Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.

STUDY OBJECTIVE: We assess agreement between carboxyhemoglobin levels measured by the Rad-57 signal extraction pulse CO-oximeter (RAD), a Food and Drug Administration-approved device for noninvasive bedside measurement, and standard laboratory arterial or venous measurement in a sample of emergency department (ED) patients with suspected carbon monoxide poisoning. METHODS: The study was a cross-sectional cohort design using a convenience sample of adult and pediatric ED patients in a Level I trauma, burn, and hyperbaric oxygen referral center. Measurement of RAD carboxyhemoglobin was performed simultaneously with blood sampling for laboratory determination of carboxyhemoglobin level. The difference between the measures for each patient was calculated as laboratory carboxyhemoglobin minus carboxyhemoglobin from the carbon monoxide oximeter. The limits of agreement from a Bland-Altman analysis are calculated as the mean of the differences between methods ±1.96 SDs above and below the mean. RESULTS: Median laboratory percentage carboxyhemoglobin level was 2.3% (interquartile range 1 to 8.5; range 0% to 38%). The mean difference between laboratory carboxyhemoglobin values and RAD values was 1.4% carboxyhemoglobin (95% confidence interval [CI] 0.2% to 2.6%). The limits of agreement of differences of measurement made with the 2 devices were -11.6% and 14.4% carboxyhemoglobin. This range exceeded the value of ±5% carboxyhemoglobin defined a priori as clinically acceptable. RAD correctly identified 11 of 23 patients with laboratory values greater than 15% carboxyhemoglobin (sensitivity 48%; 95% CI 27% to 69%). There was one case of a laboratory carboxyhemoglobin level less than 15%, in which the RAD device gave a result greater than 15% (specificity of RAD 96/97=99%; 95% CI 94% to 100%). CONCLUSION: In the range of carboxyhemoglobin values measured in this sample, the level of agreement observed suggests RAD measurement may not be used interchangeably with standard laboratory measurement.

Recurrent hemorrhage after western diamondback rattlesnake envenomation treated with crotalidae polyvalent immune fab (ovine).

INTRODUCTION: Recurrent coagulopathy has been observed in patients after rattlesnake envenomation treated with Crotalidae Polyvalent Immune Fab (ovine) [FabAV]. While recurrent coagulopathy is well documented in the literature, clinically significant sequelae have not been reported. We present a case of recurrent thrombocytopenia after western diamondback envenomation treated with FabAV, resulting in an extensive recurrent local hemorrhage. CASE REPORT: A 24-year-old male presented to our emergency department several hours after western diamondback envenomation. He sustained bites to both hands and the right flank by leaning over his pet "snake enclosure." On presentation, the patient was hypotensive, tachycardic, and thrombocytopenic with a platelet count of 17/nl. Antivenom therapy was initiated according to the standard FabAV protocol. However, sixteen hours after completion of the recommended FabAV infusion, the patient experienced a recurrent thrombocytopenia with a dramatic seventeen point drop in hematocrit. The source of bleeding was clinically attributed to an expanding hematoma at the site of envenomation. DISCUSSION: FabAV has become the standard treatment for symptomatic crotalid envenomation. However, the pharmacokinetics of this drug predispose it to recurrent coagulopathies. While studies have shown persistent and recurrent coagulopathic derangements after FabAV therapy, no clinically significant sequelae have been reported. This report highlights the potential for recurrent local hemorrhagic complications following rattlesnake envenomation, even after treatment guided by the current FabAV protocol. CONCLUSIONS: Recurrent coagulopathy following FabAV therapy can result in clinically significant hemorrhage, supporting the observation that extended repeat dosing may be necessary to adequately treat subjects of rattlesnake envenomation.

Gaboon viper (Bitis gabonica) envenomation resulting from captive specimens--a review of five cases.

