Cooling the newborn after asphyxia - physiological and experimental background and its clinical use

Many years of experimental work on hypoxic-ischaemic injury have supported the hypothesis that cooling the body and brain after the primary injury offers permanent neuroprotection. Clinically, the question of how late cooling can start after the insult and still have a protective effect is important and not fully investigated. Pilot studies in human adults initiated cooling after 10-18 h (trauma, stroke), however animal data suggest cooling is not effective if started later than 6 h. There might be a threshold for 'cooling dose' - by depth or duration - to achieve permanent protection. Hypothermia must be administered with understanding of the extensive physiological effects. Different enzymes have different sensitivity to changes in temperature, hence some effects may be beneficial and some deleterious. Hypothermia and cardiovascular responses and coagulation needs careful monitoring.

Novel treatments after experimental brain injury

Perinatal hypoxic-ischaemic encephalopathy(HIE) is being studied in laboratory models that allow the delayed cascade of events triggered by the energetic insult to be examined in detail. The concept of the 'excitotoxic cascade' provides a conceptual framework for thinking about the pathogenesis of HIE. Major events in the cascade triggered by hypoxia-ischaemia include overstimulation of N-methyl-D-aspartate type glutamate receptors, calcium entry into cells, activation of calcium-sensitive enzymes such as nitric oxide synthase, production of oxygen free radicals, injury to mitochondria, leading in turn to necrosis or apoptosis. New experimental approaches to salvaging brain tissue from the effects of HIE include inhibition of neuronal nitric oxide synthase, administration of neuronal growth factors, and inhibition of the caspase enzymes that execute apoptosis. Recent experimental work suggests that these approaches may be effective during a longer 'therapeutic window' after the insult, because they are acting on events that are relatively delayed. Application of modest hypothermia may allow these agents to be neuroprotective at even longer intervals after hypoxia-ischaemia.

Selection of babies for intervention after birth asphyxia

Based on animal experiments, the therapeutic window for neonates with signs of perinatal hypoxia-ischaemia is probably less than 6 h, and early selection of patients is of utmost importance. In term neonates, fetal heart rate and blood flow patterns, the Apgar score, and other clinical scoring systems are insufficient to select patients for intervention, whereas umbilical artery pH<7.0 combined with umbilical arteriovenous differences in PCO(2), lactate/pyruvate ratios in cord blood, and CSF interleukin-1beta have a better predictive value. At present, neurophysiological methods such as (amplitude-integrated) EEG and evoked potentials have the best predictive value. In preterm neonates, lactate/pyruvate and uric acid measurements in cord blood, as well as neurophysiology appear to be helpful to predict brain injury, and might be used to select patients for intervention.

Fetal oxygenation, assessment of fetal well-being, and obstetric management of the pregnant patient with asthma

Asthma is the most common chronic respiratory disease affecting pregnant women. To provide the best obstetric care, it is necessary to understand fetal oxygenation and how it can be affected by maternal asthma. During pregnancy, fetal well-being should be closely monitored, and asthma care should be carefully integrated with obstetric care. Optimal fetal assessment includes establishing gestational age, assessment of fetal growth, and monitoring fetal activity. Evaluation for high-risk patients may include the non-stress test, contraction stress test, or biophysical profile.

Keeping a cool head, post-hypoxic hypothermia--an old idea revisited

Hypoxia-ischaemia produces permanent brain damage by processes that continue for many hours after reoxygenation/reperfusion. This provides a window of opportunity for therapy aimed at preventing further loss of brain cells. Reducing brain temperature by 2-6 degrees C for 3-72 h after reoxygenation/reperfusion has been shown to reduce brain damage by 25-80% in controlled trials with six different neonatal animal models of hypoxia-ischaemia. No adverse effects from mild hypothermia have been documented. The mechanisms of protection are unknown but may include a reduction in extracellular excitotoxic amino acids, reduced nitric oxide synthesis and inhibition of apoptosis. Mild hypothermia is currently the most promising clinically feasible neural rescue therapy for full-term infants at risk of developing hypoxic-ischaemic encephalopathy, but clinical use must be restricted to approved trial protocols.

