Venovenous perfusion in ECMO for newborn respiratory insufficiency. A clinical comparison with venoarterial perfusion

Device updates in pediatric and neonatal ECMO

Since the early use of extracorporeal life support (ECLS), new innovations and technological advancements have augmented the ability to use this technology in children and neonates. Cannulae have been re-designed to maintain structure and allow for single cannula venovenous (VV) ECLS in smaller patients. Circuit technology, including pumps and tubing, has evolved to permit smaller priming volumes and lower flow rates with fewer thrombotic or hemolytic complications. New oxygenator developments also improve efficiency of gas exchange. This paper serves as an overview of recent device developments in ECLS delivery to pediatric and neonatal patients.

Updates in Neonatal Extracorporeal Membrane Oxygenation and the Artificial Placenta

Extracorporeal life support, initially performed in neonates, is now commonly used for both pediatric and adult patients requiring pulmonary and/or cardiac support. Data suggests the clinical feasibility of Extracorporeal Membrane Oxygenation for premature infants (29-33 weeks estimated gestational age [EGA]). For extremely premature infants less than 28 weeks EGA, an artificial placenta has been developed to recreate the fetal environment. This approach is investigational but clinical translation is promising. In this article, we discuss the current state and advances in neonatal and "preemie Extracorporeal Membrane Oxygenation" and the development of an artificial placenta and its potential use in extremely premature infants.

Cannulation and decannulation techniques for neonatal ECMO

In neonates with cardiac and/or respiratory failure, extracorporeal membrane oxygenation (ECMO) continues to be an important method of respiratory and/or cardiovascular support where conventional treatments are failing. ECMO cannulation involves a complex decision-making process to choose the proper ECMO modality and cannulation strategy to match each patient's needs, unique anatomy, and potential complication profile. Initially, all ECMO support involved cannulating both the carotid artery and the internal jugular vein (IJV), known as veno-arterial (VA-ECMO) for cardiac and/or respiratory support. Rarely was cannulation through the chest used. The development of dual-lumen cannulae in the early to mid 1990s addressed the concerns about carotid artery ligation and its impact on neurological outcomes, and allowed single vascular access for veno-venous respiratory support (VV-ECMO). We present a review of cannulation and decannulation techniques for both VA and VV-ECMO in neonates.

Multisite Veno-Venous Cannulation for Neonates and Nonambulatory Children

OBJECTIVES

Neonates with respiratory failure are ideally supported with veno-venous rather than veno-arterial extracorporeal membrane oxygenation due to the reduced rate of neurologic complications. However, the proportion of neonates supported with veno-venous extracorporeal membrane oxygenation is declining. We report multisite veno-venous extracorporeal membrane oxygenation, accessing the neck, returning to the inferior vena cava via the common femoral vein in neonates and children less than 10 kg.

DESIGN

Retrospective case series with 1 year minimum follow-up.

PATIENTS

Patients less than 10 kg supported with veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein.

SETTING

A 30-bed pediatric intensive care delivering extracorporeal membrane oxygenation to approximately 20 children annually.

INTERVENTIONS

Veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein was delivered using two single lumen cannulae.

MEASUREMENTS AND MAIN RESULTS

January 2015 to August 2019, 11 patients underwent veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein with median weight of 3.6 kg (interquartile range 2.8-6.1 kg), and median corrected gestational age of 13 days (interquartile range, 2-175 d). The smallest patient weighed 2.1 kg. Seven patients had comorbidities. Extracorporeal membrane oxygenation was technically successful in all patients with median flows of 126 mL/kg/min (interquartile range, 120-138 mL/kg/min) and median arterial oxygenation saturation of 94% (interquartile range, 91-98%) at 24 hours. Nine survived to home discharge, and two were palliated. Common femoral vein occlusion was observed in all patients on ultrasound post decannulation. There was no clinical or functional deficit in the cannulated limb at follow-up, a minimum of 1 year post extracorporeal membrane oxygenation.

CONCLUSIONS

Veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein was performed safely in patients under 10 kg with the smallest patient weighing 2.1 kg. Although occlusion of the common femoral vein was observed in patients post decannulation, subsequent follow-up demonstrated no clinical implications. We challenge current practice that veno-venous extracorporeal membrane oxygenation accessing the jugular and returning to the femoral vein cannot be performed in nonambulatory patients and suggest that this strategy is preferred over veno-arterial extracorporeal membrane oxygenation in infants requiring extracorporeal membrane oxygenation for respiratory failure.

Hemodynamic performance limits of the neonatal Double-Lumen cannula

Venovenous extracorporeal membrane oxygenation (VV-ECMO) is the preferred surgical intervention for patients suffering from severe cardiorespiratory failure, also encountered in SARS-Cov-2 management. The key component of VV-ECMO is the double-lumen cannula (DLC) that enables single-site access. The biofluid dynamics of this compact device is particularly challenging for neonatal patients due to high Reynolds numbers, tricuspid valve location and right-atrium hemodynamics. In this paper we present detailed findings of our comparative analysis of the right-atrial hemodynamics and salient design features of the 13Fr Avalon Elite DLC (as the clinically preferred neonatal cannula) with the alternate Origen DLC design, using experimentally validated computational fluid dynamics. Highly accurate 3D-reconstructions of both devices were obtained through an integrated optical coherence tomography and micro-CT imaging approach. Both cannula configurations displayed complex flow structures inside the atrium, superimposed over predominant recirculation regimes. We found that the Avalon DLC performed significantly better than the Origen alternative, by capturing 80% and 94% of venous blood from the inferior and superior vena cavae, respectively and infusing the oxygenated blood with an efficiency of more than 85%. The micro-scale geometric design features of the Avalon DLC that are associated with superior hemodynamics were investigated through 14 parametric cannula configurations. These simulations showed that the strategic placement of drainage holes, the smooth infusion blood stream diverter and efficient distribution of the venous blood capturing area between the vena cavae are associated with robust blood flow performance. Nevertheless, our parametric results indicate that there is still room for further device optimization beyond the performance measurements for both Avalon and Origen DLC in this study. In particular, the performance envelope of malpositioned cannula and off-design conditions require additional blood flow simulations for analysis.

