The influence of inflation rate on the hematologic and hemodynamic effects of intermittent pneumatic calf compression for deep vein thrombosis prophylaxis

Hemodynamics in nutcracker syndrome: implications for diagnosis

BACKGROUND

Nutcracker syndrome is a disease characterized by complex symptoms, making its diagnosis challenging and often delayed, often resulting in a painful experience for the patients.

OBJECTIVE

This study aimed to investigate the pathogenesis of nutcracker syndrome through the perspective of hemodynamics by simulating blood flow with varying compression degrees of the left renal vein.

METHODS

3D patient-specific vascular models of the abdominal aorta, superior mesenteric artery and left renal vein were constructed based on CT images of patients suspected of having nutcracker syndrome. A hemodynamic simulation was then conducted using computational fluid dynamics to identify the correlation between alterations in hemodynamic parameters and varying degrees of compression.

RESULTS

The study indicated the presence of an evident gradient in velocity distribution over the left renal vein with relatively high degrees of stenosis (α ≤ 50°), with maximum velocity in the central region of the stenosis. Additionally, when the compression degree of the left renal vein increases, the pressure distribution of the left renal vein presents an increasing number of gradient layers. Furthermore, the wall shear stress shows a correlation with the variation of blood flow velocity, i.e., the increase of wall shear stress correlates with the acceleration of the blood flow velocity.

CONCLUSIONS

Using computational fluid dynamics as a non-invasive instrument to obtain the hemodynamic characteristics of nutcracker syndrome is feasible and could provide insights into the pathological mechanisms of the nutcracker syndrome supporting clinicians in diagnosis.

The FACT : Use of a novel intermittent pneumatic compression device to promote pre-surgery arm vein dilation in patients with chronic renal failure

BACKGROUND

Arteriovenous fistula (AVF) creation and maturation for hemodialysis is globally a topic of importance given the poor results and high costs associated with renal care. Successful AVF (surgical or endovascular) creation requires appropriate superficial veins and quality arteries. Many procedures fail due to initial small veins with limited blood flow capacity and distensibility. Intermittent pneumatic compression has previously shown success in trials to increase superficial veins in patients with end stage renal disease post AVF. The objective of this study is to investigate the role of an intermittent pneumatic device, the Fist Assist®, to dilate cephalic arm veins in patients with advanced chronic kidney disease (CKD) prior to AVF placement.

METHODS

Three centers enrolled subjects from June 2019 through July 2021. Baseline Doppler measurements of the cephalic vein in standard locations the forearm and upper arm with and without a blood pressure cuff were recorded. Patients were instructed and used Fist Assist® on their non-dominant arm for up to 4 h daily for 90 days. At approximately 3 months, Doppler measurements were repeated. The primary endpoint was cephalic vein enlargement with secondary endpoints based on percentage of veins approaching 2.5 mm in the forearm and 3.5 mm in the upper arm.

RESULTS

Thirty-seven subjects with CKD (mean eGFR 13.8 mL/min) were enrolled and completed the trial. Paired-difference t-tests (one tail) for aggregate data showed significant venous dilation of the cephalic vein in both the forearm and upper arm after use with the Fist Assist® (p < 0.05). Mean differences in the forearm veins were approximately 0.6 and 1.1 mm in the upper arm cephalic vein after Fist Assist® application. There were no major complications reported by any subject during the trial.

CONCLUSIONS

Fist Assist® use in patients with CKD is effective to enhance vein dilation. Forearm and upper arm cephalic veins increased on average 0.6 and 1.1 mm respectively after Fist Assist® application. This is the first trial to evaluate the effect of intermittent, focal pneumatic compression on pre-surgery vein diameter in patients with advanced CKD before AVF creation.

