[A critical carol : Being an essay on anemia, suffocation, starvation, and other forms of intensive care, after the manner of Dickens]

Irgendwo in den USA – Einige Tage vor Heiligabend wird der angetrunkene Charlie Cratchit bei dem Versuch, eine Straße zu überqueren, von einem Bus angefahren und schwer verletzt: Rippenserienfraktur, Femur- und Fibulafraktur, Milz- und Pankreaslazeration, Darmrisse. In einem US-amerikanischen Krankenhaus der Maximalversorgung wird er operativ versorgt und anschließend auf die Intensivtherapiestation verlegt und dort kontinuierlich von einem namenlosen, sehr erfahrenen Arzt betreut. Vier Tage vor Heiligabend, erscheint am Patientenbett der Geist des berühmten britischen Physiologen Ernest Henry Starling. Er tritt in einen Dialog mit dem namenlosen Arzt, interessiert sich sehr für den Swan-Ganz-Katheter und verschwindet dann wieder. Die Besuche wiederholen sich in den kommenden 3 Nächten. Einmal kritisiert er Cratchits niedrigen Hämatokrit, beim nächsten Mal zeigt er sich unzufrieden mit der Respiratoreinstellung, und beim letzten Besuch ist er äußerst besorgt über den Ernährungszustand des Patienten. Der namenlose Arzt ist zunächst indigniert über des Geistes Kritik und Belehrungen, erkennt aber, dass darin der Schlüssel zu Cratchits Genesung liegt und handelt letztlich nach seinen Vorschlägen. Mit Erfolg: Nach der vom Geist Starlings angeregten Umstellung der maschinellen Ventilation, Gabe von 3 Erythrozytenkonzentraten und Aufnahme einer parenteralen Ernährung kann Charlie Cratchit am Weihnachtsabend extubiert und am Neujahrstag von der Intensivtherapiestation entlassen werden. In diesem Essay hat Robert Bartlett Charles Dickens’ „Weihnachtsgeschichte“ in die Welt der Intensivmedizin verlegt. Sie soll den Intensivmediziner anregen, therapeutische Interventionen wie maschinelle Ventilation, hämodynamische Interventionen und Gabe von Blutprodukten kritisch zu hinterfragen. Hintergrundinformationen und Kommentare zu den angesprochenen aktuellen Problemen der modernen Intensivmedizin ergänzen den Essay.

Enhancing analytical accuracy of intravascular electrochemical oxygen sensors via nitric oxide release using S-nitroso-N-acetyl-penicillamine (SNAP) impregnated catheter tubing

Implantable medical devices are an integral part of primary/critical care. However, these devices carry a high risk for blood clots, caused by platelet aggregation on a foreign body surface. This study focuses on the development of a simplified approach to create nitric oxide (NO) releasing intravascular electrochemical oxygen (O₂) sensors with increased biocompatibility and analytical accuracy. The implantable sensors are prepared by embedding S-nitroso-N-acetylpenacillamine (SNAP) as the NO donor molecule in the walls of the catheter type sensors. The SNAP-impregnated catheters were prepared by swelling silicone rubber tubing in a tetrahydrofuran solution containing SNAP. Control and SNAP-impregnated catheters were used to fabricate the Clark-style amperometric PO₂ sensors. The SNAP-impregnated sensors release NO under physiological conditions for 18 d as measured by chemiluminescence. The analytical response of the SNAP-impregnated sensors was evaluated in vitro and in vivo. Rabbit and swine models (with sensors placed in both veins and arteries) were used to evaluate the effects on thrombus formation and analytical in vivo PO₂ sensing performance. The SNAP-impregnated PO₂ sensors were found to more accurately measure PO₂ levels in blood continuously (over 7 and 20 h animal experiments) with significantly reduced thrombus formation (as compared to controls) on their surfaces.

Rodent Skeletal Muscle Metabolomic Changes Associated With Static Cold Storage

OBJECTIVE

The aim of this study was to evaluate the impact of static cold storage preservation on skeletal muscle metabolism using a rodent model.

METHODS

Sixteen male Lewis rats (250 ± 25 g) were distributed into 4 groups, including naive control, warm ischemia for 2 hours, static warm storage for 6 hours, and static cold storage for 6 hours. Energy status, metabolomics profiling, and histopathology of the muscle were analyzed.

RESULTS

In the warm ischemia and static warm storage groups, glycolytic pathway metabolites decreased, but the Krebs cycle metabolite of succinate and the purine degradation product of hypoxanthine accumulated. Increased succinate and hypoxanthine levels were associated with increased injury severity scores. During static cold storage, the glycolytic pathway activity and the energy status were preserved. Succinate and hypoxanthine levels showed no significant difference from the naive group.

CONCLUSION

Warm ischemia results in reduced glycolysis and Krebs cycle metabolites. Static cold storage preserves the glycolytic pathway and represents a favorable contribution to cellular energy demand. Succinate and hypoxanthine might be used as novel potential biomarkers for the assessment of viability and injury severity.

[The old man and the I sea U : Essay on faith, fate and evidence - after the manner of Hemingway]

Robert Bartlett, emeritus Professor of surgery at the University of Michigan in Ann Arbor, USA, transformed classical works of world literature (Charles Dickens: A Christmas Carol, Lewis Carroll: Alice in Wonderland) into teaching aids for advanced training in intensive care medicine. He recently turned his hand to the well-known work of Ernest Hemingway: the Nobel Prize winning novel The Old Man and the Sea. Subsequent to Robert Bartlett's essay this article provides background information and comments on the current problems in modern intensive care medicine addressed in his essay.

Hematological changes during short-term tidal flow extracorporeal life support

Various methods exist in the clinical practice of long-term venovenous (VV) extracorporeal life support (ECLS). Among the clinical techniques used are single venous access with a dual-lumen catheter, and cannulation of the jugular and femoral veins. Tidal flow VV ECLS uses a single-lumen catheter to achieve both venous drainage and arterialized reinfusion through a series of tubing occluders that are automated by a pump. A single venous occluder tidal flow system with a 15 Fr single-lumen cannula (n- 6) and passive filling M pump was compared to a conventional 14 Fr dual-lumen cannula (n- 7) and roller pump for four hours of VV ECLS. The changes in platelet count and plasma-free hemoglobin (pHgb) were compared. The results showed a decline in platelet counts typical of ECLS in both groups that were not significantly different from each other. A small elevation in pHgb did not rise above normal clinical levels of 15 mg/dL in either group after four hours of ECLS. Some recirculation was observed and needs to be addressed in future studies. Single occluder tidal flow ECLS may be feasible and efficacious for long-term application once recirculation is resolved and the system evaluated for long-term support.

A simple technique to prevent limb ischemia during veno-arterial ECMO using the femoral artery: the posterior tibial approach

Lower extremity ischemia is common when the femoral artery is used for veno-arterial extracorporeal membrane oxygenation (VA ECMO). We describe a new technique to reperfuse the extremity. The ipsilateral posterior tibial artery is exposed via a small incision behind the medial malleolus. The vessel is cannulated in a retrograde fashion and connected to the arterial limb of the ECMO circuit.

Thirty-six patients received a posterior tibial reperfusion cannula: average flow was 155.8 ml/min and increased over the initial 24 hours. Fifty-eight percent received the posterior tibial cannula within 6 hours of ECMO initiation and none sustained permanent lower extremity injury. Of the remaining 42%, three required amputation or developed permanent neurologic injury. Overall survival was 41%.

Cannulation of the posterior tibial artery is a simple technique to reperfuse the lower extremity during VA ECMO. The cannula should be inserted within 6 hours of ECMO initiation to avoid irreversible ischemic damage.

Current status of extracorporeal life support (ECMO) for cardiopulmonary failure

Extracorporeal life support with artificial heart and lung for cardiopulmonary failure is commonly called extracorporeal membrane oxygenation (ECMO). ECMO can provide partial or total support, is temporary, and requires systemic anticoagulation. ECMO controls gas exchange and perfusion, stabilizes the patient physiologically, decreases the risk of ongoing iatrogenic injury, and allows ample time for diagnosis, treatment, and recovery from the primary injury or disease. ECMO is used in a variety of clinical circumstances and the results depend on the primary indication. ECMO provides life support but is not a form of treatment. Survival ranges from 30% in extracorporeal cardiopulmonary resuscitation to 95% for neonatal meconium aspiration syndrome. The major limitations to widespread applications are the need for anticoagulation and bleeding complications. However, nowadays, the new devices allow only minor bleeding that is rarely a fatal complication. Research on non-thrombogenic surfaces holds the promise of prolonged extracorporeal circulation without anticoagulation and without bleeding. The next decade may bring routine application of ECMO to all advanced Intensive Care Units where patients with profound respiratory and cardiac failure are treated.

