Thromboxane mediation of cardiovascular dysfunction following aspiration

Acid aspiration leads to an inflammatory response characterized by the activation and pulmonary entrapment of platelets and while blood cells (WBCs. We speculate that thromboxane (Tx) produced by these activated cells alters lung permeability and diminishes cardiac performance. The lungs of dogs were aspirated with 0.1N HCl (3 ml/Kg). Within 30 minutes in six untreated controls, cardiac index (CI) decreased from 121 to 104 ml/min . kg (P less than ).05), mean arterial pressure decreased from 142 to 120 mm Hg (P less than 0.05), Pao2 decreased from 91 to 73 mm Hg (P less than 0.05), and TxB2 levels increased from 70 to 130 pg/ml (P less than 0.05). Pulmonary WBC sequestration occurred after 2 hours, while at 21/2 hours edema fluid was noted in the endotracheal tube. Six dogs were treated with infusion of the imidazole derivative ketoconazole 1 hour after aspiration (2.5 mg/kg bolus followed by 10 mg/kg . hr for 2 hours). After 30 to 60 minutes of treatment, CI rose from 106 to 143 ml/min . kg (P less than 0.05), TxB2 decreased from 130 to 70 pg/ml (P less than 0.05). At 21/2 hours, plasma from treated animals used to incubate a papillary muscle led to developed tension 8% higher than that in controls (P less than 0.05). Sequestration of WBC was not observed. After 4 hours, 24 ml endotracheal edema fluid was collected in contrast to 127 ml in controls (P less than 0.05). A hamster cheek pouch used for bioassay of microvascular permeability yielded 78 leakage sites/cm2 with control edema fluid and 26/cm2 with fluid from treated animals (P less than 0.05). The importance of WBC Tx synthesis in the induction of permeability was tested by stimulation of isolated WBCs with ionophore in the presence or absence of ketoconazole (0.4 Microgram/ml). Ketoconazole reduced the number of leakage sites in the hamster cheek pouch from 196/cm2 noted in controls to 28/cm2 (P less than 0.05). These data support our hypothesis that Tx directly or indirectly lead to cardiac depression and WBC-mediated permeability.