Impact of ophthalmic draping on end-tidal CO₂, cerebral oximetry, and optic nerve sheath diameter in cataract surgery: an observational comparison by COVID-19 pneumonia history with randomized oxygen flow allocation

Ophthalmic draping during cataract surgery creates an isolated surgical field but may lead to carbon dioxide (CO₂) accumulation beneath the drape. Elevated CO₂ can cause hypercapnia, cerebral vasodilation, and increased intracranial pressure, potentially reflected by changes in cerebral oximetry and optic nerve sheath diameter (ONSD). Patients with a history of COVID-19 pneumonia may exhibit residual pulmonary dysfunction that influences these parameters during surgery. This study aimed to investigate the effects of ophthalmic draping on end-tidal CO₂, cerebral oximetry, and ONSD in patients undergoing cataract surgery and to determine whether these effects differ between patients with and without a history of COVID-19 pneumonia. This prospective comparative study included 80 ASA I–III patients aged > 18 years with and without a history of COVID-19 pneumonia who underwent unilateral phacoemulsification under local anesthesia. Participants were divided into two main groups: those with (Group A, n = 40) and without (Group B, n = 40) a history of COVID-19 pneumonia. Within each predefined COVID-19 history stratum, patients were randomly allocated by block randomization to receive either 2 L/min (A-2, B-2) or 4 L/min (A-4, B-4) oxygen insufflation beneath the surgical drape. End-tidal CO₂ and hemodynamic parameters were continuously monitored, while cerebral oximetry parameters (rSO₂, ΔO₂Hb, ΔHHb, ΔcHb) were measured bilaterally every five minutes. ONSD was assessed ultrasonographically before and after surgery. ETCO₂ values showed no significant group-by-time differences. Postoperative ONSD values were significantly higher than preoperative values within both main groups and all oxygen-flow subgroups; however, the between-group comparisons were not statistically significant. Right frontal relative deoxyhemoglobin changes (ΔHHb-right) differed significantly between Groups A and B at the 10th minute ( p = 0.003), while the other cerebral oximetry parameters demonstrated no significant group- or time-dependent differences. No patient developed hypoxia or neurological deterioration. In patients undergoing short-duration unilateral phacoemulsification under local anesthesia with supplemental oxygen at 2–4 L/min, ophthalmic draping was not associated with clinically meaningful differences in ETCO₂ or ONSD, regardless of the history of COVID-19 pneumonia. Although selected cerebral oximetry parameters showed statistically significant differences between groups, all measured respiratory, hemodynamic, and cerebral physiological variables remained within physiological limits throughout the procedure. These findings should be interpreted within the context of the specific clinical settings studied. ClinicalTrials.gov, NCT05571683. Retrospectively registered on 7 October 2022.