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Biomedical subjects

Geoffrey K Isbister

Publications and source records attributed to Geoffrey K Isbister.

At least 19 recordsLinked to original sources
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

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↗
PubMed2003

Bites by spiders of the family Theraphosidae in humans and canines.

Spiders of the family Theraphosidae occur throughout most tropical regions of the world. There have only been three case reports of bites by these spiders in Australia. The aim of this study was to describe the clinical effects of bites by Australian theraphosid spiders in both humans and canines. Cases of spider bite were collected by the authors over the period January 1978-April 2002, either prospectively in a large study of Australian spider bites, or retrospectively from cases reported to the authors. Subjects were included if they had a definite bite and had collected the spider. The spiders were identified by an expert arachnologist to genus and species level where possible. There were nine confirmed bites by spiders of the family Theraphosidae in humans and seven in canines. These included bites by two Selenocosmia spp. and by two Phlogiellus spp. The nine spider bites in humans did not cause major effects. Local pain was the commonest effect, with severe pain in four of seven cases where severity of pain was recorded. Puncture marks or bleeding were the next most common effect. In one case the spider had bitten through the patient's fingernail. Mild systemic effects occurred in one of nine cases. There were seven bites in dogs (Phlogellius spp. and Selenocosmia spp.), and in two of these the owner was bitten after the dog. In all seven cases the dog died, and as rapidly as 0.5-2h after the bite. This small series of bites by Australian theraphosid spiders gives an indication of the spectrum of toxicity of these spiders in humans. Bites by these spiders are unlikely to cause major problems in humans. The study also demonstrates that the venom is far more toxic to canines.

Adult↗
PubMed2003

Australian scorpion stings: a prospective study of definite stings.

There is little information on scorpion stings in Australia. The aim of this study is to describe the circumstances and clinical effects of stings by Australian scorpions. Cases of scorpion stings were collected prospectively from calls and presentations to Australian poison information centres and emergency departments from February 2000 to April 2002. Only definite scorpion stings where the scorpion was immediately collected and expertly identified were included. There were 95 patients, 33 males and 62 females, with a mean age of 32 (SD 19.5; range 1-71) and 23 children (age<15 years). Three families of scorpions caused all stings: Buthidae (79), Bothruiridae (11, all Cercophonius spp.) and Urodacidae (five, all Urodacus spp.). The majority of stings (76%) were by one genus of scorpion Lychas spp. Seventy one percent of stings occurred between 6pm and 8am and 82 (86%) occurred indoors. Sixty percent of stings occurred on distal limbs. The median duration of effects was 6 h (interquartile range (IQR): 1-24 h). Immediate localised pain occurred in all cases and was severe in 76 cases (80%). Other local effects included red mark/redness (66%), tenderness (35%), numbness (12%) and paraesthesia (11%). Minor systemic effects (nausea, headache and malaise) occurred in 11% of cases. There were no deaths or major systemic envenoming. Less severe effects were observed for the larger Urodacus species, compared to Lychas spp. Scorpion stings in Australia do not appear to cause severe or life-threatening effects, even in children. This differs from other parts of the world, where severe envenoming is reported. The major clinical effect is severe pain, consistent with other scorpion stings. Most stings occurred indoors and at night.

Adolescent↗
PubMed2003

A prospective study of definite bites by spiders of the family Sparassidae (huntsmen spiders) with identification to species level.

Spiders of the family Sparassidae occur on most continents in tropical and temperate regions of the world. They are large Araneomorphae (modern spiders) which are often feared. There are few reports of confirmed sparassid bites and some suggest that particular genera (Neosparassus) can cause severe effects. This study investigated the circumstances and clinical effects of bites by Australian sparassid spiders with correlation to taxonomic species level. Cases were recruited prospectively from calls to Australian poison information centres and two emergency departments. Patients were included if there was a clear history of bite and the spider was caught, and were followed up over a week. There were 173 patients with spider injuries and 168 with definite bites by sparassid spiders over a 27 month period. Ninety-five percent of bites were by spiders from four genera: Isopeda (32%), Isopedella (21%), Neosparassus (27%) and Heteropoda (14%); other genera included Delena and Holconia. The seasonal and diurnal distribution of bites differed between genera, although the majority occurred in warmer months in daylight hours. Seventy-six percent of bites occurred because the spider was interfered with (picked up, dressing or picked up an object with the spider) consistent with the behaviour of most of the family requiring provocation to bite. Ninety-five percent of bites occurred on limbs, 82% on distal limbs, again consistent with handling the spider. Pain/discomfort occurred in all cases, and was severe in 27%. The median duration of pain was 5 min which was significantly less than other spiders. Puncture marks (40%) or localised initial bleeding (35%) occurred in 54% of bites, and both occurred significantly more often in all sparassid bites compared to all other spider bites (p<0.0001). Swelling occurred in 16%, itchiness in 14% and redness/red mark in 57% of cases, the latter significantly less common than other spiders (p=0.0002). Systemic effects occurred in 4% of bites and were minor (nausea and/or headache). There were no cases of necrotic ulcers or allergic reactions. There were four cases with features consistent with local infection. Bites by sparassid spiders cause minor effects, characterised by immediate and transient pain, associated with bleeding, puncture marks and local redness. The mechanism of effects appeared to be trauma rather than envenoming. There were no major differences between genera, and Neosparassus spp. did not cause major effects.

