hearts can be mended, but salvation of hearts and brains needs further rigorous attention.

Remote ischaemic preconditioning protects against cardiopulmonary bypass-induced tissue injury: a preclinical study

OBJECTIVES

To test the hypothesis that remote ischaemic preconditioning (rIPC) reduces injury after cardiopulmonary bypass (CPB).

DESIGN

Randomised study with an experimental model of CPB (3 h CPB with 2 h of cardioplegic arrest). Twelve 15 kg pigs were randomly assigned to control or rIPC before CPB and followed up for 6 h.

INTERVENTION

rIPC was induced by four 5 min cycles of lower limb ischaemia before CPB.

MAIN OUTCOME MEASURES

Troponin I, glial protein S-100B, lactate concentrations, load-independent indices (conductance catheter) of systolic and diastolic function, and pulmonary resistance and compliance were measured before and for 6 h after CPB.

RESULTS

Troponin I increased after CPB in both groups but during reperfusion the rIPC group had lower concentrations than controls (mean area under the curve -57.3 (SEM 7.3) v 89.0 (11.6) ng.h/ml, p = 0.02). Lactate increased after CPB in both groups but during reperfusion the control group had significantly more prolonged hyperlactataemia (p = 0.04). S-100B did not differ between groups. Indices of ventricular function did not differ. There was a tendency to improved lung compliance (p = 0.07), and pulmonary resistance changed less in the rIPC than in the control group during reperfusion (p = 0.02). Subsequently, peak inspiratory pressure was lower (p = 0.001).

CONCLUSION

rIPC significantly attenuated clinically relevant markers of myocardial and pulmonary injury after CPB. Transient limb ischaemia as an rIPC stimulus has potentially important clinical applications.

Systemic and Pulmonary Effects of Vasopressors and Inotropes in the Neonate

This paper briefly reviews the systemic and pulmonary hemodynamic actions of the most frequently used vasopressor-inotropes and inotropes in the preterm and term neonate. It is important to note that very little is known about the medium- and long-term cardiovascular and neurodevelopmental benefits of the use of these medications in the neonate.

Preservation of mitochondrial structure and function after cardioplegic arrest in the neonate using a selective mitochondrial KATP channel opener

BACKGROUND

Mitochondrial dysfunction may contribute to early postoperative neonatal heart dysfunction. Diazoxide, a mitochondrial-selective adenosine triphosphate-sensitive potassium-channel opener, is associated with mitochondrial preservation after cardioplegic arrest. We evaluated the mitochondrial-protective effect of diazoxide in terms of mitochondrial structure and function after neonatal cardioplegic arrest.

METHODS

Newborn piglets (age, approximately 14 days) underwent cardiopulmonary bypass and 60 minutes of cardioplegic arrest using cold crystalloid cardioplegic solution (CCP, n = 5) or cold crystalloid cardioplegic solution with diazoxide (CCP+D, n = 5). After 6 hours of recovery, myocardium was harvested. Control myocardium from piglets that did not undergo cardiopulmonary bypass (non-CPB, n = 5) was obtained.

RESULTS

Cardioplegic arrest was associated with translocation of Bax to the mitochondria, which was not prevented by diazoxide. Nevertheless, by electron microscopy, CCP-associated remodeling of mitochondrial structure was subjectively diminished in CCP+D hearts. In addition, CCP-associated mitochondrial permeabilization and cytochrome c release into the cytosol were prevented with CCP+D (p < 0.05). In vitro oxygen consumption of isolated mitochondria demonstrated deficient function of mitochondrial complex I in CCP, but it was preserved in the CCP+D myocardial mitochondria (p < 0.05). Complex II and IV activity was not different among groups. In parallel with impaired complex I function, the cardiac adenosine triphosphate content was diminished in CCP hearts, but well maintained in CCP+D hearts (p < 0.05).

CONCLUSIONS

Although early apoptotic signaling events (Bax translocation) are not prevented by diazoxide, addition of the mitochondrial-selective adenosine triphosphate-sensitive potassium-channel opener to the cardioplegic solution is associated with protection of mitochondrial structural and functional integrity in a clinically relevant model of neonatal cardiac surgery. The mitochondrial-protective effects of diazoxide may contribute to improved postoperative myocardial function in the neonate.

