Impella LP 2.5 for left ventricular unloading during venoarterial extracorporeal membrane oxygenation support

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is commonly used as a means of support for acute cardiopulmonary failure. In the setting of severe left ventricular (LV) dysfunction, VA-ECMO may be complicated by LV distension, which can lead to pulmonary edema and compromise myocardial recovery. Traditional decompression methods carry significant risk. We report the use of the Impella LP 2.5 for LV decompression in a 70-year-old man with decompensated heart failure who was placed on VA-ECMO for cardiogenic shock with severe pulmonary edema and respiratory failure. Both devices were successfully weaned on day 5 of VA-ECMO support, after myocardial recovery.     

Use of the CDI blood parameter monitoring system 500 for continuous blood gas measurement during extracorporeal membrane oxygenation simulation

The Oximetrix III Opticath (Abbott Critical Care Systems) is used for continuous measurement of venous saturation in a variety of applications, including extracorporeal membrane oxygenation (ECMO), despite clinical reports that have presented data showing poor accuracy of these devices. The CDI Blood Parameter Monitoring System 500 (Terumo) is an inline blood gas monitoring tool commonly used during cardiopulmonary bypass procedures to continuously assess oxygen saturation, blood gases, potassium, and bicarbonate. The purpose of this experiment was to compare the Opticath and the CDI 500 in trending venous blood saturation during a simulation of ECMO. An ECMO simulation circuit consisting of a silicone rubber membrane oxygenator and a stainless steel heat exchanger was constructed, and a standard venous reservoir bag was used to represent the patient. The CDI and the Opticath were incorporated side by side into a shunt that originated just before the oxygenator and returned flow to the venous line. The circuit was primed with fresh porcine blood and conditioned with the addition of CO2 to simulate typical venous blood under ECMO conditions. After an initial calibration procedure, samples were drawn and analyzed by an AVL Opti CCA (Roche/Osmetech) every 4-8 hours for a period of 7 days, with calibration of each device at sample intervals. The data were plotted, and a least squares regression line was calculated. The average error for venous saturation of the CDI and Opticath after 72 hours was 3.86 and 9.51 respectively. At 168 hours, error for the CDI was 8.37, and the Opticath had an error of 14.78. A correlation analysis of the CDI and AVL CCA analyzer yielded a correlation coefficient of r = .88 at 72 hours and r = .84 at 168 hours. Correlation between the Opticath and the AVL CCA yielded a correlation coefficient of r = .77 at 72 hours and r = .55 at 168 hours. Based on these findings, the CDI 500 is an effective tool for monitoring venous blood saturation under simulated conditions of ECMO. Keywords: CDI 500, Opticath, extracorporeal membrane oxygenation, venous saturation.     

Development of disposable self-regulating blood pumps and automatically-controlled portable extracorporeal membrane oxygenation systems for neonatal extracorporeal membrane oxygenation

For safer and simpler neonatal ECMO management, the authors have been developing an innovative, automatically-controlled ECMO machine using self-regulating blood pumps. The newest model is an air-driven, tube-type blood pump. A pair of blood pumps are placed in parallel and actuated alternately with compressed air. The pump flow is automatically regulated in accordance with hemodynamic changes of the body. The need for a venous reservoir is eliminated because the circuit does not generate excessive negative pressure when there are shortages of draining blood. Therefore, the priming volume of the circuit is only 85 ml. This ECMO apparatus has three driving modes, one of which is a "delay" mode. This enables the pump flow to easily be varied from 10 to 500 ml/min under automatic control, and it can be used when the pump flow is decreased for weaning. This newest ECMO apparatus was clinically used in 3 neonates with severe lung hypoplasia and persistent fetal circulation. The ECMO duration was 139 h to 168 h, and the maximum ECMO flow 71.3 to 109.0 ml/min/kg. Thanks to the self-regulation, intensive observation of the circuit was not necessary during ECMO. Damage to blood cells was less significant, and the use of blood products was only minimal (15.7 ml/kg/day) because a large volume of blood to stabilize the pump performance was not necessary. In conclusion, the automatically-controlled ECMO apparatus worked well without complications by changing the ECMO flow automatically in accordance with hemodynamic changes. This automatic ECMO system required fewer personnel expenditures and was also favorable in terms of hematological findings.     

