The effect of intravenous fluid preload on diuresis during spinal anesthesia-induced detrusor blockade

Spinal anesthesia , through interruption of spinal nerve conduction, causes
intense blockade of sensation, motor function as well as (para)sympathetic
function. Loss of sympathetic tone causes vasodilation which may lead to
arterial hypotension and bradycardia. To avoid these effects, in anesthetic
practice, usually intravenouspreload is administered as cristalloids or
colloids. The form and dosage of these plasma expanders will influence diuresis
during spinal anesthesia-induced detrusor blockade. Excess diuresis may cause
bladder distension and neccecitates bladder catheterization

Objective: to compare the quantitative effects of Ringer Lactate and HES 6% on
diuresis during spinal anesthesia-induced detrusor blockade as well as
prevention of hypotension and vasopressor use.

Before spinal anesthesia is performed, patients are randomized into one of the
3 study groups (no preload, preload with Ringers' Lactate 14 ml/kg, preload
with HES 6% 7 ml/kg). Spinal anesthesia is administerd with lidocaine 2% 70mg.
Hypotension is treated with vasopressors, atropine or additional intravenous
fluid. Bladder scans will be performed on the recovery unit and day-case unit.
Total urinary volume is measured until sensory function at dermatome S2/3 is
restored and spontanous voiding is possible.

Prespinal administration of intravenous Ringers' Lactate 14 ml/kg or HES 6% 7
ml/kg.

Except for extra bladderscan and block height measurements, all actions are
part of routine anesthesiologic care.