The International Liaison Committee on Resuscitation (ILCOR) consensus on science with treatment recommendations for pediatric and neonatal patients: pediatric basic and advanced life support

This publication contains the pediatric and neonatal sections of the 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations (COSTR). The consensus process that produced this document was sponsored by the International Liaison Committee on Resuscitation (ILCOR). ILCOR was formed in 1993 and consists of representatives of resuscitation councils from all over the world. Its mission is to identify and review international science and knowledge relevant to cardiopulmonary resuscitation (CPR) and emergency cardiovascular care (ECC) and to generate consensus on treatment recommendations. ECC includes all responses necessary to treat life-threatening cardiovascular and respiratory events. The COSTR document presents international consensus statements on the science of resuscitation. ILCOR member organizations are each publishing resuscitation guidelines that are consistent with the science in this consensus document, but they also take into consideration geographic, economic, and system differences in practice and the regional availability of medical devices and drugs. The American Heart Association (AHA) pediatric and the American Academy of Pediatrics/AHA neonatal sections of the resuscitation guidelines are reprinted in this issue of Pediatrics (see pages e978-e988). The 2005 evidence evaluation process began shortly after publication of the 2000 International Guidelines for CPR and ECC. The process included topic identification, expert topic review, discussion and debate at 6 international meetings, further review, and debate within ILCOR member organizations and ultimate approval by the member organizations, an Editorial Board, and peer reviewers. The complete COSTR document was published simultaneously in Circulation (International Liaison Committee on Resuscitation. 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Circulation. 2005;112(suppl):73-90) and Resuscitation (International Liaison Committee on Resuscitation. 2005 International Consensus Conference on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Resuscitation. 2005;67:271-291). Readers are encouraged to review the 2005 COSTR document in its entirety. It can be accessed through the CPR and ECC link at the AHA Web site: www.americanheart.org. The complete publication represents the largest evaluation of resuscitation literature ever published and contains electronic links to more detailed information about the international collaborative process. To organize the evidence evaluation, ILCOR representatives established 6 task forces: basic life support, advanced life support, acute coronary syndromes, pediatric life support, neonatal life support, and an interdisciplinary task force to consider overlapping topics such as educational issues. The AHA established additional task forces on stroke and, in collaboration with the American Red Cross, a task force on first aid. Each task force identified topics requiring evaluation and appointed international experts to review them. A detailed worksheet template was created to help the experts document their literature review, evaluate studies, determine levels of evidence, develop treatment recommendations, and disclose conflicts of interest. Two evidence evaluation experts reviewed all worksheets and assisted the worksheet reviewers to ensure that the worksheets met a consistently high standard. A total of 281 experts completed 403 worksheets on 275 topics, reviewing more than 22000 published studies. In December 2004 the evidence review and summary portions of the evidence evaluation worksheets, with worksheet author conflict of interest statements, were posted on the Internet at www.C2005.org, where readers can continue to access them. Journal advertisements and e-mails invited public comment. Two hundred forty-nine worksheet authors (141 from the United States and 108 from 17 other countries) and additional invited experts and reviewers attended the 2005 International Consensus Conference for presentation, discussion, and debate of the evidence. All 380 participants at the conference received electronic copies of the worksheets. Internet access was available to all conference participants during the conference to facilitate real-time verification of the literature. Expert reviewers presented topics in plenary, concurrent, and poster conference sessions with strict adherence to a novel and rigorous conflict of interest process. Presenters and participants then debated the evidence, conclusions, and draft summary statements. Wording of science statements and treatment recommendations was refined after further review by ILCOR member organizations and the international editorial board. This format ensured that the final document represented a truly international consensus process. The COSTR manuscript was ultimately approved by all ILCOR member organizations and by an international editorial board. The AHA Science Advisory and Coordinating Committee and the editor of Circulation obtained peer reviews of this document before it was accepted for publication. The most important changes in recommendations for pediatric resuscitation since the last ILCOR review in 2000 include: Increased emphasis on performing high quality CPR: "Push hard, push fast, minimize interruptions of chest compression; allow full chest recoil, and don't provide excessive ventilation" Recommended chest compression-ventilation ratio: For lone rescuers with victims of all ages: 30:2 For health care providers performing 2-rescuer CPR for infants and children: 15:2 (except 3:1 for neonates) Either a 2- or 1-hand technique is acceptable for chest compressions in children Use of 1 shock followed by immediate CPR is recommended for each defibrillation attempt, instead of 3 stacked shocks Biphasic shocks with an automated external defibrillator (AED) are acceptable for children 1 year of age. Attenuated shocks using child cables or activation of a key or switch are recommended in children <8 years old. Routine use of high-dose intravenous (IV) epinephrine is no longer recommended. Intravascular (IV and intraosseous) route of drug administration is preferred to the endotracheal route. Cuffed endotracheal tubes can be used in infants and children provided correct tube size and cuff inflation pressure are used. Exhaled CO2 detection is recommended for confirmation of endotracheal tube placement. Consider induced hypothermia for 12 to 24 hours in patients who remain comatose following resuscitation. Some of the most important changes in recommendations for neonatal resuscitation since the last ILCOR review in 2000 include less emphasis on using 100% oxygen when initiating resuscitation, de-emphasis of the need for routine intrapartum oropharyngeal and nasopharyngeal suctioning for infants born to mothers with meconium staining of amniotic fluid, proven value of occlusive wrapping of very low birth weight infants <28 weeks' gestation to reduce heat loss, preference for the IV versus the endotracheal route for epinephrine, and an increased emphasis on parental autonomy at the threshold of viability. The scientific evidence supporting these recommendations is summarized in the neonatal document (see pages e978-e988).

