Fluid administration rate for uncontrolled intraabdominal hemorrhage in swine

Comparative Analysis of Whole Blood Infusion Effects: Assessing LifeFlow Versus Pressure Bag in a Sus scrofa Model

BACKGROUND

To improve survival for hemorrhagic shock treatment, guidelines emphasize two patient care priorities: (1) immediate hemorrhage control and (2) early resuscitation with whole blood or blood products. The LifeFlow device is designed to rapidly infuse blood products. However, the effects of using this device compared to pressure-bag systems remain unclear. We hypothesize that there will be no laboratory-measured difference with the blood when infused through the LifeFlow versus the current standard pressure bag system.

METHODS

Two units of fresh whole blood were obtained from a sus scrofa model. One unit was "infused" using the LifeFlow with the other unit used as a control through a standard pressure bag system into an empty bag. The "before" measurements were obtained from blood samples from a standard fresh whole blood collection bag. The blood was "infused" into a whole blood bag devoid of storage solution from which the "after" measurements were obtained.

RESULTS

This study utilized 22 clinically healthy sus scrofa. Blood units were primarily obtained from a left subclavian central line (50.0%). The median time to acquire and administer a unit of blood was similar for both the LifeFlow device (8.4 min and 8.1 min) and the pressure bag (8.7 min and 7.4 min). No significant differences were found in the total time to acquire or administer blood between the two devices. The median volume of blood acquired was 500 mL for both groups. While no significant differences in blood parameters were observed between the two devices, significant differences were noted when comparing pre- and post-transfusion values within each device. For the LifeFlow device, an increase in hemoglobin and chloride levels and a decrease in thromboplastin time and glucose levels were observed. With the pressure bag, only a decrease in blood urea nitrogen was observed.

CONCLUSIONS

In comparing the LifeFlow to the pressure bag, there were no significant differences noted in the total time to acquire or administer a whole unit of blood. However, there were differences with several laboratory parameters of unclear clinical significance.

Conditional Treatment Effect Analysis of Two Infusion Rates for Fluid Challenges in Critically Ill Patients: A Secondary Analysis of Balanced Solution versus Saline in Intensive Care Study (BaSICS) Trial

Rationale: Optimal infusion rate for fluid challenges in critically ill patients is unknown. A large clinical trial comparing two different infusion rates yielded neutral results. Conditional average treatment effect (CATE) assessment may aid in tailoring therapy. Objectives: To estimate CATE in patients enrolled in the BaSICS trial and to assess the effects of receiving CATE model-recommended treatment in terms of hospital mortality. Methods: Post hoc analysis of the BaSICS trial assessing the effect of two infusion rates for the fluid challenge (fast, 999 ml/h, control group; vs. slow, 333 ml/h, intervention group) on hospital mortality. CATE was estimated as the difference in outcome for treatment arms in counterfactuals obtained from a Bayesian model trained in the first half of the trial adjusted for predictors hypothesized to interact with the intervention. The model recommended slow or fast infusion or made no recommendation in the second half. A threshold greater than 0.90 probability of benefit was considered. Results: A total of 10,465 patients were analyzed. The model was trained in 5,230 patients and tested in 5,235 patients. A recommendation could be made in the test set in 19% of patients (14% were recommended the control group and 5% the treatment group); for 81% of patients, no recommendation could be made. Slow infusion was more frequently recommended in cases of planned admissions in younger patients; fast infusion was recommended for older patients with sepsis. Slow infusion rate in the subgroup of patients in the test set in which slow infusion was recommended by the model was associated with an odds ratio of 0.58 (95% credible interval of 0.32-0.90; 0.99 posterior probability of benefit) for hospital mortality. Fast infusion in the subgroup in which the model recommended fast infusion was associated with an odds ratio of 0.72 (credible intervals from 0.54 to 0.91; probability of benefit >0.99). Conclusions: Estimation of CATEs from counterfactual probabilities in data from BaSICS provided additional information on trial data. Agreement between treatment recommendation and actual treatment was associated with lower hospital mortality. Clinical trial registered with clinicaltrials.gov (NCT02875873).

