Nonsurgical management of renovascular hypertension in the neonate.

Over an 18-month period nine infants in a neonatal intensive care unit developed hypertension (blood pressure, 115/88 to 280/140 mm Hg) at 2 to 45 days of age. Eight of the nine infants had indwelling umbilical artery catheters prior to onset of hypertension; six of the nine infants had evidence of a patent ductus arteriosus. Peripheral plasma renin activity was greater than 300 ng/ml/3 hr in six of eight infants. Angiograms were abnormal in six of seven infants and computerized renal scans were abnormal in all nine infants. One infant had congenital renal artery stenosis. Eight of nine infants had evidence of unilateral or bilateral renal artery thrombi which were felt to have emanated from an umbilical artery catheter or a ductus arteriosus. Hypertension in all infants was successfully controlled medically (follow-up of 3 to 27 months; mean, 14.4 months). Blood pressures remained normal when medication was discontinued. In our experience, neonatal renovascular hypertension is no longer uncommon, responds to aggressive medical management, and rarely requires early nephrectomy. Neonatal renovascular hypertension was usually associated with umbilical artery catheters positioned above the level of the renal arteries.

Tracheal asiration and its clinical correlates in the diagnosis of congenital pneumonia.

Tracheal aspirates were obtained from 320 newborns with respiratory distress and one or more perinatal risk factors for infection. Samples were obtained before 8 hours of age, either by direct aspiration or immediately following intubation. Twenty-five infants had bacteria present in the aspirate smear. In each case a pure culture of the organism suspected by smear morphology was grown. The same organism was isolated from blood in 14 of the 25 newborns suspected of having pneumonia. The remaining 11 infants had clinical courses, depressed mature neutrophil counts, and elevated band to total neutrophil ratios consistent with bacterial infection. Twenty-five infants without bacteria in the tracheal aspirate smear were randomly selected as a comparison group. Three of these infants had positive blood cultures, and one of the three also grew the same organism from the tracheal aspirate. The chest radiograph was abnormal in all infants but did not discriminate patients with or without pneumonia. We conclude that examination of the tracheal aspirate obtained within the first 8 hours of age is helpful in the early diagnosis of congenital pneumonia.

Effect of heparinization of fluids infused through an umbilical artery catheter on catheter patency and frequency of complications.

Heparinization of fluids (1 unit/ml) infused through an umbilical artery catheter (UAC) was efficacious in prolonging catheter patency in a double-blind, randomized, controlled clinical study. On the basis of life-table analysis, the half-life of catheter function was seven days in the heparinized group as compared with just over two days in the nonheparinized group (P less than .01). UAC occlusion occurred in 4 of 32 patients in the heparinized and 19 of 30 in the nonheparinized group (chi 2 = 17.6, P less than .01). Blood transfusions, number of arterial blood gases drawn through the UACs, and fluid infusion rates were not related to catheter occlusion. Heparinization of the UAC infusion did not alter the partial thromboplastin time or the incidence of catheter-related thromboembolic phenomena in the extremities. Heparinization of fluids infused through a UAC appears to be useful in the care of critically ill neonates.

Thrombotic complications of umbilical artery catheters: A clinical and radiographic study.

Catheterization of the aorta via the umbilical artery provides a convenient route for monitoring arterial blood pressure, for obtaining blood specimens for measurement of blood gas tensions and chemistries, and for the infusion of fluids and pharmacologic preparations in sick newborn infants. Use of this technique may be accompanied by a number of complications of which thrombotic phenomena are the most common. Twenty-three of 98 (24%) newborn infants undergoing umbilical artery catheterization were found to have thrombotic complication determined by aortography. No correlation was present between the duration of time that the umbilical artery catheters were in place and the occurrence of thrombotic complications. From paired aortographic or aortographic and autopsy studies in 24 patients, it was concluded that if a thrombotic complication did not occur early, none was likely to occur subsequently. One patient was considered to have died as a direct result of a thrombotic complication. Aortography is a safe, simple, and reliable technique for the early detection of thrombotic complications of umbilical artery catheters. Umbilical artery catheterization is not without risk and careful selection of patients for this procedure is indicated.

Effect of pulmonary artery distention on systemic vascular resistance in newborn lambs.

