Effect of SAM junctional tourniquet on respiration when applied in the axilla: A swine model

Abstract

Purpose: SAM junctional tourniquet (SJT) has been applied to control junctional hemorrhage. However, there is limited information about its safety and efficacy when applied in the axilla. This study aims to investigate the effect of SJT on respiration when used in the axilla in a swine model.

Methods: Eighteen male Yorkshire swines, aged 6-month-old and weighing 55 - 72 kg, were randomized into 3 groups, with 6 in each. An axillary hemorrhage model was established by cutting a 2 mm transverse incision in the axillary artery. Hemorrhagic shock was induced by exsanguinating through the left carotid artery to achieve a controlled volume reduction of 30% of total blood volume. Vascular blocking bands were used to temporarily control axillary hemorrhage before SJT was applied. In Group I, the swine spontaneously breathed, while SJT was applied for 2 h with a pressure of 210 mmHg. In Group II, the swine were mechanically ventilated, and SJT was applied for the same duration and pressure as Group I. In Group III, the swine spontaneously breathed, but the axillary hemorrhage was controlled using vascular blocking bands without SJT compression. The amount of free blood loss was calculated in the axillary wound during the 2 h of hemostasis by SJT application or vascular blocking bands. After then, a temporary vascular shunt was performed in the 3 groups to achieve resuscitation. Pathophysiologic state of each swine was monitored for 1 h with an infusion of 400 mL of autologous whole blood and 500 mL of lactated ringer solution. T_b and T₀ represent the time points before and immediate after the 30% volume-controlled hemorrhagic shock, respectively. T₃₀, T₆₀, T₉₀ and T₁₂₀, denote 30, 60, 90, and 120 min after T₀ (hemostasis period), while T₁₅₀, and T₁₈₀ denote 150 and 180 min after T₀ (resuscitation period). The mean arterial pressure and heart rate were monitored through the right carotid artery catheter. Blood samples were collected at each time point for the analysis of blood gas, complete cell count, serum chemistry, standard coagulation tests, etc., and thromboelastography was conducted subsequently. Movement of the left hemidiaphragm was measured by ultrasonography at T_b and T₀ to assess respiration. Data were presented as mean ± standard deviation and analyzed using repeated measures of two-way analysis of variance with pairwise comparisons adjusted using the Bonferroni method. All statistical analyses were processed using GraphPad Prism software.

Results: Compared to T_b, a statistically significant increase in the left hemidiaphragm movement at T₀ was observed in Groups I and II (both p < 0.001). In Group III, the left hemidiaphragm movement remained unchanged (p = 0.660). Compared to Group I, mechanical ventilation in Group II significantly alleviated the effect of SJT application on the left hemidiaphragm movement (p < 0.001). Blood pressure and heart rate rapidly increased at T₀ in all three groups. Respiratory arrest suddenly occurred in Group I after T₁₂₀, which required immediate manual respiratory assistance. PaO₂ in Group I decreased significantly at T₁₂₀, accompanied by an increase in PaCO₂ (both p < 0.001 vs. Groups II and III). Other biochemical metabolic changes were similar among groups. However, in all 3 groups, lactate and potassium increased immediately after 1 min of resuscitation concurrent with a drop in pH. The swine in Group I exhibited the most severe hyperkalemia and metabolic acidosis. The coagulation function test did not show statistically significant differences among three groups at any time point. However, D-dimer levels showed a more than 16-fold increase from T₁₂₀ to T₁₈₀ in all groups.

Conclusion: In the swine model, SJT is effective in controlling axillary hemorrhage during both spontaneous breathing and mechanical ventilation. Mechanical ventilation is found to alleviate the restrictive effect of SJT on thoracic movement without affecting hemostatic efficiency. Therefore, mechanical ventilation could be necessary before SJT removal.

Keywords: Axilla; Junctional hemorrhage; Respiration; Swine model; Tourniquet.

Fig. 1

SAM junctional tourniquet (SJT) instructions for the axilla in the swine model. (A) Place SJT loosely around the upper thorax of the swine and place a 25 mm-diameter pressure sensor between the target compression device (TCD) surface and the swine to measure the pressure exerted by SJT. Then, position the TCD over the area to be compressed; (B) Connect the belt using the buckle after the TCD is held in place, and secure the buckle to hear the first “click”; (C) Press the extra belt on the Velcro to hear the second “click”; (D) Manually inflate SJT via using the hand pump to control hemorrhage; (E) Swine applicated with SJT pressure sensor and TCD; and (F) Swine before SJT application.

Fig. 2

Experimental protocol. (A) The algorithm of the experiment; and (B) Experimental flow chart. SJT: SAM junctional tourniquet; TVS: Temporary vascular shunt.

Fig. 3

Movement of the left hemidiaphragm was measured by M-mode ultrasonography.

Fig. 4

Hemodynamic changes in Groups Ⅰ, Ⅱ and Ⅲ. (A) Mean arterial pressure (MAP) and (B) heart rate (HR); (C) The arterial partial pressure of PaO₂ and (D) PaCO₂ gases. MAP in Groups Ⅰ, Ⅱ and Ⅲ from T_b to T₀ was accompanied by an increase in HR in the 3 groups. From T₀ to T₁₂₀, MAP sharply increased and then gradually returned to baseline levels, concurrently with slow growth in HR. However, after T₁₂₀, MAP sharp decreased, while HR significant increased. In addition, the blood gases changed significantly at T₁₂₀, particularly in Group Ⅰ (p < 0.001 vs. Groups II and III), and then returned to baseline levels from T₁₂₀ to T₁₈₀.

Fig. 5

Metabolic changes in blood samples collected at different time points (T_b, T₀, T₃₀, T₆₀, T₉₀, T₁₂₀, T₁₅₀ and T₁₈₀) during the experiments. (A) Potassium; (B) Lactate concentrations; (C) pH; (D) Blood urea nitrogen; (E) Serum creatinine concentration; (F) Percentage of hematocrit; (G) Platelet count; (H) Creatine kinase; (I) Aspartate aminotransferase enzymatic activities; and (J) D-dimer. ∗p < 0.001 comparison between T_b and T₁₈₀; #p < 0.001 comparison between T₁₂₀ and T₁₈₀.

Fig. 6

Thromboelastogram changes in blood samples collected at different time points (A) Clot initiation; (B) Clot polymerization; (C) Clotting angle; (D) Clot strength; and (E) Clotting index. #p < 0.001 comparison between T₀ and T₆₀.