Stoidela and others: you might be interested in reading report here Ketamine/NDEs.
Basically, NDEs can be reproduced in fully alive, healthy, normal humans with the proper dosage of ketamine, a popular anesthetic. No one is sure of the exact mechanism by which ketamine produces this experience, but this paper was published in 1996, so there may be some new info I’ve not seen yet. For those who don’t know, ketamine is a very seriously abused drug, commonly known as ‘Special K’, valued for its overall safety and fascinating hallucinatory experience. Ketamine is a congener of phencyclidine (PCP), if that rings any bells.
Ketamine has been a very popular veterinary anesthetic, especially for cats (for whom we have very few safe and effective drugs). However, cats anesthetized with ketamine usually have a VERY rough recovery, and 20% of these cats will have seizures following ketamine use. My own veterinarian switched to Telazol as an induction agent after two of my kittens suffered an extreme ketamine reaction that included attempts to rip their faces off. 
Anyway, since NDEs can be induced through ketamine use alone, I see no basis for assigning any spiritual or mystical significance to NDEs that occur otherwise. There is obviously a natural, normal, chemical basis for the experience. One theory points to the fact that ketamine/PCP binds to a site that, when blocked, prevents neuronal cell death due to excitotoxicity in conditions of low blood oxygen, low blood sugar, etc. NDEs may simply be the result of the body’s attempt to prevent brain damage.
I’m adding here some pertinent quotes from the above referenced paper:
“The intravenous administration of 50 - 100mg of ketamine can reproduce all of the features which have commonly been associated with NDE’s.”
“Mounting evidence suggests that the reproduction/induction of NDE’s by ketamine is not simply an interesting coincidence. Exciting new discoveries include the major binding site for ketamine on brain cells, known as the phencyclidine (PCP) binding site of the NMDA receptor . . .”
“The present author has experienced several NDE’s and has also been administered ketamine as an anesthetic and within experimental paradigms. The NDE’s and ketamine experiences were clearly the same type of altered state of consciousness. Ketamine repeatedly produced effects which were like the NDE’s described by Moody (1975), Noyes and Kletti (1976a), Greyson and Stevenson (1980), Ring (1980), Sabom (1982), and Morse et al., (1985). Ketamine reproduced travel through a tunnel (sometimes described as ‘the plumbing of the world’ or in mundane terms such as ‘like being on a subway train’), emergence into the light, and a ‘telepathic’ exchange with an entity which could be described as ‘God’. Neither the NDE’s nor the ketamine experiences bore any resemblance to the effects of psychedelic drugs such as dimethyltryptamine (DMT; also administered to the author in experimental paradigms) and lysergic acid diethylamide (LSD).”
“Much has been made of the apparent mystery surrounding the occasional ability of cardiac arrest survivors to describe the resuscitation in detail (Saborn, 1982). It is worth noting that ketamine can permit sufficient sensory input to allow accounts of procedures during which the patient appeared wholly unconscious (Siegal,1981; Hejja and Galloon, 1975). These reports are not regarded by anaesthetists as particularly mysterious.”