Balloon distention of the left pulmonary artery (PA) was produced in 14 lambs (aged 1 to 3 days) to assess whether an increase in systemic vascular resistance results from such distention. The lambs were anesthetized with chloralose and instrumented to enable measurement of systemic blood flow, PA pressure, aortic pressure, heart rate and right atrial pressure. PA distention resulted in an increase in systemic vascular resistance and aortic pressure (p less than 0.05). This result was probably due to a systemic vasoconstrictor response, since systemic blood flow and right atrial pressure did not change significantly. Limited trials using autonomic blocking agents suggested that the response is either a reflex under autonomic control or a response to humoral release of alpha-adrenergic substances. In conclusion, some interdependence appears to exist between the systemic and pulmonary vascular beds. It is postulated that such changes may be important in fetal life when they may affect redistribution of cardiac output during adaptation to hypoxemia.

Increased systemic vascular resistance in neonates with pulmonary hypertension.

The time necessary for aortic diastolic pressure to decrease to 50 percent of an initially selected value after dissipation of the dicrotic notch (T 1/2) was determined in newborn infants with and without pulmonary hypertension. The mean T 1/2 was 671 +/- 167 msec in seven infants with clinical evidence of pulmonary hypertension and documented right to left ductus arteriosus shunting; 849 +/- 243 msec in nine infants with clinical evidence of pulmonary hypertension but no documented right to left ductus arteriosus shunting; and 457 +/- 66 msec in eight infants with hyaline membrane disease and no clinical evidence of pulmonary hypertension or a patent ductus arteriosus. The mean T 1/2 values in the former two groups were significantly different from that in the group with no pulmonary hypertension (P less than 0.01). An evaluation of factors affecting T 1/2 leads to the conclusion that the patients with pulmonary hypertension had increased systemic vascular resistance as well. This finding has important diagnostic, etiologic and therapeutic implications.

Role of arterial design on pulse wave reflection in a fractal pulmonary network.

A novel interpretation of pulmonary arterial input impedance was evaluated for the lung as a fractal vascular network. We hypothesized that local sources of reflection introduce trends of global reflection into the input impedance spectra. These trends are related to the network topology, geometry, and design according to Rb = Rdx, where Rb is the branching ratio, Rd is the diameter ratio, and x is the fractal dimension quantifying design. Simulations using values of Rd and x, which were derived morphometrically, confirmed two patterns of global reflection: a continuous trend attributed to a single effective site of reflection caused by frequency-dependent sources of impedance contrast and a discrete trend arising from a longitudinal distribution of frequency-independent sources of reflection. The continuous trend depended only on the network parameter Rd, whereas the discrete trend depended on Rd and x. Our results indicate that the impedance-matching properties of a deterministic pulmonary fractal network encode arterial geometry and topology via function and that typical values of Rd and x for the pulmonary circulation facilitate shear stress amplification in its peripheral vessels. Thus, inasmuch as shear forces may be involved in the endothelial mechanisms for pathological, or physiological, vascular remodeling, broadband input impedance analysis may reveal interactions between network organization and vascular function.

Risk factors for bacteriuria in men.

OBJECTIVE: To identify risk factors for bacteriuria in a selected group of institutionalized men. METHODS: A total of 99 men, mean age seventy-one years, range forty-eight to one hundred four years, living in a nursing home were evaluated for diagnoses of benign prostatic hyperplasia (BPH) and diabetes mellitus (DM), symptoms of bladder outlet obstruction, and postvoid residual urine volume (PVR). At the time of evaluation urine cultures were performed for all subjects. Urinalyses had been performed in all men within the two years prior to initiation of the study. Residents unable to give informed consent, with a history of cancer of the prostate or bladder, previous urethral or prostate surgery, or inability to void in the standing position were excluded. RESULTS: Prior to or during the study 30 residents had bacteriuria, which was not correlated with age, PVR, previous diagnoses of BPH or DM, or with obstructive or irritative urinary symptoms consistent with bladder outlet obstruction. CONCLUSIONS: Competent, institutionalized residents with higher functional levels meeting the inclusion criteria were not at a high risk of bacteriuria. The concept that increased PVR per se predisposes to bacteriuria cannot be substantiated.

Intratracheal administration of pulmonary vasodilator agents.

