CASE STUDY

This case study summarizes the concepts presented in this chapter. The neonatologists and anesthesiologists at the University of California, San Francisco, were notified of the impending birth of a 1500-g, appropriate-for-gestational-age neonate by a mother whose membranes had ruptured 24 hours earlier. Labor had progressed despite the use of tocolytic agents. The obstetricians typed and crossmatched the mother's blood against one unit of type O, Rh-negative packed red blood cells and one unit of whole blood so that blood would be available in the delivery room to transfuse the neonate during resuscitation if the blood volume or hematocrit level was low. Both units of blood were in the delivery room in separate plastic cold packs before the neonate's birth.

2362

Before the neonate was born, arterial and venous pressure transducers and an umbilical SaO₂ catheter were calibrated. A blood-gas machine and a centrifuge were moved into the resuscitation area so that blood gas, pH, and hematocrit data would be available within 2 minutes of obtaining the blood sample. An anesthesiologist, attending neonatologist, neonatology fellow, pediatric resident, and two neonatal nurses provided care for the neonate during resuscitation.

The neonate was born vaginally. Her mouth and nose were suctioned, and her umbilical cord was clamped and transected. She was handed to a waiting anesthesiologist and dried with a towel as she was quickly taken from the delivery room to the resuscitation room (a distance of 20 feet). The umbilical cord was clamped and cut immediately after birth because the patient was apneic and because her heart rate was about 100 beats/min. Under the assumption that she would be hypovolemic, those caring for the neonate were prepared to infuse blood if her MAP was more than two standard deviations (2 SD) below the average MAP for a patient of her gestational age.

The neonate was weighed immediately on her arrival in the resuscitation area. This took less than 10 seconds. Knowing her correct weight allowed those resuscitating her to administer the appropriate doses of drugs, fluids, and blood during resuscitation. After weighing the neonate, she was placed on the sterile resuscitation table, needle electrodes were inserted under her skin to continuously provide an electrocardiogram and measure the heart rate, and her trachea was intubated. Ventilation was controlled with 25 cm H₂ O pressure and 100% oxygen. The first inspiration was held for 2 seconds. After the first breath, ventilation was controlled at a rate of 60 breaths/min; pressures of 20/5 cm H₂ O were applied during each breath. Every fifth inspiration was held for 2 seconds in an attempt to improve the distribution of ventilation and increase removal of fluid from the lung. By this time, the neonate was 1.5 minutes old. A pulse oximeter was applied to her hand, and her SaO₂ was less than 80%.

A nurse held the umbilical cord up in the air while the abdomen and umbilical cord were sterilized with povidone-iodine; the abdomen then was covered with sterile towels. Next, an umbilical tape was placed approximately 1 cm above the point where the umbilical cord entered the skin, and the tape was tied loosely. Care was taken not to include the skin of the abdomen in the tie. The umbilical cord and tie were then grasped with the thumb and index finger of one hand to control bleeding, the umbilical cord was cut cleanly, and the unwanted portion of the umbilical cord was discarded. The artery was dilated with a pair of curved iris forceps; an umbilical catheter was inserted into one of the thick-walled umbilical arteries. The catheter was advanced until blood flowed back into the catheter. When this occurred, the stopcock was closed, and the catheter was advanced an additional 2 cm. The catheter was then connected to the pressure transducer, and all air was removed from the system, after which the arterial blood pressure was measured.

Because the initial SaO₂ was less than 80%, the peak inspiratory pressure was increased to 25 cm H₂ O and the respiratory rate was increased to 80 breaths/min. A sample of blood was obtained for blood gases, pH, hematocrit level, electrolyte determinations, and blood culture and sensitivity of organisms to antibiotics. Because it is often difficult to distinguish hyaline membrane disease from intrauterine pneumonia, the neonate was given ampicillin (50 mg/kg) and gentamicin (2.5 mg/kg) through the umbilical catheter. At this point, the neonate was 5 minutes old.

