ORIGINAL Five-year experience with Chinese cobra (Naja atra)– ARTICLE related injuries in two acute hospitals in Hong Kong OF Wong 黄凱峯 Tommy SK Lam 林成傑 Objective To review the clinical features and management of patients with HT Fung 馮顯達 injuries related to the Chinese cobra (Naja atra). CH Choy 蔡正謙 Design Retrospective study. Setting Two acute hospitals in Hong Kong. Main outcome measures The nature of injuries, envenoming features, complications, response to antivenom therapy, and outcome. Results Eighteen patients were recruited during the 5-year study period. Fifteen of them were snake-bitten, the remaining three suffered ocular injuries. Of the 15 patients with cobra bites, 14 (93%) presented with local swelling. No patient developed severe neurotoxic symptoms. Two patients had laboratory features of haemolysis. Fourteen patients received antivenom therapy and five of them subsequently underwent surgical interventions for extensive local tissue damage and necrosis. There was no fatality. Conclusion Bites from Chinese cobra result in serious local complications with extensive tissue necrosis and minimal neurotoxic symptoms. There is an apparent trend of favourable outcomes following the early administration of antivenom to patients without early signs of irreversible tissue damage. Further research is needed to evaluate the effectiveness of early antivenom use in Chinese cobra bites in order to minimise extent of tissue damage. Introduction Snake envenomation is not an uncommon medical emergency in Hong Kong. Little information about local cobra (Naja atra) envenomation has been reported however. Only three local cases could be found in the literature.1,2 Two of these were described incidentally in a case series about the bamboo snake (Cryptelytrops albolabris), which is responsible for 95% of snake envenomations in this region. Both patients had local symptoms, one of whom developed skin necrosis treated by repeated debridement and a skin graft.1 The third case entailed a fatal N atra bite in another case series.2 The patient developed compartment syndrome over his injured limb complicated by extensive skin necrosis and necrotising fasciitis. The cause of his death was septicaemia complicated with acute renal failure, thrombocytopenia, and coagulopathy. Although cobra bites in Hong Kong are seldom fatal, such envenomations cause many deaths in the agricultural areas of some South Asian countries.3 Envenomation syndromes due to cobras in Asia vary depending on locality. Researchers reported region-specific clinical presentations due to Asiatic cobra species ranging from potentially fatal neurotoxicity but with minimal local symptoms, to extensive Key words 4-6 Antivenins; Cobra venoms; Emergency local tissue necrosis without neurotoxicity. We report here the clinical presentation and treatment; Necrosis; Snake bites management of patients with N atra–related injuries seen in our institutions during the past 5 years. In particular we set out to document the liability to complications from Chinese Hong Kong Med J 2010;16:36-43 cobra bites (including neurotoxic symptoms and local tissue necrosis) encountered locally in comparison to envenomation due to other Asiatic cobra species. Department of Accident and Emergency Medicine, Tuen Mun Hospital, Tuen Mun, Hong Kong Methods OF Wong, FHKCEM, FHKAM (Emergency Medicine) TSK Lam, MB, BS, MRCS(Ed) Patients HT Fung, FRCS (Edin), FHKAM (Emergency Medicine) The study was conducted in the accident and emergency departments (AEDs) of Tuen Mun CH Choy, FHKCEM, FHKAM (Emergency Medicine) Hospital and Pok Oi Hospital. These are the two acute hospitals located in non-urban areas of Correspondence to: Dr OF Wong Hong Kong with a significant burden of snake-bite incidents. All patients who attended the two Email: [email protected] hospitals for Chinese cobra–related injuries from 1 April 2004 to 31 March 2009 were included. 36 Hong Kong Med J Vol 16 No 1 # February 2010 # www.hkmj.org # Chinese cobra–related injuries # TABLE 1. Frequency of patients presenting with cobra bites No. of patient injuries 香港兩間急症醫院處理與眼鏡蛇有關的受 According to month 傷病例的五年經驗 January 0 目的 探討與眼鏡蛇有關的受傷病例，其臨床症狀與處理方 February 0 法。 March 1 設計 回顧研究。 April 1 安排 香港兩間急症醫院。 May 1 主要結果測量 受傷類別、毒液特徵、併發、對抗毒治療的反應及結 June 0 果。 July 1 結果 研究期間共有18位病人，其中15位被蛇咬傷，其餘 August 6 3位被蛇的毒液傷及眼部。15位被眼鏡蛇咬傷的病人 September 2 中，14位（93%）的傷口出現腫脹。病人均沒有嚴 October 4 重的神經中毒症狀，兩位病人的檢驗結果顯示有溶 November 2 血。14位病人接受抗毒治療，其中5位最終須進行手 術以治療擴大性的傷口組織受損及壞死。沒有死亡案 December 0 例。 According to time of injury 結論 被眼鏡蛇咬傷的病人會引致嚴重的傷口組織併發，繼 0000-0559 1 而有擴大性的組織壞死，及出現輕微的神經中毒症 0600-1159 5 狀。縱使病人未有出現不能逆轉的組織受損，盡早使 1200-1759 8 用抗毒治療有明顯較好的治療結果。需要進一步研究 1800-2359 4 及早使用抗毒治療是否可以減低被眼鏡蛇咬傷的組織 According to body part involved 受損程度。 