Use of phasic abdominal compression on rats with cardiac arrest in normothermia.

Rats were given excess ether to respiratory and cardiac arrest. One to five minutes after cardiac arrest cardiovascular assistance was attempted with manual abdominal compression, abdominal compression with neck constriction or phasic abdominal compression. Phasic abdominal compression was chosen as the method for further experimentation because it restarted the hearts of 8 out of 11 of the animals studied without raising right atrial pressures high enough to damage the lungs. It was applied externally to the abdomen and lower extremities of the animals with an adult sized blood pressure cuff. The cuff was inflated to a pressure of 100 mm. Hg at a frequency of 240 cycles per minute with compressed air. The maximum heart rate achieved by the animals was positively correlated with the frequency of phasic external compression (r = 0. 59). Following the collapse of blood pressure but before cessation of cardiac electrical activity due to anaesthetic overdose, artificial respiration (40 per min. ) plus phasic compression induced an increase in the rate of cardiac contraction to 200 to 250 beats per min. and a rise in the mean blood pressure of 100 +- 24 mm. Hg. One to five minutes after cardiac arrest phasic compression restarted the hearts of 70 out of 80 rats (88%). Compression plus intraarterial injections of noradrenaline (0. 5 ug. ) raised the blood pressures of 45 of 80 rats (56%) to a mean pressure of 90 +- 20 mm. Hg. Spontaneous respiration resumed in 20 of 35 (57%) of the rats allowed to recover after phasic abdominal compression. Measurement of arterial blood PO2, PCO2, pH, lactate, Na+ and K+ indicated that the acutely anoxic condition of the rats at cardiac arrest was reversed if the blood pressure rose during phasic abdominal compression. Determination of aortic and cardiac Na+ , K+ , glucose, lactate, ATP and PCr showed that the low energy state produced at cardiac arrest was reversed if the blood pressure rose