Impact of Preoperative Toxicological Screening on Perioperative Anesthetic Management and Short-Term Outcomes Following Metabolic and Bariatric Surgery: A Prospective Observational Study

Preoperative substance use is increasingly observed among candidates for metabolic and bariatric surgery (MBS), yet its perioperative and 1-year effects remain unclear in the Middle East and North Africa (MENA). We assessed whether routine preoperative urine toxicology screening tests (TSTs) predict anesthetic requirements, recovery, early complications, and 1-year weight loss. Prospective single-center cohort of 1,260 primary MBS patients (Alexandria, Egypt; Dec 2023–May 2024). All underwent urine screening for seven substance classes and were classified as TST-positive or TST-negative. Outcomes included propofol and intraoperative fentanyl doses, recovery metrics, postoperative pain (VAS) and opioid requirements, 30-day complications/readmissions, length of stay, and 1-year percent total and excess weight loss (%TWL, %EWL). Inverse propensity score weighting (IPSW) balanced baseline covariates. One-year outcomes were available for 1,134 of 1,260 patients (90.0%). 190 out of 1,260 (15.1%) were TST-positive—most commonly tramadol (57.9%) and cannabis (36.8%); 12.1% denied use despite a positive TST. After IPSW adjustment, TST-positive patients required more propofol (mean difference 49.7 mg; p < 0.001) and fentanyl (MD 51.2 µg; p < 0.001), experienced longer recovery times (MD 5.36 min; p < 0.001), had higher postoperative VAS scores and opioid requirements, longer hospital stays (p < 0.001), and increased 30-day complications (5.4% vs. 1.9%; p = 0.015) and readmissions (7.1% vs. 1.6%; p < 0.001). Routine preoperative TST identifies patients at risk for increased anesthetic/analgesic needs, delayed recovery, agitation, and higher early morbidity. Incorporating TST into preoperative pathways may optimize perioperative planning in MENA settings. NCT07100314. TST-positive patients required higher anesthetic doses and longer, agitated recovery. TST-positive patients reported higher pain scores and greater 24-h opioid consumption. TST-positive patients had more 30-day chest infections and readmissions for vomiting. Undisclosed TST-positivity (12.1%) supports objective screening in the MENA region.