[Restoration of respiratory function of an organism after cold oppressions without warming].

In experiments on rats studied influence of intravenous introduction NazdTA on respiratory function of rats after the full termination of breath at deep hypothermia. It is shown that such method without warming application it is possible to lower on 1.5-2.0 degrees C a temperature threshold of approach full a cold paralysis of respiratory function of an organism. It confirms the hypothesis put forward earlier about an important role of infringement of balance of ions of calcium in cytoplasm of cells in development of a pathology of an organism at deep hypothermia. The received results can be used at resuscitation of victims accidental hypothermia.

[Resuscitation of vital activity in intensively cooled animals by physiological methods without rewarming].

White rat males (Wistar) were cooled in the water (9-10 °C) to the stop breathing (at rectal temperature 14.7 ± 0.5°, brain 16.0 ± 0.3 °C). After the removal of water animals were injected 0.5% solution disodium salt ethylenediaminetetraacetic acid (Na2EDTA) intravenously, which reduced the concentration of Ca2+ in the blood. Breathing rats were resumed after 4-8 min after administration Na2EDTA. Then one group of rats was cooled to the temperature of the body 12.2 ± 0.7 (brain 14.9 ± 0.3 °C). At such a low temperatures the breath of rats was long-term (2-3 hours) supported at the level of 12 ± 3 cycle/min. The second group of rats was not additionally cooled after the resumption of breathing. The same dose of Na2EDTA caused the rise of the respiratory rate to a higher level--29 ± 4 cycles/min at a temperature in the rectum and the brain 15-16°. Apparently, the process of accumulation of Ca2+ in the cytoplasm of the respiratory center's cells was slowed after the Na2EDTA injection to hypothermal rats in the bloodstream. It is assumed that the Na2EDTA injection under the hypothermia conditions was activated the cell's protection mechanisms from cold damage. The obtained results and the literature data allowed to conclude that nonhibernators are able to maintain basic life functions under significant reduction in the body temperature.

Respiration restitution in rats following its termination in immersion hypothermia.

Rats were cooled in water until attaining profound hypothermia and respiratory arrest. After removal from water, 0.5% solution of Na2EDTA was administered intravenously. This led to a drop of blood [Ca2+] by 20-30% from the baseline and promoted recovery of respiration following its arrest lasting 10.3±1.4 min. By the 30th minute of Na2EDTA administration, respiration rate increased to 32.3±5.2 cycles per minute and respiration amplitude reached 68±4% of the baseline level. This effect was observed without special warming of the rats. It was concluded that the period during which the organism maintains viability in respiration arrest and disturbances in respiratory center are still reversible is prolonged under conditions of profound hypothermia.

[Cold pathology and experimental therapy of deep hypothermia].

A complete cold paralysis of respiration and thermoregulation occurs in rats at the temperature in the brain 16.6 +/- 0.3 and in the rectum 15.2 +/- 0.3 degrees C. Under the conditions of room temperature 18-19 degrees C, the respiration never restores, and the animals die. This is believed [6] to be the result of calcium ion Ca2+ accumulation in the cells of respiration and thermoregulation centers. After the arrest of respiration the animals were injected with the solution of disodium salt of ethylenediaminetetraacetic acid (Na2EDTA), which binds calcium ions in the blood and facilitates their removal from the cell (explanations in the text). In 7-9 min after the injection the calcium content in the blood decreased and the respiration began to restore at the temperature of the cold paralysis. Thermoregulation was also restored. All the test animals survived. All the control animals, which were not injected with Na2EDTA, died.