[Changes in blood gas parameters of heatstroke rats in dry-heat environment of desert]

To investigate the changes in characteristics of blood gas analysis of heatstroke rats residing in dry-heat environment of desert, and to provide a theoretical reference for its treatment in clinic.

Forty-eight male Sprague-Dawley ( SD ) adult rats under anesthesia were divided into six groups by random number table, with 8 rats in each group: namely mild, moderate, severe heatstroke groups and their corresponding control groups. The rats were placed in an artificial chamber with simulated desert dry-heat environment ( temperature 41 centigrade, humidity 10% ) for about 70, 110, 145 minutes, respectively, to reproduce mild, moderate, severe heatstroke models. The rats in control groups were placed in a normothermic environment for corresponding duration. Abdominal aorta blood of each group was collected for blood gas analysis, and electrolytes were determined by a portable blood gas analyzer.

(1) Arterial partial pressure of carbon dioxide ( PaCO(2) ) in mild heatstroke group was increased to ( 45.64±8.19 ) mmHg ( 1 mmHg = 0.133 kPa ), arterial oxygen saturation ( SaO(2) ) was decreased to 0.84±0.08, pH value was lowered to 7.36±0.11, showing that respiratory acid-base imbalance was resulted. Base excess of extracellular fluid ( BEecf ) in moderate heatstroke group was decreased to ( -3.00±0.76 ) mmol/L, HCO(3)(-) was decreased to ( 19.39±1.89 ) mmol/L, and pH value was lowered to 7.21±0.07, indicating that metabolic acid-base imbalance was aggravated gradually. The changes in parameters in severe heatstroke group gradually became more serious, and a significant difference was found as compared with those of mild and moderate heatstroke groups ( PaCO(2): F = 6.537, P = 0.006; SaO(2): F = 5.174, P = 0.015; pH value: F = 10.736, P = 0.001; BEecf: F = 67.136, P = 0.000; HCO(3)(-): F = 5.612, P = 0.011 ), manifesting an obvious combination of respiratory acidosis and metabolic acidosis, and a serious mixed acid-base disturbance was produced. (2) Compared with corresponding control groups, hemoglobin ( Hb ) was significantly increased in moderate heatstroke group ( g/L: 15.31±1.84 vs. 13.28±0.94, t = 2.791, P = 0.014 ), Hb and hematocrit ( HCT ) in severe heatstroke group were significantly increased [ Hb ( g/L ): 16.59±2.52 vs. 13.42±1.15, t = 3.224, P = 0.006; HCT: ( 53.50±6.63 )% vs. ( 45.50±4.47 )%, t = 2.828, P = 0.013 ], showing that the degree of dehydration was aggravated gradually from mild to serious degree. (3) Serum sodium content in mild heatstroke group was normal ( t = 0.665, P = 0.517 ), serum potassium content was lowered significantly ( t = -2.526, P = 0.024 ); serum sodium content in moderate heatstroke group was increased significantly ( t = 2.162, P = 0.048 ), serum potassium content was lowered significantly ( t = -5.458, P = 0.000 ); and serum sodium content in severe heatstroke group rose obviously ( U = 12.500, P = 0.038 ), and most of the rats showed hypokalemia, with a small proportion of rats showed obvious hyperkalemia ( U = 19.500, P = 0.195 ).

Acidosis, electrolyte disturbance, respiratory failure and dehydration in heatstroke occurred in dry-heat environment of desert. It indicates that resuscitation should focus on correction of respiratory acidosis, with simultaneous correction of metabolic acidosis, and one should be alert to correct dehydration and electrolyte disturbance. During the moderate phase and the serious phase, correction of aggravated metabolic acidosis should be reinforced, and the prevention and treatment of the severe dehydration and electrolyte disturbance should be undertaken actively.