Evaluation of various maneuvers for prevention of air embolism during central venous catheter placement

Coronary Air Embolism Secondary to Percutaneous Lung Biopsy: A Systematic Review

To determine mortality and morbidity associated with coronary air embolism (CAE) secondary to complications of percutaneous lung biopsy (PLB) and illicit-specific risk factor associated with this complication and overall mortality, we searched PubMed to identify reported cases of CAE secondary to PLB. After assessing inclusion eligibility, a total of 31 cases from 26 publications were included in our study. Data were analyzed using Fisher's exact test. In 31 reported cases, cardiac arrest was more common after left lower lobe (LLL) biopsies (n=4, 80%, p=0.001). Of these patients who suffered from cardiac arrest, CAE was found more frequently in the right coronary artery (RCA) than other locations but did not reach statistical significance (n=5, 62%, p=0.39). At the same time, intervention in the LLL was significantly associated with patient mortality (n=3, 60%, p=0.010). Of the patients who died, CAE was more likely to have occurred in the RCA, but this association was not statistically significant (n=4, 57%, p=0.33). LLL biopsies have a statistically significant correlation with cardiac arrest and patient death. More research is needed to examine the effect of the air location in the RCA on patient morbidity and mortality.

Evaluation of the Catheter Clamp over Hydrophilic Guide Wire Central Venous Catheter Exchange Technique for Air Embolism Prophylaxis in an In Vitro Model

PURPOSE

To develop a reproducible in vitro model simulating central venous catheter (CVC) exchange with high potential for air embolization and test the hypothesis that a closed catheter clamp over hydrophilic guide wire exchange technique will significantly reduce the volume of air introduced during CVC exchange.

MATERIALS AND METHODS

The model consisted of a 16-F valved sheath, 240-mL container, and pressure transducer submerged in water in a 1,200-mL suction canister system. Continuous wall suction was applied to the canister to maintain negative pressure at -7 mm Hg or -11 mm Hg. Each trial consisted of 0.035-inch hydrophilic guide wire introduction, over-the-wire catheter exchange, and wire removal following clinical protocol. A total of 256 trials were performed, 128 trials at each pressure with the catheter clamp open (n = 64) or closed (n = 64) around the hydrophilic guide wire.

RESULTS

There was a statistically significant lower volume of air introduced with closed clamp over-the-wire exchanges than with open clamp exchanges at both pressures (2-tailed t-test, P < .001). At -7 mm Hg, a mean of 48.0 mL (SD ± 9.3) of air was introduced with open clamp and 20.6 mL (SD ± 4.7) of air was introduced with closed clamp. At -11 mm Hg, 97.8 mL (SD ± 11.9) of air was introduced with open clamp and 37.8 mL (SD ± 6.3) of air was introduced with closed clamp.

CONCLUSIONS

This study demonstrated the use of a reproducible in vitro model mimicking conditions causing air embolism during CVC exchange. Results showed that CVC exchange using closed catheter clamp over hydrophilic guide wire exchange technique significantly reduced the volume of air introduced per exchange.

An analysis of the effect of syringe barrel volume on performance and user perception

In the market, there are many types and shapes of syringes. One of the groupings of syringe types is based on barrel volume. The shape of the product design affects performance and user perception. The aim of this study is to investigate the effect of barrel volume on its performance and user perception. We performed analysis following international organization for standardization 7886 procedures on syringe with 1 mL, 3 mL, 5 mL, and 10 mL volume. In addition, a user perception test was conducted on 29 respondents using a questionnaire with the Likert chart method. This study indicates that the bigger the syringe volume, the larger the dead space and the force to operate the piston are. A larger syringe volume also raises the volume that changes due to the plunger position increase. Meanwhile, the barrel volume does not affect water and water leakage, as we did not observe any leak during the syringe tests in our experiment. In addition, the user perception test shows that the barrel's length influences the ease of device control during the injection. The volume of the barrel negatively correlated with its effect to the environment. The safety features of all syringes are similar except for the 3 mL syringe, which has a value of 0.1 points difference to other syringes.

