Extracorporeal life support

Pre-clinical evaluation of the infant Jarvik 2000 heart in a neonate piglet model

BACKGROUND

The infant Jarvik 2000 heart is a very small, hermetically sealed, intracorporeal, axial-flow ventricular assist device (VAD) designed for circulatory support in neonates and infants. The anatomic fit, short-term biocompatibility and hemodynamic performance of the device were evaluated in a neonate piglet model.

METHODS

The infant Jarvik 2000 heart with two different blade profiles (low- or high-flow blade design) was tested in 6 piglets (8.8 ± 0.9 kg). Using a median sternotomy, the pump was placed in the left ventricle through the apex without cardiopulmonary bypass. An outflow graft was anastomosed to the ascending aorta. Hemodynamics and biocompatibility were studied for 6 hours.

RESULTS

All 6 pumps were implanted without complication. Optimal anatomic positioning was found with the pump body inserted 2.4 cm into the left ventricle. Hemodynamics demonstrated stability throughout the 6-hour duration. The pump flow increased from 0.27 to 0.95 liter/min at increasing speeds from 18 to 31 krpm for the low-flow blade design, whereas the pump flow increased from 0.54 liter/min to 1.12 liters/min at increasing speeds from 16 krpm to 31 krpm for the high-flow blade design. At higher speeds, >80% of flow could be supplied by the device. Blood chemistry and final pathology demonstrated no acute organ injury or thrombosis for either blade design.

CONCLUSIONS

The infant Jarvik 2000 heart is anatomically and biologically compatible with an short-term neonate piglet model. This in vivo study demonstrates the future feasibility of this device for clinical use.

Bivalirudin in pediatric patients maintained on extracorporeal life support

OBJECTIVE

Anticoagulation with heparin is standard of care for patients maintained on extracorporeal life support. Very limited evidence exists for the use of alternative anticoagulants during extracorporeal life support. Patients with heparin-induced thrombocytopenia, heparin resistance, and evidence of significant thrombosis while on heparin may be candidates for alternative anticoagulation. The objective of this analysis is to present evidence for the use of bivalirudin during extracorporeal life support in pediatric patients.

DESIGN

Case series.

SETTING

University of California, Davis Medical Center.

PATIENTS

Twelve critically ill, pediatric patients receiving bivalirudin for anticoagulation during extracorporeal life support.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Twelve patients meeting entry criteria received bivalirudin during the study period. The median patient age was 8 days (range, 1 d to 6 yr). Eight patients were neonates. Eight patients were male. Nine patients were supported with venoarterial extracorporeal life support. Median duration of extracorporeal life support was 226 hours (range, 111-913) and median time on bivalirudin was 92 hours (range, 60-230). Bivalirudin bolus doses were administered to select patients without bleeding complications. The maintenance dose that corresponded with initial target activated partial thromboplastin time ranged from 0.045 to 0.48 mg/kg/hr with a median rate of 0.16 mg/kg/hr. The median dose for days 1, 3, and 5 was 0.135, 0.175, and 0.267 mg/kg/hr, respectively. The correlation (r2) between dose adjustment and activated partial thromboplastin time response was 0.264.

CONCLUSIONS

This is the largest case series describing the use of a direct thrombin inhibitor in pediatric extracorporeal life support patients. The maintenance dose range reflected considerable inter-patient variability. There was an observed increase in dose requirements with time. Bivalirudin, with close monitoring, is a potential option for pediatric patients on extracorporeal life support who have developed heparin-induced thrombocytopenia, heparin resistance, or significant thrombosis while on heparin.

Recombinant factor VIIa for uncontrollable bleeding in patients with extracorporeal membrane oxygenation: report on 15 cases and literature review

Introduction

Bleeding is the most frequent complication in patients receiving venoarterial or venovenous extracorporeal membrane oxygenation (ECMO). Recombinant activated factor VII (rFVIIa) has been used in these patients with conflicting results. We describe our experience with rFVIIa for refractory bleeding in this setting and review the cases reported in the literature.

