Effect of ambient temperature on SIDS rate.

OBJECTIVE: To examine the relationship between ambient temperature and rate of sudden infant death syndrome (SIDS). SUBJECTS AND SETTING: All infants with SIDS occurring during 1980-1989 in the Sydney metropolitan area. RESULTS: The SIDS rate varied more than threefold over the months of the year and peaked at the minimum daily temperature in July. The rate was negatively linearly related to both the monthly mean minimum and maximum daily temperatures. Both relationships were highly significant (P < 0.001). CONCLUSION: The significant relationship between daily temperature and SIDS rate means either that daily temperature is an excellent indicator of the cold weather conditions that have a profound effect on the rate of SIDS or that temperature itself plays a direct role in the cause of SIDS.

The pneumographic and medical investigation of infants suffering apparent life threatening episodes.

Investigation of 340 babies who suffered from apparent life threatening episodes (ALTE) was performed using pneumographic studies and a variety of medical investigations. A number of medical abnormalities were demonstrated by history or investigation, including gastro-oesophageal reflux (211), airways pathology (17), evidence of fits (25), brain-stem tumour (2), hypoglycaemia (2), respiratory syncytial virus (8) and possible Munchausen by proxy (5). Pneumographic abnormalities were detected in 27 of the 340 infants. Home monitors were used for 135 infants. Future central apnoeas occurred in 20 of the 26 infants on home monitors that had had an abnormal pneumogram, compared with one of the 109 infants on home monitors after a normal pneumogram. Thus pneumograms have a sensitivity and specificity of 95% for predicting central apnoeas in babies who have already suffered an ALTE. The effect of eyeball pressure on the heart rate was measured in 65 babies and was found to cause a brisk drop in heart rate in 32 babies. Twenty-two of the 32 babies had future white apnoeas (usually associated with gastro-oesophageal reflux), compared with five of the 33 babies who had no drop in heart rate in response to eyeball pressure. Thus this test has a sensitivity of 81% and a specificity of 74% at predicting white apnoeas in babies who have already suffered an ALTE.

Pneumographic studies: predictors of future apnoeas but not sudden infant death in asymptomatic infants.

Pneumograms were performed on 401 asymptomatic infants: 322 siblings, 15 cousins and 24 twins of sudden infant death syndrome (SIDS) victims; 14 siblings of near-miss SIDS victims, and 26 infants of anxious parents. The infants of anxious parents had significantly fewer abnormalities than siblings of SIDS victims. In 222 infants subsequently monitored at home, the pneumogram as a predictor of future apnoea had a sensitivity rate of 97.5% and a specificity rate of 72% (P less than 0.001). Infants who were to experience future apnoeas had a significantly higher percentage of time in periodic breathing and a higher density of apnoeas in their original pneumograms. However, the abnormal pneumogram did not predict SIDS, because the eight infants who died all had normal pneumograms.

Hypoxic-ischaemic encephalopathy after near miss sudden infant death syndrome.

Between 1982 and 1985, 14 infants aged 3-26 weeks presented with severe hypoxic episodes as a result of the 'near miss' sudden infant death syndrome (SIDS). They all had metabolic acidosis, cardiovascular instability, acute renal failure, ischaemic colitis, or acute neurological dysfunction. Investigation of the cause excluded infection and trauma, or a primary metabolic, pulmonary, cardiac, or seizure disorder. Seven infants were deeply comatose on admission, never regained consciousness, and died within 60 hours. A characteristic evolution of hypoxic-ischaemic encephalopathy not previously clearly described after near miss SIDS was seen in the seven who lived. Five of the seven were conscious within one hour of resuscitation and showed a striking interval of near normality before neurological deterioration that was characterised by status epilepticus, deep coma, and brain stem dysfunction from 36-96 hours after the event. A biphasic course was not apparent in the remaining two, each of whom was comatose on admission, though refractory seizures did develop. Computed tomograms of the brain more than a week after the event showed cortical infarction or cerebral atrophy. Six of the survivors, followed up from 16-55 months, have serious residual deficits including spastic quadriplegia, delayed development, cortical blindness, or infantile spasms.

Review of 'near-miss' sudden infant death syndrome and results of simplified pneumographic studies.

Pneumographic studies were carried out on 92 infants suffering from 'near-miss' Sudden Infant Death Syndrome, 67 siblings of Sudden Infant Death Syndrome victims, and five infants of anxious parents. Medical investigations revealed a wide range of causes for episodes presenting as apnoea. The simple pneumographic studies had a 94% sensitivity and specificity for the prediction of future apnoeas.

Brainstem auditory evoked responses in infants at risk of sudden infant death.

