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expiratory ratio (I:E) and airway pressure wave form during mechanical ventilation: The significance of mean airway pressure
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Abstracts
infants of Rh +ve mothers were screened by enzyme and AutoAnalyzer methods at birth and 6 weeks; 65 again at 3 months and 49 again at 6 to 12 months after delivery. None had evidence of Rh-immunization. One infant, enzyme-negative, AutoAnalyzer-positive at 8 weeks, was AutoAnalyzer negative at 12 months. (Antibody specificity at 8 weeks was not determined). Maternal fetal Rh-immunization is a rare occurrence. Rhimmune globulin should not be given to Rh - v e infants born of Rh + v e mothers. DISCUSSION Dr. Tsang: If samples are obtained on day 2 in the infant, is it possible that transfused maternal cells might be eliminated by the infant? Dr. Bowman: This is unlikely since the infant generally does not produce isohemagglutinins. Cord blood contamination by maternal blood is a difficult problem to overcome. Although some studies suggest maternal-fetal transfusion of 30-40 ml (12% of blood volume), this seems unlikely and may be related to contamination. Dr. llall (Kansas City): What is the dose-response relationship, and were there adverse effects on the infant? Dr. Bowman: When 300pg Rh-immunoglobulin was given im at 28 and 34 weeks' gestation to mothers, 35% of inffints had positive direct Coombs tests, although they had normal Hgb and bilirubins. With a single dose at 28 weeks, no infants had positive Coombs tests and the dose is felt to be effective in prophylaxis.
The effect of variations in inspiratory/expiratoly ratio (I:E) and airway pressure wave form during mechanical ventilation: The significance of mean airwa), pressure S. J. Boros, St. Paul, Minn. Ten.neonates with severe lung disease were studied during mechanical ventilation with volume preset infant ventilators, using different I:E ratios (1:4; !: 1) and different airway pressure 9,,.'ave forms (sawtooth wave; square wave). Although tidal volumes, respiratory rates, positive end expiratory pressure (PEEP) remained constant, I:E ratios were increased from !:4 to i:1, first by decreasing inspiratory flow rate, producing a sawtooth pressure wave, and again by using an inspiratory hold mechanism that produced an inspiratory plateau or square pressure wave. For each I:E ratio: pressure wave combination, Pao:, Paco:. pH, peak inspiratory pressure, and mean airway pressure (MAP) were measured and compared. In all patients, optimum oxygenation and ventilation occurred with the I:E ratio/pressure wave combination that produced the maximum MAP. In all patients, increases in oxygenation appeared directly related to increases in MAP. No adverse affects on arterial blood pressure due to the application of high MAP were observed. DISCUSSION Dr. Erenberg: What kind of infants were these? Dr. Boros: There "'ere 8 RDS infants; the rest had meconium aspriation. All were critically ill. Dr. Chernick: Were there changes in blood pressure?
The Journal of Pediatrics August 1978
Dr. Boros: Blood pressure and pulse pressure measurements were unchanged. Dr. Hunt: These studies confirm the lamb studies, llow would MAP relate to barotrauma? Dr. Boros: In the retrospective studies of Dr. O. Reynolds, decreased inspiratory pressure ( < 25 cm H:O) and increased inspiratory time seemed to have better results. Dr. Rigatto (Winnipeg): We use the recommendations of Dr. O.-Reynolds and we have fewer problems and no hypotension. The end expiratory pressure is high in )'our studies; is that the best combination for optimal oxygenation? Dr. Boros: Better oxygenation can be achieved by increased peak inspiratory pressure, increased PEEP, or increased stretch inspiratory pressure at low peak inspiratory pressure. Dr. Chernick: Oxygenation Can be achieved by rapid ventilation at 180/min, and MAP need not be changed at all.