Population Pharmacokinetics of Milrinone in Neonates with Hypoplastic Left Heart Syndrome Undergoing Stage I Reconstruction

We performed a blinded, randomized pharmacokinetic study of milrinone in 16 neonates with hypoplastic left heart undergoing stage I reconstruction to determine the impact of cardiopulmonary bypass and modified ultrafiltration on drug disposition and to define the drug exposure during a continuous IV infusion of drug postoperatively. Neonates received an initial dose of either a 100 or 250 microg/kg of milrinone into the cardiopulmonary bypass circuit at the start of rewarming. Postoperatively, milrinone was infused to clinical needs. A mixed-effect modeling approach was used to characterize milrinone pharmacokinetics during cardiopulmonary bypass, modified ultrafiltration, and postoperatively using the NONMEM algorithm. All patients in this study demonstrated a modified ultrafiltration concentrating effect that occurred despite a modified ultrafiltration drug clearance of 3.3 mL x kg(-1) x min(-1). The infants in this study demonstrated an impaired renal clearance during the immediate postoperative period. A constant infusion of 0.5 microg x kg(-1) x min(-1) resulted in drug accumulation during the initial 12 h of drug administration. Postoperatively, milrinone clearance was significantly impaired (0.4 mL x kg(-1) x min(-1)), improved by the 12th postoperative hour, and approached steady-state clearance (2.6 mL x kg(-1) x min(-1)) by postoperative day 4. In the postoperative setting of markedly impaired renal function, an infusion rate of 0.2 microg x kg(-1) x min(-1) should be considered.

Pilot study of milrinone for low systemic blood flow in very preterm infants

OBJECTIVES

To examine the hemodynamic effects of milrinone given prophylactically to very preterm infants at high risk of low superior vena cava (SVC) flow and to investigate the preliminary efficacy and safety of an optimal dose.

STUDY DESIGN

This was a prospective, open-label study in two stages. The first involved dose escalation in two cohorts. Milrinone infusions of 0.25 microg/kg per minute (n = 8) and then 0.5 microg/kg per minute (n = 11) were administered from 3 to 24 hours of age. Population pharmacokinetic modeling was used to develop an optimized dose regimen. Ten infants then were loaded with 0.75 microg/kg per minute for 3 hours, followed by 0.2 microg/kg per minute maintenance until 18 hours of age. Infants were monitored for blood pressure, serial echocardiograms, and blood milrinone levels. The primary outcome was maintenance of SVC flow greater than 45 mL/kg per minute through the first 24 hours.

RESULTS

Low SVC flow developed in 36% of babies at both 0.25 microg/kg per minute and 0.5 microg/kg per minute of milrinone. Blood levels on these two regimens were slow to reach the target range and accumulated above this range by 24 hours. At 0.75 to 0.2 microg/kg per minute, no infant had SVC flow below 45 mL/kg per minute, compared with 61% in historic control subjects. Four infants needed an additional inotrope to support blood pressure. Blood levels were within the target range in 9 of 10 babies.