Conversion from Venovenous to Venoarterial Extracorporeal Membrane Oxygenation in Adults

No major study has been performed on the conversion from venovenous (VV) to venoarterial (VA) extracorporeal membrane oxygenation (ECMO) in adults. This single-center retrospective cohort study aimed to investigate the incidence, indication, and outcome in patients who converted from VV to VA ECMO. All adult patients (≥18 years) who commenced VV ECMO at our center between 2005 and 2018 were screened. Of 219 VV ECMO patients, 21% (n = 46) were converted to VA ECMO. The indications for conversion were right ventricular failure (RVF) (65%), cardiogenic shock (26%), and other (9%). In the converted patients, there was a significant increase in Sequential Organ Failure Assessment (SOFA) scores between admission 12 (9-13) and conversion 15 (13-17, p < 0.001). Compared to non-converted patients, converted patients also had a higher mortality rate (62% vs. 16%, p < 0.001) and a lower admission Respiratory Extracorporeal Membrane Oxygenation Survival Prediction (RESP) score (p < 0.001). Outcomes were especially unfavorable in those converted due to RVF. These results indicate that VA ECMO, as opposed to VV ECMO, should be considered as the first mode of choice in patients with respiratory failure and signs of circulatory impairment, especially in those with impaired RV function. For the remaining patients, Pre-admission RESP score, daily echocardiography, and SOFA score trajectories may help in the early identification of those where conversion from VV to VA ECMO is warranted. Multi-centric studies are warranted to validate these findings.

Pediatric and neonatal extracorporeal life support: current state and continuing evolution

The use of extracorporeal life support (ECLS) for the pediatric and neonatal population continues to grow. At the same time, there have been dramatic improvements in the technology and safety of ECLS that have broadened the scope of its application. This article will review the evolving landscape of ECLS, including its expanding indications and shrinking contraindications. It will also describe traditional and hybrid cannulation strategies as well as changes in circuit components such as servo regulation, non-thrombogenic surfaces, and paracorporeal lung-assist devices. Finally, it will outline the modern approach to managing a patient on ECLS, including anticoagulation, sedation, rehabilitation, nutrition, and staffing.

Factors Behind Decline of Venovenous Extracorporeal Membrane Oxygenation to Support Neonatal Respiratory Failure

OBJECTIVES

Neonates with respiratory failure are ideally supported with venovenous rather than venoarterial extracorporeal membrane oxygenation due to the reduced rate of neurologic complications. However, the proportion of neonates supported with venovenous extracorporeal membrane oxygenation is declining. We aimed to explore the factors behind this decline.

DESIGN

We conducted a survey in order to understand current practice across the United Kingdom, exploring barriers to neonatal venovenous extracorporeal membrane oxygenation in addition to collecting U.K.-wide retrospective data from 2000 onwards.

PATIENTS

Neonates with respiratory failure supported with extracorporeal membrane oxygenation in the United Kingdom.

SETTING

All 11 pediatric U.K. extracorporeal membrane oxygenation centers provided data.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The percentage of neonates with respiratory failure supported with venovenous extracorporeal membrane oxygenation has declined from 58% to 16% over the last decade, reflected internationally with a decrease of 1.3% per year. Nine extracorporeal membrane oxygenation centers are able to offer pediatric venovenous extracorporeal membrane oxygenation, but only four offer neonatal venovenous extracorporeal membrane oxygenation. Of those able to provide neonatal venovenous extracorporeal membrane oxygenation, three centers use dual lumen cannulae and one uses neonatal multisite cannulation. The most frequently cited barriers to neonatal venovenous extracorporeal membrane oxygenation were the lack of availability of a suitable dual lumen cannula with concerns of cardiac perforation and challenges of multisite cannulation due to small caliber femoral veins.

CONCLUSIONS

The majority of U.K. centers are unable to provide venovenous extracorporeal membrane oxygenation for neonates due to concerns with availability and suitability of dual lumen cannulae. An alternative to be considered is the use of multisite cannulation, which has been used historically and is currently being used in centers internationally and in the United Kingdom.

Infusion Jet Flow Control in Neonatal Double Lumen Cannulae

Clinical success of extracorporeal membrane oxygenation (ECMO) depends on the proper venous cannulation. Venovenous (VV) ECMO is the preferred clinical intervention as it provides a single-site access by utilizing a VV double lumen cannula (VVDLC) with a higher level of mobilization and physical rehabilitation. Concurrent venous blood drainage and oxygenated blood infusion in the right atrium at the presence of the cannula makes the flow dynamics complex where potential mixing of venous and oxygenated blood can drastically decrease the overall performance of ECMO. There are no studies focusing on the neonatal and pediatric populations, in which the flow related effects are critical due to the small atrium size. In this study, fluid dynamics of infusion outflow jet for two commercially available neonatal VVDLC is analyzed using particle image velocimetry (PIV). Moreover, six new designs are proposed for the infusion channel geometry and compared. Important flow parameters such as flow turning angle (FTA), velocity decay, potential core, and turbulent intensity are investigated for the proposed models. The experiments showed that the outflow parameters of commercial cannulae such as FTA are strongly dependent on the operating Re number. This may result in a drastic efficiency reduction for cannula operating at off-design flow conditions. Moreover, the infusion outlet tip structure and jet internal guiding pathway (JIGP) was observed to greatly affect the outflow flow features. This is of paramount importance since the anatomical positioning of the cannula and the infusion outlet is strongly dependent on the outflow properties such as FTA.

Hemodynamic effects of perfusion level of peripheral ECMO on cardiovascular system

Background

Peripheral ECMO is an effective cardiopulmonary support in clinical. The perfusion level could directly influence the performances and complications. However, there are few studies on the effects of the perfusion level on hemodynamics of peripheral ECMO.

Methods

The geometric model of cardiovascular system with peripheral ECMO was established. The blood assist index was used to classify the perfusion level of the ECMO. The flow pattern from the aorta to the femoral artery and their branches, blood flow rate from aorta to brain and limbs, flow interface, harmonic index of blood flow, wall shear stress and oscillatory shear index were chosen to evaluate the hemodynamic effects of peripheral ECMO.

Results

The results demonstrated that the flow rate of aorta outlets increased and perfusion condition had been improved. And the average flow to the upper limbs and brain has a positive correlation with BAI (r = 0.037, p < 0.05), while there is a negative correlation with lower limbs (r = − 0.054, p < 0.05). The HI has negative correlation with BAI (p < 0.05, r < 0). The blood interface is further from the heart with the BAI decrease. And the average WSS has negative correlation with BAI (p < 0.05, r = − 0.983) at the bifurcation of femoral aorta and has positive correlation with BAI (p < 0.05, r = 0.99) at the inner aorta. The OSI under different BAI is higher (reaching 0.4) at the inner wall of the aortic arch, the descending aorta and the femoral access.

Conclusions

The pathogenesis of peripheral ECMO with different perfusion levels varies; its further research will be thorough and extensive.

Use of venovenous ECMO for neonatal and pediatric ECMO: a decade of experience at a tertiary children's hospital

BACKGROUND

Advances in extracorporeal membrane oxygenation (ECMO) have led to increased use of venovenous (VV) ECMO in the pediatric population. We present the evolution and experience of pediatric VV ECMO at a tertiary care institution.

METHODS

A retrospective cohort study from 01/2005 to 07/2016 was performed, comparing by cannulation mode. Survival to discharge, complications, and decannulation analyses were performed.

