Changes in serial laboratory test results in snakebite patients

when can we safely exclude envenoming?

Graham Ireland, Simon Brown, Nicholas Buckley, Jeff Stormer, Bart Currie, Julian White, David Spain, Geoffrey Isbister

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Objectives: To determine which laboratory tests are first associated with severe envenoming after a snakebite, when (ie, how long after the bite) the test results become abnormal, and whether this can determine a safe observation period after suspected snakebite.

    Design, patients and setting: Prospective cohort study of 478 patients with suspected or confirmed snakebite recruited to the Australian Snakebite Project from January 2002 to April 2009, who had at least three sets of laboratory test results and at least 12 hours of observation in hospital after the bite. Severe envenoming was defined as venom-induced consumption coagulopathy (VICC), myotoxicity, neurotoxicity or thrombotic microangiopathy.

    Main outcome measures:
    International normalised ratio (INR), activated partial thromboplastin time (aPTT), creatine kinase (CK) level, and neurological examination.

    Results: There were 240 patients with severe envenoming, 75 with minor envenoming and 163 non-envenomed patients. Of 206 patients with VICC, 178 had an INR > 1.2 (abnormal) on admission, and the remaining 28 had an INR > 1.2 within 12 hours of the bite. Of 33 patients with myotoxicity, a combination of CK > 250 U/L and an abnormal aPTT identified all but two cases by 12 hours; one of these two was identified within 12 hours by leukocytosis. Nine cases of isolated neurotoxicity had a median time of onset after the bite of 4 hours (range, 35 min - 12 h). The combination of serial INR, aPTT and CK tests and repeated neurological examination identified 213 of 222 severe envenoming cases (96%) by 6 hours and 238 of 240 (99%) by 12 hours.

    Conclusion: Laboratory parameters (INR, aPTT and CK) and neurological reassessments identified nearly all severe envenoming cases within 12 hours of the bite, even in this conservative analysis that assumed normal test results if the test was not done.
    Original languageEnglish
    Pages (from-to)285-290
    Number of pages6
    JournalMedical Journal of Australia
    Volume193
    Issue number5
    Publication statusPublished - 6 Sep 2010

    Fingerprint

    Snake Bites
    International Normalized Ratio
    Bites and Stings
    Partial Thromboplastin Time
    Creatine Kinase
    Disseminated Intravascular Coagulation
    Venoms
    Neurologic Examination
    Observation
    Thrombotic Microangiopathies
    Leukocytosis
    Cohort Studies
    Outcome Assessment (Health Care)
    Prospective Studies

    Cite this

    Ireland, G., Brown, S., Buckley, N., Stormer, J., Currie, B., White, J., ... Isbister, G. (2010). Changes in serial laboratory test results in snakebite patients: when can we safely exclude envenoming? Medical Journal of Australia, 193(5), 285-290.
    Ireland, Graham ; Brown, Simon ; Buckley, Nicholas ; Stormer, Jeff ; Currie, Bart ; White, Julian ; Spain, David ; Isbister, Geoffrey. / Changes in serial laboratory test results in snakebite patients : when can we safely exclude envenoming?. In: Medical Journal of Australia. 2010 ; Vol. 193, No. 5. pp. 285-290.
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    abstract = "Objectives: To determine which laboratory tests are first associated with severe envenoming after a snakebite, when (ie, how long after the bite) the test results become abnormal, and whether this can determine a safe observation period after suspected snakebite. Design, patients and setting: Prospective cohort study of 478 patients with suspected or confirmed snakebite recruited to the Australian Snakebite Project from January 2002 to April 2009, who had at least three sets of laboratory test results and at least 12 hours of observation in hospital after the bite. Severe envenoming was defined as venom-induced consumption coagulopathy (VICC), myotoxicity, neurotoxicity or thrombotic microangiopathy. Main outcome measures: International normalised ratio (INR), activated partial thromboplastin time (aPTT), creatine kinase (CK) level, and neurological examination. Results: There were 240 patients with severe envenoming, 75 with minor envenoming and 163 non-envenomed patients. Of 206 patients with VICC, 178 had an INR > 1.2 (abnormal) on admission, and the remaining 28 had an INR > 1.2 within 12 hours of the bite. Of 33 patients with myotoxicity, a combination of CK > 250 U/L and an abnormal aPTT identified all but two cases by 12 hours; one of these two was identified within 12 hours by leukocytosis. Nine cases of isolated neurotoxicity had a median time of onset after the bite of 4 hours (range, 35 min - 12 h). The combination of serial INR, aPTT and CK tests and repeated neurological examination identified 213 of 222 severe envenoming cases (96{\%}) by 6 hours and 238 of 240 (99{\%}) by 12 hours. Conclusion: Laboratory parameters (INR, aPTT and CK) and neurological reassessments identified nearly all severe envenoming cases within 12 hours of the bite, even in this conservative analysis that assumed normal test results if the test was not done.",
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    Ireland, G, Brown, S, Buckley, N, Stormer, J, Currie, B, White, J, Spain, D & Isbister, G 2010, 'Changes in serial laboratory test results in snakebite patients: when can we safely exclude envenoming?', Medical Journal of Australia, vol. 193, no. 5, pp. 285-290.

    Changes in serial laboratory test results in snakebite patients : when can we safely exclude envenoming? / Ireland, Graham; Brown, Simon; Buckley, Nicholas; Stormer, Jeff; Currie, Bart; White, Julian; Spain, David; Isbister, Geoffrey.

    In: Medical Journal of Australia, Vol. 193, No. 5, 06.09.2010, p. 285-290.

    Research output: Contribution to journalArticleResearchpeer-review

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    AU - Buckley, Nicholas

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    AU - Spain, David

    AU - Isbister, Geoffrey

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    N2 - Objectives: To determine which laboratory tests are first associated with severe envenoming after a snakebite, when (ie, how long after the bite) the test results become abnormal, and whether this can determine a safe observation period after suspected snakebite. Design, patients and setting: Prospective cohort study of 478 patients with suspected or confirmed snakebite recruited to the Australian Snakebite Project from January 2002 to April 2009, who had at least three sets of laboratory test results and at least 12 hours of observation in hospital after the bite. Severe envenoming was defined as venom-induced consumption coagulopathy (VICC), myotoxicity, neurotoxicity or thrombotic microangiopathy. Main outcome measures: International normalised ratio (INR), activated partial thromboplastin time (aPTT), creatine kinase (CK) level, and neurological examination. Results: There were 240 patients with severe envenoming, 75 with minor envenoming and 163 non-envenomed patients. Of 206 patients with VICC, 178 had an INR > 1.2 (abnormal) on admission, and the remaining 28 had an INR > 1.2 within 12 hours of the bite. Of 33 patients with myotoxicity, a combination of CK > 250 U/L and an abnormal aPTT identified all but two cases by 12 hours; one of these two was identified within 12 hours by leukocytosis. Nine cases of isolated neurotoxicity had a median time of onset after the bite of 4 hours (range, 35 min - 12 h). The combination of serial INR, aPTT and CK tests and repeated neurological examination identified 213 of 222 severe envenoming cases (96%) by 6 hours and 238 of 240 (99%) by 12 hours. Conclusion: Laboratory parameters (INR, aPTT and CK) and neurological reassessments identified nearly all severe envenoming cases within 12 hours of the bite, even in this conservative analysis that assumed normal test results if the test was not done.

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