Intraluminal Ureteric Injection of High Concentration Alkalinised Long-acting Local Anaesthetic and STeroid Post urEteroscopy: A Prospective Double Blinded Randomised Controlled Trial (LASTE Trial)

Study Rationale Ureteroscopy is a widely performed procedure in urology. Pain is one of the commonest complications after ureteroscopy and one of the common reasons for re-admission after this procedure. Insertion of a stent post-ureteroscopy can cause pain affecting daily activities in 80% of the patients. Pain post ureteroscopy is multi-factorial and currently there is no specific method used clinically to treat this. Intraluminal injection of local anesthetic solution in the ureter has been extensively studied in the animal model with positive results. Intraluminal injection steroids has also been studied previously and steroids have also been used in medical expulsive therapy for ureteric stones previously. The investigators are proposing the use of high concentration alkalinized long-acting local anaesthetic levo-bupivicaine and long-acting steroid dexamethasone for post-ureteroscopy pain. It is simple, cheap, safe, easy to perform and widely available.

Background Intraluminal injection of local anesthetics (LA) in the ureter has been studied previously in animal models. Burdgya et al in 1986, USSR examined effects of LA on guinea pig ureters . Action potential of ureteric smooth muscle has initial fast component consisting of repeated gradually decaying spikes and a subsequent slow component i.e plateau. This action potential is accompanied by a brief contraction. Two opposite effects of LA occur on ureteric smooth muscle: Low concentrations of procaine, lignocaine and tetracaine (0.1-1 mM) at pH 7.4 increased duration of slow plateau of the evoked action potentials. At higher concentrations lignocaine (5mM) and tetracaine (0.5mM) caused complete inhibition of evoked action potentials and phasic contractions. Procaine 5mM predominantly inhibited contractile responses. High pH (9) significantly increased while low pH (pH 6) decreased the inhibitory action of procaine and lignocaine. Tetracaine had the most potent inhibitory action on ureter smooth muscle with the weakest stimulant action while lignocaine had stronger inhibitory effect on ureter smooth muscle than procaine. Ross et al in 1972 reported intraluminal injection of 2% lignocaine reduced peristaltic activity in 5 out of 15 ureters in their patients with no effect in the remaining group.

Andersson and Ulmsten found that local instillation of 4% lignocaine in their patients caused an initial brief stimulation followed by reduced activity. Tsuchida in 197 studied dog ureters to report prompt inhibitory effect of 4% lignocaine applied to mucosa invivo with no effect when applied to adventitia.

Struthers in 1976 in his invivo dog studies found both systemic and intraluminal administration of lignocaine, procaine and mepivacaine caused only hyperperistalsis and never inhibition. Sur et al published a study with intravesical injection of ropivacaine before ureteroscopic surgery demonstrated trends toward decreased pain and voiding symptoms. Patients received five injections of 2 mL 0.5% ropivacaine around the ureteral orifice or to the control cohort, who received five injections of 2 mL of 0.9% normal saline in identical locations. A pilot study suggested that PSD597 (intravesical alkalinized lidocaine) is effective for treating interstitial cystitis/painful bladder syndrome (IC/PBlS) , providing short-term amelioration of symptoms in a substantial proportion of patients, with a strong suggestion that repeating the treatment has a potentially cumulative effect. A randomized controlled trial comparing injection of non-irritating salt water (placebo), and half an injection of pH buffered lidocaine before the stent placement in patients undergoing ureteroscopy is currently being conducted. Till date there is no human study assessing the efficacy and safety of high concentration alkalinised long-acting LA injection for post-ureteroscopy pain based on the results of the animal studies outlined above.

The anaesthetic drug chosen for this study is levobupivacaine (Chirocaine™ -): it is S-isomer of bupivacaine, an amino-amide local anaesthetic widely used in regional anaesthesia, in postoperative analgesia and in treatment of acute and chronic pain. This drug produces sensory and motor nerve conduction block, acting on sodium channels of the cell membrane - sensitive to electric stimulus - but also on potassium and calcium channels. Moreover, it is remarkable for a rapid onset time and a long duration. In vitro and in vivo pharmacodynamic studies show that levobupivacaine has the same potency as bupivacaine, though the former is less likely to cause cardio- and neurotoxicity.