Application Areas of Intermittent Pneumatic Compression in the Prevention of Deep Vein Thrombosis During Dixon Surgery: A Randomized, Controlled Trial.

PURPOSE: Deep vein thrombosis (DVT) is common in the lithotomy position after laparoscopic surgery. Intermittent pneumatic compression (IPC) plays an important role in DVT prevention. However, few studies have compared the different compression areas of IPC application. It was hypothesized that the location of the compression sleeves could have an impact on the effects of thromboprophylaxis. METHODS: In this randomized, controlled trial performed from August 2020 to March 2021, 164 patients scheduled to undergo laparoscopic Dixon surgery were randomly assigned to one of four groups, based on the bilateral placement of compression sleeves during surgery: feet, calves, thighs, or control (no IPC). Both lower extremities were monitored for DVT on days 1 and 7 after surgery, using ultrasonographic assessment of mean blood velocity, blood flow volume, and diameter of the common femoral veins. Thrombosis-related hematologic analysis was performed. FINDINGS: On day 1 after surgery, IPC of the feet or calves was associated with a reduced prevalence of DVT compared with controls (both: P = 0.024; OR = 0.09; 95% CI, 0.01-0.72), while IPC of the thighs had no significant benefit (P = 0.781; OR = 0.86; 95% CI, 0.29-2.55). The prevalence of DVT in the left extremity was lower with IPC of the feet and calves compared with controls (both, P = 0.048). The mean blood velocity in the common femoral vein was significantly increased after surgery with IPC of the left and right feet (P = 0.006 and 0.007, respectively) and calves (P = 0.011 and P = 0.026, respectively) compared with controls. Similarly, the volume of blood flow in the left common femoral vein was greater with IPC of the feet and calves (P = 0.03 and 0.027, respectively). However, on day 7 after surgery, the between-group differences in the prevalences of DVT and hematologic indicators of thrombosis were not significant. IMPLICATIONS: On day 1 after surgery, IPC application at the feet or calves facilitated venous return and, hence, reduced the prevalence of DVT, especially in the left extremities. However, there were no significant differences in the prevalences of DVT or thrombosis-related hematologic indicators among the four groups on the day 7 after surgery. Chinese Clinical Trial Registration identifier: ChiCTR2000035325.

Effect of dysmorphic plantar arch on venous hemodynamics of the lower limb.

BACKGROUND: The role of the plantar venous pump (PVP) on venous return is evident but the effects of the foot morphology have never been characterized properly. METHOD: 52 healthy volunteers-26 with normal plantar arch (control) and 26 with dysmorphic plantar arch (in two subgroups: 13 flat feet, 13 hollow feet)-were included. Using Doppler ultrasound, we measured the diameter and the peak systolic velocity in the large veins of the lower limb after PVP stimulation by manual compression and bodyweight transfer. RESULT: The mean peak systolic velocity of the studied veins varied from 12.2 cm/s to 41.7 cm/s in the control group and from 10.9 cm/s to 39.1 cm/s in the dysmorphic plantar group. The foot arch morphology did not affect significantly the venous blood flows, except in the great saphenous vein during manual compression. CONCLUSION: The plantar morphology did not induce a significant increase of venous blood velocity resulting from PVP stimulation.

Which Frequency of Ankle Pump Exercise Should Be Chosen for the Prophylaxis of Deep Vein Thrombosis?

INTRODUCTION: Ankle pump exercise (APE) is an effective method to prevent deep vein thrombosis (DVT) in the lower extremities. However, traditional APE at a frequency of 3 times/min applied in the clinic lacked high compliance, and individuals were found to prefer an APE of 30 times/min. This study aimed to compare the effects of APEs with the above two different frequencies on the venous hemodynamics and fatigue of lower extremities. METHODS: The study applied a randomized cross-over design, and 307 healthy adults were randomly assigned into two groups, whose left feet performed 5 minutes of traditional APE (3 times/min, after 10 minutes of rest) and 5 minutes of selected APE (30 times/min, after 10 minutes of rest) in different orders. The diameters and blood flow velocities of the external iliac vein, femoral vein, and popliteal vein of the left extremities were recorded with the color doppler ultrasound when participants were at rest and after 5 minutes of traditional or selected APE. The fatigue of lower extremities was assessed with the Rating of Perceived Exertion (RPE) after the participants performed 5 minutes of different APEs. RESULTS: After both traditional APE and selected APE, the diameters and blood flow (peak systolic) velocities of the external iliac vein, femoral vein, and popliteal vein increased significantly in the participants (P<.01), and the effects of the two APEs on venous hemodynamics of the lower extremities had no significant difference (P>.05). However, participants reported that traditional APE caused higher fatigue, and 252 (82.1%) participants preferred APE at 30 times/min. CONCLUSION: Both traditional and selected APE could increase venous blood flow in the lower extremity. Despite the equivalent effects, the selected APE of 30 times/min may cause less fatigue than the traditional one of 3 times/min.