Assessment of liver function during extracorporeal membrane oxygenation in the non-heart beating donor swine

INTRODUCTION

Although the use of non-heart beating donors (NHBD) could bridge the widening gap between organ demand and supply, its application to liver transplantation is limited due to warm ischemia (WI), biliary tree injury, and inadequate organ assessment. Warm blood reperfusion using extracorporeal membrane oxygenation (ECMO) can be a suitable option to reduce WI in organs from NHBD, allowing one to determine hepatic flow characteristics and bile production and facilitating assessment of organ viability.

METHODS

This work evaluates the use of warm blood veno-arterial ECMO reperfusion in NHBD swine. Systemic and hepatic hemodynamics, bile, urine, and mixed venous blood were measured. After baseline data collection, 10 kU heparin was given intravenously followed by 1 g KCl to elicit cardiac arrest (CA). ECMO was started after 30 or 60 minutes of CA and kept running for 120 minutes.

RESULTS

One-way repeated measures analysis of variance (ANOVA) with Tukey test analysis was used within a group. Two-way ANOVA was used between groups. ECMO can restore venous SO2 and pH in both groups; the values were close to baseline in the 30-minute CA group. Also, in this group, bile production was > 65% from baseline early during reperfusion and its value was lower in the longer CA group < 55% (P < .001). Aspartate aminotransferase (AST) was doubled at the end of ECMO support in the 60-minute CA group (P < .05).

CONCLUSION

In this preheparinized NHBD swine model, ECMO support restores liver perfusion, oxygenation, and bile production after 60 minutes of CA. Quantification and analysis of bile production could be a determinant of liver function during ECMO resuscitation, and it may be a predictor of graft viability before transplantation.

An artificial lung reduces pulmonary impedance and improves right ventricular efficiency in pulmonary hypertension

OBJECTIVE

Artificial lungs may have a role in supporting patients with end-stage lung disease as a bridge or alternative to lung transplantation. This investigation was performed to determine the effect of an artificial lung, perfused by the right ventricle in parallel with the pulmonary circulation, on indices of right ventricular load in a model of pulmonary hypertension.

METHODS

Seven adult male sheep were connected to a low-resistance membrane oxygenator through conduits anastomosed end to side to the pulmonary artery and left atrium. Banding of the distal pulmonary artery generated acute pulmonary hypertension. Data were obtained with and without flow through the device conduits. Outcome measures of right ventricular load included hemodynamic parameters, as well as analysis of impedance, power consumption, wave reflections, cardiac efficiency, and the tension-time index.

RESULTS

The model of pulmonary hypertension increased all indices of right ventricular load and decreased ventricular efficiency. Allowing flow through the artificial lung significantly reduced mean pulmonary artery pressure, zero harmonic impedance, right ventricular power consumption, amplitude of reflected waves, and the tension-time index. Cardiac efficiency was significantly increased.

CONCLUSIONS

An artificial lung perfused by the right ventricle and applied in parallel with the pulmonary circulation reduces ventricular load and improves cardiac efficiency in the setting of pulmonary hypertension. These data suggest that an artificial lung in this configuration may benefit patients with end-stage lung disease and pulmonary hypertension with right ventricular strain.

Results of a phase I trial evaluating a liver support device utilizing albumin dialysis

BACKGROUND

We have previously reported the clearance of protein-bound and water-soluble hepatic toxins, in vitro and in an animal model, using albumin dialysis as an extracorporeal hepatic support (ECHS) device.

OBJECTIVE

The objective of this study was to evaluate albumin dialysis through a phase I clinical trial. We hypothesized that albumin dialysis would (1) decrease elevated levels of hepatic toxins, (2) increase the Fischer ratio, and (3) decrease hepatic encephalopathy (HES) and intracranial pressure (ICP), while (4) maintaining stable hemodynamics.

METHODS

Patients with acute liver failure were treated with an ECHS device utilizing continuous hemodiafiltration with continuous albumin dialysis. Mean arterial blood pressure (MAP), heart rate (HR), systemic venous oxygen saturation (Svo(2)), ICP, and HES were recorded. Blood samples were evaluated for hepatic toxins and factor VII levels.

RESULTS

Nine patients were enrolled (status I, n = 5; status IIA, n = 4). There was no significant change in MAP, HR, or Svo(2) (MAP: Pre = 81 +/- 5.6 mm Hg, Post = 79 +/- 5.9 mm Hg, P =.70; HR: Pre = 104 +/- 5.2 bpm, Post = 107 +/- 6.2 bpm, P =.62; Svo(2): Pre = 72 +/- 3.5, Post = 71 +/- 1.7, P =.77). There was a decrease in the ammonia and total bilirubin levels (NH(3): Pre = 129.8 +/- 23.8 mg/dL, Post = 63.9 +/- 16.1 mg/dL, P =.01; total bilirubin: Pre = 20.3 +/- 2.5 mg/dL, Post = 17.6 +/- 2.7 mg/dL, P =.4). There was a significant increase of the Fischer ratio and factor VII levels (Fischer ratio: Pre = 0.98 +/- 0.2, Post = 2.17 +/- 0.5, P =.038; factor VII: Pre = 13.9 +/- 4.9, Post = 23.2 +/- 4.8, P =.015). There was a significant decrease in the HES and ICP (HES: Pre = 3.8 +/- 0.1, Post = 2 +/- 0.7, P =.02; ICP: Pre = 37 +/- 3.9, Post = 13.3 +/- 2.8, P =.048). Of 5 status I patients, 1 recovered native hepatic function and 3 were bridged to transplantation.

CONCLUSIONS

This phase I study suggests that albumin dialysis as a liver support device is safe and effective in clearing hepatic toxins, with an associated decrease in the HES and ICP. This encouraging efficacy data warrant further investigation with a phase II/III trial.

Development of an implantable artificial lung: challenges and progress

Unlike dialysis, which functions as a bridge to renal transplantation, or a ventricular assist device, which serves as a bridge to cardiac transplantation, no suitable bridge to lung transplantation exists. Our goal is to design and build an ambulatory artificial lung that can be perfused entirely by the right ventricle and completely support the metabolic O2 and CO2 requirements of an adult. Such a device could realize a substantial clinical impact as a bridge to lung transplantation, as a support device immediately post-lung transplant, and as a rescue and/or supplement to mechanical ventilation during the treatment of severe respiratory failure. Research on the artificial lung has focused on the design, mode of attachment to the pulmonary circulation, and intracorporeal versus paracorporeal placement of the device.

The use of extracorporeal life support in adult patients with primary cardiac failure as a bridge to implantable left ventricular assist device

BACKGROUND

Extracorporeal life support (ECLS) is an effective technique for providing emergent circulatory assistance, and may represent a life-saving option in patients who might not initially be considered a candidate for other forms of circulatory support (extracorporeal or implantable left ventricular assist device [LVAD]). In the setting of cardiac arrest, ECLS represents the only viable method of initiating circulatory support. However, ECLS has a number of disadvantages that include high complication rates (eg, stroke, bleeding) and a limited duration of potential support, which have prevented its widespread acceptance, particularly in the adult population. With the increased successful application of long-term implantable LVADs as a bridge to transplant, the major limitation of ECLS could be overcome by bridging patients to a long-term implantable LVAD ("bridge to bridge"), thereby reducing the reluctance to utilize ECLS when indicated. After acquisition of the HeartMate LVAD (Thermo Cardiosystems, Inc, Woburn, MA) we investigated the use of ECLS as a bridge to an implantable LVAD and subsequent transplantation in selected high-risk patients.

