Stephen Horton

Experience with the Jostra Rotaflow and QuadroxD oxygenator for ECMO.

Since April 1988, we have been able to offer extracorporeal membrane oxygenation (ECMO) to patients who are either failing ventilation or who need cardiopulmonary support following cardiac surgery. During this time, we have supported 211 patients, the majority of whom have been supported with the Avecor (Affinity, Avecor Cardiovascular Inc., Minneapolis, MN, USA) spiral wound silicone-membrane oxygenator. Microporous hollow-fibre oxygenators have been used (18%) at our center. However, due to their early failure, they have necessitated conversion to a device that potentially would last for the entire ECMO course, i.e., Avecor and, subsequently, have not been used routinely until the introduction of the QuadroxD (Jostra Medizintechnik AG, Hirrlingen, Germany). The recent development of the poly-4-methyl-1-pentene diffusion membrane allows us to utilize hollow-fibre technology with a true (nonmicroporous) membrane. This has enabled us to use this low-resistance device with all its inherent advantages, without plasma leakage necessitating circuit changeover. From July 2000, we have used the QuadroxD oxygenator for our patients requiring ECMO support. This has been in patients with weights ranging from 2.16-51.0 kg (n = 23), with the longest support being for 1119 hours. This new technology has enabled us to utilize a single device for all patient sizes, so we now have an ECMO circuit set up at all times, minimizing the time required for support to be available, potentially improving survivor morbidity.

Reference values for kaolin-activated thromboelastography in healthy children.

BACKGROUND:The hemostatic system of children changes with age and differs significantly from the hemostatic system of adults. Age-specific reference values are therefore required for most hemostatic variables. Thromboelastography (TEG®) is a point-of-care coagulation test that may provide superior evaluation and management of coagulopathies after cardiac surgery, when large-dose unfractionated heparin is administered for cardiopulmonary bypass. In this study, we established reference values for kaolin-activated TEG in healthy children, to facilitate accurate interpretation of pediatric TEG results. METHODS:Kaolin-activated TEG was performed on 100 healthy children undergoing elective day surgery and 25 healthy adult volunteers. The following TEG variables were recorded: reaction time, coagulation time, &agr; angle, maximum amplitude, percentage lysis 30 min after maximum amplitude was reached, and the coagulation index. Differences between age-groups were evaluated using analysis of variance. RESULTS:Age-specific reference values for kaolin-activated TEG in healthy children between 1 mo and 16 yr of age are presented. No significant differences between children and adults were observed. CONCLUSIONS:TEG results, from a particular clinical setting, must be compared to age-specific, as well as analyzer- and activator-specific, reference values to allow for correct interpretation of the results. Reference values provided here will be of use in acute clinical situations where a practical monitor of hemostasis is required.

Centrifugal ventricular assist in children under 6 kg

OBJECTIVE The clinical application of centrifugal ventricular assist devices (VAD) has generally been limited to adults and large paediatric patients. In our experience neonates and small paediatric patients requiring ventricular support post-cardiopulmonary bypass are well supported by VAD. In this study we analyse our experience. METHODS We have examined the records of our VAD patients who weighed less than 6 kg. Thirty-four patients, ranging in age from 2 to 258 days (median 60 days) and weight from 1.9 to 5.98 kg (median 3.7 kg), underwent 35 VAD procedures. One patient was supported on VAD twice. RESULTS All patients had congenital heart lesions and were placed on VAD either because they could not be weaned from cardiopulmonary bypass after repair or palliation of the lesion (71.5%), or for support in the post-operative period due to refractory low cardiac output (28.5%). Twenty-two of the 35 VAD procedures (0.63, 95% CI: 0.45-0.78) resulted in successful weaning and decannulation, this was similar to the weaning probability for patients greater than 6 kg (P = 0.07). There were 10 late deaths in this group, with a 1-year KM survival of 0.31 (95% CI: 0.17-0.47). Most late deaths were related to irreversible cardiac disease processes as were the elective discontinuance of VAD outcomes. Neither weight, age, VAD duration, CPB duration, X clamp duration, univentricular anatomy or TGA anatomy predicted successful discharge from hospital (P > 0.05)--Weight P = 0.576; Age P = 0.532; VAD duration P = 0.181; CBP duration P = 0.549; X clamp duration P = 0.984; Univentricular anatomy P = 0.481; TGA anatomy P = 0.099. CONCLUSION We believe centrifugal ventricular assist is a realistic option in very small patients who require post-cardiopulmonary bypass support. It is relatively easy to establish and manage, the results, although showing no factors predictive of successful discharge, are encouraging.

Pump-induced haemolysis: a comparison of short-term ventricular assist devices

Centrifugal pumps are superior to roller pumps for extended support durations in terms of pump-induced haemolysis. In this study, we evaluated the commonly used Biomedicus BP 50 and compared it with the Jostra Rotaflow and a standard roller pump in an in vitro test circuit. Each circuit was run for a six-day period and repeated five times. Plasma haemoglobin values showed the roller pump to become more haemolytic than the Biomedicus (p = 0.022) and the Rotaflow. A statistically significant difference between the Biomedicus and the Rotaflow was observed on day six of the trial (p = 0.016), with the Rotaflow showing lower levels of haemolysis than the Biomedicus. These results support the use of the new generation centrifugal pump, the Rotaflow, as a suitable device for short-term ventricular assist.

