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Does This Patient Have a Severe Snake Envenomation?: The Rational Clinical Examination Systematic Review.
JAMA Surg. 2019 04 01; 154(4):346-354.JS

Abstract

Importance

Venomous snakebite severity ranges from an asymptomatic dry bite to severe envenomation and death. The clinical evaluation aids in prognosis and is essential to determine the risks and potential benefits of antivenom treatment.

Objectives

To identify historical features, clinical examination findings, basic laboratory testing, and clinical grading scales that will risk-stratify patients with pit viper snake envenomation for severe systemic envenomation, severe tissue injury, and/or severe hematologic venom effects.

Data Sources

We conducted a structured search of PubMed (1966-October 3, 2017) and Embase database (1980-October 3, 2017) to identify English-language studies that evaluated clinical features predictive of severe envenomation.

Study Selection

We included studies that evaluated the test performance of at least 1 clinical finding with an acceptable reference standard of severe envenomation for venomous snakes of the Western Hemisphere. Only studies involving the most common subfamily, Crotalinae (pit vipers), were evaluated. Seventeen studies with data were available for abstraction.

Data Extraction and Synthesis

The clinical features assessed and severity outcome measures were extracted from each original study. We assessed severity in 3 categories: systemic toxicity, tissue injury, and hematologic effects. Differences were resolved by author consensus.

Results

The pooled prevalence of severe systemic envenomation was 14% (95% CI, 9%-21%). The pooled prevalence of severe tissue injury and severe hematologic venom effects were 14% (95% CI, 12%-16%) and 18% (95% CI, 8%-27%), respectively. Factors increasing the likelihood of severe systemic envenomation included the time from bite to care of 6 or more hours (likelihood ratio [LR], 3.4 [95% CI, 1.1-6.4]), a patient younger than 12 years (LRs, 3.2 [95% CI, 1.5-7.1] and 2.9 [95% CI, 1.3-6.2]), large snake size (LR, 3.1 [95% CI, 1.5-5.7]), and ptosis (LRs, 1.4 [95% CI, 1.0-2.1] and 3.8 [95% CI, 1.8-8.3]). Envenomation by the genus Agkistrodon (copperhead and cottonmouth), as opposed to rattlesnakes, decreased the likelihood of severe systemic envenomation (LR, 0.28 [95% CI, 0.10-0.78]). Initial hypofibrinogenemia (LR, 5.1 [95% CI, 1.7-15.0]) and thrombocytopenia (LR, 3.7 [95% CI, 1.9-7.3]) increased the likelihood of severe hematologic venom effects. Other clinical features from history, physical examination, or normal laboratory values were not discriminative.

Conclusions

Clinical features can identify patients at increased risk of severe systemic envenomation and severe hematologic venom effects, but there are few features that are associated with severe tissue injury or can confidently exclude severe envenomation. Physicians should monitor patients closely and be wary of progression from nonsevere to a severe envenomation and have a low threshold to escalate therapy as needed.

Authors+Show Affiliations

Division of Emergency Medicine, Duke University School of Medicine, Durham, North Carolina.Division of Emergency Medicine, Duke University School of Medicine, Durham, North Carolina.Kaiser Permanente South San Francisco, South San Francisco, California.Department of Medicine, Durham VA Medical Center, Durham, North Carolina. Department of Medicine, Duke University Health System, Durham, North Carolina.Department of Emergency Medicine and Rocky Mountain Poison and Drug Center, Denver Health, Denver, Colorado. Department of Emergency Medicine, University of Colorado School of Medicine, Aurora.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Systematic Review

