Maintenance of Cardiodynamics with Aspirin During Abdominal Aortic Aneurysmectomy (AAA)

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Abstract
The importance of prostacyclin (PGI2) 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 h 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 ng/ml to 0.419 .+-. 0.257 ng/ml (P < 0.01) 30 min 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.g/ml to 0.193 .+-. 0.138 ng/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 depressed developed tension (Tpd) of a rat papillary muscle by 16% (P < 0.05); reduction of Ca2+-ATPase and Mg2+-ATPase activity in a rat myocardial subfraction of sarcoplasmic reticulum (P < 0.05) and reduction of Ca2+-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-PGF1.alpha. and TxB2 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. 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. Tx may modulate cardiac depression which can be prevented with 650 mg aspirin before operation.