Biomedical subjects
H Kirpalani
Publications and source records attributed to H Kirpalani.
Birthweight, early passive respiratory system mechanics, and ventilator requirements as predictors of outcome in premature infants with respiratory failure.
Early respiratory mechanics have been reported to predict outcome in newborns with respiratory failure. However, it remains unknown whether measurements of pulmonary function add significantly to the predictive value of more readily available variables The present study was designed to answer this question. Passive respiratory system mechanics were measured by an airway occlusion technique in 104 ventilator-dependent premature infants between 6 and 48 hours of life and corrected for infant size. A ventilation index [FiO2 x mean airway pressure (MAP)] was calculated at the time of pulmonary function testing. Poor outcome was defined as death from respiratory failure or need for supplemental oxygen at 28 days. Stepwise logistic function regression examined whether ventilation index and respiratory mechanics added predictive power over and above birthweight. Five infants died, and 45 patients required supplemental oxygen at 28 days. Birthweight was a strong predictor and would have entered the logistic model first in any case. Ventilation index added significantly to the predictive model (P = 0.038). Respiratory system conductance (P = 0.15) and compliance (P = 0.93) entered on the third and last step, respectively. We conclude that in premature infants with respiratory failure, birthweight is a strong predictor of outcome. Early ventilator requirements but not respiratory system mechanics, add significantly to this predictive model.
Informational needs of parents of sick neonates.
Sixty-one parents of 43 neonates in a neonatal intensive care unit were interviewed within 3 days of their first conference with the neonatologist to assess their needs for medical information. The conference with the physician and the interview with the investigator were audiotaped. Information given by the physician and information recalled by the parents was categorized and rated by the investigator. The physicians gave very detailed information about diagnosis in 77% of cases whereas 39% of the parents recalled diagnostic information in great detail. Respective percentages for prognosis were 16 and 33; for current management (eg, investigation, therapy), 28 and 66; and for cause of illness, 16 and 18. The statistical significance of the differences between the very detailed information int he physician-parent conferences and in the parent-investigator interviews was, by category, less than .002, less than .041, less than .004, and not significant, respectively. Information in the respective categories was described as "most helpful" by 20%, 67%, 90%, and 8% of parents. All but one of the parents stated that they wanted the whole truth. Physician uncertainty in providing information was significantly associated with severity of illness. It is concluded that while parents wanted information in all categories, they paid most attention to that relating to management. Physician-parent discordances with respect to information about management, diagnosis, and prognosis suggest directions for future investigation of the optimal content of information for parents in this context.
The Medical reform Group has a purpose.
Explore the source record for details and available documents.
End-tidal carbon dioxide measurements in critically ill neonates: a comparison of side-stream and mainstream capnometers.
To determine whether end-tidal PCO2 (PETCO2) measurements obtained with two infrared capnometers accurately approximates the arterial PCO2 (PaCO2) in critically ill neonates, simultaneous measurements of PETCO2 were obtained from the distal and proximal ends of the tracheal tube with a sidestream capnometer (Puritan Bennett/Datex--BP/D) and from the proximal end with a mainstream capnometer (Hewlett-Packard-HP) in 20 intubated neonates. Distal sidestream PETCO2 and mainstream PETCO2 correlated with the PaCO2 (r2 = 0.66 and 0.61, respectively) within the range of 26-57 mmHg PaCO2. However, proximal PETCO2 with the sidestream capnometer correlated very poorly (r2 = 0.09) with PaCO2. The slope of the least square regression line for the distal sidestream capnometer, 0.67, was significantly less than that for the mainstream capnometer, 0.78 but both were significantly greater than that for the proximal sidestream capnometer, 0.39 (P less than 0.05). The slope of the regression for the proximal sidestream capnometer did not differ significantly from horizontal. Insertion of the mainstream sensor for the HP capnometer significantly increased the transcutaneous CO2 when compared with preinsertion values. We conclude that both distal sidestream and mainstream capnometry provide accurate estimates of the PaCO2 in critically ill neonates.
Measuring on-line compliance in ventilated infants using hot wire anemometry.
We investigated the validity of using tidal volume (VT) as measured by the neonatal volume monitor (NVM) to derive respiratory compliance. The NVM is a noninvasive device that measures VT by hot wire anemometry. The quotient of VT and the inflation pressure amplitude from the mechanical ventilator provided a measure of respiratory compliance. This was validated against the single breath occlusion technique in 15 infants (birth weight 0.9 to 4.4 kg). To ensure fully passive expiration, only paralyzed or sedated patients were studied. Only 12 of the 15 infants were analyzed because of limitations in the single breath technique. In three infants the flow-volume curves obtained were alinear, indicating inhomogeneity. In the 12 infants with acceptable single breath data, agreement between the two methods was excellent. Using the expired volume, r2 was .99. We conclude that the NVM can be used to obtain valid estimates of respiratory compliance on-line in intubated infants.
Respiratory response and pharmacokinetics of intravenous salbutamol in infants with bronchopulmonary dysplasia.
