The purpose of this study is to compare the efficacity and the readiness for discharge between two local anesthetics, bupivacaine and 2-chloroprocaine, used for spinal anesthesia.

Many surgeries are performed under spinal anesthesia, including ambulatory surgeries. The standard agent used for spinal anesthesia is called bupivacaine. It's safe and effective, but has a major disadvantage. It has a long duration of action (up to 4 hours), witch can prolong unnecessarily the patient's stay in the recovery room and in hospital.

Another local anesthetic available for spinal anesthesia is 2-chloroprocaine. It has been used since many years, but some serious cases of toxicity in the 80's led to an interruption of its utilization. Those cases have been proven to be associated with the preservative agent (bisulfite) that was added and to the low pH (<3) of the drug.

Since then, 2-chloroprocaine exists in a preservative-free formulation and has been used in thousands of patients worldwide, without any problem. The major advantage of 2-chloroprocaine is its shorter duration of action, permitting a faster recovery from anesthesia, and also permitting a faster discharge from hospital (in a context of ambulatory surgery)

The purpose of this study is to compare the efficacity and the readiness for discharge (from the recovery room, and from hospital) between two local anesthetics, bupivacaine and 2-chloroprocaine, used for spinal anesthesia in elective ambulatory surgeries.

Patients, after consenting for the study, will be randomly assigned to the following groups:

• spinal anesthesia with chloroprocaine 2% 40 mg (2 mL)
• spinal anesthesia with bupivacaine 0,75% 7,5 mg (1 mL)

An "executant anesthesiologist" will be responsible for performing the spinal anesthesia, with a 25 gauge Sprotte needle, at the level L2L3, L3L4 or L4L5. The "responsible anesthesiologist" will only take charge of the patient after the technique, so he stays double-blinded to the local anesthetic used. During surgery, if the patient feels pain, he may receive iv fentanyl, 25-100 µg at every 5 minutes.

Measures will start immediately after the spinal block:

Evaluation of the sensory block height (with ice):

• Every 3 minutes for 15 minutes (time to obtain a block a about T10)
• Every 5 minutes for 45 minutes (surgery)
• Every 10 minutes for 60 minutes, then every 15 minutes until the block regresses to S2 (recovery room and ambulatory surgery unit)

Evaluation of the motor block (using the Bromage scale):

• Every 3 minutes for 15 minutes
• At the beginning and at the end of the surgery
• After the surgery:every 10 minutes for 60 minutes, then every 15 minutes until the block regresses to S2 (recovery room and ambulatory surgery unit)

(Bromage scale: full flexion of feet and knee = 0; able to move knee and feet, not hip = 1; able to move feet only = 2; unable to move feet or knee = 3)

When the block will have regressed to S2, the patient will be asked to urinate. If he isn't able to urinate, this demand will be repeated every 15 minutes. (not applicable if the patient goes home with a urinary catheter)

In the context of an ambulatory surgery, the patient will go home when he will meet the usual discharge criteria. All patients will receive a phone call from the research team the day after surgery, and 7 days later, to assess their satisfaction towards the analgesia and to inquire about potential complications of the spinal anesthesia.

Inclusion Criteria:

• patients aged 18 years and older
• urologic elective ambulatory procedure. For example:cystoscopy, circumcision,transurethral bladder tumor resection, varicocele and hydrocele surgery
• gynecologic elective ambulatory procedure. For example: hysteroscopy, vulvar ou vaginal biopsy
• general surgery elective ambulatory procedure. For example:inguinal herniorraphy, short ano-rectal procedure

Exclusion Criteria:

• INR > 1,3
• platelet < 75 000
• concomitant drugs: clopidogrel (last dose < 7 days), iv heparin, low molecular weight heparin (last dose < 24 hours)
• neurologic disease: spinal stenosis, symptomatic lumbar herniated disc, multiple sclerosis
• liquid restriction (cardiac or renal insufficiency)
• allergy or intolerance to chloroprocaine, bupivacaine or PABA
• atypical plasma cholinesterase or deficiency