RESULTS

In total, 160 patients (105 NICU, 55 PICU) required 13 ± 11 days of ECMO. VV cannulation was used primarily in 83 patients with 64% survival, while venoarterial (VA) ECMO was used in 77 patients with 54% survival. Overall, 74% of patients (n = 118) were successfully decannulated; 57% survived to discharge. VA ECMO had a higher rate of intra-cranial hemorrhage than VV (22 vs 9%, p = 0.003). Sixteen VA patients (21%) had radiographic evidence of a cerebral ischemic insult. No cardiac complications occurred with the use of dual-lumen VV cannulas. There were no differences in complications (p = 0.40) or re-operations (p = 0.85) between the VV and VA groups.

CONCLUSION

Dual-lumen VV ECMO can be safely performed with appropriate image guidance, is associated with a lower rate of intra-cranial hemorrhage, and may be the preferred first-line mode of ECMO support in appropriately selected NICU and PICU patients.

LEVEL OF EVIDENCE

II.

Prognosis and Outcome of Neonates Treated Either with Veno-Arterial (VA) or Veno-Venous (VV) ECMO

A comparison was done between neonates requiring veno-arterial (VA) ECMO (too small jugular vein, inability to insert a 12 Fr double lumen catheter or cardio-circulatory instability) and neonates treated with veno-venous (VV) ECMO in the same period of time. From 1991-1995 ECMO was done in 48 neonates after failure of maximum conventional treatments, NO-inhalation and HFOV. 30/48 babies were treated with VV-ECMO, with a switch to VA-ECMO later on in 3 of them. In 18 infants VA-ECMO was installed primarily. Differences between the VA- and VV-ECMO group were: the 01 was higher in the VV-treated babies (62±20 vs. 48±13, p < 0.03), as were birth weight (3385±570 vs. 2963±653 g, p< 0.04), gestational age (39.7 ± 1.6 vs. 37.9 ± 2.7 weeks, p< 0.01) and MAP (18.7 ± 2.2 vs. 17.1 ± 2.4 cm H2O, p< 0.05). Severe ICH's occurred more frequently in the VA-treated babies (29 vs. 7%, p< 0.05), the rate of other complications was equal. The mortality rates were 43% (VA) and 15% (VV), p< 0.05. About one third of neonatal ECMO candidates will be treated with VA-ECMO, even if the VV-ECMO technique is available. Need for VA-ECMO implies - due to a higher number of preterm babies and a greater severity of illness before ECMO - a higher incidence of ICH's and a higher mortality rate.

Avalon catheters in pediatric patients requiring ECMO: Placement and migration problems

PURPOSE

The Avalon dual-lumen venovenous catheter has several advantages, but placement techniques and management have not been adequately addressed in the pediatric population. We assessed our institutional outcomes and complications using the Avalon catheter in children.

METHODS

We reviewed all pediatric patients who had Avalon catheters placed for respiratory failure at our institution, excluding congenital heart disease patients, from April 2009 to March 2016. All patients were managed using our standard ECMO protocol, and cannula position was followed by daily chest x-ray and intermittent echocardiography (ECHO). Data included demographics, diagnosis, PRISM3 predicted mortality, ECMO duration, complications, and survival. The primary outcome was the need for catheter repositioning.

RESULTS

Twenty-five patients were included, with mean age 8.3±6.9years and 15±22days of ECMO support. Overall survival was 68% (17/25). Fourteen patients (56%) underwent placement with fluoroscopy in addition to ultrasound and ECHO, primarily after 2013. Overall, thirteen patients (52%) had problems with cannula malposition. 9 of these (69%) required cannula repositioning. Three of 14 (21%) cannulas placed with fluoroscopy required repositioning, compared to 7/11 (64%) placed without fluoroscopy (p=0.05).

CONCLUSIONS

Complications are common with the Avalon catheter in children. Safe percutaneous access requires ultrasound guidance, and use of intraoperative fluoroscopy in addition to echocardiography decreases malposition rates.

LEVEL OF EVIDENCE

IV (Prognosis study).

Influence of central hemodynamics on VV ECMO oxygen delivery in neonatal animal model

BACKGROUND

Recirculation of oxygenated blood in venovenous extracorporeal membrane oxygenation (VV ECMO) can decrease the oxygen delivery provided by the ECMO support. This study investigated the influence of central hemodynamics and catheter position on the amount of recirculation and oxygen delivery during VV ECMO.

METHODS

Recirculation was measured in seven newborn lambs (mean weight 4.7 kg) during VV ECMO using the ELSA Monitor (Transonic Systems, Inc., Ithaca, NY) and using the central venous line (CVL) method. The ECMO pump was set at the prescribed flow of 110-120 mL/kg/min for a targeted oxygen delivery rate of 6cc/kg/min without recirculation. Hemodynamic status before and during ECMO was also measured by the COstatus Monitor (Transonic Systems, Inc.,Ithaca, NY).

RESULTS

Lambs with a higher cardiac index (>160 ml/min/kg), had a tendency to have higher percent oxygen delivery (65-94%, at prescribed flow) while lambs with lower cardiac index (<150 ml/min/kg), tended to have lower percent oxygen delivery (39-62%, at prescribed flow). ELSA recirculation measurements had a squared correlation coefficient R2 = 0.8 with the CVL method.

CONCLUSIONS

The ELSA monitor provides an easy to use, non-invasive method to measure recirculation in VV ECMO. The data suggests that cardiac function may play an important prognostic role in achieving effective VV ECMO support.

Hemodynamic Differences Between Central ECMO and Peripheral ECMO: A Primary CFD Study

Background

Veno-arterial extracorporeal membrane oxygenation (VAECMO), including central ECMO (cECMO) and peripheral ECMO (pECMO), is widely used in cardiopulmonary surgery. The outcomes and complications of both types of ECMO are quite different from each other. The hemodynamic differences among them are hypothesized as a key factor. Hence, a numerical study was conducted to test this hypothesis.

Material/Methods

Ideal cardiovascular models with pECMO and cECMO were established. The aortic pressure and flow rate were chosen as boundary conditions. The flow pattern, blood flow distributions, flow junction, harmonic index (HI) of blood flow, wall shear stress (WSS), and the oscillatory shear index (OSI) were calculated to evaluate the hemodynamic states.

Results

pECMO could achieve better upper limb and brain perfusion (0.05458 vs. 0.05062 kg/s), and worse lower limb perfusion (0.03067 vs. 0.03401 kg/s). There exist low WSS (<0.4 pa) regions at the inner and posterior wall of the aorta, and high WSS (>2 pa) region at the access of the femoral artery. These regions also have relatively high OSI value (reaching 0.45). In contrast, for cECMO, there exist high WSS at the posterior wall of the aortic arch.