Intrapartum fetal monitoring

There is an undisputed need for close fetal surveillance during labour. The transition to extra-uterine life has a number of potential hazards-many of which may be averted by appropriately timed intervention. It is evident, however, that not all intrapartum sequelae can be avoided despite intensive surveillance and increasingly high rates of intervention.

Iatrogenic radiant heat burns in severely asphyxic newborns

We report two cases of newborns who developed second-degree burns following resuscitation under infra-red heating lamps. Both infants were asphyxic and suffered from insufficient peripheral circulation which, combined with the long duration of the exposure to the light, contributed to the development of the lesions. Both infants died shortly after birth for reasons other than the burns.

Pregnancy complicated by Ebstein's anomaly: oxygen administration to mother for chronic fetal hypoxemia. A therapeutic case report

For chronic fetal hypoxia due to maternal Ebstein's anomaly, oxygen was administered daily to the mother by mask for 105 days. At 20 weeks of gestation, umbilical venous blood gases in room air showed pH 7.42, PO2 25.7 mm Hg, PCO2 33.7 mm Hg and O2 saturation 48.7%, and changed to 7.45, 39.1 mm Hg, 25.9 mm Hg and 77.4% on 3 liters/min of oxygen inhalation by mask, respectively. The PO2 of the maternal arterial blood gases increased to 30 mm Hg on oxygen administration at 15 weeks of gestation, but at 25 weeks of gestation the PO2 increased by only about 10 mm Hg. At 30 weeks, intrauterine growth retardation was suspected. Just after the second puncture of the umbilical cord at 31 weeks and 3 days of gestation, 80 bpm fetal bradycardia occurred for several minutes without recovery and emergency cesarean section was done under the general anesthesia.

Weakness in the newborn calf

The peak time period for the average beef producer to experience the majority of calf losses has consistently been from the time of birth through the first seven days of life. Weakness is a principal clinical sign of diseases or conditions responsible for mortality including birth trauma, prematurity or dysmaturity, congenital malformations, metabolic defects, intrauterine infection, anoxia or hypoxia, hypothermia, starvation, extremes in birth weight, and post-natal infection. This article discusses anoxia/hypoxia and septicemia in greater detail because of their involvement as a common cause of weakness in the newborn calf.

Intrauterine resuscitation in the severely distressed fetal dog

Severe fetal distress was produced in 16 fetal dogs by successive and/or prolonged occlusion of the maternal abdominal aorta in an acute surgical preparation, and was characterized in fetal arterial blood of 7.06 for pH, 10 mm Hg for O2, 127 mm Hg for CO2, and fetal heart rate decelerations. Five fetuses recovered spontaneously in utero and delivered normally; 3 needed maternal oxygenation before delivery; 3 suddenly died in utero; 5 fetuses were delivered while still alive in utero when the tpH reached 6.85, and eventually expired. Intrauterine recovery and resuscitation was effective in some fetuses.

Glucose, lactic acid, and perinatal hypoxic-ischemic brain damage

Investigations suggest that hyperglycemia, superimposed on hypoxia-ischemia or cerebral ischemia, accentuates brain damage in adult experimental animals and humans, but not in immature animals. Fundamental differences in the immature and adult brain, which account for the age-specific paradox, are discussed. Based on currently available data, we recommend that glucose supplementation not be curtailed during labor and delivery of asphyxiated human infants; on the contrary, glucose therapy may substantially reduce hypoxic-ischemic brain damage.

Development of the coronary vasculature in hypoxic fetal rats treated with a purified perfluorocarbon emulsion

OBJECTIVE

To quantitatively define the coronary vascular bed in the 21-day-old rat fetus with gestational normoxia and hypoxia; to determine if maternal supplemental oxygen and/or oxygen-carrying perfluorocarbons (PFCs) influence development of coronary vessels; and to compare the results using purified and unpurified PFC treatment.

