Angioedema following anti-snake venom administration

S. Venkateswaran*

Intensivist, Kauvery Hospital, Salem

Abstract

Angioedema is a known complication of anti-snake venom (ASV) therapy for snake bite envenomation. We present a 68-years-aged male patient who presented with oropharyngeal angioedema following ASV administration who was managed using awake fibreoptic intubation, steroids and antihistaminic therapy.

Case Presentation

A 68-year-aged male patient presented to our hospital with the history of unknown snakebite over his left foot while driving his two-wheeler following which he had an accidental fall. Patient had oral bleeding and bleeding from bite site. He was initially treated in another hospital where his basic investigations were done and his whole blood clotting time was monitored. He was treated with 10 vials of Anti-snake venom (ASV) and 4 units of platelet transfusion. During administration of ASV patient developed facial swelling, hypotension, difficulty in breathing and hoarseness of voice for which he was treated with steroids, adrenaline and antihistamines. He was then referred to our hospital for further management.

On arrival patient was conscious, obeyed simple commands, tachypnoeic, tachycardic and hypotensive, on vasopressor support.

Patient was known to have type 2 diabetes mellitus, and was on oral hypoglycaemic drugs.

On examination, patient was seen to be having non pitting edema over the neck region and swelling of the tongue and lips along with hoarseness of voice and stridor (Fig. 1).

Baseline investigations were done (Table 1). Incidentally patient was also found to be HbSAg positive. 2D echo was done which showed normal LV function and no regional wall abnormality. Twenty minutes whole blood clotting time was monitored based on which ASV was administered. Plain CT head and neck was done which showed soft tissue edema over the oropharynx and laryngopharynx (Figs. 2 and 3). No intra cranial abnormalities were detected. Left lower limb doppler was done for left leg swelling which showed normal study.

Fig. 1: Appearance of the patient, on admission.

Variable	Day 1	Day 3	Day 5
Hemoglobin (g/dl)	9.8	8.5	7.8
Total leucocyte count (cells/mm³)	19,090	13,840	14,100
Platelet count (lakhs/mm³)	1.32	1.20	1.15
Serum creatinine (mg/dl)	1.6	1.4	0.9
PT (seconds)	18.4	13	13
INR	1.62	1.37	1.37
CPK (units/litre)	817	3071	1853

Table 1. Baseline investigations of patient on day 1, day 3 and day 5.

Fig. 2. CT showing soft tissue edema over the oropharynx and laryngopharynx.

Fig. 3. CT showing odema over vocal cord.

Patient was started on antibiotics, proton pump inhibitors, steroids, and antihistamines along with other supportive measures.

In view of worsening breathing mechanics and stridor, difficult airway was anticipated and awake fibreoptic intubation was done. Patient improved symptomatically over a period of two days following which vasopressor support was tapered. Patient was extubated after 2 hours of spontaneous breathing trail and positive cuff leak test.

Discussion

An estimate of about 5 million snake bites occurs in India, according to WHO, resulting in envenomation, in approximately 2.7 million people [1]. The only specific treatment for snake bite envenomation is intravenous administration of ASV.

The total required dose of ASV is usually between 10 vials to 30 vials for haematotoxic cases. It can be given either as a low-dose infusion or high-dose intermittent boluses. In high-dose intermittent bolus regimen, 10 vials of ASV is given stat over 30 min as infusion, followed by 6 vials 6 hourly bolus therapy till clotting time normalizes and/or local swelling subsides. In low dose infusion therapy, 10 vials of ASV for russelâ€™s viper or 6 vials for saw scaled viper is given stat as infusion over 30 minutes followed by 2 vials, 6 hourly as infusion in 100ml normal saline till clotting time normalises [2].

Both acute and delayed reactions are known to occur to ASV. The acute reactions may range from mild urticaria, nausea, vomiting, fever and headache to severe systemic anaphylaxis with hypotension, cyanosis and altered sensorium [3]. Angioedema occurring as a complication of ASV therapy is a rare but known complication. Angioedema can be mast cell mediated or bradykinin induced [4]. Both forms of angioedema can lead to imminent airway obstruction causing a life-threatening emergency [5].

Our patient developed angioedema following administration of ASV. The angioedema was suspected to be due to a histaminergic reaction. In spite of steroid administration, patientâ€™s symptoms progressively worsened. He was not taking any angiotensin converting enzyme inhibitors for hypertension, had no previous history of allergy to any substance or edema of the head and neck regions and also had no family history with similar complaints.

Oropharyngeal angioedema is a potentially life-threatening condition requiring urgent airway evaluation and intervention [6]. Awake fibreoptic intubation is the most common method used to secure airway in patients with angioedema [6]. Cuff leak test and direct laryngoscopy are used to determine eligibility for extubation in patients intubated for angioedema [7].

In our patient difficult airway was anticipated and elective awake fibreoptic intubation was done. Cuff leak test was used to assess the patency of the airway and it helped to mitigate dreaded post extubation complications. With the above airway management and continued use of steroids and antihistamines patient improved steadily and was discharged with advice to follow up.

References

Snake bite in india. https://www.who.int/india/health-topics/snakebite
de Silva HA, et al. Adverse reactions to snake antivenom, and their prevention and treatment. Br J Clin Pharmacol. 2016;81(3):446-52.
Misra L, et al. Angioedema: Classification, management and emerging therapies for the perioperative physician. Indian J Anaesth. 2016;60(8):534-41.
Bernstein JA, et al. Emerging concepts in the diagnosis and treatment of patients with undifferentiated angioedema. Int J Emerg Med. 2012;5(1):39.
Pandian V, et al. Management of difficult airway among patients with oropharyngeal angioedema. Laryngoscope. 2019;129(6):1360-67.
Floyd E, et al. An extubation protocol for angioedema. OTO Open. 2017;1(1):2473974X17691230.

Dr. S. Venkateswaran

Consultant

Angioedema following anti-snake venom administration