Gravitational effects on carotid and jugular characteristics in graded head-up and head-down tilt

Altered gravity affects hemodynamics and blood flow in the neck. At least one incidence of jugular venous thrombosis has been reported in an astronaut on the International Space Station. This investigation explores the impact of changes in the direction of the gravitational vector on the characteristics of the neck arteries and veins. Twelve subjects underwent graded tilt from 45° head-up to 45° head-down in 15° increments in both supine and prone positions. At each angle, the cross-sectional area of the left and right common carotid arteries (ACCA) and internal jugular veins (AIJV) were measured by ultrasound. Internal jugular venous pressure (IJVP) was also measured by compression sonography. Gravitational dose-response curves were generated from experimental data. ACCA did not show any gravitational dependence. Conversely, both AIJV and IJVP increased in a nonlinear fashion with head-down tilt. AIJV was significantly larger on the right side than the left side at all tilt angles. In addition, IJVP was significantly elevated in the prone position compared with the supine position, most likely because of raised intrathoracic pressure while prone. Dose-response curves were compared with existing experimental data from parabolic flight and spaceflight studies, showing good agreement on an acute timescale. The quantification of jugular hemodynamics as a function of changes in the gravitational vector presented here provides a terrestrial model to reference spaceflight-induced changes, contributes to the assessment of the pathogenesis of spaceflight venous thromboembolism events, and informs the development of countermeasures.NEW & NOTEWORTHY Flow stasis and thrombosis have been identified in the jugular vein during spaceflight. We measured the area and pressure of the internal jugular vein and the area of the common carotid artery in graded head-up and head-down tilt. Experimental data are used to generate gravitational dose-response curves for the measured variables, demonstrating that jugular vein area and pressure exhibit a nonlinear response to altered gravity. Gravitational dose-response curves show good agreement with spaceflight and parabolic flight studies.

Usefulness of peripherally inserted central catheter port system (PICC-PORT) implantation in the sitting position: a new technique for cases unsuitable for conventional implantation

PURPOSE

Totally implantable central venous access port implantation is typically performed in the supine position. However, some patients cannot adopt the supine position due to severe pain and/or dyspnea. The present study evaluated the technical feasibility of peripherally inserted central catheter port system (PICC-PORT) implantation in the sitting position in such cases.

MATERIALS AND METHODS

In the sitting position method, PICC-PORT implantation was performed with the patients seated on a videofluoroscopy chair positioned between the limbs of an angiographic C-arm and the operative upper arm positioned on an arm stand. From January 2019 to September 2021, eight patients underwent PICC-PORT implantations using this sitting method. We also evaluated 251 consecutive patients with conventional supine position PICC-PORT implantation as controls. Differences in technical success, procedure time and complications were retrospectively assessed between the two groups.

RESULTS

Procedural success rates were 100% in both groups. Median procedure times in the sitting and conventional groups were 42 and 44 min, respectively. No complications were observed in the sitting group. There were no significant differences between the two groups in procedure time (p = 0.674) and complications (p = 1.000).

CONCLUSION

Implantation of PICC-PORT in the sitting position is technically feasible and useful.

Cerebral venous congestion exacerbates cerebral microhemorrhages in mice

Cerebral microhemorrhages (CMHs; microbleeds), which are small focal intracerebral hemorrhages, importantly contribute to the pathogenesis of cognitive decline and dementia in older adults. Although recently it has been increasingly recognized that the venous side of the cerebral circulation likely plays a fundamental role in the pathogenesis of a wide spectrum of cerebrovascular and brain disorders, its role in the pathogenesis of CMHs has never been studied. The present study was designed to experimentally test the hypothesis that venous congestion can exacerbate the genesis of CMHs. Increased cerebral venous pressure was induced by internal and external jugular vein ligation (JVL) in C57BL/6 mice in which systemic hypertension was induced by treatment with angiotensin II plus L-NAME. Histological analysis (diaminobenzidine staining) showed that mice with JVL developed multiple CMHs. CMHs in mice with JVL were often localized adjacent to veins and venules and their morphology was consistent with venous origin of the bleeds. In brains of mice with JVL, a higher total count of CMHs was observed compared to control mice. CMHs were distributed widely in the brain of mice with JVL, including the cortical gray matter, brain stem, the basal ganglia, subcortical white matter, cerebellum, and the hippocampi. In mice with JVL, there were more CMHs predominantly in cerebral cortex, brain stem, and cerebellum than in control mice. CMH burden, defined as total CMH volume, also significantly increased in mice with JVL. Thus, cerebral venous congestion can exacerbate CMHs. These observations have relevance to the pathogenesis of cognitive impairment associated with right heart failure as well as elevated cerebral venous pressure due to jugular venous reflux in older adults.

The aging venous system: from varicosities to vascular cognitive impairment

Aging-induced pathological alterations of the circulatory system play a critical role in morbidity and mortality of older adults. While the importance of cellular and molecular mechanisms of arterial aging for increased cardiovascular risk in older adults is increasingly appreciated, aging processes of veins are much less studied and understood than those of arteries. In this review, age-related cellular and morphological alterations in the venous system are presented. Similarities and dissimilarities between arterial and venous aging are highlighted, and shared molecular mechanisms of arterial and venous aging are considered. The pathogenesis of venous diseases affecting older adults, including varicose veins, chronic venous insufficiency, and deep vein thrombosis, is discussed, and the potential contribution of venous pathologies to the onset of vascular cognitive impairment and neurodegenerative diseases is emphasized. It is our hope that a greater appreciation of the cellular and molecular processes of vascular aging will stimulate further investigation into strategies aimed at preventing or retarding age-related venous pathologies.

