Prehospital Treatment for Rattlesnake bite
This is taken out of the latest Medical literature. Kind of lenthy but answers a lot of Q's
The prehospital phase of snakebite treatment is fraught with myth and dangerous practices that can contribute to the morbidity of the patient. The most important steps to ensure a good outcome include immobilization and rapid transport of the victim for evaluation by trained medical personnel. Hardy  found delay in obtaining medical care to be a common denominator among victims who died following a rattlesnake bite. It is not absolutely necessary to identify the snake to initiate treatment of the patient following bites by indigenous crotalids in North America. Thorough examination and proper observation dictate treatment of crotalid bites regardless of the species involved. Rescuers and the victim should not place themselves at risk of a second bite in an attempt to capture or kill the snake. If the snake has been killed, it should be transported with the patient in a closed container. Killed snakes (even decapitated heads) have been reported to cause severe envenomation.  
Animal studies have demonstrated that survival is improved when immobilization was performed.   In human volunteers, the progress of radiotracer (simulating snake venom) was followed using lymphoscintigraphy. The radiotracer's rate of transit increased significantly following a short time of walking when injected either into upper or lower extremities.  Obviously, if walking is required in order to reach medical care, then the patient should be allowed to walk. Medical care should not be delayed only for the purpose of keeping the patient from moving.
Although splinting of the envenomated extremity may be beneficial,  Wingert and Chan  did not find a benefit to other first aid measures, such as incision, cryotherapy, tourniquets, and suction. These are discussed more fully later. The focus should be directed toward immediate access to professional medical care.
Cryotherapy and Heat Application
In theory, the application of either heat or cold was thought to be beneficial. Cryotherapy was believed to decrease venom enzymatic activity and slow humoral responses and was once considered standard prehospital care.   Some authors even suggested that cryotherapy be continued for as long as 3 days.  The use of ethyl chloride, Freon, and fire extinguishers containing carbon tetrachloride or carbon dioxide was recommended if ice was not readily available.   On the other hand, the application of heat was suggested to increase blood flow to the bite and, subsequently, disseminate the venom from the site and minimize local tissue necrosis. In animal models, however, no decrease in tissue necrosis was demonstrated with either heat or cold application.   In addition, further tissue necrosis as a result of these therapies can occur. Therefore, ice, cryotherapy, or heat application is not recommended.
Pressure immobilization is a technique that has been advocated for the treatment of non-pit viper bites in Australia.      In this method, a broad elastic bandage is applied over the clothing at the bite site. It is then wrapped proximally over the entire extremity, which is then splinted (extremity wrap). It is believed that the combination of lymphatic compression and reduction of lymph flow retards venom distribution. The range of pressure to impede flow, however, is narrow (40 to 70 mm Hg for the upper limb, and 55 to 70 mm Hg for the lower limb).  Lower pressures do not compress the lymphatics adequately, and higher pressures may impede venous and arterial flow and increase patient discomfort and movement to the point where venom absorption is actually enhanced.
Although compression therapy may be of benefit for patients bitten by Australian elapids,      no studies have demonstrated benefit for animals or humans bitten by crotalids. Furthermore, tissue necrosis from crotalids is the most common permanent morbidity, and necrosis might be enhanced by forcing venom to remain concentrated in the bitten extremity. Therefore, application of a compression bandage (extremity wrap) is not recommended for crotalid bites. 
The role of tourniquets (ligatures) and constrictive bands in snakebite prehospital therapy has been highly debated in the past. The placement of a tourniquet was considered the standard of prehospital care for the snakebite victim years ago.  Some believed that tightening the
tourniquet to the point of pain was the most effective therapy.  The dangers of arterial tourniquets became apparent and they fell from favor with the suggestion that constrictive bands just tight enough to occlude the lymphatics be used.   Continued concern, however, regarding vascular compromise by any constrictive device and the apparent lack of proven efficacy has led to the recommendation that no band should be placed on the extremity of a crotalid snakebite victim.  We are unaware of any scientific animal or human studies that demonstrate a beneficial change in clinical outcome with the use of constrictive bands following crotalid envenomation. A tourniquet can produce an arterial thrombosis in snake bite victims. 
Incision and Suction
Incision and suction have been recommended over the years by various authors.     Early experimental animal models demonstrated that a fraction of the snake venom could be removed if incision and suction were performed within the first few minutes after the bite.  Subsequent animal models, however, have failed to demonstrate a clinical benefit to this procedure.  The possible complications to this procedure are numerous and include damage to tendons, muscles and nerves, and hemorrhage.  The chance of wound infection is also increased, both from the instrument used and by contamination of oral flora when sucking out the venom. The authors have cared for patients with self-inflicted neurovascular injuries requiring surgery, but who suffered dry bites. Because of lack of proved clinical benefit and potential for complications, incision and suction are not recommended.
Snake Venom Extractors
Extraction kits are available that create a negative pressure over the wound and therefore require no previous incision. These are plunger devices intended to extract venom back through the bite wound.  In essence, the puncture wounds of snakebites are small and the venom injected diffusely into tissue. Although experiments in animals have shown that suction and extraction may remove some venom when used within 3 minutes of the bite,   no studies have demonstrated improvement in morbidity or mortality in animals or humans with the use of extractors.  If used as an unproved first-aid measure, care should be taken to be sure that such use does not delay obtaining medical therapy.
Electric Shock Therapy
The suggestion that electric shock therapy might be effective for treatment of snake bite began last century and once again resurfaced in 1986 in a letter published in Lancet. The authors reported anecdotal experience in the use of electric shock therapy on 34 snake bitten patients in the eastern Amazon jungles of Ecuador, where dry bites are more common than in North America following crotalid envenomations, and where villagers commonly possess snake venom antibodies from previous bites. This letter stimulated a flurry of responses, and subsequent articles and letters in both medical journals and nonmedical magazines advocated this procedure without proof for efficacy.    Other authors proposed the pathophysiologic mechanism supporting this therapy.  Subsequent experiments with various animal models, however, failed to find any benefit in the use of this modality.       In addition, specific case reports have emphasized the danger of attempting to use electric shock.   Electric shock therapy has no valid role in the treatment of crotalid envenomation.