Blood product resuscitation mitigates the effects of aeromedical evacuation after polytrauma

Porcine Packed Red Blood Cells Demonstrate a Distinct Red Blood Cell Storage Lesion

INTRODUCTION

The red blood cell (RBC) storage lesion has been well described in mouse and human blood but not in swine. Understanding the porcine RBC storage lesion is necessary prior to evaluating transfusion of stored packed red blood cells (pRBCs) in polytrauma models. We hypothesized that porcine pRBCs would undergo a similar storage lesion severity after 42 d.

METHODS

Whole blood was collected from female Yorkshire pigs and pRBCs were isolated in additive storage solution 3. Female human whole blood was obtained from our local blood bank and pRBCs prepared. Human and porcine pRBCs were stored for 42 d and sampled weekly and evaluated for markers of the RBC storage lesion including biochemical measurements, eryptotic RBCs, band-3 expression, erythrocyte-derived microvesicles, and free hemoglobin concentrations.

RESULTS

Porcine pRBCs demonstrated a hematocrit similar to human pRBCs. Both human and porcine pRBC units developed a progressive storage lesion. However, over 42 d of storage, porcine pRBCs maintained their pH and had decreased glucose utilization. Porcine pRBCs also demonstrated decreased levels of eryptosis compared to human samples and generated less erythrocyte-derived microvesicles with lower free hemoglobin concentrations.

CONCLUSIONS

Porcine pRBCs stored in additive storage solution 3 demonstrate a progressive RBC storage lesion over 42 d of storage but with less severity than human controls. Given the differences in porcine erythrocyte metabolism, further study of the storage lesion in porcine blood is needed in addition to incorporating the use of stored porcine pRBCs in a swine model of hemorrhagic shock to more closely mimic clinical scenarios.

Validation of Preload Assessment Technologies at Altitude in a Porcine Model of Hemorrhage

INTRODUCTION

Dynamic preload assessment measures including pulse pressure variation (PPV), stroke volume variation (SVV), pleth variability index (PVI), and hypotension prediction index (HPI) have been utilized clinically to guide fluid management decisions in critically ill patients. These values aid in the balance of correcting hypotension while avoiding over-resuscitation leading to respiratory failure and increased mortality. However, these measures have not been previously validated at altitude or in those with temporary abdominal closure (TAC).

METHODS

Forty-eight female swine (39 ± 2 kg) were separated into eight groups (n = 6) including all combinations of flight versus ground, hemorrhage versus no hemorrhage, and TAC versus no TAC. Flight animals underwent simulated aeromedical evacuation via an altitude chamber at 8000 ft. Hemorrhagic shock was induced via stepwise hemorrhage removing 10% blood volume in 15-min increments to a total blood loss of 40% or a mean arterial pressure of 35 mmHg. Animals were then stepwise transfused with citrated shed blood with 10% volume every 15 min back to full blood volume. PPV, SVV, PVI, and HPI were monitored every 15 min throughout the simulated aeromedical evacuation or ground control. Blood samples were collected and analyzed for serum levels of serum IL-1β, IL-6, IL-8, and TNF-α.

RESULTS

Hemorrhage groups demonstrated significant increases in PPV, SVV, PVI, and HPI at each step compared to nonhemorrhage groups. Flight increased PPV (P = 0.004) and SVV (P = 0.003) in hemorrhaged animals. TAC at ground level increased PPV (P < 0.0001), SVV (P = 0.0003), and PVI (P < 0.0001). When TAC was present during flight, PPV (P = 0.004), SVV (P = 0.003), and PVI (P < 0.0001) values were decreased suggesting a dependent effect between altitude and TAC. There were no significant differences in serum IL-1β, IL-6, IL-8, or TNF-α concentration between injury groups.

CONCLUSIONS

Based on our study, PPV and SVV are increased during flight and in the presence of TAC. Pleth variability index is slightly increased with TAC at ground level. Hypotension prediction index demonstrated no significant changes regardless of altitude or TAC status, however this measure was less reliable once the resuscitation phase was initiated. Pleth variability index may be the most useful predictor of preload during aeromedical evacuation as it is a noninvasive modality.

Partial Resuscitative Endovascular Balloon Occlusion of the Aorta Limits Ischemia-Reperfusion Injury After Simulated Aeromedical Evacuation

INTRODUCTION

One of the advantages of partial Resuscitative Endovascular Balloon Occlusion of the Aorta (pREBOA) compared to the original model is the mitigation of reperfusion injury. The safety and efficacy of pREBOA have not been demonstrated in the setting of aeromedical evacuation. We hypothesized that the pREBOA would result in less ischemia-reperfusion injury after altitude exposure.

METHODS

Twenty-four swine underwent femur fracture with hemorrhage for 20 min, followed by resuscitative endovascular balloon occlusion of the aorta (REBOA) deployment to Zone 1 and were randomized to pREBOA-PRO (Prytime Medical Devices Inc) full inflation, partial inflation, or sham inflation and then an altitude exposure of ground level or 8000 ft for 15 min. The primary endpoint was to examine if the balloon functioned at altitude. Our secondary endpoint was investigating evidence of ischemia-reperfusion by hemodynamic instability, electrolyte derangements, and acidosis. Comparisons were made by ANOVA.

RESULTS

After deflation, the partially inflated group maintained a higher mean arterial pressure (MAP) compared to fully inflated group (P = 0.026). Full REBOA pigs were more tachycardic compared to sham pREBOA at ground (P < 0.001) and this was exacerbated at altitude (P < 0.001). Full REBOA pigs were more acidotic than sham and pREBOA at ground pigs (P = 0.0006 and P = 0.0002, respectively). Altitude increased the acidosis in full REBOA pigs, resulting in a greater base deficit (P < 0.0001), lactate (P < 0.0001), and IL-6 (P = 0.006).

CONCLUSIONS

PREBOA resulted in less severe ischemia-reperfusion injury at both altitude and ground, while full balloon inflation at altitude exacerbated acidosis and ischemia-reperfusion injury. Efforts should therefore be made to utilize partial balloon occlusion when employing the REBOA catheter.