PubMed HealthSearch

Biomedical subjects

A J Macnab

Publications and source records attributed to A J Macnab.

At least 19 recordsLinked to original sources

Successful treatment of dinitrophenol poisoning in a child.

BACKGROUND: Poisoning with agricultural toxins is well known in the adult environment, but is rarely seen in children. Vancouver, British Columbia, borders on a large agricultural area, and the British Columbia Children's Hospital is the provincial referral center for major pediatric emergencies. In our experience, children from farming communities are vulnerable to a range of agriculturally related injuries, and exposure to toxic chemicals requiring hospitalization is not rare. METHODS: This is a case report with literature review. RESULTS: A child presenting in a coma proved later to have been exposed to a toxic agent. The agent, dinitrophenol, is a widely used agricultural herbicide and insecticide. The diagnosis resulted from a detailed history and physical examination, which revealed symptoms and signs that suggested poisoning. A search of the farm resulted, and the parents located open dinitrophenol containers. The toxic effects of dinitrophenol described in adults by Poison Control matched those present in the child, and specific treatment interventions existed that could be implemented to positively influence outcome. CONCLUSIONS: Awareness of the possibility of exposure to dinitrophenol is required, as death can result from exposure, and milder cases may go unrecognized. Appropriate treatment can improve outcome. Injuries with toxic agricultural agents are wholly preventable if the materials are handled appropriately in the farm environment, and parents whose children live on or visit farms are aware of the risks involved and take appropriate precautions.

Adult

Midazolam premedication delays recovery after propofol without modifying involuntary movements.

Midazolam has GABAergic effects in children that may modify propofol-induced involuntary movements, yet delay recovery. In a double-blind, randomized study, 24 children (2-7 yr of age, ASA physical status I or II) undergoing short surgical procedures received midazolam 0.5 mg/kg (Group M) or placebo (Group P) per os 20-30 min before propofol anesthesia (5 mg/kg intravenously followed by an infusion). Blind observers scored sedation and anxiety levels (scale 1-4) before premedication, at separation from parents, and at induction of anesthesia. Induction and emergence were videotaped, and body movements were recorded. During recovery, times to eye opening and maximum Steward (SS = 6) and Vancouver Sedative Recovery (VSRS = 22) scores were noted. Parents were questioned about side effects that may have occurred during the following week. Both groups were similar in age, sex, weight, timing of premedication, propofol dose, and duration of surgery. The incidence of involuntary movements did not differ between groups but was higher at induction (79%) than on emergence (25%) (P < 0.05). Anxiety and sedation scores were similar in Group P and Group M, but recovery took longer after midazolam, with eye opening (mean +/- SD) 24 +/- 7 vs 43 +/- 18 min, maximum SS (median and range) 27 (13-37) vs 55 (24-138) min, and maximum VSRS 51 (30-100) vs 80 (50-130) min. Children returned to normal activity in 1 (0-5) day, and none exhibited neurological complications. We conclude that an oral premedicant dose of midazolam prolongs recovery from anesthesia in children without affecting dystonic movements after propofol.

Administration, Oral

Comparison of 13 published cytochrome c oxidase near-infrared spectroscopy algorithms.

Conflicting patterns of change in cytochrome c oxidase (Cyt a,a3) redox status have been obtained between different near-infrared spectrophotometers when making measurements during tissue ischaemia. This study identifies possible sources of error that could be the cause of the discrepancy. A single set of optical density data was repeatedly analysed using each of the absorption spectra from 13 publications. In addition, changes in Cyt a,a3 redox status were calculated from the data set using three numerical methods, five computer software routines, eight displacements in wavelength, and ten incremental changes in the value of absorption or concentration coefficients. All Cyt a,a3 absorption spectra resulted in algorithms yielding similar patterns of change, regardless of the numerical method or computer process employed (0.9996 average r2, coefficient of correlation). However, a significantly different pattern of change in Cyt a,a3 redox status, resembling that reported by Piantadosi [Piantadosi CA (1993) Methods Toxicol. 2:107-126], was obtained when either the wavelengths, and/or the absorption values were altered to simulate erroneous values. This implies that all of the present algorithms are valid (including those of Piantadosi), but that microchip encoding errors may exist in the instrument used by Piantadosi.

