Lidocaine was first discovered from systematic investigations at the Institute of Chemistry at Stockholm. In the early 1940s, Nils Lofgren discovered lidocaine as a potent anesthetic, initially labelled LL30. It was first clinically tested in 1994, and stood up to appraisal as a reliable and highly efficient local anesthetic.
One systematic review found that, depending on the duration of the infusion of lidocaine, significantly different pain ratings resulted. Similarly, a review found low to moderate evidence for an effect of intravenous lidocaine on pain at rest as one of the major predefined outcomes. Interestingly, this was true for a large variation between the bolus doses (1 to 3mg/kg) and continuous infusion regimes (1.5 to 5 mg/kg/h). The variation of doses impacted pain; early and intermediate, postoperative ileus, time to first flatus, and time to first bowel movements/sounds. One study based all medications in the protocol on the dosing body weight \[ideal body weight (IBW) + 0.4 x (actual body weight-IBW). Besides an important improvement in overall quality of recovery, subjects had an improvement in the physical comfort, pain, and physical independence subcomponents of the quality of recovery score. Additionally, there was an opioid sparing effect observed in patients undergoing laparoscopic bariatric surgery, making it especially critical due to the limited respiratory reserve of the bariatric population.
Another study assigned subjects in the experimental group to an IV infusion of 2mg/kg per hour of lidocaine, maintained 15 to 30 minutes before skin closure. The study found similar positive effects, improving postoperative analgesia, reducing postoperative opioid requirements, and accelerating the return of the first flatus. Specifically, the investigation found results similar to previous investigations with longer infusion times across a variety of surgical procedures.
Based on the above, there is a call for further research evaluating the optimum dosage of lidocaine infusion in bariatric populations undergoing major surgery. Not only are there a wide variety of positive effects of lidocaine that need to be investigated, but there is a need for precision and sensitivity of dose regimes in a bariatric population susceptible to adverse effects. It is therefore of interest to find an optimal dosage schedule in order to provide anesthesiologists with a standard which maximizes opioid sparing effects, whilst minimizing patient pain, hospital stay, as well as nausea and vomiting.
Given the complexity of this proposed randomized-controlled trial, as well as time and financial limitations, a pilot study was deemed necessary to find out the feasibility and safety of comparing different dosing schedules, rate of patient recruitment, funding necessities, and needs of additional personnel.