Pulmonary air embolism associated with proximal bland thrombus

We report a case of pulmonary air embolism associated with proximal bland thrombus seen on computed tomography pulmonary angiography in a 49-year-old man, who developed acute hypoxia following removal of central venous catheter.

Role of age-related alterations of the cerebral venous circulation in the pathogenesis of vascular cognitive impairment

There has been an increasing appreciation of the role of vascular contributions to cognitive impairment and dementia (VCID) associated with old age. Strong preclinical and translational evidence links age-related dysfunction and structural alterations of the cerebral arteries, arterioles, and capillaries to the pathogenesis of many types of dementia in the elderly, including Alzheimer's disease. The low-pressure, low-velocity, and large-volume venous circulation of the brain also plays critical roles in the maintenance of homeostasis in the central nervous system. Despite its physiological importance, the role of age-related alterations of the brain venous circulation in the pathogenesis of vascular cognitive impairment and dementia is much less understood. This overview discusses the role of cerebral veins in the pathogenesis of VCID. Pathophysiological consequences of age-related dysregulation of the cerebral venous circulation are explored, including blood-brain barrier disruption, neuroinflammation, exacerbation of neurodegeneration, development of cerebral microhemorrhages of venous origin, altered production of cerebrospinal fluid, impaired function of the glymphatics system, dysregulation of cerebral blood flow, and ischemic neuronal dysfunction and damage. Understanding the age-related functional and phenotypic alterations of the cerebral venous circulation is critical for developing new preventive, diagnostic, and therapeutic approaches to preserve brain health in older individuals.

Repeated Valsalva maneuvers promote symptomatic manifestations of cerebral microhemorrhages: implications for the pathogenesis of vascular cognitive impairment in older adults

Multifocal cerebral microhemorrhages (CMHs, also known as "cerebral microbleeds"), which are associated with rupture of small intracerebral vessels, have been recognized as an important cause for cognitive decline in older adults. Although recent studies demonstrate that CMHs are highly prevalent in patients 65 and older, many aspects of the pathogenesis and clinical significance of CMHs remain obscure. In this longitudinal observational study, a case of a 77-year-old man with multifocal CMHs is described, in whom the rupture of intracerebral vessels could be linked to repeatedly performing extended Valsalva maneuvers. This patient was initially seen with acute aphasia after performing a prolonged Valsalva maneuver during underwater swimming. T2-weighted magnetic resonance imaging revealed a left acute frontal intracerebral hemorrhage (ICH) with multiple CMHs. The aphasia was resolved and no cognitive impairment was present. Two years later, he developed unsteadiness and confusion after performing two prolonged Valsalva maneuvers during underwater swimming separated by about 12 days. Repeat brain imaging revealed an acute right and a subacute left ICH, with a marked interval increase in the number of CMHs. The patient also exhibited manifest memory loss after the second admission and was diagnosed with dementia. These observations suggest that prolonged Valsalva maneuver is potentially a common precipitating cause of both CMHs and symptomatic ICHs. The Valsalva maneuver both increases the systolic arterial pressure and gives rise to a venous pressure wave transmitted to the brain in the absence of the competent antireflux jugular vein valves. This pressure increase is superimposed on existing hypertension and/or increases in blood pressure due to exercise and increased venous return due to immersion of the body in water. We advocate that further studies are needed to distinguish between CMHs with arterial and venous origins and their potential to lead to ICH induced by Valsalva maneuver as well as to determine whether these lesions have a predilection for a particular location.

The Valsalva manoeuvre versus tourniquet for venipuncture

BACKGROUND

During ultrasound-guided cannulation, venous filling is required for venipuncture. Tourniquet with an elastic tube at the axilla is the most common method to induce venous stasis for cannulation of the deep veins of the arm. Although effective, this method might be associated with short- and long-term complications. Valsalva manoeuvre has been used to produce venous filling in other extrathoracic veins. The aim of this observational study is to demonstrate the effect of Valsalva manoeuvre in respect of the elastic tourniquet on venous distention during echography-guided cannulation of the deep veins of the arm.

METHOD

Sixty-nine patients scheduled for cannulation of basilic or brachial vein were prospectively observed. Vein diameters were recorded at rest and after 10 s of Valsalva or tourniquet placement.