Adult

Midazolam following open heart surgery in children: haemodynamic effects of a loading dose.

Our objective was to establish the safety and effectiveness of a loading dose of midazolam for postoperative sedation of children recovering from open heart surgery; a prospective randomized placebo-controlled double-blind study was done with subjects randomized to three groups according to loading dose. I = 0.08 mg.kg-1; II = 0.04 mg.kg-1; and III = 0.00 mg.kg-1 (placebo). An open label continuous midazolam infusion protocol followed. Haemodynamic parameters were monitored. The study was discontinued following an adverse event involving the 23rd subject. When data for all 23 subjects were combined, there was a mean decrease of 10% in blood pressure (BP) 30 min after the loading dose (P < 0.001). Heart rate change was less significant. Clinicians identified four hypotensive episodes as temporally associated with the midazolam load, two each in Groups I (0.08 mg.kg-1) and III (placebo). One subject in Group I (the 23rd) became hypotensive within five min of receiving the loading dose, had a difficult clinical course and died four weeks postoperatively. We cannot conclude that the loading dose of midazolam had any systematic haemodynamic effect in our study population. Although the clinical course of the 23rd subject suggests a subset of more susceptible children (those who receive opioid analgesia with midazolam, are volume-restricted, and/or undergo more complex forms of surgical correction), many critical care patients are inherently physiologically unstable, and concluding clinically that blood pressure fluctuation is drug related may be erroneous.

Blood Pressure

Demographics of alpine skiing and snowboarding injury: lessons for prevention programs.

OBJECTIVE: To establish the demographics of ski injury in relation to age, gender, and perceived cause during a representative season to identify potential injury prevention strategies. SETTING: Blackcomb Mountain, a world class ski resort in British Columbia, Canada. METHODS: Data were collected from the lift ticket records and from ski patrol injury reports for one season, November to May 1991-2. RESULTS: There were 720,066 skier and snowboarder day visits counted by the mountain's lift ticket records, with a total of 2,092 injury reports (incidence 2.91 per 1,000 day visits). Of those with significant injuries (those requiring physician care), 1,210 (58%) were male. The highest injury rate was among children (age 7-12) and teens (age 13-17) with incidences of 3.18 and 3.34 significant injuries per 1,000 skier days, respectively. Head and face injuries constituted 17% and 22% of injuries, respectively in these groups. Overall 22% of head and face injuries were severe enough to cause loss of consciousness or clinical signs of concussion. This was the body region injured most frequently in males. For females over 7 years of age, the knee was the most common site of injury. For youths, the incidence of injuries during school organized activities was 25% higher than during other outings. CONCLUSIONS: The vulnerability of school group participants suggests special education is warranted. The high incidence of head injuries, particularly among young males, needs to be addressed. In light of the high proportion of this group who already wear helmets, the role of helmets in both protection and possible causation of head injury needs objective research.

Adolescent

Oximeter reliability in a subzero environment.

BACKGROUND: Pulse oximeters optimize care in the pre-hospital setting. As British Columbia ambulance teams often provide care in subzero temperatures, we conducted a study to determine the reliability of 3 commercially-available portable oximeters in a subzero environment. NULL HYPOTHESIS: We hypothesized that there is no significant difference between SaO2 readings obtained using a pulse oximeter at room temperature and a pulse oximeter operating at sub-zero temperatures. METHODS: Subjects were stable normothermic children in intensive care on Hewlett Packard monitors (control unit) at room temperature. The test units were packed in dry ice in an insulated bin (temperature - 15 degrees C to -30 degrees C) and their sensors placed on the subjects, contralateral to the control sensors. Data were collected simultaneously from test and control units immediately following validation of control unit values by co-oximetry (blood gas). RESULTS: No data were unacceptable. Two units (Propaq 106EC and Nonin 8500N) functioned well to < -15 degrees C, providing data comparable to those obtained from the control unit (p < 0.001). The Siemens Micro O2 did not function at the temperatures tested. CONCLUSIONS: Monitor users who require equipment to function in subzero environments (military, Coast Guard, Mountain Rescue) should ensure that function is reliable, and could test units using this method.

