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

Efficacy and safety of damage control in experimental animal models of injury: protocol for a systematic review and meta-analysis

BACKGROUND

Although abbreviated surgery with planned reoperation (damage control surgery) is now widely used to manage major trauma patients, the procedure and its component interventions have not been evaluated in randomized controlled trials (RCTs). While some have suggested the need for such trials, they are unlikely to be conducted because of patient safety concerns. As animal studies may overcome several of the limitations of existing observational damage control studies, the primary objective of this study is to evaluate the efficacy and safety of damage control versus definitive surgery in experimental animal models of injury.

METHODS/DESIGN

We will search electronic databases (Medline, Embase, PubMed, Web of Science, Scopus, and the Cochrane Library), conference abstracts, personal files, and bibliographies of included articles. We will include RCTs and prospective cohort studies that utilized an animal model of injury and compared damage control surgery (or specific damage control interventions or adjuncts) to definitive surgery (or specific definitive surgical interventions). Two investigators will independently evaluate the internal and external/construct validity of individual studies. The primary outcome will be all-cause mortality. Secondary outcomes will include blood loss amounts; blood pressures and heart rates; urinary outputs; core body temperatures; arterial lactate, pH, and base deficit/excess values; prothrombin and partial thromboplastin times; international normalized ratios; and thromboelastography (TEG) results/activated clotting times. We will calculate summary relative risks (RRs) of mortality and mean differences (for continuous outcomes) using DerSimonian and Laird random effects models. Heterogeneity will be explored using subgroup meta-analysis and meta-regression. We will assess for publication bias using funnel plots and Begg's and Egger's tests. When evidence of publication bias exists, we will use the Duval and Tweedie trim and fill method to estimate the potential influence of this bias on pooled summary estimates.

DISCUSSION

This study will evaluate the efficacy and safety of damage control in experimental animal models of injury. Study results will be used to guide future clinical evaluations of damage control surgery, determine which animal study outcomes may potentially be generalizable to the clinical setting, and to provide guidelines to strengthen the conduct and relevance of future pre-clinical studies.

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.

Temporary rapid bowel ligation as a damage control adjunct improves survival in a hypothermic traumatic shock swine model with multiple bowel perforations

BACKGROUND

Primary intestinal anastomosis is not the right choice for multiple bowel perforations under hemodynamically stable conditions. Our group has employed temporary rapid bowel ligation as a damage control procedure in a hypothermic traumatic shock swine model with multiple bowel perforations and hypothesized that damage control treatment would improve survival in the setting of a damage control surgery.

MATERIALS AND METHODS

The abdomen was shot one time with an experimental modified gun while 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 control (no resuscitation), primary anastomosis (PA), or temporary rapid bowel ligation (damage control group, DC). Animals were resuscitated for 12 h with the shed blood and lactated Ringer solution. Delayed anastomosis was performed in DC 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. The lung and ileum was harvested at the end of the experiment for pathologic evaluation and test of wet/dry weight ratio, TNF-α level, and nuclear factor-κB activations.

RESULTS

All animals suffered extreme physiologic conditions: hypothermia, severe acidosis, hypotension, and depressed cardiac output. Control animals suffered 100% mortality. Compared with the PA group, DC animals required less resuscitation fluid, normalized lactate levels faster, had lower serum creatine kinase, aspartate amino transferase levels and tissue TNF-α level and nuclear factor-κB activations, suffered less severe histopathology, had greater early survival.

CONCLUSIONS

Multiple bowel perforations under hemodynamically stable conditions seem better managed with DC than with PA. Temporary rapid bowel ligation as a damage control adjunct is important to rapid control of multiple bowel perforations instead of a prolonged operative time.

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.