Outcomes of Surgery for Simple Total Anomalous Pulmonary Venous Drainage in Neonates

BACKGROUND Repair of total anomalous pulmonary venous drainage (TAPVD) in neonates remains a challenge as it is often associated with severe obstruction. We describe a large cohort of neonates who underwent TAPVD repair at a single institution. METHODS From 1973 to 2008, 112 patients underwent simple TAPVD surgery during the first month of life. Data collection occurred retrospectively. RESULTS Preoperative pulmonary venous obstruction (PVO) occurred in 89 (79.5%) patients. There were 12 (10.7%) early deaths. Significant risk factors were bypass time greater than 65 minutes (p=0.014) and emergent surgery (p=0.005). Hospital mortality was unchanged throughout the 3 eras (1973 to 1988, 1989 to 1998, 1999 to 2008), despite an increase in patients with preoperative acidosis (p=0.004) and severe TAPVD obstruction (p=0.038) during the recent 10 years. There were 6 (6.25%) late deaths within 2 years of repair. Survival at 20 years was 83.4% (95% confidence interval 75 to 89). Risk factors for late death were operative weight 2.5 kg or less (p=0.004) and postoperative pulmonary hypertensive crisis (p=0.02). Reoperation for recurrent PVO was required in 13 patients (11.9%). Risk factors were operative weight 2.5 kg or less (p=0.035) and postoperative pulmonary hypertensive crisis (p=0.002). Follow-up was 96% complete and survivors (n=90) were asymptomatic at a median age of 11.7 years. CONCLUSIONS Hospital mortality remained unchanged over the 36-year period. Survival beyond 2 years offers excellent outcome. Risk factors for mortality were the preoperative clinical status, prolonged bypass time, persisting micro-obstruction, and low operative weight. A reduction in mortality will likely require development of effective medical management for patients who have peripheral PVO not amenable to surgical repair.

IL-6 and IL-8 Levels After Cardiopulmonary Bypass Are Not Affected by Surface Coating

UNLABELLED BACKGROUND.:Contact of blood with the surfaces of the cardiopulmonary bypass (CPB) circuit has been implicated as a cause of the inflammatory response. We undertook a prospective randomized trial of 200 pediatric patients, all with a calculated total bypass flow of less than 2.3 L/min (< 0.96 L/m2/min). METHODS Patients were randomly assigned to 1 of 4 CPB groups: (1) Nonheparin-bonded circuit with no albumin preprime; (2) Nonheparin-bonded circuit with albumin preprime; (3) Heparin-bonded circuit with no albumin preprime; (4) Heparin-bonded circuit with albumin preprime. Measurements of cytokines, (interleukin [IL]-6, IL-8) and blood cell counts were made prebypass and 6 and 24 hours after institution of cardiopulmonary bypass. RESULTS Analysis of variance showed no significant difference in any of the clinical or biochemical characteristics of the 4 groups. The interaction between heparin-bonded oxygenators and albumin preprime was not significant. No important differences in IL-6 or IL-8 concentrations were noted after CPB using either heparin or nonheparin-bonded oxygenators with albumin or albumin free preprime using two-way analysis of variance. CONCLUSIONS Albumin preprime and heparin-bonding do not attenuate the inflammatory response component attributable to the concentration of these markers.

Remote ischemic preconditioning in cyanosed neonates undergoing cardiopulmonary bypass: A randomized controlled trial

OBJECTIVE The myocardial protective effect of remote ischemic preconditioning has been demonstrated in heterogeneous groups of patients undergoing cardiac surgery. No studies have examined this technique in neonates. The present study was performed to examine the remote ischemic preconditioning efficacy in this high-risk patient group. METHODS A preliminary, randomized, controlled trial was conducted to investigate whether remote ischemic preconditioning in cyanosed neonates undergoing cardiac surgery confers protection against cardiopulmonary bypass. Two groups of neonates undergoing cardiac surgery were recruited for the present study: patients with transposition of the great arteries undergoing the arterial switch procedure and patients with hypoplastic left heart syndrome undergoing the Norwood procedure. The subjects were randomized to the remote ischemic preconditioning or sham control groups. Remote ischemic preconditioning was induced by four 5-minute cycles of lower limb ischemia and reperfusion using a blood pressure cuff. Troponin I and the biomarkers for renal and cerebral injury were measured pre- and postoperatively. RESULTS A total of 39 neonates were recruited-20 with transposition of the great arteries and 19 with hypoplastic left heart syndrome. Of the 39 neonates, 20 were randomized to remote ischemic preconditioning and 19 to the sham control group. The baseline demographics appeared similar between the randomized groups. The cardiopulmonary bypass and crossclamp times were not significantly different between the 2 groups. The troponin I levels were not significantly different at 6 hours after cardiopulmonary bypass nor were the postoperative inotrope requirements. Markers of renal (neutrophil gelatinase-associated lipocalin) and cerebral injury (S100b, neuron-specific enolase) were not significantly different between the 2 groups. CONCLUSIONS Our data suggest that remote ischemic preconditioning in hypoxic neonates undergoing cardiopulmonary bypass surgery does not provide myocardial, renal, or neuronal protection. Additional studies are needed to examine the relationships among developmental age, hypoxia, and the molecular mechanisms of ischemic preconditioning.

