The International Journal of Artificial Organs

Heart failure is a major cause of mortality and morbidity, particularly among patients with advanced disease and no access to cardiac transplantation. LVAD implantation is not only a bridge-to-transplantation option for patients awaiting a heart donor, but is often used as bridge-to-destination therapy in patients unsuited for transplantation for various reasons. LVAD infection is considered the second-most common cause of death in patients who survive the initial 6 months on LVAD support. Few reports describe the indications for chronic suppressing antibiotic therapy, device exchange, methods for exchanging infected devices, post-exchange antimicrobial management status, and the outcomes of such patients.

This is the case of a 74-year-old male patient with numerous comorbidities who received urgent surgical management for severe heart failure with a HeartMate II. Six months later he developed an LVAD pump infection with methicillin-resistant Staphylococcus epidermidis, which was diagnosed with leucocyte scintigraphy. The patient received an omental graft over the LVAD and a chronic suppressive antibiotic regime. A marked leukocyte scintigraphy showed the infection's regression 6 months after the initiation of antibiotic treatment.

We concisely reviewed the driveline infections and the main aspects of the LVAD pump infection. We reviewed options for conservative and nonconservative management and showed that conservative management of the LVAD pump infection is possible.

There are no defined recommendations for the management of LVAD pump infection. This case is among the few in the literature showing that conservative treatment of an LVAD pump infection is possible.

Waste products of metabolism accumulate in patients with chronic kidney disease, and require clearance by haemodialysis (HD). We wished to determine whether there was an association between resting energy expenditure (REE) and total energy expenditure (TEE) in HD patients and body composition.

We determined REE by recently validated equations (CKD equation) and compared REE with that estimated by standard equations for REE, and TEE calculated from patient reported physical activity, in HD patients with corresponding body composition measured by dual energy X-ray absorptiometry (DEXA) scanning.

We studied 107 patients, 69 male (64.5%), mean age 62.7 ± 15.1 years. The CKD equation REE was 72.5 ± 13.3 watts (W) and TEE 83.2 ± 9.7 W There was a strong association between REE with body surface area (BSA) (r² = 0.80), total soft lean and fat lean tissue mass (r² = 0.69), body mass index (BMI) (r² = 0.34), all p<0.001. REE estimated using the modified Harris Benedict, Mifflin St. Jeor, Katch McArdle, Bernstein and Robertson equations underestimated REE compared to the CKD equation. TEE was more strongly associated with BSA (r² = 0.51), appendicular muscle mass (r² = 0.42), than BMI (r² = 0.15) all p<0.001.

TEE was greater for those employed (104.9 ± 10.7 vs. 83.1 ± 12.3 W, p<0.001), and with no co-morbidity (88.7 ± 14.8 vs. 82.7 ± 12.3 W, P<0.05).

Standard equations underestimate REE in HD patients compared to the CKD equation. TEE was greater in those with more skeletal muscle mass, in those who were employed and in those with the least comorbidity. More metabolically active patients may well require greater dialytic clearances.

To determine whether obese surgical patients are at a significant disadvantage in terms of outcomes after extracorporeal device (ECD) support, such as veno-venous extracorporeal membrane oxygenation (VV ECMO) or pumpless extracorporeal lung assist (pECLA), for respiratory failure, the relationship between body mass index (BMI) and hospital outcomes was analyzed.

This retrospective study included data on patients who were supported with an ECD between January 1, 2008 and December 31, 2014. The analysis included 89 patients (74 male).

The median BMI was 30 kg/m² (19–88.5). The median duration of the ECD support was 9.0 days, with a maximum of 37.1 days. The median LOS (length of stay) in the intensive care unit (ICU) was 21 days (range 0.06–197.6). The median hospital LOS was 34.9 days (range 0.1–213.8). VV ECMO was performed 72 times, and pECLA was performed 18 times. The number of patients successfully weaned off the ECD was 54 (60.6%). Survival at the discharge from the hospital was 48.3%.

