CARDIOVASCULAR EFFECTS OF THORACIC COMPRESSION IN HORSES SUBJECTED TOEUTHANASIA

Six horses scheduled for euthanasia were instrumented for the measurem ent of blood flow by thermodilution, pulmonary arterial, right atrial and arterial blood pressures and collection of arterial blood for pH a nd blood gas analysis. The horses were anaesthetised with intravenous (iv) thiamylal sodium (10 mg/kg) and placed in right lateral recumbenc y. After euthanasia with an overdose of pentobarbitone sodium (100 mg/ kg, iv) and loss of the electrocardiogram and arterial pulse pressure. thoracic compression at rates of 40, 60 and 80 compressions/min was i nstituted. Thoracic compression was accomplished by an investigator wh o delivered a blow to the chest wall with his knee while dropping from a standing or crouching position. Compression rates of 40, 60 and 80/ min produced blood flows of 5.65 +/- 0.5, 6.33 +/- 1.11 and 8.28 +/- 2 .16 litres/min, respectively. Compression rates of 80/min produced sig nificantly (P<0.05) greater blood flows and mean arterial blood pressu res than did slower rates. The blood flows produced by 80 thoracic com pressions/min were approximately 50% of those reported for deeply anae sthetised horses and while not sufficient to sustain life might be use d to prolong life in order to facilitate distribution of resuscitative drugs to vital tissues.