Language

eng

PubMed ID

30758508

Citation

Gerardo, Charles J., et al. "Does This Patient Have a Severe Snake Envenomation?: the Rational Clinical Examination Systematic Review." JAMA Surgery, vol. 154, no. 4, 2019, pp. 346-354.
Gerardo CJ, Vissoci JRN, Evans CS, et al. Does This Patient Have a Severe Snake Envenomation?: The Rational Clinical Examination Systematic Review. JAMA Surg. 2019;154(4):346-354.
Gerardo, C. J., Vissoci, J. R. N., Evans, C. S., Simel, D. L., & Lavonas, E. J. (2019). Does This Patient Have a Severe Snake Envenomation?: The Rational Clinical Examination Systematic Review. JAMA Surgery, 154(4), 346-354. https://doi.org/10.1001/jamasurg.2018.5069
Gerardo CJ, et al. Does This Patient Have a Severe Snake Envenomation?: the Rational Clinical Examination Systematic Review. JAMA Surg. 2019 04 1;154(4):346-354. PubMed PMID: 30758508.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Does This Patient Have a Severe Snake Envenomation?: The Rational Clinical Examination Systematic Review. AU - Gerardo,Charles J, AU - Vissoci,João R N, AU - Evans,C Scott, AU - Simel,David L, AU - Lavonas,Eric J, PY - 2019/2/14/pubmed PY - 2020/2/19/medline PY - 2019/2/14/entrez SP - 346 EP - 354 JF - JAMA surgery JO - JAMA Surg VL - 154 IS - 4 N2 - Importance: Venomous snakebite severity ranges from an asymptomatic dry bite to severe envenomation and death. The clinical evaluation aids in prognosis and is essential to determine the risks and potential benefits of antivenom treatment. Objectives: To identify historical features, clinical examination findings, basic laboratory testing, and clinical grading scales that will risk-stratify patients with pit viper snake envenomation for severe systemic envenomation, severe tissue injury, and/or severe hematologic venom effects. Data Sources: We conducted a structured search of PubMed (1966-October 3, 2017) and Embase database (1980-October 3, 2017) to identify English-language studies that evaluated clinical features predictive of severe envenomation. Study Selection: We included studies that evaluated the test performance of at least 1 clinical finding with an acceptable reference standard of severe envenomation for venomous snakes of the Western Hemisphere. Only studies involving the most common subfamily, Crotalinae (pit vipers), were evaluated. Seventeen studies with data were available for abstraction. Data Extraction and Synthesis: The clinical features assessed and severity outcome measures were extracted from each original study. We assessed severity in 3 categories: systemic toxicity, tissue injury, and hematologic effects. Differences were resolved by author consensus. Results: The pooled prevalence of severe systemic envenomation was 14% (95% CI, 9%-21%). The pooled prevalence of severe tissue injury and severe hematologic venom effects were 14% (95% CI, 12%-16%) and 18% (95% CI, 8%-27%), respectively. Factors increasing the likelihood of severe systemic envenomation included the time from bite to care of 6 or more hours (likelihood ratio [LR], 3.4 [95% CI, 1.1-6.4]), a patient younger than 12 years (LRs, 3.2 [95% CI, 1.5-7.1] and 2.9 [95% CI, 1.3-6.2]), large snake size (LR, 3.1 [95% CI, 1.5-5.7]), and ptosis (LRs, 1.4 [95% CI, 1.0-2.1] and 3.8 [95% CI, 1.8-8.3]). Envenomation by the genus Agkistrodon (copperhead and cottonmouth), as opposed to rattlesnakes, decreased the likelihood of severe systemic envenomation (LR, 0.28 [95% CI, 0.10-0.78]). Initial hypofibrinogenemia (LR, 5.1 [95% CI, 1.7-15.0]) and thrombocytopenia (LR, 3.7 [95% CI, 1.9-7.3]) increased the likelihood of severe hematologic venom effects. Other clinical features from history, physical examination, or normal laboratory values were not discriminative. Conclusions: Clinical features can identify patients at increased risk of severe systemic envenomation and severe hematologic venom effects, but there are few features that are associated with severe tissue injury or can confidently exclude severe envenomation. Physicians should monitor patients closely and be wary of progression from nonsevere to a severe envenomation and have a low threshold to escalate therapy as needed. SN - 2168-6262 UR - https://www.unboundmedicine.com/medline/citation/30758508/Does_This_Patient_Have_a_Severe_Snake_Envenomation:_The_Rational_Clinical_Examination_Systematic_Review_ L2 - https://jamanetwork.com/journals/jamasurgery/fullarticle/10.1001/jamasurg.2018.5069 DB - PRIME DP - Unbound Medicine ER -