Methods

Clinical characteristics, demographics, bleeding, thrombotic complications, mortality, and rFVIIa administration were retrospectively collected for analysis from the electronic charts of the 15 patients in our intensive care unit who received rFVIIa while being given ECMO from January 2006 to March 2011.

Results

Fifteen patients received rFVIIa for persistent bleeding under venoarterial (n = 11) or venovenous (n = 4) ECMO. Bleeding dramatically decreased in 14 patients, without a major thrombotic event, except in one patient in whom a major stroke could not be ruled out. Two circuits were changed within the 48 hours after rFVIIa administration for clots in the membrane and decreased oxygenation but without massive clotting. The mortality rate was 60%.

Conclusions

rFVIIa use for intractable hemorrhaging in patients receiving ECMO controlled bleeding, without major thrombotic events, and with 60% dying. Hence, its use warrants discussion, and clinicians should be aware of the possibility of potentially life-threatening systemic thrombosis, emboli, or circuit clotting. Whether rFVIIa can save the lives of such patients remains to be determined.

ECMO-Assisted Esophagectomy after Left Pneumonectomy

Background

Esophagectomy after pneumonectomy has been rarely reported, mainly due to the technical difficulty in performing this surgical approach. Conventional intubation to the contralateral respiratory passage is technically challenging, while the homolateral respiratory tract is absent, making oxygenation impossible.

Methods

To overcome this problem, we used venoarterial (VA) extracorporeal membrane oxygenation (ECMO) which can help achieve gas exchange despite the collapsed lung and provide a clear unobstructed surgical field for esophagectomy.

Results

We obtained satisfactory outcomes with VA ECMO in our treated patient.

Conclusions

This technique may be an excellent option for the treatment of complex situations such as esophagectomy after pneumonectomy.

The Microcirculation Is Unchanged in Neonates with Severe Respiratory Failure after the Initiation of ECMO Treatment

Purpose. Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is known to improve cardiorespiratory function and outcome in neonates with severe respiratory failure. We tested the hypothesis that VA-ECMO therapy improves the microcirculation in neonates with severe respiratory failure. Methods. This single-center prospective observational pilot study took place in an intensive care unit of a level III university children's hospital. Twenty-one-term neonates, who received VA-ECMO treatment, were included. The microcirculation was assessed in the buccal mucosa, using Orthogonal Polarization Spectral imaging, within 24 hours before (T1) and within the first 24 hours after initiation of ECMO treatment (T2). Data were compared to data of a ventilated control group (N = 7). Results. At baseline (T1), median functional capillary density (FCD), microvascular flow index (MFI), and heterogeneity index (HI) did not differ between the ECMO group and the control group. At T2 the median FCD was lower in the control group (median [range]: 2.4 [1.4–4.2] versus 4.3 [2.8–7.4] cm/cm²; P value <0.001). For MFI and HI there were no differences at T2 between the two groups. Conclusion. The perfusion of the microcirculation does not change after initiation of VA-ECMO treatment in neonates with severe respiratory failure.

Long-term support with an ambulatory percutaneous paracorporeal artificial lung

BACKGROUND

Conventional extracorporeal membrane oxygenation is bulky and non-ambulatory and requires multiple blood transfusions. We hypothesized that a percutaneous, paracorporeal artificial lung (PAL) could be established through a single venous cannulation to provide long-term ambulatory respiratory support.

METHODS

Our PAL system was tested in 11 healthy sheep. An Avalon Elite dual-lumen cannula (DLC), inserted through the right jugular vein into the superior vena cava, right atrium, and inferior vena cava, was connected to a CentriMag pump and compact hollow-fiber gas exchanger, forming a short-circuit PAL system. All sheep were moved to intensive care unit and were ambulatory after anesthesia recovery. Hemodynamics and device performance were measured daily.

RESULTS

The ambulatory PALs were successfully established in all sheep. The sheep were awake, ate, and moved freely in the metabolic cage, with no need of artificial nutrition or blood transfusion. All sheep had stable hemodynamics, with 2 liters/min of average circuit flow and hemoglobin levels exceeding 9.2 g/dl throughout the experiment. A progressive decrease of oxygen transfer and carbon dioxide removal capacity was observed. Sheep were euthanized between 10 and 24 days for bleeding (n = 2), gas exchanger failure (n = 6), and DLC issues (n = 3).

