Partial liquid ventilation provides effective gas exchange in a large animal model

PURPOSE

The purpose of this study was to show the ability of partial liquid ventilation (PLV) to sustain gas exchange in normal large (50 to 70 kg) adult animals.

METHODS

Ten adult sheep (53.7 +/- 2.8 kg) were anesthetized and mechanically ventilated. Sequential dosing of perflubron (LiquiVent, Alliance Pharmaceutical Corp, San Diego, CA) was performed to cumulative doses of 10 mL/kg, 20 mL/kg, 40 mL/kg, and 60 mL/kg. Physiological data were assessed at baseline and after each dose. Five animals were rotated through the left decubitus, right decubitus, supine, and prone positions while five animals remained prone throughout the experiment.

RESULTS

PaO2 and PaCO2 did not change significantly from baseline during administration of perflubron except for the PaO2 in rotated animals when supine (rotated-supine PaO2: baseline = 519 +/- 64 mm Hg; 60 mL/kg = 380 +/- 109 mm Hg, P = .0131). In both groups, static lung compliance (CT) decreased steadily with each successive perflubron instillation (nonrotated CT: baseline = 1.55 +/- 0.22 mL/cm H2O/kg; 60 mL/kg = 0.52 +/- 0.10 ml/cmH2O/kg, P = .0003).

CONCLUSIONS

These data show that during PLV in this normal animal model, effective gas exchange is sustained and CT decreases with increasing perflubron dose.

Pneumomediastinum: elucidation of the anatomic pathway by liquid ventilation

Partial liquid ventilation is a new technique to improve oxygenation in patients with severe acute respiratory distress syndrome. In a patient with status asthmaticus and tension pneumothorax treated with subsequent liquid ventilation, radiopaque perfluorocarbon was identified along brochiovascular structures, in the mediastinum, and in the retroperitoneum. Perfluorocarbon outlined on CT and chest radiography the anatomic pathway by which spontaneous pneumomediastinum develops following alveolar rupture, as described earlier by histopathologic study in animals. This represents the radiopaque equivalent of radiolucent pneumomediastinum. Perfluorocarbon remained in the pulmonary interstitium on radiography 30 days after beginning liquid ventilation, without sequelae.

Initial experience with partial liquid ventilation in adult patients with the acute respiratory distress syndrome

OBJECTIVE

To evaluate the safety and efficacy of partial liquid ventilation (PLV).

DESIGN

Before-after trial.

SETTING

The surgical intensive care unit at the University of Michigan, Ann Arbor, from April to December 1994.

PATIENTS

A consecutive sample of 10 patients aged 19 to 55 years with the acute respiratory distress syndrome who were receiving extracorporeal life support.

INTERVENTION

Perflubron was administered into the trachea until the dependent zone of the lung was filled. Gas ventilation of the perflubron-filled lung was then performed (PLV). Volatilized perflubron replacement was repeated daily for from 1 to 7 days with a median cumulative dose of 38 mL/kg (range, 15 to 62 mL/kg).

MAIN OUTCOME MEASURES

Physiologic shunt and static pulmonary compliance.

RESULTS

Physiologic shunt decreased from a median of 0.72 (range, 0.37 to 1.0) to 0.46 (range, 0.21 to 0.96) over the 72 hours following initiation of PLV (P = .01 by repeated measures analysis of variance). Static pulmonary compliance corrected for patient weight increased from a median of 0.16 mL/cm H2O per kilogram (range, 0.01 to 0.48 mL/cm H2O per kilogram) to 0.27 mL/cm H2O per kilogram (range, 0.05 to 1.11 mL/cm H2O per kilogram) over the same time period (P = .04 by repeated measures analysis of variance). Overall survival was five (50%) of 10 patients. Complications that were potentially associated with PLV included pneumothorax development in one patient and mucus plug formation in one patient.

CONCLUSIONS

Perflubron may be safely administered into the lungs of patients with severe respiratory failure receiving extracorporeal life support and may be associated with improvement in gas exchange and pulmonary compliance.

Total liquid ventilation with perfluorocarbons increases pulmonary end-expiratory volume and compliance in the setting of lung atelectasis

OBJECTIVE

To compare compliance and end-expiratory lung volume during reexpansion of normal and surfactant-deficient ex vivo atelectatic lungs with either gas or total liquid ventilation.

DESIGN

Controlled, animal study using an ex vivo lung preparation.

SETTING

A research laboratory at a university medical center.

SUBJECTS

Thirty-six adult cats, weighing 2.5 to 4.0 kg.

