Noninvasive determination of cardiac output using single breath CO2 analysis

OBJECTIVE

To examine the utility of single breath CO2 analysis as a noninvasive measure of cardiac output.

SETTING

An animal laboratory in a university-affiliated medical center.

DESIGN

A prospective, animal cohort study comparing 21 parameters derived from single breath CO2 analysis with cardiac output determined by an ultrasonic flow probe.

SUBJECTS

Six healthy adult sheep.

METHODS

The single breath CO2 analysis station consists of a mainstream capnometer, a variable orifice pneumotachometer, a signal processor, and computer software with capability for both on- and off-line data analysis. Twenty-one derived components of the CO2 expirogram were evaluated as predictors of cardiac output. Cardiac output was manipulated by successive injections of a hydraulic constrictor placed around the inferior vena cava.

MEASUREMENTS AND MAIN RESULTS

Thirty-four measurements of cardiac output were available for comparison with derived variables from the CO2 expirogram. Stepwise linear regression identified two variables that were most predictive of cardiac output: a) the angle between the slope lines for phase II and III of the CO2 expirogram divided by the volume of CO2 per breath (angle/mL CO2); and b) the slope of phase II. The multivariate equation was highly statistically significant and explained 94% of the variance (adjusted r2 = .94, p < .0001). The bias and precision of the calculated cardiac output were .00 and .23, respectively. The mean percent difference for the cardiac output estimate derived from the single breath CO2 analysis station was 0.36%.

CONCLUSIONS

Our data indicate that analysis of the CO2 expirogram can yield accurate information about the cardiovascular system. Specifically, two variables derived from a plot of expired CO2 concentration vs. expired volume predict changes in cardiac output in healthy adult sheep with an adjusted coefficient of determination of .94. Prospective application of this technology in the setting of lung injury and rapidly changing physiology will be essential in determining the clinical usefulness of the technique.

Abdominal tuberculosis: the surgical perspective

The increasing incidence of pulmonary tuberculosis (TB) has led many to predict a corresponding increase in abdominal TB. This study reports the incidence, presentation, and outcome of abdominal TB to elucidate factors that might assist the surgeon to treat this potentially curable disease. A retrospective review of patients diagnosed with tuberculosis between 1993 and 1995 was performed at two hospitals. Diagnosis of abdominal TB was based on acid fast bacilli on tissue stains and/or culture. Seven patients were diagnosed with abdominal TB. Two patients were HIV positive; six were recent immigrants. Abdominal pain, fever, and significant weight loss were the most common symptoms. All preoperative radiologic tests failed to demonstrate findings suggestive of TB. All patients were brought to operation. Indications included perforated viscus (2), acute abdomen (1), small bowel obstruction (1), colocutaneous fistula (1), pelvic neoplasm (1), and biliary colic (1). Abdominal TB was either diagnosed or suspected intraoperatively in six patients. Postoperative anti-TB chemotherapy was promptly instituted. Although abdominal TB can be cured medically if treated early enough, the nonspecific presentation delays diagnosis in the majority of cases. Diagnosis of abdominal TB can be made or at least highly suspected intraoperatively such that anti-TB medications can be initiated promptly. Appropriate surgical therapy and prompt initiation of anti-tuberculosis medications can successfully treat abdominal TB.

MR in children with L-carnitine deficiency

PURPOSE

To describe the MR imaging findings in five children with proved L-carnitine deficiency.

METHODS

MR imaging studies (five without contrast, two with contrast) were obtained in five children (mean age, 9 years) who presented with stroke symptoms and who proved to have L-carnitine deficiency as established by serum levels.

RESULTS

In three of five patients, infarctions were confined to arterial distributions; one patient had a hemorrhagic infarction in one frontoparietal region; and one patient had only nonspecific periventricular white matter T2 hyper-intensities. Serum L-carnitine levels normalized after correction; sequelae included seizures in two patients, hemiparesis in one patient, normal outcome in one patient, and death in one patient.

CONCLUSION

L-Carnitine deficiency is a rare metabolic disorder leading to cerebral infarctions, as seen in our five patients, and should be considered in the differential diagnosis of children who have had a stroke, particularly when associated with hypoglycemia and myopathy.

Mesenteric angioplasty in the treatment of chronic intestinal ischemia

PURPOSE

This study was undertaken to determine the safety and efficacy of percutaneous transluminal angioplasty (PTA) in the treatment of chronic mesenteric ischemia (CMI) in very high-risk surgical patients.

