Maintenance of cardiodynamics with aspirin during abdominal aortic aneurysmectomy (AAA)

The importance of prostacyclin (PGI2) and thromboxane (Tx) medication of depressed cardiac performance during abdominal aortic aneurysm operative surgery was studied by contrasting the effects of 650 mg aspirin administered 12 hours before operation to that of a placebo. In 11 patients who received a placebo, the stable metabolite of PGI2, 6-keto-PGF1 alpha rose from 0.050 +/- 0.032 eta grams/ml to 0.419 +/- 0.257 eta grams/ml (p less than 0.01) 30 minutes after the skin incision. The stable metabolite of TxA2, TxB2 did not increase until the aorta was clamped when TxB2 rose from 0.089 +/- 0.054 eta grams/ml to 0.193 +/- 0.138 eta grams/ml (p less than 0.05); this was prior to blood transfusion. During aortic clamping cardiac output decreased 27% (p less than 0.001). In vitro testing of patient plasma showed: 1) depressed developed tension (Tpd) of a rat papillary muscle by 16% (p less than 0.05); 3) reduction of Ca++-ATPase and Mg++-ATPase activity in a rat myocardial subfraction of sarcoplasmic reticulum (p less than 0.05); 3) reduction of Ca++-ATPase in a rat myocardial subfraction of myofibrils (p less than 0.01). Aspirin administered to 11 patients produced no measurable changes in blood loss or fluid requirements. Aspirin lowered preoperative 6-keto-PGF1 alpha and TxB2 levels (p less than 0.01) and prevented an increase of either agent during operation. The low Tx levels were associated with a stable cardiac output during aortic clamping. Further, plasma obtained from aspirin-treated patients did not depress papillary muscle contractility nor decrease ATPase activity of either myocardial subfraction. The observation that TxB2 when added to a papillary muscle or myocardial subfractions, did not decrease Tpd or ATPase suggests that TxB2 plays an indirect role in altering cardiac muscle activity. The results indicate that Txs modulate cardiac depression, which can be prevented with 650 mg aspirin before operation.