Effects of Thoracic Epidural Anaesthesia on the Serosal Microcirculation of the Human Small Intestine

Background: The effect of thoracic epidural analgesia (TEA) on splanchnic blood flow during abdominal surgery remains unclear. The purpose of this study was to examine whether the hemodynamic effects of TEA resulted in microcirculatory alterations to the intestinal serosa, which was visualized using incident dark-field (IDF) videomicroscopy. Methods: An observational cohort study was performed. In 18 patients, the microcirculation of the intestinal serosa was visualized with IDF. Microcirculatory and hemodynamic measurements were performed prior to (T1) and after administering a bolus of levobupivacaine (T2). If correction of blood pressure was indicated, a third measurement was performed (T3). The following microcirculatory parameters were calculated: microvascular flow index, proportion of perfused vessels, perfused vessel density and total vessel density. Data are presented as median [IQR]. Results: Mean arterial pressure decreased from 73 mmHg (68–83) at T1 to 63 mmHg (±11) at T2 (p = 0.001) with a systolic blood pressure of 114 mmHg (98–128) and 87 (81–97), respectively (p = 0.001). The microcirculatory parameters of the bowel serosa, however, were unaltered. In seven patients, blood pressure was corrected to baseline values from a MAP of 56 mmHg (55–57), while microcirculatory parameters remained constant. Conclusion: We examined the effects of TEA on the intestinal serosal microcirculation during abdominal surgery using IDF imaging for the first time in patients. Regardless of a marked decrease in hemodynamics, microcirculatory parameters of the bowel serosa were not significantly affected. Trial registry number: ClinicalTrials.gov identifier NCT02688946

Can sidestream dark field (SDF) imaging identify subtle microvascular changes of the bowel during colorectal surgery?

Background: Recognition of a non-viable bowel during colorectal surgery is a challenging task for surgeons. Identifying the turning point in serosal microcirculatory deterioration leading up to a non-viable bowel is crucial. The aim of the present study was to determine whether sidestream darkfield (SDF) imaging can detect subtle changes in serosal microcirculation of the sigmoid after vascular transection during colorectal surgery. Methods: A prospective observational clinical study was performed at a single medical centre. All eligible participants underwent laparoscopic sigmoid resection and measurements were taken during the extra-abdominal phase. Microcirculation was measured at the transected bowel and 20 cm proximal to this point. Microcirculatory parameters such as Microvascular Flow Index (MFI), proportion of perfused vessels (PPV), perfused vessel density (PVD), total vessel density (TVD) and the Heterogeneity Index were determined. Data are presented as median (interquartile range) or mean ± standard deviation. Results: A total of 60 SDF images were acquired for 10 patients. Perfusion parameters and perfused vessel density were significantly lower at the transected bowel compared with the non-transected measurements [MFI 2.29 (1.96–2.63) vs 2.96 (2.73–3.00), p = 0.007; PPV 74% (55–83) vs 94% (86–97), p = 0.007; and PVD 7.61 ± 2.99 mm/mm2 versus 10.67 ± 1.48 mm/mm2, p = 0.009]. Total vessel density was similar between the measurement locations. Conclusions: SDF imaging can identify changes of the bowel serosal microcirculation. Significantly lower serosal microcirculatory parameters of the vascular transected bowel was seen compared with the non-transected bowel. The ability of SDF imaging to detect subtle differences holds promise for future research on microvascular cut-off values leading to a non-viable bowel

Interobserver variation in the interpretation of SSEPs in anoxic-ischaemic coma

OBJECTIVE: To study interobserver variation in the interpretation of median nerve SSEPs in patients with anoxic-ischaemic coma. METHODS: SSEPs of 56 consecutive patients with anoxic-ischaemic coma were interpreted independently by 5 experienced clinical neurophysiologists using guidelines derived from a pilot study. Interobserver agreement was expressed as kappa coefficients. RESULTS: Kappa ranged from 0.20 to 0.65 (mean 0.52, SD 0.14). Disagreement was related with noise level and failure to adhere strictly to the guidelines in 15 cases. The presence or absence of N13 and cortical peaks caused disagreement in 5 cases each. For recordings with a noise level of 0.25 microV or more, mean kappa was 0.34; for recordings with a noise level below 0.25 microV mean kappa was 0.74. CONCLUSIONS: Interobserver agreement for SSEPs in anoxic-ischaemic coma was only moderate. Since the noise level strongly influenced interobserver variation, utmost attention should be given to its reduction. If an artefact level over 0.25 microV remains, absence of N20 cannot be judged with sufficient certainty and the SSEP should be repeated at a later stage. SIGNIFICANCE: Because of its moderate interobserver agreement, great care has to be given to accurate recording and interpretation of SSEPs before using the recordings for non-treatment decision

Central motor conduction studies in patients with spinal cord disorders: a review.

Study design:Topical review of the literature.Objectives:The evaluation of patients with myelopathies requires radiological investigations; however, for the correct interpretation of the neuroimaging findings, the functional assessment of corticospinal conduction is helpful or even mandatory in many conditions. The objective of this review article was to assess the utility of the motor evoked potentials ( MEPs) in diagnosis and management of the most frequent spinal cord disorders.Setting:Salzburg ( Austria) and Merano ( Italy).Methods:A MEDLINE search was performed using following terms: 'motor evoked potentials', 'transcranial magnetic stimulation', 'central motor conduction', 'compressive myelopathy', 'spinal cord infarction', 'spinal cord injury', 'syringomyelia', 'myelitis', 'hereditary spastic paraparesis', 'subacute combined degeneration' and 'hepatic myelopathy'.Results:Central motor conduction abnormalities can be detected also in the absence of neuroradiological abnormalities-for example, in patients with subacute combined degeneration or hepatic myelopathy. In the most frequent patients with compressive myelopathies, MEPs were found to be very helpful in determining the functional significance of neuroimaging findings. MEP recording can supplement clinical examination and neuroimaging findings also in the assessment of the spinal cord injury level. In patients with spinal cord infarction, the MEP study can demonstrate spinal involvement even when radiological evidence for spinal cord damage is absent or equivocal, thus allowing an important early diagnosis.Conclusion:MEPs represent a highly sensitive and accurate diagnostic tool in many different spinal cord disorders. MEPs can also be useful in follow-up evaluation of motor function during treatment and rehabilitation