Comparative Study Between Bilateral and Unilateral Spinal Anaesthesia

The purpose of this study is to compare unilateral spinal anesthesia using hyperbaric Prilocaine with "classical bilateral spinal anesthesia" using plain Prilocaine according to block characteristics and quality of micturition, standardized to the subjects own functional bladder capacity. Our hypothesis is that unilateral spinal anesthesia will provide faster time to micturtition and discharge, lesser hypotension and lesser micturition problems.

Many studies have been published in search of the ideal locoregional anesthetic for day case procedures under spinal anesthesia.

Transient neurological symptoms (TNS) and bladder retention are two side effects, which have been described in literature with incidences ranging from 0-80%.

Lidocaine, which was our hospital standard for spinal anesthesia in day case surgery, has a high incidence of TNS. Besides changing the product, dose or additive, optimisation of spinal anesthesia can be performed by changing anesthetic technique or fluid policy.

There is no consensus in literature about fluid policy and the risk of urinary retention. In a previous study we found that urge sensation and bladder capacity is subject to a high variability.

There are a few studies published about unilateral anesthesia for day-case surgery. For bilateral anesthesia it was shown that recuperation of the detrusor function comes with the regression of the sensory block to the S2 dermatome . However, little is known about bladder function during unilateral block of the sacral segments, not to mention the detrusor function and micturition with an asymmetric recovery of the sensory and motor block.

Prilocaine has found to induce reasonably short durations of spinal blockade, without causing TNS while manufactured in plain and hyperbaric solutions .

We expect that with a unilateral technique patients can void faster and can reach discharge criteria faster then with a bilateral technique.

We will compare unilateral spinal anesthesia with hyperbaric prilocaine with bilateral spinal anesthesia with plain prilocaine. The two techniques will be compared on the following subject

* quality of the motor and sensory block
* recovery from the sensory and motor block
* hemoynamic changens (blood pressure and hart rate)
* time to micturition
* micturition quality
* discharge time
* complications

Sensory block will be tested by loss of cold sensation. Quality of unilateral block will be tested by QST.

Protocol for catheterisation will be adjusted according to the patients individual bladder capacitity, based on a bladder diary. Quality of micturition will be based on bladderscanning, uroflow and subjective complaints. A micturition score from one of our previous studies is used.

Two days and one week postoperative patients will be called and asked if they experienced one of the following symptoms:

* Back pain
* Symptoms of TNS
* Headache
* Micturition problems
* Use of per oral pain medication
* Other

Eligibility Criteria:
Inclusion Criteria:

* spinal anaesthesia
* surgery\<60 minutes

Exclusion Criteria:

* preexisting micturition problems
* surgery lower abdomen/pelvis
* bmi\>30
* mental problems
* kidney disease
* neurologic disease