We compared intravenous and intratracheal administration of histamine (0.4 and 1.6 micrograms/kg, respectively) and nitroglycerin (5.0 and 20.0 micrograms/kg, respectively) in seven hypoxemic 2 week old lambs, during right lung only perfusion, to see if intratracheal administration could limit their vasodilator action to the pulmonary vessels. The hemodynamic variables: pulmonary artery pressure (Ppa), left atrial pressure (Pla), pulmonary blood flow per kilogram (Q/kg), and aortic pressure (Pao) were measured at baseline and in each experimental state, then pulmonary vascular resistance (PVR) and systemic vascular input resistance (SVR) were determined. We found that intravenous histamine showed some pulmonary vasodilator selectivity in that it caused a 19% decrease of Ppa from baseline (P less than 0.002), a 23% decrease of PVR from baseline (P less than 0.002), and an 8% decrease of SVR from baseline (P less than 0.05). Intratracheal histamine produced smaller effects, decreasing Ppa by 11% from baseline (P less than 0.02), and PVR by 14% from baseline (P less than 0.02), while SVR was unaffected. Intravenous nitroglycerin decreased cardiac output by 16% from baseline (P less than 0.02), and also decreased SVR by 8% while producing a small increase in PVR. Intratracheal nitroglycerin caused a similar 17% (P less than 0.01) decrease in cardiac output, and again an increased PVR but a decreased SVR. This study confirms that histamine has some intrinsic pulmonary vasodilator selectivity. Furthermore, the data suggest that intratracheal administration may accentuate pulmonary selectivity by lessening systemic effects. Nitroglycerin, on the other hand, had untoward hemodynamic effects in the presence of hypoxia.

Irreversibility of birth-related changes in the pulmonary circulation.

We hypothesized that establishing conditions of hypoxia and fluid filling of the airways in lungs of newborns would reproduce the high levels of pulmonary vascular resistance (PVR) observed in the fetal state. We assessed the hemodynamics of the left pulmonary circulation of 1- to 3-day-old lambs during a variety of airway states while attempting to reestablish fetal conditions. Eleven animals were studied during both normoxemia and hypoxemia in a baseline airway state with a positive end-expiratory pressure (PEEP) of 4 cm H2O, and in experimental airway states, of atelectasis, and fluid filling to 15 and 30 mL/kg and with PEEP of 12 cm H2O. PVR increased while pulmonary blood flow decreased with all airway state changes as compared to baseline, suggesting a passive mechanism for these changes. With the addition of hypoxemia there was a further increase in PVR in all states accompanied by an increase in pulmonary blood flow, indicating that active vasoconstriction was responsible for the increase in PVR. The combined effects of hypoxemia and fluid filling, designed to approximate the fetal state, increased PVR to only 20-30% of fetal values. Thus, additional factors appear to be important in maintaining the high PVR of the fetal state. We speculate that ventilation of the lungs at birth irreversibly alters these factors.

Normocarbic hyperventilation fails to induce pulmonary vasodilation.

The pulmonary vasodilator effect of increased rate of mechanical ventilation, with and without respiratory alkalosis, was studied in chronically instrumented newborn lambs. Pulmonary hypertension was first induced by ventilating with a hypoxic gas mixture. Subsequent respiratory alkalosis caused significant decreases in pulmonary arterial pressure and pulmonary vascular resistance. When normocarbia was re-established by adding carbon dioxide to the inspired gas, with the ventilator rate being held constant, the pressure and resistance returned to the baseline hypertensive state. Therefore, mechanical factors, either direct or indirect, appear to be of minor importance in the mechanism of pulmonary vasodilation secondary to frequency-induced hyperventilation.

Effect of pulmonary hypertension on lung compliance in newborn lambs.

We studied the effects of increased pulmonary arterial pressure and vascular resistance on lung compliance in 12 anesthetized newborn lambs. Lung compliance was unaffected by large changes in pulmonary artery pressure and pulmonary vascular resistance (80% increase) that were induced by either hypoxia or acidosis. We conclude that contraction of the pulmonary vascular smooth muscle in normal newborn lambs does not affect the stiffness of the lung in the parenchymal regions undergoing volume change during ventilation.

Percutaneous and surgical placement of fine silicone elastomer central catheters in high-risk newborns.