RESULTS

The mean difference between basilic vein diameters during tourniquet and Valsalva manoeuvre was 0.006 mm (95% confidence interval = -inf, 0.09) with a standard deviation of 0.5 mm (95% confidence interval = 0.5, 0.7; p > 0.01). The mean difference between brachial vein diameters during tourniquet and Valsalva manoeuvre was 0.04 mm (95% confidence interval = -0.23, 0.15) with a standard deviation of 0.8 mm (95% confidence interval = 0.7, 0.9; p > 0.01).

DISCUSSION

This increase in cross-sectional basilic and brachial vein diameters was not different to that obtained with the elastic tube tourniquet.

Vascular air embolism: A silent hazard to patient safety

PURPOSE

To narratively review published information on prevention, detection, pathophysiology, and appropriate treatment of vascular air embolism (VAE).

MATERIALS AND METHODS

MEDLINE, SCOPUS, Cochrane Central Register and Google Scholar databases were searched for data published through October 2016. The Manufacturer and User Facility Device Experience (MAUDE) database was queried for "air embolism" reports (years 2011-2016).

RESULTS

VAE may be introduced through disruption in the integrity of the venous circulation that occurs during insertion, maintenance, or removal of intravenous or central venous catheters. VAE impacts pulmonary circulation, respiratory and cardiac function, systemic inflammation and coagulation, often with serious or fatal consequences. When VAE enters arterial circulation, air emboli affect cerebral blood flow and the central nervous system. New medical devices remove air from intravenous infusions. Early recognition and treatment reduce the clinical sequelae of VAE. An organized team approach to treatment including clinical simulation can facilitate preparedness for VAE. The MAUDE database included 416 injuries and 95 fatalities from VAE. Data from the American Society of Anesthesiologists Closed Claims Project showed 100% of claims for VAE resulted in a median payment of $325,000.

CONCLUSIONS

VAE is an important and underappreciated complication of surgery, anesthesia and medical procedures.

Venous air embolism related to the use of central catheters revisited: with emphasis on dialysis catheters

Venous air embolism is a dreaded condition particularly relevant to the field of nephrology. In the face of a favourable, air-to-blood pressure gradient and an abnormal communication between the atmosphere and the veins, air entrance into the circulation is common and can bring about venous air embolism. These air emboli can migrate to different areas through three major routes: pulmonary circulation, paradoxical embolism and retrograde ascension to the cerebral venous system. The frequent undesirable outcome of this disease entity, despite timely and aggressive treatment, signifies the importance of understanding the underlying pathophysiological mechanism and of the implementation of various preventive measures. The not-that-uncommon occurrence of venous air embolism, often precipitated by improper patient positioning during cervical catheter procedures, suggests that awareness of this procedure-related complication among health care workers is not universal. This review aims to update the pathophysiology of venous air embolism and to emphasize the importance of observing the necessary precautionary measures during central catheter use in hopes of eliminating this unfortunate but easily avoidable mishap in nephrology practice.

Cerebral microhemorrhages: mechanisms, consequences, and prevention

The increasing prevalence of multifocal cerebral microhemorrhages (CMHs, also known as "cerebral microbleeds") is a significant, newly recognized problem in the aging population of the Western world. CMHs are associated with rupture of small intracerebral vessels and are thought to progressively impair neuronal function, potentially contributing to cognitive decline, geriatric psychiatric syndromes, and gait disorders. Clinical studies show that aging and hypertension significantly increase prevalence of CMHs. CMHs are also now recognized by the National Institutes of Health as a major factor in Alzheimer's disease pathology. Moreover, the presence of CMHs is an independent risk factor for subsequent larger intracerebral hemorrhages. In this article, we review the epidemiology, detection, risk factors, clinical significance, and pathogenesis of CMHs. The potential age-related cellular mechanisms underlying the development of CMHs are discussed, with a focus on the structural determinants of microvascular fragility, age-related alterations in cerebrovascular adaptation to hypertension, the role of oxidative stress and matrix metalloproteinase activation, and the deleterious effects of arterial stiffening, increased pulse pressure, and impaired myogenic autoregulatory protection on the brain microvasculature. Finally, we examine potential treatments for the prevention of CMHs based on the proposed model of aging- and hypertension-dependent activation of the reactive oxygen species-matrix metalloproteinases axis, and we discuss critical questions to be addressed by future studies.

