Serial arterial blood gas monitoring during deep sedation for left atrial ablation procedures: a retrospective cohort study

Abstract Background The use of deep sedation in left atrial procedures, like pulmonary vein isolation (PVI) for atrial fibrillation, is increasing, particularly with pulsed field ablation (PFA), which often requires deeper sedation than traditional methods. Currently, there is no standardized European consensus on sedation protocols for these procedures, with practices varying from minimal sedation to deep sedation (RASS score -4). No studies have yet assessed respiratory and metabolic stability through serial arterial blood gas (ABG) analysis over time in these patients. Purpose This study aimed to evaluate the utility of serial ABG monitoring (every 15 minutes) for assessing hemodynamic and respiratory stability in deeply sedated patients, guiding interventions like sedation adjustments, manual ventilation, and non-invasive ventilation (NIV). Methods We retrospectively studied 63 patients (mean age 64.8 years, 38.1% female) undergoing left atrial ablation with radiofrequency (RF) or PFA at a single center. Continuous invasive blood pressure was monitored via radial artery access, and sedation with midazolam, fentanyl, and propofol was used to achieve a RASS score of -4. ABGs were collected every 15 minutes, analyzing pH, pO2, pCO2, and base excess (BE). Clinical actions, including sedation adjustments and ventilation support, were based on ABG results. Acidosis was defined as pH < 7.35, severe acidosis as pH < 7.20, and hypercapnia as pCO2 > 45 mmHg, with significant hypercapnia at pCO2 > 60 mmHg. Results Among the patients, 63 had at least two ABGs taken within the first 30 minutes, 60 had three, and 47 had four (up to 60 minutes). Significant pH changes were observed over time (repeated measures ANOVA, p < 0.001), with marked decreases between early and later measurements (e.g., 15 to 30 minutes, p < 0.001). pCO2 levels rose significantly after 30 minutes (p<0.001) , stabilizing due to clinical interventions like sedation adjustments. Severe hypercapnia (pCO2 > 60 mmHg) occurred in 13 patients (21%), with manual ventilation required in 17 patients (27%) and NIV in 3 patients (4.8%). BE showed significant shifts, with changes at various time points (e.g., 15 to 30 minutes, p < 0.001). Sodium bicarbonate (NaBic) was given to 14 patients (22.2%). Conclusion This study highlights the value of serial ABG analysis in identifying critical changes in pH, pCO2, and BE in deeply sedated patients during left atrial ablation, which may otherwise go undetected with standard monitoring practices. Notably, more than 20% of patients experienced severe hypercapnia within an hour, requiring clinical interventions. These findings support the potential need for ABG monitoring as a new standard in deep sedation for left atrial procedures, offering insights into respiratory and metabolic stability that are not achievable through routine SpO2 and blood pressure monitoring alone.ABG pH values over time pCO2 values over time