INTERVENTIONS

Heparin (300 U/kg) was administered, cats were killed, and lungs were excised en bloc. Normal lungs and saline-lavaged, surfactant-deficient lungs were allowed to passively collapse and remain atelectatic for 1 hr. Lungs then were placed in a plethysmograph and ventilated for 2 hrs with standardized volumes of either room air or perfluorocarbon. Static pulmonary compliance and end-expiratory lung volume were measured every 30 mins.

MEASUREMENTS AND MAIN RESULTS

Reexpansion of normal atelectatic lungs with total liquid ventilation was associated with an 11-fold increase in end-expiratory lung volume when compared with the increase in end-expiratory lung volume observed with gas ventilation (total liquid ventilation 50 +/- 14 mL, gas ventilation 4 +/- 9 mL, p < .0001). The difference was even more pronounced in the surfactant-deficient lungs with an approximately 19-fold increase in end-expiratory lung volume observed in the total liquid ventilated group, compared with the gas ventilated group (total liquid ventilation 44 +/- 17 mL, gas ventilation 2 +/- 8 mL, p = .0001). Total liquid ventilation was associated with an increase in pulmonary compliance when compared with gas ventilation in both normal and surfactant-deficient lungs (normal: gas ventilation 6 +/- 1 mL/cm H2O, total liquid ventilation 14 +/- 4 mL/cm H2O, p < .0001; surfactant-deficient: gas ventilation 4 +/- 1 mL/cm H2O, total liquid ventilation 9 +/- 3 mL/cm H2O, p < .01).

CONCLUSIONS

End-expiratory lung volume and static compliance are increased significantly following attempted reexpansion with total liquid ventilation when compared with gas ventilation in normal and surfactant-deficient, atelectatic lungs. The ability of total liquid ventilation to enhance recruitment of atelectatic lung regions may be an important means by which gas exchange is improved during total liquid ventilation when compared with gas ventilation in the setting of respiratory failure.

Partial liquid ventilation with perflubron during extracorporeal life support in adults: radiographic appearance

PURPOSE

To describe the radiographic appearance of perflubron-filled lungs during partial liquid ventilation (PLV).

MATERIALS AND METHODS

Supine chest radiographs (391 anteroposterior, 154 lateral radiographs) were obtained before and after daily perflubron instillation in 13 adults undergoing PLV who were receiving extracorporeal life support. Perflubron distribution, barotrauma, and inability to discern catheters were evaluated.

RESULTS

Immediately after instillation of perflubron, opacification of more than two-thirds of the lungs was shown in 12 of 13 patients. A gravity-dependent distribution of perflubron was shown on 146 (95%) of 154 lateral radiographs. Perflubron gradually cleared until it filled less than one-third of the lungs 6.8 days later (range, 2-20 days). In the five survivors, minimal perflubron was visible up to 138 days. In five patients, perflubron increased the visibility of small pneumothoraces present before PLV. Location of intrathoracic catheters was obscured on 44 radiographs.

CONCLUSION

Perflubron symmetrically opacifies the lungs in a gravity-dependent distribution during PLV and clears to minimal levels within 3 weeks.

Initial experience with partial liquid ventilation in pediatric patients with the acute respiratory distress syndrome

OBJECTIVE

Liquid ventilation with perfluorocarbon previously has not been reported in pediatric patients with respiratory failure beyond the neonatal period. We evaluated the technique of partial liquid ventilation in six pediatric patients with the acute respiratory distress syndrome of sufficient severity to require extracorporeal life support (ECLS).

DESIGN

This study was a noncontrolled, phase I/II experimental study with a single group pretest/posttest design.

SETTING

All studies were performed at a tertiary, pediatric referral hospital at the University of Michigan Medical School.

PATIENTS

Six pediatric patients, from 8 wks to 5 1/2 yrs of age, with severe respiratory failure requiring ECLS to support gas exchange.

INTERVENTIONS

After 2 to 9 days on ECLS, perfluorocarbon was administered into the trachea until the dependent zone of each lung was filled. The initial administered was 12.9 +/- 2.3 mL/kg (range 5 to 20). Gas ventilation of the perfluorocarbon-filled lungs (partial liquid ventilation) was then performed. The perfluorocarbon dose was repeated daily for a total of 3 to 7 days, with a cumulative dose of 45.2 +/- 6.1 mL/kg (range 30 to 72.5).

