Moderate-to-severe Vipera berus envenoming requiring ViperaTAb antivenom therapy in the UK

Figures & data

Figure 1. Time of day (median and IQR), day of the week, and monthly distribution of 170 bites requiring antivenom.

Figure 2. Location of hospitals treating envenomed patients.

Figure 3. Age and sex distribution of cases.

Figure 4. Location of bites for women and men. Circle size is proportional to the number of bites at that site.

Table 1. Systemic features related to age in patients envenomed by V berus subsequently treated with antivenom.

	Children (0–15 years old)	Adults 16–64 years old	Adults > 64 years old	Fisher exact between child/adult <65
Number of cases	38	119	13
Anaphylaxis	2 (5.3%)	20 (16.8%)	1 (7.7%)	p = 0.11
Hypotension	4 (10.5%)	21 (17.6%)	1 (7.7%)	p = 0.44
Diarrhoea	2 (5.3%)	11 (9.2%)	1 (7.7%)	p = 0.73
Vomiting	11 (28.9%)	20 (16.8%)	1 (7.7%)	p = 0.10
Any systemic feature(s)	14 (36.8%)	46 (38.6%)	4 (30.8%)	p = >0.99

NB. Each patient may have had more than one clinical feature of systemic envenoming.

Table 2. Effects and complications of envenoming in patients treated with antivenom.

Clinical complication	Frequency
Bite site ischaemia/necrosis	9 (5.3%)
Blister/bullae	3 (1.8%)
ECG abnormalities	6 (3.5%)
Rash	6 (3.5%)
Blister/bullae	3 (1.8%)
DVT (confirmed by USS doppler)	1 (0.6%)

Figure 5. Time (median and IQR) to presentation, first and second dose of antivenom.

Figure 6. Length of hospital stay for children (<16 years old), adults (16–64 years old) and adults (>64years old). Five values lie outside of the limit of the Y-axis (Children <16 years = 212h, Adults (16-64 years) = 242 h, 254 h and 261 h and Adult (>64 years) = 406 h)

Table 3. Illustrative cases of severe envenoming and learning points.

Case	Time from bite to ViperaTAb (h)	Time to discharge from presentation (h)	Illustrative point	Clinical details
1	21.0 and 66.9	254	Importance of early antivenom.	A female patient developed a sharp pain on her foot whilst walking (unwitnessed bite). She presented to hospital with a diffusely tender, swollen leg, leucocytosis (25 × 10^3/mL) and metabolic acidosis. Snakebite was considered as a differential diagnosis in the emergency department; however, the patient was given IV antibiotics and referred to orthopaedics for assessment of possible necrotizing fasciitis and/or compartment syndrome. No surgical intervention was required. Antivenom was administered 17.5 h after presentation resulting in an improvement in clinical features and biochemistry; however, due to the substantial local effects, the patient required a prolonged period of rehabilitation.
2	4.8	212.7	Importance of compartmental pressure assessment.	A male child presented following a bite to the right foot. Antivenom was given for local effects with no evidence of systemic features. It was adjudged to have been effective and no further doses were administered. The following day, further swelling of the affected limb was noted. He underwent fasciotomy for suspected compartment syndrome without prior radiological or compartmental pressure assessment. In theatre, the muscle was found to be swollen but pink and healthy.
3	3.2, 11.7 and 24.0	242.9	Severe systemic envenoming with anaphylaxis. Importance of compartmental pressure assessment.	Following a bite to the left hand, a male patient presented with perioral paraesthesiae, lip swelling, a sensation of “tight throat” and swelling to the elbow. He was administered IM adrenaline and ViperaTAb, resulting in resolution of systemic features. Over the next 24 h, oedema progressed to the upper arm and onto the thorax despite a further dose of antivenom. Due to clinical concern about compartment syndrome, compartmental pressures were measured and found to be normal (9–10 mmHg). He received a final (third) dose of ViperaTAb and gradually improved with conservative management.
4	7.8, 22.3 and 27.9	142.6	Systemic envenoming with cardiotoxicity. Envenoming associated thrombocytopenia.	A male child presented 3.4 h after sustaining a bite on the right ankle in a rural area. At presentation he was lethargic, complained of abdominal pain, and had ST changes and sinus tachycardia on ECG. Adrenaline and fluids were given as urgent treatment in the emergency department. Bloods revealed a thrombocytopenia (35 × 10^9/ L), raised lactate (2.3 mmol/ L) and metabolic acidosis (pH 7.32). Despite delays due to a lack of antivenom stock at the hospital, his symptoms improved following antivenom administration. The following day the thrombocytopenia had worsened and remained low for a further five days (nadir of 5 × 10^9/ L). Two further doses of antivenom and 1 unit of platelets were administered and the patient observed until sustained improvement in platelets count (80 × 10^9/ L at discharge).
5	3.2 and 5.7	67.3	Severe systemic envenoming. Importance of rapid assessment and treatment.	Within 15 min of a bite to his right hand, the male patient vomited, felt unwell, became drowsy and experienced swelling of his mouth and throat. He was treated at the scene with IM adrenaline before transfer to hospital by air ambulance. Antivenom was administered within 30 min of presentation to hospital. Following antivenom, systemic features resolved. A second dose of antivenom was administered for progressive swelling to the envenomed limb. The patient made a good recovery and was discharged 2 days later.