John M. D. Thompson

Bed sharing, smoking, and alcohol in the sudden infant death syndrome. New Zealand Cot Death Study Group.

OBJECTIVES--To investigate why sharing the bed with an infant is a not consistent risk factor for the sudden infant death syndrome in ethnic subgroups in New Zealand and to see if the risk of sudden infant death associated with this practice is related to other factors, particularly maternal smoking and alcohol consumption. DESIGN--Nationwide case-control study. SETTING--Region of New Zealand with 78% of all births during 1987-90. SUBJECTS--Home interviews were completed with parents of 393 (81.0% of total) infants who died from the sudden infant death syndrome in the postneonatal age group, and 1592 (88.4% of total) controls who were a representative sample of all hospital births in the study region. RESULTS--Maternal smoking interacted with infant bed sharing on the risk of sudden infant death. Compared with infants not exposed to either risk factor, the relative risk for infants of mothers who smoked was 3.94 (95% confidence interval 2.47 to 6.27) for bed sharing in the last two weeks and 4.55 (2.63 to 7.88) for bed sharing in the last sleep, after other confounders were controlled for. The results for infants of non-smoking mothers were inconsistent with the relative risk being significantly increased for usual bed sharing in the last two weeks (1.73; 1.11 to 2.70) but not for bed sharing in the last sleep (0.98; 0.44 to 2.18). Neither maternal alcohol consumption nor the thermal resistance of the infants clothing and bedding interacted with bed sharing to increase the risk of sudden infant death, and alcohol was not a risk factor by itself. CONCLUSION--Infant bed sharing is associated with a significantly raised risk of the sudden infant death syndrome, particularly among infants of mothers who smoke. The interaction between maternal smoking and bed sharing suggests that a mechanism involving passive smoking, rather than the previously proposed mechanisms of overlaying and hyperthermia, increases the risk of sudden infant death from bed sharing.

Plagiocephaly and Brachycephaly in the First Two Years of Life: A Prospective Cohort Study

Objectives.Although referrals for nonsynostotic plagiocephaly (NSP) have increased in recent years, the prevalence, natural history, and determinants of the condition have been unclear. The objective of this study was to assess the prevalence and natural history of NSP in normal infants in the first 2 years of life and to identify factors that may contribute to the development of NSP. Methods.Two hundred infants were recruited at birth. At 6 weeks, 4 months, 8 months, 12 months, and 2 years, the head circumference shape was digitally photographed, and head shape was quantified using custom-written software. At each age, infants were classified as cases when the cephalic index was ≥93% and/or the oblique cranial length ratio was ≥106%. Neck rotation and a range of infant, infant care, socioeconomic, and obstetric factors were assessed. Results.Ninety-six percent of infants were followed to 12 months, and 90.5% were followed to 2 years. Prevalence of plagiocephaly and/or brachycephaly at 6 weeks and 4, 8, 12, and 24 months was 16.0%, 19.7%, 9.2%, 6.8%, and 3.3% respectively. The mean cephalic index by 2 years was 81.6% (range: 72.0%–102.6%); the mean oblique cranial length ratio was 102.6% (range: 100.1%–109.4%). Significant univariate risk factors of NSP at 6 weeks include limited passive neck rotation at birth, preferential head orientation, supine sleep position, and head position not varied when put to sleep. At 4 months, risk factors were male gender, firstborn, limited passive neck rotation at birth, limited active head rotation at 4 months, supine sleeping at birth and 6 weeks, lower activity level, and trying unsuccessfully to vary the head position when putting the infant down to sleep. Conclusions.There is a wide range of head shapes in infants, and prevalence of NSP increases to 4 months but diminishes as infants grow older. The majority of cases will have resolved by 2 years of age. Limited head rotation, lower activity levels, and supine sleep position seem to be important determinants.

Dummies and the sudden infant death syndrome.

The association between dummy use and sudden infant death syndrome (SIDS) was investigated in 485 deaths due to SIDS in the postneonatal age group and compared with 1800 control infants. Parental interviews were completed in 87% of subjects. The prevalence of dummy use in New Zealand is low and varies within New Zealand. Dummy use in the two week period before death was less in cases of SIDS than in the last two weeks for controls (odds ratio (OR) 0.76, 95% confidence interval (CI) 0.57 to 1.02). Use of a dummy in the last sleep for cases of SIDS or in the nominated sleep for controls was significantly less in cases than controls (OR 0.44, 95% CI 0.26 to 0.73). The OR changed very little after controlling for a wide range of potential confounders. It is concluded that dummy use may protect against SIDS, but this observation needs to be repeated before dummies can be recommended for this purpose. If dummy sucking is protective then it is one of several factors that may explain the higher mortality from SIDS in New Zealand than in other countries, and may also explain in part the regional variation within New Zealand.

Diagnosis and prevention of hyponatremia at an ultradistance triathlon.