Conclusions

The hemodynamic performances of various types of ECMO are different from each other, which maybe the key reasons for the differences in the outcomes and complications. Therefore, for pEMCO, the lower-extremity ischemia is a complication that must be considered. The type, support level, and duration of ECMO should also be carefully regulated according to the patients’ condition, as they are the important factors related to vascular complications.

The pulmonary circulation in neonatal respiratory failure

The pulmonary circulation rapidly adapts at birth to establish lungs as the site of gas exchange. Abnormal transition at birth and/or parenchymal lung disease can result in neonatal hypoxemic respiratory failure. This article reviews the functional changes in pulmonary hemodynamics and structural changes in pulmonary vasculature secondary to (1) normal and abnormal transition at birth, and (2) diseases associated with neonatal hypoxemic respiratory failure. Various management strategies to correct respiratory failure are also discussed.

Venovenous cannulation for extracorporeal membrane oxygenation using a bicaval dual-lumen catheter in neonates

PURPOSE

Venovenous extracorporeal membrane oxygenation (VV-ECMO) has been used as a management strategy for neonates with refractory pulmonary failure. However, VV-ECMO has been limited in neonates secondary to cannula design and patient size. Herein, we describe the use of a bicaval dual-lumen catheter for VV-ECMO in neonates.

METHODS

The medical records of all neonates cannulated for ECMO support with a bicaval dual-lumen 13F catheter from 2008 to 2010 were reviewed.

RESULTS

Nine neonates cannulated with this dual-lumen catheter were identified. The median gestational age was 38 weeks (range, 31-40 weeks), the median weight was 3.4 kg (range, 2.2-5.5 kg), the median age at cannulation was 2 days (range, 1-64 days), and the median duration of ECMO support was 7 days (range, 5-23 days). There were no VV-to-VA conversions. The median pump flow both at 4 and 24 hours postcannulation was 300 mL/min (range, 240-370 mL/min). One patient developed cannula thrombosis, and one required cannula repositioning because of flow recirculation. Overall survival was 56%.

CONCLUSION

The dual-lumen bicaval catheter can be safely used in neonates with minimal complications and is our preferred method for VV-ECMO support in the neonatal population.

Anesthesia for airway surgeries under the perioperative venovenous extracorporeal membrane oxygenation: Three case reports

The airway management for patients with critical airway problems continues to be a challenge to the anesthesiologist. In general cases, conventional ventilation techniques have been used successfully. These include fiberoptic bronchoscope guided intubation, supraglottic airway, endotracheal or endobronchial intubation at operative field, high frequency jet ventilation, etc. However, patients with near-fatal airway obstruction or severely depressed pulmonary function that is refractory to conventional ventilation methods also present. In these cases, cardiopulmonary bypass or extracorporeal membrane oxygenation (ECMO) can be used. Although these situations are uncommon indications for ECMO, ECMO can be a potential option for these life threatening conditions. Especially, venovenous (VV) ECMO can be used for pure pulmonary support. We describe three cases of airway surgery requiring ECMO. VV ECMO was established in all cases. ECMO provided adequate temporary pulmonary support and all patients weaned from ECMO successfully without any complication.

Primary use of the venovenous approach for extracorporeal membrane oxygenation in pediatric acute respiratory failure

OBJECTIVES

To describe a single center's experience with the primary use of venovenous cannulation for supporting pediatric acute respiratory failure patients with extracorporeal membrane oxygenation (ECMO).

DESIGN

Retrospective chart review of all patients receiving extracorporeal life support at a single institution.

SETTING

Pediatric intensive care unit at a tertiary care children's hospital.

PATIENTS

Eighty-two patients between the ages of 2 wks and 18 yrs with severe acute respiratory failure.

INTERVENTIONS

ECMO for acute respiratory failure.

MEASUREMENTS AND MAIN RESULTS

From January 1991 until April 2002, 82 pediatric patients with acute respiratory failure were cannulated for ECMO support. Median duration of ventilation before ECMO was 5 days (range, 1-17 days). Sixty-eight of these patients (82%) initially were placed on venovenous ECMO. Fourteen patients were initiated and remained on venoarterial support, including six in whom venovenous cannulae could not be placed. One patient was converted from venovenous to venoarterial support due to inadequate oxygenation. Venoarterial patients had significantly greater alveolar-arterial oxygen gradients and lower PaO(2)/FIO(2) ratios than venovenous patients (p <.03). Fifty-five of 81 venovenous patients received additional drainage cannulae (46 of 55 with an internal jugular cephalad catheter). Thirty-five percent of venovenous patients and 36% of venoarterial patients required at least one vasopressor infusion at time of cannulation (p = nonsignificant); vasopressor dependence decreased over the course of ECMO in both groups. Median duration on venovenous ECMO for acute hypoxemic respiratory failure was 218 hrs (range, 24-921). Venovenous ECMO survivors remained cannulated for significantly shorter time than nonsurvivors did (median, 212 vs. 350 hrs; p =.04). Sixty-three of 82 ECMO (77%) patients survived to discharge-56 of 68 venovenous ECMO (81%) and nine of 14 venoarterial ECMO (64%).

CONCLUSIONS

Venovenous ECMO can effectively provide adequate oxygenation for pediatric patients with severe acute respiratory failure receiving ECMO support. Additional cannulae placed at the initiation of venovenous ECMO could be beneficial in achieving flow rates necessary for adequate oxygenation and lung rest.

Persistent fetal circulation

Persistent fetal circulation (PFC), also known as persistent pulmonary hypertension of the newborn, is defined as postnatal persistence of right-to-left ductal or atrial shunting, or both in the presence of elevated right ventricular pressure. It is a relatively rare condition that is usually seen in newborns with respiratory distress syndrome, overwhelming sepsis, meconium and other aspiration syndromes, intrauterine hypoxia and ischemia, and/or neonatal hypoxia and ischemia. This condition causes severe hypoxemia, and, as a result, has significant morbidity and mortality. Improved antenatal and neonatal care; the use of surfactant; continuous monitoring of oxygenation, blood pressure and other vital functions; and early recognition and intervention have made this condition even more rare. In modern neonatal intensive care units, anticipation and early treatment of PFC and its complications in sick newborns are commonplace. Thus, severe forms of PFC are only seen on isolated occasions. Consequently, it is even more imperative to revisit PFC compared with the time when there were occasional cases of PFC seen in neonatal intensive care units, and to discuss evolving treatment and management issues that pertain to this syndrome.

Venovenous extracorporeal membrane oxygenation in newborn infants using the umbilical vein as a reinfusion route

PURPOSE

The authors report on four neonates treated with venovenous (VV) extracorporeal membrane oxygenation (ECMO) using the umbilical vein as a reinfusion route.

