Photocurable extracellular matrix sealant for cessation of venous hemorrhage.

Hemorrhage is the second leading cause of death in patients under 46 years of age in the United States. Cessation of hemorrhage prevents hemorrhagic shock and tissue hypoxia. Controlling the bleed via direct pressure or tourniquet is often the first line of defense, but long-term care requires staples, hemostatic agents, or sealants that seal the vessel and restore blood flow. Here, we compare a new photocurable extracellular matrix sealant (pcECM) with low, medium, and high crosslink density formulations to a commercially available fibrin-based sealant, TISSEEL®. pcECM has potential uses in surgical and remote settings due to room temperature storage conditions and fast preparation time. Here, we determine if pcECM sealant can stop venous hemorrhage in a murine model, adhere to the wound site in vivo throughout the wound-healing process, and has the mechanical properties necessary for stopping hemorrhage. Adjusting pcECM crosslinking density significantly affected viscosity, swelling, burst strength, tensile strength, and elasticity of the sealant. 3-Dimensional ultrasound volume segmentations showed pcECM degrades to 17 ± 8% of its initial implant volume by day 28. Initially, local hemodynamic changes were observed, but returned close to baseline levels by day 28. Acute inflammation was observed near the puncture site in pcECM implanted mice, and we observed inflammatory markers at the 14-day explant for both sealants. pcECM and fibrin sealant successfully sealed the vessel in all cases, and consistently degraded over 14-28 days. pcECM is a durable sealant with tunable mechanical properties and possible uses in hemorrhage control and other surgical procedures.

In Vivo Visualization and Quantification of Rat Laryngeal Blood Supply After Hydration Challenge.

OBJECTIVES: Systemic dehydration decreases total body blood volume; however, hemodynamic alterations at the level of local organs, such as the larynx, remain unclear. Here we sought to quantify superior thyroid artery (STA) blood flow after dehydration and rehydration using in vivo magnetic resonance angiography (MRA) and ultrasound imaging in a rat model. METHODS: Male Sprague-Dawley rats (N = 17) were included in this prospective, repeated measures design. Rats first underwent MRA to determine baseline STA cross-sectional area, followed by high-frequency in vivo ultrasound imaging to measure STA blood velocity at baseline. Next, rats were systemically dehydrated (water withholding), followed by rehydration (water ad-lib). Ultrasound imaging was repeated immediately after dehydration and following rehydration. The STA blood velocity and STA cross-sectional area were used to compute STA blood flow. Three rats served as temporal controls for ultrasound imaging. To determine if the challenges to hydration status affected the STA cross-sectional area, four rats underwent only MRA at baseline, dehydration, and rehydration. RESULTS: Systemic dehydration resulted in 10.5% average body weight loss. Rehydration resulted in average body weight gain of 10.9%. Statistically significant reductions were observed in STA mean blood flow rate after dehydration. Rehydration reversed these changes to pre-dehydration levels. No significant differences were observed in STA cross-sectional area with dehydration or rehydration. CONCLUSION: Systemic dehydration decreased blood flow in the superior thyroid artery. Rehydration restored blood flow in the STA. Change in hydration status did not alter the STA cross-sectional area. These preliminary findings demonstrate the feasibility of using ultrasound and MRA to quantify hemodynamic changes and visualize laryngeal blood vessels. LEVEL OF EVIDENCE: NA Laryngoscope, 134:779-785, 2024.

Aortic dissection detection and thrombus structure quantification using volumetric ultrasound, histology, and scanning electron microscopy.

Aortic dissection occurs when a weakened portion of the intima tears, and a separation of layers propagates along the aortic wall to form a false lumen filled with active blood flow or intramural thrombus. The unpredictable nature of aortic dissection formation and need for immediate intervention leaves limited serial human image data to study the formation and morphological changes that follow dissection. We used volumetric ultrasound examination, histology, and scanning electron microscopy (SEM) to examine intramural thrombi at well-defined timepoints after dissection occurs in apolipoprotein E-deficient mice infused with angiotensin II (n = 71). Stratification of red blood cell (RBC) morphologies (biconcave, intermediate biconcave, intermediate polyhedrocyte, and polyhedrocyte) in the thrombi with scanning electron microscopy (n = 5) was used to determine degree of thrombus deposition/contraction. Very few biconcave RBCs (1.2 ± 0.6%) were in the thrombi, and greater amounts of intermediate biconcave RBCs (25.8 ± 6.7%) were located in the descending thoracic portion of the dissection while more polyhedrocytes (14.6 ± 5.1%) and fibrin (42.3 ± 4.5%; P < .05) were found in the distal suprarenal aorta. Thrombus deposition likely plays some role in patient outcomes, and this multimodality technique can help investigate thrombus deposition and characteristics in experimental animal models and human tissue samples.

Neurovascular Hypoxia Trajectories Assessed by Photoacoustic Imaging in a Murine Model of Cardiac Arrest and Resuscitation.

Cardiac arrest is a common cause of death annually mainly due to postcardiac arrest syndrome that leads to multiple organ global hypoxia and dysfunction after resuscitation. The ability to quantify vasculature changes and tissue oxygenation is crucial to adapt patient treatment in order to minimize major outcomes after resuscitation. For the first time, we applied high-resolution ultrasound associated with photoacoustic imaging (PAI) to track neurovascular oxygenation and cardiac function trajectories in a murine model of cardiac arrest and resuscitation. We report the preservation of brain oxygenation is greater compared to that in peripheral tissues during the arrest. Furthermore, distinct patterns of cerebral oxygen decay may relate to the support of vital brain functions. In addition, we followed trajectories of cerebral perfusion and cardiac function longitudinally after induced cardiac arrest and resuscitation. Volumetric cerebral oxygen saturation (sO2) decreased 24 h postarrest, but these levels rebounded at one week. However, systolic and diastolic cardiac dysfunction persisted throughout and correlated with cerebral hypoxia. Pathophysiologic biomarker trends, identified via cerebral PAI in preclinical models, could provide new insights into understanding the pathophysiology of cardiac arrest and resuscitation.

