Critical Care and Shock

Correlation between cerebral near-infrared spectroscopy and macrohemodynamic changes post-fluid resuscitation in the Sus scrofa model of hemorrhagic shock

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Objectives: Current resuscitation approaches focus on macrohemodynamic circulation, whereas adequate tissue perfusion and target organ oxygen delivery should be the primary goals. This study aimed to compare the macrohemodynamic markers with microcirculation markers (cerebral oxygenation) in response to shock and fluid resuscitation.

Design: This is an experimental study using an intact in vivo model of hemorrhagic shock.

Setting: This study was conducted at a certified animal experimental laboratory.

Patients and participants: Male domestic piglets (Sus scrofa) 6-10 weeks old were used as the model for this study.

Interventions: Measurement of microcirculation in animal model of hemorrhagic shock.

Measurement and results: Under anesthesia, the pressure-targeted shock was induced via venous blood drawing to reduce mean arterial pressure (MAP) by 20%, followed by normovolemic resuscitation using NaCl 0.9% of equal volume to the blood drawn. After 30 minutes, hypervolemic resuscitation using 40 ml/kg NaCl 0.9% was given. Pulse contour cardiac output (PiCCO) was used to monitor cardiac index (CI), stroke volume index (SVI), systemic vascular resistance index (SVRI), and oxygen delivery (DO2), while near-infrared spectroscopy (NIRS) measured cerebral saturation (SctO2). All parameters were recorded at baseline, shock, immediately following normovolemic resuscitation, hypervolemic resuscitation (hypervolemic-1), and the next 30 minutes (hypervolemic-2), and 60 minutes (hypervolemic-3). There were strong correlations between delta SctO2, delta CI, delta SVI, and delta DO2 during the hemorrhagic shock and normovolemic phase (p<0.05). No macrohemodynamic parameters represent the cerebral oxygenation during hypervolemic-1 up to hypervolemic-3.

Conclusions: Macrohemodynamic parameters were not correlated to SctO2 as a surrogate for microcirculation in every phase. We recommend routinely monitoring microcirculation as a target goal of resuscitation in critically ill patients.