Effects of different exercise methods of calf muscles on the hemodynamics of lower extremity vein.

OBJECTIVE: To compare the effects of active and passive calf muscle contraction on the hemodynamics of the lower extremity vein. METHODS: 30 females were selected by convenient sampling. The hemodynamic indexes of the common femoral vein were measured by Duplex ultrasound during the active ankle pump exercise, active circular exercise, passive ankle pump exercise, passive circular exercise, and massage the calf muscles. RESULTS: There was no significant difference in the velocity of common femoral vein when the subjects do active ankle pump exercise, active circular exercise, and massage the calf muscles (p > .05), but the velocity of common femoral vein was faster than that of passive ankle pump exercise and passive circular exercise (p < .01). CONCLUSION: The effects of active ankle exercise and massage on promoting venous blood return of lower extremity are better than that of passive ankle exercise.

Effects of intermittent pneumatic compression on femoral vein peak venous velocity during active ankle exercise.

INTRODUCTION: The risk of developing deep vein thrombosis (DVT) is high even after the period of bed rest following major general surgery including total joint arthroplasty (TJA). Mobile intermittent pneumatic compression (IPC) devices allow the application of IPC during postoperative exercise. Although ambulation included ankle movement, no reports have been made regarding the effects of IPC during exercise, including active ankle exercise (AAE), on venous flow. This study was performed to examine whether using a mobile IPC device can effectively augment the AAE-induced increase in peak velocity (PV). METHODS: PV was measured by Doppler ultrasonography in the superficial femoral vein at rest, during AAE alone, during IPC alone, and during AAE with IPC in 20 healthy subjects in the sitting position. PV in AAE with IPC was measured with a mobile IPC device during AAE in the strong compression phase. AAE was interrupted from the end of the strong compression phase to minimize lower limb fatigue. RESULTS: AAE with IPC (76.2 cm/s [95%CI, 69.0-83.4]) resulted in a significant increase in PV compared to either AAE or IPC alone (47.1 cm/s [95%CI, 38.7-55.6], p < 0.001 and 48.1 cm/s [95%CI, 43.7-52.4], p < 0.001, respectively). DISCUSSION: Reduced calf muscle pump activity due to the decline in ambulation ability reduced venous flow. Therefore, use of a mobile IPC device during postoperative rehabilitation in hospital and activity including self-training in an inpatient ward may promote venous flow compared to postoperative exercise without IPC. CONCLUSION: Use of a mobile IPC device significantly increased the PV during AAE, and simultaneous AAE with IPC could be useful evidence for the prevention of DVT in clinical settings, including after TJA.

Structural recirculation and refractory hypoxemia under femoro-jugular veno-venous extracorporeal membrane oxygenation.