Long-Term Outcomes After Atrioventricular Valve Operations in Patients Undergoing Single-Ventricle Palliation

BACKGROUND Outcomes after atrioventricular (AV) valve operations in patients with functional single ventricles are unclear. METHODS From 1988 to 2010, 76 consecutive patients with single ventricles underwent AV valve operations for regurgitation at a single institution. Five replacements, 66 repairs, and 5 valve closures were performed at a median age of 1 year (range, 1 day-14 years) on 43 tricuspid, 9 mitral, and 24 common AV valves. RESULTS Hospital mortality was 17% (13/76). The follow-up was 100% complete. There were 15 late deaths. There were 48 survivors with a mean follow-up of 8.3±6 years. One- and 10-year Kaplan-Meier survival after AV valve operations was 72% (95% confidence interval [CI], 60%-81%) and 61% (95% CI, 48%-71%), respectively. Independent predictors of overall mortality were presence of a common AV valve (p=0.03), requirement for postoperative mechanical circulatory support (p=0.02), and timing of valve operations between initial palliation and performance of a bidirectional cavopulmonary shunt (BCPS) (p=0.047). Ten-year freedom from valve reoperation and from thromboembolic events of hospital survivors was 56% (95% CI, 38%-70%) and 70% (95% CI, 56%-80%), respectively. At last follow-up, 11 of 48 surviving patients (23%) had moderate to severe regurgitation, and pacemaker implantation was required in 6 patients. Only 34 patients reached the stage of Fontan completion. CONCLUSIONS AV valve regurgitation is a considerable burden for the patient with a single ventricle, especially when appearing at a young age. A quarter of patients died within the first year after operation, and they had considerable morbidity in terms of reoperation, thromboembolic events, and pacemaker implantation. Their chances of reaching Fontan completion seemed decreased.

Extracorporeal Membrane Oxygenation Circuitry

The extracorporeal membrane oxygenation circuit is made of a number of components that have been customized to provide adequate tissue oxygen delivery in patients with severe cardiac and/or respiratory failure for a prolonged period of time (days to weeks). A standard extracorporeal membrane oxygenation circuit consists of a mechanical blood pump, gas-exchange device, and a heat exchanger all connected together with circuit tubing. Extracorporeal membrane oxygenation circuits can vary from simple to complex and may include a variety of blood flow and pressure monitors, continuous oxyhemoglobin saturation monitors, circuit access sites, and a bridge connecting the venous access and arterial infusion limbs of the circuit. Significant technical advancements have been made in the equipment available for short- and long-term extracorporeal membrane oxygenation applications. Contemporary extracorporeal membrane oxygenation circuits have greater biocompatibility and allow for more prolonged cardiopulmonary support time while minimizing the procedure-related complications of bleeding, thrombosis, and other physiologic derangements, which were so common with the early application of extracorporeal membrane oxygenation. Modern era extracorporeal membrane oxygenation circuitry and components are simpler, safer, more compact, and can be used across a wide variety of patient sizes from neonates to adults.

Amplitude-Integrated Electroencephalography and Brain Injury in Infants Undergoing Norwood-Type Operations

BACKGROUND Perioperative brain injury is common in infants undergoing cardiac surgery. Amplitude-integrated electroencephalography (aEEG) provides real-time neurologic monitoring and can identify seizures and abnormalities of background cerebral activity. We aimed to determine the incidence of perioperative electrical seizures, and to establish the background pattern of aEEG, in neonates undergoing Norwood-type palliations for complex congenital heart disease in relation to outcome at 2 years. METHODS Thirty-nine full-term neonates undergoing Norwood-type operations underwent aEEG monitoring before and during surgery and for 72 hours postoperatively. The perfusion strategy included full-flow moderately hypothermic cardiopulmonary bypass with antegrade cerebral perfusion. Amplitude-integrated electroencephalography tracings were reviewed for seizure activity and background pattern. Survivors underwent neurodevelopmental outcome assessment using the Bayley Scales of Infant Development (3rd edition) at 2 years of age. RESULTS Thirteen (33%) infants had electrical seizures, including 9 with intraoperative seizures and 7 with postoperative seizures. Seizures were associated with significantly increased mortality, but not with neurodevelopmental impairment in survivors. Delay in recovery of the aEEG background beyond 48 hours was also associated with increased mortality and worse motor development. CONCLUSIONS Perioperative seizures were common in this cohort. Intraoperative seizures predominantly affected the left hemisphere during antegrade cerebral perfusion. Delayed recovery in aEEG background was associated with increased risk of early mortality and worse motor development. Ongoing monitoring is essential to determine the longer-term significance of these findings.