METHODS

Twenty-four focal mesenteric stenoses treated from 1984 to 1994 by PTA in 19 patients with CMI were reviewed. All 19 patients were considered poor surgical candidates. Seventeen patients had classic symptoms of CMI, and two patients had atypical abdominal complaints. Vessels dilated included the superior mesenteric artery (18), celiac artery (3), inferior mesenteric artery (1), aorta-superior mesenteric artery vein graft (1), and aorta-splenic artery vein graft (1). Complete follow-up was possible in all patients, with the exception of one patient who had no symptoms when last seen 17 months after the procedure.

RESULTS

PTA was technically successful in 18 of 19 patients (95%) and 23 of 24 stenoses (96%). The lone technical failure resulted in superior mesenteric artery dissection with thrombosis and bowel infarction; the patient died despite emergent laparotomy and revascularization (mortality rate, 5%). Complete symptomatic relief was attained in 15 patients (79%), with follow-up showing continued relief of symptoms for a mean of 39 months (range, 4 to 101 months). Partial symptomatic relief was attained in three patients. Recurrent symptoms developed in three patients (20%) at a mean interval of 28 months (range, 9 to 43 months). Repeat PTA performed in two patients provided good technical results and relief from clinical symptoms. One patient had a symptomatic axillary sheath hematoma that required surgical decompression.

CONCLUSIONS

Mesenteric PTA is a valuable treatment option in patients who have CMI and are considered very high operative risks. The initial technical success rate is excellent, with the majority of patients having complete symptomatic improvement and continued relief of symptoms at short-term follow-up.

Asthma and atopy in four rural Australian aboriginal communities

OBJECTIVE

To determine the prevalence and nature of asthma in four rural Australian Aboriginal communities.

DESIGN

Cross-sectional population study.

SETTING

Four Aboriginal communities in Queensland, the Northern Territory and South Australia, Australia.

SUBJECTS

Data were collected from 1252 subjects aged 5-84 years in August 1990 and August/September 1991.

MAIN OUTCOME MEASURES

Respiratory symptoms, measured by interview-administered questionnaire; airway hyperresponsiveness (AHR), measured by histamine challenge; and allergy, measured by skin-pick tests. AHR was a PD20FEV1 of histamine of less than or equal to 3.9 mumol.

RESULTS

The prevalence of AHR in the four communities ranged from 2.2% to 7.5% and significantly increased with age (chi 2 trend test: P < 0.05). The prevalence of current asthma was 0.5% among 8-12 year old children and 3.3% among adults. The overall prevalence of atopy in the four communities ranged from 21% to 34%. Allergy to cats, house dust mites or cigarette smoking was a risk factor for AHR, and cat allergy was a risk factor for current asthma.

CONCLUSIONS

The prevalence of asthma in rural Aboriginal adults is low in comparison with the prevalence among non-Aboriginal Australians, and asthma in Aboriginal children is almost non-existent. The low prevalence of asthma is possibly due to environmental factors that influence the acquisition of atopy and AHR.

CT in adult supraglottitis

We describe the CT appearance of supraglottitis and its complications in three adults. The most common CT findings were thickening of the epiglottis, aryepiglottic folds, false and true vocal cords, obliteration of the preepiglottic fa, thickening of the platysma muscle, and reticulation of the subcutaneous fat. Multiple loculated fluid-density collections consistent with abscesses were seen in one patient. Although the diagnosis of supraglottitis is generally made on the basis of the patient's history and by direct endoscopy, CT may be used to confirm the diagnosis when an adequate laryngoscopic examination cannot be performed. CT is also useful in evaluating the complications of this disorder.