Analysis of Variance

Effective interventions for nearly drowned children.

Near-drowning, one of the great tragedies in emergency pediatrics, is largely preventable. It generates particular concern and frustration among those who must treat its victims and their families. Should every drowned child be resuscitated? What treatment will minimize the risk of secondary brain injury?

Adolescent

The Vancouver sedative recovery scale for children: validation and reliability of scoring based on videotaped instruction.

We originally developed and tested the Vancouver Sedative Recovery Scale (VSRS) to measure recovery from sedation following paediatric open heart surgery and reported excellent clinical inter-observer reliability. We now report a new study using videotape instruction of novice raters and videotaped case examples to determine whether the instruction produces adequate skill with the VSRS. Inter-rater reliability was assessed using videotapes of 16 children across a range of ages (six months to six years), and all levels of sedation (unresponsive to fully awake). Variably randomized subsets of six of the 16 test cases were randomly assigned to be rated by each of 16 video-instructed ICU staff volunteers, according to a balanced incomplete block design, such that every pair of raters assessed two children in common. The validity of the ratings from the video-instructed raters was assessed by comparison with "gold standard" scores from two experts who rated all 16 children clinically as the test cases were videotaped. The experts were in agreement themselves (intraclass correlation of 0.976). The correlation between the novice scores (average of six ratings per video) and the live clinical scores (average of two expert ratings) was 0.977 over the 16 test cases. On average, the mean expert rating was slightly higher, but the difference was negligible. (The differences between the mean ratings of the experts and novices for 13 of the 16 videos are very close to zero, while the other three differences, from technically less good videos, are two standard deviations away from zero). The VSRS, video instruction method and incomplete block design may be of use to other clinicians and investigators.

Anesthesia Recovery Period

Carbamazepine poisoning in children.

Carbamazepine poisoning in children remains a significant problem for the emergency physician. We report 16 cases of toxicity at British Columbia Children's Hospital and discuss presenting symptoms, treatment, and hospital course. Pharmacology, drug interactions, resulting in carbamazepine toxicity, and treatment guidelines are summarized.

Adolescent

Paediatric inter-facility transport: the parents' perspective.

A telephone survey was conducted to evaluate the impact on families of inter-facility paediatric transport to a tertiary care centre. The 54 families who responded were almost unanimous in their appreciation of the transport service and the expertise of the attendants. However, many experienced problems, including finances, child care, travel arrangements and accommodation. Most problems were encountered by those who did not accompany the child in the transport vehicle, lived at a distance so that they could not commute and did not use hospital accommodation. Further research is suggested to assess the extent of the problems families face and to determine appropriate solutions.

Adolescent

A research tool for measurement of recovery from sedation: the Vancouver Sedative Recovery Scale.

The need for a research tool to measure recovery from sedation was identified during the design phase of a study investigating sedative protocols following open heart surgery in children. A thorough review of the literature failed to show any scales that measure degree of sedation in children at various times after initial awakening. The Vancouver Sedative Recovery Scale (VSRS) was developed through an iterative process during which we identified numerous indicators of levels of alertness among sedated children, and then determined the applicability and face validity of these indicators. The VSRS evaluated in this study consists of 12 distinct items that encompass three categories of indicators (response; eye appearance and function; and body movement). Total possible VSRS scoring ranges from 0 to 22 (higher score indicating more alert) because some of the 12 items have more than two rating levels. The VSRS was administered to 82 pediatric intensive care unit and postanesthesia recovery patients, with each patient assessed simultaneously by at least two observers. Internal consistency as measured by Cronbach's alpha was excellent: 0.85. Interobserver agreement or reliability as measured by intraclass correlation was also very high: 0.90; and for individual items Cohen's kappa ranged from 0.65 to 0.89. We consider the VSRS to be a good beginning in our effort to quantify level of alertness after sedation in the pediatric patient population.

Anesthesia Recovery Period

Hypospadias after assisted reproduction incorporating in vitro fertilization and gamete intrafallopian transfer.

