A multicenter controlled trial of fetal pulse oximetry in the intrapartum management of nonreassuring fetal heart rate patterns

OBJECTIVE

Recent developments permit the use of pulse oximetry to evaluate fetal oxygenation in labor. We tested the hypothesis that the addition of fetal pulse oximetry in the evaluation of abnormal fetal heart rate patterns in labor improves the accuracy of fetal assessment and allows safe reduction of cesarean deliveries performed because of nonreassuring fetal status.

STUDY DESIGN

A randomized, controlled trial was conducted concurrently in 9 centers. The patients had term pregnancies and were in active labor when abnormal fetal heart rate patterns developed. The patients were randomized to electronic fetal heart rate monitoring alone (control group) or to the combination of electronic fetal monitoring and continuous fetal pulse oximetry (study group). The primary outcome was a reduction in cesarean deliveries for nonreassuring fetal status as a measure of improved accuracy of assessment of fetal oxygenation.

RESULTS

A total of 1010 patients were randomized, 502 to the control group and 508 to the study group. There was a reduction of >50% in the number of cesarean deliveries performed because of nonreassuring fetal status in the study group (study, 4. 5%; vs. control, 10.2%; P =.007). However, there was no net difference in overall cesarean delivery rates (study, n = 147 [29%]; vs. control, 130 [26%]; P = .49) because of an increase in cesarean deliveries performed because of dystocia in the study group. In a blinded partogram analysis 89% of the study patients and 91% of the control patients who had a cesarean delivery because of dystocia met defined criteria for actual dystocia. There was no difference between the 2 groups in adverse maternal or neonatal outcomes. In terms of the operative intervention for nonreassuring fetal status, there was an improvement in both the sensitivity and the specificity for the study group compared with the control group for the end points of metabolic acidosis and need for resuscitation.

CONCLUSION

The study confirmed its primary hypothesis of a safe reduction in cesarean deliveries performed because of nonreassuring fetal status. However, the addition of fetal pulse oximetry did not result in an overall reduction in cesarean deliveries. The increase in cesarean deliveries because of dystocia in the study group did appear to result from a well-documented arrest of labor. Fetal pulse oximetry improved the obstetrician's ability to more appropriately intervene by cesarean or operative vaginal delivery for fetuses who were actually depressed and acidotic. The unexpected increase in operative delivery for dystocia in the study group is of concern and remains to be explained.

Factors influencing outcome of cardiopulmonary resuscitation in children

We evaluated 47 pediatric patients after cardiopulmonary arrest. Patients entered the study with the onset of advanced life support. We followed them until death, or discharge from the hospital, occurred. We identified three groups of patients: long-term survivors, who survived to discharge, short-term survivors, who survived longer than 24 hours after CPR but not until discharge, and nonsurvivors, who died within 24 hours of their arrest. All of the long-term surviving patients were discharged from the hospital without gross neurologic deficit attributable to the arrest or resuscitation effort. Twenty-seven (57%) children were successfully resuscitated. Eighteen (38%) were long term-survivors, while nine (19%) were short-term survivors. Favorable outcome is associated with the following factors: inhospital arrest, extreme bradycardia as the presenting arrhythmia, successful resuscitation with only ventilation, oxygen and closed chest massage, and a duration of CPR of less than 15 minutes. Age, sex, and race, as well as pupillary reaction and motor response at the onset of advanced life support, did not correlate with long-term survival.

Epinephrine-halothane interactions in children

Cutaneous infiltration of dilute solutions of epinephrine for hemostasis during halothane anesthesia can result in ventricular dysrhythmias. Our clinical experience, published reports, and a study comparing piglets with adult swine suggest that children may be less susceptible than adults to dysrhythmias under these conditions. We therefore undertook a prospective survey of heart rate and rhythm in halothane-anesthesized children who received subcutaneous epinephrine for hemostasis. Mass spectrometry was used to quantify end-tidal halothane and to avoid hypercarbia. In 83 children anesthesized with halothane, we continuously recorded ECG, heart rate (HR), end-tidal halothane (ETHalo), and carbon dioxide (ETCO2). The surgeons injected 0.4--15.7 micrograms/kg of epinephrine (in saline or 1% lidocaine) to provide hemostasis at a variety of sites. No child developed a ventricular dysrhythmia. One child had self-limited premature atrial contractions (PAC). Sixty-three children had some increase in heart rate after epinephrine injection, while seven increased their HR 15% or more above pre-injection levels. No relation between any increase in HR and epinephrine dosage, ETHalo, ETCO2, physical status, or age was found by multiple linear regression; however, HR was increased significantly in patients receiving epinephrine in head and neck sites other than the palate. The authors conclude that children tolerate higher doses of subcutaneous epinephrine than adults during halothane anesthesia. The arrhythmogenic dose of epinephrine in children receiving halothane has yet to be determined, but at least 10 micrograms/kg of epinephrine infiltration may be used safely in normocarbic and hypocarbic pediatric patients without congenital heart disease. The presence of PAC and tachycardia emphasize the need for continuous ECG monitoring and caution during halothane anesthesia with epinephrine injection.

