Clinical review: alternative vascular access techniques for continuous hemofiltration

Development of a Modular Tissue Phantom for Evaluating Vascular Access Devices

Central vascular access (CVA) may be critical for trauma care and stabilizing the casualty. However, it requires skilled personnel, often unavailable during remote medical situations and combat casualty care scenarios. Automated CVA medical devices have the potential to make life-saving therapeutics available in these resource-limited scenarios, but they must be properly designed. Unfortunately, currently available tissue phantoms are inadequate for this use, resulting in delayed product development. Here, we present a tissue phantom that is modular in design, allowing for adjustable flow rate, circulating fluid pressure, vessel diameter, and vessel positions. The phantom consists of a gelatin cast using a 3D-printed mold with inserts representing vessels and bone locations. These removable inserts allow for tubing insertion which can mimic normal and hypovolemic flow, as well as pressure and vessel diameters. Trauma to the vessel wall is assessed using quantification of leak rates from the tubing after removal from the model. Lastly, the phantom can be adjusted to swine or human anatomy, including modeling the entire neurovascular bundle. Overall, this model can better recreate severe hypovolemic trauma cases and subject variability than commercial CVA trainers and may potentially accelerate automated CVA device development.

Skin Necrosis Distal to a Rapid Infusion Catheter: Understanding Possible Complications of Large-bore Vascular Access Devices

Rapid infusion catheters (RICs) allow expedient conversion of peripheral intravenous (PIV) catheters to peripheral sheaths; however, little is known about potential complications. In this case, a 64-year-old male polytrauma patient had a 20-gauge PIV catheter in the right cephalic vein upsized to an 8.5 French (Fr) RIC without incident during an arrest with pulseless electrical activity (PEA). On RIC post-placement day two, the patient developed edema and ecchymosis extending from the right dorsal mid-hand to the antecubital fossa, just distal to the RIC insertion point. Compartments were soft; the volar surface (including an arterial line location), fingers, and upper arm were normal. The RIC flushed and returned blood appropriately. Ultrasound revealed a noncompressible cephalic vein either related to the catheter or thrombosis, and imaging of the hand showed an ulnar styloid fracture and a minimally displaced triquetral fracture. The RIC was removed immediately. Over the next week, the areas of ecchymosis developed bullae and then sloughed, leaving open wounds extending into the dermis. The patient later expired from unrelated causes.

The area and timing of the skin necrosis were highly suspicious for a catheter-associated complication, despite the presence of the arterial line and small distal fractures. The necrosis was potentially due to thrombosis of the superficial venous outflow system, leading to congestion and skin compromise, but we found no similar reports. Alternatively, the catheter may have ruptured the vein and caused a gravity-dependent ecchymosis, but the volar surface was not impacted, and the catheter was functioning properly. The RIC may also have encroached on the arterial space, decreasing flow, but we would have expected distal hand changes. The only published reports we could find on RIC complications involved a lost guide wire, fragmentation of a catheter during placement, and a case of compartment syndrome, raising the question of whether skin necrosis is truly a rare event or simply underreported with the RIC. Although the exact causal relationship remains unknown in our case, RICs should be removed as soon as possible after immediate stabilization.

Successful continuous renal replacement therapy using two single-lumen catheters in neonates and infants with cardiac disease

BACKGROUND

Acute kidney injury (AKI) frequently occurs in neonates and infants after cardiopulmonary bypass (CPB) and may require renal replacement therapy (RRT). Peritoneal dialysis (PD) is the RRT modality of choice in neonates with AKI after CPB, but continuous renal replacement therapy (CRRT) may be necessary if PD is ineffective or contraindicated. Vascular access is challenging in this population, in part, due to small central vein size that may preclude placement. The risk of malfunction or morbidity associated with standard dialysis catheters may be excessive in neonates with congenital heart disease. We describe a unique approach to vascular access for CRRT in six small patients with AKI.

