Validation of a novel partial resuscitative endovascular balloon occlusion of the aorta device in a swine hemorrhagic shock model: Fine tuning flow to optimize bleeding control and reperfusion injury.

OBJECTIVES: Partial restoration of aortic flow during resuscitative endovascular balloon occlusion of the aorta (REBOA) is advocated by some to mitigate distal ischemia. Our laboratory has validated the mechanics and optimal partial REBOA (pREBOA) flow rates using a prototype device. We hypothesize that pREBOA will increase survival when compared with full REBOA (fREBOA) in prolonged nonoperative management of hemorrhagic shock. METHODS: Twenty swine underwent placement of aortic flow probes, zone 1 REBOA placement, and 20% blood volume hemorrhage. They were randomized to either solid organ or abdominal vascular injury. The pREBOA arm (10 swine) underwent full inflation for 10 minutes and then deflation to a flow rate of 0.5 L/min for 2 hours. The fREBOA arm (10 swine) underwent full inflation for 60 minutes, followed by deflation/resuscitation. The primary outcome is survival, and secondary outcomes are serologic/pathologic signs of ischemia-reperfusion injury and quantity of hemorrhage. RESULTS: Two of 10 swine survived in the fREBOA group (2/5 solid organ injury; 0/5 abdominal vascular injury), whereas 7 of 10 swine survived in the pREBOA group (3/5 solid organ injury, 4/5 abdominal vascular injury). Survival was increased (p = 0.03) and hemorrhage was higher in the pREBOA group (solid organ injury, 1.36 ± 0.25 kg vs. 0.70 ± 0.33 kg, p = 0.007; 0.86 ± 0.22 kg vs. 0.71 ± 0.28 kg, not significant). Serum evidence of ischemia was greater with fREBOA, but this was not significant (e.g., lactate, 16.91 ± 3.87 mg/dL vs. 12.96 ± 2.48 mg/dL at 120 minutes, not significant). Swine treated with pREBOA that survived demonstrated trends toward lower alanine aminotransferase, lower potassium, and higher calcium. The potassium was significantly lower in survivors at 60 minutes and 90 minutes time points (5.97 ± 0.60 vs. 7.53 ± 0.90, p = 0.011; 6.67 ± 0.66 vs. 8.15 ± 0.78, p = 0.029). Calcium was significantly higher at 30 minutes, 60 minutes, and 90 minutes (8.56 ± 0.66 vs. 7.50 ± 0.40, p = 0.034; 8.63 ± 0.62 vs. 7.15 ± 0.49, p = 0.019; 8.96 ± 0.64 vs. 7.00, p = 0.028). CONCLUSION: Prolonged pREBOA at a moderate distal flow rate provided adequate hemorrhage control, improved survival, and had evidence of decreased ischemic injury versus fREBOA. Prophylactic aggressive calcium supplementation may have utility before and during the reperfusion phase.

Establishing Absolute Lymphocyte Count Thresholds for Further Review of Peripheral Blood Lymphocytosis to Judiciously Screen for Monoclonal B-Cell Populations in Older Adults.

OBJECTIVES: Lymphocytosis may represent either a lymphoproliferative disorder (LPD) or a reactive process. The absolute lymphocyte count (ALC) threshold for further evaluation of lymphocytosis is not well established. METHODS: We prospectively performed flow cytometry on blood samples from patients 50 years or older with ALCs of 4.0 × 109 cells/L or greater without a history of an LPD. RESULTS: Monoclonal B-cell populations were found in 34 (19.1%) of 178 cases, with incidence increasing with age. In patients younger than 75 years, no monoclonal B-cell population was identified in patients with ALCs less than 4.4 × 109 cells/L, while such clones were found below and above this threshold in patients 75 years and older. CONCLUSIONS: These findings support a threshold for smear review and flow cytometry no lower than 4.4 × 109 cells/L in patients younger than 75 years and a threshold as low as 4.0 × 109 cells/L in patients 75 years and older.

Mast cell tryptase in a case of anaphylaxis due to repeat antibiotic exposure.

Mast cell tryptase can be an indicator of type I hypersensitivity reaction and thus may serve as a surrogate marker of anaphylaxis. A 34-year-old white male patient presented with a history of systemic lupus erythematosus. Shortly after administration of cefazolin for dialysis, he developed pruritus and shortness of breath. He expired an hour later. Autopsy excluded anatomic causes of death. There was an elevated postmortem mast cell tryptase level, 29.2 ng/mL. For mast cell tryptase level to be useful, the patient must survive long enough after exposure to an allergen for mast cells to release this enzyme. A credible allergen must be identified. In this case such, mast cell tryptase could establish anaphylaxis as the cause of death. The case suggests that in a patient with autoimmune disease, it may be prudent to test for immune reaction to a drug before administering it a second time via pinprick or other method.

Massive internal injury in the absence of significant external injury after collisions of passenger vehicles with much larger vehicles.

We have encountered cases of motor vehicle collisions in which there was relatively little external trauma, but there were massive internal injuries that were much more extensive than might be expected from the external examination. Two cases were collisions between trains and pickup trucks, the third a collision between a semi trailer and a van. In all three cases, the external examination showed minor abrasions and lacerations. Internally, however, there were massive injuries which were fatal. While the significant injuries in our cases were not surprising given the force of the collisions involved, it is interesting that the external examination showed relatively little injury. We speculate that collisions between passenger vehicles and very large vehicles generate massive internal injuries by transmission of force through the victims.