Neurologic uncertainty in newborn intensive care.
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Brain Death↗
Biomedical subjects
J F Watchko
Publications and source records attributed to J F Watchko.
Efficacy of thromboresistant umbilical artery catheters in reducing aortic thrombosis and related complications.
Previous in vitro and in vivo reports suggest that catheters constructed of polyurethane with heparin bonded to the surface (HB-PU) are less thrombogenic than catheters made of polyvinyl chloride (PVC). A randomized trial sufficiently large (power 80%) to detect a reduction in the incidence of umbilical artery (UA) catheter complications, including aortic thrombus formation, from 45% to 20% was conducted in 125 infants. The infants were monitored for complications possibly related to the use of a UA catheter, such as systemic hypertension and abnormalities of lower extremity perfusion. The presence of aortic thrombi was assessed by ultrasound study 3.5 +/- 1.2 (SD) days and 11.1 +/- 2.3 days after insertion of the catheter. The use of HB-PU umbilical catheters did not lead to a significant reduction in the incidence of complications and aortic thrombi compared with the use of PVC catheters. The lack of reduction may have been related to the prolonged duration of catheter use in both groups. A much larger study would have been required to detect a smaller, but perhaps clinically significant, reduction in catheter-associated complications.
Aorta↗
Diaphragmatic function during hypercapnia: neonatal and developmental aspects.
The effect of acute hypercapnia on diaphragmatic force output was studied in 6 young (4-8 days) and 6 older (16-20 days) anesthetized, spontaneously breathing piglets. Diaphragmatic force output was assessed by analysis of the transdiaphragmatic pressure (Pdi) generated during phrenic nerve stimulation. Pdi was measured under base-line conditions (50% O2-50% N2) and after 10 min of hypercapnia induced by breathing 5, 10, or 15% CO2 balanced with N2 and 50% O2. Pdi was significantly less than base line during the 10 and 15% hypercapnic conditions in the young (P less than 0.05) but not the older piglets. End-expiratory lung volume was noted to decrease during 15% CO2 hypercapnia. Force output augmentation occurred at this lower end-expiratory lung volume and was significantly greater in the older piglet compared with its younger counterpart (P less than 0.05). When the effects of lung volume on Pdi were corrected for, there was no age-related difference in the response to 15% CO2 hypercapnia. We conclude that severe hypercapnia has a depressant effect on diaphragmatic force output in both young and older piglets, and a differential augmentation in diaphragmatic force-output gain occurs at lower end-expiratory lung volume between young and older piglets, with the greater output occurring in the more mature animal.
Animals↗
Effect of inspiratory resistive loading on costal and crural diaphragm electromyograms in piglets.
We examined the effect of inspiratory resistive loaded breathing (IRL) on the electromyographic (EMG) activity of the costal and crural diaphragm in nine anesthetized spontaneously breathing piglets (age 10-23 days, weight 2.8-4.4 kg). Bipolar wire electrodes were inserted into the anterior paratendinous costal diaphragm and the midportion of the crural diaphragm. EMG activity was quantified in arbitrary units (au) of peak moving time average while the animals breathed 50% O2/50% N2 (baseline) and during 30 min of IRL. Thirty min of IRL increased the peak moving time average of both parts of the diaphragm, with the increase in the crural EMG activity (from baseline: 22 +/- 2 to 30 min of IRL: 76 +/- 22 au) exceeding that of costal (from baseline: 23 +/- 2 to 30 min of IRL: 50 +/- 24 au), p less than 0.05. These results 1) suggest that the inspiratory EMG activity of the diaphragm can be differentially distributed between its costal and crural components and 2) document that crural inspiratory EMG activity undergoes greater augmentation under the condition of IRL than does the costal activity in piglets.
Animals↗
Response to resistive loading in the newborn piglet.
The diaphragmatic force generation and electromyographic response to long-term (1 h) inspiratory resistive loading was examined in the newborn piglet during the 3rd postnatal wk of life. Minute ventilation decreased to approximately 50% of baseline level within 5 min of imposition of a severe resistive load and remained at this level for the duration of loading. The decrease in ventilation was secondary to a fall in tidal volume at a constant frequency. There was a significant increase in central nervous system output to the diaphragm as manifested by integrated diaphragmatic electromyogram. Progressive augmentation of this index of central drive continued throughout the period of loading. Functional residual capacity fell significantly by 60 min of inspiratory resistive loading. This strategy should allow greater force generation by placing the diaphragm at a more optimal length-tension relationship. However, the force generating capability of the diaphragm was compromised as assessed by force-frequency curve analysis. These results suggest that the diaphragm of the neonatal piglet fatigues during prolonged inspiratory resistive loading.
Airway Resistance↗
Spectral analysis of diaphragmatic EMG during the neonatal biphasic hypoxic ventilatory response.