ECMO in evolution: the impact of changing patient demographics and alternative therapies on ECMO

The incidence of neonatal extracorporeal membrane oxygenation (ECMO) is decreasing nationally. This decrease is presumed to be a result of the emergence of alternative technologies such as high-frequency oscillatory ventilation (HFOV), nitric oxide (NO), and surfactant therapy as well as others. The purposes of the present report were to determine just how rapidly the demographics of ECMO are changing and to determine the impact of competing technologies on ECMO use. The authors reviewed their entire ECMO experience of 455 cases (370 neonatal, 38 pediatric, and 47 cardiac). The neonatal cases also were separated into diagnostic groups: MAS (meconium aspiration syndrome), PPHN (persistent pulmonary hypertension of the newborn), RDS (respiratory distress syndrome), and sepsis. To allow statistical comparison, the patients were divided into four chronological groups, of equal 3-year duration, spanning the 12 years that ECMO has been available. The results of the analysis demonstrated four principle findings. (1) The total number of patients receiving ECMO per year was declining (P = .0001). This decline was attributable to a reduction in the total number of neonatal patients, with the exception of cases of congenital diaphragmatic hernia. (2) The complexity of each ECMO run was increasing, as evidenced by substantial increases in mean ECMO duration per patient and an increase in the incidence of patient complications on ECMO (P = .0001). (3) There has been a significant decrease in the overall survival rate for patients treated with ECMO (P = .0001). (4) The ECMO population mix has shifted away from straightforward neonatal cases and toward the more complex pediatric and cardiac cases. This demographic shift has occurred as a result of improvements in pre-ECMO management of neonatal patients, and is primarily responsible for the findings noted above. However, there also has been a worsening of condition severity within each diagnostic group, which also is partly responsible for the changes noted. If these trends continue, pediatric, cardiac, and CDH patients will likely account for the majority of ECMO patients. Consequently, existing ECMO centers must be prepared to adapt to the changing demographics by evolving programs that support pediatric, cardiac, and adult patients, in addition to neonates. Furthermore, the complexity associated with transporting these unstable older patients and the likelihood that the number of active ECMO centers will decline may require remaining ECMO centers to develop long-distance ECMO transport capabilities.

Effects of nitric oxide on hyperinflation-induced pulmonary hypertension in the isolated-perfused lung

OBJECTIVE

To determine if nitric oxide decreases pulmonary vascular resistance in hyperinflation-induced pulmonary hypertension.

DESIGN

Isolated-perfused lamb lung model.

SETTING

Experimental animal laboratory in a university setting.

SUBJECTS

Ten isolated-perfused lamb lungs harvested from subjects with a mean age of 29 days.

INTERVENTIONS

After induction of anesthesia, endotracheal intubation, and mechanical ventilation, lungs were perfused via an extracorporeal circuit. Ventilatory pressures were set to provide tidal volumes of 10 mL/kg and ventilatory rates were adjusted to maintain a Paco2 of 40 +/- 5 torr (3.5 +/- 0.7 kPa). The perfusion system consisted of a blood reservoir, a membrane oxygenator, and a nonocclusive roller pump. Blood flow was increased progressively to 50 mL/kg/min, maintaining a pulmonary arterial pressure of < 25 mm Hg and a left atrial pressure between 2 and 5 mm Hg. End-expiratory lung volume was measured using a nitrogen washout method. Baseline data were collected after a 1-hr stabilization period. Lung volume was increased to achieve 25% (moderate hyperinflation) and 50% (severe hyperinflation) increments in pulmonary vascular resistance. Nitric oxide (80 parts per million) was administered to the preparation after each increment in lung volume.

MEASUREMENTS AND MAIN RESULTS

Mean pulmonary arterial pressure, mean left atrial pressure, pulmonary vascular resistance, and static lung compliance were measured at baseline and after moderate and severe hyperinflation, both before and after nitric oxide administration. Significant decreases in pulmonary vascular resistance were found when the preparation was ventilated with nitric oxide at baseline (43% decrease) and during hyperinflation induced pulmonary hypertension at both moderate (31% decrease) and severe (23% decrease) levels of hyperinflation.

CONCLUSIONS

Inhaled nitric oxide significantly reduces pulmonary vascular resistance, even when pulmonary hypertension is induced by airway hyperinflation and supraphysiologic lung volumes. These data suggest that the use of nitric oxide following lung transplantation may allow for effective management of pulmonary hypertension in patients who receive allografts from undersized donors. Further clinical experience will be crucial in precisely defining the range of donor-recipient size mismatch that can be adequately managed and the time course over which nitric oxide can be administered safely and effectively to these patients.

Vena cava injuries during laparoscopic cholecystectomy

Two instances of vena cava injury occurring during insertion of a new trocar for laparoscopic surgery are presented. The mechanism of injury in each case was identical. These injuries are extremely rare, and fortunately both patients survived. Any new instrument that is purported to be an improvement over existing ones should be critically evaluated so that needless and unnecessary injuries such as these can be avoided.