Can Intermittent Pneumatic Compression Reduce the Incidence of Venous Thrombosis in Critically Ill Patients: A Systematic Review and Meta-Analysis

Venous thromboembolism (VTE) is a common complication for critically ill patients. Intermittent pneumatic compression (IPC) is recommended for patients with high risk of bleeding. We aim to evaluate the effectiveness of IPC for thromboprophylaxis in critically ill patients. We searched PubMed, Embase, and ClinicalTrials for randomized controlled trials (RCTs) and observational studies that evaluated IPC in critically ill patients. RevMan 5.3 software was used for the meta-analysis. A total of 10 studies were included. The IPC group significantly reduced the VTE incidence compared with no thromboprophylaxis group (risk ratio [RR]: 0.35, confidence interval [CI]: 0.18-0.68, P = .002) and the IPC group also showed lower VTE incidence than the graduated compression stockings (GCS) group (RR: 0.47, CI: 0.24-0.91, P = .03). There were no significant differences between using IPC and low-molecular-weight heparin (LMWH) for VTE incidence (RR: 1.26, CI: 0.72-2.22, P = .41), but LMWH showed significantly more bleeding events. Intermittent pneumatic compression as an adjunctive treatment did not further reduce VTE incidence (RR: 0.55, CI: 0.24-1.27, P = .16). Intermittent pneumatic compression can reduce the incidence of VTE for critically ill patients, which is better than GCS and similar to LMWH, but it has no significant advantage as an adjunct therapy for thromboprophylaxis.

Intermittent Calf Compression Delays the Onset of Presyncope in Young Healthy Individuals

Orthostatic fluid shifts reduce the effective circulating volume and thus contribute to syncope susceptibility. Recurrent syncope has a devastating impact on quality of life and is challenging to manage effectively. To blunt orthostatic fluid shifts, static calf compression garments are often prescribed to patients with syncope, but have questionable efficacy. Intermittent calf compression, which mimics the skeletal muscle pump to minimize pooling and filtration, holds promise for the management of syncope. We aimed to evaluate the effectiveness of intermittent calf compression for increasing orthostatic tolerance (OT; time to presyncope). We conducted a randomized single-blind crossover study, in which participants (n = 21) underwent three graded 60° head-up-tilt tests to presyncope with combined lower body negative pressure on separate days. Low frequency intermittent calf compression (ICLF; 4 s on and 11 s off) at 0-30 and 0-60 mmHg was applied during two tests and compared to a placebo condition where the garment was fitted, but no compression applied. We measured continuous leg circumference changes (strain gauge plethysmography), cardiovascular responses (finger plethysmography; Finometer Pro), end tidal gases (nasal cannula), and cerebral blood flow velocity (CBFv, transcranial Doppler). The 0-60 mmHg ICLF increased OT (33 ± 2.2 min) compared to both placebo (26 ± 2.4 min; p < 0.001) and 0-30 mmHg ICLF (25 ± 2.7 min; p < 0.001). Throughout testing 0-60 mmHg ICLF reduced orthostatic fluid shifts compared to both placebo and 0-30 mmHg ICLF (p < 0.001), with an associated improvement in stroke volume (p < 0.001), allowing blood pressure to be maintained at a reduced heart rate (p < 0.001). In addition, CBFv was higher with 0-60 mmHg ICLF than 0-30 mmHg ICLF and placebo (p < 0.001). Intermittent calf compression is a promising novel intervention for the management of orthostatic intolerance, which may provide affected individuals renewed independence and improved quality of life.

Thromboprophylaxis using combined intermittent pneumatic compression and pharmacologic prophylaxis versus pharmacologic prophylaxis alone in critically ill patients: study protocol for a randomized controlled trial

BACKGROUND

Venous thromboembolism (VTE) remains a common problem in critically ill patients. Pharmacologic prophylaxis is currently the standard of care based on high-level evidence from randomized controlled trials. However, limited evidence exists regarding the effectiveness of intermittent pneumatic compression (IPC) devices. The Pneumatic compREssion for preventing VENous Thromboembolism (PREVENT trial) aims to determine whether the adjunct use of IPC with pharmacologic prophylaxis compared to pharmacologic prophylaxis alone in critically ill patients reduces the risk of VTE.