MEASUREMENTS AND MAIN RESULTS

All measurements of native gas exchange were made during brief periods of discontinuation of ECLS and include PaO2 and the alveolar-arterial oxygen gradient, P(A-a)O2. Static pulmonary compliance, corrected for weight, was also measured directly. The mean PaO2 increased from 39 +/- 6 to 92 +/- 29 torr (5.2 +/- 0.8 to 12.2 +/- 3.9 kPa) over the 96 hrs after the initial dose (p = .021 by repeated-measures analysis of variance). The average P(A-a)O2 decreased from 635 +/- 10 to 499 +/- 77 torr (84.7 +/- 1.3 to 66.5 +/- 10.3 kPa) over the same time period (p = .059), while the mean static pulmonary compliance (normalized for patient weight) increased from 0.12 +/- 0.02 to 0.28 +/- 0.08 mL/cm H2O/kg (p = .01). All six patients survived. Complications potentially associated with partial liquid ventilation were limited to pneumothoraces in two of six patients.

CONCLUSIONS

Perfluorocarbon may be safely administered into the lungs of pediatric patients with severe respiratory failure on ECLS and may be associated with improvement in gas exchange and pulmonary compliance.

Liquid ventilation in adults, children, and full-term neonates

We evaluated the safety and efficacy of partial liquid ventilation in a series of 19 adults, children, and neonates who were in respiratory failure and on extracorporeal life support. During partial liquid ventilation, the alveolar-arterial oxygen difference decreased from 590 (SE 25) to 471 (42) mm Hg (p = 0.0002) and static pulmonary compliance increased from 0.18 (0.04) to 0.29 (0.04) mL cm H2O-1 kg-1 (p = 0.0002). 11 patients (58%) survived. These preliminary data suggest that partial liquid ventilation can be safely used in patients with severe respiratory failure and may improve lung function.

Improvement of gas exchange, pulmonary function, and lung injury with partial liquid ventilation. A study model in a setting of severe respiratory failure

STUDY OBJECTIVE

To evaluate gas exchange, pulmonary function, and lung histology during gas ventilation of the perfluorocarbon-filled lung compared with gas ventilation of the gas-filled lung in severe respiratory failure.

STUDY DESIGN

Application of gas (GV) or partial liquid (PLV) ventilation in lung-injured sheep.

SETTING

A research laboratory at a university medical center.

SUBJECTS

Eleven sheep 17.1 +/- 1.8 kg in weight.

INTERVENTIONS

Lung injury was induced by intravenous administration of 0.07 mL/kg oleic acid followed by saline pulmonary lavage. When alveolar-arterial oxygen pressure difference (P[A-a]O2) was 600 mm Hg or more and PaO2 was 50 mm Hg or less with fraction of inspired oxygen of 1.0, bijugular venovenous extracorporeal life support (ECLS) was instituted. For the first 30 min on ECLS, all animals were ventilated with gas. Over the ensuing 2.5 h, ventilation with 15 mL/kg gas was continued without intervention in the control group (GV, n = 6) or with the addition of 35 mL/kg of perflubron (PLV, n = 5).

MEASUREMENTS AND RESULTS

At 3 h after initiation of ECLS, Qps/Qt was significantly reduced in the PLV animals when compared with the GV animals (PLV = 41 +/- 13%; GV = 93 +/- 4%; p < 0.005). At the same time point, pulmonary compliance was increased in the PLV when compared with the GV group (PLV = 0.61 +/- 0.14 mL/cm H2O/kg; GV = 0.41 +/- 0.02 mL/cm H2O/kg; p < 0.005). The ECLS flow rate required to maintain the PaO2 in the 50 to 80 mm Hg range was substantially and significantly lower in the PLV group when compared with that of the GV group (PLV = 25 +/- 20 mL/kg/min; GV = 87 +/- 15 mL/kg/min; p < 0.001). Light microscopy performed on lung biopsy specimens demonstrated a marked reduction in lung injury in the liquid ventilated (LV) when compared with the GV animals.

CONCLUSION

In a model of severe respiratory failure, PLV improves pulmonary gas exchange and pulmonary function and is associated with a reduction in pulmonary pathology.

A matched pairs analysis of venoarterial and venovenous extracorporeal life support in neonatal respiratory failure