BACKGROUND: Five cases of illegitimate bite by captive specimens of the Gaboon viper (Bitis gabonica) snake have demonstrated the dangers of keeping exotic African snakes in captivity. CASE SERIES: Four cases necessitated hospitalization for the bite and were characterized by progressive swelling of the affected limb, local necrosis and hemorrhagic edema near the wound, chest tightness and prolonged coagulation times. However, platelet counts were not altered. All patients received antivenom and had uneventful recovery, except for one who underwent amputation of a distal phalanx and one who required debridement. In the fifth case, the patient died without being able to summon help. DISCUSSION: The results of this case series emphasize the need for extreme care to be exercised with the captivity of exotic snakes, such as the Gaboon viper. The increasing popularity of this snake as a captive pet predicates the need for private collectors to have a pre-existing treatment strategy with their local emergency centers. Such arrangements may facilitate the treatment of envenomation by this snake.

An adolescent scuba diver with 2 episodes of diving-related injuries requiring hyperbaric oxygen recompression therapy: a case report with medical considerations for child and adolescent scuba divers.

Worldwide, more than 1000 scuba (self-contained underwater breathing apparatus) diving injuries per year requiring hyperbaric recompression are documented. Approximately 80 to 90 fatalities per year are reported in North America. On average, there were 16 diving injuries requiring hyperbaric recompression therapy in scuba divers aged 19 years and younger in North America between 1988 and 2002. The youngest injured diver was 11 years old, and the youngest fatality was 14 years old during this time period. In the year 2000, certifying recreational scuba diving organizations lowered the minimum age to 8 from age 12 years for participation in the sport. We report a case of a highly trained adolescent scuba diver who, despite having advanced diving certifications, had 2 separate episodes of diving-related injuries requiring hyperbaric recompression therapy. A discussion of medical considerations in the care of the child and adolescent scuba diver is included.

Efficacy of Crotalidae polyvalent antivenin for the treatment of hognosed viper (Porthidium nasutum) envenomation.

Envenomation from pit vipers native to North America can be treated successfully with either of the 2 commercially available antivenoms licensed in the United States. However, envenomations from imported snakes held in zoos or private collections often pose unique challenges to management because of the lack of specific antivenom and the unclear efficacy of the available licensed products. We report the case of a 37-year-old man who was envenomated on his left hand by his pet hognosed viper (Porthidium nasutum ). He had swelling at the wound site that progressively worsened over 3 to 4 hours. His symptom progression included the structural motor impairment of his fingers and a sensory deficit. Treatment with 8 vials of Antivenin (Crotalidae) polyvalent was associated with a halt of extremity swelling and restoration of neurologic and motor function of his hand. Limited experimental evidence provides support for antigenic cross-reactivity between Antivenin (Crotalidae) polyvalent and P nasutum venom.

Validity of a decision rule to reduce cervical spine radiography in elderly patients with blunt trauma.

STUDY OBJECTIVES: A decision instrument based on 5 clinical criteria has been shown to be highly sensitive in selecting patients who require cervical spine imaging after blunt trauma, while simultaneously reducing overall imaging. We examine the performance of this instrument in the elderly and explore some of the common features of geriatric cervical spine injury (CSI). METHODS: The National Emergency X-radiography Utilization Study (NEXUS) was a prospective, observational, multicenter study conducted at 21 geographically diverse centers. We analyzed the performance of the NEXUS decision instrument among patients at least 65 years of age. RESULTS: The study group consisted of 2,943 (8.6%) geriatric patients, representing 8.6% of the entire NEXUS sample. The rate of CSI was twice as great in these patients as it was in nongeriatric patients (4.59% versus 2.19%). Odontoid fractures were particularly common in geriatric patients, accounting for 20% of geriatric fractures compared with 5% of nongeriatric fractures. The frequency of patients meeting NEXUS criteria was similar in the 2 groups, with 14% of geriatric patients and 12.5% of nongeriatric patient classified as low risk. CSI occurred in only 2 low-risk geriatric patients, and these patients' injuries met our preset definition of a clinically insignificant injury. The sensitivity of the NEXUS decision instrument for clinically significant injury in the geriatric group was therefore 100% (95% confidence interval 97.1% to 100%). CONCLUSION: The prevalence of CSI, and especially odontoid fracture, is relatively increased among geriatric patients with blunt trauma. The NEXUS decision instrument can be applied safely to these patients, with an expected reduction in cervical imaging comparable with that achieved in nongeriatric patients.