Renal calcifications: A complication of long-term high-dose fiu'osemide K. ilufnagle,* D. Penn,* and P. Williams, Royal Oak, Mich. Over the past 3,'ear, four infants developed renal calcifications while on long-term furosemide therapy. The infants received furosemide initially for control of the patent ductus arteriosus and later for bronchopulmonary dysplasia. Doses ranged from 2-18 mg/kg/day for at least 27 days. The calcifications were noted on flat plates of the abdomen at 1-3 months of age. The radiologic findings varied from isolated stones to nephrocalcinosis and staghorn calculi. Serum calcium was normal in all four; one had an elevated serum phosphorus. All had a component of metabolic alkalosis with urinary ptl in 6.5-7.0 range. Three infants had markedly elevated 24-hour excretion of calcium when on furosemide; 38-50 mg Ca/24 hours or 15-20 mg/ kg/day. (Our normal value is 2-4 mg Ca/kg/day.) All had amorphous crystals and two had calcium oxalate crystals in the urine. Analysis of the stones found at autopsy showed calcium, oxalate, and phosphate. Two infants developed sepsis from urinary tract infections after the stone formation. Furosemide was switched to chlorothiazide in two infants and a radiographic diminution in the stones was seen in both. On~ had total resolution, later confirmed by autopsy. Furosemide therapy, at doses of at least 2 mg/kg/day for one month, can be associated with renal calcifications. A possible mechanism for the stone formation is the hypercalciuria and alkaline urine produced by furosemide therapy. This complication should be looked for in infants on high-dose long-term furosemide treatment. DISCUSSION Dr. Tsang: What numbers of infa,,ts in )our nursery receive intensive furosemide therapy? Dr. tlufnagle: There are 400 admissions each year; about 12 infants "'ith severe lung disease are on long-term furosemide therapy. Dr. Erenberg: Infants on long-term furosemide referred to us have had metabolic alkalosis. Is this a factor in the renal calcification? Dr. Hufnagle: The infants had metabolic alkalosis ( + 2 0 to 30 mEq/l) and hypochloremia, and this could be important. Dr. Chesney: The calcifications could be related to shock kidneys. Dr. ttillman: Were there bone changes?
Abstracts
infants of Rh +ve mothers were screened by enzyme and AutoAnalyzer methods at birth and 6 weeks; 65 again at 3 months and 49 again at 6 to 12 months after delivery. None had evidence of Rh-immunization. One infant, enzyme-negative, AutoAnalyzer-positive at 8 weeks, was AutoAnalyzer negative at 12 months. (Antibody specificity at 8 weeks was not determined). Maternal fetal Rh-immunization is a rare occurrence. Rhimmune globulin should not be given to Rh - v e infants born of Rh + v e mothers. DISCUSSION Dr. Tsang: If samples are obtained on day 2 in the infant, is it possible that transfused maternal cells might be eliminated by the infant? Dr. Bowman: This is unlikely since the infant generally does not produce isohemagglutinins. Cord blood contamination by maternal blood is a difficult problem to overcome. Although some studies suggest maternal-fetal transfusion of 30-40 ml (12% of blood volume), this seems unlikely and may be related to contamination. Dr. llall (Kansas City): What is the dose-response relationship, and were there adverse effects on the infant? Dr. Bowman: When 300pg Rh-immunoglobulin was given im at 28 and 34 weeks' gestation to mothers, 35% of inffints had positive direct Coombs tests, although they had normal Hgb and bilirubins. With a single dose at 28 weeks, no infants had positive Coombs tests and the dose is felt to be effective in prophylaxis.