DESIGN

Unilateral uterine artery ligation was introduced on gestational day 17 in pregnant animals. Control fetuses were from unligated uterine horns. Experimental intervention occurred during gestational days 17 to 21, with fetuses recovered on day 21. Developing coronary vessels were analyzed quantitatively via light microscopy.

ANIMALS

Pregnant Sprague Dawley rats.

INTERVENTIONS

Following ligation, pregnant rats received no further treatment, supplemental oxygen inhalation alone, or daily intravenous purified PFC treatment, with or without supplemental oxygen.

MAIN RESULTS

Hypoxia caused an increase in resorptions (P less than 0.001), and decreased fetal body weight (P less than 0.001) and heart weight (P less than 0.05). Although the area occupied by developing coronary vessels (sinusoids) was substantially increased, maturation was unchanged. Oxygen supplementation alone did not appreciably influence fetal resorptions or body weight in ligated horns, but did increase fetal heart weight. Sinusoidal area decreased (P less than 0.01), with no effect on sinusoidal maturity. Purified PFC treatment did not alter maternal weight gain or fetal body weight, and moderately decreased resorptions in ligated horns. Fetal heart weight was augmented with purified perflurochemical, while unpurified perfluorochemical treatment diminished heart weight. Both PFC emulsions substantially decreased sinusoidal area.

CONCLUSIONS

Perflurocarbon treatment associated with supplemental oxygen is capable of improving the hypoxic effects on fetal heart and coronary vessel development if the emulsion used is appropriately purified.

Extracorporeal membrane oxygenation (ECMO) for non-ECMO intensive care nurseries

An extracorporeal membrane oxygenation (ECMO) centre has been established in the sole outborn-only level 3 nursery in Melbourne. In the absence of other guidelines, an infant may qualify for ECMO if the expected mortality, based on assessment of the severity of hypoxia, exceeds 80%. However, for a non-ECMO centre, this involves the additional hazard of transport for an already critically-ill infant. The aim of this study was to determine the predictors of at least 80% mortality in babies who might have qualified for ECMO but who were cared for in a non-ECMO level 3 nursery. Regardless of the severity or duration of hypoxia, we were unable to identify a group of infants whose mortality exceeded 80%. Since outborn infants were disproportionately over-represented amongst those who might qualify for ECMO, it would be advisable to admit preferentially those born outside the level 3 perinatal centres who might qualify for ECMO directly to the ECMO centre. For infants born within our level 3 perinatal centre, it is recommended not to transfer those who might qualify based on data from other centres until the exact role of ECMO is determined. Alternatively, a randomized controlled trial of transfer versus non-transfer to the ECMO centre for severely hypoxic infants cared for in non-ECMO level 3 nurseries could be considered.

The influence of oxygen administration to the mother during labor on the fetal transcutaneously measured carbon-dioxide partial pressure

The aim of this study was to plot the course of the transcutaneously measured PCO2 (tcPCO2) in the fetus during oxygenation of the mother. In our examination 35 parturients with a suspicious or pathologic CTG were given pure oxygen for 10 minutes at a flow speed of 10 l/min. The fetal tcPCO2 was measured with a TCM 3 measuring device from Radiometer. The measuring temperature was 41 degrees C. The fetal tcPCO2 was 67.2 +/- 3.9 mmHg before the O2 application, during the O2 application it was 67.3 +/- 14.1 mmHg and for the period after the O2 application we found an average measurement of 66.7 +/- 13.9 mmHg. Further we investigated whether, depending on the original levels of the fetal tcPCO2 an O2 application to the mother had a measurable effect on the fetal tcPCO2 levels. The average levels of the tcPCO2 in the fetuses with pathological original levels of greater than or equal to 60 mmHg or with normal levels of less than 60 mmHg did not show any significant differences before, during or after the O2 application. Our own results and reports given in the literature about an increase in the fetal O2 partial pressure during maternal oxygenation lead to the conclusion that in cases with fetal hypoxia, the O2 application to the mother--in addition to other measures for intrauterine reanimation or speedy termination of labor--could be of advantage.

