Prophylactic Alpha-blockers in the Prevention of Urinary Retention Post Inguinal Hernia Repair

Overview

Post operative urinary retention ( POUR) is caused by sympathetic activation of the internal urethral sphincter after surgery. The smooth muscles of the around the internal urethral sphincter have been demonstrated to be rich in alpha-1 adrenergic receptors. Our research idea is novel because there has been no prior prospective study conducted using alpha-blockers to reduce post-operative urinary retention in patients undergoing inguinal hernia repair. The proposed research is important as existing studies that sought to understand POUR have merely established the risks factors involved. Despite so, the incidence of POUR remains high and no studies to date have investigated the use of specific interventions to reduce the risk of POUR. This is essential as patients who develop POUR have also been successfully shown to have significantly longer length of hospitalisation. Besides, the development of POUR can also cause significant pain/discomfort, increase risks of long-term urethral catheterisation and predispose patients to urinary tract infections

The study will be conducted as a randomised, double blind, placebo-controlled trial. This is a single center trial. The experimental design and procedure will be performed in accordance to the CONSORT guidelines. Patients will be assessed for eligibility, and selected based on the inclusion and exclusion criteria. Once eligible, informed consent will be obtained for every patient, and those in agreement to the participation of the trial will be randomly provided with pre-assigned sealed envelopes containing either tamsulosin or placebo, for which patient and investigators will be blinded to. Patients will then consume either oral tamsulosin 0.4mg or placebo daily for 5 days prior to elective surgery. A baseline postural blood pressure measurement will be taken before and after the 1st dose, and patients will be informed to look out for symptoms of hypersensitivity reactions and orthostatic hypotension, and to cease consumption should they develop. Prior to surgery, the patients will require to report to the study team if they had finished all 5 drug doses. Patients who develop intercurrent illnesses or have urgent matters at hand that would require their surgery to be postponed will receive another 5 drug doses that is to be consumed prior the their next scheduled surgical date. During the surgery, a maximum dose of 0.1mg/kg of morphine can be given to patients. No ilioinguinal block will be performed for patients, but local anesthesia 10mls 0.5% Bupivacaine will be infiltrated into the wound sites. The patients will then be monitored in the 23 hour short stay ward, during which the patient's wound site, scrotum, pain levels and ability to pass urine will be assessed prior to being discharged. All patients will be provided with a maintenance drip post operatively. Patients will also be placed on paracetamol 1g 6 hourly strictly and tramadol 50mg 8 hourly as per required. Alternative analgesia will be provided should patients have existing allergies to these drug classes. Patients will be assessed for presence of voiding difficulty 6 hours post operatively, and patients who complain of voiding difficulty or inability to pass urine within 6 hours post operatively will be defined to have POUR, while a bladder scan will be performed will be performed . Patients with existing bladder volume of more than 400mls will be catheterised, while those with less than 400mls will be followed up with subsequent 2 hourly bladder scans, and catheterised should their bladder volume be beyond 400mls. Once discharged, patients will receive a phone call at 24 hours post discharge and scheduled to return for a follow up appointment 1 weeks later in the clinic where urinary symptoms will once again be assessed in both settings. The end points of incidence of POUR/catheterisation, length and cost of hospitalisation, rates of same day discharge, and patient satisfaction in both arms will be recorded and analysed. Patients will be analysed via an intention to treat basis, and patients who defaulted treatment (did not receive full 5 doses of medicine), did not turn up for surgery or lost to subsequent follow up post operatively will be taken into account, and reported and analysed accordingly.