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Because of an increased survival rate in the neonatal intensive care unit (NICU), more and more “ex-preemies” are presenting to the operating room for surgical procedures. Remember that the premature infant is defined as being less than 37 weeks gestational age. Therefore, an “ex-preemie” by definition has now reached greater than 37 weeks conceptual age. This discussion will consider the anesthetic management of premature, as well as ex-premature, infants.

Only a few studies have concerned themselves with the development of the fetal vertebral column, and this paper attempts to extend the literature. Standards are presented for the growth in width of the human vertebral column between 10 and 26 weeks of conceptual age. The growth patterns show that cervical and lumbar enlargements are not present at 8 weeks but develop slowly and become clearly present at 26 weeks. The growth equations also show that groups of vertebrae have their own growth patterns, indicating that the vertebral column could be separated into five groups: C1-C5, C6-C7, T1-T12, L1-S1, and S2-S5. Furthermore, comparisons with growth patterns available for growth in length from other studies reveal that some vertebrae appear to develop in one dimension independently of another.

The relative composition of skin, muscle, and bone and their distribution patterns throughout the body are given for a series of Macaca mulatta from 171 days conceptual age through adulthood. In terms of percent of total body weight, the musculature of these animals doubles during the firs postnatal year whereas bone and skin decrease. Regionally, the muscles of the thighs, back extensors, truncal-forelimb and upper arms increase most markedly. The thighs double and the upper arms increase whereas the trunk, hands, feet, and tail decrease. The biomechanical implications of these changes for motor development are discussed.

The accuracy and precision of gestational dating, based on single measurements of the fetal biparietal diameter (BPD), was estimated in a consecutive series of 970 apparently normal, singleton pregnancies. The BPD sizes used varied between 11 and 60 mm, corresponding to 9-22 postconceptional weeks. The 'conceptual ages', used for reference, were estimated by means of ultrasonic measurements of the fetal crown--rump lengths (CRL). The association between the estimated conceptual age (dependent variable) and BPD size (independent variable) was found to be well represented (R2 = 0.972) by a second order polynomial: conceptual age = 44.7 + 1.069 X BPD + 0.01382 X BPD X BPD. To check the validity of the proposed equation, we used 23 fetuses conceived by artificial insemination with donor semen as controls. There was good agreement between the virtual conceptual ages of the control cases and their corresponding BPD-estimated conceptual ages (0.5 days mean difference, 3.6 days SD) when the suggested regression equation was used. The estimated precision of BPD-dating was minumum +/- 4.4 days (= +/- 2SD) at 9-10 completed postconceptional weeks. At 14 completed weeks the corresponding precision was found to be +/- 11 days (+/- 2SD). At the end of the studied BPD size interval, i.e. 56-60 mm BPD corresponding to 22 conceptual weeks, the precision was +/- 15 days. From an obstetrical point of view it seems obvious that the imprecision of gestational dating associated with BPD measurements greater than 35 mm should call for ultrasonic dating procedures to be performed earlier in pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

To determine whether prematurely born infants with a history of idiopathic apneic episodes are more prone than other infants to life-threatening apnea during recovery from anesthesia, the authors prospectively studied 214 infants (173 full term, 41 premature) who received anesthesia. Fifteen premature infants had a preanesthetic history of idiopathic apnea. Six of these required mechanical ventilation because of idiopathic apneic episodes during emergence from anesthesia. Two were ventilated for other reasons, and seven recovered normally. Infants ventilated for apnea were younger (postnatal age 1.6 +/- 1.2 months, mean +/- SD; conceptual age 38.6 +/- 3.0 weeks) than those who recovered normally (postnatal age 5.6 +/- 2.7 months; conceptual age 55.1 +/- 11.3 weeks) (P less than 0.01). No other premature or full-term infant was ventilated because of postoperative apneic episodes. The authors conclude that anesthetics may unmask a defect in ventilatory control of prematurely born infants younger than 41-46 weeks conceptual age who have a preanesthetic history of idiopathic apnea.

