Predictive Value of Bedside Clotting Time in Determining the Volume of Antivenom in Patients Bitten by Snake

Abstract

Snake bite is a common problem in Nigeria and indeed in many parts of the world. [1] There seems to be a seasonal variation in the cases of snake bites that are reported. Although snake bite can happen anytime of the year, most reports are noted at the beginning of and during the period of rain. [2,3,4] This is when there is a significant change in the weather and the arrival of rain which fills the holes hence driving the snakes out and also for them to tap sun energy. During this time as well, farmers begin the usual farming season and hence increase in the risk of coming into contacts with several reptiles and rodents among which that with snakes has been noted to be the most dangerous of such encounters. [3] Snake bite can be fatal sometimes despite adequate attention but over the years there has been a decline in the mortality in some places due to prompt initiation of antivenom and other therapeutic measures including analgesics, antibiotics and tetanus toxoid. [2,5,6,7] However, it is of interest to note that it is not all such bites that are from snakes, it is not all bites from venomous snakes that results in envenomation needing the use of antivenom and by all means it is not all snakes that are venomous. [5] Antivenoms has been used from 20mls to 80mls to neutralise envenomation, there is paucity of data indicating the specific amount to be used in any condition of snake bites. [4,7,8] Dosages has been guided by the local and systemic indications for their usage and this may be confusing in rural areas. [8] More so that we have to use the same dosage regardless of the age of the patient since the amount of the venom injected into the host is the same considering the volume of distribution in children and adult or obese and the severely wasted individual. [7] Antivenoms whether monovalent or polyvalent are not entirely safe and sometimes anaphylaxis may happen despite adequate precaution. [6,8] Against this background, we tried to find a relationship between the clotting time done by the bedside and the volume of antivenom required by the patient. We tried to see if it could be possible to use the clotting time to predict the exact amount of the antivenom that will be required in cases of snake bite requiring envenomation. This we hoped may prevent the irregularity in the dosage of the antivenom and help standardize the use of antivenom in every hospital.