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Biomedical subjects

Geoffrey K Isbister

Publications and source records attributed to Geoffrey K Isbister.

At least 55 records · Page 3Linked to original sources
PubMed2004

Use of high performance liquid chromatography to measure tetrodotoxin in serum and urine of poisoned patients.

Tetrodotoxin (TTX) poisoning is an infrequent but important problem in South-eastern Asia. Despite it being a considerable public health issue in some countries and its potential lethality there continues to be no readily available method for measuring TTX in urine or serum. Previously published methods have used immunoaffinity chromatography, or the conversion of TTX to its C9-base derivative for measurement by mass spectrometry. A simple and reproducible method was developed using solid phase extraction cartridges to clean up serum and urine samples from TTX-poisoned patients, and the subsequent analysis of the samples by high performance liquid chromatography with post-column derivatisation and fluorescence detection. Minimum quantifiable concentrations of TTX were 5 and 20 ng/ml for serum and urine, respectively. Precision and accuracy of the assay were 13 and 15%, respectively. The standard curves were linear in the range of 20-300 ng/ml for urine and 5-20 ng/ml for serum. TTX was quantified in six samples of urine and six samples of serum from seven patients who ingested common toadfish and had clinical effects consistent with TTX poisoning. TTX was detected in all urine samples but in only one serum sample. Using this method confirmation of TTX poisoning will be far simpler and readily available. A 24 h urine collection in the period immediately following poisoning is likely to be the most sensitive test for TTX poisoning. With appropriately collected and timed serum and urine specimens it will be possible to properly define the pharmacokinetics of TTX in humans.

Calibration↗
PubMed2004

Prospective study of centipede bites in Australia.

BACKGROUND: There are limited reports of definite bites by centipedes with expert identification, which are required for attribution of particular clinical effects to different species. OBJECTIVE: To describe the clinical effects of centipede bites in Australia. METHODS: Prospective study of calls regarding centipede exposures to a state poison information center, from December 2000 to March 2002. Information collected included demographics, details of the exposure, local effects, systemic effects, and treatment. Collected centipedes were identified by an expert. All subjects were followed until clinical effects had resolved. RESULTS: Of 48 centipede exposures, 3 were centipede ingestions with no adverse effects and one was a contact reaction to the centipede that resulted in erythema and delayed itchiness. Of 44 definite centipede bites, the centipedes obtained and formally identified in 14 cases were from the genera Scolopendra (5), Cormocephalus (6), and Ethmostigmus (3). Of these 14 bites, 13 occurred distally (hands or feet). Pain occurred in all 14 cases and was severe in 7 patients. Redness/red mark occurred in 53%, swelling/raised area in 43%, and itchiness in 14%. No systemic effects were reported. Ethmostigmus spp. and Scolopendra spp. caused more severe effects. Of the bites, 57% occurred indoors and 50% at night. Treatment consisted of supportive measures including ice packs and simple analgesia, and 4 patients reported pain relief after immersing the bite area in hot water. Similar clinical effects were reported in the other 30 definite centipede bites. CONCLUSIONS: Australian centipede bites cause minor effects with moderate to severe pain, associated with localized swelling and erythema in bites by the genera Ethmostigmus and Scolopendra. Hot water immersion may potentially be beneficial for centipede bites. The genus Scolopendra occurs worldwide and the results may have international applicability.

Adolescent↗
PubMed2004

Australian wolf spider bites (Lycosidae): clinical effects and influence of species on bite circumstances.

BACKGROUND: Necrotic arachnidism continues to be attributed to wolf spider bites. This study investigates the clinical effects of bites by wolf spiders in Australia (family Lycosidae). METHODS: Subjects were recruited prospectively from February 1999 to April 2001 from participating emergency departments or state poison information centers. Subjects were included if they had a definite bite by a wolf spider and had collected the spider, which was later identified by an arachnologist. Spiders were identified to the lowest taxonomic level possible and cephalothorax width was measured to correlate bite effects and spider size. RESULTS: There were 45 definite wolf spider bites (23 male and 22 female patients; age range 1 to 69 years, median age 28 years). Species level identifications (14 species) were possible for 31 of 43 spiders belonging to seven different generic groupings. Most bites were by spiders from four generic groupings, Tasmanicosa (including 'Lycosa') (15), Venatrix (8), Venator (10), and Hogna (7). Bites occurred more commonly in south-eastern Australia and occurred throughout the year, with 7 bites (16%) in late autumn or winter. In 7 cases (16%) the person was swimming in or cleaning a pool. Seventy-two percent of bites occurred on distal parts of limbs. Pain occurred in all bites and was severe in 11 cases (24%), with a median duration of 10 min (IQR: 2-60 min). Other effects included puncture marks/bleeding (33%), swelling (20%), redness (67%), and itchiness (13%). Minor systemic effects occurred in three patients (7%): nausea (two), headache (one) and malaise (one). There were no cases of necrotic ulcers [0%; 97.5% CI 0-8%]. Tasmanicosa spider bites caused significantly more itchiness and redness, and large spiders (>5 mm) more often caused severe pain and left fang marks. CONCLUSION: Wolf spider bites cause minor effects, no more severe than most other spiders, and do not appear to cause necrotic ulcers. The effects are likely to be due to mechanical injury, although minor local envenomation occurs with Tasmanicosa bites.