The effects of iv salbutamol on respiratory mechanics were studied in six infants with bronchopulmonary dysplasia. Salbutamol was infused at a dose of 30 micrograms/kg over 30 min in five infants; a sixth infant received 66.7 micrograms/kg over 4 min. Salbutamol caused improvement in total respiratory system compliance and in airflow resistance. There was no correlation between salbutamol serum concentration and pulmonary function. Elimination half-time appears to be dictated in these infants more by the distribution volume (Vd) than by clearance (Cl). The area under concentration-time curve of salbutamol correlated inversely to the change in heart rate (HR). There was a significant positive correlation between Vd and percent HR change. These data provide evidence that preterm infants have measurable activity of bronchiolar beta 2 receptor responsive to salbutamol.
Widened subarachnoid space in pre-discharge cranial ultrasound: evidence of cerebral atrophy in immature infants?
The authors examined the incidence of widened subarachnoid spaces (SAS) among 75 infants with birthweights less than or equal to 1250g, and their significance in developmental outcome. Nine of 30 infants with gestations less than or equal to 27 weeks had widened SAS in their pre-discharge ultrasound scans. Three of the nine, including two with periventricular leukomalacia (PVL), had late-onset ventricular enlargement, unrelated to intraventricular haemorrhage (IVH): all three were developmentally impaired. The other six infants without ventricular enlargement developed normally, including one with IVH. Five of the remaining 21 infants with gestations less than or equal to 27 weeks and without widened SAS were developmentally impaired. Widened SAS was not associated with a significantly increased risk of developmental impairment; ventricular enlargement and PVL were the only significant factors. The authors conclude that an isolated finding of widened SAS is not predictive of impairment in immature infants.
Case 6. Perinatal hemochromatosis.
Explore the source record for details and available documents.
Searching MEDLINE for randomized clinical trials involving care of the newborn.
Randomized clinical trials make up only a small fraction of published articles concerning care of the newborn infant and an even smaller fraction of articles about all human subjects. The busy pediatrician who wants to keep abreast of the medical literature requires strategies to detect such relevant studies promptly and reliably. Computer searching of MEDLINE is an attractive, potentially powerful but not sufficiently validated means of achieving this goal. Therefore, the sensitivity, specificity, and positive predictive value of two MEDLINE search strategies designed to detect randomized clinical trials for prevention and treatment of newborn diseases among all original articles about human subjects appearing in ten pediatric and general medical journals during 1985 were determined. The yield of both MEDLINE searches was compared to that of a manual search. Fifty-three randomized clinical trials of newborn care were identified by hand search among 233 articles concerning care of the newborn and 2,988 original articles about human subjects. The sensitivities of the MEDLINE searches were 53% and 34%, respectively, and the positive predictive values were 82% and 69%, respectively. Specificity of both computer searches was virtually 100%. Twenty-one randomized clinical trials were not identified by either MEDLINE search strategy, 17 of them for failure of the indexer to assign any methodologic terms at all or failure to assign sufficiently stringent methodologic terms. Consequently, sensitivities were higher, 77% and 68% respectively, when no methodologic terms were used during repeat searches. However, positive predictive values decreased concomitantly to 20% or less.(ABSTRACT TRUNCATED AT 250 WORDS)
Strengths and limitations of the Apgar score: a critical appraisal.
The Apgar score is widely used for several purposes: to discriminate between infants who require resuscitation at birth and those who do not; to predict outcome; and to evaluate change in the condition of the newly born over the first minutes of life. Using published evidence of its clinical reliability and validity, this article explores whether the Apgar score serves all three measurement purposes equally well. Methodologic guidelines for assessing health indices are applied to examine the structure of the Apgar score as well as its function where performance data are lacking or inadequate. Despite the advent of modern technology, the Apgar score remains the best tool for the identification of newly born infants in need for cardiopulmonary resuscitation. For predicting later death or handicap, the Apgar score is insensitive but fairly specific. The ability of the Apgar score to measure change over time has not been studied systematically; however, available data suggest that serial Apgar ratings in infants with early low scores detect clinically important recovery of lack thereof.
End-tidal, transcutaneous, and arterial pCO2 measurements in critically ill neonates: a comparative study.
Explore the source record for details and available documents.
High-frequency oscillation in the rescue of infants with persistent pulmonary hypertension.
High-frequency oscillatory ventilation (HFOV) was used to treat 41 infants with persistent pulmonary hypertension of the newborn (PPHN). Of the 37 patients who showed early improvement on HFOV, three died. The remaining 34 patients demonstrated, within one hour of the switchover to HFOV, a rise in mean arterial/alveolar oxygen tension ratio (PaO2/PaO2) from 0.093 +/- 0.041 (SD) to 0.132 +/- 0.051 (p less than .001), and a fall in mean PaCO2 from 42 +/- 10 to 34 +/- torr 9 (p less than .01). Mean airway pressure (Paw) fell significantly (p less than .01) within 12 h. The mean duration of conventional mechanical ventilation before starting HFOV was longer in 13 patients who developed bronchopulmonary dysplasia (BPD) than in 21 non-BPD patients (44.7 +/- 32.3 vs. 19.1 +/- 15.6 h, p less than .002), as was the duration of exposure to Paw greater than 15 cm H2O during that treatment mode (31.8 +/- 21.3 vs. 9.5 +/- 6.0 h, p less than .001). HFOV is often effective in the treatment of patients with PPHN, and early initiation of this type of mechanical ventilation may be associated with a reduced incidence of BPD.