METHODS AND RESULTS

From Oct 1, 1996 to Sept 30, 2000, 33 adult patients presenting with cardiac arrest or severe hemodynamic instability were placed on ECLS for the bridge to bridge indication. Of the 33 patients, 10 patients survived to LVAD implant, 1 was bridged directly to transplant, 5 weaned from ECLS, and 16 died on ECLS. Overall, 12 patients survived to discharge. One-year actuarial survival from the initiation of ECLS was 36%. One-year actuarial survival from the time of LVAD implant, conditional on surviving ECLS, was 80%.

CONCLUSIONS

The 1-year survival of adult patients placed on ECLS and who subsequently survived to an implantable LVAD was favorable. These data support a strategy of ECLS to implantable LVAD bridge to heart transplant in adult patients who are in need of circulatory support and who are not initially candidates for other forms of mechanical support. The favorable results of this strategy support utilization of ECLS even in situations where myocardial recovery is thought to be unlikely.

Assessment of an extracorporeal life support to LVAD bridge to heart transplant strategy

BACKGROUND

Extracorporeal life support (ECLS) is an effective technique for providing emergent circulatory assistance. However, its use in adult patients is associated with poor survival when myocardial function fails to recover. Due to the prolonged waiting times for heart transplantation, ECLS as a bridge to transplant is associated with poor survival. In addition, ECLS has been reported to be a significant risk factor for death after bridging to an implantable left ventricular assist device (LVAD). After acquisition of the HeartMate LVAD (Thermo Cardiosystems, Inc) in October 1996, we began using ECLS as a bridge to an implantable LVAD and subsequently transplantation in selected high-risk patients.

METHODS

From October 1, 1996 to December 1, 1999, 60 adult patients presenting with cardiogenic shock were evaluated for circulatory assistance.

RESULTS

Twenty-five patients (group 1) with cardiac arrest or severe hemodynamic instability and multiorgan failure were placed on ECLS. Eight patients survived to LVAD implant, 1 was bridged directly to transplant, and 4 weaned from ECLS. Nine patients in group 1 survived to discharge. Thirty patients (group 2) underwent LVAD implant without ECLS. Twenty-three were bridged to transplant, with 22 surviving to discharge. Five patients (group 3) were placed on extracorporeal ventricular assist with 3 bridged to transplant and all surviving to discharge. One-year actuarial survival from the initiation of circulatory support was 36% (group 1), 73% (group 2), and 60% (group 3). One-year actuarial survival from the time of LVAD implant in group 1, conditional on surviving ECLS, was 75% (p = NS compared with group 2).

CONCLUSIONS

In selected high-risk patients, LVAD survival after initial ECLS was not different from survival after LVAD support alone. An initial period of resuscitation with ECLS is an effective strategy to salvage patients with cardiac arrest or extreme hemodynamic instability and multiorgan injury.

A novel stable reproducible model of hepatic failure in canines

BACKGROUND

Stable and reproducible large animal models of hepatic failure, which allow the assessment of liver-assist devices, are not available. Our objective was to develop a physiologically stable animal model of hepatic failure on which the safety and efficacy of an extracorporeal liver-assist device can be tested. We hypothesized that a surgical model which consists of an end-to-side portocaval shunt combined with common bile duct ligation and transection would create hepatic failure with: (1) elevations in amino transferases, total bilirubin, and ammonia; (2) a decrease in the ratio of branched chain to aromatic amino acids; and (3) histologic evidence of hepatic injury.

METHODS

Eleven mongrel dogs underwent common bile duct transection and an end-to-side portocaval shunt. Aminotransferases (AST, ALT), total bilirubin, ammonia, and branched chain and aromatic amino acids were measured prior to operation (baseline) and after 9 days. A necropsy was performed on Postoperative Day 9 and liver biopsies were obtained for histology.

RESULTS

By Postoperative Day 9, AST, ALT, total bilirubin, and ammonia values were significantly elevated compared to baseline (P < 0.02). The ratio of branched chain to aromatic amino acids was significantly reduced compared to baseline (P < 0.003). There was histologic evidence of cholestasis and inflammation.

CONCLUSION

Portocaval shunt with common bile duct transection produces liver failure with elevations in aminotransferases, total bilirubin, and ammonia, a decreased branched chain to aromatic amino acid ratio, and histologic inflammation. Unlike ischemic or chemically induced models of liver failure, the dogs were hemodynamically and neurologically stable. This model can be used to test the safety and efficacy of liver-assist devices aimed at temporizing the detoxification functions of the failing liver.

Extracorporeal life support in the management of severe respiratory failure

ECLS is a safe and effective means to keep patients alive during severe respiratory failure that would otherwise be fatal. In addition to direct and indirect treatment of the lungs during ECLS, the technique allows days of time for study and treatment of other conditions and other organ failure. The technique has been refined in newborn infants and children, in whom survival rates are high and the technology is proven by prospective randomized trials. ECLS is usually applied to adults with respiratory failure when the mortality risk is over 80%. With these indications, the survival rate in experienced centers is 50% to 60%. A new prospective, randomized trial of ECLS in adult patients is underway in the United Kingdom. In the meantime, intensivists who are charged with the management of moribund ARDS patients who fail to respond to other methods of therapy should consider the risks versus the benefits of transferring such patients to an ECLS center.

Hemolytic potential of hydrodynamic cavitation

The purpose of this study was to determine the hemolytic potentials of discrete bubble cavitation and attached cavitation. To generate controlled cavitation events, a venturigeometry hydrodynamic device, called a Cavitation Susceptibility Meter (CSM), was constructed. A comparison between the hemolytic potential of discrete bubble cavitation and attached cavitation was investigated with a single-pass flow apparatus and a recirculating flow apparatus, both utilizing the CSM. An analytical model, based on spherical bubble dynamics, was developed for predicting the hemolysis caused by discrete bubble cavitation. Experimentally, discrete bubble cavitation did not correlate with a measurable increase in plasma-free hemoglobin (PFHb), as predicted by the analytical model. However, attached cavitation did result in significant PFHb generation. The rate of PFHb generation scaled inversely with the Cavitation number at a constant flow rate, suggesting that the size of the attached cavity was the dominant hemolytic factor.

Respiratory failure. Conventional and high-tech support

Although significant progress has been made in the treatment of patients with acute lung failure in the critical care setting, the mortality rate from acute lung injury and ARDS is unacceptably high, given the numbers of patients treated for these syndromes each year. The improved understanding of the pathophysiology of respiratory failure from basic science and clinical research is reflected in improved survival rates over the years. Advances in the mechanical ventilator (through microprocessor technology); biosurface technology; liquid ventilation; and, in some cases, returning to so-called "antiquated" practices of patient care (e.g., prone positioning) seem to have had an impact nonetheless. As refinement continues to occur in these areas, morbidity and mortality from lung failure will have a lesser impact on patients as physicians treat the consequences of organ failure in the ICU.

Percutaneous cannulation for pediatric venovenous extracorporeal life support

BACKGROUND/PURPOSE

The objective of this study was to show the safety and efficacy of a method of percutaneous cannulation for venovenous extracorporeal life support (ECLS) access in nonneonatal (>10 kg) pediatric patients.

METHODS

Between June 1992 and October 1998, 26 pediatric patients (age range, 3 to 17 years; weight range, 19 to 100 kg) underwent attempted percutaneous cannulation for venovenous ECLS at our institution. Venous drainage access was attempted using a modified Seldinger technique via the right internal jugular vein (RIJ, n = 22) or right femoral vein (RFV, n = 4). Reinfusion access was attempted via the RFV (n = 19), RIJ (n = 4), or left femoral vein (n = 3).

RESULTS

The percutaneous technique was successful in 24 of 26 patients (92.3%). Maximum blood flow during ECLS was 80.1 +/- 30.0 mL/kg/min, generating a postmembrane lung outlet pressure of 138 +/- 54.8 mm Hg. Adequate gas exchange was achieved in all patients, and survival to discharge was 79.2%. There was no procedure-related mortality. Complications potentially related to the percutaneous technique included RIJ thrombosis (n = 1) detected after decannulation and cannula site bleeding (n = 3).

CONCLUSION

Percutaneous access may be used safely and effectively for venovenous ECLS in pediatric patients.

