1 Department of Anaesthesia, North Devon District Hospital, Barnstaple EX31 4JB, UK. 2 Department of Anaesthesia and Intensive Care and 3 Department of Obstetrics and Gynaecology, Torbay Hospital, Torquay TQ2 7AA, UK. 4 Pharmacy Department, Derriford Hospital, Plymouth PL6 8DH, UK guy.rousseau@virgin.net
Accepted for publication: June 17, 2002
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Abstract |
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Methods. Ten ASA III patients (age 3850 yr) underwent uterine balloon thermal ablation under general anaesthesia. They each had 11 ml of 2% lidocaine gel (InstillagelTM) inserted into the uterine cavity at the end of the procedure. Blood samples were taken at 5, 15, 30 and 60 min after insertion and lidocaine concentrations were measured using high-performance liquid chromatography.
Results. Mean (range) plasma lidocaine concentrations at 5, 15, 30 and 60 min were 40.3 (0221.9), 66.3 (0271.9), 64.9 (0208) and 75 (0212) ng ml1, respectively.
Conclusion. There was minimal systemic absorption of lidocaine from the uterus following uterine balloon thermal ablation. Measured concentrations were well below the toxic plasma concentration for lidocaine (810 µg ml1).
Br J Anaesth 2002; 89: 8468
Keywords: anaesthetics local, lidocaine; uterus, thermal ablation
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Introduction |
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Methods |
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In the postoperative recovery area, patients received additional fentanyl 50 µg i.v. until comfortable. TylexTM (acetaminophen 500 mg and codeine phosphate 30 mg), two tablets every 6 h, and diclofenac 50 mg orally every 8 h were given as required for further analgesia.
After induction of anaesthesia, a 14-gauge i.v. cannula was placed in the antecubital fossa for postoperative blood sampling. The cervix was dilated with a size-5 Hagar dilator and the depth of the uterine cavity measured with a uterine sound. The balloon-tipped catheter was inserted into the uterine cavity up to this depth. The balloon was inflated with 5% dextrose 515 ml until a pressure of 160180 mm Hg was reached. The dextrose solution was then heated to 87°C for 8 min. To maintain contact with the endometrium, the pressure in the balloon was kept at 160180 mm Hg. At the end of the procedure, 2% lidocaine 11 ml was inserted into the uterus using an introducer (Instillaquil). Blood samples were taken at 5, 15, 30 and 60 min after insertion of the lidocaine gel. The plasma was separated using 4-ml Vacuette tubes (Greiner Turbotechnik) within 3 h and stored at 20°C. Plasma lidocaine concentration was measured using high-performance liquid chromatography and the values expressed in ng ml1 plasma.4 The extraction method was shown to be accurate and precise over the concentration range investigated: the intraday precision coefficients of variation and relative error were, respectively, 6.70% and 2.90% at 50 ng ml1, 5.14% and 3.50% at 100 ng ml1 and 3.88% and 9.03% at 200 ng ml1. Interday precision coefficients of variation and relative error were, respectively, 6.47% and 0.12% at 50 ng ml1, 3.84% and 2.14% at 100 ng ml1 and 2.80% and 2.19% at 200 ng ml1.
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Results |
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Discussion |
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We chose to use lidocaine in a gel because it is available in this form. In addition, it is supplied in a syringe that is incompatible with i.v. needles and cannulae, which reduces the risk of inadvertent i.v. injection. The dose of lidocaine was not adjusted for weight or body mass index (BMI) because we wanted to evaluate a simple one-dose regimen for adults. Other factors may affect how much lidocaine is absorbed, such as uterine cavity size and uterine muscle spasm, both of which will alter the volume of lidocaine that remains in the uterine cavity. Peak plasma concentrations in those with a lower body weight or BMI were below toxic concentrations.
In conclusion, the amount of lidocaine absorbed systemically after 11 ml of 2% lidocaine gel is placed in the uterine cavity following intrauterine balloon thermal ablation is low. Further studies are needed to evaluate the analgesic effects of intrauterine lidocaine gel after balloon thermal ablation.
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Acknowledgements |
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References |
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2 Amso NN, Stabinsky SA, McFaul P, et al. Uterine thermal balloon therapy for the treatment of menorrhagia: the first 300 patients from a multi-centre trial. Br J Obstet Gynaecol 1998; 105: 51723[ISI][Medline]
3 Anderson LF, Meinert L, Rygaard C, et al. Thermal balloon endometrial ablation: safety aspects evaluated by serosal temperature, light microscopy and electron microscopy. Eur J Obstet Gynecol Reprod Biol 1998; 79: 638[ISI][Medline]
4 Zivanovic L, Agatonovic-Kustrin S, Vasiljevic M, Nemcova I. Comparison of high-performance and thin-layer chomatographic methods for the assay of lidocaine. J Pharm Biomed Anal 1996; 14: 122932[ISI][Medline]
5 Foldes FF, Malloy R, McNall PG, Koukal LR. Comparison of toxicity of intravenously given local anaesthetic agents in man. JAMA 1960; 172: 14938[ISI]