The performance of each veno-venous extracorporeal membrane oxygenation (vv-ECMO) configuration is determined by the anatomic context and cannula position. A mathematical model was built considering bicaval specificities to simulate femoro-jugular configuration. The main parameters to define were cardiac output (QC ), blood flow in the superior vena cava (QSVC ), extracorporeal pump flow (QEC ), and pulmonary shunt (kS-PULM ). The obtained variables were extracorporeal flow ratio in the superior vena cava (EFRSVC  = QEC /[QEC  + QSVC ]), recirculation coefficient (R), effective extracorporeal pump flow (Qeff-EC  = [1 - R] × QEC ), Qeff-EC /QC ratio, and arterial blood oxygen saturation (SaO2 ). EFRSVC increased logarithmically when QEC increased. High QC or high QSVC /QC decreased EFRSVC (range, 68%-85% for QEC of 5 L/min). R also increased following a logarithmic shape when QEC increased. The R rise was earlier and higher for low QC and high QSVC /QC (range, 12%-49% for QEC of 5 L/min). The Qeff-EC /QC ratio (between 0 and 1) was equal to EFRSVC for moderate and high QEC . The Qeff-EC /QC ratio presented the same logarithmic profile when QEC increased, reaching a plateau (range, 0.67-0.91 for QEC /QC  = 1; range, 0.75-0.94 for QEC /QC  = 1.5). The Qeff-EC /QC ratio was linearly associated with SaO2 for a given pulmonary shunt. SaO2  < 90% was observed when the pulmonary shunt was high (Qeff-EC /QC  ≤ 0.7 with kS-PULM  = 0.7 or Qeff-EC /QC  ≤ 0.8 with kS-PULM  = 0.8). Femoro-jugular vv-ECMO generates a systematic structural recirculation that gradually increases with QEC . EFRSVC determines the Qeff-EC /QC ratio, and thereby oxygen delivery and the superior cava shunt. EFRSVC cannot exceed a limit value, explaining refractory hypoxemia in extreme situations.

An alternative explanation for the phasic variations in venous flow.

BACKGROUND: Phasic venous flow variation with respiration is surrounded by controversy and not well understood. The current concept assigns a major role to the "abdominal pump." According to this model, inspiratory increases in abdominal pressure compress the vena cava, increasing its internal venous pressure and propelling blood upstream. Some have assigned a secondary role to the "thoracic pump," with the negative intrapleural pressure aiding blood flow toward the heart. The aim of the present study was to examine the phasic changes in flow, pressure, and volume in the central veins and named tributaries. METHODS: Caliber area changes were measured using intravascular ultrasonography in 37 patients undergoing iliac vein stenting. The pressure was measured in 48 patients using transducer tip catheters with electronic zero calibration. Duplex ultrasound flow in the head and neck and truncal and limb veins during inspiration and expiration was measured in 15 normal volunteers. RESULTS: The caliber of the abdominal inferior vena cava had increased by 32% and its lateral pressure had decreased significantly during inspiration. Intravenous pressure in the central veins of the chest and right atrium was positive at 6 to 14 mm Hg. Negative pressures were rarely seen and then only transiently. The internal jugular vein displayed little phasic variation. The upper limb veins displayed weak inspiratory phasicity. Phase polarity was reversed in the lower limbs, with near flow stoppage during inspiration. CONCLUSIONS: These observations conflict with the current notions of venous flow phasicity, which are based on push-pull pressure changes in the abdominal and thoracic veins. The paradoxical inspiratory inferior vena cava caliber increase probably explains the concurrent pressure decrease. Sustained negative pressures in the thoracic central veins and right atrium did not occur. We have proposed an alternate hypothesis for venous flow phasicity based on alternate stretching and relaxation of the mobile section of the great veins with respiratory movement.

Comparison of global end-diastolic volume index derived from jugular and femoral indicator injection: a prospective observational study in patients equipped with both a PiCCO-2 and an EV-1000-device.

Transpulmonary thermodilution (TPTD)-derived global end-diastolic volume index (GEDVI) is a static marker of preload which better predicted volume responsiveness compared to filling pressures in several studies. GEDVI can be generated with at least two devices: PiCCO and EV-1000. Several studies showed that uncorrected indicator injection into a femoral central venous catheter (CVC) results in a significant overestimation of GEDVI by the PiCCO-device. Therefore, the most recent PiCCO-algorithm corrects for femoral indicator injection. However, there are no systematic data on the impact of femoral indicator injection for the EV-1000 device. Furthermore, the correction algorithm of the PiCCO is poorly validated. Therefore, we prospectively analyzed 14 datasets from 10 patients with TPTD-monitoring undergoing central venous catheter (CVC)- and arterial line exchange. PiCCO was replaced by EV-1000, femoral CVCs were replaced by jugular/subclavian CVCs and vice-versa. For PiCCO, jugular and femoral indicator injection derived GEDVI was comparable when the correct information about femoral catheter site was given (p = 0.251). By contrast, GEDVI derived from femoral indicator injection using the EV-1000 was obviously not corrected and was substantially higher than jugular GEDVI measured by the EV-1000 (846 ± 250 vs. 712 ± 227 ml/m2; p = 0.001). Furthermore, measurements of GEDVI were not comparable between PiCCO and EV-1000 even in case of jugular indicator injection (p = 0.003). This is most probably due to different indexations of the raw value GEDV. EV-1000 could not be recommended to measure GEDVI in case of a femoral CVC. Furthermore, different indexations used by EV-1000 and PiCCO should be considered even in case of a jugular CVC when comparing GEDVI derived from PiCCO and EV-1000.