Adolescent↗
PubMed2004

Relative toxicity of selective serotonin reuptake inhibitors (SSRIs) in overdose.

BACKGROUND: Selective serotonin reuptake inhibitors (SSRIs) have increasingly replaced tricyclic antidepressants (TCAs) in the treatment of depression. They appear to be safer in overdose, but there is little information on their spectrum of toxicity in overdose, or relative toxicity of each agent. OBJECTIVE: To determine the effect of SSRIs in overdose, as a group, and the relative toxicity of five different SSRIs. METHODS: A review of consecutive SSRI poisoning admissions to a single toxicology unit. Outcomes examined were length of stay [LOS], intensive care [ICU] admission rate, coma, seizures, electrocardiographic [ECG] abnormalities, and presence of serotonin syndrome [SS]. Logistic regression was used to model the outcome QTc >440 msec. RESULTS: There were 469 SSRI poisoning admissions analyzed after exclusions. The median LOS for all SSRI overdose admissions was 15.3 h (IQR: 10.5-21.3) and 30 of 469 (6.4%; 95% CI 4.3-9.0%) cases were admitted to ICU. The incidence of seizures was 1.9% and coma was 2.4%. Serotonin syndrome occurred in 14% of overdoses. Comparison of median QTc intervals of the five SSRIs was significantly different (p=0.0002); citalopram (450 IQR: 436-484) was individually different to fluoxetine (p=0.045), fluvoxamine (p=0.022), paroxetine (p=0.0002), and sertraline (p=0.001). The proportion of citalopram overdoses with a QTc >440 msec was 68%, differing significantly from sertraline (adjusted OR: 5.11 95% CI 2.32-11.27). Comparison of median QT intervals of the five SSRIs was statistically different (p=0.026); citalopram (400 IQR: 380-440) was individually different from sertraline (p=0.023). CONCLUSIONS: This study shows SSRIs are relatively safe in overdose despite serotonin syndrome being common. The exception was citalopram, which was significantly associated with QTc prolongation. We believe that cardiac monitoring should be considered in citalopram overdose, particularly with large ingestions and patients with associated cardiac disease.

Adolescent↗
PubMed2004

Aspiration pneumonitis in an overdose population: frequency, predictors, and outcomes.

OBJECTIVE: To characterize the frequency of aspiration pneumonitis in an unselected population of overdose patients and, further, to identify factors that predispose to aspiration pneumonitis and the outcomes of patients with aspiration pneumonitis compared with those without. DESIGN: Retrospective cohort study. SETTING: Toxicology unit of a tertiary referral hospital. PATIENTS: All poisoning admissions. MEASUREMENTS AND MAIN RESULTS: A total of 71 of 4,562 poisoning admissions to the Hunter Area Toxicology Service between January 1997 and October 2002 had definite aspiration pneumonitis (1.6%; 95% confidence interval, 1.2-2.0). Older age, Glasgow Coma Score of <15, spontaneous emesis, seizures, delayed presentation to hospital, and ingestion of tricyclic antidepressants were associated with an increased risk of aspiration pneumonitis. Paracetamol poisoning and female sex were associated with a decreased risk of aspiration pneumonitis with univariate analysis. Ingestion of alcohol, benzodiazepines, antipsychotics, and administration of activated charcoal were not associated with aspiration pneumonitis. A logistic regression model for predicting aspiration pneumonitis contained seven predictors: age, sex, Glasgow Coma Score of <15 (odds ratio, 3.14; 95% confidence interval, 1.87-5.27), emesis (odds ratio, 4.17; 95% confidence interval, 2.44-7.13), seizure, tricyclic antidepressant ingestion, and time from ingestion to presentation (delay of >24 hrs [odds ratio, 4.42; 95% confidence interval, 2.42-8.10]). The mortality for patients with aspiration pneumonitis was 8.5% compared with 0.4% for those without (odds ratio, 23; 95% confidence interval, 9-60; p <.0001), and they had a significantly higher intensive care unit admission rate. The median length of stay of patients with aspiration pneumonitis was 126 hrs (interquartile range, 62-210 hrs) compared with 14.7 hrs (interquartile range, 7-23 hrs) in patients without (p <.0001). CONCLUSIONS: Our study has shown a number of risk factors in overdose patients that are associated with aspiration pneumonitis that may allow the early identification of these patients for appropriate observation and management. Patients with aspiration pneumonitis have a significantly increased mortality and length of stay in the hospital.