CONCLUSIONS

We used population pharmacokinetic modeling to develop an optimal dosing regimen for milrinone. The efficacy and safety in this novel preventative approach to circulatory support is encouraging but inconclusive. We do not recommend the use of milrinone in preterm infants outside a research setting.

Alterations in plasma B-type natriuretic peptide levels after repair of congenital heart defects: A potential perioperative marker

OBJECTIVES

B-type natriuretic peptide, a cardiac hormone with diuretic, natriuretic, and vasoactive properties, is used in the diagnosis, risk stratification, and management of adult cardiac patients. However, no study has yet determined the prognostic value of B-type natriuretic peptide after surgical intervention for congenital heart disease. The objectives of this study were (1) to determine alterations in B-type natriuretic peptide levels after repair of congenital heart disease with cardiopulmonary bypass and (2) to investigate potential associations between B-type natriuretic peptide levels and outcomes in this patient population.

METHODS

Fifty-one infants and children undergoing repair of congenital heart disease were studied. B-type natriuretic peptide levels were measured before and after surgical intervention, and the ability of the postoperative 12-hour B-type natriuretic peptide level to predict postoperative outcomes was evaluated.

RESULTS

B-type natriuretic peptide levels increased after separation from cardiopulmonary bypass, with an 8-fold peak increase at 12 hours (P < .005). Postoperative 12-hour B-type natriuretic peptide levels were associated with the duration of mechanical ventilation and the presence of a low cardiac output state after surgical intervention. On multivariate analysis, the 12-hour B-type natriuretic peptide level was an independent predictor of the duration of mechanical ventilation. In fact, B-type natriuretic peptide levels of greater than 540 pg/mL predicted mechanical ventilation beyond 48 hours, with a sensitivity of 88.9% and a specificity of 82.5%. In addition, B-type natriuretic peptide levels of greater than 815 pg/mL predicted the presence of a low cardiac output state within 48 hours after surgical intervention, with a sensitivity of 87.5% and a specificity of 90.2%.

CONCLUSIONS

B-type natriuretic peptide determinations might be a useful tool for clinicians caring for infants and children after surgical intervention for congenital heart disease.

Intracardiac temperature monitoring in infants after cardiac surgery

BACKGROUND

Hyperthermia after cerebral ischemia is associated with worse neurologic outcome. Our goals were 3-fold: (1) to describe the postoperative temperature course in infants after cardiac surgery, (2) to compare intracardiac temperature monitoring with traditional monitoring in infants, and (3) to determine variables that influence the patients' temperatures.

METHODS

Longitudinal temperature data were collected for 100 infants undergoing cardiac surgery. Intra-atrial, nasopharyngeal, esophageal, rectal, and axillary temperatures were recorded in all patients.

RESULTS

The mean age at the time of operation was 128 +/- 166 days, and the mean weight was 5.1 +/- 2.4 kg. Circulatory arrest was used for 54 patients. In the operating room, the maximum intra-atrial temperature (37.5 degrees C +/- 0.6 degrees C) was significantly greater than both the simultaneous esophageal temperature (36.9 degrees C +/- 1.9 degrees C, P = .03) and nasopharyngeal temperature (36.3 degrees C +/- 2.5 degrees C, P < .001). In the cardiac intensive care unit, intra-atrial temperature was significantly greater than both axillary and rectal temperatures. During the first 24 postoperative hours, intra-atrial temperature was greater than 38 degrees C in 48 (48%) patients, rectal temperature was greater than 38 degrees C in 36 (36%) patients, and axillary temperature was greater than 38 degrees C in 7 (7%) patients.

CONCLUSIONS

In patients less than 2 years of age undergoing cardiac surgery requiring cardiopulmonary bypass, intra-atrial temperature peaked 4 to 6 hours after leaving the operating room. Traditional methods of temperature monitoring significantly underestimate core temperature after cardiac surgery in infants. Use of intracardiac temperature monitoring might result in avoidance of cerebral hyperthermia.

