Plasma levels of local anaesthetics following their injection are affected by many factors. Serial plasma levels following injection of lignocaine and prilocaine at various rates in over 500 patients have been measured and this has allowed some of these factors to be assessed and quantified. The vascularity of the site of injection causes major differences in the maximum plasma level. Prilocaine consistently gives lower levels than lignocaine. Adrenaline causes a reduction in the plasma levels of both drugs and the optimal concentration is 1:200,000. Speed of injection is important when giving the drugs intravenously but not epidurally. The concentration of the injected solution does not affect the plasma levels. The weight and age of the patients (all adult females) were unrelated to the mayi'mnm plasma levels.

Estimations of the plasma concentrations of lignocaine and prilocaine during epidural block and intercostal regional block show that higher plasma levels are consistently found with lignocaine provided comparable solutions are studied; that the site of injection is of some importance in determining the absorption of local analgesic drug; that, within the range 1-2 per cent, concentration is not important if a total dose of 400 mg of either drug is not exceeded and finally that the addition of adrenaline 1/80,000 is of value with lignocaine but possibly not with prilocaine.

We have compared gastric aspirate pH and volume at induction of anaesthesia in 222 patients who had received either omeprazole or ranitidine before elective operations. Omeprazole was given orally either as 40 mg on the evening before and 40 mg on the morning of surgery or as 80 mg on the morning of surgery. Ranitidine 150 mg was given orally on the evening before surgery and 2 h before anaesthesia. Treatment success was defined as aspirate pH > or = 2.5 and volume < 25 ml at induction of anaesthesia. Treatment was successful in 84% (95% confidence interval (CI) 73-91%) of patients in the omeprazole 40 + 40 mg group, 84% (95% CI 73-91%) in the ranitidine group and 73% (95% CI 61-83%) in the omeprazole 80 mg group. There were no statistically significant differences between the groups. Twelve patients in the omeprazole 80 mg group had gastric pH < 2.5 and four had volume > 25 ml. Only three patients had a gastric pH < 2.5 in the omeprazole 40 + 40 mg group and none had volume > 25 ml, which compared well with the ranitidine group. Omeprazole, given as 40 mg in the evening and 40 mg on the morning of operation, has a potential role for use in patients at risk for aspiration during general anaesthesia.

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The plasma concentrations reached following the epidural injection of 200, 400, 500, 600 and 700 mg of lignocaine have been determined. From these results, a linear relationship between dosage and plasma concentration was established. Plasma concentrations following rapid injection (400 mg in 15 seconds) were determined and found to be slightly higher than slower (60 seconds) injection. Statistical analysis of data has allowed a preliminary evaluation of the effects of weight and age upon the plasma concentrations of lignocaine. Recommendations on the dosage of lignocaine in epidural block in regard to toxicity are made, and the effects of the various factors affecting the absorption and elimination of local anaesthetic agents are assessed.