The effect of spinal anaesthesia on urethral function

This study was to assess the effect of spinal anaesthesia on urethral retro-resistance pressure (URP), cough pressures and tendency to leak. The population consisted of 32 women undergoing a tension-free vaginal tape (TVT) operation under a spinal anaesthetic. URP, cough pressures and an assessment of the degree of leak were performed before the spinal anaesthetic was placed. A standard anaesthetic technique was used, and measurements were repeated after the spinal anaesthetic was inserted. The degree of leak was assessed on a five-point scale with 350 ml in the bladder. The cough pressures and URP values were averaged over three or more measurements. The mean URP value fell from 75.0 to 54.0 cm/H₂O (p = 0.0003) after the spinal was inserted. There was a non-significant fall in mean cough pressure from 85.0 to 67.5 cm/H₂O (p = 0.06). The degree of leakage increased (p = 0.005). Spinal anaesthesia causes a fall in the resistance in the urethra but does not cause a significant fall in the pressure generated by a cough. Women are more likely to leak after coughing during the TVT operation under spinal anaesthesia than they are before the spinal is inserted. The cough test under spinal anaesthesia does not mimic the result of coughing without a spinal.