Use of the placenta as an artificial lung

Oxygen transfer across a single cotyledon of the human placenta was assessed by using three different perfusates in the maternal circuit: 1) M-199 culture medium, 2) human adult red blood cells (RBCs), and 3) perflubron. These maternal circuit perfusates were oxygenated with a membrane oxygenator. RBCs were perfused on the fetal side of the circuit and samples were taken preplacenta and postplacenta for each maternal perfusate. PO2 and PCO2 were measured and O2 transfer was calculated for each maternal perfusate. O2 transfer per single cotyledon (mean +/- SE) was 0.18 +/- 0.04, 0.20 +/- 0.03, and 0.15 +/- 0.05 ccO2/min when using: 1) M-199, 2) RBCs, and 3) perflubron, respectively. O2 transfer per kilogram of placental tissue was 13.08 +/- 2.78, 14.57 +/- 2.05, and 10.43 +/- 3.79 ccO2/kg per minute when using: 1) M-199, 2) RBCs, and 3) perflubron, respectively. When extrapolated to the individual weights of the entire placenta, the O2 transfer was 9.15 +/- 1.95, 10.20 +/- 1.43, and 7.30 +/- 2.65 when using: 1) M-199, 2) RBCs, and 3) perflubron, respectively. We conclude from these data that O2 transfer can be accomplished during placental perfusion. Larger studies are required to differentiate efficacy among the three maternal circuit perfusates.

Reduced platelet activation and thrombosis in extracorporeal circuits coated with nitric oxide release polymers

OBJECTIVE

To determine whether the use of nitric oxide (NO)-releasing polymers coated onto the inner surface of extracorporeal circuits can reduce platelet consumption and activation in the absence of systemic heparinization using a rabbit model of venovenous extracorporeal circulation.

DESIGN

Prospective, controlled trial.

SETTING

Research laboratory at an academic medical institution.

SUBJECTS

New Zealand White Rabbits.

INTERVENTIONS

Anesthetized, tracheotomized, and ventilated New Zealand White rabbits were injected with freshly prepared, 111In(oxine)3 labeled single donor platelets through the external jugular vein. After baseline measurements, these animals were placed on venovenous extracorporeal circulation through a 1-m control circuit or NO test circuit for 4 hrs at a blood flow rate of 109-118 mL/min via roller pump. Four groups were studied: systemically heparinized control circuits, systemically heparinized NO test circuits, nonheparinized control circuits, and nonheparinized NO test circuits. Platelet counts, fibrinogen levels, and plasma free indium levels were measured hourly. Circuits were rinsed and retained for gamma counting after the 4-hr run or when the circuit clotted. Four animals, one from each group, did not receive radiolabeled platelets so that the circuits could be preserved for scanning electron microscopic examination after the 4-hr study.

MEASUREMENTS AND MAIN RESULTS

Platelet consumption was significantly reduced in both the heparinized and nonheparinized NO test groups when compared with the controls (p < .0001 and p < .0004, respectively). Platelet adhesion to the extracorporeal circuits was significantly reduced in the nonheparinized test circuits when compared with the controls (p < .05). Scanning electron microscopic examination of the circuits revealed that in the absence of heparin and in the presence of a NO-releasing surface, platelets retained their spherical nonactivated shape.

CONCLUSIONS

The incorporation of NO into the surface of extracorporeal circuits reduces platelet consumption and eliminates the need for systemic heparinization in a rabbit model of extracorporeal circulation.

Extracorporeal life support: the University of Michigan experience

The University of Michigan experience with extracorporeal life support (ECLS) in 1000 consecutive patients between 1980 and 1998 is the largest series at one institution in the world. Among this patient population, survival to hospital discharge in moribund patients with respiratory failure was 88% in 586 neonates, 70% in 132 children, and 56% in 146 adults. Survival in moribund patients with cardiac failure was 48% in 105 children and 33% in 31 adults. This article describes the University of Michigan's overall ECLS patient experience, the progression of ECLS from laboratory experiments to clinical application at the bedside, the expansion of the technology to other centers, and current ECLS technology and outcomes. Despite the challenges faced in clinical research in this field, our experience and that of others has shown that ECLS saves lives of patients with acute cardiac or pulmonary failure in a variety of clinical settings.

Hemodynamic effect of a low-resistance artificial lung in series with the native lungs of sheep

BACKGROUND

An artificial lung with 1 to 6 month work life could act as a bridge to transplantation. A pumpless artificial lung has been developed.

METHODS

The artificial lung was placed in series with the native lungs of adult sheep. Hemodynamics were observed, as the right ventricle generated flow through the device. Through a left thoracotomy, two 20-mm grafts were anastomosed in an end-to-side fashion to the pulmonary artery. The grafts were externalized, and directed flow through the chest wall, to the extracorporeal lung. The animals were recovered, weaned from the ventilator, and when standing, flow was diverted through the device.

RESULTS

Five of 7 animals survived 24 hours with 75% to 100% of the cardiac output diverted through the device. All animals were active, with interest in food and water, and able to stand.

CONCLUSIONS

The right ventricle perfused the artificial lung with 75% to 100% of the cardiac output for 24 hours. This device demonstrates the feasibility of a pumpless pulmonary assist device relying on the right ventricle for perfusion.

Venovenous versus venoarterial extracorporeal life support for pediatric respiratory failure: are there differences in survival and acute complications?

OBJECTIVES

To examine the Extracorporeal Life Support Organization (ELSO) registry database of infants and children with acute respiratory failure to compare outcome and complications of venovenous (VV) vs. venoarterial (VA) Extracorporeal Life Support (ECLS).

DESIGN

Retrospective cohort study.

SETTING

ELSO registry for pediatric pulmonary support.

PATIENTS

All nonneonatal pediatric pulmonary support ECLS cases treated at U.S. centers and reported to the ELSO registry as of July 1997. Patients were excluded if they had one or more of the following diagnoses: hematologic-oncologic, cardiac, abdominal surgical, burn, metabolic, airway, or immunodeficiency disorder.

INTERVENTIONS

Venoarterial or venovenous extracorporeal life support for severe pulmonary failure.

MEASUREMENTS AND MAIN RESULTS

From 1986 to June of 1997, 763 pediatric patients met the inclusion criteria. Overall, 595 were initially managed with VA bypass, and 168 with VV bypass. The VA group was younger (mean +/- SD, 26.1+/-42.2 months for VA vs. 63.5+/-68.7 months for VV) and smaller (11.8+/-15.1 kg vs. 22.9+/-23.8 kg) (p<.001). There were no differences between groups in number of days on mechanical ventilation before ECLS, number of hours on ECLS, or number of hours on mechanical ventilation post-ECLS in survivors. Mean pH and Paco2 values, positive end-expiratory pressure, and mean airway pressure just before placing the patient on ECLS were also similar. VA-treated patients had higher Fio2 requirements (p = .034), lower Pao2 (p = .047), and lower Pao2/Fio2 ratio (p = .014) just before cannulation. There was a trend of higher peak inspiratory pressure in VA-treated patients (p = .053). Overall, survival rate was not different for the two groups (55.8% for VA vs. 60.1% for VV; p = .33). Central nervous system complications were not different between the two groups. Examination of the same variables was then conducted after dividing the patients into four subgroups. There were no significant differences in survival or complications during bypass between VV and VA modes of ECLS in any subgroup. Stepwise logistic regression modeling was performed to control for variables associated with the outcome survival for VV and VA-treated groups, and variables measured before bypass were identified as being associated with improved survival. There was a trend of improved survival in the VV-treated patients (p = .12).

CONCLUSIONS

Overall survival of pediatric patients with acute respiratory failure supported by VA or VV ECLS was comparable. A randomized clinical trial may be useful in clarifying these observations.

Emergency extracorporeal membrane oxygenation (ECMO)-supported percutaneous coronary interventions in the fibrillating heart

We describe two cases of refractory ventricular fibrillation complicating transcatheter interventional procedures. Extracorporeal membrane oxygenation was used in each to support percutaneous coronary revascularization in the fibrillating heart as a means of facilitating successful restoration of sinus rhythm. Cathet. Cardiovasc. Intervent. 48:402-405, 1999.