It has been suggested that venovenous (VV) extracorporeal life support (ECLS) confers a survival advantage over venoarterial (VA) ECLS. These results have been confounded by differences in patient populations. In this study, a matched pairs comparison of survival and complication rates in neonatal respiratory failure patients managed with VA or VV ECLS was performed. Retrospective matching of 643 VA and VV patient pairs from the Extracorporeal Life Support Organization Registry was performed. Pairs were matched by same year, same diagnosis, gestational age +/- 1 week, birth weight +/- 0.3 kg, and oxygenation index +/- 5. Further matching for hemodynamic status was possible for 272 pairs and included pre ECLS CPR, use of epinephrine, and arterial pH +/- 0.1. Statistical significance was defined for outcome and selected complication rates using McNemar's chi-square analysis with correction for multiple comparisons. A survival advantage for VV was significant when matching for respiratory failure (83.8% VA versus 91.5% VV), but was not significant when matching for hemodynamic failure (90.4% VA versus 94.5% VV). In the latter match, hemolysis (10.7% VA versus 23.5% VV) and cannula kinking (0.4% VA versus 10.6% VV) were more common with VV ECLS. The incidence of intracranial hemorrhage did not significantly differ between groups (6.3% VA versus 7.4% VV). Survival is not significantly greater with VV ECLS when patients are matched for degree of respiratory and hemodynamic failure. Hemolysis and cannula kinking are more common with VV ECLS. There is no identified difference in the incidence of intracranial hemorrhage.

Approach to cervicothoracic neuroblastomas via a trap-door incision

Neuroblastomas located in the apex of the hemithorax or in the lower cervical region may make complete resection via a cervical or a thoracic approach difficult. The authors recently managed two patients with cervicothoracic neuroblastomas through an approach using the trap-door incision often applied in the setting of vascular trauma. This approach allowed a successful, complete excision of these tumors, which may have otherwise been difficult.

Liquid ventilation improves pulmonary function, gas exchange, and lung injury in a model of respiratory failure

OBJECTIVE

The authors evaluated gas exchange, pulmonary function, and lung histology during perfluorocarbon liquid ventilation (LV) when compared with gas ventilation (GV) in the setting of severe respiratory failure.

BACKGROUND

The efficacy of LV in the setting of respiratory failure has been evaluated in premature animals with surfactant deficiency. However, very little work has been performed in evaluating the efficacy of LV in older animal models of the adult respiratory distress syndrome (ARDS).

METHODS

A stable model of lung injury was induced in 12 young sheep weighing 16.4 +/- 3.0 kg using right atrial injection of 0.07 mL/kg of oleic acid followed by saline pulmonary lavage and bijugular venovenous extracorporeal life support (ECLS). For the first 30 minutes on ECLS, all animals were ventilated with gas. Animals were then ventilated with either 15 mL/kg gas (GV, n = 6) or perflubron ([PFC], LV, n = 6) over the ensuing 2.5 hours. Subsequently, ECLS was discontinued in five of the GV animals and five of the LV animals, and GV or LV continued for 1 hour or until death.

MAIN FINDINGS

Physiologic shunt (Qps/Qt) was significantly reduced in the LV animals when compared with the GV animals (LV = 31 +/- 10%; GV = 93 +/- 4%; p < 0.001) after 3 hours of ECLS. At the same time point, pulmonary compliance (CT) was significantly increased in the LV group when compared with the GV group (LV = 1.04 +/- 0.19 mL/cm H2O/kg; GV = 0.41 +/- 0.02 mL/cm H2O/kg; p < 0.001). In addition, the ECLS flow rate required to maintain the PaO2 in the 50- to 80-mm Hg range was substantially and significantly lower in the LV group when compared with that of the GV group (LV = 14 +/- 5 mL/kg/min; GV = 87 +/- 15 mL/kg/min; p < 0.001). All of the GV animals died after discontinuation of ECLS, whereas all the LV animals demonstrated effective gas exchange without extracorporeal support for 1 hour (p < 0.01). Lung biopsy light microscopy demonstrated a marked reduction in alveolar hemorrhage, lung fluid accumulation, and inflammatory infiltration in the LV group when compared with the GV animals.

CONCLUSION

In a model of severe respiratory failure, LV improves pulmonary gas exchange and compliance with an associated reduction in alveolar hemorrhage, edema, and inflammatory infiltrate.

Enterocolitis associated with Hirschsprung's disease: a clinical-radiological characterization based on 168 patients