METHODS

From 1994 to 1997, 26 instances VV-ECMO in neonates have been carried out at our neonatal center for the treatment of severe respiratory and cardiac failure. Among them, 22 patients could be treated with VV-ECMO mainly using 15F double-lumen catheter (DLC), adding the cephalic drainage using another catheter. In the remaining four cases, however, attempts to insert the DLC into the right internal jugular vein failed because the vein was too small or technical problems. For such instances, two catheters were cannulated into the right atrium and the cephalic portion of the right internal jugular vein, respectively. These two venous catheters were connected to the drainage route of ECMO circuit with a "Y" connector. Then, the umbilical vein was cannulated with 10F or 8F catheter, which was connected to the reinfusion route of ECMO to return the oxygenated blood to the infant.

RESULTS

The median age at which ECMO was initiated was 18 hours, and the median ECMO course was 72 hours. The liver function tests were slightly and transiently worsened in two patients during VV perfusion, (in one patient serum glutamic-oxaloacetic transaminase [SGOT] elevated to 76 IU/L and serum glutamic-pyruvic transaminase [SGPT] to 49 IU/L, and in another patient SGOT elevated to 56 IU/L and SGPT remained in normal range). Preumbilical cannula pressures were measured in two patients. In a patient who used 10F umbilical cannula, the preumbilical maximum pressure was 43 mm Hg at 250 mL/min of ECMO flow. In another with an 8F catheter, it was 72 mm Hg at 180 mL/min of ECMO flow. All of the patients survived without any neurological complications.

CONCLUSIONS

If the right internal jugular vein would not accommodate the DLC, VV-ECMO using the umbilical vein as a infusion route could be selected.

Percutaneous access for venovenous extracorporeal life support in neonates

BACKGROUND

Although percutaneous cannulation has been previously described in adult and pediatric patients older than 3 years, its use in neonates for venovenous extracorporeal life support (ECLS) has not been previously described.

METHODS

Twenty neonates of weight 3.4 +/- 0.6 kg (range, 2.3 to 4.9 kg.) with severe respiratory failure (meconium aspiration syndrome, persistent pulmonary hypertension of the newborn, sepsis) were managed with double-lumen venovenous ECLS. Percutaneous access via the right internal jugular (RIJ) vein with a 12F (n = 13) or 15F (n = 7) double-lumen ECLS cannula was obtained via a modified Seldinger technique. RIJ access was specifically obtained 2 to 3 cm above the clavicle with a 21-gauge needle and a 0.018-in guide wire followed by a technique that allowed insertion of the larger cannula guide wire. Decannulation simply involved removal of the cannula with hemostasis obtained by direct pressure.

RESULTS

Percutaneous cannulation was performed without difficulty in 11 infants. Conversion to an open technique for cannula placement was required in four patients early in our experience because percutaneous access to the RIJ with the 0.018-inch guide wire could not be achieved, and in one neonate because the 15F cannula could not be advanced into the RIJ and resulted in laceration of the vein. Inability to achieve RIJ access also led to use of an "exposure-assisted" percutaneous procedure in four patients later in our experience. Complications included a pneumothorax identified on chest radiograph 18 hours after cannulation in one infant and partial thrombotic occlusion of the cannula requiring a change over a guide wire in another. There were no problems associated with decannulation.

CONCLUSIONS

This is the first description of percutaneous cannulation in neonates for venovenous ECLS. In the authors' early experience, percutaneous access using a 12F double lumen venovenous cannula may be efficiently performed especially in patients >3.0 kg in weight and has the potential for simplifying and reducing the cost of the ECLS technique.

Extracorporeal membrane oxygenation causing asymmetric vasculopathy in neonatal infants

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a form of cardiopulmonary bypass therapy used in term or near-term infants with severe cardiorespiratory disorders not responsive to conventional intensive care interventions. An ECMO-associated retinal vasculopathy has been described with little reference to the specific condition of the patient. We examined the eyes of 91 infants who underwent ECMO treatment. An assessment was made of the following: (1) when retinal changes occurred, (2) whether there was a particular systemic disorder or ECMO approach associated with these retinal findings, and (3) whether there may be ocular sequelae from this development.

METHODS

Ninety-one neonates were treated with ECMO for meconium aspiration syndrome (MAS), primary persistent pulmonary hypertension of the newborn, sepsis, congenital diaphragmatic hernia (CDH), respiratory distress syndrome (RDS), and blood aspiration. Venoarterial bypass was performed in 73 patients. The remaining 18 patients underwent venovenous bypass. Ophthalmologic examinations were performed during bypass in 6 infants and within 3 weeks of ECMO in the remainder.

RESULTS

Asymmetric retinopathy (left eye > right eye) was discovered in six infants with CDH and in one infant with RDS within a 2-week period after bypass, demonstrating venous tortuosity with or without intraretinal hemorrhages. One infant treated for MAS had a left eye intraretinal hemorrhage only. All patients with the noted retinal changes underwent venoarterial cannulation. Six of 9 patients with CDH had retinal findings noted compared with 1 of 10 patients with RDS and 1 of 35 patients with MAS.

CONCLUSION

Because we were able to examine infants while they were receiving ECMO or shortly after termination of bypass, asymmetric vasculopathy was found in a greater percentage of our patients compared with a similar large case series. ECMO-associated retinal vasculopathy appeared to disproportionately occur in those patients with CDH who underwent venoarterial bypass. Further study of retinal vascular changes in patients with CDH should be performed to assess long-term effects.

Principles and Practice of Venovenous Extracorporeal Membrane Oxygenation

Over the past several years, the use of venovenous extracorporeal membrane oxygenation (ECMO) has increased. The primary advantage of venovenous (VV) over venoarterial (VA) ECMO is preservation of the carotid artery. Its primary disadvantage is that it does not provide circulatory support. While VV ECMO is technically similar to VA ECMO, clinical application of VV ECMO is quite different from VA ECMO. Recent clinical data show that VV ECMO is safe and effective. The purpose of this review is to discuss these differences between VV and VA ECMO, to review the various forms of VV ECMO, and finally to offer recommendations on the safe clinical use of VV ECMO.

Jugular ligation does not increase intracranial pressure but does increase bihemispheric cerebral blood flow and metabolism

OBJECTIVES

To answer the following questions: a) Does jugular venous ligation (simulating venovenous extracorporeal life support) alter proximal jugular venous pressure, intracranial pressure, hemispheric cerebral blood flow, or cerebral metabolism? b) Does release of ligation reverse these effects? and c) What are the comparative effects of venous ligation alone vs. venous ligation in combination with arterial ligation?

DESIGN

Prospective, randomized, laboratory investigation.

SETTING

Multidisciplinary laboratory setting.

SUBJECTS

Sixteen swine, weighing 8.1 to 12.1 kg, 3 to 4 wks of age.

