Modification of controlled hypotension induced by nicardipine or nitroprusside in cats pretreated with injectable acetyl salicylic acid

Controlled hypotension is a well established technique to decrease blood loss and improve surgical visibility. Several different pharmacologic agents have been used for controlled hypotension including direct acting vasodilators such as sodium nitroprusside and calcium channel blockers (Testa and Tobias, l995) . This study was designed to assess the effect of non-steroidal anti-inflammatory drug (NSAID) acetyl salicylic acid (ASA) therapy on the efficacy and safety of I.V. infusion of nicardipine compared with the more commonly used agent; sodium nitroprusside. The effect of each drug on blood pressure and ECG pattern of normalcontrol cats and cats pretreated with (ASA) was investigated. A target mean arterial pressure (MAP) of 55-65 mmHg was to be achieved. It was found that both nicardipine and nitroprusside achieved a stable controlled hypotensive state in control groups. Comparison between the two drugs revealed a significant increase in (MAP) with nitroprusside after drug discontinuation. Pretreatment with (ASA), attenuated significantly the effect of nicardipine infusion on (MAP) . However, pretreatment with ASA produced insignificant effect on the decrease in MAP caused by nitroprusside except at 4 min. during infusion where ASA pretreatment attenuated its effect. Moreover (ASA) pretreatment decreased nitroprusside dose needed to reach the target blood pressure and increased time of blood pressure to returin to base line. Both nicardipine and nitroprusside infusion caused increase in mean heart rate (HR) without ECG changes in control and pretreated groups.There was a Statistically significant increase in (HR) in the (ASA) pretreated groups of both drugs when compared to that in the control groups. When the increase in (HR) induced by nitroprusside infusion was compared to that induced by nicardipine infusion, there was insignficiant difference in the control groups, difference was significant. INTRODUCTION: One of the commonly used technique to limit blood loss and the possibility of transmitting infectious diseases in orth -opedic surgical procedures is controlled hypotension. Controlled hypo -tension; referred to as delibrate or induced hypo -tension, is while in (ASA) pretreatred groups the  difference was significant.