The impact of ischemic intervals on neuromuscular recovery in a porcine (Sus scrofa) survival model of extremity vascular injury.

San Antonio Military Medicine Center Consortium, Wilford Hall United States Air Force Medical Center, the 59th Clinical Research Squadron, and Genesis Concepts & Consultants (under USAF Contract No: FA7014-09-D-0008), Lackland Air Force Base, San Antonio, TX, USA.
Journal of vascular surgery: official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter (Impact Factor: 2.98). 10/2010; 53(1):165-73. DOI: 10.1016/j.jvs.2010.07.012
Source: PubMed

ABSTRACT Despite advances in revascularization following extremity vascular injury, the relationship between time to restoration of flow and functional limb salvage is unknown. The objectives of this study are to describe a large animal survival model of hind limb ischemia/reperfusion and define neuromuscular recovery following increasing ischemic periods.
Sus scrofa swine (N = 38; weight, 87 ± 6.2 kg) were randomized to iliac artery occlusion for 0 (Control), 1 (1HR), 3 (3HR), or 6 (6HR) hours, followed by vessel repair and 14 days of recovery. Additionally, one group underwent iliac artery division with no restoration of flow (Ligation), and one group underwent iliac artery exposure only without intervention (Sham). A composite physiologic measure of recovery (PMR) was generated to assess group differences over 14 days of survival. PMR included limb function (Tarlov score) and electrophysiologic measures (compound muscle action potential amplitude, sensory nerve action potential amplitude, and nerve conduction velocity). Using the PMR and extrapolating the point at which recovery following ligation crosses the slope connecting recovery after 3 and 6 hours of ischemia, an estimate of the ischemic threshold for the hind limb is made. These results were correlated with peroneus muscle and peroneal nerve histology.
Baseline physiologic characteristics were similar between groups. Neuromuscular recovery in groups with early restoration of flow (Control, 1HR, 3HR) was similar and nearly complete (92%, 98%, and 88%, respectively; P > .45). While recovery was diminished in both 6HR and Ligation, Ligation, rather than repair, exhibited greater recovery (68% vs 53%; P < .05). These relationships correlated with the pathologic grade of degeneration, necrosis, and fibrosis (P < .05). The PMR model predicts minimal and similar persistent loss of function in groups undergoing early surgical restoration of flow (Control 8%, 1HR 1%, 3HR 12%; P > .45). In contrast, the Ligation group exhibited the greatest degree of injury early in the reperfusion period, followed by more complete recovery and at a faster rate than 6HR. Extrapolating from the PMR the point at which Ligation (68% recovery) crosses the slope connecting 3 hours (84% recovery) and 6 hours (53% recovery) of ischemia estimates the ischemic threshold to be 4.7 hours. Restoration of flow at ischemic intervals exceeding this are associated with less physiologic recovery than ligation.
In this model, surgical and therapeutic adjuncts to restore extremity perfusion early (1-3 hours) after extremity vascular injury are most likely to provide outcomes benefit compared with delayed restoration of flow or ligation. Furthermore, the ischemic threshold of the extremity after which neuromuscular recovery is significantly diminished is less than 5 hours. Additional studies are necessary to determine the effect of other factors such as shock or therapeutic measures on this ischemic threshold.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Traumatic injury to the popliteal vascular zone remains a challenging problem on the modern battlefield and is frequently associated with more complications than other vascular injuries. Limb salvage and morbidity (graft infection, thrombosis and delayed haemorrhage) were studied. All popliteal vascular injuries over an 8 month period admitted to the Military Base Hospital were analyzed. Local limb evaluation included confirmation of the presence of ischaemia, extent of soft tissue damage, muscle viability after calf fasciotomy, and neurological injury. Ischaemic time was recorded from the time of injury to definitive revascularization. If there was a prior attempt at reconstruction, the amputation was considered delayed. For a series of 44 patients with popliteal vascular injury average time to presentation was 390min, 46% were completely ischaemic. Of those 39 (89%) had popliteal artery injuries. There were 24 (62%) complete popliteal artery transections and associated venous (69%) and osseous (46%) injuries. The preferred technique of repair was inter-position venous graft (IPVG) (54%). Eleven immediate amputations were performed (28%). There were 13 wound infections (33%), 5 early graft thromboses (5 of 21 IPVG, 238%), 2 anastomotic disruptions (2 of 21 IPVG, 9%), which resulted in 4 delayed amputations. Mortality was 5% (2 patients). In this case series of popliteal artery injury early identification of limbs at risk, early four compartment fasciotomy, temporary intra-luminal shunting, definitive repair of concomitant venous injuries and aggressive treatment of haemodynamic instability were shown to be beneficial in achieving reasonable outcome in an austere environment with limited recourses.
    Injury 01/2014; 45(5). DOI:10.1016/j.injury.2014.01.003 · 2.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ischemia and reperfusion injuries present major challenges for both military and civilian medicine. Improved methods for assessing the effects and predicting outcome could guide treatment decisions. Specific issues related to ischemia and reperfusion injury can include complications arising from tourniquet use, such as microvascular leakage in the limb, loss of muscle strength and systemic failures leading to hypotension and cardiac failure. Better methods for assessing the viability of limbs/tissues during ischemia and reducing complications arising from reperfusion are critical to improving clinical outcomes for at-risk patients. The purpose of this research is to develop and assess possible prediction models of outcome for acute limb ischemia using a pre-clinical model. Our model relies only on non-invasive imaging data acquired from an animal study. Outcome is measured by pathology and functional scores. We explore color, texture, and temporal features derived from both color and thermal motion imagery acquired during ischemia and reperfusion. The imagery features form the explanatory variables in a model for predicting outcome. Comparing model performance to outcome prediction based on direct observation of blood chemistry, blood gas, urinalysis, and physiological measurements provides a reference standard. Initial results show excellent performance for the imagery-base model, compared to predictions based direct measurements. This paper will present the models and supporting analysis, followed by recommendations for future investigations.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Groin application of Combat Ready Clamp (CRoC) in pigs elicits an acute inflammation in underlying ischemic tissues. This study examined functional recovery of pigs' hind leg(s) following 2 hours of CRoC application.
    Journal of Trauma and Acute Care Surgery 09/2014; 77(3 Suppl 2):S101-S108. DOI:10.1097/TA.0000000000000350 · 2.50 Impact Factor