The newborn infant monkey consistently demonstrates a biphasic ventilatory response to hypoxemia. We have previously shown that the ventilatory depression during the late portion of this biphasic response is secondary to a decline in inspiratory volume that cannot be explained solely by central neural depression. We hypothesized that hypoxemia caused the diaphragm to fatigue, thereby accounting for the late ventilatory depression during the biphasic neonatal hypoxic response. Diaphragmatic fatigue has been reported to be associated with a decrease in the centroid frequency (Fc) of the electromyogram derived through frequency spectral analysis. Therefore, we analyzed the power spectral density of the diaphragmatic electromyogram recorded from percutaneously implanted crural diaphragmatic electrodes in five 2-day-old infant monkeys while they breathed room air and after 5 min exposure to two levels of hypoxemia during the late ventilatory depression. A fast Fourier transform of EKG free diaphragmatic electromyogram was used to compute the power spectral density and the Fc. The Fc during room air breathing was statistically equivalent to the Fc observed after five minutes exposure to 12% FiO2 (p = 0.79), and 8% FiO2 (p = 0.74) when ventilation was falling. In conclusion, our data demonstrate that changes in the centroid frequency are not present during the biphasic ventilatory decline that occurs with the hypoxic ventilatory response in newborn monkeys. Thus, diaphragmatic fatigue, as defined by a decline in Fc, does not occur during the neonatal biphasic hypoxic response.
Animals↗
Diaphragmatic muscle fiber type development in swine.
Diaphragmatic muscle fiber types were determined in the costal and crural segments of swine diaphragm at 4 postnatal ages (1 day, 1 month, 6 months, and between 3-6 yr of age). Fiber types were differentiated by enzyme histochemistry for adenosine triphosphatase and reduced nicotinamide adenine dinucleotide. A progressive increase in the number of type I fibers occurred in both costal and crural segments from birth to 6 months of age. The number of type IIA fibers decreased and type IIB fibers increased over the same time period. Type IIC fibers were present through 1 month of age, were rarely observed at 6 months, and were not found in older animals. Type I fibers were more numerous in the crural portion of the diaphragm. The cross-sectional area of all fiber types in both costal and crural segments increased significantly with age. No preferential fiber type growth was noted in either segment of the diaphragm. These data suggest that the pig diaphragmatic muscle is differentiated into its adult form by 6 months of postnatal age, but fiber cross-sectional area growth continues along with body growth.
Adenosine Triphosphatases↗
Neurodevelopmental outcome following persistent pulmonary hypertension of the neonate.
The neurodevelopmental status of 12 children with persistent pulmonary hypertension of the newborn (PPHN) was examined. All had neonatal documentation of PPHN by echocardiogram, and all were ventilated at least 72 hours. The mean age at follow-up was 20 months (range, 12-28). Five of the 12 subjects were normal at follow-up, three were felt to be suspect but not clearly abnormal, and four had neurodevelopmental abnormalities, including three with sensorineural hearing impairment (25 per cent incidence in this study). These findings represent a concerning frequency of neurodevelopmental dysfunction and support early routine hearing evaluation in this unique subgroup of neonatal intensive care unit survivors.
Follow-Up Studies↗
A new agenda needed concerning "tragic choices".
Debate regarding the context of decision making on catastrophically ill infants has been focused on process and methodology. An expanded scope of inquiry is needed to increase our understanding of the dilemmas we face.
Attitude↗
Diaphragmatic function during hypoxemia: neonatal and developmental aspects.
The effect of acute hypoxemia on diaphragmatic force output was studied in five young (age 4-8 days, wt 1.3-2.2 kg) and five older (age 16-19 days, wt 2.8-3.3 kg), anesthetized, spontaneously breathing piglets. Diaphragmatic force output was assessed by analysis of the transdiaphragmatic pressure (Pdi) generated during an occluded inspiratory effort, at end-expiratory lung volume, triggered by supramaximal transvenous stimulation of both phrenic nerves at frequencies of 20, 30, 50, and 100 Hz. During pressure measurements, the piglets were fitted with a rigid plaster cast covering the abdomen and lower third of the chest to ensure a consistency in diaphragmatic shortening during phrenic nerve stimulation. Pdi was measured under base-line conditions [inspired O2 fractional concentration (FIO2) = 0.50] and after 10 min of hypoxemia induced by breathing 12-14% FIO2. Pdi was significantly less than base line during acute hypoxemia at all frequencies of stimulation in both young and older piglets. The decline in the older piglets' Pdi during hypoxemia was significantly greater than that seen in younger piglets. We conclude that acute hypoxemia impairs the capacity of the developing piglet diaphragm to generate force. Furthermore, our data suggest that the young piglet is more resistant to the depressant effects of hypoxemia when compared to its older counterpart.
Age Factors↗
Postnatal changes in transdiaphragmatic pressure in piglets.