ObjectiveTo evaluate a method of medical care at an ultradistance triathlon, with the aim of reducing the incidence of hyponatremia. DesignDescriptive research. SettingNew Zealand Ironman triathlon (3.8 km swim, 180 km cycle, 42.2 km run). Participants117 of 134 athletes seeking medical care after the triathlon (involving 650 race starters). InterventionsA prerace education program on appropriate fluid intake was undertaken. The number of support stations was decreased to reduce the availability of fluid. A body weight measurement before the race was introduced as a compulsory requirement, so that weight change during the race could be included in the triage assessment. An on-site laboratory was established within the race medical tent. Main Outcome MeasuresNumbers of athletes and diagnoses, including the incidence of symptomatic hyponatremia (defined as symptoms of hyponatremia in association with a pretreatment plasma sodium concentration [Na] < 135 mmol/L); weight changes; and changes in [Na]. ResultsThe common diagnoses in the 117 athletes receiving attention were exercise-associated collapse (27%), musculoskeletal complaints (26%), and dehydration (12%). There was a significant reduction in the number of athletes receiving medical care for hyponatremia, from 25 of the 114 athletes who received care in 1997 (3.8% of race starters) to 4 of the 117 athletes who received care in 1998 (0.6% of race starters). Mean weight change among athletes in the 1998 race was −3.1 kg, compared with −2.6 kg in 1997. ConclusionA preventive strategy to decrease the incidence of hyponatremia, including education on fluid intake and appropriate placement of support stations, was associated with a decrease in the incidence of symptomatic hyponatremia.

ORIGINAL ARTICLE: Accuracy of surface landmark identification for cannula cricothyroidotomy

Cannula cricothyroidotomy is recommended for emergency transtracheal ventilation by all current airway guidelines. Success with this technique depends on the accurate and rapid identification of percutaneous anatomical landmarks. Six healthy subjects underwent neck ultrasound to delineate the borders of the cricothyroid membrane. The midline and bisecting transverse planes through the membrane were marked with an invisible ink pen which could be revealed with an ultraviolet light. Eighteen anaesthetists were then invited to mark an entry point for cricothyroid membrane puncture. Only 32 (30%) attempts by anaesthetists accurately marked the skin area over the cricothyroid membrane. Of these only 11 (10%) marked over the centre point of the membrane. Entry point accuracy was not significantly affected by subjects’ weight, height, body mass index, neck circumference or cricothyroid dimensions. Consultant and registrar anaesthetists were significantly more accurate than senior house officers at correctly identifying the cricothyroid membrane. Accuracy of percutaneously identifying the cricothyroid membrane was poor. Ultrasound may assist in identifying anatomical landmarks for cricothyroidotomy.

Exercise-induced hyponatremia in ultradistance triathletes is caused by inappropriate fluid retention.

ObjectiveTo study fluid and sodium balance during overnight recovery following an ultradistance triathlon in hyponatremic athletes compared with normonatremic controls. Case Control StudyProspective descriptive study. Setting1997 New Zealand Ironman Triathlon (3.8 Km swim, 180 Km cycle, 42.2 Km run). ParticipantsSeven athletes (“subjects”) hospitalized with hyponatremia (median sodium [Na] = 128 mmol L−1). Data were compared with measurements from 11 normonatremic race finishers (“controls”) (median sodium = 141 mmol L−1). InterventionsNone. Main Outcome MeasuresAthletes were weighed prior to, immediately after, and on the morning after, the race. Blood was drawn for sodium, hemoglobin, and hematocrit immediately after the race and the following morning. Plasma concentrations of arginine-vasopressin (AVP) were also measured post race. ResultsSubjects were significantly smaller than controls (62.5 vs. 72.0 Kg) and lost less weight during the race than controls (median −0.5% vs. −3.9%, p = 0.002) but more weight than controls during recovery (−4.4% vs. −0.8%, p = 0.002). Subjects excreted a median fluid excess during recovery (1,346 ml); controls had a median fluid deficit (521 ml) (p = 0.009). Estimated median sodium deficit was the same in subjects and controls (88 vs. 38 mmol L−1, p = 0.25). Median AVP was significantly lower in subjects than in controls. Plasma volume fell during recovery in subjects (−5.9%, p = 0.016) but rose in controls (0.76%, p = NS). ConclusionsTriathletes with symptomatic hyponatremia following very prolonged exercise have abnormal fluid retention including an increased extracellular volume, but without evidence for large sodium losses. Such fluid retention is not associated with elevated plasma AVP concentrations.