METHODS/DESIGN

The PREVENT trial is a multicenter randomized controlled trial, which will recruit 2000 critically ill patients from over 20 hospitals in three countries. The primary outcome is the incidence of proximal lower extremity deep vein thrombosis (DVT) within 28 days after randomization. Radiologists interpreting the scans are blinded to intervention allocation, whereas the patients and caregivers are unblinded. The trial has 80 % power to detect a 3 % absolute risk reduction in proximal DVT from 7 to 4 %.

DISCUSSION

The first patient was enrolled in July 2014. As of May 2015, a total of 650 patients have been enrolled from 13 centers in Saudi Arabia, Canada and Australia. The first interim analysis is anticipated in July 2016. We expect to complete recruitment by 2018.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT02040103 (registered on 3 November 2013). Current controlled trials: ISRCTN44653506 (registered on 30 October 2013).

Investigation of Blood Flow During Intermittent Pneumatic Compression and Proposal of a New Compression Protocol

INTRODUCTION

Intermittent pneumatic compression (IPC) is now a widely used therapy for the prophylaxis of deep vein thrombosis and pulmonary embolism. In general, the IPC sequence is composed of sequential compression and simultaneous deflation. Typically, veins are considered to be squeezed and emptied during the compression phase and to be refilled during the deflation phase. However, because the stop or sudden increase in blood flow can be dangerous, a further investigation is needed with respect to the blood flow.

MATERIALS AND METHODS

We demonstrated a new compression protocol based on the investigation results of venous blood flow during IPC. This new compression protocol involves successive compression without the deflation phase; thus, the expelled blood volume flow during a given period can be maximized. To investigate the blood flow during IPC, sonography movie clips and in-laboratory developed blood flow analysis software was used.

RESULTS

The increases in the peak volume flow during IPC were 49% (±24%) and 25% (±29%) with the conventional protocol and the new protocol, respectively, whereas the total volume flow (TVF) was not significantly changed (-1.0% and -13.0%, respectively). With the new protocol, the peak velocity (PV) was 49% lower than that with the conventional protocol. Thus, the new protocol has an effect of maintaining TVF without resulting in a sudden large increase or decrease in PV.

CONCLUSION

The new suggested protocol might improve safety because it can maintain the stability of blood flow by reducing the risk of blood stasis and a rapid change in blood flow.

The efficacy of intermittent pneumatic compression in the prevention of lower extremity deep venous thrombosis

Intermittent pneumatic compression (IPC) has been used to prevent lower extremity deep venous thrombosis for more than 30 years and is a popular choice for prophylaxis among both physicians and patients because of its efficacy and reduced risk of bleeding compared with pharmacologic prophylaxis. However, the efficacy of IPC may depend on the clinical situation as well as on several variables associated with the devices. To determine the efficacy of IPC, recent guidelines and literature were reviewed. IPC is efficacious as a sole prophylactic agent in low- or moderate-risk surgical patients and in patients with high risk of bleeding with pharmacologic prophylaxis. In high-risk surgical and medical patients, IPC is recommended as a synergistic tool in combination with pharmacologic agents, if pharmacologic agents are not contraindicated. No specific compression modality proved its superiority, although newer portable battery-powered devices seem to allow better patient compliance and satisfaction.

Comparison of clinical and physiological efficacies of different intermittent sequential pneumatic compression devices in preventing deep vein thrombosis: a prospective randomized study

BACKGROUND

There are few comparative studies about the optimal method of pneumatic compression to prevent deep vein thrombosis (DVT). The aim of this prospective randomized study was to compare venous hemodynamic changes and their clinical influences between two graded sequential compression groups (an alternate sequential compression device [ASCD] vs. a simultaneous sequential compression device [SSCD]).

METHODS

In total, 34 patients (68 limbs) undergoing knee and spine operations were prospectively randomized into two device groups (ASCD vs. SSCD groups). Duplex ultrasonography examinations were performed on the 4th and 7th postoperative days for the detection of DVT and the evaluation of venous hemodynamics. Continuous data for the two groups were analyzed using a two-tailed, unpaired t-test. Relative frequencies of unpaired samples were compared using Fisher exact test. Mixed effects models that might be viewed as ANCOVA models were also considered.