Hemodynamic Effect of Resuscitative Endovascular Balloon Occlusion of the Aorta in Hemodynamic Instability Secondary to Acute Cardiac Tamponade in a Porcine Model

BACKGROUND

The pre-hospital use of Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is increasing, although it remains controversial, in part because of suggested contraindications such as acute cardiac tamponade (ACT). As both the pre-hospital and in-hospital use of REBOA might potentially occur with concurrent ACT, knowledge of the hemodynamic effect of REBOA in this setting is crucial. This study, therefore, aimed at investigating the physiological effects of REBOA in hemodynamic instability secondary to ACT in a porcine model. We hypothesize that REBOA can temporarily increase systemic blood pressure and carotid blood flow, and prolong survival, in hemodynamic shock caused by ACT.

METHODS

Fourteen pigs (24-38 kg) underwent ACT, through true cardiac injury and hemorrhage into the pericardial space, and were allowed to hemodynamically deteriorate. At a systolic blood pressure (SBP) of 50 mm Hg (SBP50) they were randomized to total occlusion REBOA in zone 1 or to a control group. Survival, hemodynamic parameters, carotid blood flow (CBF), femoral blood flow (FBF), cardiac output (CO), end-tidal CO2, and arterial blood gas parameters were analyzed.

RESULTS

REBOA intervention was associated with a significant increase in SBP (50 mm Hg to 74 mm Hg, P = 0.016) and CBF (110 mL/min to 195 mL/min, P = 0.031), with no change in CO, compared to the control group. At 20 min after SBP50, the survival rate in the intervention group was 86% and in the control group 14%, with time to death being significantly longer in the intervention group.

CONCLUSIONS

This randomized animal study demonstrates that REBOA can help provide hemodynamic stabilization and prolong survival in hemodynamic shock provoked by ACT. It is important to stress that our study does not change the fact that urgent pericardiocentesis or cardiac surgery is, and should remain, the standard optimal treatment for ACT.Level of evidence: Prospective, randomized, experimental animal study. Basic science study, therapeutic.

Hemodynamic Parameters in the Assessment of Fluid Status in a Porcine Hemorrhage and Resuscitation Model

BACKGROUND

Measuring fluid status during intraoperative hemorrhage is challenging, but detection and quantification of fluid overload is far more difficult. Using a porcine model of hemorrhage and over-resuscitation, it is hypothesized that centrally obtained hemodynamic parameters will predict volume status more accurately than peripherally obtained vital signs.

METHODS

Eight anesthetized female pigs were hemorrhaged at 30 ml/min to a blood loss of 400 ml. After each 100 ml of hemorrhage, vital signs (heart rate, systolic blood pressure, mean arterial pressure, diastolic blood pressure, pulse pressure, pulse pressure variation) and centrally obtained hemodynamic parameters (mean pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure, cardiac output) were obtained. Blood volume was restored, and the pigs were over-resuscitated with 2,500 ml of crystalloid, collecting parameters after each 500-ml bolus. Hemorrhage and resuscitation phases were analyzed separately to determine differences among parameters over the range of volume. Conformity of parameters during hemorrhage or over-resuscitation was assessed.

RESULTS

During the course of hemorrhage, changes from baseline euvolemia were observed in vital signs (systolic blood pressure, diastolic blood pressure, and mean arterial pressure) after 100 ml of blood loss. Central hemodynamic parameters (mean pulmonary artery pressure and pulmonary capillary wedge pressure) were changed after 200 ml of blood loss, and central venous pressure after 300 ml of blood loss. During the course of resuscitative volume overload, changes were observed from baseline euvolemia in mean pulmonary artery pressure and central venous pressure after 500-ml resuscitation, in pulmonary capillary wedge pressure after 1,000-ml resuscitation, and cardiac output after 2,500-ml resuscitation. In contrast to hemorrhage, vital sign parameters did not change during over-resuscitation. The strongest linear correlation was observed with pulmonary capillary wedge pressure in both hemorrhage (r2 = 0.99) and volume overload (r2 = 0.98).

CONCLUSIONS

Pulmonary capillary wedge pressure is the most accurate parameter to track both hemorrhage and over-resuscitation, demonstrating the unmet clinical need for a less invasive pulmonary capillary wedge pressure equivalent.

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