INTERVENTIONS

Sixteen swine were randomly assigned to two groups, utilizing a random sequence of vessel ligation. Nine swine underwent occlusion of the right internal and external jugular veins alone (venovenous ligation) followed by release of the occlusion and then occlusion of the right common carotid artery and the right internal and external jugular veins together (venoarterial ligation). The remaining seven swine underwent venoarterial ligation, followed by release of the occlusion and then venovenous ligation. In the experimental group in which venovenous ligation was performed first, the 5, and 30-min release periods after ligation were taken to represent the effects of draining the right jugular vein during venovenous extracorporeal life support.

MEASUREMENTS AND MAIN RESULTS

Data were obtained at baseline, 5, and 30 mins after each ligation/release period. Intracranial pressure, right and left internal jugular pressures/flow rates, and cerebral sinus lactate concentrations were measured. Cerebral blood flow was determined using 133Xe clearance methodology, and the cerebral metabolic rate was calculated. There were no significant differences between the ipsilateral internal jugular pressure or extracorporeal life support at 5 or 30 mins after venovenous or venoarterial ligation compared with baseline values or compared with the release of the ligation at 5 or 30 mins. There was a significant increase in right-side (44.7 +/- 2.0 vs. 38.8 +/- 2.4 mL/kg/min; p < .05) and left-side (42.9 +/- 2.3 vs. 38.7 +/- 1.9 mL/kg/min; p < .05) cerebral blood flow 5 mins after venovenous ligation when compared with baseline values. Similarly, after venoarterial ligation, there was a significant increase in right-side (44.6 +/- 2.2 vs. 38.8 +/- 2.4 mL/kg/min; p < .05) and left-side (43.9 +/- 1.5 vs. 38.7 +/- 1.9 mL/kg/min; p < .05) and cerebral blood flow. Cerebral oxygen consumption was significantly increased after venovenous (2.7 +/- 0.2 to 3.2 +/- 0.2 mL/kg/min; p < .05) and venoarterial (2.7 +/- 0.2 to 3.1 +/- 0.2 mL/kg/min; p < .05) ligation at 5 mins after ligation. This increase persisted at the 30-min period and after release of ligation.

CONCLUSIONS

Ligation of the right jugular veins alone (venovenous ligation) or jugular veins and right carotid artery (venoarterial ligation) does not increase jugular venous pressures or intracranial pressure. However, this procedure does increase cerebral blood flow and cerebral oxygen consumption. These findings demonstrate that there is adequate decompression of the venous system by the cerebrovascular system and retrograde decompression during extracorporeal life support appears unwarranted.

Independent ventilation and ECMO for severe unilateral pulmonary edema after SLT for primary pulmonary hypertension

Single lung transplantation (SLT) is now accepted therapy for selected cases of severe pulmonary hypertension. A recognized complication is the postoperative development of reperfusion edema in the graft, a potentially fatal cause of respiratory failure. Because reperfusion edema may be a reversible process, temporizing support measures can be life-saving. We report the case of a 48-year-old woman who developed severe reperfusion edema following right SLT for primary (unexplained) pulmonary hypertension. Extracorporeal membrane oxygenation (ECMO) was instituted. Independent lung ventilation was later begun and resulted in markedly improved oxygenation allowing withdrawal of ECMO. We conclude that reperfusion edema following SLT for pulmonary hypertension may be uniquely amenable to treatment with independent lung ventilation and ECMO if needed.

Extracorporeal life support for neonatal respiratory failure. A 20-year experience

OBJECTIVE

The authors reviewed their experience with extracorporeal life support (ECLS) in neonatal respiratory failure; they define changes in patient population, technique, and outcomes.

SUMMARY BACKGROUND DATA

Extracorporeal life support has progressed from laboratory research to initial clinical trials in 1972. Following a decade of clinical research, ECLS is now standard treatment for neonatal respiratory failure refractory to conventional pulmonary support techniques. Our group has the longest and largest experience with this technique.

METHODS

Between 1973 and 1993, 460 neonates with severe respiratory failure were treated using ECLS. The records of all patients were reviewed.

RESULTS

Overall survival was 87%. Primary diagnoses were meconium aspiration syndrome (MAS; 169 cases [96% survival]), respiratory distress syndrome/hyaline membrane disease (91 cases [88% survival]), persistent pulmonary hypertension of the newborn (37 cases [92%]), pneumonia/sepsis (75 cases [84% survival]), congenital diaphragmatic hernia (CDH; 67 cases [67% survival]), and other diagnoses (21 cases [71% survival]). Common mechanical complications included clots in the circuit (136; 85% survival); air in the circuit (67; 82% survival); cannula problems (65; 83% survival) and oxygenator failure (34; 65% survival). Patient-related complications included intracranial infarct or bleed (54 cases; 61% survival), major bleeding (48 cases; 81% survival), seizures (88 cases; 76% survival), metabolic abnormalities (158 cases; 71% survival) and infection (21 cases; 48% survival). Since 1989, treatment groups have been expanded to include premature infants (13 cases; 62% survival), infants with grade I intracranial hemorrhage (28 cases; 54% survival) and "non-honeymoon" CDH patients (15 cases; 27% survival). Since 1990, single-catheter venovenous access has been used in 131 patients (97% survival) and currently is the preferred mode of access. Follow-up ranges from 1 to 19 years; 80% of patients are growing and developing normally.

CONCLUSIONS

Extracorporeal life support has become standard treatment for severe neonatal respiratory failure in our center (460 cases; 87% survival), and worldwide (8913 cases; 81% survival). The availability of ECLS makes the evaluation of other innovative methods of treatment, such as late elective repair of diaphragmatic hernia and new pulmonary vasodilators, possible. The application of ECLS is now being extended to premature and low-birth weight infants as well as older children and adults.

Complications of neonatal extracorporeal membrane oxygenation

From 1973-1985 to 1988 the average patient complications per case were 1.44 per case and significantly increased during 1990 to 1992 to 2.10 per case (Figure 3). During the same periods patient survival significantly decreased from 84% (1973-1985 to 1988, n = 2463) to 80% (1990 to 1992, n = 4005) (Figure 4). The association between total complication rates and survival rate was examined by regression analysis (Table 5). The correlation of patient complication rate and total complication rate with survival is highly significant; however, causality cannot be established. When comparing different entry criteria (Table 2) for incidence of mechanical and patient complications, no significant differences are apparent. This is not surprising since each of the entry criteria were designed to identify the same patient population. When premature neonates (> 35 weeks) were placed on ECMO, 36% of them had intracranial haemorrhage (ICH) with 62% mortality while only 12% of the neonates < 35 weeks had ICH and a 49% mortality. Similar findings were noted with low birthweight neonates (< 2.2 kg), 28% had ICH with 64% mortality while only 12% of the neonates > 2.2 kg had ICH with a 50% mortality. Selection criteria remain problematic for a variety of reasons. They cannot be viewed as absolute because of variability between centres. What represents likely 80% mortality in one centre may not apply to another. Historical controls are misleading because changing respiratory therapy strategies make historical populations difficult to compare. Also, once an ECMO centre becomes established, a more challenging group of patients will be attracted than previously was the case. Further, a single entry criterion cannot be generalized for all entry diagnoses. Criteria for an 80% predicted mortality is probably not the same for MAS, CHN, PPHN, and sepsis. Subsequent patients registered in the Neonatal ECMO Registry of the Extracorporeal Life Support Organization will address these issues more thoroughly, as specific details of the pre-ECMO condition and therapeutic strategies are collected. This collective review should help to identify trends which require reassessment of technique or patient management.