Venovenous versus venoarterial extracorporeal membrane oxygenation in congenital diaphragmatic hernia

Background: Extracorporeal membrane oxygenation (ECMO) has a significant role as a final rescue modality in severe respiratory failure of the newborn with congenital diaphragmatic hernia (CDH). The objective of this study was to compare the efficiency of venovenous (VV) versus venoarterial (VA) ECMO in newborns with CDH.Methods: A retrospective report of 11 years experience (1990 through 2001) of a single center, comparing VV and VA ECMO is given. VV ECMO was the preferred rescue modality for respiratory failure unresponsive to maximal medical therapy. Only when the placement of a VV ECMO 14F catheter was not possible, VA ECMO was used. Forty-six patients met ECMO criteria; 26 were treated with VV ECMO and 19 with VA ECMO. One patient underwent conversion from VV to VA ECMO.Results: Before ECMO, there was no difference between VV and VA ECMO patients in mean oxygenation index (83 v 83), mean airway pressure (18.4 v 18.9 cm H₂O), ECMO cannulation age (28 v 20 hours), or in the percentage of patients who needed dopamine and dobutamine (100% v 100%). From November 1994, nitric oxide (NO) was available; before ECMO, 11 of 14 (79%) VV ECMO patients received NO versus 9 of 10 (90%) patients in the VA group. VV ECMO patients were larger (3.34 v 2.77 kg; P < .05) and of advanced gestational age (39.0 v 36.9 wk; P < .05) compared with VA ECMO patients. There was no significant difference between VV and VA ECMO patients in survival rate (18 of 26, 69% v 13 of 19, 68%), ECMO duration (152 v 150 hours), time of extubation (32.0 v 33.5 days), age at discharge (73 v 81 days), or incidence of short-term intracranial complications (3.8% v 10.5%) or myocardial stun (3.8% v 15.8%).Conclusions: The authors conclude that VV ECMO is as reliable as VA ECMO in newborns with CDH in severe respiratory failure who need ECMO support and who can accommodate the VV double-lumen catheter. Because of its potential advantages, VV ECMO may be the preferred ECMO method in these infants.     

Femoral venoarterial extracorporeal membrane oxygenation using a novel biatrial cannula for venous drainage and left ventricular venting

Extracorporeal life support (ECLS) is an expanding technology for patients in cardiogenic shock. The majority of patients requiring ECLS can be managed with percutaneous venoarterial (VA) femoral cannulation. Despite sufficient extracorporeal circulatory support, a unclear number of patients develop left ventricular distension which can result in increased wall tension and stress as well as worsening pulmonary edema. Indications to vent the left ventricle can be controversial. When venting is indicated, a number of additional procedures may be considered including inotropic support, intra-aortic balloon pump, impella, balloon atrial septostomy, or placement of a transseptal cannula. We present a unique case of a femoral VA extracorporeal membrane oxygenation as a bridge to transplant with left-sided venting using a Bio-Medicus NextGen cannula (Medtronic) with a transseptal approach.     

Nesiritide during extracorporeal membrane oxygenation

Nesiritide is a recombinant formulation of B-type natriuretic peptide (BNP). Preliminary experience in the adult population has shown nesiritide to be an effective agent in the treatment of decompensated congestive heart failure (CHF) in adults. Given its physiological effects, it may be an effective agent in other clinical scenarios. We report the use of nesiritide in two infants during extracorporeal membrane oxygenation (ECMO). In one patient, nesiritide in doses up to 0.09 microg.kg(-1).min(-1) were used to control mean arterial pressure while in the other patient, doses of 0.01-0.03 microg.kg(-1).min(-1) were used to augment urine output. The potential applications of nesiritide and dosing regimens for this agent in the ECMO population are discussed.     