The enterocolitis associated with Hirschsprung's disease (HD) has not been clearly characterized. This study was undertaken to analyze the clinical and radiological findings of Hirschsprung's enterocolitis (HEC) in 168 patients treated from July 1974 through October 1992. HEC occurred in 57 patients (33.9%), either preoperatively (13; 7.7%) or postoperatively (36; 21.4%). In eight patients (4.8%), it occurred pre- and postoperatively. The number of bouts of HEC per patient ranged from one to six (mean, 2.2). The major presenting features were abdominal distension (83%), explosive diarrhea (69%), vomiting (51%), fever (34%), lethargy (27%), rectal bleeding (5%), and colonic perforation (2.5%). There were no deaths directly related to HEC. The analysis of 150 plain x-rays of the abdomen, taken at the onset of HEC or in between bouts, showed that colonic dilatation was the most sensitive radiological finding (90% sensitivity), but it had poor specificity (24%). However, an intestinal cutoff sign (gaseous intestinal distension with abrupt cutoff at the level of the pelvic brim) was both sensitive (74%) and specific (86%) for HEC. Barium enema was of limited value in the diagnosis of HEC bouts because most of the radiographic findings persisted for prolonged periods after cessation of such bouts. The authors conclude that (1) HEC can be characterized as abdominal distension and explosive diarrhea associated with the intestinal cutoff sign and (2) the occurrence of explosive diarrhea in any patient with HD is suggestive of HEC, even in the absence of systemic symptoms, and should be treated to avoid the morbidity and potential mortality of HEC.

Outcome for infants with congenital diaphragmatic hernia requiring extracorporeal membrane oxygenation: the first year

Congenital diaphragmatic hernia (CDH) has been associated with a high mortality rate. The purposes of this study were to determine the impact of extracorporeal membrane oxygenation (ECMO) on the survival of infants with CDH and to document the sequelae and 1-year neurodevelopmental outcome for CDH infants who required ECMO. Thirty neonates with CDH were admitted between May 7, 1990 and October 1, 1992. Twenty required ECMO and were enrolled in our neonatal follow-up program. Information about the infants' neonatal course was obtained from chart review, and the infants were seen at 3, 6, and 12 months of age for medical and neurodevelopmental follow-up. Primary diaphragmatic repair was performed in 13 infants. Five required Goretex graft reconstruction (GGR), and two did not have repair. Sixteen (80%) of the 20 infants who required ECMO survived. The overall survival rate increased from 31% (10 of 32) in the 5 years previous to the start of the ECMO program to 63% (19 of 30) since then (P = .01). The most common sequelae noted by the time of discharge included gastroesophageal reflux (GER; 81%), the need for tube feeding (69%), and chronic lung disease (CLD; 62%). At 1 year of age, mean cognitive skills were average (87 +/- 23) and motor skills were borderline (75 +/- 24) according to the Bayley Scales of Infant Development. Hypotonia was present in 10 of 13 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Development and application of a simplified liquid ventilator

OBJECTIVE

Perfluorocarbon liquid ventilation has been shown to have advantages over conventional gas ventilation in premature newborn and lung-injured animals. To simplify the process of liquid ventilation, we adapted an extra-corporeal life-support circuit as a time-cycled, volume-limited liquid ventilator.

DESIGN

Laboratory study that involved sequential application of gas and liquid ventilation in normal cats and in lung-injured sheep.

SETTING

A research laboratory at a university medical center.

SUBJECTS

Eight normal cats weighing 2.7 to 3.8 kg (mean 3.1 +/- 0.5), and four lung-injured young sheep weighing 10.4 to 22.5 kg (mean 15.9 +/- 5.0).

INTERVENTIONS

Normal cats were supported with traditional gas ventilation for 1 hr (respiratory rate 20 breaths/min, peak inspiratory pressure 12 cm H2O, positive end-expiratory pressure 4 cm H2O, and FIO2 1.0). The lungs were then filled with perfluorocarbon (30 mL/kg) and tidal volume liquid ventilation was instituted, utilizing a newly developed liquid ventilation device. Liquid ventilatory settings were 4 secs for inspiration time, 8 secs for expiration time, 5 breaths/min for respiratory rate, and 15 to 20 mL/kg for tidal volume. Liquid ventilation utilizing this device was also applied to sheep after induction of severe lung injury by right atrial injection of 0.07 mL/kg of oleic acid, followed by saline pulmonary lavage. Extracorporeal life support was instituted to provide a stable model of lung injury. For the first 30 mins of extracorporeal support, all animals were ventilated with gas. Animals were then ventilated with 15 mL/kg of perfluorocarbon over the ensuing 2.5 hrs.