Adolescent↗
PubMed2003

Valproate overdose: a comparative cohort study of self poisonings.

AIMS: Based on individual case reports of massive overdoses, valproate is often regarded as having significant toxicity. This study aimed to describe the epidemiology of valproate poisoning and the spectrum of its clinical effects. METHODS: Consecutive valproate poisonings were identified and compared with other anticonvulsant overdoses and all other poisonings, from a prospective database of poisoning admissions presenting to a regional toxicology service. National prescription data for the same period were obtained. RESULTS: There were 79 patients with valproate poisoning from January 1991 to November 2001, 15 cases with valproate alone. Of the 15 cases, drowsiness occurred in two patients (both taking> 200 mg kg-1), vomiting occurred in four and tachycardia in five. In patients co-ingesting other medications, moderate to severe effects were consistent with the co-ingestants. There was one death not directly related to valproate. One patient had metabolic acidosis and thrombocytopaenia consistent with severe valproate toxicity. Comparison of valproate, carbamazepine, phenytoin and control groups showed that length of stay for both phenytoin and carbamazepine was significantly longer than for valproate (P < 0.0001), and there was a significantly increased risk of intensive care unit admission for carbamazepine vs valproate (OR 2.73; 95% CI 1.22, 6.28; P = 0.015). Although valproate prescriptions increased over the 10 years, there was relatively greater increase in the incidence of valproate poisoning. The odds of a valproate overdose in 1992 compared with carbamazepine were 0.29 (95% CI 0.07, 1.28; P = 0.141), but in 2001 were 2.73 (95% CI 1.38, 5.39; P = 0.004). CONCLUSIONS: Valproate causes mild toxicity in the majority of cases. Massive overdoses of greater than 400 mg kg-1 can cause severe toxicity, but these are uncommon. The older anticonvulsants phenytoin and carbamazepine remain a greater problem than valproate in overdose.

Adult↗
PubMed2003

Moclobemide poisoning: toxicokinetics and occurrence of serotonin toxicity.

AIMS: To investigate the spectrum of toxicity of moclobemide overdose, the occurrence of serotonin toxicity, and to estimate toxicokinetic parameters. METHODS: All moclobemide overdoses presenting over a 10-year period to the Hunter Area Toxicology Service were reviewed. Clinical features, complications, length of stay (LOS) and intensive care (ICU) admission rate were extracted from a standardized, prospectively collected database. Comparisons were made between moclobemide alone and moclobemide with a serotonergic coingestant poisoning. Serotonin toxicity was defined by a combination of Sternbach's criteria and a clinical toxicologist's diagnosis. In five patients serial moclobemide concentrations were measured. Time to maximal plasma concentration (Tmax), peak plasma concentration (Cmax) and terminal elimination half-lives were estimated. RESULTS: Of 106 included patients, 33 ingested moclobemide alone, 21 ingested moclobemide with another serotonergic agent (in some cases in therapeutic doses) and 52 ingested moclobemide with a nonserotonergic agent. Eleven (55%) of 21 patients coingesting a serotonergic drug developed serotonin toxicity, which was significantly more than one (3%) of 33 moclobemide-alone overdoses (odds ratio 35, 95% confidence interval 4, 307; P < 0.0001). In six of these 21 cases severe serotonin toxicity developed with temperature >38.5 degrees C and muscle rigidity requiring intubation and paralysis. The 21 patients had a significantly increased LOS (34 h) compared with moclobemide alone overdoses (12 h) (P < 0.0001) and a significantly increased ICU admission rate of 57% vs. 3% (P < 0.0001). Time to peak plasma concentration was delayed in two patients where prepeak samples were obtained. Cmax increased slightly with dose, but all three patients ingesting > or = 6 g vomited or had charcoal. The mean elimination half-life of moclobemide in the five patients in whom serial moclobemide concentrations were measured was 6.3 h and elimination was first order in all cases. There was no evidence of a dose-dependent increase in half-life. CONCLUSIONS: The effects of moclobemide alone in overdose are minor, even with massive ingestions. However, moclobemide overdose in combination with a serotonergic agent (even in normal therapeutic doses) can cause severe serotonin toxicity. The elimination half-life is prolonged by two to four times in overdose, compared with that found in healthy volunteers given therapeutic doses. This may be a result of wide interindividual variation in overall elimination, also seen with therapeutic doses, but appears not to be due to saturation of normal elimination pathways.

