Protective Ventilation Improves Gas Exchange, Reduces Incidence of Atelectases, and Affects Metabolic Response in Major Pancreatoduodenal Surgery

Abstract

Background: Protective perioperative ventilation has been shown to improve outcomes and reduce the incidence of postoperative pulmonary complications. The goal of this study was to assess the effects of ventilation with low tidal volume (V_T) either alone or in a combination with moderate permissive hypercapnia in major pancreatoduodenal interventions.

Materials and methods: Sixty adult patients scheduled for elective pancreatoduodenal surgery with duration >2 h were enrolled into a prospective single-center study. All patients were randomized to three groups receiving high V_T [10 mL/kg of predicted body weight (PBW), the HVT group, n = 20], low V_T (6 mL/kg PBW, the LVT group, n = 20), and low V_T combined with a moderate hypercapnia and hypercapnic acidosis (6 mL/kg PBW, PaCO₂ 45-60 mm Hg, the LVT + HC group, n = 20). Cardiopulmonary parameters and the incidence of complications were registered during surgery and postoperatively.

Results and discussion: The values of V_T were 610 (563-712), 370 (321-400), and 340 (312-430) mL/kg for the HVT, the LVT, and the LVT + HC groups, respectively (p < 0.001). Compared to the HVT group, PaO₂/FiO₂ ratio was increased in the LVT group by 15%: 333 (301-381) vs. 382 (349-423) mm Hg at 24 h postoperatively (p < 0.05). The HVT group had significantly higher incidence of atelectases (n = 6), despite lower incidence of smoking compared with the LVT (n = 1) group (p = 0.017) and demonstrated longer length of hospital stay. The patients of the LVT + HC group had lower arterial lactate and bicarbonate excess values by the end of surgery.

Conclusion: In major pancreatoduodenal interventions, preventively protective V_T improves postoperative oxygenation, reduces the incidence of atelectases, and shortens length of hospital stay. The combination of low V_T and permissive hypercapnia results in hypercapnic acidosis decreasing the lactate concentration but adding no additional benefits and warrants further investigations.

Keywords: atelectasis; pancreatoduodenal surgery; permissive hypercapnia; postoperative pulmonary complications; protective ventilation.

Figure 1

The values of tidal volume and arterial partial pressure of CO₂ in the groups at the beginning and end of the surgery. Data are presented as median (25th–75th percentiles). p values are calculated using Kruskal–Wallis H-test followed by post hoc Mann–Whitney U-test. *p < 0.001 between the LVT, LVT + HC, and the HVT groups for the tidal volume set at the start and end of surgery. ^†p < 0.001 between the LVT group and the LVT + HC group for PaCO₂ at the start and end of surgery.

Figure 2

The ratio of PaO₂/FiO₂ at 24 h after surgery. Data are presented as median (25th–75th percentiles). p values are calculated using Mann–Whitney U-test between the HVT and the LVT groups; *p = 0.027 compared with the HVT group.

Figure 3

The length of the hospital stay. Data are presented as median (25th–75th percentiles). p values are calculated using Kruskal–Wallis H-test followed by post hoc Mann–Whitney U-test between the HVT and the LVT groups only; *p = 0.048 using Mann–Whitney U-test test between the HVT and LVT groups analyzed pair-wise.

Figure 4

The incidence of the postoperative complications in the study groups. Data are presented as stacked numbers of the complications. p values are calculated using χ²-test between the HVT and the LVT groups; *p = 0.047 comparing all groups using Pearson χ²-test and p = 0.038 using Exact Fisher’s test between the HVT and LVT groups. ^†p = 0.13 for incidence of all the complications between the HVT and the LVT groups.