MEASUREMENTS AND MAIN RESULTS

In normal cats, mean PaO2 values after 1 hr of liquid or gas ventilation were 275 +/- 90 (SD) torr (36.7 +/- 10.4 kPa) in the liquid-ventilated animals and 332 +/- 78 torr (44.3 +/- 10.4 kPa) in the gas-ventilated animals (NS). Mean PaCO2 values were 40.5 +/- 5.7 torr (5.39 +/- 0.31 kPa) in the liquid-ventilated animals and 37.6 +/- 2.3 torr (5.01 +/- 0.31 kPa) in the gas-ventilated animals (NS). Mean arterial pH values were 7.35 +/- 0.07 in the liquid-ventilated animals and 7.34 +/- 0.04 in the gas-ventilated animals (NS). No significant changes in heart rate, mean arterial pressure, lung compliance, or right atrial venous oxygen saturation were observed during liquid ventilation when compared with gas ventilation. In the lung-injured sheep, an increase in physiologic shunt from 15 +/- 7% to 66 +/- 9% was observed with induction of lung injury during gas ventilation. Liquid ventilation resulted in a significant reduction in physiologic shunt to 31 +/- 10% (p < .001). In addition, the extracorporeal blood flow rate required to maintain the PaO2 in the 50 to 80 torr (6.7 to 10.7 kPa) range was substantially and significantly (p < .001) lower during liquid ventilation than during gas ventilation (liquid ventilation 15 +/- 5 vs. gas ventilation 87 +/- 15 mL/min/kg).

CONCLUSIONS

Liquid ventilation can be performed successfully utilizing this simple adaptation of an extracorporeal life-support circuit. This modification to an existing extracorporeal circuit may allow other centers to apply this new investigational method of ventilation in the laboratory or clinical setting.

Colonization of intestinal bacteria in the normal neonate: comparison between mouth and rectal swabs and small and large bowel specimens

Seventy-four New Zealand white rabbit pups were divided into four groups: group I, 2 days of age (n = 9); group II, 3 to 5 days of age (n = 24); group III, 6 to 8 days of age (n = 27); and group IV, 10 to 13 days of age (n = 14). Mouth swabs (MS), rectal swabs (RS), small bowel specimens (SB), and large bowel specimens (LB) were obtained from each rabbit, incubated for 24 hours in thioglycolate broth, and plated on blood agar in aerobic and anaerobic environments. After 24 hours, growth on blood agar plates were observed. All MS specimens and all but one RS specimen showed positive growth. Growth of both LB and SB specimens increased significantly with age (P < .04). In addition, SB growth was significantly less than RS or MS growth in groups I, II, and III (P < .05). LB growth was significantly less than RS or MS growth in group I (P < .01) and tended to be less in groups II and III (62.5% v 100% and 93% v 100%, respectively). These data show that nearly half of normal rabbits under 6 days of age have sterile small and large intestines despite almost 100% growth from rectal and mouth swabs. These findings partially explain the absence of spontaneous bacterial translocation in young rabbit pups (under 4 days of age) and have important implications for the prophylaxis and treatment of neonatal sepsis.

Resolution of splenic injury after nonoperative management

Numerous studies have demonstrated success with nonoperative management of splenic injuries in pediatric patients. However, the resolution of the splenic injury has not been previously evaluated. The records of 50 pediatric patients with splenic injuries from blunt trauma treated nonoperatively between 1984 to 1992 were reviewed retrospectively. Abdominal computed tomography (CT) was performed at the time of injury and 6 weeks postinjury in 25 patients. These scans were reviewed and categorized by a modification of a previously reported grading system for parenchymal injury. All patients had healing of the splenic injuries, with complete resolution of the healing process observed at 6 weeks postinjury in 44%. Even those with shattered spleens (n = 6) had consistent improvement in splenic architecture, with resolution of fractures and/or contusions and return of splenic perfusion. Ten (77%) of 13 grade 1 and 2 injuries were completely resolved by the 6-week follow-up examination, whereas only one (8%) of 12 grade 3 to 5 injuries showed radiological resolution of splenic injuries. None of the 25 follow-up CT scans affected clinical decision-making or led to a deviation from the established protocol, which included a 3-month period of reduced activity. All 50 patients did well, without evidence of morbidity, mortality, or complications after return to full activity 3 months postinjury.(ABSTRACT TRUNCATED AT 250 WORDS)

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

OBJECTIVE

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

SUMMARY BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Evaluation of left ventricular mass in children with left-sided congenital diaphragmatic hernia

To evaluate left ventricular (LV) mass in children with left-sided congenital diaphragmatic hernia (CDH), we retrospectively examined the echocardiographic data available on all newborn infants with a diagnosis of CDH between April 1989 and May 1993. Adequate data for evaluation were available for 20 of 31 patients with left-sided CDH and no significant congenital heart disease. Left ventricular mass was determined from two-dimensional echocardiograms by an area-length method. Findings were compared with a control group that consisted of neonates with other causes of pulmonary hypertension. Patients with left-sided CDH had a significantly lower indexed LV mass than control subjects (1.96 gm/kg +/- 0.59 vs 2.84 gm/kg +/- 0.41; p = 0.0001). Additionally, children with left-sided CDH who required extracorporeal membrane oxygenation before repair (n = 7) had a significantly lower indexed LV mass than those patients who did not require extracorporeal membrane oxygenation before repair (1.53 gm/kg +/- 0.50 vs 2.20 gm/kg +/- 0.52; (p = 0.007). Infants who survived (n = 13) had an indexed LV mass of 2.09 gm/kg +/- 0.58 vs 1.64 gm/kg +/- 0.58 in those who died (p = 0.07). We conclude that the LV mass index in children with left-sided CDH is significantly lower than in children with other causes of pulmonary hypertension in the newborn period. Evaluation of LV mass in neonates with left-sided CDH may help predict the need for extracorporeal support before surgical repair, and may help indicate overall prognosis.

