There are two aims of first aid measures in accidents with venomous and poisonous animals:
- delaying the harmful and in particular the life-threatening effects of such an accident until medical care is at hand;
- alleviation of symptoms, in particular fear and pain.
First aid measures must be practicable, all the more in the case of accidents with venomous and poisonous animals, the vast majority of which occur far from medical care facilities.
The development of optimal methods only represents the first step in solving the problems of first aid. By far the more difficult task is making these methods available. In the regions of the world most affected by accidents with venomous and poisonous animals, there are numerous obstacles to the successful dissemination of an appropriate first aid measure. There needs to be a dissemination strategy that reaches the affected sections of the population. If the method in question requires particular resources, these need to be available as soon as an accident occurs. However, most of the first aid strategies that are currently considered optimal fail to fulfill one or more of these criteria, at least in those regions most affected by accidents with venomous and poisonous animals.
Numerous first aid methods have been proposed, but very few have been systematically tested or validated in field studies. In this section, those first aid methods are described for which there is broad consensus among experts and that have been tested at least to the extent that the efficacy and risks can be estimated and serious adverse effects can be excluded (Currie 1992, Theakston 1992, Warrell 1990b, 1992a, b). However, this does not solve the problems that may cause these methods to fail when they are used in specific regional conditions.
Cnidarians (Jellyfish, Corals and Anemones)
Venomous fish
Scorpions
Spiders
Hymenopterans (Bees, Wasps and Ants)
Terrestrial venomous snakes (choose respective region)
1. Calming the patient
Fear (fear of death) can be the dominant symptom following a snakebite. Movement and activity associated with fear may speed up transport of the venom (muscle pump).
2. Immobilisation of the bitten extremity
Immobilisation of an extremity can be achieved with any form of stick or pole. Strips of clothing can be used to fix the extremity to the splint. If the bite is on the arm, a sling can also be used to immobilise the limb. Care needs to be taken that no pressure points develop and that the blood circulation is not compromised. Immobilisation can considerably retard the absorption and transport of certain venom components. The efficacy of this method has been experimentally proven for large-molecular-weight venom components, chiefly haemostatic toxins, transported by the lymphatic system. However, the absorption and transport of low-molecular-weight venom components, e.g. neurological toxins from cobras, are not influenced by this method (Barnes and Trueta 1941). This fact alone results in practical problems. In most cases the snake that caused the bite is not seen. Thus, in regions in which there are snakes whose venoms have both neurological and haemostatic effects, the success of immobilisation alone is not predictable. Regional knowledge and experience can be helpful to a certain extent, in that they may make it possible to narrow down the species that caused the bite with the use of indirect, e.g. ecological, criteria (→ "How to manage a snake bite").
3. Compression-immobilisation method
A compression bandage is applied to the entire bitten extremity with the use of a wide elastic bandage. The pressure applied should be around 55 mmHg. This pressure is above the venous pressure in the leg in the supine position (10–25 mmHg), but not standing (90 mmHg)! The extremity is then also immobilised in the manner described above. Concurrent immobilisation of the extremity is necessary for the method to be fully effective.
This method, developed by Sutherland et al. in Australia, is convincing in many regards (Sutherland et al. 1979, 1980). Delay of the absorption and transport of neurological and haemostatic venom components has been experimentally proven. However, problems do occur with this method, especially when it is used outside of Australia and the Pacific Islands. Furthermore, this method has also never undergone formal clinical evaluation. Apart from this, the availability of elastic bandages is not guaranteed in most circumstances and is also not achievable. Strips of cloth are not a fully adequate alternative, as the desired pressure is even more difficult to control than with elastic bandages, and the danger of the bandage twisting and cutting into the limb is even greater. The greatest danger of compression bandages arises when they are used for bites by snakes whose venom contains components that cause local effects. If venoms that cause soft tissue necrosis are held in one place, there may be a dramatic increase in tissue damage. This is chiefly to be expected with most viperid and crotalid bites, but also with certain elapid bites. Distal ischaemia, in the most extreme case gangrene of an entire extremity, must be feared if the compression bandage is applied too tightly. This can also occur if the pressure under the compression bandage increases due to progressive swelling in critical regions. Because optimal application of the compression-immobilisation technique can very effectively retard transport of the venom, a bolus effect is to be expected when the bandage is removed. At this point, a large quantity of the retained venom is suddenly released into the systemic circulation and there is an abrupt and vigorous onset of the symptoms of envenoming. Thus, it is essential that all preparations for the administration of general and specific treatments are made before removal of the splint and bandage. There must be intravenous access with a running infusion, the specific antivenom must be ready for immediate administration and general emergency medical measures, such as endotracheal intubation, ventilation and treatment of anaphylactic shock, must be immediately available.
