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

The importance of prostacyclin (PGI ₂) and thromboxane (Tx) mediation 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 PGI ₂, 6-keto-PGF(1α) rose from 0.050 ± 0.032 νg/ml to 0.419 ± 0.257 νg/ml (p < 0.01) 30 minutes after the skin incision. The stable metabolite of TxA ₂, TxB ₂ did not increase until the aorta was clamped when TxB ₂ rose from 0.089 ± 0.054 νg/ml to 0.193 ± 0.138 νg/ml (p < 0.05); this was prior to blood transfusion. During aortic clamping cardiac output decreased 27% (p < 0.001). In vitro testing of patient plasma showed: 1) depressed developed tension (Tpd) of a rat papillary muscle by 16% (p < 0.05); 2) reduction of Ca ⁺⁺-ATPase and Mg ⁺⁺-ATPase activity in a rat myocardial subfraction of sarcoplasmic reticulum (p < 0.05); 3) reduction of Ca ⁺⁺-ATPase in a rat myocardial subfraction of myofibrils (p < 0.01). Aspirin administered to 11 patients produced no measurable change in blood loss or fluid requirements. Aspirin lowered preoperative 6-keto-PGF(1α) and TxB ₂ levels (p < 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 TxB ₂ when added to a papillary muscle or myocardial subfractions, did not decrease Tpd or ATPase suggests that TxB ₂ plays an indirect role in altering cardiac muscle activity. The results indicate that Txs modulate cardiac depression, which can be prevented with 650 mg apsirin before operation.