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.

Advances in the treatment of persistent pulmonary hypertension of the newborn

Despite an association with meconium and blood aspiration, pneumonia, sepsis, pneumothorax, prematurity, and congenital diaphragmatic hernia, no cause for persistent pulmonary hypertension of the newborn can be found in many cases. This article discusses the advances in current therapies including the promising new therapy of inhaled nitric oxide.

Multicenter comparison of conventional venoarterial access versus venovenous double-lumen catheter access in newborn infants undergoing extracorporeal membrane oxygenation

A multicenter trial was designed to compare standard venoarterial (VA) access versus single-catheter, venovenous access using the double-lumen catheter (VV-DLC) for newborns with respiratory failure undergoing extracorporeal membrane oxygenation (ECMO). Twenty-seven ECMO centers participated, each submitting data from the center's most recent VA cases, and data from VV-DLC cases completed upon entering the study. Data from 135 VA ECMO cases and 108 VV-DLC cases were submitted. All diagnoses resulting in neonatal respiratory failure were submitted, including patients with congenital diaphragmatic hernia (24 patients VA bypass, 11 patients VV-DLC bypass). Overall survival in patients undergoing VA bypass was 87%, while survival in patients undergoing VV-DLC bypass was 95%. Eleven patients required conversion from VV-DLC bypass to VA bypass because of insufficient support--10 of these patients survived (91% survival). Average bypass time for newborns undergoing VA bypass was 132 +/- 7.4 hours versus 100 +/- 5.1 hours for those undergoing VV-DLC bypass. Neurologic complications were more common in the VA bypass patients, although the VV patients were more stable. Hemorrhagic, cardiopulmonary, and mechanical complications, other than kinking of the DLC, occurred with approximately equal frequency in each group. In conclusion, in newborns with adequate cardiac function, venovenous ECMO using the DLC can provide the same level of support as conventional VA ECMO, without ligation of the carotid artery.

Efficacy of venovenous extracorporeal membrane oxygenation for neonates with respiratory and circulatory compromise

We report a 12-month experience at Egleston Children's Hospital in Atlanta, Ga., with a protocol under which venovenous extracorporeal membrane oxygenation (ECMO) was used instead of venoarterial ECMO. Fifty-five newborn infants were referred for ECMO, four of whom had disqualifying conditions (all four died). Thirty-one infants were supported without recourse to ECMO, one of whom died. Of the 20 remaining patients, three were placed on a venoarterial ECMO regimen because of our early uncertainty about the efficacy of venovenous ECMO or because of technical constraints. All other patients (n = 17), including three with congenital diaphragmatic hernia, were supported with venovenous perfusion. No patient begun on a venovenous ECMO regimen required conversion to venoarterial bypass. Before ECMO, venovenous patients required an average dopamine dose of 16 micrograms/kg per minute and an average dobutamine dose of 6 micrograms/kg per minute. Of 15 patients studied before ECMO, three had significantly impaired contractility, and all had evidence of pulmonary hypertension on an echocardiogram. Mean blood pressure did not change while heart rate fell from 172 to 146 beats/min during the first 2 hours of ECMO and vasoactive drug doses were reduced. Of the 17 venovenous ECMO patients, 15 (88%) survived. We conclude that neonatal patients with severe hypoxia and substantial circulatory compromise can be effectively supported by venovenous ECMO in most cases.

Uses of extracorporeal membrane oxygenation in nonneonatal respiratory patients. An update

Neonatal extracorporeal membrane oxygenation (ECMO) has progressed rapidly from the experimental stage to a standard of care for certain infants who fail to respond to maximal conventional management. A broad diagnostic group of nonneonatal patients has now been supported by several different modes of ECMO with encouraging results. Selection criteria for nonneonatal patients that differ from those used for neonatal patients are emerging. Prospective randomized clinical trials are needed.

A prospective, multicenter, randomized study of high versus low positive end-expiratory pressure during extracorporeal membrane oxygenation

To test the hypothesis that increased positive end-expiratory pressure (PEEP) could prevent deterioration of pulmonary function and lead to more rapid recovery of lung function, we randomly assigned 74 patients undergoing extracorporeal membrane oxygenation (ECMO) at four centers to receive either high (12 to 14 cm H2O) or low (3 to 5 cm H2O) PEEP. The two groups were similar in terms of weight, gestational age, diagnosis, and pre-ECMO course. All other aspects of care were identical. Dynamic lung compliance was measured at baseline and every 12 hours. Radiographs of the chest were obtained daily. Survival rates were similar in the two groups: 36 of 40 for low PEEP and 34 of 34 for high PEEP. The duration of ECMO therapy was 97.4 +/- 36.3 hours in the high-PEEP group and 131.8 +/- 54.5 hours in the low-PEEP group (p less than 0.01). Dynamic lung compliance throughout the first 72 hours of ECMO was significantly higher in patients receiving high PEEP. Radiographic appearance of the lungs correlated well with lung compliance: patients receiving high PEEP had significant deterioration of the radiographic score less frequently than those receiving low PEEP. High PEEP also was associated with significantly fewer complications. We conclude that PEEP of 12 to 14 cm H2O safely prevents deterioration of pulmonary function during ECMO and results in more rapid lung recovery than traditional lung management with low PEEP.

Extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a means of diverting a fraction or all of the circulation through a device that permits gas exchange across a permeable membrane. The site of removal and the site of return of blood are dictated primarily by practical considerations based on the volume of flow of blood to be diverted and whether a particular organ is to be bypassed. The prototype of extracorporeal oxygenation is heart-lung bypass, used for various types of cardiac surgery, in which the entire venous return is diverted through an oxygenator (bubble or membrane type) and returned to the aorta. Since the earliest reports of the use of ECMO in neonates, venoarterial bypass has been the preferred route, with blood drained from the right atrium and returned either to the carotid artery or to the femoral artery, although the former seems to have been used most often (2;4;11;12;14;18). In some reports, veno-venous bypass has also been accomplished with removal of blood from the right atrium and return into the umbilical or femoral vein (13;19). Gas exchange across the lung may also continue, although the ventilator rate, tidal volume, or peak inspiratory pressure are usually reduced markedly during the period of extracorporeal oxygenation. Anticoagulation is accomplished with few problems by infusion of heparin sulfate throughout the duration of the procedure. There now have been enough reports in the literature (individual cases or series of patients) to demonstrate that the procedure can be carried out with a minimum of technical difficulties in newborn infants (2;3;4;11;12;18), although the selection of “appropriate” patients reduces the morbidity and technical challenges of the procedure.