The use of the immobilisation-compression technique is unreservedly justified and can be life-saving in the case of bites from snakes whose venom causes neurological effects:
- Elapids: Aspidelaps scutatus, *kraits (Bungarus spp.), numerous species of cobra (Hemachatus haemachatus, *Naja haje, N. melanoleuca, *N. nivea, N. atra, N. kaouthia, N. naja, *N. philippinensis, Ophiophagus hannah), coral snakes (Micrurus spp.), *mambas (Dendroaspis spp.);
- Australian elapids: the genera *Acanthophis, *Micropechis, *Notechis, *Oxyuranus, Pseudechis (signs of paralysis due to rhabdomyolysis), Tropidechis, *Pseudonaja;
- *Sea snakes (Hydrophiidae).
According to current knowledge, only with the snakes marked by an asterisk (*) can local swelling and local necrotic effects of the venom be largely or definitely excluded. With regard to all the other snakes listed above, the risk of additional local tissue damage due to the compression-immobilisation technique is consciously accepted in order to achieve the benefits of delaying the life-threatening neurological effects of the venom. For some of the snakes listed above, there are additional benefits of immobilisation/compression with regard to delaying the haemostatic and/or skeletal muscle-damaging effects of their venoms (Notechis, Oxyuranus, Pseudechis, Pseudonaja, Tropidechis).
4. Transporting the patient
The patient must be taken as quickly as possible to the closest place in which he/she can be assessed by a medically trained person. The transportation should involve no physical effort on the part of the patient. This measure is also aimed at slowing down entry of the venom into the systemic circulation in association with physical activity. If no vehicle is available, the patient can be carried on a stretcher, which, if need be, can be made on the spot from simple materials. If only one helper is available, the patient must be carried on the helper's back, if he/she has the strength to do so.
5. Presentation of the dead snake
If it is possible to do so without danger, it is very helpful for the purposes of choosing the appropriate antivenom and assessing the expected complications if the snake that caused the bite is brought along to the medical facility. It is necessary to be aware that a snake may be mistakenly assumed to be dead and also that it is still possible to be bitten even once the snake's head has been cut off.
Dangerous and contra-indicated first aid measures
Among the great number of first aid measures for which there is no foundation and many of which can even cause considerable additional damage, the following are most relevant:
- Tourniquets, in particular arterial tourniquets, that are not applied on the basis of clearly defined criteria. The criteria in favour of a tourniquet, preferably the compression-immobilisation method, are given above. However, occlusive bandages carry the following risks: ischaemia and gangrene of the extremity, damage of superficial nerves in particular, intensification of local venom effects, increased fibrinolytic activity in the congested extremity, swelling, bleeding from injuries in the congested extremity, a bolus effect with abrupt and vigorous onset of the symptoms of envenoming after removal of the bandage.
- Interfering with the bite wound, beyond cleaning it and covering it with a clean cloth. In regions in which ELISA tests for the identification of snakes with the aid of their venom are available, e.g. Australia, wound extrudates that have seeped into the cloth covering the wound should be retained. The following have particularly damaging consequences: wound incisions, ice (so-called cryotherapy), injection or instillation of substances, for example calcium permanganate. The same is true for the local application of electric shocks, which is still claimed to be effective despite an absolute lack of evidence.
- Traditional treatment methods found in all regions of the world. These must also be viewed with scepticism, as they also include methods that are known to have extremely damaging effects. Moreover there is the danger of a considerable delay before specific treatment is administered.