Recombinant Kunitz protease inhibitory domain of the amyloid beta-protein precursor as an anticoagulant in venovenous extracorporeal circulation in rabbits

Investigations were performed to characterize a recombinant Kunitz protease inhibitory domain of the amyloid beta-protein precursor (rKPI) as anticoagulants. After a single intravenous infusion of wild type rKPI into dogs, its elimination fit a two compartment model with a t1/2alpha and t1/2beta of 5 and 77 min, respectively. Further investigations determined if a variant form of rKPI with 178-fold more potent anti-factor Xa activity (rKPI-DD135, Ki = 0.9 nM) could serve as an anticoagulant in a rabbit model of extracorporeal circulation using a venovenous shunt. A prospective investigation was initiated to compare standard heparin (n = 8) at 400 U/kg with different infusion concentrations of rKPI-DD135. After a single intravenous infusion of 1.89 mg/kg of rKPI-DD135 followed by a constant infusion at 0.003 (n = 3), 0.03 (n = 7), or 0.3 (n = 5) mg/kg/min, the anti-factor Xa activity of the animals' plasma rapidly reaches a steady state for the two lower infusion concentrations of the agent. All infusions of rKPI-DD135 prolong the activated clotting time with less variation than that seen with heparin administration. rKPI-DD135 anticoagulation does not prevent a drop in the platelet counts. Fibrinogen levels decrease only slightly when the circuit is anticoagulated with rKPI-DD135. rKPI-DD135 markedly prolongs the APTT, has little effect on the PT, and reduces plasma prekallikrein and plasminogen activation. The 0.3 mg/kg/min infusion concentration of rKPI-DD135 results in reduced deposition of 111Indium-labeled platelets on the circuit when compared to heparin. Last, after a steady state level is achieved, 60% of the plasma anti-factor Xa activity of rKPI-DD135 is eliminated within 60 min after stopping the infusion. These data show the rKPI-DD135 can provide single agent anticoagulation in a rabbit extracorporeal circuit. Development of short acting factor Xa inhibitors may be useful anticoagulants for cardiopulmonary bypass.

Determination of the in vivo cavitation nuclei characteristics of blood

Cavitation has been documented in the in vitro testing of blood-handling devices. To predict whether cavitation will occur clinically, the nuclei content of blood and the threshold pressure for activation of the in situ nuclei must be characterized. A single-pass flow apparatus is described for determining the nuclei characteristics of blood. The flow apparatus consists of a syringe pump and a venturi-geometry hydrodynamic device, called a cavitation susceptibility meter (CSM). Blood is accelerated through the throat of the CSM, thus exposing the nuclei in the blood to a well-defined pressure profile. The apparatus was used in an ex vivo sheep model for the determination of the in vivo nuclei characteristics of blood. The active nuclei concentration of in vivo blood was measured to be at most 2.7 nuclei per liter of plasma at a minimum throat pressure of -1610 mm Hg gauge (i.e., tension of 900 mm Hg). At this pressure, bubble stability theory predicts the active nuclei to have a radius on the order of 0.3 microm. Based on these results, in vitro studies to determine the cavitation potential of blood-handling devices must utilize test fluids that contain a minimum nuclei size distribution and concentration. It cannot be assumed that in vivo blood is nuclei rich, such that it will cavitate at or near vapor pressure.

Extreme negative pressure does not cause erythrocyte damage in flowing blood

In extracorporeal circulation, negative pressure is thought to be a source of hemolysis. This study was designed to investigate the effects of extreme negative pressure on flowing blood. The study model was pipe flow. The hemolysis generated by negative pressure driven flow was compared with that generated by positive pressure driven flow of equal magnitude to control for the hemolytic effect of shear stress. A series of pressures (720, 600, 500, -500, -600, and -720 mm Hg; n = 8) was tested for pipe diameters of 0.04 and 0.16 cm, with a length-to-diameter ratio of 500. The pressure difference across the pipe (deltaP) was equal to the magnitude of the applied pressure. The hemolysis was quantified by the modified index of hemolysis (MIH). For both pipe diameters, MIH was found to not depend on the deltaP or the blood collection day (multiple regression analysis, p = 0.50 and p = 0.63, respectively). There was no statistically significant difference between the MIH for equal deltaP generated by positive or negative pressure (p = 0.50) for both pipe diameters tested. MIH did depend upon the pipe diameter, with 0.04 cm having higher MIH at all pressures (p = 0.0003). Thus, negative pressure is not a significant hemolytic factor in flowing blood.

Effect of blood flow rate on thrombogenesis in a rabbit extracorporeal circulation model

Blood flow is believed to affect the thrombogenicity of extracorporeal circulation (ECC). The purpose of this study was to look at the relationship between blood flow and thrombogenicity in a rabbit model of ECC. Rabbits were anesthetized and systematically heparinized. Bilateral jugular cannulation was performed, and the animals were placed on venovenous ECC. The circuits were composed of 1 m of 1/4 inch size surgical grade polyvinylchloride (PVC) tubing. ECC was maintained for 4 hours. Three experimental groups were studied: a high flow group (n=7; flow rate: 30 ml/min/Kg), low flow group (n=7; flow rate: 10 ml/mg/Kg), and no ECC group (n=7). Platelet count, fibrinogen concentration, PaO2/FiO2, and postmortem findings were evaluated. Platelet consumption was higher with high flow, and fibrinogen consumption was higher with low flow.

Extracorporeal resuscitation of cardiac arrest

OBJECTIVE

Extracorporeal support of heart and lung function (venoarterial perfusion) during cardiac arrest (ECPR) has been advocated as a means of improving survival following cardiac arrest. The authors retrospectively reviewed their institution's seven-year experience with this intervention.

METHODS

Emergency department patients and inpatients in cardiac arrest or immediately postarrest were considered candidates. ECPR was instituted using venoarterial bypass and was continued until patients regained sufficient cardiopulmonary function to allow weaning from the device or until their condition was deemed irrecoverable.

RESULTS

ECPR was attempted in 25 patients and successfully instituted in 21. Four patients (16%) were converted from ECPR to ventricular assist devices, two of whom survived and await transplantation. Seven additional patients were discharged from the hospital, resulting in an overall survival of 36%. Because none of the children treated survived, there was a trend toward higher age among survivors (survivors 40 +/- 14 yr, nonsurvivors 33 +/- 15 yr, p = 0.29). The duration of conventional CPR was shorter among survivors (survivors 21 +/- 16 min, nonsurvivors 43 +/- 32 min, p = 0.04), as was the duration of extracorporeal support (survivors 44 +/- 21 hr, nonsurvivors 87 +/- 96 hr, p = 0.18). Survival was seen only in patients whose conditions were amenable to a definitive therapeutic intervention, particularly cardiac arrest due to respiratory or pulmonary embolic disease. While four of the five patients treated in the ED were successfully supported, none survived to discharge.

CONCLUSION

In select patients with reversible disease, extracorporeal CPR can be used to successfully treat cardiac arrest. Further investigation into its most appropriate application is warranted.

Extracorporeal life support in pulmonary failure after trauma

OBJECTIVE

To present a series of 30 adult trauma patients who received extracorporeal life support (ECLS) for pulmonary failure and to retrospectively review variables related to their outcome.

METHODS

In a Level I trauma center between 1989 and 1997, ECLS with continuous heparin anticoagulation was instituted in 30 injured patients older than 15 years. Indication was for an estimated mortality risk greater than 80%, defined by a PaO2: FIO2 ratio less than 100 on 100% FIO2, despite pressure-mode inverse ratio ventilation, optimal positive end-expiratory pressure, reasonable diuresis, transfusion, and prone positioning. Retrospective analysis included demographic information (age, gender, Injury Severity Score, injury mechanism), pulmonary physiologic and gas-exchange values (pre-ECLS ventilator days [VENT days], PaO2:FIO2 ratio, mixed venous oxygen saturation [SvO2], and blood gas), pre-ECLS cardiopulmonary resuscitation, complications of ECLS (bleeding, circuit problems, leukopenia, infection, pneumothorax, acute renal failure, and pressors on ECLS), and survival.

