There was a study by another group that states that hot water helps with pain but does not prevent necrosis. This suggests that the venom components responsible for tissue necrosis may be heat resistant.
Here's a section of the abstract:
Skin necrosis was observed in a high percentage of the victims, mostly fishermen and bathers. The initial therapeutic procedures, like immersion of the affected member in hot water were effective in the initial phases of the envenoming, especially in the control of the acute pain; however, they did not prevent skin necrosis.
Haddad V et al. - Freshwater stingrays: study of epidemiologic, clinic and therapeutic aspects based on 84 envenomings in humans and some enzymatic activities of the venom. Toxicon 2004 Mar 1;43(3):287-94
I remember reading another study that stated that if mucus from the stinger was included with the venom it caused significantly more necrosis. I can't remember the reference for that one right now.
Here's a section of the abstract:
Skin necrosis was observed in a high percentage of the victims, mostly fishermen and bathers. The initial therapeutic procedures, like immersion of the affected member in hot water were effective in the initial phases of the envenoming, especially in the control of the acute pain; however, they did not prevent skin necrosis.
Haddad V et al. - Freshwater stingrays: study of epidemiologic, clinic and therapeutic aspects based on 84 envenomings in humans and some enzymatic activities of the venom. Toxicon 2004 Mar 1;43(3):287-94
I remember reading another study that stated that if mucus from the stinger was included with the venom it caused significantly more necrosis. I can't remember the reference for that one right now.
