Emergency Department Thoracotomy: A Cost-Effective Model for Simulation Training.

BACKGROUND: Simulation provides a safe learning environment where high-stakes, low-frequency procedures can be practiced without the fear of being unsuccessful or causing harm. Emergency department thoracotomy (EDT) is one such procedure. Realistic thoracotomy models are expensive and not readily available. OBJECTIVE: Our objective is to describe a cost-effective, realistic, reproducible, and reusable thoracotomy model for simulation training. METHODS: We modified a commercially available clothes mannequin torso to expose the chest and abdominal cavity. A plastic skeleton composed of a spinal cord and ribs was placed inside the torso. Tubing was used to simulate the aorta and esophagus; both tubes were secured to the distal spine with zip ties. Commercially available lungs and heart were placed inside the chest cavity. A small rubber ball simulated the left lung to be able to maneuver the lung. The heart was covered with plastic wrap to simulate the pericardium. Thick tape was used to simulate the pleural cavity. Yoga mats were used to simulate the intercostal muscles, subcutaneous tissue, and skin. RESULTS: This model was tested with Emergency Medicine (EM) residents during a simulation session. A voluntary survey was available for residents to provide feedback. Survey results confirmed that the model provided valuable education, with overall positive feedback. CONCLUSION: This EDT model provides a valuable teaching opportunity to EM residents who otherwise might not have the opportunity to perform this procedure. Residents agreed that the model improved their confidence and is an effective method in providing the opportunity to practice this low-frequency, high-stakes procedure.

The effect of air exposure on leucocyte and cytokine activation in an in-vitro model of cardiotomy suction.

INTRODUCTION: Cardiopulmonary bypass (CPB) is known to cause a systemic inflammatory and immune response. OBJECTIVE: An in-vitro model of cardiotomy suction was designed to quantify the effects of incrementally increased air-blood exposure on leucocyte marker CD11b and cytokine activation in two common anticoagulants, heparin and citrate. METHODS: Fresh human blood was exposed to increasing amounts of air flow for ten minutes. Leucocyte and cytokine levels were measured prior to and after ten minutes of air flow. Cytokine levels were also measured after air exposure when incubated for 24 hours at 37oC. RESULTS: Leucocyte activation, measured by CD11b, was elevated between baseline and air flow rates up to 50 mL/min. After 10 minutes of air exposure, no measured cytokine levels were elevated. After 24 hours of incubation, cytokine levels of TNFα, IL-10, IL-6, and IL-8 were elevated. However, only IL-8 was significantly elevated in citrated blood, but not in heparinized blood, when compared to baseline samples that were also incubated for 24 hours. CONCLUSION: This study investigates CD11b levels in response to an air stimulus in blood that was anticoagulated with citrate or heparin. Exposure to an air stimulus activates leucocytes. Activation of CD11b was less when using heparin as an anticoagulant compared to citrate. Cytokine activation occurs with air stimulation, but levels do not immediately rise, indicating that time is required to generate free cytokines.

The Effect of Ex Situ Perfusion in a Swine Limb Vascularized Composite Tissue Allograft on Survival up to 24 Hours.

PURPOSE: To test the potential for the ex situ limb perfusion system to prolong limb allograft survival up to 24 hours. METHODS: We used 20 swine for the study. In group 1 (control), 4 limbs were perfused with heparin solution and preserved at 4°C for 6 hours. In group 2, 4 limbs were perfused with autologous blood at 27°C to 32°C for 24 hours. In both groups, limbs were transplanted orthotopically to recipients and monitored for 12 hours. In addition to perfusion parameters, we recorded perfusate gases and electrolytes (pH, pCO2, pO2, O2 saturation, Na, K, Cl, Ca, HCO3, glucose, and lactate) and obtained functional electrostimulation hourly throughout the experiment. Histology samples were obtained for TUNEL staining and single-muscle fiber contractility testing. RESULTS: In both groups, hemodynamic variables of circulation remained stable throughout the experiment. Neuromuscular electrical stimulation remained intact until the end of reperfusion in group 2 vs no response in group 1. In group 2, a gradual increase in lactate levels during pump perfusion returned to normal after transplantation. Compared with the contralateral limb in group 2, single-muscle fiber contractility testing showed no significant difference at the end of the experiment. CONCLUSIONS: We demonstrated extended limb survival up to 24 hours using normothermic pulsatile perfusion and autologous blood. CLINICAL RELEVANCE: Successful prolongation of limb survival using ex situ perfusion methods provides with more time for revascularization of an extremity.