Air Embolism: Diagnosis, Clinical Management and Outcomes

Air embolism is a rare but potentially fatal complication of surgical procedures. Rapid recognition and intervention is critical for reducing morbidity and mortality. We retrospectively characterized our experience with air embolism during medical procedures at a tertiary medical center. Electronic medical records were searched for all cases of air embolism over a 25-year period; relevant medical and imaging records were reviewed. Sixty-seven air embolism cases were identified; the mean age was 59 years (range, 3–89 years). Ninety-four percent occurred in-hospital, of which 77.8% were during an operation/invasive procedure. Vascular access-related procedures (33%) were the most commonly associated with air embolism. Clinical signs and symptoms were related to the location the air embolus; 36 cases to the right heart/pulmonary artery, 21 to the cerebrum, and 10 were attributed to patent foramen ovale (PFO). Twenty-one percent of patients underwent hyperbaric oxygen therapy (HBOT), 7.5% aspiration of the air, and 63% had no sequelae. Mortality rate was 21%; 69% died within 48 hours. Thirteen patients had immediate cardiac arrest where mortality rate was 53.8%, compared to 13.5% (p = 0.0035) in those without. Air emboli were mainly iatrogenic, primarily associated with endovascular procedures. High clinical suspicion and early treatment are critical for survival.

Air Embolism: Practical Tips for Prevention and Treatment

Air embolism is a rarely encountered but much dreaded complication of surgical procedures that can cause serious harm, including death. Cases that involve the use of endovascular techniques have a higher risk of air embolism; therefore, a heightened awareness of this complication is warranted. In particular, central venous catheters and arterial catheters that are often placed and removed in most hospitals by a variety of medical practitioners are at especially high risk for air embolism. With appropriate precautions and techniques it can be preventable. This article reviews the causes of air embolism, clinical management and prevention techniques.

Over-catheter tract suture to prevent bleeding and air embolism after tunnelled catheter removal

Introduction

Severe, life-threating, complications might occur on dialysis catheter removal.

Methods

We present a useful technique that may prevent vascular air embolism and severe bleeding.

Results

The suture is placed around the catheter and tied over previous tract just after device removal.

Conclusions

Applying a compressing suture to the tract left after removal of a tunnelled haemodialysis catheter is a simple manoeuvre that could prevent severe complication.

Tunneled Central Venous Catheter Exchange: Techniques to Improve Prevention of Air Embolism

Malfunctioning tunneled hemodialysis central venous catheters (CVCs), because of thrombotic or infectious complications, are frequently exchanged. During the CVC exchanging procedure, there are several possible technical complications, as in first insertion, including air embolism. Prevention remains the key to the management of air embolism. Herein, we emphasize the technical tricks capable of reducing the risk of air embolism in long-term CVC exchange. In particular, adoption of a 5 to 10 degrees Trendelenburg position, direct puncture of the previous CVC venous lumen for guide-wire insertion, as opposed to guide-wire introduction after cutting the CVC, a light manual compression of the internal jugular vein venotomy site after catheter removal. The Valsalva maneuvre in collaborating patients, valved introducers, and correction of hypovolemia are also useful precautions. Principles of air embolism diagnosis and treatment are also outlined in the article.

VenaTrac™ Device for Over-the-Wire Placement of Chronic Dialysis Catheters

Purpose

The VenaTrac™ is designed for exchange and primary placement of chronic tunneled hemodialysis catheters over a wire. It occludes both lumens of the catheter for the purpose of reducing the risk of air embolism and blood loss. The purpose of this paper is to report our experience with the use of this device.

Methods

A retrospective review of chronic hemodialysis dialysis catheters exchanges over a 30-month period was performed. Two hundred and ninety-seven over-the-wire catheter exchanges and 47 primary placements using the VenaTrac™ device were reviewed. In addition, 430 over-the-wire catheter exchanges without the use of the VenaTrac™ were reviewed.

Results

No insertional complications or air embolism occurred when using the VenaTrac™. Symptomatic air embolism was documented in 5 out of 430 catheter exchanges performed without the use of VenaTrac™ (1.2%).

Conclusions

VenaTrac™ over-the-wire insertion device demonstrated safe and reliable use with no incidence of air embolism.

Humming Is as Effective as Valsalva’s Maneuver and Trendelenburg’s Position for Ultrasonographic Visualization of the Jugular Venous System and Common Femoral Veins

STUDY OBJECTIVE

The purpose of this study is to compare ultrasonographic visualization of the jugular and common femoral veins by using a novel technique (humming) and 2 conventional techniques (Valsalva's maneuver and Trendelenburg's position). The Valsalva's maneuver and Trendelenburg's position are common methods for producing venous distention, aiding ultrasonographically guided identification and cannulation of the jugular and common femoral veins. We hypothesize that humming is as effective as either Valsalva's maneuver or Trendelenburg's position for distention and ultrasonographic visualization of these procedurally important blood vessels. Herein, we investigate a new method of venous distension that may aid in the placement of central venous catheters by ultrasonographic guidance.

