SummaryIn a double-blind trial, 50patients were randomly allocated to receive up to 0.29

No abstract

Interest in the Gorlin formula for estimating heart valve effective orifice area (EOA) has recently been rekindled and the formula itself has been challenged. In this validation study, explanted native heart valves, unimplanted mechanical prostheses, unimplanted bioprostheses and explanted bioprostheses have been tested in vitro in a pulsatile flow simulator. Pressures have been measured 30 mm upstream and 100 mm downstream from the plane of the valve sewing ring (to give pressure drop, pd in kPa). Flow (Q in 1 min-1) has been measured directly by electromagnetic flowmeter and orifice areas have either been taken from manufacturer supplied data (mechanical valves) or have been digitised from video images at maximum orifice (biological valves). The formula EOA = Q/(6.96 x pd 1/2) - 0.7 fitted the data with good correlation, r = 0.96 (n = 179). The orifice assumption on which this formula is based (cf. Gorlin formula) is confirmed though it is recommended that the formula should be modified to account for (i) the pressure recovery phenomenon and (ii) the fact that forward flow through a valve only occurs over a portion of the cycle in pulsatile flow. Heart rates used in the study ranged from 40 to 140 min-1, stroke volumes ranged from 20 to 114.3 ml, cardiac outputs from 2.0 to 8.0 1 min-1 and peripheral resistance from 0.1 to 1.6 kPa 1-1 min (1 - 12 mmHg l-1 min). Application of the formula was independent of the flow conditions.

A randomized partial cross-over clinical trial of two intravenous techniques for outpatient conservative dentistry was performed in 61 patients. Subanaesthetic incremental doses of Althesin were used at 52 sessions and a single sedative dose of diazepam at 45 sessions. Each technique produced similar cardiovascular and respiratory changes. With Althesin, recovery after operation was more rapid and there was some evidence of a stronger anxiolytic effect and of less frequent and less severe thrombophlebitis. In contrast, Althesin was sometimes associated with jaw tremor or shivering and was less frequently mentioned by those patients who expressed a strong preference for one of the two techniques.

In a randomized cross-over trial in 82 outpatients aged 15-45 yr undergoing conservative dentistry, a solution of flunitrazepam 0.25 mg ml-1 i.v. (average dose 0.014 mg kg-1) was compared with a solution of diazepam 5 mg ml-1 i.v. (0.29 mg kg-1). Cardiovascular changes, operating conditions and side-effects were similar. Forty minutes after the start of injection, about 85% of all patients could not remember the local anaesthetic injection. Thirty minutes after the end of treatment, only 25% of all patients had recovered. One week later, most patients receiving each drug had only vague memories of their treatment; they had felt more relaxed immediately after the i.v. injection than before. Drowsiness was equally common after flunitrazepam and diazepam. Ataxia was more prolonged with flunitrazepam but arm pain and venous thrombophlebitis were less frequent.