Haemodynamic and renal sympathetic responses to V1b vasopressin receptor activation within the paraventricular nucleus.

NEW FINDINGS: What is the central question of this study? Does antagonism of V1b receptors prevent the haemodynamic and renal sympathetic nerve responses that occur with application of exogenous vasopressin into the paraventricular nucleus (PVN) of conscious, chronically instrumented rats? What is the main finding and its importance? Microinjection of vasopressin into the PVN increased mean arterial pressure, heart rate and renal sympathetic nerve activity, all of which were inhibited by pre-injection of the PVN with the V1b antagonist, nelivaptan. The administered vasopressin did not enter the peripheral circulation or increase plasma vasopressin. Ganglionic blockade prevented each of the responses, consistent with mediation by enhanced sympathetic output rather than an increase in circulating vasopressin. Vasopressin (VP) participates in regulation of haemodynamics and volume. Besides more classical actions as a circulating hormone, VP may act via release from axons and dendrites within the CNS. The paraventricular nucleus (PVN) possesses vasopressinergic neurons and a dense complement of VP receptors, including the V1b receptor, which has been implicated in several types of stress responses. We tested the hypothesis that antagonism of V1b receptors will prevent VP-induced increases in mean arterial pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA). Studies were performed in conscious male Sprague-Dawley rats chronically instrumented with vascular catheters, renal nerve electrodes and a cannula stereotaxically directed into the PVN. Unilateral microinjection of VP into the PVN significantly increased MAP, HR and RSNA, peaking at 10 min. Pre-injection of the PVN with the selective V1b receptor antagonist, nelivaptan, did not alter baseline values but blocked the responses to VP. Ganglionic blockade with chlorisondamine decreased MAP and HR and abolished their increase in response to subsequent PVN application of VP. Injection of VP into the PVN did not alter plasma VP levels. Paraventricular nucleus injection with radiolabelled VP resulted in negligible radiolabelled VP in peripheral blood. These findings support the concept that, in basal conditions, PVN V1b receptor activation (rather than VP release into the periphery) may be implicated in the increases in MAP, HR and RSNA due to increased sympathetic outflow. While the role of V1a and oxytocin receptors cannot be excluded, these data suggest that further studies of the role of V1b receptor activation by endogenous VP during stress to effect neuroexcitation are warranted.

The diagnostic yield for computed tomography pulmonary angiography in patients with anticoagulation.

BACKGROUND: Patients who present to the emergency department (ED) for suspected pulmonary embolism (PE) are often on active oral anticoagulation (AC). However, the diagnostic yield of computed tomography pulmonary angiography (CTPA) in screening for PE in patients who present on AC has not been well characterized. We aim to investigate the diagnostic yield of CTPA in diagnosing PE depending on AC status. METHODS: We reviewed and analyzed the electronic medical records of patients who underwent CTPA for PE at a university hospital ED from June 1, 2019, to March 25, 2022. Primary outcome was the incidence of PE on CTPA depending on baseline AC status and indication for AC. RESULTS: Of 2,846 patients, 242 were on AC for a history of venous thromboembolism (VTE), 210 were on AC for other indications, and 2,394 were not on AC. The incidence of PE on CTPA was significantly lower in patients on AC for other indications (5.7%) when compared to patients on AC for prior VTE (24.3%) and patients not on AC at presentation (9.8%) (P<0.001). In multivariable analysis among the whole cohort, AC was associated with a positive CTPA (odds ratio [OR] 0.26, 95% confidence interval [CI]: 0.15-0.45, P<0.001). CONCLUSION: The incidence of PE among patients undergoing CTPA in the ED is lower in patients previously on AC for indications other than VTE when compared to those not on AC or those on AC for history of VTE. AC status and indication for AC may affect pre-test probability of a positive CTPA, and AC status therefore warrants consideration as part of future diagnostic algorithms among patients with suspected PE.