Subungual melanoma of the hand

Subungual melanoma is a rare but well-recognized tumor of the hand. Its management is ill defined and the factors influencing prognosis have not been well described. The clinicopathologic features of a series of 38 patients with subungual melanoma of the hand are reported. The median thickness was 3 mm, and only seven patients presented with pathologic stage I disease (American Joint Committee on Cancer [AJCC] system). Ulceration and lack of pigmentation were the only significant univariate prognostic indicators. There was no significant difference in local recurrence rates among patients whose amputation was carried out proximal or distal to the interphalangeal joint of the thumb or the middle of the middle phalanx in the other fingers. Management of the regional lymph node field based on the use of selective lymphadenectomy is described.

Is a twelve-percent cesarean section rate at a perinatal center safe?

OBJECTIVE

Our purpose was to examine the pregnancy and neonatal outcomes at a perinatal center with a consistent cesarean section rate approximately half the national average.

STUDY DESIGN

Ten years of vaginal delivery and cesarean section rates (1983 to 1992) and 5 years of mortality and morbidity outcomes (1988 to 1992) were compared with national health statistics and national health objectives.

RESULTS

The cesarean section rate during the 10-year period ranged from 10% to 15%, with an average of 12.5%. The cesarean section rate for the 5 years during which maternal and neonatal outcome data were obtained was 11.3%. The forceps and vacuum extraction rates during that time were consistently less than 5%. The nurse-midwifery service delivered approximately 36% of all babies during this period. In an examination of maternal mortality, we discovered only one death during the 5-year interval. The rate of maternal admission to the intensive care unit after delivery was 0.2%. The percent of women who received blood transfusions was 1%. The average length of stay for both vaginal and cesarean section deliveries declined steadily across the whole interval and was 2.5 days for a vaginal delivery and 5.5 days for a cesarean section. An examination of neonatal morbidity and mortality revealed an admission rate to the intensive care unit of less than 6%. The distribution of Apgar scores indicated less than 4% of neonates had scores < or = 3 at 1 minute; 0.5% had scores < or = 3 at 5 minutes. The neonatal death rate was 614 per 100,000 births, and fetal mortality was 729 per 100,000 births from 1988 to 1992.

CONCLUSIONS

The lowest safe cesarean section rate is not known; it will undoubtedly vary with location and patient mix. We believe that we have been able to establish a rate of cesarean section one half of the national average with good maternal and fetal outcomes. This has been accomplished through a vigorous prenatal care program, excellent perinatal and infertility services, a vigorous program of vaginal birth after cesarean section, and a competent nurse-midwifery service.

Single breath CO2 analysis: description and validation of a method

OBJECTIVES

To evaluate the performance of a newly developed single breath CO2 analysis station in measuring the airway deadspace in a lung model (study 1), and then to quantify the bias and precision of the physiologic deadspace measurement in a surfactant-depleted animal model (study 2).

DESIGN

A prospective bench validation of a new technique of airway deadspace measurement using a criterion standard (study 1); a prospective, animal cohort study comparing a new technique of physiologic deadspace measurement with a reference method (Bohr-Enghoff method) (study 2).

SETTING

A bench laboratory and animal laboratory in a university-affiliated medical center.

SUBJECTS

A lung model (study 1), and adult sheep with induced surfactant deficiency (saline lavage) (study 2).

METHODS

The single breath CO2 analysis station consists of a mainstream capnometer, a variable orifice pneumotachometer, a signal processor, and computer software with capability for both on- and off-line data analysis. Study 1: We evaluated the accuracy of the airway deadspace calculation using a plexiglass lung model. The capnometer and pneumotachometer were placed at the ventilator Y-piece with polyvinyl chloride tubing added to simulate increased airway deadspace. Segments of tubing were sequentially removed during each testing session to simulate decreasing deadspace. The calculated airway deadspace was derived from the single breath CO2 plot and compared with the actual tubing volume using least-squares linear regression and paired t-tests. Study 2: The accuracy of the physiologic deadspace measurement was examined in a saline-lavaged animal model by comparing the physiologic deadspace calculated from the single breath CO2 analysis station with values obtained using the Enghoff modification of the Bohr equation: deadspace/tidal volume ratio = (PaCO2-mixed expired PCO2)/PaCO2.