Regional blood flow distribution during extracorporeal membrane oxygenation in rabbits

To study regional blood distribution during extracorporeal membrane oxygenation, we stabilized three groups of five rabbits each (3 to 5 kg) on venoarterial bypass at a flow rate of 30 ml/kg/min. Albumin aggregates (15 to 30 microns) labeled with technetium 99m were injected into the left ventricle during bypass (ventricle), the perfusion cannula during bypass (cannula), and the left ventricle with no bypass (control). Animals were put to death, organs were removed, and the percent distribution was determined with a gamma camera. The Student Newman-Keuls test was used for statistical comparisons. Distribution to both the heart and brain in the cannula group were decreased from control by 55% and 35%, respectively. Distribution to the brain in the ventricle group was also decreased from control by 39%. Intestinal distribution was elevated above control in the ventricle group by 37%, whereas musculoskeletal distribution was elevated 33% above control in the cannula group. No significant changes were noted for the kidneys, stomach, or liver. These data suggest that overall perfusion of some vital organs may be significantly reduced during low-flow extracorporeal membrane oxygenation, specifically in the case of the heart and brain, which may be deprived of oxygenated blood.     

Carotid artery reconstruction following neonatal extracorporeal membrane oxygenation

Although reconstruction of the right common carotid artery (RCCA) in neonatal extracorporeal membrane oxygenation (ECMO) patients is intuitively attractive, there is little known about prolonged arterial cannulation and how it may affect subsequent vascular repair. A histological study of RCCA segments from neonatal ECMO patients was performed, so that cannulation technique and catheter design could be optimized before proceeding with arterial reconstruction. Circumferential transmural necrosis (CTN) was found in 25 of 31 (80%) arteriotomy specimens in comparison with 2 of 9 (20%) more proximal carotid specimens; the remaining specimens in each group demonstrated either focal subintimal or focal transmural necrosis. CTN was more common in patients with longer ECMO runs (96 +/- 5.9 versus 75 +/- 5.6 hours, P = .009; arteriotomy site), but was independent of cannula size, birthweight, and gestational age. Eleven patients have undergone RCCA reconstruction. Doppler flow studies at 4 to 7 months of follow-up in five patients demonstrated slightly higher right-sided versus left-sided peak systolic, end-diastolic, and mean flow velocities. No neurological or developmental problems could be attributed to vascular reconstruction. In conclusion, RCCA reconstruction is technically feasible, but due to the high prevalence of CTN at the arteriotomy site, excision of this segment is recommended at the time of arterial repair.     

Prostaglandin F1 alpha levels during and after neonatal extracorporeal membrane oxygenation

Infants receiving extracorporeal membrane oxygenation therapy undergo long-term cardiopulmonary bypass, are systemically heparinized, and frequently receive platelet transfusions. Prostacyclin is a powerful inhibitor of platelet aggregation as well as a potent vasodilator. The levels of its stable metabolite prostaglandin F1 alpha increase significantly in children undergoing cardiopulmonary bypass during heart operations but decrease to preoperative levels after bypass. To determine the effect of long-term bypass on prostacyclin levels, multiple plasma samples were analyzed in 10 human neonates both during extracorporeal membrane oxygenation therapy and within 24 hours after extracorporeal membrane oxygenation. Prostaglandin F1 alpha, the stable metabolite of prostacyclin, was quantitated by radioimmunoassay in picograms per milliliter. Prostaglandin F1 alpha levels were elevated while the patients received extracorporeal membrane oxygenation therapy but decreased with duration of extracorporeal membrane oxygenation. In most infants, prostaglandin F1 alpha levels rose again during weaning from extracorporeal membrane oxygenation and remained elevated for 24 hours after extracorporeal membrane oxygenation. Extracorporeal membrane oxygenation course influenced circulating prostaglandin F1 alpha levels. Fluctuating prostaglandin F1 alpha levels are of clinical significance in the management of vasomotor tone and platelet function, common problems in the care and the prevention of hemorrhage in these critically ill infants.     

