Prolonging the zone 1 aortic occlusion time to 4 hours using a partial resuscitative endovascular balloon in a swine model

Abstract

Background: The clinical usage of the resuscitative endovascular balloon occlusion of the aorta (REBOA) is limited by distal ischemia resulting from complete aortic occlusion. We hypothesized that animals would physiologically tolerate the prolonged partial occlusion using the novel partially occluding REBOA (pREBOA) with survivable downstream injuries.

Methods: This study used the pREBOA-PRO catheter in a previously established swine model. Female Yorkshire swine (n = 10) underwent a volume-controlled hemorrhage (40% estimated blood). After 1 hour of shock (mean arterial pressure, 28-32 mm Hg), animals were randomized to partial occlusion for either 2 hours or 4 hours. The pREBOA was inflated in zone 1 to achieve partial occlusion defined as a distal systolic blood pressure (SBP) of 20 ± 2 mm Hg. The balloon was deflated at the end of the occlusion period, and animals were resuscitated for 2 hours. Tissues were examined for gross and histologic injury. The primary endpoint was histologic organ injury, and secondary end points were hemodynamic variables and degree of distal organ ischemia.

Results: All animals survived to the endpoint. Both groups had similar proximal and distal SBP at baseline, with a divergence of pressures ranging from 55 mm Hg to 90 mm Hg on inflation. The lactate levels increased throughout the occlusion and decreased approximately 40% during the observation period. More animals required norepinephrine and fluid in the 4-hour group compared with the 2-hour group. There was no gross small bowel ischemia noted in the 2-hour animals. The 4-hour group had surgically resectable patchy short segment ischemia. Neither group showed nonsurvivable organ ischemia on pathology or laboratory values.

Conclusion: This is the first study showing that the zone 1 aorta can be occluded for over 4 hours using a new pREBOA device without need for balloon titration. In conclusion, simple changes in balloon design offer reliable partial aortic occlusion, with potentially survivable and surgically manageable downstream injuries.

Graphical abstract

Figure 1

A schematic of the pREBOA-PRO device in various stages of partial aortic occlusion and in the zone 1 aorta. The pREBOA-PRO is a semi-compliant balloon with ridges creating channels along the balloon. With full inflation, the balloon causes a complete occlusion. The variable balloon shape during partial occlusion allows for a gradual change in flow as the balloon is inflated and deflated. Copyright 2023, Prytime Medical Devices, Inc. All Rights Reserved. Used with Permission.

Figure 2

Experimental timeline. Following instrumentation, all animals underwent 40% hemorrhage over a 20-min period. They then entered a 1-h period of shock (MAP goal 28–32 mm Hg). Animals then underwent pREBOA-PRO inflation for 2 or 4 h. Whole blood transfusion was then started, and after 50% of the blood was returned, the balloon was slowly deflated. Following completion of transfusion, the animals were survived for a 2-h period of critical care and then euthanized.

Figure 3

Proximal and distal systolic blood pressures in 2 hr and 4 hr groups throughout the experiment. Data presented as group mean ± standard deviation. (A) 2 h, (B) 4 h.

Figure 4

Data presented as group mean ± standard deviation (A) Total norepinephrine dose and (B) Lactated Ringer's volume by experimental group. Statistically significant differences between groups using a Student's t test are designated on all figures as * (p < 0.05).

Figure 5

Histologic Scoring. The tissues were fixed, sectioned, and stained with hematoxylin and eosin. The data are presented as mean ± standard deviation of histologic injury scores. (A) Small bowel (B) Liver (C) Lung (D) Kidney. Statistically significant differences between groups using a Student's t test are designated on all figures as * (p < 0.05). See Supplementary Table 1–3, 6, http://links.lww.com/TA/D44, for full scoring details, maximum value on y axis demonstrates tissue necrosis. Representative sections in a 4 hour animal are display in the respective panels. (hr = hour).