[Flunitrazepam-pretreatment for prevention of adverse cardiovascular effects following ketamine]

In 18 patients with documented ischaemic heart disease the cardiovascular effects of ketamine (1.5 mg/kg iv) were studied under three different conditions: 1. in awake premedicated patients (n = 6); 2. after the previous administration of flunitrazepam (0.015 mg/kg iv, n = 6) and 3. under conditions of neuroleptanalgesia and muscle relaxation (n = 6). Flunitrazepam prevented or at least attenuated the increases in heart rate (30%), mean arterial pressure (37%), mean pulmonary artery pressure (165%), left ventricular filling pressure (230%), total peripheral resistance (50%), pulmonary vascular resistance (100%) and in the rate-pressure product (66%) which were associated with the use of ketamine as the sole anaesthetic agent. In addition, the flunitrazepam-pretreatment abolished the fall in cardiac index and stroke index which occured in patients given ketamine alone. Flunitrazepam therefore appears to be a promising drug to prevent adverse cardiovascular reactions, when ketamine should be chosen for induction of anaesthesia. Neuroleptanalgesia and muscle relaxation also proved effective in controlling the sympathomimetic actions of ketamine. The response of the mean pulmonary artery pressure and of the ventricular filling pressures to ketamine in this group was even more damped than in the patients pretreated with flunitrazepam alone.