CASE-DIAGNOSIS/TREATMENT

This is a retrospective review of six patients with fluid overload and AKI that received CRRT because PD was contraindicated. In all cases, CRRT was performed via two hemostasis valve sheaths placed into separate veins for dialysis access and return. The low-resistance sheaths provided excellent blood flow with normalization of metabolic derangements and significant fluid removal (median negative 167 ml/kg at 72 h). Mean circuit life before the first change was 55.2 ± 30.4 h.

CONCLUSIONS

The use of two small single-lumen catheters in separate veins enables consistent and effective hemodiafiltration in neonates and infants with challenging vascular access.

Central venous thrombosis and perioperative vascular access in adult intestinal transplantation

BACKGROUND

Venous access is crucial in intestinal transplantation, but a thrombosed venous system may prevent the use of central veins of the upper body. The incidence of venous thrombosis and the necessity to perform alternative vascular access (AVA) in intestinal transplant recipients have not been fully investigated.

METHODS

Records of adult patients who underwent intestinal transplantation between January 1, 2001, and December 31, 2009, were reviewed. Contrast venography was performed as pre-transplantation screening. Vascular accesses at the transplantation were categorized as I (percutaneous line via the upper body veins), II (percutaneous line via the lower body veins), and III (vascular accesses secured surgically, with interventional radiology, or using non-venous sites). Categories II and III were defined as AVA. Risk factors for central venous thrombosis and those for requiring AVA were analysed, respectively.

RESULTS

Among 173 patients, central venous obstruction or stenosis (<50% of normal diameter) was found in 82% (141 patients). AVA was required in 4.6% (eight patients: four in each category II and III). Large-bore infusion lines were placed via the femoral arteries in all category III patients without complications. Existing inferior vena cava filter and hypercoagulable states were identified as the risk factors for the use of AVA, but not for central venous thrombosis. Outcomes of patients who underwent AVA were similar to those of patients without AVA.

CONCLUSIONS

The majority of adult patients undergoing intestinal transplantation had at least one central venous stenosis or obstruction. The recipient outcomes were comparable when either standard vascular access or AVA was used for transplantation.

Year in review 2007: Critical Care--nephrology

We summarize original research in the field of critical care nephrology that was accepted for publication or published in 2007 in Critical Care and, when considered relevant or directly linked to this research, in other journals. Four main topics were identified for a brief overview. The first of these was the definition of acute kidney injury and recent evidence showing the validity of RIFLE (Risk, Injury, Failure, Loss and End-stage kidney disease) criteria and the recent Acute Kidney Injury Network review of the same criteria. Second, we cover the clinical and experimental utilization of novel biomarkers for diagnosis of acute kidney injury, giving special attention to neutrophil gelatinase-associated lipocalin protein. The third area selected for review is outcomes of acute kidney injury during the past 10 years, described by a recent Austrailian epidemiological study. Finally, specific technical features of renal replacement therapies were examined in 2007, specifically regarding anticoagulation and vascular access.

Multiple organ system extracorporeal support in critically ill children

Multiple organ system extracorporeal support effectively supports brain, heart, lung, liver, kidney, coagulation, red blood cell, and immune cell function in the sickest infants and children who have multiple organ system failure. These therapies have optimum benefit if: (1) the underlying disease is reversible; (2) the therapies are performed expertly and are monitored to prevent and minimize systemic hemolysis; and (3) the therapies are provided in a goal-directed manner. These therapies represent a significant advance in pediatric critical care medicine. This article provides a framework for this multidisciplinary team approach for implementing these therapies.

Brachio-cephalic ('Gracz') fistula use for continuous hemofiltration in a hemodynamically unstable hemodialysis patient without venous vascular access: a case report

Even in patients with chronic renal failure and chronic intermittent hemodialysis, continuous venovenous hemofiltration (CVVH) is the most often practiced renal replacement technique in the intensive care unit. Although patients show less hemodynamic instability during CVVH than during hemodialysis, it requires a blood flow exceeding 200 ml/min in the extracorporeal circuit necessitating the use of large bore catheters. Vascular access in critically ill septic and edematous patients is sometimes difficult, or even impossible.

We describe a technique of using a brachio-cephalic arterio-venous fistula in a hemodialysis patient for continuous hemofiltration (HF) resulting in improved hemodynamic stability.