MEASUREMENTS AND MAIN RESULTS

Study 1: Thirty-six measurements of calculated airway deadspace were made and compared with actual circuit deadspace during four different testing conditions. Measured airway deadspace correlated significantly with actual circuit deadspace (r2 = .99). The proportional error of the method was -0.8% with a 95% confidence interval from -3.6% to 1.9%. Study 2: A total of 27 pairs of measurements in four different animals were available for analysis. The derived physiologic deadspace/tidal volume ratio significantly correlated with the value obtained using the Bohr-Enghoff method (r2 = .84). The bias and precision of our physiologic deadspace calculation were .02 and .02, respectively, and the mean percent difference for the physiologic deadspace calculated from the single breath CO2 analysis station was 2.4%.

CONCLUSIONS

Our initial experience with the single breath CO2 analysis station indicates that this device can reliably provide on-line evaluation of the single-breath CO2 waveform. In particular, estimation of the airway and physiologic deadspace under a variety of testing conditions was consistently within 5% of actual values. We feel that with further application and refinement of the technique, single breath CO2 analysis may provide a noninvasive, on-line monitor of changes in pulmonary blood flow.

Why should midwives be concerned with ethics?

Is there such a thing as midwifery ethics? Yes, there is. As human beings (moral agents), midwives are to be ethical, moral, responsible persons and professionals. Midwives work in moral relationships with other persons. They serve by the moral standards of their profession as now embodied in written codes of ethics, a profession that is part of the larger health care profession. As part of the professional world, midwives participate in the general standard that to be professional is to be ethical and to be unethical is to be unprofessional. The professions, in turn, are part of what Eric Fromm calls "human ethics." If midwives are to be ethical, we suggest they need to understand ethics and to reason morally. Better health care for all is the result.

MR of recurrent high-grade astrocytomas after intralesional immunotherapy

PURPOSE

To describe the MR findings in six patients with recurrent cerebral astrocytomas before, immediately after, and 3 months after local immunotherapy with tumor-infiltrating lymphocytes and interleukin-2.

METHODS

Contrast-enhanced MR studies were obtained in six patients (three with anaplastic astrocytoma and three with glioblastoma multiforme) at the time of tumor recurrence, after a second resection and placement of an Ommaya catheter, at the end of immunotherapy, and thereafter at 3-month intervals. These MR studies were reviewed with special attention to pattern and degree of enhancement, edema, and mass effect.

RESULTS

In three patients, gross total removal of recurrent tumor was achieved and postimmunotherapy MR studies showed a flare phenomenon characterized by increased nodular enhancement, increased edema, and mass effect. On the 3-month follow-up examination, these findings had resolved, and no further tumor recurrence was seen during the following 12-month period. Neither of the two patients who had subtotal resection had a flare phenomenon. In one of these patients, the tumor was stable at the 12-month follow-up; the other patient had recurrent tumor at the 6-month follow-up. In the last patient, who also had subtotal tumor resection and progressive enhancement after immunotherapy, tumor progression was rapid.

CONCLUSION

After local immunotherapy, increased enhancement, edema, and mass effect are most likely the result of a flare phenomenon, but because rapid tumor progression may produce similar features, follow-up MR studies are indispensable. The flare phenomenon resolved by 3 months in all patients.

Estrogen receptors in gallbladder cancer: detection by an improved immunohistochemical assay

Although gallbladder carcinoma is the most common malignancy of the extrahepatic biliary tract, patients with this disease have a very poor prognosis. Previous investigations have documented the presence of estrogen receptors (ER) in gallbladder cancers for possible therapeutic benefit; however, the methods used for detection were largely imprecise, which led to a wide range of results. In light of these unclear results obtained with inferior techniques, we have attempted to determine more accurately the prevalence of ER positivity in gallbladder cancer using an improved, more specific immunohistochemical assay (IHA) for estrogen receptors. The IHA, which used a pronase pretreatment and the H222 monoclonal antibody, was performed on archival tumor specimens of 25 patients. There were no strongly or moderately positive specimens. Three specimens stained weakly positive, and 22 specimens (88%) were negative. The three specimens that were weakly positive showed neither statistical significance nor any identifiable trends with respect to patient sex, tumor stage, or histologic type. We conclude that, contrary to previous reports, weak estrogen receptor staining occurs in a very small percentage of gallbladder carcinomas. Furthermore, although the minimum concentration of ER required for potential therapeutic benefit is unclear, the addition of hormonal therapy in patients with gallbladder cancer is not likely to alter the outcome of this malignancy.