Prevention, recognition, and treatment of perinatal asphyxia

Management of perinatal asphyxia is one of those rare opportunities in clinical medicine when death or life-long disability can be prevented with several minutes of skillful and judicious action. Fetal and neonatal asphyxia is approached most successfully as a joint obstetric, pediatric, and anesthetic effort. This article reflects the team approach to perinatal asphyxia.

[Placental scintigraphy--a diagnostic method for evaluating indications for hyperbaric oxygenation in pregnant women with high risk of perinatal pathology]

At most, 40 pregnant females at a high risk for fetal perinatal pathology underwent clinical investigation, ultrasonic scanning of the placenta, recording of the fetal electro- and phonocardiography, the evaluation of the placental levels of lactogen and estradiol and thermoresistant alkaline phosphatase changes of the values considered who were then treated with hyperbaric oxygenation (HBO) under the control of dynamic placental scintigraphy. Based on the placentographic findings, the authors distinguished from the whole of the risk-group the patients whose pattern of uteroplacental blood flow response to the treatment was beneficial and therefore the HBO treatment for fetoplacental insufficiency was advisable.

[Continuous respiratory therapy of newborn and premature infants with respiratory disorders]

2216 newborns and prematures with respiratory distress of different underlying diseases were treated with long term respiratory therapy from 1. Jan. 1975 to 31. Dec. 1985. One part of the patients were born in our hospital, the other part of them were transported from outside. The rate of prematures was 81.2%. The respiratory therapy was applied in 1813 cases because of pulmonary diseases (group 1.), while in 403 cases the respiratory troubles were extrapulmonary in origin (group 2.). The diseases in the first group were as follows: hyaline membrane disease in 482 cases (27.30%), intrauterine pneumonia in 634 cases (34.64%), postnatal pneumonia in 291 cases (15.90%), meconium aspiration syndrome in 110 cases (6.01%), severe RDS-II in 158 cases (8.63%), pulmonary immaturity in 116 cases (6.35%), persistent fetal circulation in 21 cases (1.15%) and pulmonary aplasia on the left in 1 case (0.021%). In the second group the greatest part of the cases were treated for neurological disturbances. We discuss the indications of different types of respiratory therapy and the complications as well. The survival rate was in the first group 59.3%, while in the second only 16.9%. Therefore the respiratory therapy seems to be more effective in the pulmonary diseases of the newborns. The mortality rate and the rate of severe complications were lower among inborn babies because of the early application of the respiratory therapy.

[Indications for cesarean section in the delivery of the 2d twin after vaginal birth of the 1st twin]

Cesarean section for delivery of twin B after vaginal delivery of twin A is a rare and extraordinary event in obstetrics. From 1.1.82-31.12.86, from a total number of 9357 deliveries, 133 pairs of twins (1.4%) were born. In 3 cases (2.2%) twin B was delivered by cesarean section after vaginal delivery of twin A. Taking into account 51 published cases in the recent literature, the indications for cesarean delivery of the second twin were demonstrated and compared. In the main, emergency situations presenting more than one obstetrical complication were responsible for this uncommon practice. Regarding the results presented, cesarean section of the second twin after vaginal delivery of the first-born seems to be a proven procedure to deliver the second twin faster and more safely than by hazardous vaginal manipulations, especially in obstetrical emergency situations.

Maternal oxygen therapy for intrauterine growth retardation

Humidified oxygen (55%) was administered continuously through a face mask to 5 patients whose pregnancies (4 singleton and 1 twin) were all complicated by severe intrauterine growth retardation, oligohydramnios, high blood-flow impedance in the fetal aorta and umbilical artery, and low mean blood-velocity in the fetal thoracic aorta. All the fetuses were hypoxic and 2 were acidotic. After maternal hyperoxygenation, the fetal pO2 increased to within or near the normal range, and resulted in a sustained increase in the mean blood-velocity in the fetal thoracic aorta. 5 fetuses survived with minimum neonatal morbidity. The effect of maternal hyperoxygenation on the fetal pO2 in such cases may prove to be a useful method of assessing placental function and guiding management.