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Effects of Permissive Hypercapnia During Lung Surgery on Inflammatory Biomarkers in Serum and Bronchoalveolar Lavage
Milena Stojanović1, Milena Vasilijic1, Jelena Zivadinovic1,2
1Clinic for Anaesthesia and Intensive Therapy, University Clinical Center Niš, 18000 Niš, Serbia.
Introduction:
Permissive hypercapnia has become an integral component of lung-protective ventilation strategies during one-lung ventilation (OLV), particularly in thoracic surgery. Its potential immunomodulatory effects have attracted increasing interest; however, clinical evidence remains limited and inconsistent.
The Aim:
The primary objective was to evaluate the effects of permissive hypercapnia on inflammatory biomarkers in bronchoalveolar lavage fluid and serum during one-lung ventilation. The secondary objective was to assess the influence of different ventilation modes on these inflammatory responses.
Methods:
Forty patients undergoing elective lung surgery requiring OLV were prospectively enrolled and allocated to either a normocapnic (n = 20) or hypercapnic group (n = 20). BAL concentrations of TNF-α, IL-1β, IL-6, and IL-8 were measured before and after intervention. Serum IL-6, C-reactive protein (CRP), and leukocyte counts were also assessed.
Outcome Measures:
Primary outcome: Change in bronchoalveolar lavage (BAL) levels of preselected biomarkers for inflammation (TNF-α, IL-1β, IL-6, and IL-8) and in serum (IL-6, CRP, and WBC) between the normocapnic and hypercapnic groups during one-lung ventilation.
Secondary Outcome:
Whether the inflammatory response differed according to the ventilation mode (pressure-controlled versus volume-controlled ventilation).
Results:
Baseline and post-intervention BAL concentrations of TNF-α, IL-1β, IL-6, and IL-8 were generally comparable between the hypercapnic and normocapnic groups. No significant differences were observed in post-intervention BAL concentrations of TNF-α, IL-1β, or IL-6 among the ventilated subgroups. However, post hoc analysis demonstrated significantly lower IL-8 concentrations in the hypercapnic-PC subgroup compared with the normocapnic-PC subgroup (p = 0.034). Within the normocapnic cohort, BAL IL-8 concentrations were significantly higher in the PC subgroup than in the VC subgroup (p = 0.012). In serum, postoperative IL-6 concentrations were significantly higher in the hypercapnic than in the normocapnic group (p = 0.003).
Conclusions:
Permissive hypercapnia was not associated with a reduction in BAL concentration of the pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-8. However, postoperative serum IL-6 concentrations were significantly higher in patients exposed to hypercapnia. As the duration of surgery, one-lung ventilation, and mechanical ventilation was longer in the hypercapnic group, the observed increase in serum IL-6 cannot be attributed solely to hypercapnia. Further large-scale randomized studies are required to clarify the immunological effects of permissive hypercapnia during thoracic surgery.