Brainstem auditory evoked responses (BAERs) were recorded from 63 near-miss Sudden Infant Death Syndrome (NMSIDS) infants, 26 siblings of SIDS (SSIBS) infants and 67 control infants between 0 and 30 weeks post-term. The majority of BAERs recorded from the NMSIDS and SSIBS infants had normal form and interpeak intervals (V-I and V-IIn) within normal limits for their age. However, 15% of these infants had interpeak intervals outside the normal range, suggesting abnormal neural function in these cases. The distributions of interpeak intervals for all NMSIDS and SSIBS infants were skewed towards longer times compared to control infants. The distributions of V-IIn intervals for both groups of at risk infants were significantly different to that of control infants. While the observations confirm that the recording of BAERs is not suitable for identifying infants at risk of SIDS, they suggest, however, that maturation of neural processing in the brainstem of these infants may be delayed.

Simplified pneumographic monitoring of infants at risk from sudden infant death syndrome.

A system of pneumographic study of infants considered at increased risk from the sudden infant death syndrome is described. It is simple for nursing staff to use and for clinicians to interpret. A total of 166 'at risk' infants were studied and 85 were subsequently monitored at home. Seventeen of these infants, 16 of whom had had abnormal pneumograms, subsequently suffered significant apnoea. Four of 20 babies who had abnormal pneumograms did not have subsequent episodes of apnoea. Two babies died; the first was on a monitor but the second, despite having had an abnormal pneumogram, was not.

Effects of 2% carbon dioxide, 0.5% carbon dioxide, and 100% oxygen on cranial blood flow of the human neonate.

The effects of breathing 100% O2, 2% CO2, and 0.5% CO2 on the cranial blood flow of the normal human baby were investigated. A mercury in Silastic strain gauge was placed around the occipital head circumference (OFC) of a sleeping infant, and jugular flow was measured using venous occlusion plethysmography. Cranial flow was calculated using formulas derived from an electrical model. In matched sleep states cranial blood flow fell with 100% O2 (mean from eight babies = 32.8%), and rose with 2% CO2 (mean from seven babies = 40.6%). With 0.5% CO2 the flow rose in three babies and did not change in another four. These results indicate the extreme sensitivity of cerebral vasculature to the nature of the ambient gas.

Effects of sleep state and feeding on cranial blood flow of the human neonate.

Jugular venous occlusion plethysmography was performed on sleeping babies. Cranial blood flow (CBF) was calculated by correcting for noncompressible drainage pathways. Sleep state of the baby was monitored using clinical and EEG criteria. In 20 babies CBF was consistently higher in rapid eye movement (REM) sleep compared with nonREM sleep (mean difference 24.2%). In 7 babies systolic blood pressure was consistently higher in REM sleep (mean 20.2%). There was no correlation between the degree of change in blood pressure and CBF. In 11 babies in whom CBF was measured at known times after feeding, there was a consistently lower flow rate during the first hour compared with 2 hours later (mean difference 34.5%). The degree of change was unrelated to amount of feed taken, despite the method of test weighing being demonstrably accurate.

An estimation of intracranial blood flow in the new-born infant.

1. A non-invasive method for the estimation of the intracranial blood flow of the new-born infant is described, and results obtained with it are presented. 2. The technique is a novel application of the principle of blood flow measurement by venous occlusion plethysmography. It is possible to apply a plethysmographic technique to the neonatal cranium because the presence of open sutures between the component bones permits small, but readily measurable, changes in intracranial volume to occur. 3. Skull volume changes are calculated from changes in the occipito-frontal circumference of the cranium as recorded and measured with a mercury-in-Silastic strain gauge. 4. The jugular veins in the baby's neck are occluded by finger pressure and there follows an increase in skull volume, which is rapid at first, but which decreases exponentially as venous drainage diverts to non-occluded channels such as the vertebral venous plexus. At the instant of jugular occlusion the rate of skull volume increase is representative of the rate of flow in the jugular vessels prior to occlusion, and so provides an index of the relative magnitude of the intracranial blood flow. The method thus allows changes in intracranial blood flow to be followed. When occlusion is released cranial volume decreases, initially rapidly, but slowing exponentially as resting volume is regained. 5. A theoretical model of the events occurring during the inflow and outflow phases has been developed, and a formula derived which allows an estimation to be made of the flow of blood through uncompressed channels. The measured value of jugular blood flow can then be augmented to an estimate of total intracranial flow. 6. The mean cerebral blood flow of sixteen normal babies was estimated to be 40 ml. 100 g-1.min-1 (S.D. = +/- 11.63).

Clinical comparison between glucose and sucrose additions to a basic electrolyte mixture in the outpatient management of acute gastroenteritis in children.

In a double-blind trial in 94 children attending outpatients the value of glucose or a sucrose addition to a basic electrolyte mixture for the management of acute gastroenteritis was compared. Of the children treated with added sucrose 10% failed to respond compared with 27% of those treated with added glucose. This difference was significant (P=0-05), but the time to recovery in those in the two groups who responded to treatment was not significantly different. Thus, despite theoretical advantages, there was no practical advantage in using glucose rather than sucrose. A 5% sucrose electrolyte solution with its relatively low osmolality, ready availability, and ease of preparation is recommended as the treatment of choice in the outpatient management of acute gastroenteritis in infancy.