Initiation of reticular and spider veins, incompetent perforantes and varicose veins in the saphenous vein network of the rat.

In an attempt to induce experimental varicosity, reverse perforant vein development was initiated in the rat leg by applying a chronic (14 and 32 weeks) partial stricture on the main branch of the deep femoral vein. At surfacing of the incompetent perforantes, typical reticular vein plaques and spider veins were identified by video-microscopy and quantitative histology. Deep vein blood was channeled by them into the saphenous vein system, the extra flow deforming these vessels, causing local dilations and broken course, even undulations of larger branches.

Ischemic Preconditioning Improves Microvascular Endothelial Function in Remote Vasculature by Enhanced Prostacyclin Production.

BACKGROUND The mechanisms underlying the effect of preconditioning on remote microvasculature remains undisclosed. The primary objective was to document the remote effect of ischemic preconditioning on microvascular function in humans. The secondary objective was to test if exercise also induces remote microvascular effects. METHODS AND RESULTS A total of 12 healthy young men and women participated in 2 experimental days in a random counterbalanced order. On one day the participants underwent 4×5 minutes of forearm ischemic preconditioning, and on the other day they completed 4×5 minutes of hand-grip exercise. On both days, catheters were placed in the brachial and femoral artery and vein for infusion of acetylcholine, sodium nitroprusside, and epoprostenol. Vascular conductance was calculated from blood flow measurements with ultrasound Doppler and arterial and venous blood pressures. Ischemic preconditioning enhanced (P<0.05) the remote vasodilator response to intra-arterial acetylcholine in the leg at 5 and 90 minutes after application. The enhanced response was associated with a 6-fold increase (P<0.05) in femoral venous plasma prostacyclin levels and with a transient increase (P<0.05) in arterial plasma levels of brain-derived neurotrophic factor and vascular endothelial growth factor. In contrast, hand-grip exercise did not influence remote microvascular function. CONCLUSIONS These findings demonstrate that ischemic preconditioning of the forearm improves remote microvascular endothelial function and suggest that one of the underlying mechanisms is a humoral-mediated potentiation of prostacyclin formation.

Vein Graft Interposition: A Training Model Using Gradually Thawed Cryopreserved Vessels.

INTRODUCTION: Microsurgical interposition of vein grafts is an extraordinarily filigree surgical technique, which requires both sound theoretical knowledge and solid manual skills. Although there are a large number of training models, the majority of these are either relatively expensive, technically complex, or employ synthetic materials with poor resemblance to human tissue. The authors' model allows training of ex vivo vein graft interposition on gradually thawed cryopreserved vessels and it, therefore, is cost-efficient and readily available when needed. Furthermore, it respects the 3R-principle (Reduce-Refine-Replace), as it is based on rat cadaveric vessels. METHODS: Three trainees with basic microsurgical experience, but without prior performance of vein graft interpositioning, were chosen to perform 20 femoral vein graft (5 mm) interpositions into femoral artery defects. The patency and leakage rate served as qualitative variable and operation time as a quantitative variable for efficiency control. RESULTS: For the first half of trials, the trainees had a patency failure rate of 50% and for the second half a rate of 13.3%. The leakage rate noticeably decreased from 44.4% in the first half of trials to 10% in the second half. Although the trainees needed 60 minutes on average for their first 10 trials, they improved to 51 minutes for their last 10 anastomoses. CONCLUSION: The authors' microsurgical model offers a simple, low-cost simulation training, specifically designed for learning of vein graft interposition into arterial defects. The model is associated with a high learning curve, based on an objective control of the anastomoses by assessment of the patency, leakage, and operation time.