Bacteriology of skin and soft-tissue infections: comparison of infections in intravenous drug users and individuals with no history of intravenous drug use

The bacteriology of cutaneous or subcutaneous abscesses (86 specimens) among intravenous drug users (IVDUs) was compared with the bacteriology of abscesses (74 specimens) in patients with no history of intravenous drug use (non-IVDUs). The IVDU abscesses yielded 173 aerobes and 131 anaerobes. Staphylococcus aureus was the most common aerobe isolated (50% of specimens yielded this isolate), followed by "Streptococcus milleri" (46%). The commonly encountered anaerobes were Fusobacterium nucleatum (17%), pigmented Prevotella species (22%), Peptostreptococcus micros (17%), Actinomyces odontolyticus (15%), and Veillonella species (13%). The non-IVDU isolates included 116 aerobes and 106 anaerobes. S. aureus was isolated from 53% of these specimens, followed by coagulase-negative staphylococci (19%), "S. milleri" (19%), and Streptococcus pyogenes (16%). The main groups of anaerobes were Peptostreptococcus species (35%), Bacteroides species (19%), and gram-positive bacilli (31%). Overall, 67% of the IVDU isolates were of oral origin, compared with 25% of the non-IVDU isolates. Of the specimens from IVDUs and non-IVDUs, 48% and 67%, respectively, yielded only aerobes, and 2% and 4%, respectively, yielded only anaerobes. Sixty-four percent of the patients had one or more beta-lactamase-producing organisms.

Isolation of nonsedimentable lipid-protein particles from insect intestine

Nonsedimentable lipid-protein particles have been isolated from intestinal tissue of the American cockroach, Periplaneta americana. Most of the particles were within the range 30-50 nm in diameter and appear to originate from larger structures. Lipid analysis of the particles showed them to be enriched in neutral lipid components relative to microsomal membranes. Specifically, there is a decline in the amounts of phosphatidylcholine and phosphatidylethanolamine in the nonsedimentable particles compared with the microsomal membranes. Also, in contrast to microsomal membranes, the particles have a higher content of phosphatidic acid along with 1,2- and 1,3-diacyglycerols, free fatty acids and an unidentified lipid that co-migrates with sterol ester, wax ester and hydrocarbon standards in thin layer chromatograms. The cytosol, separated from the particles by ultrafiltration, contained phosphatidic acid, free fatty acids and the unidentified lipid. By contrast, the composition of neutral lipids in the cytosol resembles that of the particles. SDS-PAGE analysis of microsomal membranes, the particles and particle free cytosol shows an enrichment of low molecular weight proteins in the particles and cytosol. The particles and cytosol appear to possess proteolytic activity that is distinguishable from that of corresponding microsomal membranes since the incubation of these components with BSA resulted in the formation of distinct polypeptides. Many characteristics of these particles resemble those of the deteriosomes that have been isolated from plant tissue.

Inhaled nitric oxide and hemodynamic evaluation of patients with pulmonary hypertension before transplantation

OBJECTIVES

We investigated the effect of inhaled nitric oxide and infused acetylcholine in patients with pulmonary hypertension undergoing cardiac catheterization before cardiopulmonary transplantation.

BACKGROUND

The fate of patients under consideration for transplantation of the heart or lungs, or both, is influenced by the evaluation of their pulmonary vascular reactivity.

METHODS

We evaluated 11 patients who were classified into two groups on the basis of mean left atrial pressure > 15 mm Hg (group I, n = 6) or < or = 15 mm Hg (group II, n = 5). All patients inhaled nitric oxide at 80 ppm. This was preceded by an infusion of 10(-6) mol/liter of acetylcholine in seven consecutive patients (n = 3 in group I, n = 4 in group II).