Percutaneous insertion of fine silicone elastomer catheters (0.6 millimeters outside diameter) have been used for central parenteral nutrition of very low birth weight and other high risk infants. Because peripheral venous access can be limited in the newborn, we report the previously undescribed surgical cannulation of the superficial arm veins with this catheter, and compare our experience with this technique and the percutaneous method in neonates. A central catheter position was attained in 88% of surgical (38 of 43) and 74% of percutaneous (17 of 23) cannulations. The two groups did not differ in birth weight or gestational age. The mean duration of catheterization was similar in the two groups (combined means = 21.8 +/- 2.3 days SEM). There was no difference in weight gain (combined means = 16.9 +/- 1.0 grams SEM per day) or head growth (combined means = 1.1 +/- 0.1 millimeters per day) between the groups and these rates approximated known fetal growth rates for our mean gestational age. Disseminated candidiasis, in a 770-gram infant with thymic hypoplasia, caused the only systemic infection and death among our 49 patients. The most commonly encountered problem was catheter occlusion secondary to a blood clot at the tip of these fine catheters (8 of 55). No thromboembolic events were recognized, and minor complications were not different with the two techniques. Surgical cannulation of the superficial arm veins offers a safe alternative to percutaneous central silicone elastomer catheter placement if superficial venous access is not available. Both methods provided early, adequate parenteral nutrition without excessive fluid intake in our high-risk infants, and undoubtedly contributed to a favorable neonatal outcome.

Brain injury and protective effects of hypothermia using triphenyltetrazolium chloride in neonatal rat.

Colorless 2,3,5-triphenyltetrazolium chloride (TTC) is reduced by enzymes in functioning mitochondria to a red-colored compound, and has been used to differentiate areas of viable tissue from areas of infarction in adult animals. TTC was used to study the central nervous system protective effects of hypothermia on the neonatal rat exposed to hypoxia and ischemia. The effect of hypothermia on survival and weight gain was also determined. Seven-day-old Wistar rats with right carotid artery ligation were exposed to 3 hours of 8% oxygen and maintained at either 37 degrees C (n = 22) or 30 degrees C (n = 18). The survivors were sacrificed 2 days later and brain slices exposed to TTC. These slices were photographed and the percentage of damage to the right brain was estimated gravimetrically from the stained and unstained areas of enlarged images. The mean weight gains were 4.2 +/- 1.2 gm in the 30 degrees C group and -1.0 +/- 2.8 gm in the 37 degrees C group (P < .001). The survival in the 37 degrees C group was 77% and in the 30 degrees C group 100% (P < .025). The mean percentage damage to the right side of the brain in the 37 degrees C group was 45.5% (range: 0-87.5%); there was no detectable damage in any of the 30 degrees C group pups (P < .0001). In our study, TTC proved to be a rapid and simple method for assessing central nervous system injury in the neonatal rat. This study also confirms that moderate hypothermia is protective against hypoxic-ischemic brain injury.

Computerized axial tomography of the brain in neonates and young infants.

Twenty critically ill infants with abnormal head growth and/or seizures underwent CAT of the brain. Signs of birth asphyxia or respiratory distress were present in all. Six out of ten infants with abnormal size of the head had abnormal CAT scans. Nine out of ten infants with seizures had abnormal scans. Abnormalities included hydrocephalus, intraventricular hemorrhage, cerebral edema, subarachnoid hemorrhage and porencephaly. Six infants required neurosurgical procedures. Development at two to 15 months of age in the 19 surviving infants was normal in nine, suspect in eight, and severely delayed in two patients. Until the prognosis of the various CNS disorders discussed is clearly defined, aggressive management appears indicated.

Prognosis of intracranial hemnorrhage in neonates.

Eleven of 21 infants with intracranial hemorrhage documented by computerized axial tomography survived and have had serial developmental assessments. Six of nine infants with intraventricular hemorrhage (IVH) are developing normally, as is one of two infants with isolated subtentorial hemorrhage. According to our system for grading the severity of IVH, severe IVH correlated best with mortality and less well with developmental delay in survivors. Contrary to past impressions, IVH, even if severe, does not uniformly lead to a poor developmental outcome in surviving infants.

Adrenal abscess: complication of supportive therapy of adrenal hemorrhage in the newborn.

A case of adrenal hemorrhage treated supportively resulted in an adrenal abscess. Onset of fever after a nonoperative approach should lead to consideration of surgical exploration for an adrenal abscess.