Tension pneumothorax during extracorporeal membrane oxygenation

Life-threatening tension pneumothorax in neonates on extracorporeal membrane oxygenation (ECMO) has been associated with an increase in arterial oxygen tension and a decrease in peripheral perfusion, followed by a decrease in ECMO flow with progressive hemodynamic deterioration. To investigate this triad, chest tubes were placed bilaterally in 9 dogs to allow injection of air to produce tension pneumothorax. Six dogs were subsequently placed on standard venoarterial ECMO before the reinduction of tension pneumothorax. Measured values included arterial pulse pressure, inferior vena cava pressure, systemic arterial blood gases, peripheral arterial oxygen saturation, mixed venous oxygen saturation, and left heart cardiac output. Oxygen delivery was calculated from directly measured values. Each of the 6 dogs on ECMO demonstrated the triad of increased arterial oxygen tension (92 +/- 7 to 325 +/- 20 mm Hg; p less than 0.05), decreased peripheral perfusion (as evidenced by a decrease in pulse pressure from 55 +/- 4 to 31 +/- 5 mm Hg; p less than 0.05), and decreased mixed venous oxygen saturation (71% +/- 3% to 22% +/- 2% saturation; p less than 0.05) followed by a lower ECMO flow with progressive hemodynamic deterioration (oxygen delivery decreased from 285 +/- 11 to 111 +/- 12 mL/min; p less than 0.05). Aspiration of the intrathoracic air allowed return to baseline ECMO flow and hemodynamic stability in all dogs. The triad of increased arterial oxygen tension and decreased peripheral perfusion (as evidenced by a lower arterial pulse pressure and lower mixed venous oxygen saturation) followed by decreased ECMO flow with progressive hemodynamic deterioration consistently appears when tension pneumothorax occurs on ECMO.     

Stunned myocardium during extracorporeal membrane oxygenation

The "stunned myocardium" is a syndrome of reversible myocardial dysfunction that may be mediated by oxygen-derived free radicals. This phenomenon has been seen in some neonates undergoing extracorporeal membrane oxygenation. We performed echocardiograms and measured creatine phosphokinase isoenzymes and lipid peroxide levels in 16 neonates before, during, and after extracorporeal membrane oxygenation. Infants who developed stunned myocardia by echocardiography did so shortly after initiation of bypass and exhibited concurrent elevations of the MB fraction of creatine phosphokinase. Lipid peroxide levels did not simultaneously rise. These data suggest that oxygen-derived free radicals may not cause the stunned myocardium seen in neonates undergoing extracorporeal membrane oxygenation.     

Antithrombin replacement during extracorporeal membrane oxygenation

Heparin remains the predominant anticoagulant during extracorporeal membrane oxygenation (ECMO). Heparin acts by potentiating the anticoagulant effect of antithrombin (ATIII). Acquired ATIII deficiency, common in pediatric patients requiring ECMO, may result in ineffective anticoagulation with heparin. ATIII replacement may result in increased bleeding. Our objective is to determine ATIII's effect on anticoagulation and blood loss during ECMO. A retrospective chart review was performed of all patients at Children's Hospital of Wisconsin who received ATIII while supported on ECMO in 2009. ATIII activity levels, heparin drip rate, and activated clotting times (ACT) were compared before, 4, 8, and 24 h after ATIII administration. Chest tube output and packed red blood cell (pRBC) transfusion volume were compared from 24 h before ATIII administration to 24 h after. Twenty-eight patients received ATIII as a bolus dose during the course of 31 separate times on ECMO support. The median age of these patients was 0.3 years (range 1 day-19.5 years). ATIII activity increased significantly at 8 and 24 h after administration. No significant difference was noted in heparin drip rate, ACT levels, chest tube output, or pRBC transfusion volume. ATIII administration resulted in higher ATIII activity levels for 24 h without a significant effect on heparin dose, ACT, or measures of bleeding.     

Mediastinal hemorrhage during extracorporeal membrane oxygenation

A case of mediastinal hemorrhage along with hemorrhage into a pneumatocele while on extracorporeal membrane oxygenation (ECMO) is presented. Computerized tomography of the chest was utilized to support the diagnosis. Barotrauma to the lungs best explains the inciting event that allowed the hemorrhage to occur once the patient was heparinized for ECMO. This complication serves to point out the importance of commencing early ECMO support before widespread pulmonary and mediastinal barotrauma develops.