Effect of extracorporeal life support on survival when applied to all patients with congenital diaphragmatic hernia

Extracorporeal life support (ECLS) has been used for neonates with congenital diaphragmatic hernia (CDH) and respiratory failure at the authors' hospital since June 1981. In 1988, criteria for inclusion in ECLS were broadened to include "nonhoneymoon" infants (honeymoon: best postductal PaO2 of > 50 mm Hg). To evaluate the impact of this approach on the treatment of CDH, the authors reviewed the records of all newborns managed at their institution, since the availability of ECLS in 1981, who were symptomatic with CDH in the first 24 hours of life (n = 111). The patients were divided chronologically into two groups: 1981 to 1987 (early ECLS, n = 36) and 1988 to 1993 (expanded ECLS, n = 75). The data demonstrate that the number of CDH patients managed at our institution each year has increased (1981 to 1987 = 6, 1988 to 1993 = 14) as has the severity of associated respiratory insufficiency (% of patients with best PaO2 of < or = 50 mm Hg: 1981 to 1987 = 6%, 1988 to 1993 = 28%). Overall, the survival rate was lower for patients in the expanded ECLS group (59% v 75%; P = .121). When the survival rates for patients supported with ECLS postoperatively were compared for the expanded and early groups, a significant difference (59% v 80%; P < .05) was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Liquid ventilation provides uniform distribution of perfluorocarbon in the setting of respiratory failure

BACKGROUND

We evaluated the effect of perfluorocarbon liquid ventilation (LV) on gas exchange and pulmonary function in the setting of respiratory failure and the distribution of the ventilating medium during LV when compared to gas ventilation (GV).

METHODS

Ten sheep, 17.3 +/- 4.2 kg in weight, underwent oleic acid induction of lung injury followed by either GV (n = 5) or perfluorocarbon LV (n = 5). After 1 hour animals were killed, and chest computed tomographic (CT) imaging was performed. Average CT attenuation number was assessed as an indicator of the distribution of gas or perfluorocarbon in the dependent (posterior) and nondependent (anterior) zones of the lung (air = -1000; soft tissue = 0; perfluorocarbon = +2300 Hounsfield units [H]).

RESULTS

Significant increases in PaO2 (LV = 298 +/- 76 mm Hg, GV = 43 +/- 18 mm Hg, p < 0.001), SvO2 (LV = 74% +/- 6%, GV = 32% +/- 18%, p < 0.01), and lung compliance (LV = 1.65 +/- 0.50 ml/cm H2O/kg, GV = 0.58 +/- 0.06 ml/cm H2O/kg, p < 0.01) were observed. Significant decreases in physiologic shunt (LV = 24% +/- 6%, GV = 62% +/- 14%, p < 0.01) were noted. CT attenuation data showed the presence of minimal gas ventilation in the dependent regions during GV although the nondependent regions remained well aerated (CT attention number during GV: ND = -654 +/- 160 H; D = -92 +/- 160 H, p < 0.0001). During LV, there was a fairly homogenous distribution of perfluorocarbon in the lungs (CT attenuation number during LV: D = 1071 +/- 330 Hounsfield units; ND = 1112 +/- 287 Hounsfield units; p = 0.240). Lung biopsy analysis in the LV animals was consistent with a reduction in intraalveolar hemorrhage, intraalveolar edema, and the inflammatory infiltrate.

CONCLUSIONS

On the basis of the data, we conclude that in this lung injury model, (1) the distribution of the ventilating medium is uniform during LV when compared to GV, (2) LV improves gas exchange and pulmonary function, and (3) histologic evidence of lung injury is reduced after LV when compared to GV.

