Malayan Pit Viper Envenomation and Treatment in Thailand

Figures & data

Table 1 Characteristics of Patients with Malayan Pit Viper Envenomation Reported to Ramathibodi Poison Center

Characteristic	n (% of 167 Patients)
Age [years, median (IQR; range)]	40.5 (28.5–56; 1.3–87)
Gender
Male	105 (62.9)
Female	62 (37.1)
Bitten area
Finger	38 (22.8)
Toe	18 (10.8)
Hand	14 (8.4)
Foot	49 (29.3)
Wrist	1 (0.6)
Ankle	26 (15.6)
Arm	2 (1.2)
Leg	11 (6.6)
Shoulder	1 (0.6)
Buttock	1 (0.6)
Multiple site	1 (0.6)
Diagnosis of MPV bite
Brought snake to hospital	96 (57.5)
Able to recognized the type of snake	56 (33.5)
Unknown snakebites which response to MPV antivenin	15 (9.0)

Abbreviations: MPV, Malayan pit viper; IQR, interquartile range.

Figure 1 Patients with Malayan pit viper bite reported to Ramathibodi Poison Center during July 2016 to June 2018. (A) Malayan pit viper bites by region of Thailand. (B) Malayan pit viper bites by month and season. (C) Malayan pit viper bites by time of day (O’clock).

Table 2 Clinical Manifestations of Patients with Malayan Pit Viper Envenomation Reported to Ramathibodi Poison Center

Clinical Manifestations	n (% of 167 Patients)
Local effect	156 (93.4)
Swelling	149 (89.2)
Local pain	79 (47.3)
Bleeding per wound	33 (19.8)
Ecchymosis	32 (19.2)
Bleb	38 (22.8)
Necrosis	22 (13.2)
Hematoma	7 (4.2)
Necrotizing fasciitis	5 (3.0)
Compartment syndrome	12 (7.2)
Systemic effect	147 (88.0)
Prolonged VCT	123 (73.7)
Unclotted 20WBCT	57 (34.1)
Platelet <50,000/mcL	29 (17.4)
INR >1.2	51 (30.5)
Systemic bleeding	14 (8.4)

Abbreviations: MPV, Malayan pit viper; VCT, venous clotting time; 20WBCT, 20-minute whole blood clotting test; INR, international normalized ratio.

Figure 2 Grading of local effects after Malayan pit viper bite reported to Ramathibodi Poison Center during July 2016 to June 2018.

Table 3 Number of Patients with Laboratory Tests and Patients with Abnormal Results (n = 167)

Clotting Test	No. Cases with Laboratory Test	No. Cases with Abnormal Result (% of Cases with Lab Test)
VCT	152	123 (80.9)
20WBCT	99	57 (57.6)
Platelet	162	29 (17.9)
INR	116	51 (44.0)

Abbreviations: VCT, venous clotting time; 20WBCT, 20-minute whole blood clotting test; INR, international normalized ratio.

Table 4 Onset of Systemic Toxicity in Patients with Malayan Pit Viper Envenomation Reported to Ramathibodi Poison Center

Systemic Effects	Median Onset of Abnormality (IQR; Range)
Prolonged VCT	6.5 h (2.75–13 h; 30 min–49 h)
Unclotted 20WBCT	13 h (7–13 h; 10 min–66.5 h)
Platelet < 50,000 mcL	3 h (1–9.5 h; 30 min−18 h)
INR > 1.2	9 h (5–18.5 h; 30 min–96 h)
Systemic bleeding	5.5 h (4.1–22.4 h; 15 min–59 h)
Overall onset of systemic effects	6 h (1.5–12 h; 10 min–96 h)

Abbreviations: VCT, venous clotting time; 20WBCT, 20 minutes whole blood clotting test; INR, international normalized ratio; IQR, interquartile range; h, hour; min, minute.

Figure 3 Cumulative percentage of cases with systemic effect over time.

Table 5 Antivenin Administration for Patients with Malayan Pit Viper Envenomation Reported to Ramathibodi Poison Center (n = 315 Courses)

Antivenin Administration	Course (% of 315 Courses)
Indications
Prolonged VCT	212 (67.3)
Unclotted 20WBCT	73 (23.2)
Platelet <50,000 mcL	30 (9.5)
INR >1.2	42 (13.3)
Systemic bleeding	14 (4.4)
Operative management	1 (0.3)
Appropriate administration	269 (85.4)
Correct indication	293 (93.0)
Appropriate dosage	305 (96.8)
Appropriate duration of infusion	300 (95.2)

Abbreviations: VCT, venous clotting time; 20WBCT, 20-minute whole blood clotting test; INR, international normalized ratio.

Table 6 Allergic Reaction to Antivenin in Patients with Malayan Pit Viper Envenomation Reported to Ramathibodi Poison Center (n = 315 Courses)

Symptoms	Course (% of 315 Courses)
Skin manifestation
Rash	47 (14.9)
Pruritus	6 (1.9)
Angioedema	2 (6.3)
Gastrointestinal manifestation
Nausea and vomiting	9 (2.9)
Abdominal pain	1 (0.3)
Respiratory manifestation
Dyspnea	12 (3.8)
Wheezing lung	14 (4.4)
Chest tightness	19 (6.0)
Hypoxia	5 (1.6)
Cardiovascular manifestation
Hypotension	13 (4.1)

Table 7 Onset of Systemic Toxicity in 17 Pediatric Cases with Malayan Pit Viper Envenomation Reported to Ramathibodi Poison Center

Systemic Effects	Median Onset of Abnormality (IQR; Range)
Prolonged VCT	12.5 h (5–18.5 h, 30 min–32.5 h)
Unclotted 20WBCT	13 h (12–15.25 h, 11–22 h)
INR > 1.2	17 h (15.5–20.75 h, 30 min–41 h)
Overall onset of systemic effects	11 h (5–15 h; 0.5–59 h*)

Note: *One patient presented with gingival bleeding and low platelet count at 59 h after bitten.

Abbreviations: VCT, venous clotting time; 20WBCT, 20 minutes whole blood clotting test; INR, international normalized ratio; IQR, interquartile range; h, hour; min, minute.