RESULTS

The subjects were 26.3+/-2.1 years old (range, 15-59 years), 50% male, and had blunt injury in 83.3%. Pulmonary recovery sufficient to wean the patient from ECLS occurred in 17 patients (56.7%), and 50% survived to discharge. Fewer VENT days and more normal SvO2 were associated with survival. The presence of acute renal failure and the need for venoarterial support (venoarterial bypass) were more common in the patients who died. Bleeding complications (requiring intervention or additional transfusion) occurred in 58.6% of patients and were not associated with mortality. Early use of ECLS (VENT days < or = 5) was associated with an odds ratio of 7.2 for survival. Fewer VENT days was independently associated with survival in a logistic regression model (p = 0.029). Age, Injury Severity Score, and PaO2:FIO2 ratio were not related to outcome.

CONCLUSION

ECLS has been safely used in adult trauma patients with multiple injuries and severe pulmonary failure. In our series, early implementation of ECLS was associated with improved survival. Although this may represent selection bias for less intractable forms of acute respiratory distress syndrome, it is our experience that early institution of ECLS may lead to improved oxygen delivery, diminished ventilator-induced lung injury, and improved survival.

Nosocomial infections in adult patients undergoing extracorporeal membrane oxygenation

The use of extracorporeal membrane oxygenation (ECMO) for adult patients has increased in recent years. A retrospective cohort study of adult patients undergoing ECMO was performed between 19 February 1985 and 10 October 1995 to evaluate nosocomial infections. Seventy-one evaluable patients underwent ECMO for a total of 799 days. Forty-six infections were identified in 32 (45%) of 71 patients. There were 15 bloodstream infections, 13 lower respiratory infections, 11 urinary tract infections, and 7 miscellaneous infections. The rates of bloodstream infection (18.8 cases per 1,000 ECMO days) and urinary tract infection (13.8 cases per 1,000 ECMO days) were significantly higher than those reported through the Centers for Disease Control and Prevention / National Nosocomial Infection Surveillance System (P < .0001 and P < .001, respectively). The rate of bloodstream infection increased with the duration of ECMO cannulation. This study highlights the increased risk for nosocomial infections in this patient population. Infection may not be apparent, and increased physician awareness of infection risk is imperative.

Venovenous extracorporeal life support via percutaneous cannulation in 94 patients

STUDY OBJECTIVE

The objective of this study was to demonstrate the safety and utility of a method of percutaneous access for cannulation of adult patients for venovenous extracorporeal life support (ECLS).

DESIGN

A retrospective review of a patient series.

SETTING

A surgical ICU at a university teaching hospital.

PATIENTS

The study group consisted of 94 adults > 17 years old with respiratory failure who were placed on venovenous ECLS by means of percutaneous cannulation.

INTERVENTIONS

The cannulation of the internal jugular and femoral veins (FVs) using the Seldinger technique for venovenous ECLS.

MEASUREMENTS AND RESULTS

Between May 1992 and November 1997, we performed percutaneous cannulation for venovenous ECLS in 94 adult patients with respiratory failure. The mean (+/- SD) age was 36.1+/-12.7 years old (range, 17 to 65 years). The mean (+/-SD) weight was 80.7+/-22.3 kg (range, 36 to 156 kg). The right internal jugular vein (RIJV) was used for venous drainage access in all but four cases. The right FV (n = 86), the left FV (n = 3), or the RIJV (n = 4) was utilized for venous reinfusion. The maximum blood flow (+/-SD) during ECLS was 57.6+/-17.5 mL/kg/min (range, 22.4 to 127.8 mL/kg/min), with a postmembrane outlet pressure (+/-SD) of 146+/-43 mm Hg (range, 56 to 258 mm Hg) at the maximum flow rate. There were 11 unsuccessful percutaneous cannulation attempts. In three patients (3%), the complications consisted of arterial injury requiring operative cutdown and repair. In six patients (6%), cannula-site bleeding required pursestring suture reinforcement of the cannula site. One patient died from the perforation of the superior vena cava during cannulation.

CONCLUSIONS

Based on these data, we conclude that percutaneous cannulation may be utilized to provide venovenous ECLS in adults.

Can the clearance of tumor necrosis factor alpha and interleukin 6 be enhanced using an albumin dialysate hemodiafiltration system?

Patients with acute hepatic failure (AHF) have elevated levels of inflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6). Recently, we have shown selective hemodiafiltration with albumin dialysis, as an extracorporeal liver support device (ECLVS), to be effective in the clearance of multiple toxins that are elevated in AHF. Our objective was to evaluate whether ECLVS would be effective in the clearance of TNF-alpha and IL-6. An in vitro continuous hemodiafiltration circuit was used with single pass counter-current dialysis. A known amount of recombinant rat TNF-alpha and IL-6 was added to heparinized bovine blood and filtered across a polyalkyl sulfone hemofilter using matched filtration and dialysate flow rates. During 4 hours, the serial TNF-alpha and IL-6 concentrations were measured in the circulating blood, and the content of each cytokine was calculated using mass balance. For each cytokine, clearance was determined for two dialysate groups at constant temperature and pH (group 1: dialysate = 0.9 normal saline, n = 5; group 2: dialysate = albumin 2 gm/dl, n = 5). Analysis of data was performed using ANOVA and Student's t-test. There was improved clearance of TNF-alpha and IL-6 when albumin was used in the dialysate (81+/-0.09% of the initial TNF-alpha and 77+/-0.04% of the IL-6 quantities) compared with when 0.9 normal saline was used as the dialysate (58+/-0.14% of the initial TNF-alpha and 56+/-0.18% of the IL-6 quantities); p < 0.03. An ECLVS utilizing hemodiafiltration with albumin dialysis is more effective than conventional hemofiltration in the clearance of TNF-alpha and IL-6 and, therefore, may benefit patients with acute hepatic failure.

Partial liquid ventilation in adult patients with ARDS: a multicenter phase I-II trial. Adult PLV Study Group

OBJECTIVE

To evaluate the safety and efficacy of partial liquid ventilation (PLV) in adult patients with the acute respiratory distress syndrome (ARDS).

SUMMARY BACKGROUND DATA

Previous studies have evaluated gas exchange and the safety of PLV in adult patients with severe respiratory failure whose gas exchange was partially provided by extracorporeal life support (ECLS). This is the first experience with adult patients who were not on ECLS.

METHODS

Intratracheal perflubron in a total dose of 30.1 +/- 7.1 ml/kg was administered over a period of 45 +/- 9 hours to nine adult patients with mean age = 49 +/- 4 years and mean PaO2/FiO2 ratio = 128 +/- 7 as part of a prospective, multicenter, phase I-II noncontrolled trial.

RESULTS

Significant decreases in mean (A-a)DO2 (baseline = 430 +/- 47, 48 hour = 229 +/- 17, p = 0.0127 by ANOVA) and FiO2 (baseline = 0.82 +/- 0.08, 48 hour = 0.54 +/- 0.06, p = 0.025), along with an increase in mean SvO2 (baseline = 75 +/- 3, 48 hour = 85 +/- 2, p = 0.018 by ANOVA) were observed. No significant changes in pulmonary compliance or hemodynamic variables were noted. Seven of the nine patients in this study survived beyond 28 days after initiation of partial liquid ventilation whereas 5 patients survived to discharge. Three adverse events [hypoxia (2) and hyperbilirubinemia (1)] were determined to be severe in nature.

CONCLUSIONS

These data suggest that PLV may be performed safely with few related severe adverse effects. Improvement in gas exchange was observed in this series of adult patients over the 48 hours after initiation of PLV.

A prospective comparison of atrio-femoral and femoro-atrial flow in adult venovenous extracorporeal life support

INTRODUCTION

In the United States, venovenous extracorporeal life support has traditionally been performed with atrial drainage and femoral reinfusion (atrio-femoral flow). Although flow reversal (femoro-atrial flow) may alter recirculation and extracorporeal flow, no direct comparison of these 2 modes has been undertaken.

OBJECTIVE

Our goal was to prospectively compare atrio-femoral and femoro-atrial flow in adult venovenous extracorporeal life support for respiratory failure.

METHODS

A modified bridge enabling conversion between atrio-femoral and femoro-atrial flow was incorporated in the extracorporeal circuit. Bypass was initiated in the direction that provided the highest pulmonary arterial mixed venous oxygen saturation, and the following measurements were taken: (1) maximum extracorporeal flow, (2) highest achievable pulmonary arterial mixed venous oxygen saturation, and (3) flow required to maintain the same pulmonary arterial mixed venous oxygen saturation in both directions. Flow direction was then reversed, and the measurements were repeated. Data were compared with paired t tests and are presented as mean +/- standard deviation.

