Assessing Cerebrovascular Hemodynamics Using Transcranial Doppler in Patients with Mechanical Circulatory Support Devices.

BACKGROUND AND PURPOSE: Mechanical circulatory support (MCS) devices are commonly used in heart failure patients. These devices carry risk for presumably embolic and additionally hemorrhagic stroke. Alterations in blood flow play a key role in stroke pathophysiology, and we aimed to learn more about hemodynamic compromise. In this study, we used transcranial Doppler (TCD) ultrasound to define hemodynamics of commonly used nonpulsatile MCS devices, as well as pulsatile devices, with special attention to the total artificial heart (TAH). METHODS: From 2/2013 through 12/2016, we prospectively enrolled patients with MCS who underwent TCD imaging. We analyzed TCD parameters, including peak systolic velocity, end-diastolic velocity, pulsatility indices (PIs), and number of high-intensity transient signals. Waveform morphologies were compared between various MCS devices. RESULTS: We performed 132 TCD studies in 86 MCS patients. Waveforms in patients supported by venoarterial-extracorporeal membrane oxygenation demonstrated continuous flow without clear systolic peaks with an average (±SD) PI of .43 (±.2). PIs were low in patients with continuous-flow left ventricular assist devices with a mean PI of .32 (±.13). Impella patients had morphologically distinct pulsatile waveforms and a higher mean PI of .65 (±.24). In intra-arterial balloon pump patients, mean PI was 1.01 (±.16) and diastolic upstrokes were pronounced. In TAH patients, mean middle cerebral artery velocity of 79.69 (±32.33) cm/seconds and PI of .74 (±.14) approached normal values. CONCLUSION: TCD can detect characteristic waveforms in patients supported by various MCS devices. These device-specific TCD patterns are recognizable and reproducible.

Paradoxical cerebrovascular hemodynamic changes with nicardipine.

OBJECTIVE Intravenous nicardipine is commonly used for blood pressure reduction in patients with acute stroke. However, few studies have described its effects on cerebrovascular hemodynamics as measured by transcranial Doppler (TCD) waveform analysis and pulsatility index (PI). In this study, the authors report examples of a consistent but paradoxical finding associated with nicardipine that suggests intracranial vasoconstriction, contrary to what is expected from a vasodilator. METHODS The data presented are from a convenience sample of patients who underwent TCD monitoring before, after, or during nicardipine administration. In each case, TCD waveform morphologies and PIs were compared. RESULTS The TCD waveforms during nicardipine infusion are characterized by a prominent systolic peak and dicrotic notch. Systolic deceleration was more pronounced and PIs were significantly elevated in patients who were on nicardipine (p < 0.001). This finding was not evident when patients were not on nicardipine. CONCLUSIONS This study provides the first evidence of paradoxical intracranial vasoconstriction associated with intravenous nicardipine. In the authors' experience, this finding is consistently encountered in the vast majority of patients who are treated with intravenous nicardipine, and is contradictory to what is expected from a vasodilator. Future studies are needed to confirm this finding in larger populations and diverse clinical settings and to examine mechanisms that explain this phenomenon.

The Simplest Idea Is the Best Idea.

A collaborative approach was used to ascertain an appropriate stimulus for the patients to remember their stroke-specific education. The stroke education had to stand out amidst the myriad of papers and folders patients are bombarded with in the hospital. The team came up with the simple idea of using a bright red folder. When the patients were called, the call center would prompt the patient by saying, "The stroke education was given to you in a bright red folder." Before the implementation of the red folders, only 81.5% of the patients remembered receiving stroke education. After the implementation of the red folders, 96.8% remembered receiving stroke education. The principle of Occam's razor proved to be correct in our study. A very simple idea such as changing the color of the folders to bright red proved to have very meaningful results.

Adult-onset glutaric aciduria type I presenting with white matter abnormalities and subependymal nodules.

