Establishment of an Acute Superior Mesenteric Artery Injury Model for Damage Control Surgery

H12‐(ADP)‐liposomes for hemorrhagic shock in thrombocytopenia: Mesenteric artery injury model in rabbits

Background

Objective

Methods

Results

Conclusion

Time course study of intestinal epithelial barrier disruption in acute mesenteric venous thrombosis

BACKGROUND

Acute superior mesenteric venous thrombosis (ASMVT) is an abdominal vascular condition. Early recanalization is essential to successful treatment. The aim of the study was to establish rabbit models of ASMVT and assess the time course of intestinal epithelial barrier disruption.

METHODS

After surgical exposure of superior mesenteric vein (Sham group), large-vessel (L-group) and small-vessel (S-group) models were established by endothelium damage, stenosis creation, and thrombin injection. At baseline, 6, 9, and 12 h, hemodynamic and serum parameters were tested. Serum from ASMVT patients diagnosed at 24, 36, 48, and 60 h from symptom onset was collected. Intestinal barrier disruption was assessed by tight junction (TJ) protein expression, morphology changes, and bacterial translocation. Mesenteric arteriospasm was measured by flow velocity and intestinal wet/dry weight ratio. The serum level of intestinal fatty acid-binding protein and endotoxin in patients was also measured as an indicator for intestinal barrier function.

RESULTS

Severe acidosis and lacticemia were observed in both the groups. The L-group experienced greater hemodynamic alteration than the S-group. Intestinal barrier disruption was detected by significantly decreased TJ protein expression, histology and ultrastructure injury of TJ, increased permeability, and bacterial translocation, at 9 h in the S-group and 12 h in the L-group. Secondary mesenteric arteriospasm occurred at the same time of complete intestinal barrier disruption and could be a significant cause of bowel necrosis. Significant increased level of intestinal fatty acid-binding protein and endotoxin was found in patients at 48 h in the S-group type and 60 h in the L-group type.

CONCLUSIONS

The ASMVT animal models of both the types were first established. The loss of intestinal barrier function occurred at 6 h in the S-group model and 9 h in the L-group model. For clinical patients, the time window extended to 36 h in the S-group type and 48 h in the L-group type.

Intraintestinal drainage as a damage control surgery adjunct in a hypothermic traumatic shock swine model with multiple bowel perforations

BACKGROUND

Temporary bowel ligation (TL) has been proposed to prevent contamination as a damage control procedure in multiple bowel perforations. However, bacteria translocation and intestinal ischemia may develop in a prolonged duration. We here hypothesized that intraintestinal drainage combined with temporary ligation (D-TL) would decrease intestinal injury and improve survivals in a gunshot multiple bowel perforation swine model in the setting of a damage control surgery.

MATERIALS AND METHODS

The abdomen was shot one time with an experimental modified gun whereas pigs were hemorrhaged to a mean arterial pressure of 40 mm Hg and maintained in shock for 40 min. Cold lactated Ringer solution was gradually infused to induce hypothermia. Animals were randomized to primary anastomosis, TL and intraintestinal D-TL groups (n = 8). Animals were resuscitated for 12 h with the shed blood and lactated Ringer solution. Delayed anastomosis was performed in TL and D-TL animals after resuscitation. Surviving animals were humanely killed 24 h after operation. Systemic hemodynamic parameters were recorded and blood samples were obtained for biochemical assays. Intra-abdominal pressure, portal vein and peripheral vein bacterial cultures, small intestine hematoxylin-eosin staining, and transmission electron microscopy examination were performed at 0, 2, 6, 12, and 24 h after the surgery.

RESULTS

All animals suffered extreme physiologic conditions as follows: hypothermia, severe acidosis, hypotension, and depressed cardiac output. Compared with the primary anastomosis and TL group, D-TL animals required less resuscitation fluid, suffered a lower intra-abdominal hypertension and bacterial translocation, normalized lactate levels faster, had lower serum creatine kinase, aspartate aminotransferase levels and tissue TNF-α level, and nuclear factor-kB activations and thus had greater early survival.

CONCLUSIONS

Compared with primary intestinal anastomosis and TL, rapid bowel ligation combined with intraintestinal drainage as a damage control adjunct improved survivals in a multiple bowel perforation swine model in the setting of damage control surgery.

Relevance of induced and accidental hypothermia after trauma-haemorrhage-what do we know from experimental models in pigs?

Recent experimental research has either focused on the role of accidental hypothermia as part of the lethal triad after trauma or tried to elucidate the effects of therapeutically induced hypothermia on the posttraumatic course. Induced hypothermia seems to reduce the mortality in experimental models of trauma-haemorrhage. As potential mechanisms, a decrease of cellular metabolism, beneficial effects on haemodynamic function and an attenuation of the inflammatory response have been described. However, negative side effects of hypothermia have to be considered, such as impairment of the coagulatory function and immunosuppressive effects. Furthermore, the optimal strategy for the induction of hypothermia (magnitude, duration, timing, cooling rate, etc.) and subsequent rewarming remains unclear. Nevertheless, this piece of information is essential before considering hypothermia as a treatment strategy for severely injured patients. This review aims to elaborate the differences between accidental and induced hypothermia and to summarize the current knowledge of the potential therapeutic use of induced hypothermia suggested in porcine models of trauma-haemorrhage.