Current insights regarding neurological and developmental abnormalities in children and young adults with complex congenital cardiac disease

Over a decade ago, I co-authored a review in Cardiology in the Young regarding neurological outcomes following surgery for congenital cardiac disease.1In that review, I placed much emphasis on the conduct of cardiopulmonary bypass, and its role in neurodevelopmental disabilities. Much has been learned in the intervening years regarding the multifactorial causes of abnormal school-age development, in particular, the role of prenatal, perioperative, socioeconomic, and genetic influences. In this update, I will highlight some of the recent advances in our understanding of the protean causes of neurological, behavioral, and developmental abnormalities in children and young adults with complex forms of congenital cardiac disease. In addition, I will summarize the current data on patients at particular high-risk for adverse neurodevelopmental outcomes, specifically those with a functionally univentricular heart who have had staged reconstruction with ultimate conversion to the Fontan circulation.

Perioperative management of patients with poorly functioning ventricles in the setting of the functionally univentricular heart

The patient with a functionally univentricular heart is at increased risk for ventricular dysfunction for a variety of reasons. At birth, the pulmonary and systemic circulations are in parallel, leading to pulmonary overcirculation and a volume-loaded functional ventricle. Significant atrioventricular valvar regurgitation, abnormal ventriculoarterial coupling, diastolic dysfunction, and altered ventricular geometry can also contribute to long-term ventricular dysfunction. These collected circumstances place the patient at increased risk for perioperative morbidity and mortality. We will discuss in this review the pathophysiology that leads to ventricular dysfunction at each stage of surgical palliation, as well as the strategies for perioperative management. In addition, we will highlight novel strategies for management of ventricular dysfunction.

Neonatal Persistent Pulmonary Hypertension Treated with Milrinone: Four Case Reports

Current standard therapy for persistent pulmonary hypertension of the newborn (PPHN) consists of optimal lung inflation, hemodynamic support and selective vasodilation with inhaled nitric oxide (iNO). However, not all infants will respond. Milrinone, a phosphodiesterase (PDE) III inhibitor, is routinely used in pediatric cardiac intensive care units to improve inotropy and reduce afterload. Although its use in post-operative cardiac failure has been proven in a randomized trial, it has not been reported to be beneficial in PPHN. We report four cases with severe PPHN treated with a combination of iNO and Milrinone. All four cases were unresponsive to therapy including iNO, with a mean oxygenation index (OI) of 40 (standard deviation (SD) 12)) before Milrinone. Substantial improvement in OI (mean of 28; SD 16) was followed by extubation and survival. However, of 4 patients, 2 developed serious intraventricular hemorrhages (IVHs), and 1 had a small IVH. To clarify the risk benefit ratio, of death versus survival with impairment, a randomized controlled trial is needed.

Hyperchloraemic metabolic acidosis following open cardiac surgery

AIMS

To describe acid-base derangements in children following open cardiac surgery on cardiopulmonary bypass (CPB), using the Fencl-Stewart strong ion approach.

METHODS

Prospective observational study set in the paediatric intensive care unit (PICU) of a university children's hospital. Arterial blood gas parameters, serum electrolytes, strong ion difference, strong ion gap (SIG), and partitioned base excess (BE) were measured and calculated on admission to PICU.

RESULTS

A total of 97 children, median age 57 months (range 0.03-166), median weight 14 kg (range 2.1-50), were studied. Median CPB time was 80 minutes (range 17-232). Predicted mortality was 2% and there was a single non-survivor. These children showed mild metabolic acidosis (median standard bicarbonate 20.1 mmol/l, BE -5.1 mEq/l) characterised by hyperchloraemia (median corrected Cl 113 mmol/l), and hypoalbuminaemia (median albumin 30 g/l), but no significant excess unmeasured anions or cations (median SIG 0.7 mEq/l). The major determinants of the net BE were the chloride and albumin components (chloride effect -4.8 mEq/l, albumin effect +3.4 mEq/l). Metabolic acidosis occurred in 72 children (74%) but was not associated with increased morbidity. Hyperchloraemia was a causative factor in 53 children (74%) with metabolic acidosis. Three (4%) hyperchloraemic children required adrenaline for inotropic support, compared to eight children (28%) without hyperchloraemia. Hypoalbuminaemia was associated with longer duration of inotropic support and PICU stay.

CONCLUSIONS

In these children with low mortality following open cardiac surgery, hypoalbuminaemia and hyperchloraemia were the predominant acid-base abnormalities. Hyperchloraemia was associated with reduced requirement for adrenaline therapy. It is suggested that hyperchloraemic metabolic acidosis is a benign phenomenon that should not prompt escalation of haemodynamic support. By contrast, hypoalbuminaemia, an alkalinising force, was associated with prolonged requirement for intensive care.