Adult↗
PubMed2004

Alprazolam is relatively more toxic than other benzodiazepines in overdose.

AIMS: To describe alprazolam poisoning and the relative toxicity of alprazolam compared with other benzodiazepines. METHODS: A database of consecutive poisoning admissions to a regional toxicology service was searched to identify consecutive benzodiazepine deliberate self poisonings, which were coded as alprazolam, diazepam or other benzodiazepine. Major outcomes used were length of stay (LOS), intensive care (ICU) admission, coma (GCS < 9), flumazenil administration and requirement for mechanical ventilation. Prescription data were obtained for benzodiazepines for the study period. RESULTS: There were 2063 single benzodiazepine overdose admissions: 131 alprazolam overdoses, 823 diazepam overdoses and 1109 other benzodiazepine overdoses. The median LOS for alprazolam overdoses was 19 h which was 1.27 (95% CI 1.04, 1.54) times longer compared with other benzodiazepines by multiple linear regression. For patients with alprazolam overdoses, 22% were admitted to ICU which was 2.06 (95% CI 1.27, 3.33) times more likely compared with other benzodiazepines after multivariate analysis adjusting for age, dose, gender, time to ingestion and co-ingested drugs. Flumazenil was administered to 14% of alprazolam patients and 16% were ventilated, which was significantly more than for other benzodiazepine overdoses (8% and 11%, respectively). Twelve percent of alprazolam overdoses had a GCS < 9 compared with 10% for other benzodiazepines. From benzodiazepine prescription data, total alprazolam prescriptions in Australia increased from 0.13 million in 1992 to 0.41 million in 2001. Eighty five percent of prescriptions were for panic disorder, anxiety, depression or mixed anxiety/depression. CONCLUSIONS: Alprazolam was significantly more toxic than other benzodiazepines. The increased prescription of alprazolam to groups with an increased risk of deliberate self poisoning is concerning and needs review.

Adolescent↗
PubMed2004

Clinical effects of exposure to the White-stemmed gum moth (Chelepteryx collesi).

BACKGROUND: The White-stemmed gum moth (Chelepteryx collesi) can be found in eastern Australia. The clinical effects of injuries caused by its many spine-like hairs are poorly defined and concern about the numerous hairs that remain embedded following contact with the cocoon have led to heroic means of removal. OBJECTIVE: To examine the clinical effects of injuries by the caterpillar or cocoon of the White-stemmed gum moth. METHODS: Prospective observational study of caterpillar injuries from calls to the New South Wales Poisons Information Centre. Cases resulting from C. collesi exposure were included for analysis. Caterpillars and cocoons were expertly identified where available and a follow-up consultation of all patients was conducted. Information was collected on the circumstances of exposure, local and systemic effects and treatment. RESULTS: From the 26 included cases, seven had confirmed caterpillar contact (all children aged 1-11), six had confirmed cocoon contact and 13 had exposures consistent with C. collesi, but no caterpillar was caught. All cases occurred in summer. Of 13 confirmed exposures there was no difference between caterpillars and cocoons, and these were considered together. Affected areas were hands, feet, or both, following C. collesi being handled or trodden on. Pain was reported in all 13 cases, one with severe pain. In 10 cases pain duration was < 60 min. Six subjects had more than 100 hairs embedded (small black dots). In three cases, the hairs were surrounded by swelling and yellow discolouration. Despite the attempted removal of multiple hairs, they remained embedded for prolonged periods but caused no sequelae. CONCLUSION: The clinical effects of the White-stemmed gum moth were minor with local pain. Although hairs remained in all cases, they caused no problems. Complete removal of hairs is neither possible nor necessary, and painful and invasive methods should be avoided.

Adolescent↗
PubMed2004

Developing a decision tree algorithm for the diagnosis of suspected spider bites.