Developmental outcome of neonates treated with extracorporeal membrane oxygenation

The leading cause of death in the neonatal period is respiratory failure, and extracorporeal membrane oxygenation (ECMO) is an effective means of improving survival in select patients. Only neonates with severe hypoxia and acidosis are treated with ECMO. To determine the developmental outcome of the neonates we supported with ECMO, we reviewed the records of all our patients who are at least 6 months of age. The results of follow-up assessment were available for 57 patients and growth parameters were available for 43 patients. Examinations were done at 6 to 48 months (mean, 22.1). Growth parameters showed that 14% of the patients were below the tenth percentile for height and weight while 16.3% were below the tenth percentile for head circumference. Twenty-four patients were evaluated using the Bayley Scales of Infant Development consisting of a Mental Developmental Index (MDI) and a Psychomotor Developmental Index (PDI). Normal scores (greater than 84) were obtained in 75% on the MDI and in 88% on the PDI. Only two patients (8%) scored less than 85 on both portions. Twelve patients were evaluated using the McCarthy Scales of Children's Abilities. The mean score was 95 and nine patients (75%) had scores greater than 85. The Gessell was used to evaluate six patients and five were normal. The Denver Developmental Screening Test was used to evaluate 23 patients and all passed. The results of neurologic examination were documented in 57 patients. One patient had severe spastic quadriplegia with cerebral palsy. The neurological examination was normal in the other patients. Only one of 57 patients is profoundly delayed (2%) and 45 (79%) are normal.(ABSTRACT TRUNCATED AT 250 WORDS)

To-and-for extracorporeal lung assist (ECLA) through a single catheter-in premature goats as an experimental model of infant respiratory Insufficiency

A new to-and-fro V-V bypass extracorporeal lung assist (ECLA) through a single catheter as a blood access was investigated for its efficacy on six premature goats delivered by Cesarean section at a gestational age of 118 approximately 139 days as an experimental model of infant respiratory insufficiency, then applied to a human premature infant suffering from life threatening barotrauma that had developed from mechanical pulmonary ventilation. The extracorporeal bypass flow and the gas flow to the artificial membrane lung were controlled to keep Pa(O)(2) above 40 mmHg and Pa(CO)(2) within normal limits. The neonate's own lungs were treated with a continuous positive airway pressure of 5 approximately 12 cmH(2)O, apneic oxygenation or IMV. Two goats weighing 1250 g and 700 g died 2 approximately 2.5 hours after birth from severe circulatory distress. However, the other four neonates which were heavier than 2000 g, were successfully weaned from ECLA, and three of these could be weaned from mechanical ventilation as well. A human infant also survived and was weaned from ECLA on the third day.(Tanoue T, Terasaki H, Sadanaga M et al.: To-and-fro extracorporeal lung assist (ECLA) through a single catheter-in premature goats as an experimental model of infant respiratory insufficiency.

Aluminum-containing emboli in infants treated with extracorporeal membrane oxygenation

We found fibrin thrombi or thromboemboli at autopsy in 22 of 23 infants with respiratory failure who had been treated with venoarterial extracorporeal membrane oxygenation (ECMO). In addition, distinctive basophilic aluminum-containing emboli were found in 12 of the infants; the distribution of these emboli was similar to that of the thromboemboli, except that an aluminum-containing embolus was found in a lung in only 1 infant. Sixteen infants had pulmonary thrombi or thromboemboli. We also found friable aluminum-containing concretions adhering loosely to the mixing rods of heat exchangers that had been used to warm the blood flowing through the ECMO circuit; such concretions were not present on unused mixing rods. We propose that these aluminum-containing concretions developed as the silicone coating of the heat exchanger wore away and aluminum metal was exposed to warm, oxygenated blood and that fragments of aluminum-containing concretions formed emboli. This hypothesis is supported by the fact that aluminum-containing emboli were generally not present in the lungs, which are bypassed by ECMO. Although infarcts were found in 16 of the 23 infants, we cannot be certain whether any of the infarcts were caused by the aluminum-containing emboli.

Venovenous extracorporeal membrane oxygenation (ECMO) using a double-lumen cannula

Extracorporeal membrane oxygenation (ECMO) can support neonates with severe respiratory failure. Currently, the most common application of ECMO requires venoarterial access. Venovenous (VV) ECMO is desirable to avoid common carotid artery ligation. However, the best technique of venous access for VV ECMO is not established. Using a single cannula with a double-lumen (DLC) in the right atrium for simultaneous drainage and infusion of blood, VV ECMO provided total respiratory support for six apneic puppies for 3 h each. Mean systemic arterial oxygenation was lower with DLC VV (50 torr) compared to VA ECMO (247 torr), but a physiologic pH (mean 7.34) was maintained on DLC VV bypass. Higher mean bypass flow was required on DLC VV (124 ml/kg/min) compared to VA flow (101 ml/kg/min) because of recirculation of oxygenated blood. The position of the DLC in the right atrium needed to be closely monitored. Hemorrhage was noted in the myocardium after use of DLC VV ECMO.

The use of venovenous extracorporeal membrane oxygenation in sheep receiving severe smoke inhalation injury

Smoke inhalation injury now represents the most frequent cause of death in burn patients, and accounts for 20-80 per cent of overall mortality. We have studied the use of extracorporeal membrane oxygenation (ECMO) to support sheep which have received lethal pulmonary smoke damage. The animals (n = 19) received inhalation injury induced by insufflation with smoke derived from burning cotton delivered with a bee smoker. The treatment group, those placed on ECMO at the time of injury (n=6), were systemically heparinized and placed on a venovenous perfusion circuit consisting of a roller pump, membrane oxygenator and heat exchanger. Blood flow rate in the circuit approximated 20-25 per cent of cardiac output. The animals remained on partial venovenous bypass until the termination of the experiment 96 h after injury. All animals in the treatment group survived. The control sheep (n = 7) received inhalation injury alone and had a 100 per cent mortality (P = 0.0015 ECMO vs. control). Ventilatory management of treatment and control groups followed an identical protocol. We have also studied a third group (n = 6) composed of animals receiving inhalation injury with systemic heparinization but not ECMO. This group had a 66 per cent mortality at 96 h. These studies suggest that partial venovenous ECMO may be a valuable form of adjunctive treatment in severe inhalation injury.