Does This Patient Have a Severe Snake Envenomation?: The Rational Clinical Examination Systematic Review.

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.

Marked Hypofibrinogenemia and Gastrointestinal Bleeding After Copperhead (Agkistrodon contortrix) Envenomation.

Compared with other crotaline envenomations, copperhead envenomations have historically been reported as having less severe hematologic venom effects and rarely hemorrhage. We report a case of clinically significant gastrointestinal bleeding after a copperhead (Agkistrodon contortrix) envenomation. A 52-year-old woman with a history of systemic lupus erythematosus was bitten on her right medial ankle after which hypofibrinogenemia and hematochezia developed. The symptoms resolved after repeated administration of Crotalidae polyvalent immune Fab (ovine) antivenom. She was discharged without further complications 2 days later. Although copperhead envenomations are classically considered less severe than other crotaline envenomations, this case demonstrates the potential of the venom to produce clinically significant hematologic effects.

Time to antivenom administration is not associated with total antivenom dose administered in a copperhead-predominant snakebite population.

OBJECTIVES: To prevent unnecessary antivenom administration in crotaline snakebite, observation for progression is recommended for the patient with minor envenomation whose condition is stable and not progressing. The objective of this study was to determine the association between the time from bite to initial antivenom administration (Time(AV)) and the total amount of antivenom administered (Total(AV)) and to determine what proportion of patients did not have progression of the envenomation syndrome and did not receive antivenom. METHODS: This was a retrospective chart review of patients presenting with crotaline snakebite within 24 hours from 2009 through 2012. Blinded dual-chart abstraction and strict data point definitions were used. Spearman correlation was used to determine the association between Time(AV) and Total(AV). A general linear model was used to examine this association using Time(AV) categorized to early and late administration, adjusted for likely confounders. Confounders included age, extremity involved, initial severity, and year of envenomation. RESULTS: Ninety-five eligible patients were analyzed with 45 (47%) males and a mean (±SD) age of 36.5 (±21.1) years. Eighty-five (89%) received antivenom, with a median Time(AV) of 3.3 hours (interquartile range [IQR] = 2.5 to 5.2 hours). The median Total(AV) was 10 vials (IQR = 6 to 14 vials). The univariate analysis showed a small but statistically significant decrease in Total(AV) given to patients treated greater than 6 hours from bite (r = -0.26, p = 0.015). The multivariate analysis resulted in no significant relation between early or late Time(AV) and Total(AV) (p = 0.10) after adjustment for confounders. Most minimal envenomation syndromes (80%, or 41 of 51) progressed to moderate grade envenomations. CONCLUSIONS: Time(AV) was not associated with Total(AV) when adjusted for likely confounders and supports current recommendations to observe for progression in minor envenomation. The majority of envenomations progressed, resulting in only a small proportion of patients not eventually receiving antivenom. The authors recommend observation in an environment where the patient can be adequately reassessed for progression of the envenomation.

Head computed tomography utilization and intracranial hemorrhage rates.

Utilization of computed tomography scans (CTs) has increased dramatically in emergency departments in the USA. This study aimed to retrospectively determine the yield of CTs among all patients that received a CT of the head from 2001 to 2007, which is adjusted for patient volume. For secondary endpoints, we examined the yield of CT of the head for the following hemorrhages: (1) intracerebral, (2) subarachnoid, (3) subdural, and (4) epidural. In 2001, 3.3 head CTs were performed per 100 patients seen. This increased by 60 % to 5.2 per 100 in 2007 (p = 0.005, R (2) = 0.82). This correlated with a nonsignificant decrease in the rate of intracranial hemorrhage found by CT from 3.6 per 100 CTs in 2001 (95 % confidence interval (CI) = 2.7-4.5) to 3.0 per 100 in 2007 (95 % CI = 2.5-3.6). There were no significant differences in "positive" rates for each subgroup of intracranial hemorrhage. Our study found that the utilization of head CTs increased dramatically, but there was a corresponding increase in the number of positive findings so that the overall yield of head CTs from 2001 to 2007 remained relatively constant.

Ultrasound and ski resort clinics: mapping out the potential benefits.

BACKGROUND: Skiing and snowboarding are popular activities that involve high kinetic energies, often at altitude, and injuries are common. As a portable imaging modality, ultrasound may be a useful adjunct for mountainside clinics. This review briefly discusses skier and snowboarder injury profiles and focuses on the role of ultrasound for each injury type. METHODS: Twenty-two sources including 17 reviews and observational studies were obtained describing skier and snowboarder injuries. Forty-nine studies were identified defining ultrasound applications for these injuries, including 38 reviews and observational studies, 6 case reports or case series, 3 cross-sectional studies, and 2 randomized, blinded studies. RESULTS: Approximately 200 000 rider injuries are evaluated in the Unites States seasonally. Musculoskeletal injuries are the most common, and head, face, neck, and abdominal injuries are also prevalent, as are exacerbations of preexisting disease. Ultrasound has been shown to be useful and accurate for evaluating the aforementioned injury types, including joint, ligament, tendon, and fracture evaluation. Ultrasound has not been extensively studied in the prehospital setting, and only limited data address the utility of how it might influence management in a mountainside clinic setting. CONCLUSIONS: Ultrasound has the potential to be a useful diagnostic modality in ski resort clinics. The most promising areas for future, applied studies include evaluation of musculoskeletal injuries (especially injuries to joints and tendons and ruling out fractures), assessing for elevated intracranial pressure in minor head injuries and symptoms of altitude illness, and focused assessment with sonography for trauma and extended focused assessment with sonography for trauma examinations for cases of chest and abdominal trauma of unknown significance.

Surface water quality along the Central John Muir Trail in the Sierra Nevada Mountains: coliforms and algae.

The John Muir Trail (JMT) in the Sierra Nevada Mountains of California is one of the most popular alpine wilderness trails in the United States, where backpackers depend on trailside water sources for more than 335 km (208 miles). This study addressed the risk of acquiring waterborne disease by analyzing prevalence and changes in coliform bacteria and Escherichia coli (E. coli) in lakes and streams adjacent to the central JMT. Chlorophyll-a levels were also measured as an indicator of high elevation eutrophication. Categories of environmental land use which might affect water quality were defined as: Pristine areas rarely traversed by humans; Backpack off-trail areas not traversed by pack or stock animals; and Multiuse areas with backpacker and animal use. We analyzed surface water at 36 different sites three separate times over an eight week period in the summer of 2008. Chlorophyll-a concentration increased significantly in Backpack and Multiuse sites over the summer months, but not in Pristine sites. Similar results were obtained for coliforms, with prevalence also increasing significantly over the summer months in Backpack and Multiuse sites. There was a much higher prevalence of E. coli in Multiuse sites compared to Pristine and Backpack sites. Our study provides evidence pack and stock animals serve as a source of microbial contamination of water along this section of trail.