RESULTS

Ten patients were studied, and 9 were included in the data analysis. Femoro-atrial bypass provided (1) higher maximal extracorporeal flow (femoro-atrial flow = 55.6 +/- 9.8 mL/kg per minute, atrio-femoral flow = 51.1 +/- 11.1 mL/kg per minute; P = .04) and (2) higher pulmonary arterial mixed venous oxygen saturation (femoroatrial flow = 89.9% +/- 6.6%, atrio-femoral flow = 83.2% +/- 4.2%; P = .006); (3) furthermore, it required less flow to maintain an equivalent pulmonary arterial mixed venous oxygen saturation (femoro-atrial flow = 37.0 +/- 12.2 mL/kg per minute, atrio-femoral flow = 46.4 +/- 8.8 mL/kg per minute; P = .04).

CONCLUSIONS

During venovenous extracorporeal life support, femoro-atrial bypass provided higher maximal extracorporeal flow, higher pulmonary arterial mixed venous oxygen saturation, and required comparatively less flow to maintain an equivalent mixed venous oxygen saturation than did atrio-femoral bypass.

Neutrophil accumulation is reduced during partial liquid ventilation

OBJECTIVE

This study evaluates the ability of perflubron to inhibit pulmonary neutrophil accumulation during partial liquid ventilation (PLV) in the setting of acute lung injury.

DESIGN

Randomized, controlled, nonblinded study.

SETTING

Research laboratory at a university.

SUBJECTS

Male, Sprague-Dawley rats (n = 120, 506 +/- 42 g).

INTERVENTIONS

Animals were divided into eight groups (n = 15 in each group, of which n = 12 for myeloperoxidase content and n = 3 for histologic neutrophil counting): a) GV-CVF group, animals received gas ventilation (GV) with the induction of lung injury using cobra venom factor (CVF); b) PLV-CVF group, animals received partial liquid ventilation before the induction of lung injury; c) PEEP-CVF group, animals received positive end-expiratory pressure (PEEP) before the administration of cobra venom factor; d) CVF-PLV group, animals received partial liquid ventilation after cobra venom factor; e) CVF-PEEP group, animals received PEEP after cobra venom factor; f) PLV only group, animals received partial liquid ventilation only; g) GV only group, animals received gas ventilation only; and h) NVSBA group, nonventilated spontaneous breathing animals.

MEASUREMENTS AND MAIN RESULTS

After the experimental period, total lung myeloperoxidase content was significantly decreased in the PLV-CVF (0.29 +/- 0.08, p = .02) and PEEP-CVF (0.34 +/- 0.04, p = .01) groups when compared with the GV-CVF group (0.62 +/- 0.07). When compared with the GV-CVF group, a trend toward a reduction in myeloperoxidase was observed in the CVF-PLV (0.42 +/- 0.05, p = .07) and the CVF-PEEP (0.39 +/- 0.06, p = .07) groups. When compared with the cobra venom factor only group (GV-CVF 47 +/- 2 neutrophils/high-power field), reductions in neutrophil count were observed in all groups (neutrophils/high-power field): PLV-CVF (20 +/- 2, p = .009); PEEP-CVF (24 +/- 1, p = .01); CVF-PLV (30 +/- 2, p = .03); and CVF-PEEP (37 +/- 1, p = .04).

CONCLUSION

These data suggest that both partial liquid ventilation and PEEP result in a reduction in neutrophil accumulation in the setting of acute lung injury.

Use of extracorporeal life support for adult patients with respiratory failure and sepsis

Traditionally, adult sepsis has been considered a contraindication to extracorporeal life support (ECLS). The objective of this study was to review the authors' institutional experience with a subgroup of adult patients requiring ECLS for severe respiratory failure and sepsis. Hospital records from 100 consecutive adult patients with respiratory failure placed on ECLS between 1990 and 1996 were retrospectively reviewed. Patients with sepsis as a primary indication were identified, and blood culture data reviewed. Data were analyzed with t tests and chi-square and are presented as mean +/- standard deviation. Multiple logistic regression determined the impact of sepsis and positive blood cultures (PBCs) on survival. Fourteen patients required ECLS for sepsis; 36 had PBCs during hospitalization (15 before or during ECLS). Septic patients had lower pre-ECLS PaO2/FIO2 ratios (septic: 53 +/- 14 mmHg, nonseptic: 70 +/- 68 mmHg, p = 0.04). Patients with PBCs before or during ECLS were younger (PBC: 29 +/- 6 years, no PBC: 35 +/- 13 years, p = 0.003), remained on ECLS longer (PBC: 485 +/- 336 hours, no PBC: 232 +/- 212 hours, p = 0.01), and were more frequently cannulated within 12 hours (PBC: 15/15, no PBC 60/85 p = 0.02). Neither group differed in organ dysfunction (incidence or type), frequency of respiratory recovery, or survival. Neither sepsis nor positive blood cultures were independently predictive of mortality. Sepsis and positive blood cultures do not adversely affect outcome in adult patients with respiratory failure requiring ECLS.

An approach to the treatment of severe adult respiratory failure

OBJECTIVES

The purpose of this article is to evaluate outcome in adult patients with severe respiratory failure managed with an approach using (1) limitation of end inspiratory pressure, (2) inverse ratio ventilation, (3) titration of PEEP by SvO2, (4) intermittent prone positioning, (5) limitation of FiO2, (6) diuresis, (7) transfusion, and (8) extracorporeal life support (ECLS) if patients failed to respond.

PATIENTS AND METHODS

This study was designed as a retrospective review in the intensive care unit of a tertiary referral hospital. One-hundred forty-one consecutive patients with hypoxic (n = 135) or hypercarbic (n = 6) respiratory failure referred for consideration of ECLS between 1990 and 1996. Overall, initial PaO2/FiO2 (P/F) ratio was 75+/-5 (median = 66).

RESULTS

Lung recovery occurred in 67% of patients and 62% survived. Forty-one patients improved without ECLS (83% survived); 100 did not and were supported with ECLS (54% survived). Survival was greater in patients cannulated within 12 hours of arrival (59%) compared with those cannulated after 12 hours (40%, P < .05). Multiple logistic regression identified age, duration of mechanical ventilation before transfer, four or more dysfunctional organs, and the requirement for ECLS as independent predictors of mortality.

CONCLUSIONS

An approach that emphasizes lung protection and early implementation of extracorporeal life support is associated with high rates of survival in patients with severe respiratory failure.

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 life support for 100 adult patients with severe respiratory failure

OBJECTIVE

The authors retrospectively reviewed their experience with extracorporeal life support (ECLS) in 100 adult patients with severe respiratory failure (ARF) to define techniques, characterize its efficacy and utilization, and determine predictors of outcome.

SUMMARY BACKGROUND DATA

Extracorporeal life support maintains gas exchange during ARF, providing diseased lungs an optimal environment in which to heal. Extracorporeal life support has been successful in the treatment of respiratory failure in infants and children. In 1990, the authors instituted a standardized protocol for treatment of severe ARF in adults, which included ECLS when less invasive methods failed.

METHODS

From January 1990 to July 1996, the authors used ECLS for 100 adults with severe acute hypoxemic respiratory failure (n = 94): paO2/FiO2 ratio of 55.7+/-15.9, transpulmonary shunt (Qs/Qt) of 52+/-22%, or acute hypercarbic respiratory failure (n = 6): paCO2 84.0+/-31.5 mmHg, despite and after maximal conventional ventilation. The technique included venovenous percutaneous access, lung "rest," transport on ECLS, minimal anticoagulation, hemofiltration, and optimal systemic oxygen delivery.

RESULTS

Overall hospital survival was 54%. The duration of ECLS was 271.9+/-248.6 hours. Primary diagnoses included pneumonia (49 cases, 53% survived), adult respiratory distress syndrome (45 cases, 51 % survived), and airway support (6 cases, 83% survived). Multivariate logistic regression modeling identified the following pre-ECLS variables significant independent predictors of outcome: 1) pre-ECLS days of mechanical ventilation (p = 0.0003), 2) pre-ECLS paO2/FiO2 ratio (p = 0.002), and 3) age (years) (p = 0.005). Modeling of variables during ECLS showed that no mechanical complications were independent predictors of outcome, and the only patient-related complications associated with outcome were the presence of renal failure (p < 0.0001) and significant surgical site bleeding (p = 0.0005).

