Polygraphic tracings of 13 normal infants were recorded in a morning sleep at 1 and 2 weeks of age and 1, 2, 3, 4, and 6 months of age. A vibrotactile stimulus graded at 25, 50 and 100 Hz (frequency) and amplitudes of 1, 2 and 3 mm (intensity) was used, each combination being applied twice at 30 s intervals to the hand of the sleeping infant during active sleep (AS) and quiet sleep (QS). The results were analysed as percentages of failure to arouse (FTA) in relation to the number of stimulus trials, the criteria for FTA being the absence of a response in heart or respiratory rate, electroencephalogram, or chin electromyogram. The percentages of FTA from QS did not change significantly from 1 week to 6 months of age, irrespective of frequency or intensity. The percentages of FTA from AS fell sharply and significantly from 1 week to 2 months of age (P less than 0.001). At 3 months of age there was a significant increase followed by a significant decrease at 4 months of age, both changes showing a significant difference at P less than 0.05. Apart from the first week of age, the numbers of FTA from QS were greater than from AS for all stimulus trials. It is concluded that there is an arousal deficit in QS from 1 week to 6 months of age and the temporary deficit in AS at 3 months of age could explain the peak incidence of SIDS at this time.
In the present economic climate and with increasing expenditure on neonatal intensive care, there has been a demand for economic evaluation and justification of neonatal intensive care programmes. This study assesses the inhospital costs of neonatal intensive care. Fixed and variable costs were calculated for services and uses of an Intensive/Special Care Nursery for the year 1985 and corrected to 1987 Australian dollar equivalents. Establishing a new neonatal intensive care unit of 43 costs in an existing hospital with available floor space including operating costs for a year were estimated in Australian dollars for 1987 at $6,408,000. Daily costs per baby for each were $1282 ventilator, $481 intensive, $293 transitional and $287 recovery, respectively. The cost per survivor managed in the Intensive/Special Care Nursery in 1985 showed the expected inverse relationship to birthweight being $2400 for greater than 2500 g, $4050 for 2000-2500 g, $9200 for 1500-1999 g, $23,900 for 1000-1499 g and $63,450 for less than 1000 g. Further analysis for extremely low birthweight infants managed in 1986 and 1987 demonstrated costs per survivor of $128,400 for infants less than 800 g birthweight and $43,950 for those 800-999 g. This methodology might serve as a basis for further accounting and cost-evaluation exercises.