The quality of the awake state and attention in preterm infants has been evaluated by rating indices of attention such as widening of the eye, type of fixation, brightening, scanning, and cessation of sucking measured during visual fixation of patterns. Twenty-six infants ranging from 28 to 32 weeks' gestation at birth (mean, 31 weeks) were tested from one to four weeks postnatally until 36 weeks' gestation. Indices of attention were rated on a scale of 4 with an optimal mean index of 4. A progressive increase in behaviors associated with fixation of visual stimuli has been shown from 32 to 36 weeks of conceptual age. Mean scores ranged from 0.7 at 31 weeks' gestation to 1.8 at 34 weeks' and 2.7 at 36 weeks' gestation. The possibility therefore exists that by as early as 31 to 32 weeks from conception the human brain may be capable of waking states and thus able to process some sensory stimulation.rease in behaviors associated with fixation of visual stimuli has been shown from 32 to 36 weeks of conceptual age. Mean scores ranged from 0.7 at 31 weeks' gestation to 1.8 at 34 weeks' and 2.7 at 36 weeks' gestation. The possibility therefore exists that by as early as 31 to 32 weeks from conception the human brain may be capable of waking states and thus able to process some sensory stimulation.

Sound spectrographic cry analysis was performed on 302 cries of 48 preterm infants born at 30–37 gestational weeks. The cries were recorded during the first week of life and thereafter weekly until the infants were discharged. The control series comprised 54 cries from 27 fullterm healthy infants. The results showed that the cries of the smallest prematures compared with the controls were shorter, more high-pitched, and included bi-phonation and glide more often. The cry characteristics changed with increasing conceptual age and the older the child the more the cry pattern resembled that of the fullterm. The cries of the preterm infants when they had reached 38 conceptual weeks were similar to those of newly born fullterm infants. The results indicate that the gestational age should be taken into consideration in cry analysis.

Summary. The association between fetal anthropometric measurements and conceptual age was determined for the femur length and the mean of two abdominal diameters for conceptual ages between 10 and 20 completed weeks. The conceptual age used for reference was determined by the fetal crown-rump length measured at an earlier examination. Two equations are presented for the calculation of conceptual age from isolated estimations of the femur length or the mean of two abdominal diameters. Mean abdominal diameter and femur length measurement values were found to have similar precisions of dating.

The mean concentration of citric acid in male and non-pregnant female adult guinea pig plasma was 0.308 ± 0.042 mM. Pregnant females with fetuses of 49–69 days gestational age had mean maternal and fetal plasma concentrations of 0.440 ± 0.011 and 0.217 ± 0.053 mM, respectively. Maternal and fetal values were not correlated. Neonates up to 96 h old had plasma citrate values similar to those in the fetus. The citrate concentration of the amniotic fluid was lower than that in fetal plasma and showed a negative correlation with conceptual age (p < 0.01).

Eleven preterm infants with gestational age (GA) ranging from 24 to 34 weeks were observed during the neonatal period to determine state, posture, quantity and quality of motor activity, and any effect of ventilatory assistance (VA) upon these functions for the 7 VA infants in the group. Infants were observed for a 10 minute period at a specific time daily during the first week, then weekly throughout the nursery course. State was determined using Brazelton grading. Posture was recorded at the beginning of the observation. All movements of head, eyes, body and limbs were recorded according to defined categories. The predominant behavioral states observed were light sleep and dozing. No specific preference for body and/or limb posture was observed. All infants had frequent twitches and movements predominantly of the limbs which produced posture changes. Quantity of movements did not follow any particular patterns. However, a marked change in quantity of movements was usually associated with sedation and/or illness. Clonus and tremors were almost always seen in the ventilatory assisted infant, and rarely the non-respirator infants. Posture as well as quantity and quality of movements was not related to GA or conceptual age (CA). In conclusion, the serial and systematic observation of motor activity in the preterm infant confirms the time honored clinical observation that changes in motor activity may herald significant illness. In spite of previous work by others, in this group of preterm infants posture preference did not relate to GA or CA.