Effect of tidal volume on tolerance to hemorrhage and resuscitation requirements: an experimental study in ventilated piglets

Introduction: Hemorrhagic shock is a life-threatening condition requiring rapid management. Mechanical ventilation, frequently initiated early in emergency care, influences systemic hemodynamics, yet the impact of tidal volume during hypovolemia remains poorly defined. Objectives: The primary objective of this experimental study was to compare the median depletion volume (MDV) of blood required to induce hypotension (mean arterial pressure [MAP] = 40 mmHg) according to tidal volume in mechanically ventilated piglets. The secondary objective was to compare the median transfusion volume (MTV) required to achieve a MAP ≥ 60 mmHg. Methodology: Twenty-three anesthetized piglets were allocated to three ventilation strategies: low tidal volume (LV, 6 mL·kg⁻¹; n = 7), medium tidal volume (MV, 8 mL·kg⁻¹; n = 8), and high tidal volume (HV, 10 mL·kg⁻¹; n = 8). Hemorrhagic shock was induced by controlled blood withdrawal until a MAP of 40 mmHg was reached, followed by resuscitation using autologous whole blood transfusion. Results: The MDV did not differ between groups: 30 (25–39) mL·kg⁻¹ in the LV group, 37 (35–39) mL·kg⁻¹ in the MV group, and 40 (33–41) mL·kg⁻¹ in the HV group (p = 0.34). The MTV tended to be higher with increasing tidal volume: 10 (7–10), 10 (10–13), and 12 (10–14) mL·kg⁻¹ in the LV, MV, and HV groups, respectively (p = 0.09). Conclusion: Tidal volume did not influence tolerance to hemorrhage during active blood loss. Higher tidal volumes were associated with greater transfusion requirements during resuscitation, although differences did not reach statistical significance.