The effect of variations in inspiratory/expiratoly ratio (I:E) and airway pressure wave form during mechanical ventilation: The significance of mean airwa), pressure S. J. Boros, St. Paul, Minn. Ten.neonates with severe lung disease were studied during mechanical ventilation with volume preset infant ventilators, using different I:E ratios (1:4; !: 1) and different airway pressure 9,,.'ave forms (sawtooth wave; square wave). Although tidal volumes, respiratory rates, positive end expiratory pressure (PEEP) remained constant, I:E ratios were increased from !:4 to i:1, first by decreasing inspiratory flow rate, producing a sawtooth pressure wave, and again by using an inspiratory hold mechanism that produced an inspiratory plateau or square pressure wave. For each I:E ratio: pressure wave combination, Pao:, Paco:. pH, peak inspiratory pressure, and mean airway pressure (MAP) were measured and compared. In all patients, optimum oxygenation and ventilation occurred with the I:E ratio/pressure wave combination that produced the maximum MAP. In all patients, increases in oxygenation appeared directly related to increases in MAP. No adverse affects on arterial blood pressure due to the application of high MAP were observed. DISCUSSION Dr. Erenberg: What kind of infants were these? Dr. Boros: There "'ere 8 RDS infants; the rest had meconium aspriation. All were critically ill. Dr. Chernick: Were there changes in blood pressure?
The Journal of Pediatrics August 1978
Dr. Boros: Blood pressure and pulse pressure measurements were unchanged. Dr. Hunt: These studies confirm the lamb studies, llow would MAP relate to barotrauma? Dr. Boros: In the retrospective studies of Dr. O. Reynolds, decreased inspiratory pressure ( < 25 cm H:O) and increased inspiratory time seemed to have better results. Dr. Rigatto (Winnipeg): We use the recommendations of Dr. O.-Reynolds and we have fewer problems and no hypotension. The end expiratory pressure is high in )'our studies; is that the best combination for optimal oxygenation? Dr. Boros: Better oxygenation can be achieved by increased peak inspiratory pressure, increased PEEP, or increased stretch inspiratory pressure at low peak inspiratory pressure. Dr. Chernick: Oxygenation Can be achieved by rapid ventilation at 180/min, and MAP need not be changed at all.
Renal calcifications: A complication of long-term high-dose fiu'osemide K. ilufnagle,* D. Penn,* and P. Williams, Royal Oak, Mich. Over the past 3,'ear, four infants developed renal calcifications while on long-term furosemide therapy. The infants received furosemide initially for control of the patent ductus arteriosus and later for bronchopulmonary dysplasia. Doses ranged from 2-18 mg/kg/day for at least 27 days. The calcifications were noted on flat plates of the abdomen at 1-3 months of age. The radiologic findings varied from isolated stones to nephrocalcinosis and staghorn calculi. Serum calcium was normal in all four; one had an elevated serum phosphorus. All had a component of metabolic alkalosis with urinary ptl in 6.5-7.0 range. Three infants had markedly elevated 24-hour excretion of calcium when on furosemide; 38-50 mg Ca/24 hours or 15-20 mg/ kg/day. (Our normal value is 2-4 mg Ca/kg/day.) All had amorphous crystals and two had calcium oxalate crystals in the urine. Analysis of the stones found at autopsy showed calcium, oxalate, and phosphate. Two infants developed sepsis from urinary tract infections after the stone formation. Furosemide was switched to chlorothiazide in two infants and a radiographic diminution in the stones was seen in both. On~ had total resolution, later confirmed by autopsy. Furosemide therapy, at doses of at least 2 mg/kg/day for one month, can be associated with renal calcifications. A possible mechanism for the stone formation is the hypercalciuria and alkaline urine produced by furosemide therapy. This complication should be looked for in infants on high-dose long-term furosemide treatment. DISCUSSION Dr. Tsang: What numbers of infa,,ts in )our nursery receive intensive furosemide therapy? Dr. tlufnagle: There are 400 admissions each year; about 12 infants "'ith severe lung disease are on long-term furosemide therapy. Dr. Erenberg: Infants on long-term furosemide referred to us have had metabolic alkalosis. Is this a factor in the renal calcification? Dr. Hufnagle: The infants had metabolic alkalosis ( + 2 0 to 30 mEq/l) and hypochloremia, and this could be important. Dr. Chesney: The calcifications could be related to shock kidneys. Dr. ttillman: Were there bone changes?