We examined diaphragmatic force output in 25 anesthetized piglets ranging in postnatal age from 4 to 21 days (weight 1.3-4.0 kg) in order to determine whether the diaphragm produces greater force output with maturation for a given level of neural input. Transdiaphragmatic pressure (Pdi) served as our index of diaphragmatic force output and was measured during "supramaximal" transvenous phrenic nerve stimulation at 100 Hz in order to control neural drive. Mean Pdi was 53 +/- 17 cm H2O and ranged from a minimum of 29 cm H2O to a maximum of 83 cm H2O. A significant positive correlation between Pdi and postnatal age was observed (r = 0.79, p less than 0.001). In addition, positive correlations were noted between Pdi and total body weight (r = 0.73, p less than 0.001) and Pdi and diaphragmatic wet weight (r = 0.77, p less than 0.001). The voltage needed to stimulate the phrenic nerves "supramaximally" did not correlate with postnatal age (r = 0.02, p = 0.16). We conclude that a developmental pattern of increasing Pdi with increasing postnatal age, total body weight, and diaphragmatic wet weight exists in piglets and occurs within the context of a controlled level of neural drive.
Animals↗
Severe nonimmune fetal hydrops with fetal survival. A case report.
A case of severe idiopathic nonimmune fetal hydrops spontaneously resolved after delivery with only basic supportive therapy. This case emphasizes that natural occurrences occasionally are responsible for successes attributed to invasive intrauterine treatments.
Adult↗
Changes in lung volume and deflation stability in hyaline membrane disease.
Total lung capacity (TLC), inspiratory capacity, functional residual capacity, and deflation stability of prematurely delivered Macaca nemestrina primates were measured serially during development of, and recovery from, hyaline membrane disease (HMD) to relate changes in lung volumes to changes in deflation stability. Gestational age-matched primates that did not develop HMD served as controls. TLC, measured by N2 washout, fell at 2-12 h of age (P less than 0.0001) in animals with HMD and remained lower than controls for at least 48 h (P less than 0.005). However, deflation stability, defined as the fraction of TLC remaining upon deflation to 10 cm H2O, improved from 2 to 12 h of age (P less than 0.001). Postmortem studies confirm the measurements of TLC and deflation stability and provide evidence that interstitial thickening and obstruction of air spaces with debris may be partially responsible for the observed changes in TLC in primates that develop HMD. It has been assumed that TLC is reduced in HMD because of atelectasis from elevated alveolar surface tension, but the sequential measurements in these animals suggest that other mechanisms also contribute.
Animals↗
Persistent pulmonary hypertension in a very low birthweight preterm infant.
Persistent pulmonary hypertension of the neonate (PPHN) characteristically is seen in full-term or postterm infants. Occasionally, PPHN complicates the course of hyaline membrane disease in preterm infants. This report documents the unusual occurrence of PPHN in a preterm very low birthweight infant without apparent pulmonary parenchymal disease.
Alprostadil↗
Pulmonary edema associated with upper airway obstruction.
We retrospectively surveyed records of 153 patients with croup or epiglottitis. Thirty-four children required intubation of the trachea to relieve upper airway obstruction. In those requiring intubation, pulmonary edema occurred in four (12%) of 34. Review of 17 previously reported cases, along with our patients, demonstrated that onset of pulmonary edema due to upper airway obstruction usually follows intubation. A PaO2 below 50 mm Hg is observed in 38% and pneumothorax in 24% of all reported cases. Supplemental oxygen, positive end-expiratory pressure, mechanical ventilation, and chest tube drainage have prevented death despite these life-threatening complications.
Adult↗
Decision making on critically ill infants by parents.
Two schools of thought regarding participation in decision making on critically ill infants have developed. One school places the responsibility for decision making in the hands of a forum, and the other school places it in the hands of the parent and physician. These two approaches are examined and contrasted. From the dialectic developed, there emerges a third alternative that potentially encompasses the needs of all involved participants more fully, especially when participants find themselves confronted with difficult decisions and still unresolved conflict. This third approach is the matrix paradigm.
Decision Making↗
Bilirubin 20 mg/dL = vigintiphobia.
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Bilirubin↗
Diaphragmatic pressures in piglets: transvenous versus direct phrenic nerve stimulation.
We examined transdiaphragmatic pressure (Pdi) generation during both direct (DPNS) and transvenous (TVPNS) modes of phrenic nerve stimulation in anesthetized piglets of varying postnatal age. Pdi measurements during TVPNS were not statistically different from those obtained during DPNS (p greater than 0.10). Furthermore, a good correlation (r = 0.98, p less than 0.001) was obtained when the mean Pdi measurements obtained by both methods were compared. We conclude that TVPNS can be used in lieu of DPNS to generate Pdi. Furthermore, our data suggest that this technique can be used to study the effects of various experimental manipulations on diaphragmatic force output within a developmental context.
Age Factors↗