The development of an implantable artificial lung

This report describes the development of an implantable gas exchange device. The device is composed of hollow fiber elements wound around a central open core enclosed in a compliant outer casing, offering very low resistance to blood while providing adequate gas exchange. The purpose of this study was to determine if this device design can completely support the gas exchange requirements of a large animal when the device is placed in series with the main pulmonary artery (PA). Six 40-80 kg adult sheep were used. The device was placed with vascular grafts anastomosed end to side on the proximal and distal main PA. The study began with the entire right ventricular blood flow being diverted through the device by occlusion of a snare around the PA between the vascular grafts. Total gas exchange then was provided by the device and the endotracheal tube was clamped. Results showed that this pumpless potentially implantable device is capable of completely supporting the gas exchange requirements of the experimental animals for up to 8 hours in the acute setting without significant change in cardiac index (CI) and oxygen consumption (VO2) compared with baseline. CI = 55.0 +/- 17.0 cc/min/kg versus 45.0 +/- 17.3 cc/min/kg. VO2 = 1.90 +/- 0.96 cc O2/min/kg versus 2.08 +/- 0.54 cc O2/min/kg.

Prevention of radiation enteritis in children, using a pelvic mesh sling

Between 1986 and 1991, the authors used polyglycolic acid mesh slings (placed at or above the sacral promontory) in eight children with pelvic malignancies to exclude all small bowel from the pelvis during pelvic radiation therapy. The only complications of this treatment were prolonged postoperative ileus (one patient) and temporary, partial small bowel obstruction (one patient). The average amount of radiation administered to the pelvis postoperatively was 5,349 +/- 556 cGy. In one of the eight patients, gastrointestinal symptoms (diarrhea for 24 hours) developed during radiation therapy. Early radiological evaluation confirmed that the small bowel was out of the pelvis in all five of the patients studied. Mesh disruption occurred between 2 and 5 months postoperatively (mean, 3.4 +/- 1.5 months) and was often identified symptomatically by the patient. Seven of the eight survived, with disease remission in six. Pelvic disease was absent at the time of death in the one patient who did not survive. Throughout the follow-up period (mean, 20 months) no survivor has had delayed symptoms of radiation enteritis. In children with pelvic malignancies in whom aggressive application of pelvic irradiation is required, the use of an absorbable pelvic mesh sling appears efficacious in preventing radiation-associated enteritis.

Efficacy of extracorporeal life support in the setting of adult cardiorespiratory failure

The efficacy of extracorporeal life support (ECLS, ECMO) in the management of severe adult cardiorespiratory failure remains controversial. The purpose of this review is to evaluate the authors' institutional experience with ECLS in adult patients. Between 1988 and 1993, 65 moribund patients with respiratory (n = 51) and cardiac (n = 14) failure were supported with ECLS. Criteria for initiation of ECLS were: 90% chance of mortality despite maximal conventional respiratory management, good potential for recovery, and age younger than 60 years. Venovenous bypass was used in 40 and venoarterial in 25 patients. Respiratory management included low rate, low pressure ventilation with an inspired oxygen fraction < or = 0.5 and tracheostomy tube placement. Continuous systemic heparinization was used, maintaining whole blood activated clotting time (ACT) between 180 and 200 sec. Survival data are summarized as follows: pneumonia (n = 25) 56%, adult respiratory distress syndrome (n = 24) 58%, airway support (n = 2) 100%, and cardiac support (n = 14) 29%. The most common complication was bleeding (68%), which was managed in most patients by reduction of anticoagulation or local measures such as packing. Data from survivors and nonsurvivors of ECLS in patients with respiratory failure were compared in an attempt to define prognostic indicators of improved survival. The only prognostic indicator of survival that could be identified was the period of time on the ventilator before the initiation of ECLS (survivors = 3.0 +/- 2.4 days, nonsurvivors = 6.1 +/9- 4.0 days, P < 0.005). It is concluded that ECLS can be a life saving modality for the management of severe adult cardiorespiratory failure. Earlier institution of ECLS in the course of cardiopulmonary failure may improve outcome.

Oxygen delivery in the pediatric surgical patient

Support of oxygen delivery (DO2) is central to the care of the critically ill. Whether through interventions designed to correct deviations in cardiac output, oxygenation, or hemoglobin content, the overall therapeutic goal is to maintain perfusion and oxygen delivery to the tissues. In normal animals and humans, there is a biphasic relationship between oxygen consumption (VO2) and delivery in which VO2 remains stable as long as sufficient oxygen is delivered. If oxygen delivery is reduced below a critical value (DO2 crit), then oxygen consumption decreases. The mixed venous oxygen saturation serves as an excellent monitor of the adequacy of oxygen delivery in relation to oxygen consumption. As discussed in this review, controversy exists as to whether such VO2/DO2 relationships exist in patients with sepsis or the adult respiratory distress syndrome.