RESULTS

In group I, inhaled nitric oxide decreased pulmonary artery pressure from (mean +/- SE) 71 +/- 13 to 59 +/- 10 mm Hg (p < 0.05), pulmonary vascular resistance from 14.9 +/- 3.8 to 7.6 +/- 1.7 Um2 (p < 0.05) and intrapulmonary shunt fraction from 17.8 +/- 3.6% to 12.7 +/- 2.1% (p < 0.05). Left atrial pressure tended to increase from 27 +/- 4 to 32 +/- 5 mm Hg (p = 0.07). In group II pulmonary vascular resistance decreased in response to nitric oxide from 36.4 +/- 9.0 to 31.1 +/- 7.9 Um2 (p < 0.05). Cardiac index, systemic pressure and resistance did not change in either group. Seven patients who received acetylcholine had no significant alteration in pulmonary hemodynamic variables.

CONCLUSIONS

These preliminary observations suggest that nitric oxide is a potent pulmonary vasodilator with minimal systemic effects. It may be useful in discriminating patients needing combined heart and lung transplantation from those requiring exchange of the heart alone.

I kappa B-beta regulates the persistent response in a biphasic activation of NF-kappa B

We have cloned the cDNA encoding I kappa B-beta, one of the two major I kappa B isoforms in mammalian cells. The recombinant I kappa B- beta protein interacts with equal affinity to p65 and c-Rel and does not exhibit a preference between these Rel proteins. Instead the primary difference between I kapp B-alpha and I kappa B-beta is in their response to different inducers of NF-kappa B activity. One class of inducers causes rapid but transient activation of NF-kappa B by primarily affecting I kappa B-alpha complexes, whereas another class of inducers causes persistent activation of NF-kapa B by affecting both I kappa B-alpha and I kappa B-beta complexes. Therefore, the overall activation of NF-kappa B consists of two overlapping phases, a transient phase mediated through I kappa B-alpha and a persistent phase mediated through I kappa B-beta.

Respiratory deadspace measurements in neonates with congenital diaphragmatic hernia

OBJECTIVE

To apply the technique of respiratory deadspace measurement to consecutive infants with congenital diaphragmatic hernia, who were referred to our institution, in order to assess the efficiency of gas exchange.

DESIGN

A cohort study evaluating the utility of deadspace measurements in neonates with congenital diaphragmatic hernia.

SETTING

Tertiary care pediatric intensive care unit in a university hospital.

PATIENTS

Thirty infants with congenital diaphragmatic hernia were studied on presentation to our institution, either before the institution of extracorporeal membrane oxygenation (ECMO) or after stabilization on ECMO.

METHODS

The CO2 concentration of expired gas sampled at the exhaust port of the test ventilator was continuously measured and transformed to mixed expired CO2 by the following formula that corrects for compressible volume measured by the ventilatory pneumotachometer: mixed expired CO2 = (PCO2 in exhaust gas) x (ventilatory pneumotachometer minute volume)/(minute volume at the proximal airway). We then utilized the Bohr-Enghoff method to calculate the deadspace/tidal volume ratio: deadspace/tidal volume ratio = (PaCO2 - mixed expired PCO2)/PaCO2.

MEASUREMENTS AND MAIN RESULTS

Deadspace/tidal volume ratio was calculated either before the institution of ECMO or during temporary separation from ECMO support as the patients demonstrated improvements in gas exchange and lung compliance. One hundred two measurements were made in 30 patients, with a mean of four measurements per patient (range 1 to 10). There was a significant (p = .005) difference between the first deadspace/tidal volume ratio measured, in survivors vs. nonsurvivors. The mean of the highest deadspace/tidal volume ratio in survivors was 0.47 compared with 0.62 in nonsurvivors (p = .003). A deadspace/tidal volume ratio of > or = 0.60 predicted mortality, with a positive predictive value of 80%, a negative predictive value of 79%, and an odds ratio of 15. The mean pre-ECMO deadspace/tidal volume ratio in those infants who ultimately required ECMO was significantly greater than the mean value for infants not requiring ECMO (0.65 vs. 0.43; p = .004). In patients who were treated with ECMO, survivors demonstrated a significant decrease in deadspace/tidal volume ratio during the course of ECMO. This decrease was not seen in the ECMO-treated patients who did not survive.

CONCLUSIONS

Predictors of outcome in infants with congenital diaphragmatic hernia have been complicated and contradictory, particularly in the ECMO era. We demonstrated that the respiratory deadspace can be easily quantified in these infants, and that a physiologic deadspace of > 0.60 is associated with a 15-fold increase in mortality rate. We also demonstrated that in those infants treated with ECMO, the survivors manifested a significant decrease in their deadspace/tidal volume ratio before ECMO decannulation.