METHODS

Healthy, normal volunteers aged 28 to 67 years were enrolled. Each subject's internal jugular, external jugular, and common femoral veins were measured in cross-section by ultrasonograph during rest (baseline), humming, Valsalva's maneuver, and Trendelenburg's position. Three measurements were recorded per observation in each position. Subjects were used as their own controls, and measurements were normalized to percentage increase in diameter during each maneuver or position for later comparison.

RESULTS

The study population consisted of 7 subjects, with a mean age of 47 years. Cross-sectional area was calculated for each vessel in 3 groups: baseline/control, Valsalva, Trendelenburg, and humming. The mean percentage change (+/-SD) relative to baseline cross-sectional area of the jugular vessels for each subject were external jugular vein: humming 134%+/-25% (95% confidence interval [CI] 124.9% to 146.9%), Valsalva 136%+/-23% (95% CI 121.3% to 147.5%), Trendelenburg 137%+/-32% (95% CI 120.7% to 156.9%); internal jugular vein: humming 137%+/-27% (95% CI 119.4% to 148.2%), Valsalva 139%+/-24% (95% CI 122.4% to 148.7%), Trendelenburg 141%+/-35% (95% CI 116.5% to 156.5%); common femoral vein: humming 131%+/-15% (95% CI 120.4% to 139.1%), Valsalva 139%+/-18% (95% CI 127.9% to 150.4%), Trendelenburg 132%+/-24% (95% CI 113.3% to 142.9%).

CONCLUSION

All 3 maneuvers distended the external jugular, internal jugular, and common femoral veins compared to baseline. There was no important difference in magnitude of cross-sectional area between any of the 3 maneuvers when compared with one another. Humming shares many physiologic similarities to Valsalva's maneuver and may be more familiar and easier to perform during procedures such as ultrasonographically guided central venous catheter placement and insertion of external jugular intravenous catheters.

Echocardiographic diagnosis of air embolism associated with central venous catheter placement: case report and review of the literature

Transthoracic echocardiography (TTE) is a valuable tool in the evaluation of patients with suspected air embolism. This report describes the presentation and evaluation of a critically ill woman with spontaneous air embolism occurring during a central venous catheter replacement. Bedside TTE established the diagnosis of air embolism, allowing prompt initiation of appropriate therapy. This case report highlights this uncommon but potentially life-threatening complication of central line placement and the utility of echocardiography in its evaluation.

Aerostasis during Central Venous Access: Updates in Protective Sheaths

PURPOSE

Air emboli (AE) complicating central venous catheter (CVC) placement are rare but potentially fatal events. Building on earlier experience, the authors conducted in vitro testing of the aerostatic properties of newly designed protective sheaths.

MATERIALS AND METHODS

The standard peel-away sheath, the previously studied sliding-valve sheath, and newer fixed-valve and double-valved sheaths were evaluated. Aerostatic stability of the sheaths was evaluated by measuring air flow into the model under standard and stressed conditions. In addition, volumes of AE created during simulated CVC insertion through the sheaths were determined.

RESULTS

Under physiologic conditions, significantly smaller volumes of AE occurred with a pinch 2 inches from the sheath hub relative to a pinch at 1 inch. Sliding-, fixed-, and double-valve sheaths yielded leak rates of 0.05 +/- 0.05 mL/sec, 0.06 +/- 0.05 mL/sec, and 0.08 +/- 0.07 mL/sec, respectively. Under stress, protective sheath leak rates increased to 1.8 +/- 0.4 mL/sec, 1.6 +/- 0.5 mL/sec, and 1.8 +/- 0.4 mL/sec, respectively. Use of a double-valved sheath demonstrated no significant difference in leak rates under standard and stressed conditions. In most cases, protective sheaths yielded significantly smaller AE than control sheaths. In comparison of protective sheaths, AE volumes during CVC insertion for sliding-, fixed-, and double-valved sheaths were 22.8 +/- 4.5 mL, 16.6 +/- 7.3 mL, and 10.8 +/- 4.5 mL, respectively. Double-valved sheaths yielded significantly smaller AE volumes than did sliding-valve sheaths (P < .01).

CONCLUSIONS

In most standard situations, AE volumes and aerostatic stability of protective sheaths tested favorably in comparison with control sheaths. When some sheaths were stressed, their aerostatic properties failed. In a comparison of the three protective sheaths in standard and stressed conditions, the double-valved sheath fared better than the sliding and fixed-valve sheaths.

