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Lidocaine 0.5% spinal anaesthesia: a hypobaric solution for short-stay perirectal surgery


The efficacy of subarachnoid injection of 8 ml lidocaine 0.5% was assessed in ten outpatients having perirectal surgery in the jackknife position. This solution is hypobaric, with a baricity 0.9985 ± 0.0003 (mean ± SD). Injections were made with the patient in the surgical position (with the upper torso at a 15° downward inclination). Sensory level was tested by pinprick. Times to two-segment regression, to complete resolution of sensory analgesia, to urination, and to discharge from the recovery room were recorded. All injections produced effective anaesthesia for surgery. Lidocaine 0.5% behaves clinically as a hypobaric solution. Dermatomal levels remained low (T11 to L5) while the patients were in the surgical position (head down), but rose two to six dermatomes if the patient’s head was elevated after surgery. Time to two-segment regression was 97 ± 36 min, time until regression to 5y was 116 ± 22 min, time to complete resolution of sensory blockade was 151 ± 23 min, time to urination was 197 ± 64 min, and time to discharge from the recovery room was 205 ± 45 min. Lidocaine 0.5% provides effective spinal anaesthesia of short duration appropriate for outpatient surgical procedures. Dermatomal sensory spread of anaesthesia, and our measurements of specific gravity, indicate that this solution is hypobaric. It appears that changes in position can alter the spread of analgesia for at least one hour after injection and, thus, we caution against elevating the patient’s head in the immediate postoperative period.


On a étudié l’efficacité d’une injection sous-arachnoïdienne de 8 ml de lidocaïne 0,5% hypobare (baricité de 0,9985 ± 0,0003) chez dix patients admis pour une chirurgie péri-rectale en position de Depage («jacknife position»). L’injection de lidocaïne a été faite chez le patient en position chirurgicale et le niveau d’anesthésie fut mesuré par piquage. Toutes les injections ont entraîné une anesthésie efficace, le niveau n’excédant pas D11 (D11 à L5) tant que le patient est demeuré en position chirurgicale. Le redressement du patient à la fin de la chirurgie a entraîné une augmentation du niveau d’anesthésie de deux à six dermatomes. Le temps de régression de deux segments, le temps de régression à S1 et le temps de résolution complète du bloc sensitif ont été respectivement de 97 ± 36 min, 116 ± 22 min et 151 ± 23 min. Le temps de miction a été de 197 ± 64 min et le temps de départ de la salle de réveil de 205 ± 45 min. La lidocaïne 0,5% procure une anesthésie rachidienne efficace et de courte durée qui convient bien au patient opéré en externe. En raison du caractère hypobare de la solution, on ne devrait élever la tête du patient que plus d’une heure après l’injection.


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Correspondence to Randall L. Carpenter.

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Bodily, M.N., Carpenter, R.L. & Owens, B.D. Lidocaine 0.5% spinal anaesthesia: a hypobaric solution for short-stay perirectal surgery. Can J Anaesth 39, 770 (1992).

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Key words

  • anaesthetics, local: lidocaine
  • anaesthetic techniques: Spinal