Early neonatal assessment usually consists of:
1. Apgar score (Table 35.1),
2. time to sustained respiration (TSR), and, occasionally,
3. biochemical status, and
4. neurobehavioural testing (usually for research purposes).
Long-term outcome is rarely studied.
The infant's Apgar score (up to a maximum of 10 points) is evaluated at 1 and 5 minutes. A 1 minute score of 4-6 is taken to signify moderate depression and ventilation of the neonate with oxygen is recommended. A score of 0-3 indicates severe depression (or cardiac arrest) and urgent resuscitative measures should be instituted immediately.
Prior to the advent of continuous epidural block, repeated large doses of intramuscular pethidine, often combined with sedatives (eg promazine), were standard maternal pain relief in most labour wards. Neonatal depression was frequently evident even on cursory examination. The use of lignocaine and mepivacaine in the early days of continuous epidural block were associated with "floppy but alert" neonates (1) (Chapter 77).
Today, few neonates are delivered in a depressed condition as a result of the choice of maternal analgesia. This reduction in incidence can be attributed to the:
1. decreased use of intramuscular pethidine,
2. availability of naloxone to reverse narcotic effects,
3. almost universal use of bupivacaine for continuous epidural block in labour (Chapter 25).
The Apgar score is not an appropriate tool for the detection of subtle changes in early infant behaviour. These assessments can be made using methods such as the:
1. Brazelton Neonatal Behavioural Assessment Score,
2. Early Neonatal Neurobehavioural Scale, and
3. Neurologic and Adaptive Capacity Score (Table 35.2).
Concern has been expressed that neonatal depression can occur as a result of large, repeated doses of epidural fentanyl given just before delivery (especially if fentanyl is "trapped" in an acidotic fetus). Scientific evidence for this is lacking.
In the case of general anaesthesia for caesarean section, the induction to delivery (I-D) time may be important. If I-D interval is prolonged beyond about 10 minutes, placental transfer of anaesthetic agents may contribute to neonatal depression (2) (Chapter 50). Similarly, the time from uterine incision to delivery (U-D) may be critical. Fetal acidosis can be anticipated if the U-D interval is greater than 90 seconds in patients under general anaesthesia (3).
These time constraints are of lesser importance when epidural or spinal anaesthesia is used (4).
Intrapartum and early neonatal death rates provide a reliable, if crude, measure of neonatal outcome. One survey showed that epidural analgesia was associated with a marked reduction in neonatal mortality in low birthweight babies (5). A study of neonatal outcome following 3940 caesarean sections showed a doubling of the mortality rate when general, as opposed to regional, anaesthesia was used (6).
References:
1. Scanlon JW, Brown WU, Weiss JB, Alper MH. Neurobehavioral responses of newborn infants after maternal epidural anesthesia. Anesthesiology 1974 40:121-128.
3. Datta S, Ostheimer GW, Weiss JB, et al. Neonatal effect of prolonged anesthetic induction for cesarean section. Obstetrics and Gynecology 1981 58:331-335.
4. Hodgson CA, Wauchob TD. A comparison of spinal and general anaesthesia for elective caesarean section: effect on neonatal condition at birth. International J of Obstetric Anesthesia 1994 3:25-30.
5. David H, Rosen M. Perinatal mortality after epidural analgesia. Anaesthesia 1976 31:1054-1059.