OBJECTIVE: To develop a diagnostic algorithm (decision tree) to improve the ability to identify or predict medically important spider bites (funnel-web and redback spiders) from information about the circumstances and initial clinical effects of spider bites. METHODS: A dataset of definite spider bites with expert identification of all spiders was used from a previous Australia-wide prospective study. Spider bites were categorized as: big black spider (BBS), redback spider (RED) and other spider (OTH). Big black spider included funnel-web spiders (most medically significant), but also other spiders of similar appearance. Fifteen predictor variables were based on univariate analysis from previous studies and clinical experience. They included information about the circumstances and early clinical effects of bites. The data were analyzed using CART (Classification and Regression Trees), a 'decision tree' algorithm used to create a tree-like structure to describe a data set. RESULTS: Of 789 spider bites there were 49 (6.2%) bites by BBS, 68 (8.6%) bites by RED and 672 (85.2%) bites by OTH. A decision tree was developed that included six predictor variables (fang marks/bleeding; state/territory; local diaphoresis; month; time of day; and proximal or distal bite region). The decision tree accurately classified 47 out of the 49 (96%) BBS, and no funnel-web spiders were incorrectly classified (100% sensitivity). Two hundred and forty-four of 789 were classified as OTH and included no BBS. CONCLUSIONS: A decision tree based on a small amount of information about the circumstances and early clinical effects of spider bites safely predicted all funnel-web spider bites. Application of this algorithm would allow the early institution of appropriate treatment for funnel-web spider bites and the immediate discharge of 31% as other spider bites (reassurance only).

Algorithms↗
PubMed2004

Arsenic trioxide poisoning: a description of two acute overdoses.

Arsenic is a traditional poison that has a history extending back into ancient times, as a medicinal agent, a homicidal poison and more recently in deliberate and unintentional self-poisoning. We report two cases of acute poisoning with an unwettable formulation of arsenic trioxide. Both patients had early gastrointestinal toxicity and were treated with early whole bowel irrigation (WBI). Chelation therapy with dimercaptosuccinic acid (dimercaptosuccinate, DMSA) was commenced within 24 hours and serial blood and urine arsenic concentrations were measured. Neither patient suffered any adverse outcome in spite of very high blood and urine concentrations of arsenic. Arsenic quantification in blood, urine and faeces suggested that enhanced gastrointestinal decontamination was minimally effective for decontamination and that DMSA for at least two weeks was required.

Acute Disease↗
PubMed2003

White-tail spider bite: a prospective study of 130 definite bites by Lampona species.

OBJECTIVE: To investigate the circumstances and clinical effects of bites by white-tail spiders, including the two species Lampona cylindrata and L. murina commonly encountered by humans, and the incidence of necrotic lesions. DESIGN: Prospective cohort study of definite white-tail spider bites. Cases were only included if there was a clear history of bite, the spider was caught and was identified by an expert. SETTING: Calls to Australian poisons information centres and emergency departments. PATIENTS: 130 patients with a definite bite by a white-tail spider from February 1999 to April 2002. RESULTS: There were 79 bites by L. cylindrata and 51 by L. murina. Bites occurred in warmer months, 95% indoors and 75% between 16: 00 and 08: 00. The activity at the time of the bite was characteristic and the spider was encountered between bedclothes, towels or clothing. 25% of bites occurred on distal limbs. Pain/discomfort occurred in all cases, and was severe in 27%. Other effects included puncture marks (17%), redness/red mark (83%) and itchiness (44%). Systemic effects occurred in 9%. There were no cases of necrotic ulcers (97.5% CI, 0-2.8%) or confirmed infections. Median duration of effects was 24 hours (interquartile range, 1-168 hours). There were three distinct clinical patterns: pain only (21%), pain and red mark for < 24 hours (35%), and a persistent painful or irritating red lesion (44%). CONCLUSIONS: Bites by Lampona spp. cause minor effects in most cases, or a persistent painful red lesion in almost half the cases. White-tail spider bites are very unlikely to cause necrotic ulcers, and other diagnoses must be sought.

Adolescent↗
PubMed2003

Latrodectism: a prospective cohort study of bites by formally identified redback spiders.