Prolonged indwelling time of temporary vascular shunts is associated with increased endothelial injury in the porcine mesenteric artery

BACKGROUND

Temporary intravascular shunts (TIVS) have been used as a damage control surgery (DCS) adjuncts in superior mesenteric artery (SMA) injuries, both experimentally and clinically. However, no study to date has evaluated the relationship between shunt indwelling time and resultant endothelial cell (EC) injury. We hypothesized that prolonged use of TIVS in SMA injuries would jeopardize EC integrity.

METHOD

After laparotomy, the SMA was clamped and transected while pigs were hemorrhaged to 40 mm Hg for 30 minutes. A TIVS was inserted between transected ends of the SMA without systemic anticoagulation. Totally, 24 animals were resuscitated and randomized to different shunt indwelling time groups: A, 3 hours; B, 6 hours; C, 9 hours; and D, 12 hours. Patency of shunts was monitored and recorded. Continuous wave Doppler was used as a determinant of adequacy of flow through the shunts. Transmural SMA biopsies from areas of TIVS placement were examined with electron microscopy for histopathologic injury after staining with hematoxylin and eosin and immunofluorescence using a validated histopathologic injury score (minimum-maximum score: 0-4).

RESULTS

Severity of endothelial injury was observed to be directly related to shunt indwell time. SMA transmural biopsies harvested from group D animals showed the most profound injury, demonstrating extensive EC denudations and marked intimal rupture (injury grade, 3.4 ± 0.2). Sections from group A animals revealed the mildest EC injury (1.3 ± 0.3 vs. group D p < 0.01). No significant difference was detected between group A and B. EC injury grade in group C (2.7 ± 0.6) was higher than that in group B (1.8 ± 0.6) but did not reach statistical significance (p = 0.58).

CONCLUSION

When possible, vascular reconstruction following use of shunts should include an interposition graft after debridement of the arterial edges having interfaced with the shunt. Finally, to minimize intimal injury to the native vessel, this model suggests that indwell times of shunts should be <9 hours.

Comparisons of three surgical procedures on intestine ischemia reperfusion injury in a superior mesenteric artery injury model

BACKGROUND

Temporary ligation, primary anastomosis, and temporary shunt have been reported to deal with superior mesenteric artery (SMA) injuries. We aimed to investigate which brought minimal ischemia reperfusion injury in a hypothermic traumatic shock swine model.

METHODS

SMA was completely clamped while pigs were hemorrhaged to a mean arterial pressure (MAP) of 40 mm Hg. Animals were then randomized into temporary ligation (A, n=8), primary anastomosis (B, n=8), temporary shunt (C, n=8), and control groups (n=4). Animals in group A remained SMA interrupted for additional 1h while the other groups underwent the corresponding procedures immediately. Intestine injury was assessed by histologic examination and measurement of lipid peroxidations at the end of ischemia and experiment.

RESULTS

Overall mortality rate was 50%, 25%, and 0% in groups A, B, and C, respectively (P<0.05). The total intestine ischemia time was predominantly shorter in group C in the other groups. Remarkable elevations of malonaldehyde (MDA) in small intestine were noted after reperfusion in group A. Animals in other groups, however, did not exacerbate during the 6-h reperfusion (resuscitation period). Group C showed the lowest MDA level at the end of experiment. Myeloperoxidase (MPO) levels showed no significant elevations during the ischemia or early reperfusion period; nevertheless, it reached approximately 3- to 6-fold in groups A and B (compared with baseline, P<0.01), and remained unchanged in group C at the end of experiment.

CONCLUSION

Our study suggests that temporary shunt insertion might be preferred as it shortens ischemia time, alleviates intestinal ischemia/reperfusion injury, and thus decreases early mortality in this animal model.

Temporary intravascular shunting improves survival in a hypothermic traumatic shock swine model with superior mesenteric artery injuries

BACKGROUND

Repairs of superior mesenteric artery (SMA) injuries are difficult and often result in high mortality. Our group has employed temporary intravascular shunts (TIVS) as a damage control procedure in a SMA transection model and hypothesized that TIVS would improve survival when compared with primary vascular anastomosis in the setting of a damage control surgery.

METHODS

The SMA was clamped and completely transected while pigs were hemorrhaged to a mean arterial pressure of 40 mmHg and maintained in shock for 30 minutes. Cold lactated Ringer's solution was gradually infused while the abdomen was open to induce hypothermia. Animals were randomized to control (no resuscitation), primary anastomosis (PA), or temporary shunting (TS) of the SMA. Animals were resuscitated for 6 hours with the shed blood and lactated Ringer's solution. Delayed anastomosis was performed in TS animals after resuscitation. Surviving animals were humanely killed 2 days after operation. Systemic hemodynamic parameters were recorded hourly. The ileum was harvested at the end of resuscitation and experiment for pathologic evaluation.

RESULTS

All animals suffered extreme physiologic conditions: hypothermia, severe acidosis, hypotension, and depressed cardiac output and oxygen delivery. Control animals suffered 100% mortality. Compared with the PA group, TS animals required less resuscitation fluid, retained higher SMA flow rates, normalized lactate levels faster, suffered less severe intestine histopathology, and had greater early survival.

CONCLUSION

Damage control surgery in the setting of SMA transection seems better managed with TS than with PA. Further validation of this model is required before generalization to human applications.