The heart is under the lower third of the sternum. Implications for external cardiac massage

Current guidelines for cardiopulmonary resuscitation in children state that the heart lies under the midsternum in infancy and descends with age. To verify this statement, we studied 55 patients, aged 1 day to 19 years, including eight premature infants, during either routine chest x-ray films or right-sided heart angiography. Using a Cartesian coordinate system determined by radiopaque markers placed on the chest, and computer digitization, we located the center of each patient's cardiac silhouette and/or right ventricle. Using descriptive statistics, we found that the heart lay under the lower third of the sternum in all age groups. Analysis of variance indicated that there was no significant difference in this location between age groups. These results suggest that recommendations for external cardiac massage in infants and children may need to be revised.

Management of severe pediatric head trauma

Except for prevention, nothing can alter the primary damage to the central nervous system tissues and blood vessels caused by the impact of traumatic forces over a few milli-seconds. However, damage to nervous system tissues secondary to transient reversible brain dysfunction may occur and lead to failure of respiration and circulation. Brain swelling and intracranial hypertension can develop and interfere with oxygen delivery and cellular metabolism of vital central nervous structures. A team approach with simultaneous treatment of the various disorders and recurrent evaluation is the hallmark of successful management.

Open- versus closed-chest cardiac compressions in a canine model of pediatric cardiopulmonary resuscitation

Whether or not the principles of adult resuscitation apply to the pediatric population remains unknown. In order to study this issue, a pediatric animal model was developed using puppies 6-12 weeks of age and 2-8 kg in weight. Hemodynamic status was assessed using standard methods, and measured global cerebral blood flow was assessed using the nitrous oxide (Kety-Schmidt) technique after placement of a catheter in the sagittal sinus. In this initial study, five puppies resuscitated with closed-chest cardiac compression (CCCC) were compared with five receiving open-chest cardiac compression (OCCC). Although mean systolic arterial pressures were equal with both methods during resuscitation (40 versus 49 mm Hg, P = 0.19), OCCC produced a greater cardiac output and a higher cerebral blood flow (5 versus 18 ml/100 g/min, P = 0.008). Only one of five dogs treated with CCCC had a blood flow during resuscitation greater than 15 ml/100 g/min, as compared with four of five receiving OCCC. Finally, three of five dogs in the CCCC group experienced liver lacerations, while none who were resuscitated by OCCC sustained any gross visceral injuries.

A model for technology assessment as applied to closed loop infusion systems. Technology Assessment Task Force of the Society of Critical Care Medicine

OBJECTIVES

To test a model for the assessment of critical care technology on closed loop infusion control, a technology that is in its early stages of development and testing on human subjects.

DATA SOURCES

A computer-assisted search of the English language literature and reviews of the gathered data by experts in the field of closed loop infusion control systems.

STUDY SELECTION

Studies relating to closed loop infusion control that addressed one or more of the questions contained in our technology assessment template were analyzed. Study design was not a factor in article selection. However, the lack of well-designed clinical outcome studies was an important factor in determining our conclusions.

DATA EXTRACTION

A focus person summarized the data from the selected studies that related to each of the assessment questions. The preliminary data summary developed by the focus person was further analyzed and refined by the task force. Experts in closed loop systems were then added to the group to review the summary provided by the task force. These experts' comments were considered by the task force and this final consensus report was developed.

DATA SYNTHESIS

Closed loop system control is a technological concept that may be applicable to several aspects of critical care practice. This is a technology in the early stages of evolution and much more research and data are needed before its introduction into usual clinical practice. Furthermore, each specific application and each device for each application (e.g., nitroprusside infusion, ventilator adjustment), although based on the same technological concept, are sufficiently different in terms of hardware and computer algorithms to require independent validation studies.

CONCLUSIONS

Closed loop infusion systems may have a role in critical care practice. However, for most applications, further development is required to move this technology from the innovation phase to the point where it can be evaluated so that its role in critical car practice can be defined. Each application of closed loop infusion systems must be independently validated by appropriately designed research studies. Users should be provided with the clinical parameters driving each closed loop system so that they can ensure that it agrees with their opinion of acceptable medical practice. Clinical researchers and leaders in industry should collaborate to perform the scientifically valid, outcome-based research that is necessary to evaluate the effect of this new technology. The original model we developed for technology assessment required the addition of several more questions to produce a complete analysis of an emerging technology. An emerging technology should be systematically assessed (using a model such as the model developed by the Society of Critical Care Medicine), before its introduction into clinical practice in order to provide a focus for human outcome validation trials and to minimize the possibility of widespread use of an unproven technology.

