Background: The evolution of antimicrobial resistance among critically ill patients before, during, and after the COVID-19 surge remains unclear. Methods: We retrospectively analyzed critically ill mechanically ventilated adult patients admitted to 8 Brazilian hospitals from Jan 1, 2018 to Apr 30, 2023. We stratified the patients into 3 periods: pre-surge (Jan 01, 2018-Mar 01, 2020), surge (Mar 01, 2020-Oct 01, 2021), and post-surge (after October 01, 2021). Positive cultures, pathogen prevalence, and resistance rates were analyzed using rate ratios (RR) with 95% confidence intervals (CI). Results: Among 9,780 patients (3,718 pre-surge, 3,815 surge, 2,247 post-surge), those in surge period were younger (median: 70 vs 74 pre-surge vs 75 post surge) and had longer invasive mechanical ventilation duration (median 7 vs 5 days). Blood and respiratory cultures increased across periods (56.9 pre-surge vs 69.4 surge vs 70.4 patients/1,000 patient-days post-surge). Isolation of carbapenem-resistant gram-negatives increased during the surge (RR [95% CI]: 1.8 [1.5-2.2], decreased in post-surge (0.72 [0.6-0.9]), and remained higher than pre-surge (1.3 [1.0-1.6]). Resistance rates for Pseudomonas aeruginosa reduced in post-surge, whereas Klebsiella pneumoniae doubled during the surge, and remained elevated. Conclusions: Carbapenem resistance increased during the surge period. Although it decreased post-surge, it remained higher than pre-pandemic rates.