Management of the Pediatric Postoperative Cardiac Surgery Patient

Optimal management of the postoperative pediatric cardiac surgical patient requires a thorough understanding of patient anatomy, physiology, surgical repair or palliation, and clinical condition. This necessitates a dedicated team of clinicians including skilled nurses, physicians, and respiratory therapists specialized in the care of patients who have complex congenital heart disease. This article provides an overview of the multisystemic risk factors and consequences associated with cadiopulmonary bypass and cardiac surgery. An evaluation of cardiac hemodynamics and a review of major organ systems are included. Essential assessment information and interventional strategies for managing the pediatric postoperative cardiac surgery patient are detailed.

Cardiovascular drugs for the newborn

This article reviews the various cardiovascular drugs for newborns, including antiarrhythmics, antihypertensives, inotropes, and pulmonary vasodilators. Antiarrhythmic drugs are classified according to their mechanisms of action, such as effects on ion channels, duration of repolarization, and receptor interaction, which help with understanding the effects of individual antiarrhythmic drugs and selection of drugs for specific arrhythmias. Drug treatment for hypertension should start with a single drug from one of the following classes: ACE inhibitors, angiotensin-receptor antagonists, beta-receptor antagonists, calcium channel blockers, or diuretics. The inotropic drug should be selected according to its specific pharmacologic properties and the specific cardiovascular abnormality to be corrected. An effective pulmonary vasodilator must dilate the pulmonary vasculature more than the systemic vasculature.

In vivo dilatation of the fetal and postnatal ductus arteriosus by inhibition of phosphodiesterase 3 in rats

BACKGROUND

Clinically, it appears that phosphodiesterase 3 (PDE 3) inhibitors, which are used for acute cardiac failure in premature infants, dilate the ductus arteriosus (DA).

OBJECTIVES

To clarify the ductus-dilating effects of PDE 3 inhibitors in near-term rat pups and their differential effects in near-term and preterm fetal rats, in in vivo studies.

METHODS

The in vivo ductal diameter of rat pups and fetuses was measured using a rapid whole-body freezing method, by cutting on a freezing microtome and measuring with a microscope and micrometer. Eight to twenty pups and fetuses were studied in each group. Milrinone and amrinone (specific inhibitors of PDE 3) were injected into 1-hour-old pups and the DA was studied 0.5 and 1 h later. The differential effects of these PDE 3 inhibitors on the near-term and preterm ductus were studied by injecting indomethacin (10 mg/kg) and PDE 3 inhibitors into 21D (21st day of pregnancy: term-21.5 days) and 19D dams and studying the fetal ductus 4 and 8 h later.

RESULTS

Milrinone and amrinone dilated the postnatal ductus dose-dependently. Large doses of these drugs dilated it completely, and clinically equivalent doses dilated it minimally. Milrinone and amrinone prevented constriction of the fetal ductus by indomethacin. Their ductus-dilating effects were more potent in the preterm than in the near-term fetuses, and clinically equivalent doses of these PDE 3 inhibitors dilated preterm ductus completely.

CONCLUSION

In rats, PDE 3 inhibitors reopen the constricted postnatal DA slightly. PDE 3 inhibitors dilate the fetal DA constricted with indomethacin effectively and more sensitively in preterm than in near-term fetuses.

A randomized, double-blind, placebo-controlled pilot trial of triiodothyronine in neonatal heart surgery

OBJECTIVE

This study was undertaken to evaluate the effect of triiodothyronine replacement on the early postoperative course of neonates undergoing aortic arch reconstruction.

METHODS

We performed a randomized, double-blind, placebo-controlled trial of triiodothyronine supplementation in neonates undergoing either a Norwood procedure or two-ventricle repair of interrupted aortic arch and ventricular septal defect. Patients were assigned to receive a continuous infusion of triiodothyronine (0.05 micro/kg/h) or placebo for 72 hours after cardiopulmonary bypass. Primary end points were a composite clinical outcome score and cardiac index at 48 postoperative hours.