54 (60.6%) patients were successfully weaned off the ECD; 43 (48.3%) patients survived and were discharged from the hospital. The analysis of correlations between BMI and outcomes of surgical patients treated with ECD showed no association between BMI and mortality. Complications (especially oxygenator clotting) were not more frequent in obese and extremely obese patients. We hypothesized that patients with higher or morbid BMIs would have increased mortality after ECD support. A BMI of 30.66 kg/m² corresponded to the desired sensitivity and specificity to predict mortality. This finding applied only to the study group. Treatment with ECD in obese patients presents unique challenges, including percutaneous cannulation and increased staff requirements. However, based on these data, obesity should not be an exclusion criterion for ECD therapy.

The implantation of rotary blood pumps as ventricular assist devices (VADs) has become a viable therapy for quite a number of patients with end-stage heart failure. However, these rotary blood pumps cause adverse events that are related to blood trauma. It is currently believed that turbulence in the pump flow plays a significant role. But turbulence has not been measured to date because there is no optical access to the flow space in rotary blood pumps because of their opaque casings.

This difficulty is overcome with a scaled-up model of the HeartMate II (HM II) rotary blood pump with a transparent acrylic housing. A 2-component laser Doppler velocimetry (LDV) system was used for the measurement of time resolved velocity profiles and velocity spectra upstream and downstream of the rotor blades. Observing similarity laws, the speed and pump head were adjusted to correspond closely to the design point of the original pump – 10,600 rpm speed and 80 mmHg pressure head. A model fluid consisting of a water-glycerol mixture was used.

The measured velocity spectra were scalable by the Kolmogorov length and the Kolmogorov length was estimated to be between 14 and 24 μm at original scale, thus being about 1.5 to 3 times the size of a red blood cell.

It can be concluded that turbulence is indeed present in the investigated blood pump and that it can be described by Kolmogorov's theory of turbulence. The size of the smallest vortices compares well to the turbulence length scales as found in prosthetic heart valves, for example.

Roller pumps are widely used in procedures involving cardiopulmonary bypass (CPB) due to their ease of operation and maintenance, safety, and cost. Several studies in the literature have compared the use of roller pumps with centrifugal pumps, but the influence of the roller pump adjustment on hemolysis has been poorly explored.

Measurements of hemolysis rates were carried out in 86 patients. The pump was adjusted by the dynamic calibration method, which was performed by an auxiliary device, and the patients were grouped according to the pump calibration: Group 1 (n = 20) 75 mmHg; Group 2 (n = 24) 150 mmHg; Group 3 (n = 22) 300 mmHg and Group 4 (n = 21) 450 mmHg. The hemolysis rates were measured at 4 different times during CPB (TO: before the surgical procedure; T1: 5 minutes after the start of CPB; T2: 30 minutes of CPB; and T3: 5 minutes after the CPB procedure). Hemolysis rates were calculated between the time intervals T0–T1, T1–T2, and T0–T3.

No difference in hemolysis rates was observed between the groups (p>0.31). During the first 5 minutes of CPB, hemolysis represented 35.5% of the total hemolysis and no significant difference was found between groups (p>0.60).

Calibration of roller pumps by the dynamic method did not influence the hemolysis rates. Additionally, the hemolysis during the first 5 minutes of CPB accounted for ∼1/3 of the total hemolysis.

The purpose of this study was to compare the occurrence of microcracks in teeth prepared with different retreatment systems using microcomputed tomography (micro-CT).

Forty-two freshly extracted mandibular premolar teeth were used. The root canals were instrumented with stainless steel K-files to an apical size of 35/.02 using the balanced-force technique and were obturated using the passive compaction technique. The specimens were divided into 3 experimental groups according to retreatment system used (n = 14): ProTaper Universal retreatment (PTUR), Mtwo retreatment (MTR), or D-RaCe retreatment (D-RC) systems. Each specimen was scanned using a high-resolution micro-CT system before instrumentation, after obturation, and after the removal of the filling material. The images were evaluated, and the presence of microcracks was recorded.

The PTUR system demonstrated the highest percentage, while MTR and D-RC retreatment systems resulted in similar numbers of microcracks.

Clinicians should be aware that all retreatment systems may cause microcracks.