CONCLUSIONS

We successfully established long-term ambulatory PAL for up to 24 days in 11 animals using our patented DLC through a single-site percutaneous venous cannulation. Critical bleeding/thrombosis formation and gas exchanger durability remain two major challenges for long-term-ambulatory PAL.

Extracorporeal membrane oxygenation for ARDS in adults

A 41-year-old woman presents with severe community-acquired pneumococcal pneumonia. Chest radiography reveals diffuse bilateral infiltrates, and hypoxemic respiratory failure develops despite appropriate antibiotic therapy. She is intubated and mechanical ventilation is initiated with a volume- and pressure-limited approach for the acute respiratory distress syndrome (ARDS). Over the ensuing 24 hours, her partial pressure of arterial oxygen (Pao2) decreases to 40 mm Hg, despite ventilatory support with a fraction of inspired oxygen (Fio2) of 1.0 and a positive end-expiratory pressure (PEEP) of 20 cm of water. She is placed in the prone position and a neuromuscular blocking agent is administered, without improvement in her Pao2. An intensive care specialist recommends the initiation of extracorporeal membrane oxygenation (ECMO).

Acquired von Willebrand syndrome in patients with extracorporeal life support (ECLS)

PURPOSE

Extracorporeal life support (ECLS) is used for patients with refractory heart failure with or without respiratory failure. This temporary support is provided by blood pumps which are connected to large vessels. Bleeding episodes are a typical complication in patients with ECLS. Recently, several studies illustrated that acquired von Willebrand syndrome (AVWS) can contribute to bleeding tendencies in patients with long-term ventricular assist devices (VAD). AVWS is characterized by loss of the high molecular weight (HMW) multimers of von Willebrand factor (VWF) as a result of high shear stress and leads to impaired binding of VWF to platelets and to subendothelial matrix. Since ECLS and VAD share several features, we investigated patients with ECLS for AVWS.

METHODS

We analyzed 32 patients with ECLS and 19 of them without support. To diagnose AVWS, ratios of ristocetin cofactor activity (VWF:RCo) and collagen binding capacity (VWF:CB) to VWF antigen (VWF:Ag) were employed in conjunction with multimeric analysis.

RESULTS

Reduced VWF:RCo/VWF:Ag ratios were identified in 28 ECLS patients. Furthermore, VWF:CB/VWF:Ag ratios were decreased in 31 patients. HMW multimers of VWF were missing in the same 31 patients. Thus, 31 of 32 ECLS patients presented with AVWS. Twenty-two of the 32 patients suffered from bleeding complications. Without support, AVWS was not detectable in any analyzed patient.

CONCLUSION

Our data indicate that AVWS is a typical disorder in patients with ECLS. We hypothesize that AVWS could contribute to aggravation of bleeding tendencies in ECLS patients.

Cardiogenic shock following administration of propofol and fentanyl in a healthy woman: a case report

Introduction

Cardiogenic shock is very uncommon in healthy people. The differential diagnosis for patients with acute heart failure in previously healthy hearts includes acute myocardial infarction and myocarditis. However, many drugs can also depress myocardial function. Propofol and fentanyl are frequently used during different medical procedures. The cardiovascular depressive effect of both drugs has been well established, but the development of cardiogenic shock is very rare when these agents are used.

Case presentation

After a minor surgical intervention, a 32-year-old Caucasian woman with no significant medical history went into sudden hemodynamic deterioration due to acute heart failure. An urgent echocardiogram showed severe biventricular dysfunction and an estimated left ventricular ejection fraction of 20%. Extracorporeal life support and mechanical ventilation were required. Five days later her ventricular function had fully recovered, which allowed the progressive withdrawal of medical treatment. Prior to her hospital discharge, cardiac MRI showed neither edema nor pathological deposits on the delayed contrast enhancement sequences. At her six-month follow-up examination, the patient was asymptomatic and did not require treatment.

Conclusion

Although there are many causes of cardiogenic shock, the presence of abrupt hemodynamic deterioration and the absence of a clear cause could be related to the use of propofol and fentanyl.