Gastroschisis and Hirschsprung's disease: a rare combination.

The authors report on a neonate with gastroschisis repaired at birth who later had abdominal distension, emesis, feeding intolerance, and an abnormal stooling pattern. Total colon and partial small bowel aganglionosis (TCAS), or Hirschsprung's disease, was diagnosed subsequently. This is the first report of this combination of gastrointestinal anomalies. J Pediatr Surg 36:638-640.

Hemodynamic effects of positive end-expiratory pressure during partial liquid ventilation in newborn lambs.

BACKGROUND/PURPOSE: The aim of this study was to compare the effect of positive end-expiratory pressure (PEEP) application on hemodynamics, lung mechanics, and oxygenation in the intact newborn lung during conventional ventilation (CV) and partial liquid ventilation (PLV) at functional residual capacity (FRC). CV or PLV modes of ventilation do not affect hemodynamics nor the optimum PEEP for oxygenation. METHODS: Seven newborn lambs (1 to 3 days old) were instrumented to measure pulmonary hemodynamics and airway mechanics. Each lamb was used as their own control to compare different modes of ventilation (CV followed by PLV) under graded variations of PEEP (4, 8, 12, and 16 cm H(2)O) on the influence on pulmonary blood flow and pulmonary vascular resistance. RESULTS: There was a significant drop in pulmonary blood flow (PBF) from baseline (PEEP of 4 cm H(2)O on CV, 1,229 +/- 377 mL/min) in both modes of ventilation on a PEEP of 16 cm H(2)O (CV, 750 +/- 318 mL/min v PLV, 926 +/- 396 mL/min, respectively; P <.05). Peak inspiratory pressure (PIP) was higher on PLV at PEEP states of 4 cm H(2)O (16.5 +/- 1.3 cm H(2)O to 10.6 +/- 2.1 cm H(2)O; P <.05) and 8 cm H(2)O (18.8 +/- 2.2 cm H(2)O to 15.1 +/- 2.6 cm H(2)O; P <.05) when compared with CV. Conversely, PIP required to maintain the pCO(2) was lower on PLV at PEEP states of 12 (22.5 +/- 3.6 cm H(2)O to 24.2 +/- 3.8 cm H(2)O; P <.05) and 16 cm H(2)O (27.0 +/- 1.6 cm H(2)O to 34.0 +/- 5.9 cm H(2)O; P <.05). CONCLUSIONS: Hemodynamically, CO is impaired at a PEEP above 12 cm H(2)O in intact lungs. PFC at FRC does provide an advantage in lung mechanics more than 10 to 12 cm H(2)O of PEEP by decreasing the amount PIP needed to achieve the similar levels of gas exchange and minute ventilation, implying a reduced risk for barotrauma with chronic ventilation. Thus, selection of the appropriate level of PEEP appears to be important if PLV is to be utilized at FRC. The best strategy for PLV, including the selection of PEEP, remains to be determined.

Intracranial pressure and cerebral perfusion pressure in clinically normal equine neonates.

Intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were determined in 8 clinically normal neonatal foals. After the foals oriented themselves and nursed the mares, they were sedated as necessary, and local anesthesia was provided for making the skin incisions. Using a technique similar to that used in human beings, an indwelling subdural catheter was placed to measure ICP. Carotid artery catheterization was used to measure arterial blood pressure. Cerebral perfusion pressure was calculated as the difference between mean arterial blood pressure and ICP. Intracranial pressure and CPP readings were taken twice during each 24-hour period, starting at 6 hours of age and continuing through 72 hours of age. Mean (+/- SD) ICP were 5.83 +/- 1.82, 8.81 +/- 2.06, and 9.55 +/- 1.55 mm of Hg (range, 2 to 15 mm of Hg), and mean CPP were 80.19 +/- 10.34, 75.30 +/- 10.86, and 76.80 +/- 12.59 mm of Hg (range, 50 to 109 mm of Hg) for each of the first three 24-hour periods after birth, respectively. All 8 foals had physical and neurologic examinations, CSF analysis, and computerized axial tomography evaluations. The foals manifested normal behavior during the interval of measurements, and adverse effects of the procedure were not detected during the monitoring period. Establishment of normal values for ICP and CPP are important to clinicians who have the opportunity to apply this technique for monitoring and evaluating neonatal foals with signs of CNS dysfunction.