Adult↗
PubMed2003

Suspected snakebite: one year prospective study of emergency department presentations.

AIM: Snakebite is an uncommon, but potentially life-threatening condition. The more common clinical scenario is suspected snake-bite. Our aim was to characterise the epidemiology, diagnosis and management of patients with suspected snakebites. METHODS: Prospective cohort study of patients presenting with suspected snakebites to a tertiary referral hospital serving a large rural region in tropical northern Australia where a standard admission protocol for suspected snakebites is used. RESULTS: Of 70 suspected snakebite cases, there were 45 definite bites: three severe envenomings (two western brown snakes [Pseudonaja nuchalis] and one mulga snake [Pseudechis australis]); seven mild/moderate envenomings by other snakes, two non-envenomings by identified P. nuchalis, five bites by identified non-venomous snakes and 28 definite bites without envenoming. The remaining 25 cases were either suspected bites (8), unlikely bites (15) and two people hit by snakes. Definite snake-bites occurred throughout the year, peaking in May and December. There were three severe envenomings (mainly coagulopathy), requiring antivenom treatment, but no deaths or major complications. Most patients had appropriate investigations. Of 47 venom detection kit swabs collected, 34 were not tested, venom was not detected in nine and was positive in the three envenomings with one false-positive tiger snake. Whole blood clotting time was highly sensitive for procoagulant coagulopathy and envenoming in this study. Median length of time from the bite to discharge was 20 h (interquartile range: 12-27). CONCLUSIONS: The study shows that although suspected snakebite was common, severe envenoming occurred in less than 5% of cases. The study supports the proposition that a structured approach and admission policy of suspected snakebites leads to the appropriate management of severe envenoming, with no cases discharged early and no cases of non-envenoming treated with antivenom.

Adolescent↗
PubMed2003

Nefazodone poisoning: toxicokinetics and toxicodynamics using continuous data collection.

Nefazodone overdose has been reported infrequently. The commonest effects reported are drowsiness, nausea, dizziness, and vomiting, less commonly hypotension and bradycardia. We report a case of single-agent nefazodone poisoning. Serial drug concentrations were taken for quantification of parent drug and metabolites. Clinical findings were documented every 1 to 2 hours. We modeled both the toxicokinetics of nefazodone and correlated this with clinical effects and electrocardiograph (ECG) abnormalities. A 16-year-old female took 2.4 g of nefazodone. She had significant drowsiness in the first 6 hours, associated with hypotension (systolic BP < 90 mmHg; lowest BP 70/30 mmHg) for 18 hours, and mild bradycardia (slowest rate of 56 bpm). She had a prolonged QT/QTc which normalized over 24 hours. She was given charcoal and intravenous fluids and was observed carefully, recovering with no problems. The terminal elimination half-life for nefazodone was 8.3 hours, and its metabolite hydroxy(OH)-nefazodone was 14.6 hours. BP-time curves demonstrated an 18-hour period of hypotension. There was a significant correlation between systolic BPand OH-nefazodone (R2 = 0.602). HR remained between 56 and 66 bpm for 30 hours despite hypotension. QT was significantly correlated with nefazodone (R2 = 0.911) and OH-nefazodone (R2 = 0.797), but no significant relationship between QTc and drug concentrations. The case demonstrates that nefazodone may potentially cause cardiac toxicity, which appears to be concentration-dependent. Although QT was concentration-dependent, this would need confirmation with other cases. Bradycardia, hypotension, and drowsiness are the most significant effects and are maximal in the first 12 hours when parent and metabolite concentrations are high.

Adolescent↗