CONCLUSIONS

Extracorporeal life support provides life support for ARF in adults, allowing time for injured lungs to recover. In 100 patients selected for high mortality risk despite and after optimal conventional treatment, 54% survived. Extracorporeal life support is extraordinary but reasonable treatment in severe adult respiratory failure. Predictors of survival exist that may be useful for patient prognostication and design of future prospective studies.

Characteristics of an albumin dialysate hemodiafiltration system for the clearance of unconjugated bilirubin

Extraction of protein bound liver failure toxins, such as unconjugated bilirubin, short chain fatty acids, and aromatic amino acids has been reported using hemodiafiltration with albumin in the dialysate, but the characteristics of such a system have not been described. Therefore, bilirubin clearance using albumin dialysate hemodiafiltration was evaluated in the setting of different dialysate albumin concentrations, varying temperature and pH. An in vitro continuous hemodiafiltration circuit was used with single pass countercurrent dialysis. Unconjugated bilirubin was added to bovine blood and filtered across a polyalkyl sulfone (PAS) hemofilter using matched filtration and dialysate flow rates. The serial bilirubin content was measured and first order clearance kinetics verified. The clearance rate constants were calculated for three dialysate groups of different albumin concentration at constant temperature and pH (group 1: 10 g/dl albumin, n = 5; 2 g/dl albumin, n = 5; normal saline, n = 5), and three groups of different temperature and pH at constant albumin dialysate concentration (group 2: pH = 7.0, temperature = 20 degrees C, n = 5; pH = 7.5, temperature = 20 degrees C, n = 5; pH = 7.0, temperature = 40 degrees C, n = 5). Comparisons were made with ANOVA and Tukey post hoc analysis. When albumin was used in the dialysate, the 2 g/dl group cleared bilirubin 3.1 times faster than saline alone (p = 0.001), and the 10 g/dl group was superior to both (p = 0.001). There were no measurable differences between the 2 g/dl groups at the various temperatures tested (p = 0.08), but the clearance was less at a pH of 7.5 (p = 0.015). The clearance of unconjugated bilirubin is greatly enhanced with the use of albumin containing dialysates when compared to traditional crystalloid hemodiafiltration, is greater at lower pH, and seems to be unaffected by temperature.

Total respiratory support with tidal flow extracorporeal circulation in adult sheep

A novel pressure gated tidal flow extracorporeal circulation (TF ECC) device was developed, and it was hypothesized that it could provide total respiratory support in apneic adult sheep without adverse hemodynamic or cardiac effects. The circuit consisted of a single lumen cannula, computer driven tubing occluders gated by circuit pressure, a nonocclusive peristaltic blood pump, a spiral coiled membrane lung, and a heat exchanger. Six paralyzed, anesthetized adult sheep were instrumented and TF ECC was instituted via cannulation of the right atrium. Total respiratory support was provided by the circuit during an apneic period of 6 hours. Echocardiography was performed with the animal instrumented (baseline) and after 2 hours of TF ECC. Circuit blood tidal volume was 172.6 +/- 18.0 cc, resulting in a TF ECC flow of 71.1 +/- 10.1 cc/kg/min. At the end of the study period, PaCO2 was 35.5 +/- 7.6 mmHg, paO2) was 91.2 +/- 30.6 mmHg, and pulmonary artery oxygen saturation (SPAO2) was 95 +/- 5%. Hemodynamic stability was maintained with no significant differences at baseline and after 6 hours in mean arterial pressure, mean pulmonary artery pressure, or heart rate noted. Echocardiographic evaluation showed preserved fractional shortening of the left ventricular (LV) septal-lateral dimension (baseline 32.4 +/- 11.4%; 2 hours 34.8 +/- 8.4%). This study demonstrates TF ECC provides total respiratory support without adverse hemodynamic effects, and preserved LV function.

Effect of independent changes in mixed-venous PCO2 or PO2 on cardiac output in anesthetized sheep

To determine whether changes mixed-venous PCO2 or PO2 affect cardiac output independent of changes in arterial blood gases, we used extracorporeal gas exchange to increase mixed-venous PCO2 or decrease mixed-venous PO2 in adult sheep. Sheep were anesthetized, mechanically ventilated, and connected to a veno-venous extracorporeal circuit. The circuit included a gas exchanger which was used to increase mixed-venous PCO2 or decrease mixed-venous PO2; the native lungs were ventilated to maintain arterial PCO2 and PO2 at control levels. When mixed-venous PCO2 was increased by 32% above control levels for a period of 60 min, cardiac output increased significantly to 28% above control levels. Cervical vagotomy abolished this response. In contrast, decreasing mixed-venous PO2 by 29% did not increase cardiac output. These results demonstrate that increasing mixed-venous PCO2 can increase cardiac output independent of changes in arterial blood gases and that intact vagus nerves are necessary for this response to occur.

Extracorporeal life support for patients with significant orthopaedic trauma

Extracorporeal life support is a therapeutic modality that can provide cardiorespiratory support for multiply injured patients. Fourteen patients with multiple trauma who sustained pelvic or long bone fractures were referred for treatment with extracorporeal life support at the University of Michigan Medical Center. All patients were considered morlbund secondary to their pulmonary injury. Six of the 14 patients had bilateral pulmonary contusions. The mean Injury Severity Score was 19. Twelve of the 14 patients had femoral or pelvic fractures or both. Eight patients had orthopaedic injuries initially treated with traction. The most common complication during extracorporeal life support management was bleeding, which occurred in eight of 14 patients. Eight of the 14 patients survived. Seven of eight patients with less than 6 days of mechanical ventilation before initiation of extracorporeal life support survived. Only one of six patients with six or more days of mechanical ventilation before initiation of extracorporeal life support survived. Patients with significant orthopaedic trauma and severe pulmonary compromise have an extremely high mortality risk. Appropriate aggressive fracture management remains the most important intervention to decrease the risk of pulmonary compromise. Early initiation of extracorporeal life support can be an additional lifesaving intervention in select patients with orthopaedic trauma who have respiratory failure refractory to conventional mechanical ventilation.

Prolonged extracorporeal life support (ECLS) for varicella pneumonia

OBJECTIVE

To review the institutional experience of a national tertiary referral center for extracorporeal life support (ECLS) in severe varicella pneumonia.

DATA SOURCES

Hospital records and ECLS flow sheets.

STUDY SELECTION

All pediatric (nonneonatal) and adult patients who were treated for varicella pneumonia with ECLS at the University of Michigan Medical Center between 1986 and 1995.

DATA EXTRACTION

Diagnosis of varicella pneumonia was made by history of recent exposure to chickenpox, progressive dyspnea, fever, a characteristic diffuse, vesicular rash, and a supporting chest roentgenogram. Indications for ECLS included a shunt fraction of > 30% or PaO2/FlO2 ratio of < 80 despite maximal conventional therapy, which included aggressive diuresis, blood transfusions to optimize oxygen-carrying capacity, pressure-controlled/inverse-ratio ventilation, and intermittent prone positioning.

DATA SYNTHESIS

Between 1986 and 1995, 191 patients were referred for ECLS. Among these patients, there were 51 (27%) cases of viral pneumonia, of which nine cases were due to acute varicella-zoster infection. Intravenous acyclovir was administered to eight of the nine patients. Of the nine patients, two patients improved using conventional ventilator management, and seven patients underwent ECLS. Overall survival on ECLS was 71% (5/7). The mean (+/-SD) alveolar-arterial oxygen gradient and PaO2/FlO2 ratio were 533 +/- 101 torr (71.3 +/- 13.5 kPa) and 67 +/- 24, respectively. The median duration of mechanical ventilation before ECLS and the subsequent duration of ECLS were 4 and 12.8 days, respectively. One of the deaths was from progressive right heart failure secondary to pulmonary hypertension and the other death was from overwhelming Pseudomonas sepsis.

CONCLUSIONS

Early recognition of imminent pulmonary failure and rapid institution of ECLS are critical in the successful management of severe, life-threatening varicella pneumonia.