Breast Reconstruction with Free Abdominal Flaps Is Associated with Persistent Lower Extremity Venous Stasis.

BACKGROUND: Previous work has demonstrated the occurrence of lower extremity venous stasis in the early postoperative period after breast reconstruction with free abdominal flaps. The authors investigated whether venous stasis persisted through the day of discharge, thus potentially exposing patients to an elevated risk of venous thromboembolism following discharge. METHODS: Patients who underwent breast reconstruction with free abdominal flaps were enrolled prospectively and underwent duplex ultrasound of the common femoral vein at the following time points: preoperatively, postoperative day 1, and day of discharge. Parameters of interest included common femoral vein diameter, area, and maximum flow velocity. RESULTS: Thirty patients with a mean age of 50.3 years (range, 29 to 70 years) underwent breast reconstruction with 52 free abdominal flaps. A significant increase in common femoral vein diameter (19.1 percent; p < 0.01) and area (46.8 percent; p < 0.01) correlated with a significant reduction in maximum flow velocity (-10.9 percent; p = 0.03) between baseline and postoperative day 1. These changes persisted through the day of discharge [common femoral vein diameter, 17.8 percent (p < 0.01); area, 46 percent (p < 0.01); and maximum flow velocity, -11.3 percent (p = 0.01)]. Venous parameters were not influenced by unilateral versus bilateral flap harvest (p = 0.48). CONCLUSIONS: Postoperative lower extremity venous stasis following autologous breast reconstruction with free abdominal flaps seems to persist through the day of discharge. This finding may explain why patients remain at risk for venous thromboembolism after discharge. Although the authors' findings are at odds with current venous thromboembolism prophylaxis recommendations, additional studies are indicated to examine whether these findings translate into venous thromboembolism events. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Suspension syndrome: a potentially fatal vagally mediated circulatory collapse-an experimental randomized crossover trial.

PURPOSE: Suspension syndrome describes a potentially life-threatening event during passive suspension on a rope. The pathophysiological mechanism is not fully understood and optimal treatment unknown. We aimed to elucidate the pathophysiology and to give treatment recommendations. METHODS: In this experimental, randomized crossover trial, 20 healthy volunteers were suspended in a sit harness for a maximum of 60 min, with and without prior climbing. Venous pooling was assessed by measuring the diameter of the superficial femoral vein (SFV), lower leg tissue oxygenation (StO2) and by determining localized bioelectrical impedance. Hemodynamic response was assessed by measuring heart rate, blood pressure, stroke volume, and left ventricular diameters. Signs and symptoms of pre-syncope were recorded. RESULTS: Twelve (30%) out of 40 tests were prematurely terminated due to pre-syncopal symptoms (mean 44.7 min, minimum 13.4, maximum 59.7). SFV diameter increased, StO2 and the capacitive resistance of the cells decreased indicating venous pooling. Heart rate and blood pressure did not change in participants without pre-syncope. In contrast, in participants experiencing pre-syncope, heart rate and blood pressure dropped immediately before the event. All symptoms dissolved and values returned to normal within 5 min with participants in a supine position. CONCLUSIONS: Sudden pre-syncope during passive suspension in a harness was observed in 30% of the tests. Blood pools in the veins of the lower legs; however, a vagal mechanism finally leads to loss of consciousness. Time to pre-syncope is unpredictable and persons suspended on a rope should be rescued and put into a supine position as soon as possible.

Changes in trunk veins of the lower limbs in women with premenstrual leg heaviness and swelling.