Quantification of murine myocardial infarct size using 2-D and 4-D high-frequency ultrasound.

Ischemic heart disease is the leading cause of death in the United States, Canada, and worldwide. Severe disease is characterized by coronary artery occlusion, loss of blood flow to the myocardium, and necrosis of tissue, with subsequent remodeling of the heart wall, including fibrotic scarring. The current study aims to demonstrate the efficacy of quantitating infarct size via two-dimensional (2-D) echocardiographic akinetic length and four-dimensional (4-D) echocardiographic infarct volume and surface area as in vivo analysis techniques. We further describe and evaluate a new surface area strain analysis technique for estimating myocardial infarction (MI) size after ischemic injury. Experimental MI was induced in mice via left coronary artery ligation. Ejection fraction and infarct size were measured through 2-D and 4-D echocardiography. Infarct size established via histology was compared with ultrasound-based metrics via linear regression analysis. Two-dimensional echocardiographic akinetic length (r = 0.76, P = 0.03), 4-D echocardiographic infarct volume (r = 0.85, P = 0.008), and surface area (r = 0.90, P = 0.002) correlate well with histology. Although both 2-D and 4-D echocardiography were reliable measurement techniques to assess infarct, 4-D analysis is superior in assessing asymmetry of the left ventricle and the infarct. Strain analysis performed on 4-D data also provides additional infarct sizing techniques, which correlate with histology (surface strain: r = 0.94, P < 0.001, transmural thickness: r = 0.76, P = 0.001). Two-dimensional echocardiographic akinetic length, 4-D echocardiography ultrasound, and strain provide effective in vivo methods for measuring fibrotic scarring after MI.NEW & NOTEWORTHY Our study supports that both 2-D and 4-D echocardiographic analysis techniques are reliable in quantifying infarct size though 4-D ultrasound provides a more holistic image of LV function and structure, especially after myocardial infarction. Furthermore, 4-D strain analysis correctly identifies infarct size and regional LV dysfunction after MI. Therefore, these techniques can improve functional insight into the impact of pharmacological interventions on the pathophysiology of cardiac disease.

Hemodynamic Assay of Hind Limb in Multiple Animal Models.

INTRODUCTION: Measuring hemodynamic characteristics of injured limbs is paramount to early identification of potentially damaging ischemic conditions, but can often prove difficult attributable to a multitude of factors. Here, we present an in vivo optical imaging technique to characterize pulsatile blood flow quality through the distal extremity in multiple animal models that replicate the signs of distal extremity ischemia. The purpose of this study is to examine the feasibility of the optical imaging technique and relevance to hemodynamic complications such as acute compartment syndrome (ACS) and nonobvious hemorrhage. MATERIALS AND METHODS: In one pig and six mice, three different methods were used to create ischemic conditions in the lower extremity, producing symptoms similar to what is observed in ACS. In each condition, perfusion to the distal extremity was measured with the hemodynamic detection device (HDD; Odin Technologies), an optical assessment tool for perfusion and blood flow quality. RESULTS: We observed a profound decrease in extremity perfusion immediately after onset of ischemia in all three models. In the porcine model, the HDD's measurements demonstrated similar characteristic flow between the various measurement locations. After the tourniquet was applied, the HDD revealed a 95% decrease in normalized perfusion value (npv) while the intracompartmental pressure rose from 5 to 52 mmHg (a 47mmHg increase). After the tourniquet was removed during reperfusion, the normalized blood flow returned to baseline and the intracompartmental pressure dropped from 20 to 6 mmHg in less than 5 minutes. For each mouse, the HDD test leg demonstrated a measurement of 0.97 npv before femoral ligation and 0.05 npv after femoral ligation, an 89% decrease (P < .01) in flow. Pulsed-wave Doppler ultrasound (PWDU) measurements on the test leg had pre-ligation measurement of 0.84 npv and a post-ligation measurement of 0.001 npv, a 99% decrease. These PWDU measurements revealed almost complete stoppage of blood flow during ischemia, followed by a substantial increase after the femoral artery ligation was removed. CONCLUSIONS: Here, we show that a novel, optics-based sensing system can be used to diagnose and assess ACS in animal models. This technology is comparable to other standards used to monitor ACS and nonobvious hemorrhage and may also be a plausible alternative to prolonged invasive monitoring of patients with sustained extremity trauma.

Use of an Integrated Low-Flow Anesthetic Vaporizer, Ventilator, and Physiological Monitoring System for Rodents.

Low-flow digital vaporizers commonly utilize a syringe pump to directly administer volatile anesthetics into a stream of carrier gas. Per animal welfare recommendations, animals are warmed and monitored during procedures requiring anesthesia. Common anesthesia and physiological monitoring equipment include gas tanks, anesthetic vaporizers and stands, warming controllers and pads, mechanical ventilators, and pulse oximeters. A computer is also necessary for data collection and to run equipment software. In smaller spaces or when performing field work, it can be challenging to configure all this equipment in limited space. The goal of this protocol is to demonstrate best practices for use of a low-flow digital vaporizer using both compressed oxygen and room air, along with an integrated mechanical ventilator, pulse oximeter, and far infrared warming as an all-inclusive anesthesia and physiological monitoring suite ideal for rodents.