OBJECTIVE: To determine the spectrum of severity and early diagnostic predictors of redback spider bites (Latrodectus hasselti), and to examine the effect of intramuscular redback antivenom. DESIGN AND SETTING: Prospective cohort study of calls to New South Wales, Queensland and Western Australian poisons information centres and presentations to Royal Prince Alfred Hospital and Royal Darwin Hospital emergency departments. PATIENTS: 68 people with definite redback spider bites in which the spider was immediately collected and expertly identified (1 February 1999 to 30 April 2002). INTERVENTIONS: Intramuscular redback spider antivenom in a smaller cohort of hospitalised patients. MAIN OUTCOME MEASURES: Pain severity and duration, local effects and systemic envenomation (effects, prevalence, and persistence > 24 hours). RESULTS: The median duration of effects was 48 hours (interquartile range, 24-96 hours). Pain occurred after all bites and was severe in 42 (62%). Forty-five patients (66%) had pain lasting longer than 24 hours, and 22 (32%) were unable to sleep because of pain. Systemic effects occurred in 24 (35%). Increasing pain over one hour occurred in 37 cases (54%), and local/regional diaphoresis in 23 (34%); both these features were highly predictive of L. hasselti bites compared with bites of other spiders. One of six patients treated with intramuscular antivenom (17%) had no pain at 24 hours, compared with two of 17 untreated patients (12%) (difference, 5%; 95% CI, -36% to +64%; P = 0.95). There was no difference in duration of systemic effects with antivenom administration. CONCLUSIONS: Most redback spider bites cause severe and persistent effects. Intramuscular antivenom appears to be less effective than previously thought and its use by this route needs review.

Adolescent↗
PubMed2003

Bupropion poisoning: a case series.

OBJECTIVE: To investigate the toxicity of bupropion hydrochloride in deliberate self-poisoning in adults and accidental ingestion by children. DESIGN AND SETTING: Prospective study of cases identified from calls to the New South Wales Poisons Information Centre (NSW PIC), with follow-up through hospital medical records. PARTICIPANTS: Patients with bupropion poisoning managed in hospital, about whom the NSW PIC was contacted for advice, from 1 November 2000 to 31 July 2001 (59 adults and 10 children). MAIN OUTCOME MEASURES: Clinical effects, adverse outcomes (including seizures and death) and treatment. RESULTS: 45 of the 59 adults were followed up (76%), 19 of whom had taken bupropion alone. Major clinical effects of bupropion included sinus tachycardia (83%), hypertension (56%), seizures (37%), gastrointestinal symptoms (37%) and agitation (32%). Seizures were dose-dependent, with those having seizures ingesting a significantly higher median dose (P = 0.02). All seizures were brief and self-limiting. 29 patients received decontamination therapy. 10 patients required pharmacological sedation, 10 were admitted to intensive care and six were intubated. None died. Eight of 10 accidental ingestions by children were followed up (80%); one child had symptoms (vomiting and hallucinations). CONCLUSIONS: Bupropion overdose caused significant clinical effects in adults, but few in children.

Accidents, Home↗
PubMed2003

Prospective study of definite caterpillar exposures.

Exposure to caterpillars results in a variety of clinical effects depending on the species involved. The aim of this study was to describe the clinical effects from caterpillar exposures within Australia. Cases were recruited prospectively from calls to a poison information centre. Subjects were included if they had a definite exposure and they had collected the caterpillar or cocoon. The caterpillars were identified to genus and species level where possible. There were 36 included cases: two were contact exposures to caterpillar contents, one was an ingestion of a caterpillar and the remaining 33 patients had definite reactions from caterpillar or cocoon exposure. There were five families of caterpillars identified in the study: Arctiidae, Limacodidae, Anthelidae, Lymantriidae and Sphingidae, many of which occur worldwide. Clinical effects ranged from severe pain to an urticarial response depending on the species involved. There were no adverse effects following ingestion in this study. Treatment consisted primarily of removal of the caterpillar or cocoon. Other treatment measures consisted of symptomatic treatment such as ice packs and antihistamines. This is the first prospective study of caterpillar exposures within Australia and demonstrates that exposures can result in a variety of reactions depending on the family and species involved.

Adolescent↗
PubMed2003

Acute conjunctival inflammation following contact with squashed spider contents.

PURPOSE: To report the effects to the eye following contact with spider contents. DESIGN: Observational case report. METHODS: A 46-year-old man presented with a painful and inflamed eye after contents of a spider got into his right eye when he squashed the spider with a newspaper. He suffered immediate severe pain in the eye, which rapidly became red and swollen. He had conjunctival edema and periorbital swelling of the eye and severe photophobia, but his vision was normal. RESULTS: Topical local anesthetic was applied to the right eye, which was then flushed with normal saline for an hour. The redness and swelling began to resolve over 2 hours. CONCLUSIONS: Ocular exposure to the contents of a spider can cause severe pain, swelling, and redness associated with photophobia. The effects are short term, so reassurance, irrigation, and symptomatic treatment are sufficient.

Acute Disease↗