The effect of supplemental oxygen on perioperative brain natriuretic peptide concentration in cardiac risk patients - a protocol for a prosprective randomized clinical trial.

BACKGROUND: Elevated postoperative N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations are predictive for cardiac adverse events in noncardiac surgery. Studies indicate that supplemental oxygen decreases sympathetic nerve activity and might, therefore, improve cardiovascular function. Thus, we will test the effect of perioperative supplemental oxygen administration on NT-proBNP release after surgery. METHODS/DESIGN: We will conduct a single-center, double-blinded, randomized trial at the Medical University of Vienna, including 260 patients with increased cardiac risk factors undergoing moderate- to high-risk noncardiac surgery. Patients will be randomly assigned to receive 80% versus 30% oxygen during surgery and for 2 h postoperatively. The primary outcome will be the difference in maximum NT-proBNP release after surgery. As secondary outcomes we will assess the effect of supplemental oxygen on postoperative maximum troponin T concentration, oxidation-reduction potential, von Willebrand factor concentration and perioperative fluid requirements. We will perform outcome measurements 2 h after surgery, on postoperative day 1 and on postoperative day 3. The NT-proBNP concentration and the oxidation-reduction potential will also be measured within 72 h before discharge. DISCUSSION: Our trial should determine whether perioperative supplemental oxygen administration will reduce the postoperative release of NT-proBNP in patients with preoperative increased cardiovascular risk factors undergoing noncardiac surgery. TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT03366857. Registered on 8th December 2017.

High-Resolution Ultrasonography of the Transverse Cervical Nerve.

The transverse cervical nerve (TCN) is a superficial cutaneous branch of the cervical plexus that innervates the skin of the anterolateral neck. Therefore, it is exposed to injury in anterolateral cervical surgery, which can cause neuropathic pain. To provide a method with which to relieve patients' pain, this study aimed to evaluate the possibility of visualization, diagnostic assessment and blockade of the TCN with high-resolution ultrasound (HRUS). HRUS with high-frequency probes (15-22 MHz), guided ink-marking and consecutive dissection on both sides in nine fresh cadaver necks (n = 18) was conducted. On both sides of 20 healthy volunteers (n = 40), the distances between the greater auricular nerve (GAN) and the TCN at the posterior border of the sternocleidomastoid muscle were measured. Finally, cases referred to HRUS examinations because suspected TCN lesions were assessed. The TCN was visible in all anatomic specimens and in healthy volunteers. Dissection confirmed HRUS findings in all anatomic specimens (100%). In healthy volunteers, the mean distance between the GAN and the TCN was 10.42 ± 3.20 mm. The median visibility, rated on a five-point Likert scale, was four, reflecting good diagnostic quality. There were six patients with visible abnormalities on HRUS. This study confirmed the reliable visualization of the TCN with HRUS in anatomic specimens, healthy volunteers and patients.

High-Resolution Axonal Bundle (Fascicle) Assessment and Triple-Echo Steady-State T2 Mapping of the Median Nerve at 7 T: Preliminary Experience.

OBJECTIVES: The aims of this preliminary study were to determine the number of axonal bundles (fascicles) in the median nerve, using a high-resolution, proton density (PD)-turbo spin echo (TSE) fat suppression sequence, and to determine normative T2 values, measured by triple-echo steady state, of the median nerve in healthy volunteers and in patients with idiopathic carpal tunnel syndrome (CTS), at 7 T. MATERIALS AND METHODS: This prospective study was approved by the local ethics committee and conducted between March 2014 and January 2015. All study participants gave written informed consent. Six healthy volunteers (30 ± 12 years) and 5 patients with CTS (44 ± 16 years) were included. Measurements were performed on both wrists in all volunteers and on the affected wrist in patients (3 right, 2 left). Based on 5-point scales, 2 readers assessed image quality (1, very poor; 5, very good) and the presence of artifacts that might have a possible influence on fascicle determination (1, severe artifacts; 5, no artifacts) and counted the number of fascicles independently on the PD-TSE sequences. Furthermore, T2 values by region of interest analysis were assessed. Student t tests, a hierarchic linear model, and intraclass correlation coefficients (ICCs) were used for statistical analysis. RESULTS: Proton density-TSE image quality and artifacts revealed a median of 5 in healthy volunteers and 4 in patients with CTS for both readers. Fascicle count of the median nerve ranged from 13 to 23 in all subjects, with an ICC of 0.87 (95% confidence interval [CI], 0.67-0.95). T2 values were significantly higher (P = 0.023) in patients (24.27 ± 0.97 milliseconds [95% CI, 22.19-26.38]) compared with healthy volunteers (21.01 ± 0.65 milliseconds [95% CI, 19.61-22.41]). The ICC for all T2 values was 0.97 (95% CI, 0.96-0.98). CONCLUSIONS: This study shows the possibility of fascicle determination of the median nerve in healthy volunteers and patients with CTS (although probably less accurately) with high-resolution 7 T magnetic resonance imaging, as well as significantly higher T2 values in patients with CTS, which seems to be associated with pathophysiological nerve changes.