RESULTS

DVT developed in 7 patients (20.6%), all of whom were asymptomatic for isolated calf DVTs. Two of these patients were from the ASCD group (11.8%) and the other five were from the SSCD group (29.4%), but there was no significant difference (p = 0.331). Baseline peak velocity, mean velocity, peak volume flow, and total volume flow were enhanced significantly in both device groups (p < 0.001). However, the degrees of flow and velocity enhancement did not differ significantly between the groups. The accumulated expelled volumes for an hour were in favor of the ASCD group.

CONCLUSIONS

Both graded sequential compression devices showed similar results both in clinical and physiological efficacies. Further studies are required to investigate the optimal intermittent pneumatic compression method for enhanced hemodynamic efficacy and better thromboprophylaxis.

Re-using intermittent pneumatic compression garments designed for single-patient-use is a potential source of cross-infection

Hospital acquired illnesses such as healthcare associated infection (HCAI) and venous thromboembolism (VTE) are often preventable; however, they occur frequently, are hugely expensive and cause increased patient morbidity and mortality.

Intermittent pneumatic compression (IPC) has been proven to reduce the risk of patients developing a deep vein thrombosis (DVT). DVT prophylaxis IPC garments are designed to be single patient use, however anecdotally some hospitals re-use these products on multiple patients. This study examines the bacterial bio-burden present on IPC garments from three different manufacturers after an episode of single patient use and compares these results to a sample of unused (clean) garments. Sixty-one percent of used garments recorded >100 colony forming units (CFU) present on at least one sample plate, while the samples taken from unused garments reported either no growth (67%) or had very few organisms (less than five CFU) present (33%). IPC garment wear time and/or presence of graduated compression stockings worn beneath the garment had no impact on reducing the garment bio-burden.

After an episode of single patient use, IPC garments carry a significant bio-burden and could be a source of pathogens. DVT prophylaxis IPC garments should be utilised as single patient use.

Intermittent pneumatic compression in immobile patients

The purpose of this study is to stress the value of using intermittent pneumatic compression (IPC) in immobile patients. The use of IPC helps prevent limb oedema and the associated skin changes frequently seen on the legs of the immobile patient. Oedema formation is caused by an increase of fluid extravasation, while skin changes including leg ulcers are mainly because of a deficiency of the venous and lymphatic pumps. Conventional compression stockings and bandages impede leg swelling but are less efficient in supporting the deficient veno-lymphatic pump when patients are unable to move. In this situation, actively compressing the limb using IPC is a very meaningful and effective treatment option. Because of a lack of literature on the specific indication of IPC in immobile patients, experimental studies and randomised controlled trials in similar situations are reviewed. IPC is a very effective although underused treatment modality, especially in immobile, wheelchair-bound patients. By inflation and deflation of the air-filled garments, IPC produces cycles of pressure waves on the leg, thus mimicking the working and resting pressures applied by compression bandages. IPC not only reduces leg swelling but also augments the veno-lymphatic pump, which is essential for the restoration of the damaged microcirculation of the skin.

Doppler ultrasound measurements of venous return in the popliteal vein

An assessment of the use of Doppler ultrasound for the measurement of venous blood expelled at the site of the popliteal vein was made. Ten subjects underwent colour Doppler ultrasonography and measurements for peak venous velocities and venous blood volume expelled were taken for each subject when standing and during voluntary contractions. The study shows that only a weak correlation exists between peak venous velocities and venous blood volume expelled, indicating that peak venous velocity alone, is not an accurate measure of the performance of the calf muscle pump either naturally or via artificial means. Furthermore it has been shown that volume measurements based on manually traced intensity weighted mean velocities resulted in large deviations when compared to volume measurements based on computer traced intensity weighted mean velocities.