An Inexpensive Conceptual Training Model for Transvenous Pacemaker Placement.

INTRODUCTION: Emergent transvenous (TV) pacemaker placement can be life-saving, but it has associated complications. Emergency medicine (EM) educators must be able to teach this infrequent procedure to trainees. METHODS: We constructed a conceptually-focused, inexpensive training model made from polyvinyl chloride pipes and connectors, vinyl tubing, and a submersible pump. Cost of the model was $51. We tested the model with a group of 15 EM residents. We then asked participants to complete a survey reporting confidence with the procedure before and after the session. Confidence was compared using a Wilcoxon matched-pairs test. RESULTS: Confidence improved after the session, with a median confidence before the session of 2 (minimally confident; interquartile range [IQR] 1-3) and a median confidence after the session of 4 (very confident; IQR 3-4, p=0.001). All residents agreed that the model helped them to understand the process of placing a TV pacemaker. CONCLUSION: Our TV pacemaker placement model was inexpensive and allowed for practice of a complex emergency procedure with direct visualization. It improved trainee confidence.

Ex Situ Limb Perfusion System to Extend Vascularized Composite Tissue Allograft Survival in Swine.

BACKGROUND: Organ perfusion systems have successfully been applied in solid organ transplantations. Their use in limb transplantation and replantation has not been widely investigated. In this study, we tested the potential for ex situ perfusion system to prolong limb allograft viability in a swine forelimb amputation/replantation model. METHODS: Fourteen swine were used. In group 1 (n = 4), we perfused 4 amputated limbs for 12 hours using warm (27 °C-32 °C) autologous blood. Group 2 (n = 3) served as a cold preservation control group, preserving limbs for 6 hours at 4 °C. All limbs were transplanted into healthy swine (n = 7) and observed for another 12 hours. Hemodynamic variables of circulation, as well as perfusate gases and electrolytes (pH, pCO2, pO2, O2 saturation, Na(+), K(+), Cl(-), Ca(2+), HCO3(-), glucose, lactate) were measured. Muscle samples were used to measure single-muscle fiber contractility. RESULTS: In the control group, no microcirculation was observed after 6 hours of cold storage. In the pump perfusion group, all limbs displayed a gradual increase in lactate levels (P < 0.05) during ex situ perfusion that returned to normal after transplantation and reperfusion (P = 0.05). The pH and potassium remained stable throughout the experiment. Single-muscle fiber contractility testing showed near normal contractility at the end of the reperfusion period (P > 0.05). Limb weight did not increase significantly between the end of pump perfusion and reperfusion (P > 0.05). CONCLUSIONS: We demonstrated the potential to preserve limb allograft using ex vivo circulation. This approach promises to extend the narrow time frame for revascularization of procured extremities in limb transplantation.

Effect of air exposure and suction on blood cell activation and hemolysis in an in vitro cardiotomy suction model.

Cardiopulmonary bypass (CPB) elicits a systemic inflammatory response. The cause may include surface-induced leukocyte activation and hemolysis. A study was designed to describe the effects of both suction and an air-blood interface independently and in combination on leukocyte and platelet activation, and hemolysis in an in vitro model. Fresh human blood was drawn and tested in four different conditions including control (A), 10 minutes of -600 mm Hg suction (B), 10 minutes of blood exposure to room air at 100 ml/min (C), and 10 minutes of simultaneous suction and air flow (D). Samples were analyzed by flow cytometry (platelets and leukocytes) and plasma-free hemoglobin (PFHb). Leukocyte CD11b expression and platelet P-selectin (CD62P) were analyzed by flow cytometry. In comparison with baseline, granulocytes were significantly activated by air (group C, p = 0.0029) and combination (group D, p = 0.0123) but not by suction alone (group B). Monocytes and platelets were not significantly activated in any group. The PFHb increased significantly in group C (p < 0.001) and group D (p < 0.001). This study suggests that the inflammatory response and associated hemolysis during CPB may be related to air exposure, which could be reduced by minimizing the air exposure of air to blood during cardiotomy suction.