The neonate's initial MAP was 24 mm Hg, and her systolic and diastolic pressures 40/20 mm Hg. Because she was hypotensive, hypoxic, and acidotic (PaO₂ of 38 mm Hg, PaCO₂ of 60 mm Hg, pH of 7.02, base deficit of 6.0 mEq/L) and because her hematocrit level was adequate (45%), ventilation was kept constant, and she was transfused with 5 mL/kg of whole blood. (Hypotension increases right-to-left shunting of blood through the lung, foramen ovale, and ductus arteriosus of hypoxic, acidotic neonates.) The blood transfusion raised the MAP to 26 mm Hg. However, within 2 minutes, the pressure fell to 24 mm Hg. The SaO₂ was 68%. Transfusing another 5 mL/kg of whole blood raised the MAP to 28 mm Hg, the lower limits of normal for neonates of this gestational age. Simultaneous with raising the MAP, the SaO₂ rose to 82%. A second blood gas measurement showed a PaO₂ of 46 mm Hg, PaCO₂ of 53 mm Hg, and pH of 7.15. Because the pHa had increased, the PaCO₂ had decreased, and the MAP was stable, we continued to ventilate her lungs rather than administer bicarbonate. Five minutes later, the MAP had increased to 30 mm Hg, and 100% SaO₂ had been achieved. Another sample of blood was obtained. The PaO₂ was 138 mm Hg, PaCO₂ was 37 mm Hg, and pH was 7.27. During the next 10 minutes, the SaO₂ remained above 90% despite a progressive reduction of FIO₂ to 0.75. On repeat testing, the PaO₂ was 70 mm Hg, PaCO₂ was 29 mm Hg, and pH was 7.46. Because of the increased pHa and the decreased PaCO₂ , the ventilatory rate was reduced to 60 breaths/min. The FIO₂ continued to be reduced as long as the SaO₂ remained between 87% and 94%. Fifteen minutes later, when the FIO₂ was 0.50, another blood gas was obtained (PaO₂ of 68 mm Hg, PaCO₂ of 35 mm Hg, and pHa of 7.42). The MAP was 32 mm Hg, and the SaO₂ and FIO₂ were stable for the next 15 minutes. A repeat blood gas determination was similar to the previous one. Consequently, the neonate was transferred to the neonatal intensive care unit.

The neonate had mild hyaline membrane disease. By the third day of life, her condition was improved. Mechanical ventilation was discontinued and the endotracheal tube removed. She was discharged from the hospital on the 48th day of life and was doing well. Current treatment includes giving 5 mg/kg of Exosurf into the endotracheal tube and continuing ventilation. This improves oxygenation more rapidly after blood volume is adequate.

2363

This case illustrates several basic points:

1. Resuscitation of severely ill neonates involves all the technology and people required to resuscitate an older child or adult from cardiac arrest. One person cannot do all the things required to resuscitate a neonate. It is essential to notify those who are going to resuscitate the patient in time for them to arrive in the delivery room before the patient is born.
2. Neonates who are severely depressed at birth are often hypovolemic and require immediate blood volume expansion. Failure to correct the hypovolemia makes it difficult to correct the hypoxia and acidosis.
3. Blood gas levels and pHa change rapidly during resuscitation. Results of these determinations should be immediately available so that the inspired oxygen concentration and the ventilation pressures and rates can be changed as necessary. Being told the blood gas results 30 minutes after the blood sample was obtained is of little value, because the blood gas levels and pH probably have changed during that time.
4. The equipment required for resuscitation must always be available in the delivery room, rather than waiting for an emergency to occur before finding the resuscitation equipment. The equipment needed includes heating lamps and heating blankets to maintain the neonate's body temperature at a normal level, umbilical arterial and venous catheters, surgical instruments to insert umbilical catheters, pressure transducers and monitors to measure intravascular pressures, and equipment to intubate the trachea and ventilate the lungs.

A hospital that cannot provide the care outlined in this case report should transfer mothers with high-risk pregnancies to a referral hospital early in their course of labor.