Conn A W, Miyasaka K, Katayama M, Fujita M, Orima H, Barker G, Bohn D
Department of Anesthesia, National Children's Medical Research Centre, Tokyo, Japan.
Crit Care Med. 1995 Dec;23(12):2029-37. doi: 10.1097/00003246-199512000-00012.
To compare the pathophysiologic changes occurring during drowning in cold fresh water and cold salt water with reference to viability.
Randomized, prospective, controlled submersion experiments in two contrasting cold liquids.
A laboratory at a large university-affiliated medical institution.
Thirteen healthy, anesthetized mongrel dogs. Three dogs served as controls and were immersed but not submerged. The remainder were submerged in cold fresh water or cold salt water (4 degrees C).
Catheters were placed in the femoral artery, right carotid artery and right internal jugular vein. Electrocardiogram, pneumogram, and rectal temperatures were measured continuously during submersion/immersion.
Cold water submersion with drowning produced a large initial decrease in carotid artery temperature (approximately 7.5 degrees C in the first 2 mins) compared with a minor decrease (approximately 0.8 degrees C with immersion). No significant differences were noted in the rate of decrease of temperature between drowning in fresh water and salt water. During cold fresh water drowning, aspiration produced gross hemodilution with an average increase in body weight of 16.5%. Hematocrit values, serum sodium concentrations, and osmolality decreased while serum potassium concentrations, catecholamines, and free hemoglobin increased. All measured biochemical data (except PaO2) remained at viable levels. By contrast, during cold salt water drowning, average body weight increased by only 6%, with hemoconcentration and a shrinkage of vascular volume. Hematocrit and hemoglobin values increased by 30%, but initial plasma free hemoglobin values remained unchanged. Serum sodium concentrations, osmolality, and potassium concentrations increased rapidly to critical levels.
On submersion in cold water, all of the experimental animals developed tachypnea immediately, followed by aspiration with predictable effects. The biochemical and pathophysiologic changes in cold water drowning approximated those changes reported for warm water drowning for both fresh and salt water with one exception and continued aspiration of cold water produced extremely rapid core cooling as long as the circulation remained intact. This process of acute submersion hypothermia may protect the brain temporarily from lethal damage, as reported in cases of cold fresh water drowning. Concentrations of circulating catecholamines increased exponentially in both groups of test animals. Clinically, their acute effects on the circulation, compounded by significant hypothermia and extreme anoxia, must hamper the detection of residual circulation at rescue and may play a role in sudden death from cold water in the absence of drowning.
参照生存能力，比较冷淡水和冷盐水溺水时发生的病理生理变化。
在两种不同的冷液体中进行随机、前瞻性、对照性浸没实验。
一所大型大学附属医院的实验室。
13只健康、麻醉的杂种犬。3只犬作为对照，仅浸入但不浸没。其余犬浸没于冷淡水或冷盐水中（4℃）。
将导管插入股动脉、右颈动脉和右颈内静脉。在浸没/浸入过程中持续测量心电图、呼吸图和直肠温度。
与浸没时体温轻度下降（约0.8℃）相比，溺水导致的冷水浸没使颈动脉温度最初大幅下降（最初2分钟内约7.5℃）。淡水溺水和盐水溺水时体温下降速率无显著差异。在冷淡水溺水过程中，吸入导致明显的血液稀释，体重平均增加16.5%。血细胞比容值、血清钠浓度和渗透压降低，而血清钾浓度、儿茶酚胺和游离血红蛋白增加。所有测量的生化数据（除PaO2外）均保持在可存活水平。相比之下，在冷盐水溺水过程中，体重仅平均增加6%，伴有血液浓缩和血管容积缩小。血细胞比容和血红蛋白值增加30%，但最初的血浆游离血红蛋白值保持不变。血清钠浓度、渗透压和钾浓度迅速升至临界水平。
浸入冷水中时，所有实验动物均立即出现呼吸急促，随后发生吸入，产生可预测的影响。冷水中溺水的生化和病理生理变化与温水溺水（包括淡水和盐水）报道的变化相似，但有一个例外，只要循环保持完整，持续吸入冷水会导致核心体温极其迅速地下降。如冷淡水溺水病例报道的那样，这种急性浸没性体温过低过程可能会暂时保护大脑免受致命损伤。两组实验动物循环儿茶酚胺浓度均呈指数增加。临床上，它们对循环的急性影响，再加上显著的体温过低和极度缺氧，必然会妨碍救援时对残余循环的检测，并且可能在无溺水情况下的冷水猝死中起作用。
