Extracorporeal membrane oxygenation in postcardiotomy patients: Factors influencing outcome

ObjectiveOur objective was to assess the morbidity and mortality in children requiring extracorporeal membrane oxygenator support after cardiac surgery and to determine factors influencing outcome.MethodsBetween January 2003 and June 2008, 58 patients required extracorporeal membrane oxygenator support after cardiac surgery. A retrospective study was performed and factors influencing outcome were determined by logistic regression modeling with the probability of outcome based on a combination of multivariate predictors.ResultsMedian age and weight were 12 days and 3.3 kg, respectively. Thirty-one patients had single ventricle repair and 27 had biventricular repair. Median duration of support with the oxygenator was 6 days. Thirty-nine (67%) patients were successfully weaned off the support, but only 24 (41%) survived to hospital discharge. Chief complications were renal failure (31%), neurologic complications (29%), and sepsis (16%). Multivariable logistic regression analysis identified 10 days or more of extracorporeal membrane oxygenation (odds ratio = 6.1), urine output less than 2 mL · kg−1 · h−1 in first 24 hours (odds ratio = 15), renal failure (odds ratio = 9.4), and pH less than 7.35 after 24 hours of extracorporeal membrane oxygenation (odds ratio = 82) as significant independent factors associated with failure to wean off extracorporeal membrane oxygenation. Factors associated with failure of hospital discharge despite successful decannulation were as follows: extracorporeal membrane oxygenator support time of 10 days or more, red blood cell transfusion of greater than 1000 mL/kg during the entire period of oxygenator support, and sepsis. Patients with single ventricle repair were at higher risk of hospital mortality.ConclusionLonger duration of extracorporeal membrane oxygenator support, low pH and urine output in the first 24 hours, and renal failure are significant factors associated with mortality during extracorporeal membrane oxygenator support. Exposure to high amounts of blood transfusion during extracorporeal oxygenation, extended extracorporeal membrane oxygenator support, and sepsis increase risk of death after successful decannulation

Interaction of temperature with hematocrit level and pH determines safe duration of hypothermic circulatory arrest

AbstractObjectivePrevious studies have demonstrated that both hematocrit level and pH influence the protection afforded by deep hypothermic circulatory arrest. The current study examines how temperature modulates the effect of hematocrit level and pH in determining a safe duration of circulatory arrest. The study also builds on previous work investigating the utility of near-infrared spectroscopy as a real-time monitor of cerebral protection during circulatory arrest.MethodsSeventy-six piglets (9.3 ± 1.2 kg) underwent circulatory arrest under varying conditions with continuous monitoring by means of near-infrared spectroscopy (hematocrit level of 20% or 30%; pH-stat or alpha-stat strategy; temperature of 15°C or 25°C; arrest time of 60, 80, or 100 minutes). Neurologic recovery was evaluated daily by a veterinarian, and the brain was fixed in situ on postoperative day 4 to be examined on the basis of histologic score in a blinded fashion.ResultsMultivariable analysis of total histologic score revealed that higher temperature, lower hematocrit level, more alkaline pH, and longer hypothermic circulatory arrest duration were predictive of more severe damage to the brain (P < .01). Regression modeling revealed that higher temperature exacerbated the disadvantage of a lower hematocrit level and longer arrest times but not pH strategy. Normalized oxyhemoglobin nadir time, derived from near-infrared spectroscopy, was positively correlated with neurologic recovery on the fourth postoperative day and with total histologic injury score (P < .0001).ConclusionHematocrit level and pH, as well as temperature, determine the safe duration of hypothermic circulatory arrest. Near-infrared spectroscopy is a useful real-time monitor of safe duration of circulatory arrest

Tissue oxygenation index is a useful monitor of histologic and neurologic outcome after cardiopulmonary bypass in piglets

ObjectiveTissue oxygenation index is a novel monitoring indicator derived by near-infrared spectroscopy. We hypothesized that tissue oxygenation index could predict a minimum safe flow rate for specific bypass conditions.MethodsThirty-six piglets (age, 43 ± 5 days; weight, 9.0 ± 1.1 kg) underwent cardiopulmonary bypass with cerebral near-infrared spectroscopy (NIRO-300; Hamamatsu Photonics K.K., Hamamatsu City, Japan). Animals were cooled for 40 minutes to 15°C, 25°C, or 34°C (pH-stat, hematocrit value of 20% or 30%, and pump flow of 100 mL·kg−1·min−1), followed by low-flow perfusion (10, 25, or 50 mL·kg−1·min−1) for 2 hours. Neurologic and behavioral evaluations were determined for 4 days. The brain was then fixed for histologic assessment. Tissue oxygenation index was defined as the average signal during low-flow bypass.ResultsAnimals with an average tissue oxygenation index of less than 55% showed cerebral injury, whereas animals with an index of greater than 55% showed minimal or no evidence of injury. Correlations were found between average tissue oxygenation index and histologic score (Spearman rho = −0.65, P < .001) and neurologic deficit score (Pearson r = −0.50, P = .002) on the first postoperative day. Temperature (P < .001), flow rate (P < .001), and hematocrit value (P = .002) were multivariable predictors of tissue oxygenation index, as determined by means of multivariable analysis of variance.ConclusionTissue oxygenation index is a useful monitor for defining the minimum safe flow rate during cardiopulmonary bypass. An index value of less than 55% is a strong predictor of neurologic injury

Do mature pulmonary lobes grow after transplantation into an immature recipient?

BACKGROUND The use of reduced-size adult lung transplants could help solve the profound pediatric donor lung shortage. However, adequate long-term function of the mature grafts requires growth in proportion to the recipient's development. METHODS Mature left lower lobes from adult mini-pigs (age: 7 months; mean body weight: 30 kg) were transplanted into 14-week-old piglets (mean body weight: 15 kg). By the end of the 14-week holding period, lungs of the recipients (n = 4) were harvested. After volumetric measurements, the lung morphology was studied using light microscopy, scanning, and transmission electron microscopy. Changes of alveolar airspace volume were determined using a computer aided image analysis system. Comparisons were made to age- and weight-matched controls. RESULTS Volumetric studies showed no significant differences (p = 0.49) between the specific volume (mL/kg body weight) of lobar grafts and left lower lobes of adult controls. Morphologic studies showed marked structural differences between the grafts and the right native lungs of the recipients, with increased average alveolar diameter of the grafts. On light microscopy and scanning electron microscopy, alveoli appeared dilated and rounded compared to the normal polygonal shape in the controls. The computer generated semi-quantitative data of relative alveolar airspace volume tended to be higher in transplanted lobes. CONCLUSIONS The mature pulmonary lobar grafts have filled the growing left hemithorax of the developing recipient. Emphysema-like alterations of the grafts were observed without evidence of alveolar growth in the mature lobar transplants. Thus, it can be questioned whether mature pulmonary grafts can guarantee sufficient long-term gas exchange in growing recipients