OBJECTIVE: To determine incidence of hypospadias in infants born as a result of assisted reproductive technology (ART). DESIGN: Prospective data collection. SETTING: Parents with various forms of infertility attended an in-hospital in vitro fertilization program. PATIENTS: Two of the 53 male infants, conceived as a result of ART over a 3-year period, were born with hypospadias. INTERVENTIONS: Patient no. 1 underwent follicular stimulation (17 ampules of human menopausal gonadotropin (hMG), followed by 10,000 IU of human chorionic gonadotropin (hCG) 60 hours after the last hMG). Patient no. 2 underwent follicular stimulation with clomiphene citrate 100 mg/d from days 3 to 7, followed by 14 ampules of hMG starting day 6, and 10,000 IU of hCG 30 hours after her last hMG. MAIN OUTCOME MEASURES: All infants were examined in the immediate postpartum period for congenital anomalies. RESULTS: Infant no. 1, one of a set of dizygotic twins, had penoscrotal hypospadias, with normal renal sonogram and chromosomal studies. Infant no. 2 had glandular hypospadias with the urinary meatus displaced to the border of the glans. CONCLUSION: This high incidence raises concern about possible links between assisted reproduction and hypospadias.

Adult

Cardiac anomalies complicating congenital contractural arachnodactyly.

A newborn boy with congenital contractural arachnodactyly (CCA) was found to have an atrial septal defect, ventricular septal defect, patent ductus arteriosus, and aortic arch anomalies. These resulted in congestive failure but subsequent progressive dilatation of both great arteries and development of aortic regurgitation were associated with eventual cardiorespiratory failure and death at 11.5 months. Others have noted that cardiac anomalies in CCA may be comparable with those of infantile Marfan's syndrome. Our case further extends the spectrum of cardiac abnormalities in CCA and substantiates that there is overlap with infantile Marfan's syndrome. This fact and our literature review suggest that early and complete cardiac assessment is necessary for appropriate management and evaluation of prognosis in any newborn infant with findings suggestive of either condition.

Abnormalities, Multiple

Optimal escort for interhospital transport of pediatric emergencies.

The charts of 130 seriously ill or injured children transported to tertiary level intensive care were examined to determine the incidence of secondary insults incurred, as a function of escort training. Of all insults incurred, approximately 8% occurred with specialized pediatric transport escorts who were accompanied by a tertiary care physician (Group III, n = 52); 20% with specialized pediatric transport escorts alone (Group II, n = 44); and 72% with escorts who had not received specialized pediatric transport training (Group I, n = 34). Based on our results, we recommend that all transport coordinators review the qualifications and experience of their transport team members and all potential escorts to assess their ability to provide optimal care for the children they transport, particularly during long journeys, transfer by air, and when serious illness or injury is involved.

Brain Injuries

Oximetry in children recovering from deep hypothermia for cardiac surgery.

Although pulse oximetry is a potentially useful diagnostic tool in the treatment of children after major open heart surgery, there are concerns regarding its reliability for measuring oxygen saturation (SaO2) in hypothermic or low perfusion states. To test pulse oximeter reliability in children under these conditions, our study compared 187 SaO2 pulse oximeter readings (Biox 3700) with simultaneous hemoximeter (OSM2, Radiometer) readings from 56 children rewarming after open heart surgery. Ages ranged from 4 months to 18 yr; temperatures ranged from 23.5 degrees to 38 degrees C (toe) and 31.3 degrees to 40.8 degrees C (core). The mean pulse oximeter SaO2 reading was 94.90% (SD 7.18, range 54% to 100%), mean hemoximeter reading was 96.07% (SD 7.06; minimum 54%; maximum 100%). The correlation between the readings was high (r = .88, p less than .005), and was not affected by low core temperature. When oximeter and cardiac monitor pulse rates coincided, the oximeter SaO2 value was within +/- 5% (p less than .05). We conclude that the Biox 3700 oximeter is reliable for noninvasive SaO2 monitoring in mild to moderately hypothermic children after open heart surgery, particularly when oximeter and cardiac heart rates coincide. Further studies are needed to confirm our findings in children with core temperatures less than 31.3 degrees C, and when other oximeters are used.

Adolescent