Disclosing errors and adverse events in the intensive care unit*

OBJECTIVE

To review the issue of disclosing errors in care and adverse events that have caused harm to patients in critical care.

DESIGN

Review the scope of the problem, the definitions of errors and adverse events, and the benefits and problems of disclosing errors and adverse events and provide an approach by which to have these difficult discussions.

SETTING

Medical center.

PATIENTS

Critically ill patients and their families.

INTERVENTIONS

Applying a systematic framework for disclosing errors and adverse events to affected patients and their families.

MEASUREMENTS AND MAIN RESULTS

Several national organizations mandate that physicians discuss errors in care and adverse events that have caused harm with affected patients, but failure to do so is a common problem in critical care as surveys of intensivists indicate that, although most believe that errors should be disclosed, few routinely do so. The likelihood of an adverse event is increased in intensive care units because of the nature of critical care. Not all errors or adverse events require disclosure. There are ethical, financial, legal, systems, and personal benefits to disclosing errors, and disclosure discussions should address common patient concerns.

CONCLUSIONS

Failure to disclose errors and adverse events in critical care is an important and common problem. There are numerous reasons why errors and adverse events should be disclosed, and use of a standard framework for doing so will facilitate the process.

Bench-Top Evaluation of Air Flow through a Valved Peelable Introducer Sheath

PURPOSE

Air embolism is a rare but potentially fatal complication that may occur during the insertion of a central venous catheter. A valved peelable introducer sheath was developed to reduce the likelihood of an air embolus. This study was performed to determine the rate of air flow through this valved introducer sheath under different conditions that may be encountered in a clinical setting.

MATERIALS AND METHODS

A 16-F-diameter valved peelable introducer sheath was used for all experiments. A bench-top testing system was constructed that consisted of a vacuum source, a mass flow meter, and a digital vacuum gauge. A coupling device with a pneumatic O-ring was used to seal and connect the distal end of the introducer sheath to the testing system. A vacuum of -5 mm Hg was applied to the sealed distal end of the sheath to simulate physiologic conditions. The rate of air flow through the valved sheath was measured under three different conditions; (i) valve open, (ii) valve closed, and (iii) valve open but with the sheath manually pinched. Thirty air flow measurements were performed for each of the three test conditions.

RESULTS

When the valve was in the open position, the mean rate of air flow through the introducer sheath was 417.2 mL/sec (range, 415.5-419.7 mL/sec). When the valve was in the closed position, the mean rate of air flow was 0.004 mL/sec (range, 0.000-0.067 mL/sec). When the valve was open but the sheath was manually pinched, the mean rate of air flow through the sheath was 31.7 mL/sec (range, 23.0-38.8 mL/sec). During the 90 testing procedures, the mean vacuum was -5.10 mm Hg (range, -5.00 to -5.45 mm Hg).

CONCLUSIONS

This bench-top study revealed that a massive amount of air flowed through the open 16-F introducer sheath when it was subjected to a vacuum of -5 mm Hg, a situation that may occur under normal physiologic conditions. The rate of air flow could be decreased by aggressively pinching the sheath but the rate of air flow was still substantial. This study demonstrated that the addition of a sophisticated valve mechanism can essentially eliminate air flow through a peelable introducer sheath.

Measurement of Air Emboli during Central Venous Access: Do “Protective” Sheaths or Insertion Techniques Matter?

PURPOSE

Clinically significant air emboli during placement of central venous catheters are rare yet potentially fatal events. An in vitro model was developed to measure the volume of air emboli during catheter placement under a variety of experimental conditions.

MATERIALS AND METHODS

The volume of air emboli during catheter insertion with use of a standard sheath was measured using "open," "finger-pinch," and "hemostat" techniques. Corresponding experiments were performed with newly designed protective sheaths. Additional experiments evaluated the air emboli related to specific steps of catheter insertion, a sheathless insertion technique, and two commonly used dialysis catheters.