BACKGROUND: The aim of this study was to investigate vein changes during the menstrual cycle in parous women with premenstrual leg heaviness. METHODS: А total of 39 women with heavy legs before menstruation were examined. Great saphenous vein (GSV) in the groin, femoral vein (FV) and popliteal vein (PV) were examined with ultrasound scanning before 10 a.m. and after 6 p.m. on days 1 to 4 (menstrual phase) and 25 to 28 (secretory phase). To characterize biophysical features of veins we used: 1) interphase gradient of the diameter (IGd), i.e. the difference in vein diameters during the secretory and menstrual phases; 2) orthostatic gradient of the diameter (OGd), i.e. the difference in vein diameters measured in the evening and in the morning. RESULTS: Diameter changings for GSV, FV and PV were similar. GSV diameter increased from the morning during the menstrual phase to the evening during the secretory phase on average by 26.2%. OGd was 0.73 mm (95% CI: 0.59-0.87) during the menstrual phase and 0.62 mm (95% CI: 0.54-0.71) during the secretory phase. IGd was 0.73 mm (95% CI: 0.61-0.86) already in the morning. During the secretory phase 43.6% patients had the GSV reflux. During the whole menstrual cycle GSV diameter in the reflux zone increased on average by 40.6%. IGd of GSV in this zone reached 1.25 mm (95% CI: 1.02-1.48) in the morning and 1.30 mm (95% CI: 1.25-1.35) in the evening. CONCLUSIONS: Women with premenstrual leg heaviness have a minimal vein diameter in the morning during the secretory phase. The maximal diameter is revealed in the evening during the secretory phase. Clinically manifested expansion of veins, including GSV refluxes, is found during the secretory phase due to increased expansibility of veins. However, because of increased creeping ability one observes expansion of veins during the whole menstrual cycle in these women.

Factors related to the size of venous leg ulcers: A cross-sectional study.

Venous leg ulcers (VLUs) are an important health problem, and the size of ulcers often affects patient care, healing time, and quality of life. However, the risk factors associated with ulcer size have been rarely reported. The aim of this study was to establish the risk factors for the size of venous ulceration by analyzing the patient demographics and the results of duplex ultrasonography.This study was an in-patient population-based cross-sectional study conducted at a single center during the period from 2013 to 2017. Men and women aged >18 years, who consecutively presented to our hospital with VLU, were included. According to the size of the ulcer, patients were divided into two groups, those with ulcers≤2 cm and those with ulcers >2 cm. Demographic, anthropometric, and clinical data were collected. For the analysis, univariate and multivariate logistic regressions were used.A total of 232 patients with VLUs were admitted to our hospital from 2013 to 2017, including 117 patients (50.4%) with ulcer diameters ≤2 cm and 115 patients (49.6%) with ulcer diameters >2 cm. According to the results of the multivariate analysis, the ulcer duration (P = .001), the diameter of perforating veins (PVs) around the ulcers (P = .025), the reflux time of common femoral veins (CFVs) (P = .013), the reflux time of great saphenous veins (GSVs) (P = .021), and the reflux time of PVs around the ulcers (P = .001) were independent risk factors for VLUs.These findings provide evidence that the size of VLU was significantly related to the ulcer duration, the diameter of PV around the ulcers, the CFV reflux time, the GSV reflux time, and the PV reflux time.

Novel rodent model for simulation of sylvian fissure dissection and cerebrovascular bypass under subarachnoid hemorrhage conditions: technical note and timing study.

OBJECTIVESylvian fissure dissection following subarachnoid hemorrhage (SAH) is a challenging but fundamental skill in microneurosurgery, and one that has become increasingly difficult to develop during residency, given the overarching management trends. The authors describe a novel rodent model for simulation of sylvian fissure dissection and cerebrovascular bypass under SAH conditions.METHODSA standardized microvascular anastomosis model comprising rat femoral arteries and veins was used for the experimental framework. In the experimental protocol, following exposure and skeletonization of the vessels, extensive, superficial (1- to 2-mm) soft-tissue debridement was conducted and followed by wound closure and delayed reexploration at intervals of 7, 14, and 28 days. Two residents dissected 1 rat each per time point (n = 6 rats), completing vessel skeletonization followed by end-to-end artery/vein anastomoses. Videos were reviewed postprocedure to assess scar score and relative difficulty of dissection by blinded raters using 4-point Likert scales.RESULTSAt all time points, vessels were markedly invested in friable scar, and exposure was subjectively assessed as a reasonable surrogate for sylvian fissure dissection under SAH conditions. Scar score and relative difficulty of dissection both indicated 14 days as the most challenging time point.CONCLUSIONSThe authors' experimental model of femoral vessel skeletonization, circumferential superficial soft-tissue injury, and delayed reexploration provides a novel approximation of sylvian fissure dissection and cerebrovascular bypass under SAH conditions. The optimal reexploration interval appears to be 7-14 days. To the authors' knowledge, this is the first model of SAH simulation for microsurgical training, particularly in a live animal system.