A 55-year-old female presented with a 6-year history of paresthesias, incontinence, spasticity, and gait abnormalities. Neuroimaging revealed white matter abnormalities associated with subependymal nodules. Biochemical evaluation noted increased serum C5-DC glutarylcarnitines and urine glutaric and 3-hydroxyglutaric acids. Evaluation of the glutaryl-CoA dehydrogenase (GCDH) gene revealed compound heterozygosity consisting of a novel variant (c.1219C>G; p.Leu407Val) and pathogenic mutation (c.848delT; p.L283fs). Together, these results were consistent with a diagnosis of adult-onset type I glutaric aciduria.

Quantifying and comparing torsional strains after olecranon plating.

PURPOSE: Any torsion experienced at a fracture site will directly translate into shearing forces and has been regarded as detrimental to healing. The purpose of this study was to determine which plating system currently on the market controls torsional forces about comminuted olecranon fractures most effectively. METHODS: Five olecranon plates (Acumed, Synthes-SS, Synthes-Ti, ITS/US Implants and Zimmer) were implanted to stabilise a simulated comminuted fracture pattern in 50 fresh-frozen, cadaveric elbows. All specimens were evaluated by dual energy X-ray absorptiometry (DXA) scan to determine bone density. Three-dimensional displacement analysis was conducted to assess fragment motion through physiologic cyclic arcs of motion. The specimens were cycled through progressive physiologic loads (0.18-5.6 kg). Movements of the fragments were statistically compared amongst the different implants using one-way analysis of variance (ANOVA) and Tukey Honestly Significant Difference (HSD) post hoc comparisons with a critical significance level of α=0.05. RESULTS: DXA bone mineral densities (BMDs) ranged from 0.465 to 0.927, with an average of 0.714. The Acumed, Synthes-SS, Synthes-Ti and Zimmer plates allowed <1° of torsion up to 1.6 kg of load. The differences between these plates at this load were not statistically significant. The ITS/US Implants plate, however, allowed significantly more torsion above loads of 2.6 kg (p=0.045) compared with all other plates. The ITS/US Implants plate allowed over 2° of torsion at 2.6 kg (p=0.012), and nearly 3° at 3.6 kg (p=0.045). The Zimmer plate consistently allowed more torsion than the Acumed plate or either of the Synthes plates, but the differences were not statistically significant. CONCLUSION: Regardless of which olecranon plate is used, the authors recommend limiting postoperative rehabilitation loads to below 1.6 kg in an effort to minimise the detrimental effects of torsion on healing. If loads over 1.6 kg are anticipated, the authors recommend the use of the Acumed plate or either of the Synthes plates.

Comparison of olecranon plate fixation in osteoporotic bone: do current technologies and designs make a difference?

OBJECTIVES: The purpose of this study is to determine if recent innovations in olecranon plates have any advantages in stabilizing osteoporotic olecranon fractures. METHODS: Five olecranon plates (Acumed, Synthes-SS, Synthes-Ti, US Implants/ITS, and Zimmer) were implanted to stabilize a simulated comminuted fracture pattern in 30 osteoporotic cadaveric elbows. Specimens were randomized by bone mineral density per dual-energy x-ray absorptiometry scan. Three-dimensional displacement analysis was conducted to assess fragment motion through physiological cyclic arcs of motion and failure loading, which was statistically compared using one-way analysis of variance and Tukey honestly significant difference post hoc comparisons with a critical significance level of α = 0.05. RESULTS: Bone mineral density ranged from 0.546 g/cm to 0.878 g/cm with an average of 0.666 g/cm. All implants limited displacement of the fragments to less than 3 mm until sudden, catastrophic failure as the bone of the proximal fragment pulled away from the implant. The maximum load sustained by all osteoporotic specimens ranged from 1.6 kg to 6.6 kg with an average of 4.4 kg. There was no statistical difference between the groups in terms of cycles survived and maximum loads sustained. CONCLUSIONS: Cyclic physiological loading of osteoporotic olecranon fracture fixation resulted in sudden, catastrophic failure of the bone-implant interface rather than in gradual implant loosening. Recent plate innovations such as locking plates and different screw designs and positions appear to offer no advantages in stabilizing osteoporotic olecranon fractures. Surgeons may be reassured that the current olecranon plates will probably adequately stabilize osteoporotic fractures for early motion in the early postoperative period, but not for heavy activities such as those that involve over 4 kg of resistance.