Some infant ventilators do not limit peak inspiratory pressure reliably during active expiration.
In order to minimize barotrauma in newborn infants with respiratory failure, peak inspiratory pressures should not exceed those required for adequate gas exchange. We examined whether four commonly used pressure-limited, constant flow ventilators limit pressure reliably during simulated active expiration against the inspiratory stroke of the ventilator. Three machines of each type were tested at 13 different expiratory flow rates (2 to 14 L/min). Flow-dependent pressure overshoot above a dialed pressure limit of 20 cm H2O was observed in all machines. However, the magnitude differed significantly between ventilators from different manufacturers (p = .0009). Pressure overshoot above 20 cm H2O was consistently lowest in the Healthdyne (0.8 cm H2O at 2 L/min, 3.6 cm H2O at 14 L/min) and highest in the Bourns BP200 (3.0 cm H2O at 2 L/min, 15.4 cm H2O at 14 L/min). We conclude that peak inspiratory pressure overshoots on pressure-limited ventilators occur during asynchronous expiration. This shortcoming may contribute to barotrauma in newborn infants who "fight" positive-pressure ventilation.
Comparison of the digitalis receptor in erythrocytes from preterm infants and adults.
We compared 86rubidium by erythrocytes of preterm infants and adults as a measurement of their Na+, K+, ATPase enzyme system. In neonates, total uptake (0.92 +/- 0.13 micrograms/10(6) cells) and specific uptake (0.64 +/- 0.076 micrograms/10(6) cells) were significantly higher than in adults (0.52 +/- 0.1 and 0.29 +/- 0.06 micrograms/10(6) cells, respectively; p less than 0.025). The percentage of specific uptake from total uptake was higher in infants (73.3 +/- 2.3%) than in adults (57.9 +/- 4.6%) (p less than 0.005). No differences were found in the affinity constant of 86Rb uptake between infants (4.35 +/- 0.48 ng/ml) and adults (4.85 +/- 0.48 ng/ml). Stratification of infants according to their serum K+ concentrations revealed that levels above 5.4 mEq/liter were associated with a higher specific uptake (0.79 +/- 0.107 micrograms/10(6) cells) than in normokalemic infants (0.54 +/- 0.09 micrograms/10(6) cells) or adults (0.304 +/- 0.061 micrograms/10(6) cells) (p less than 0.05). The difference between hyperkalemic and normokalemic infants persisted after excluding those who received adult packed cells (0.88 +/- 0.1 and 0.6 +/- 0.12 micrograms/10(6) cells, respectively) (p less than 0.05). Infants with serum K+ greater than 5.8 mEq/liter received on average significantly more K+ in previous days (2.46 +/- 0.49 versus 1.13 + 0.34 mEq/kg.day; p less than 0.025). The different K+ level could not be attributed to different creatinine clearance in the two groups.
Necrotizing tracheobronchitis.
Explore the source record for details and available documents.
Diagnosis and therapy of necrotizing tracheobronchitis in ventilated neonates.
From January 1983 to September 1984 our neonatal ICU (NICU) treated eight endotracheally intubated infants who had suspected airway obstruction characterized by hypercarbia dissonant with severity of lung disease and difficulty in ventilation with lack of chest movement, both on conventional intermittent mandatory ventilation and high-frequency oscillation. Bronchoscopic removal of necrotic tissue was possible in six infants, two of whom survived. Bronchoscopy showed desquamation of epithelial surfaces, leaving encrusted exudations considered to be characteristic of necrotizing tracheobronchitis (NTB). The four nonsurvivors of bronchoscopy and one of the infants not submitted to bronchoscopy had NTB confirmed at autopsy. NTB was not associated with any specific lung disease, humidifier, or ventilator. The autopsy frequency of NTB during this period was 5 per 160 NICU admissions. A separate chart review of unselected autopsied cases in 1981 and 1982 showed that 12 of 284 neonates admitted to the NICU had NTB. NTB appears to be a rediscovered condition related to endotracheal intubation and mechanical ventilation using high mean airway pressures.
Technical and clinical aspects of capnography in neonates.
This article reviews the current literature on the uses of capnometry and capnography as applied to neonates. The first part addresses the technical aspects and principles of the measurements, including definitions. The features of available carbon dioxide analysers are discussed and factors known to influence their accuracy are highlighted. In the second part of this paper, in vivo studies in neonates are reviewed, with particular emphasis on understanding why the accuracy of end-tidal CO2 measurements differs among studies. This is attributable to various factors: aspiration flow rate, the sampling site (whether distal or proximal) and the type of capnometer. The critical limitation of their overall accuracy in the presence of lung disease is discussed. Potential applications are considered, as are the current limitations of transcutaneous monitoring. We conclude that capnometry with capnography is a potentially useful tool to arterial CO2 tension (PaCO2) monitor infants with normal lungs.