Cross-sectional areas of deep/core veins are smaller at lower core body temperatures.

The cardiovascular system plays a crucial role in thermoregulation. Deep core veins, due to their large size and role in returning blood to the heart, are an important part of this system. The response of veins to increasing core temperature has not been adequately studied in vivo. Our objective was to noninvasively quantify in C57BL/6 mice the response of artery-vein pairs to increases in body temperature. Adult male mice were anesthetized and underwent magnetic resonance imaging. Data were acquired from three colocalized vessel pairs (the neck [carotid/jugular], torso [aorta/inferior vena cava (IVC)], periphery [femoral artery/vein]) at core temperatures of 35, 36, 37, and 38°C. Cross-sectional area increased with increasing temperature for all vessels, excluding the carotid. Average area of the jugular, aorta, femoral artery, and vein linearly increased with temperature (0.10, 0.017, 0.017, and 0.027 mm2 /°C, respectively; P < 0.05). On average, the IVC has the largest venous response for area (18.2%/°C, vs. jugular 9.0 and femoral 10.9%/°C). Increases in core temperature from 35 to 38 °C resulted in an increase in contact length between the aorta/IVC of 29.3% (P = 0.007) and between the femoral artery/vein of 28.0% (P = 0.03). Previously unidentified increases in the IVC area due to increasing core temperature are biologically important because they may affect conductive and convective heat transfer. Vascular response to temperature varied based on location and vessel type. Leveraging noninvasive methodology to quantify vascular responses to temperature could be combined with bioheat modeling to improve understanding of thermoregulation.

Biomechanical properties of veins cultured in vitro under elevated internal pressure.

BACKGROUND: The venous response to elevated blood pressure (BP) is of major importance because it is closely related to the etiology of venous diseases and the competency of vein grafts. In vitro culture experiments may provide useful information on the function of vein grafts because it is easier to separate mechanical and hemodynamic effects from other systemic influences compared to in vivo experiments. OBJECTIVE: To study the effects of BP elevation on wall dimensions and mechanical properties of in vitro cultured veins. METHODS: Rabbit femoral veins were cultured in vitro under internal pressures of 1 to 50 mmHg for 1 week, and their wall dimensions, biomechanical properties, and histology were determined. RESULTS: No significant differences were observed in internal vein diameter and wall thickness among vessels cultured at 10-50 mmHg compared to non-cultured control vessels. For an internal pressure of 10 mmHg applied to vessels during culture (equivalent to in vivo working BP), wall circumferential stress was maintained within control levels. There were no significant effects of pressure on basal tone and contractility of vascular smooth muscle and vascular compliance. CONCLUSIONS: The in vitro results were essentially similar to those obtained from previous in vivo animal experiments, indicating that in vitro tissue culture techniques are applicable to studies of venous remodeling.

Novel Compliant Scaffold with Specific Design for Venous System: Results of a Porcine Model Study.

BACKGROUND: Stenting has become the first-line treatment of obstructive venous disease because of poor results of balloon angioplasty. This preclinical study aimed to investigate the safety and efficacy profile of a novel compliant venous scaffold (CVS) denominated Petalo CVS, specifically designed for venous diseases. MATERIALS AND METHODS: Twelve healthy pigs weighing 90 kg were used to test Petalo CVS. The devices were implanted into the internal jugular veins (IJVs) using a femoral vein percutaneous approach. The safety profile including the success rate of device releasing, anchoring, and positioning was evaluated immediately. Fracture, migration, primary patency, and endothelial response were assessed at 1, 2, 3, and 6 months after the study procedure. RESULTS: A total of 32 devices were successfully released in both IJVs. No procedure- or device-related complications were reported, and all pigs successfully completed the different scheduled follow-up periods. The primary patency rate was 100%, and no fracture or migration of the device into the brachiocephalic trunk was reported. Histological examination revealed only minimal lesions with minimal or absent inflammatory reaction surrounding the incorporated metallic rods. CONCLUSIONS: This porcine model study showed a promising safety and efficacy profile of Petalo CVS, a novel endovenous device based on specific concepts.