High-dose pentobarbital pharmacokinetics in hypothermic brain-injured children

The pharmacokinetics of pentobarbital were examined in 11 children with Reye syndrome, hypoxic encephalopathy, or acute head injury. Nine of these patients were hypothermic (less than 32 degrees C). The total systemic clearance and volume of distribution at steady state of pentobarbital were significantly reduced in these patients when compared to previous data in normothermic adult volunteers following intravenous doses of pentobarbital. Pentobarbital elimination half-life was not significantly different from control values. The diminished systemic clearance of pentobarbital may result from decreases in intrinsic enzyme activity that accompany hypothermia, as well as hepatic dysfunction in patients with Reye syndrome. Less extensive distribution of pentobarbital is likely the result of either differences in body fat composition or hypothermia-induced decreases in regional blood flow. The reduced clearance and distribution of pentobarbital may partially explain the enhanced reduction in cerebral metabolism that occurs on addition of hypothermia to barbiturate therapy in patients with elevated intracranial pressure.

Agenesis of the left diaphragm: surgical repair and physiologic consequences

Agenesis of the hemidiaphragm is an unusual congenital anomaly associated with a high mortality. This paper presents the fourth patient to survive the neonatal period with agenesis of the hemidiaphragm. He was an identical twin, weighing 1.5 kg and his clinical course was characterized by ipsilateral pulmonary hypoplasia, large alveolar-arterial gradient for oxygen, persistent fetal circulatory pattern and ventilator dependence. These abnormalities suggest a pathophysiology similar to that observed in patients with Bochdalek hernia. The surgical correction, postoperative care and observation of pulmonary function following repair of agenesis of the left diaphragm are described.

Current status of the multicenter randomized clinical trial on fetal oxygen saturation monitoring in the United States

Current clinical methods of intrapartum fetal assessment are sensitive but poorly specific in detecting fetal compromise during labor. These limitations have substantially contributed to the escalating cesarean section rate which occurred in the US during the last several decades. Experimental and clinical research efforts directed towards application of the oxygen saturation monitor (pulse oximeter) to intrapartum fetal assessment have produced encouraging results. If this new method of fetal assessment is to enter the clinical arena, safety and efficacy issues must first be properly evaluated via randomized clinical trials. The purpose of this report is to describe the design of a multicenter randomized clinical trial of intrapartum fetal oxygen saturation monitoring recently begun in the US. Specific aspects of the trial, including purpose, study design, sample size estimates, control and test groups, inclusion and exclusion criteria, fetal heart rate classification, definition of normal fetal arterial oxygen saturation (SpO2), clinical management protocol, and assessment of maternal-fetal outcomes will be addressed.

Effect of dichloroacetate in the treatment of anoxic lactic acidosis in dogs

Lactic acidosis is seen frequently after severe anoxia and circulatory failure. Because dichloroacetate (DCA) has been shown to be effective in the treatment of lactic acidosis, we studied its effect on lactate levels and pH in arterial and sagittal sinus blood specimens in a pediatric canine model of anoxic cardiac arrest followed by CPR. Lactate levels rose steadily in all puppies receiving DCA alone (group 1), DCA plus bicarbonate (group 2), bicarbonate alone (group 3), or neither drug (group 4). Arterial and sagittal-sinus lactate levels were in the range of 2 mmol/L during the baseline period, 6 mmol/L after anoxic arrest, and 10 mmol/L after 20 min of CPR. Bicarbonate, but not DCA, significantly raised arterial pH. Neither drug reversed the progression of acidosis in the sagittal sinus; mean pH ranged from 6.85 to 6.92 among the four groups after 20 min of CPR. We speculate that DCA did not decrease lactate levels or raise the pH in either the peripheral circulation or the CNS (sagittal sinus) because of poor perfusion achieved during closed-chest cardiac compression.

Scanning and transmission electron microscopy of calcified tissues

Some recent innovations have been utilized to extend studies of the structure of calcified tissues on the ultra- and microstructural levels of organization. The introduction of hydrazine as a replacement for the conventionally used ethylene diamine to deproteinize calcified tissue samples has resulted in the acquisition of previously unobtainable information about the mineral phase as it exists in situ. This enables inference of mineral-organic interrelationships when coupled with the EDTA demineralization technique used to study collagen fiber frameworks. In addition, a method for obtaining whole single osteons and separating them into lamellar constituents permits observations of the collagen-apatite orientation within successive lamellae of compact Haversian bone. The use of the structural information derived to develop a fiber-reinforced model of compact bone as a composite material is outlined and discussed.

Management of Reye's syndrome

Reye's syndrome is a potentially devastating neurologic illness seen predominantly in children following a viral prodrome. The cause is unknown. The clinical history and laboratory presentation are stereotypical and easy to recognize if the clinician considers the diagnosis. Neurologic dysfunction is characterized by lethargy, obtundation, persistent vomiting, agitated delirium, and coma. Death is secondary to severe cerebral swelling with elevation of intracranial pressure. Although no specific therapy has been clearly demonstrated to be superior in terms of outcome, most clinicians have adopted a management scheme aimed at lowering and controlling the elevated ICP. We have described the management protocol in use at the Children's Hospital of Philadelphia. The protocol is summarized in the Appendix for the convenience of the reader.