Correlation of the epidural space measured intraoperatively and estimated by MRI or US: an observational study

Cantürk, Mehmet; Kocaoğlu, Nazan; Hakki, Meltem

doi:10.1016/j.bjane.2020.06.003

Brasil

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Clinical Research • Rev. Bras. Anestesiol. 70 (3) • May-Jun 2020 • https://doi.org/10.1016/j.bjane.2020.06.003 linkcopy

Correlation of the epidural space measured intraoperatively and estimated by MRI or US: an observational study

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Background and objectives: To assess the agreement between the epidural depth measured from the surgical site with the epidural depths estimated with magnetic resonance imaging (MRI) and ultrasound scanning.

Methods: Fifty patients of either sex, scheduled for L4‒5 lumbar disc surgery under general anesthesia were enrolled in this prospective observational study, and the results of 49 patients were analyzed. The actual epidural depth was measured from the surgical site with a sterile surgical scale. The MRI-derived epidural depth was measured from the MRI scan. The ultrasound estimated epidural depth was measured from the ultrasound image obtained just before surgery.

Results: The mean epidural depth measured from the surgical site was 53.80 ± 7.67 mm, the mean MRI-derived epidural depth was 54.06 ± 7.36 mm, and the ultrasound-estimated epidural depth was 53.77 ± 7.94 mm. The correlation between the epidural depth measured from the surgical site and MRI-derived epidural depth was 0.989 (r² = 0.979, p < 0.001), and the corresponding correlation with the ultrasound-estimated epidural depth was 0.990 (r² = 0.980, p < 0.001).

Conclusions: Both ultrasound-estimated epidural depth and MRI-derived epidural depth have a strong correlation with the epidural depth measured from the surgical site. Preprocedural MRI-derived estimates of epidural depth are slightly deeper than the epidural depth measured from the surgical site, and the ultrasound estimated epidural depths are somewhat shallower. Although both radiologic imaging techniques provided reliable preprocedural estimates of the actual epidural depth, the loss of resistance technique cannot be discarded while inserting epidural needles.

KEYWORDS Epidural; Anesthesia; Ultrasound; Magnetic resonance imaging; Intraoperative

STROBE Statement - checklist of items that should be included in reports of observational studies
	Item nº	Recommendation	Page nº
Title and abstract	1	(a) Indicate the study's design with a commonly used term in the title or the abstract	1
Title and abstract	1	(b) Provide in the abstract an informative and balanced summary of what was done and what was found	1-2
Introduction
Background/Rationale	2	Explain the scientific background and rationale for the investigation being reported	3
Objectives	3	State specific objectives, including any prespecified hypotheses	3
Methods
Study design	4	Present key elements of study design early in the paper	4
Setting	5	Describe the setting, locations, and relevant dates, including periods of recruitment, exposure, follow-up, and data collection	4-6
Participants	6	(a) Cohort study - Give the eligibility criteria, and the sources and methods of selection of participants. Describe methods of follow-up Case-control study - Give the eligibility criteria, and the sources and methods of case ascertainment and control selection. Give the rationale for the choice of cases and controls Cross-sectional study - Give the eligibility criteria, and the sources and methods of selection of participants	4
Participants		(b) Cohort study - For matched studies, give matching criteria and number of exposed and unexposed Case-control study - For matched studies, give matching criteria and the number of controls per case
Variables	7	Clearly define all outcomes, exposures, predictors, potential Confounders, and effect modifiers. Give diagnostic criteria, if applicable	3
Data sources/measurement	8^a a Give information separately for cases and controls in case-control studies and, if applicable, for exposed and unexposed groupsin cohort and cross-sectional studies.	For each variable of interest, give sources of data and details of methods of assessment (measurement). Describe comparability of assessment methods if there is more than one group	4-6
Bias	9	Describe any efforts to address potential sources of bias	6
Study size	10	Explain how the study size was arrived at	7
Quantitative variables	11	Explain how quantitative variables were handled in the analyses. If applicable, describe which groupings were chosen and why	6
Statistical methods	12	(a) Describe all statistical methods, including those used to control for confounding	6
		(b) Describe any methods used to examine subgroups and interactions	6
		(c) Explain how missing data were addressed	8
		(d) Cohort study - If applicable, explain how loss to follow-up was addressed Case-control study - If applicable, explain how matching of cases and controls was addressed Cross-sectional study - If applicable, describe analytical methods taking account of sampling strategy	6
		(e) Describe any sensitivity analyses	6
Results
Participants	13^a a Give information separately for cases and controls in case-control studies and, if applicable, for exposed and unexposed groupsin cohort and cross-sectional studies.	(a) Report numbers of individuals at each stage of study - eg numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analysed	8
		(b) Give reasons for non-participation at each stage	8
		(c) Consider use of a flow diagram
Descriptive data	14^a a Give information separately for cases and controls in case-control studies and, if applicable, for exposed and unexposed groupsin cohort and cross-sectional studies.	(a) Give characteristics of study participants (eg demographic, clinical, social) and information on exposures and potential Confounders
		(b) Indicate number of participants with missing data for each variable of interest	8
		(c) Cohort study - Summarise follow-up time (eg, average and total amount)
Outcome data	15^a a Give information separately for cases and controls in case-control studies and, if applicable, for exposed and unexposed groupsin cohort and cross-sectional studies.	Cohort study - Report numbers of outcome events or summary measures over time
		Case-control study - Report numbers in each exposure category, or summary measures of exposure
		Cross-sectional study - Report numbers of outcome events or summary measures	8
Main results	16	(a) Give unadjusted estimates and, if applicable, Confounder- adjusted estimates and their precision (eg, 95% confidence interval). Make clear which Confounders were adjusted for and why they were included	8
		(b) Report category boundaries when continuous variables were categorized
		(c) If relevant, consider translating estimates of relative risk into absolute risk for a meaningful time period
Other analyses	17	Report other analyses done - eg analyses of subgroups and interactions, and sensitivity analyses	8
Discussion
Key results	18	Summarise key results with reference to study objectives	9-11
Limitations	19	Discuss limitations of the study, taking into account sources of potential bias or imprecision. Discuss both direction and magnitude of any potential bias	10
Interpretation	20	Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from similar studies, and other relevant evidence	10
Generalisability	21	Discuss the generalisability (external validity) of the study results	11
Other information
Funding	22	Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based	11

Patient characteristics	Results
ASA-PS I/II/III (n)	19/22/8
Gender M/F (n)	24/25
Age (y)	47.61 ± 13.92
Weight (kg)	82.11 ± 12.58
Height (cm)	167.27 ± 8.67
BMI (kg.m^-2)	29.51 ± 5.18
ED/US (mm)	53.77 ± 7.94
ED/MRI (mm)	54.06 ± 7.36
ED/AC (mm)	53.80 ± 7.67

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Sociedade Brasileira de Anestesiologia R. Professor Alfredo Gomes, 36, 22251-080 Botafogo RJ Brasil, Tel: +55 21 2537-8100, Fax: +55 21 2537-8188 - Campinas - SP - Brazil
E-mail: bjan@sbahq.org

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Give information separately for cases and controls in case-control studies and, if applicable, for exposed and unexposed groupsin cohort and cross-sectional studies.