Lidocaine Infusions for Pain in Patients With Malignant Bowel Obstruction

Background: Malignant bowel obstruction (MBO) occurs in 10 to 28% of patients with gastrointestinal cancers and in up to 51% of patients with advanced ovarian cancer. Pain is present in 70 to 90% of patients and is often multifactorial, with visceral, inflammatory and neuropathic components. International supportive care guidelines recommend opioids as the basis of analgesic treatment, together with adjuvants, antisecretory agents and antiemetics. However, a subgroup of patients develops refractory pain or dose-limiting opioid adverse effects. Lidocaine, a voltage-gated sodium channel blocker with additional activity at muscarinic and NMDA receptors, has been used as an adjuvant infusion for refractory cancer pain, but evidence specific to MBO is scarce.

Design: Single-center, observational, retrospective cohort study with descriptive and analytical components, conducted in the context of routine clinical practice. Data sources are the institutional electronic health records.

Population and identification: Adults (18 years or older) with cancer and MBO attended by the palliative care team between 2015 and 2025 who received a lidocaine infusion with analgesic intent. Patients will be identified through institutional databases, palliative care service records and medical orders for lidocaine infusions prescribed by a pain and palliative care specialist or fellow. All consecutive eligible patients will be included (non-probability, convenience sample). Eligibility will be verified in the electronic health record by the research team.

Data collection: Data will be recorded in an institutional REDCap database with a unique pseudonymized code for each participant. Variables include demographic, clinical and oncological characteristics (primary tumor, stage, peritoneal carcinomatosis, active cancer treatment, ECOG performance status), obstruction characteristics (level, grade, diagnostic method), pain type, baseline opioid use and oral morphine milligram equivalents (MME/24 h), concomitant adjuvant treatments (corticosteroids, somatostatin analogues, anticholinergics, ketamine, gabapentinoids), lidocaine regimen (route, initial and maximum dose in mg/kg/h, duration), pain intensity (0 to 10 Numeric Rating Scale, NRS) before and after infusion start, adverse events, reason for infusion discontinuation and hospital discharge destination.

Time windows: Baseline NRS and MME are those recorded within the 24 hours before infusion start; post-infusion values are those recorded at 24 and/or 48 hours after infusion start, using the value closest to each time point.

Outcomes: The primary outcome is the change in pain intensity (NRS) from baseline to 24 to 48 hours after infusion start. Secondary outcomes include the proportion of analgesic responders (reduction of 2 or more NRS points or 30% or more from baseline within 24 to 48 hours), change in MME/24 h, frequency and type of adverse events, discontinuation due to toxicity, lidocaine dosing and duration, and hospital discharge destination.

Statistical analysis: Categorical variables will be summarized as frequencies and proportions and continuous variables as means with standard deviations or medians with interquartile ranges according to their distribution. Paired pre-post comparisons of NRS and MME will use the paired t test or the Wilcoxon signed-rank test as appropriate. The proportion of responders will be reported with 95% confidence intervals. Exploratory subgroup analyses (lidocaine dose, infusion duration, route, baseline pain, ECOG and baseline MME) will use chi-square or Fisher exact tests and t, Mann-Whitney U or Kruskal-Wallis tests as appropriate. Missing data will be described; complete-case analysis will be used if missingness is below 10%, and multiple imputation will be considered otherwise. Given the absence of an external control group and the potential for confounding by indication, all findings will be interpreted as associations without causal inference.

Ethics: The study is classified as minimal risk under Colombian Resolution 8430 of 1993. The protocol (version 1.0, February 18, 2026), including a waiver of informed consent for retrospective record review, was approved by the Comité Corporativo de Ética en Investigación of Fundación Santa Fe de Bogotá (CCEI-19342-2026). Data will be handled in accordance with Colombian Law 1581 of 2012 on personal data protection.