Infants who are born prematurely commonly lack regulatory mechanisms to control essential life functions, such as regular breathing, thermal homeostasis, and enteral intake of nutrients. They often require assisted ventilation and supplemental oxygen beginning at birth, and an immature heart and circulation sometimes leads to systemic hypotension, inadequate organ perfusion with resultant oliguria, and metabolic acidosis. Thus, frequent or continuous monitoring of vital signs, namely temperature, blood pressure, heart rate, breathing pattern, and oxygen saturation, is an extremely important aspect of intensive care for very immature infants. Monitoring of these critical variables should begin immediately after birth, with appropriate provision of an adequate heat source to prevent hypothermia in the delivery room and during transport to the intensive care nursery; assisted ventilation with sufficient supplemental oxygen to prevent hypoxia and hypercapnia; and early intravenous access to allow delivery of glucose-containing solutions and emergency drugs if needed.
In the intensive care nursery, a more thorough assessment of the infant’s condition should include accurate baseline measurements of body weight, length, and head circumference to identify possible discordance between gestational age and prior intrauterine growth. For management of extremely small, immature, and sick newborns, it is often useful to care for the infant on a platform balance beneath the bedding to allow frequent weight determination with minimal disturbance of the infant. The infant should remain in a warm environment, with continuous monitoring of heart and respiratory rates, oxygen saturation (SaO2; pulse oximetry), and temperature. If extra oxygen is needed, with or without mechanical ventilation, partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) should be measured at frequent intervals or monitored continuously with transcutaneous electrodes. The target for PaO2 should be 50 to 80 mm Hg (SaO2 90â€“95%), and the target for PaCO2 should be 40 to 50 mm Hg, although higher values for PaCO2 may be tolerated to reduce the risk of lung injury if the infant is being managed on mechanical ventilation.
In all seriously ill preterm infants, and in those who have evidence of poor peripheral circulation, the arterial blood pressure should be monitored either through an indwelling catheter placed in the umbilical artery or through a catheter inserted percutaneously in a peripheral artery, or noninvasively with a limb cuff and oscillometric recording device. The arterial catheter also can be used for blood sampling, including measurements of arterial pH, PaO2, and PaCO2. Indwelling catheters should be removed when the infant becomes stable and does not require continuous monitoring of blood pressure or frequent measurements of arterial blood gas values. For infants who are born prematurely, or for those with suspected infection, a sample of blood for culture, complete blood count, and glucose concentration should be obtained soon after birth in advance of antibiotic therapy and intravenous nutrient delivery.
Infants with mild to moderate respiratory distress who require supplemental oxygen often can be treated effectively with nasal application of continuous positive airway pressure (CPAP) of between 5 and 8 cm H2O. The device used for nasal CPAP should be lightly attached to the nose to avoid damage to the skin and nasal septum. Infants with more severe respiratory distress usually require endotracheal intubation and mechanical ventilation with PEEP of 3 to 5 cm H2O, with ventilation settings adjusted to maintain modest chest rise and adequate oxygenation and ventilation.