Accuracy of surface landmark identification for cannula cricothyroidotomy

Cannula cricothyroidotomy is recommended for emergency transtracheal ventilation by all current airway guidelines. Success with this technique depends on the accurate and rapid identification of percutaneous anatomical landmarks. Six healthy subjects underwent neck ultrasound to delineate the borders of the cricothyroid membrane. The midline and bisecting transverse planes through the membrane were marked with an invisible ink pen which could be revealed with an ultraviolet light. Eighteen anaesthetists were then invited to mark an entry point for cricothyroid membrane puncture. Only 32 (30%) attempts by anaesthetists accurately marked the skin area over the cricothyroid membrane. Of these only 11 (10%) marked over the centre point of the membrane. Entry point accuracy was not significantly affected by subjects’ weight, height, body mass index, neck circumference or cricothyroid dimensions. Consultant and registrar anaesthetists were significantly more accurate than senior house officers at correctly identifying the cricothyroid membrane. Accuracy of percutaneously identifying the cricothyroid membrane was poor. Ultrasound may assist in identifying anatomical landmarks for cricothyroidotomy.

Study of hematological and biochemical parameters in runners completing a standard marathon.

Objective:To study hematological and biochemical parameters prospectively in runners completing a standard 42.2-km marathon run. To determine the incidence of hyponatremia in runners, and whether consumption of nonsteroidal anti-inflammatory medications (NSAIDs) was associated with alterations in serum biochemical parameters. Design:Observational cohort study. Setting:City of Christchurch (New Zealand) Marathon, June 2002. Participants:One hundred fifty-five of the 296 athletes entered in the 2002 City of Christchurch Marathon were enrolled in the study. Main Outcome Measures:Athletes were weighed at race registration and immediately after the race. Blood was drawn postrace for measurement of serum sodium, potassium, creatinine, and urea concentrations and for hematological analysis (hemoglobin concentration, hematocrit, leukocyte distribution). Results:Complete data sets including prerace and postrace weights, and postrace hematological and biochemical analyses were collected on 134 marathon finishers. Postrace serum sodium concentrations were directly related to changes in body weight (P < 0.0001). There were no cases of biochemical or symptomatic hyponatremia. Thirteen percent of runners had taken an NSAID in the 24 hours prior to the race. Mean values for serum creatinine (P = 0.03) and serum potassium (P = 0.007) concentrations were significantly higher in runners who had taken an NSAID. No athlete who had taken an NSAID had a postrace serum creatinine concentration less than 0.09 mmol/L. Ninety-eight percent of runners had a postrace leukocytosis (mean white cell count, 18.97 b/L), of which the major component was a raised neutrophil count (mean neutrophil count, 15.69 b/L). Conclusions:This study found no cases of hyponatremia in runners completing a standard distance marathon. This finding relates to a marathon run under ideal conditions (minimal climatic stress) and in which there were fewer aid stations (every 5 km) than is common in North American marathons (every 1.6 km). Also, aggressive hydration practices were not promoted. Consumption of NSAIDs in the 24 hours prior to distance running was associated with altered renal function.

Ethnic differences in mortality from sudden infant death syndrome in New Zealand.

OBJECTIVES--To examine the factors which might explain the higher mortality from sudden infant death syndrome in Maori infants (7.4/1000 live births in 1986 compared with 3.6 in non-Maori children). DESIGN--A large nationwide case control study. SETTING--New Zealand. 485 infants who died of sudden infant death syndrome were compared with 1800 control infants. There were 229 Maori and 240 non-Maori cases of sudden infant death syndrome (16 cases unassigned) and 353 Maori and 1410 non-Maori controls (37 unassigned). RESULTS--Maori infants had 3.81 times the risk (95% confidence interval 3.06 to 4.76) of sudden infant death syndrome compared with non-Maori infants. The risk factors for sudden infant death syndrome within groups were remarkably similar. When Maori and non-Maori controls were compared the prevalence of many of the known risk factors was higher in Maori infants. In particular, mothers were socioeconomically disadvantaged, younger, and more likely to smoke and their infants were of lower birth weight and more likely to share a bed with another person. Multivariate analysis controlling for potential confounders found that simply being Maori increased the risk of sudden infant death syndrome by only 1.37 (95% CI = 0.95 to 2.01), not statistically significantly different from 1. Population attributable risk was calculated for prone sleeping position, maternal smoking, not breast feeding, and infants sharing a bed with another person. In total these four risk factors accounted for 89% of deaths from sudden infant death syndrome in Maori infants and 79% in non-Maori infants. CONCLUSION--The high rate of sudden infant death syndrome among Maori infants is based largely on the high prevalence in the Maori population of the major risk factors. Other risk factors, not related to ethnicity, probably explain remaining differences between Maori and non-Maori children.

Postnatal Depression in a Community Cohort

A community cohort of 206 European and Maori women completed a questionnaire screening for postnatal depression at 4 weeks postpartum. The prevalence of major depressive disorder amongst the women was 7.8% with a further 13.6% of women experiencing more minor depressive symptoms. Postnatal depression was more likely to occur in women who were single, were less than 20 years old at the birth of their first child, were unhappy with their relationship with their partner, had a history of previous psychiatric hospitalisation, and were Maori. Women who were depressed were more likely to show a lack of enjoyment of and less positive attitude towards their infant. The study highlights the value of screening for postnatal depression with a simple questionnaire, as few depressed women would have been otherwise recognised.