RESULTS

Under physiologic conditions, the volumes of air emboli were 9.1 mL +/- 3.6, 8.6 mL +/- 3.9, and 10.0 mL +/- 4.1 for dialysis catheter insertions with open, finger-pinch, and hemostat techniques, respectively. In the open and closed positions, the sliding-valve protective sheath yielded 5.8 mL +/- 2.3 and 4.4 mL +/- 2.3 of air emboli, respectively, and the slide-clamp protective sheath yielded 5.6 mL +/- 2.0 and 5.4 mL +/- 2.1 of air emboli, respectively. The standard sheath demonstrated air emboli volumes of 14.4 mL +/- 12.8, 17.3 mL +/- 3.9, and 32.3 mL +/- 10.9 during cumulative steps of catheter insertion. The sliding-valve and slide-clamp protective sheaths yielded air emboli measuring 4.4 mL +/- 2.0, 10.9 mL +/- 5.2, and 8.6 mL +/- 1.5, and 4.4 mL +/- 1.8, 10.9 mL +/- 1.4, and 9.4 mL +/- 4.0, respectively. The sheathless insertion technique resulted in air emboli measuring 12.2 mL +/- 5.4. Split-tip and step-tip catheters resulted in air emboli volumes of 16.1 mL +/- 4.5 and 15.3 mL +/- 7.6, respectively, in the open position and 11.3 mL +/- 3.1 and 12.9 mL +/- 5.0, respectively, in the closed position.

CONCLUSIONS

The newly designed protective sheaths result in smaller volumes of air emboli compared with standard sheaths in most situations evaluated. There was no significant difference in the volume of air emboli with use of protective clinical maneuvers. In some cases, the volume of the air emboli continued to increase during catheter insertion and sheath removal. There was no statistically significant difference between the use of protective sheaths and the use of the sheathless insertion technique.

American Society of Diagnostic and Interventional Nephrology Section Editor: Stephen Ash: Preliminary Evaluation of a Valved Introducer Sheath for the Insertion of Tunneled Hemodialysis Catheters

This brief technical report describes our initial experience using the FlowGuard valved introducer sheath during the insertion of tunneled hemodialysis catheters in 15 patients. The incorporation of a silicone valve into the introducer sheath is intended to minimize blood loss and decrease the risk of air embolism during the catheter insertion procedure. Our preliminary experience demonstrated that the FlowGuard sheath is a substantial improvement when compared to standard introducer sheaths. However, an asymptomatic air embolus did occur in one patient. This article describes several caveats for the use of this new product.

Central venous catheter techniques in infants and children

PURPOSE OF REVIEW

The placement of central venous catheters is often necessary to facilitate optimal anaesthetic and perioperative management or for the long-term management of chronic underlying diseases. Insertion may be a challenge in selected patients, and the risk of infection, thrombosis, and other complications may result in significant risk factors.

RECENT FINDINGS

Ultrasound visualization of the cervical veins with Valsalva manoeuvres significantly increases the rate and safety of central venous cannulation, and decreases needle passes in paediatric patients even with experienced operators. Pericardial effusion with tamponade is a more frequent phenomenon than generally realized, and accurate location of the catheter-tip position is essential. The femoral venous approach has proved to be safe even in premature babies. Clear guidelines for infection control and the prevention of intravascular catheter-related infections in children have been established; however, the high incidence of nosocomial catheter-related infections requires effective prevention strategies. The impact of antimicrobial-impregnated central venous catheters on the prevention of bloodstream infections in children is not yet clear. Routine use of prophylactic antibiosis (i.e. vancomycin) to prevent catheter-related infection cannot be recommended. Thrombolytic therapy with recombinant tissue plasminogen activator is safe, efficient, well tolerated and effective for lysis of catheter-induced intravascular and intracardiac thrombi even in neonates. Embolized catheter fragments can be retrieved in neonates and children by non-surgical interventions using standard procedures applied by paediatric cardiologists.

SUMMARY

Despite a variety of new techniques, the major problem of central venous catheterization in neonates and children remains the prevention of catheter-related infection and infection control.

Air embolism during insertion of central venous catheters

PURPOSE

To determine the clinical consequences of air embolism occurring during insertion of central venous catheters.

MATERIALS AND METHODS

A computer search of our interventional radiology database revealed that 11,583 central venous catheters were inserted between January 1, 1995 and August 1, 2000: 7,178 were nontunneled and 4,404 were tunneled. Air embolism was reported to have occurred in 15 patients. Air embolization was recognized by audible air aspiration during catheter insertion or by fluoroscopic visualization of air within the right atrium or pulmonary artery. The radiology reports and medical records of these 15 patients were reviewed.

RESULTS

All 15 patients had an air embolism occur during insertion of a tunneled central venous catheter. These included eight Ash catheters, five chest wall ports, one Tesio catheter, and one Pheres-Flow catheter. Four patients remained asymptomatic. Six patients had mild symptoms that quickly resolved with supplemental oxygen. Four had moderate symptoms that also resolved with supplemental oxygen. One patient died acutely as a result of the air embolism.

CONCLUSION

Air embolism is a rare but potentially fatal complication of central venous catheter procedures. In our series, all occurred during insertion of a tunneled catheter through a peel-away sheath. The administration of supplemental oxygen was an effective treatment in the majority of patients.