RESULTS

We enrolled 42 patients (triiodothyronine n = 22, placebo n = 20). Baseline characteristics were similar in the treatment groups. Study drug was discontinued prematurely because of hypertension (n = 1) and ectopic atrial tachycardia (n = 1), both cases in the triiodothyronine group. Free and total triiodothyronine levels were higher in the triiodothyronine group than in the placebo group at 24, 48, and 72 postoperative hours (P < .001). The median clinical outcome scores were 2.0 (range 0-4) with triiodothyronine and 2.0 (range 0-7) with placebo (P = .046). Compared with those in the placebo group, neonates assigned to triiodothyronine had shorter median time to negative fluid balance (2.0 vs 2.5 days, P = .027). Cardiac index values were 2.11 +/- 0.64 L/min x m2 with triiodothyronine and 2.05 +/- 0.72 L/min x m2 with placebo (P = .81). Heart rate and diastolic blood pressure were not influenced by triiodothyronine supplementation, but systolic blood pressure was higher in the triiodothyronine group (P < .001). No serious adverse events were attributed to triiodothyronine administration.

CONCLUSION

Triiodothyronine supplementation was safe and resulted in more rapid achievement of negative fluid balance after aortic arch reconstruction. Cardiac index at 48 hours was not significantly improved.

Hemodynamic effects of rescue protocol hydrocortisone in neonates with low cardiac output syndrome after cardiac surgery

OBJECTIVE

To assess the hemodynamic effects and safety of hydrocortisone in neonates with low cardiac output syndrome requiring high levels of inotropic support and fluid resuscitation after cardiac surgery.

DESIGN

Retrospective chart review.

SETTING

Fifteen-bed pediatric cardiovascular intensive care unit.

PATIENTS

Twelve neonates with low cardiac output syndrome after cardiac surgery to whom hydrocortisone was administered according to one of two dosing regimens (100 mg/[m.day] for 2 days, 50 mg/[m.day] for 2 days, and 25 mg/[m.day] for 1 day or 100 mg/[m.day] for 1 day, 50 mg/[m.day] for 2 days, and 25 mg/[m.day] for 2 days) were identified from the Department of Pharmacy database between September 2002 and January 2004.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The mean and systolic blood pressure increased significantly 3 hrs after hydrocortisone treatment from the values preceding hydrocortisone administration. The mean blood pressure increased from 44.0+/-3.0 to 55.4+/-2.3 mm Hg (p=.01) and the systolic blood pressure increased from 64.2+/-4.7 to 78.3+/-3.4 mm Hg (p=.04). Comparable beneficial changes were also seen in the heart rate, which decreased from 168.3+/-4.6 to 148.3+/-5.6 beats/min (p=.004) after 24 hrs of hydrocortisone administration and remained at this level during the 72 hrs of follow-up. Significant weaning of epinephrine infusions was possible, from a mean dose of 0.16 to 0.06 microg/(kg.min) (p=.008), within 24 hrs after the initiation of steroid administration, and this reduction was not offset by increases in other inotropic agents. hydrocortisone administration caused nonsignificant increases in mean blood glucose concentration (from 116.2+/-20.6 to 156.0+/-25.6 mg/dL; p=.64), mean white blood cell count (from 16.6+/-1.6 to 18.9+/-2.6 x 10 U/L; p=.35), and sodium level (from 144.7+/-1.3 to 145.3+/-1.3 mmol/L; p=.51). Ten of the 12 patients (83.3%) survived.

CONCLUSION

Most of the hemodynamically compromised neonates who were unresponsive to high doses of inotropic agents and fluid resuscitation after heart surgery responded to hydrocortisone with improvement of hemodynamic parameters and a decrease in inotropic requirements.

Differential pharmacologic sensitivities of phosphodiesterase-3 inhibitors among human isolated gastroepiploic, internal mammary, and radial arteries