Upper limb 5 Lower limb 10 Eye 3 identification. Ten patients were able to identify the According to location snakes to be Chinese cobra clearly, using the snake photo handbook. Two others were bitten by snakes Indoors 8 of similar appearance and developed typical clinical Outdoors 10 features of Chinese cobra–bite poisoning. On the other hand, four patients with suspected Chinese cobra injuries were excluded, because their wounds Snake identification lacked typical clinical features, despite the Chinese The species of snake was confirmed by examination cobra having been described or identified by the of the specimen (dead or alive), opinion sought from respective patients. local experts (ie advice from the Kadoorie Farm and Botanical Gardens), identification by the patient with the snake photo handbook, or the combination of Time of occurrence and mode of injuries typical clinical features and patients’ descriptions of Among the confirmed cases, 15 endured cobra bites, the appearance of the snakes. whilst three suffered ocular injuries from cobra- venom spat into their eyes. One patient was bitten by a cobra in mainland China, but all the others were local Evaluation cases. Of the 18 incidents, 14 (78%) occurred in the For each incident, demographic data, its timing and summer and early autumn period (between August location, interval between injury and arrival at the and November), 13 (72%) ensued in the daytime AED (bite-to-door time), envenoming symptoms, (06:00-17:59), and eight (44%) occurred indoors. Most local complications, antivenom therapy (number of the cobra bites involved the lower limbs (Table 1). of vials and bite-to-needle time) and response, any All but two patients arrived at the hospital within 2 surgical intervention, and length of hospital stay hours of presentation. were retrieved from the clinical records. Local and systemic complications from cobra Results bites During the study period, there were a total of 18 Eleven of the 15 patients with cobra bites complained confirmed cases of N atra–related injuries. For six of paraesthesia over the wounds and in three of them, incidents, the dead snake specimen was available for the paraesthesias progressed over the entire forearm Hong Kong Med J Vol 16 No 1 # February 2010 # www.hkmj.org 37 # Wong et al # TABLE 2. Clinical features of patients with Naja atra bites due to the extensive area involved. Two patients Patient Sex/age Injured area Neurotoxicity‡ Initial Bite-to- developed laboratory features of haemolysis with a No. (years) local needle time reduction in haemoglobin (Hb) level, elevated blood symptom§ (hours) bilirubin and lactate dehydrogenase (LDH) levels. Without surgical intervention One patient developed a coagulopathy associated 1* M/34 Right ankle + P, E 3 with the wound infection. Electrocardiograms (ECG) 2 F/44 Right little ++ - 3 performed on 13 patients revealed no obvious finger abnormalities. Moreover, none of the 15 patients 3 F/44 Left foot + S, E 4 developed cardiovascular instability (hypotension or bradycardia), and there was no mortality. 4 F/44 Right thumb ++ P, E 6 5 M/51 Right thumb ++ P, E 3 6 F/67 Right thumb + S, E 3 Antivenom therapy and clinical outcome 7 F/20 Left 5th toe + S, E 7 The antivenom we used was manufactured by the 8 M/44 Right 3rd toe + S, E 12 Shanghai Institute of Biological Products and each vial contained 1000 IU. The recommended dose on 9 M/48 Right thumb - S, E 2 the product insert for Chinese cobra bite was 2000 10 F/9 Left foot - P, E 4 IU, but the indications were not clearly documented. With surgical intervention Fourteen of the 15 patients with cobra bites were 11 F/78 Right 4th toe - S, E 2 given antivenom. Local pain and swelling were the 12 M/58 Left ankle - P, E 25 indications we adopted for antivenom in 13 patients. 13 F/26 Left 5th toe + S, E 1 The remaining patient (case 2) had progressive paraesthesia over her injured limb; her symptoms 14 F/84 Left ankle + S, B 2 improved soon after the administration of antivenom. † 15 M/59 Right leg + S, B, N - The median time lag to antivenom administration * This patient was discharged against medical advice and the outcome was unknown after the snakebites was 3 hours (range, 1-25 hours). † No antivenoms therapy because of delayed presentation Treatment was discontinued once there was cessation ‡ Neurotoxicity: + = paraesthesia over bitten area, ++ = progressive paraesthesia of the affected limb of progressive swelling or neurotoxic symptoms. § Extension of swelling: P = pain without obvious swelling, S = extensive swelling well The number of vials given ranged from 1 to 21. In beyond the bitten area; local skin condition: E = erythema, B = bruising or discolouration our patients, no allergic reaction or adverse effect of skin; N = necrosis was encountered after using antivenom. All patients