Systematic investigations of the actions of phosphodiesterase (PDE)-3 inhibitors on different human vascular tissues have not been performed. We investigated the effects of specific PDE-3 inhibitors (olprinone, milrinone, and amrinone) on contracted human gastroepiploic arteries (n = 70), internal mammary arteries (n = 72), and radial arteries (n = 70) harvested from a total of 134 patients, all of whom were undergoing coronary artery bypass surgery. Each of these PDE-3 inhibitors dose-dependently diminished the contractile responses to 10(-6) mol/L norepinephrine and to either 10(-9) or 10(-8) mol/L of the thromboxane A2 analog U46619. In inducing vasorelaxations, these inhibitors were significantly more potent in norepinephrine-contracted rings than in those contracted with U46619. Further, at concentrations similar to the maximum therapeutic plasma concentrations (10(-7) mol/L olprinone; 10(-6) mol/L milrinone; 10(-5) mol/L amrinone) olprinone and milrinone were more potent at inducing relaxations than amrinone in gastroepiploic arteries and radial arteries, whereas in internal mammary arteries milrinone was more potent than the others. These results suggest different activities for the three PDE-3 inhibitors among human arteries located in different regions and may be informative about the effectiveness of these inhibitors in preventing spasms in the various arterial grafts used in revascularization.

IMPLICATIONS

Because three phosphodiesterase-3 inhibitors (milrinone, olprinone, and amrinone) differed in their vasodilator potencies (against the contractile response to either norepinephrine or a thromboxane A2 analog) among human arteries removed from different parts of the body, their vascular relaxation profiles should be considered before they are used clinically.

Nesiritide in infants and children with congestive heart failure

OBJECTIVES

Nesiritide (synthetic B-type natriuretic peptide) has been shown to be effective in the management of acute decompensated heart failure in adults. The role of nesiritide in pediatric heart failure has not been examined. In the present study, we reviewed our initial experience with nesiritide in children with primary heart failure or low cardiac output after heart surgery.

METHODS

Nesiritide was administered in an open-label fashion to patients with heart failure who were already receiving inotropic and diuretic therapy. Between July 2003 and August 2004, 30 patients aged 5 days to 16.7 yrs (median age, 4.6 months) received nesiritide therapy. Diagnoses included single-ventricle congenital defect (n = 5), two-ventricle congenital defect (n = 13), heart transplant (n = 5), and dilated cardiomyopathy (n = 7). Sixteen patients were started on nesiritide within 2 wks of corrective or palliative heart surgery. The majority of subjects (n = 24) received an initial bolus dose. Continuous infusion dosage ranged between 0.005 and 0.02 microg.kg.min. Nesiritide was discontinued for possible side effects in two patients (arrhythmia and hypotension). Duration of therapy ranged from 1 to 24 days (median, 4 days).

RESULTS

Administration of nesiritide was associated with improvement in fluid balance from positive 0.8 +/- 1.9 mL.kg.hr at baseline to negative 0.3 +/- 1.8 mL.kg.hr after 24 hrs of therapy (p = .02). There was a nonsignificant trend toward a reduction in right atrial pressure (9.2 +/- 3.9 vs. 11.2 +/- 4.1, p = .08).

CONCLUSIONS

Nesiritide is well tolerated in children with heart failure and is associated with improved diuresis. Further prospective studies will be needed to compare nesiritide with other vasoactive agents and examine the cost-efficacy of this therapy.

Milrinone and low cardiac output following cardiac surgery in infants: is there a direct myocardial effect?

We assessed the effect of milrinone on myocardial function in pediatric patients with postoperative low cardiac output syndrome by index of myocardial performance in a prospective, open-label, nonrandomized, consecutive study. Fifteen patients with low cardiac output syndrome following cardiac surgical treatment were studied in the tertiary cardiothoracic pediatric intensive care unit between April 2001 and November 2003 (age range, 0.2-16 months; median, 7; weight, 2.7-11.8 kg; median, 5). Echocardiographic, Doppler-derived, time interval-based index of myocardial performance (Tei index) was used to study cardiac function prior to and while on intravenous milrinone treatment for 18-24 hours. Treatment with milrinone led to improvement in biventricular myocardial function [mean right ventricular index from 0.521 (SD-0.213) to 0.385 (SD-0.215), p = 0.003; mean left ventricular index from 0.636 (SD-0.209) to 0.5 (SD-0.171), p = 0.012). No difference was found in the values of heart rate corrected right or left ventricular ejection time prior to and while on treatment with milrinone (right ventricle: mean, 1.23 (SD-0.42) and 1.14 (SD-0.48), p = 0.29; left ventricles: mean, 1.17 (SD-0.51) and 1.13 (SD-0.48), p = 0.66) Our data support the direct myocardial effect of milrinone as part of the mechanism behind its already proven benefit in children with low cardiac output syndrome following cardiac surgery.