Abstract
BackgroundUnexplained coma after critical illness can be multifactorial. We evaluated the diagnostic ability of bedside Optic Nerve Sheath Diameter [ONSD] as a screening test for non-traumatic radiographic cerebral edema.MethodsIn a prospective study, mixed medical-surgical intensive care units [ICU] patients with non-traumatic coma [GCS < 9] underwent bedside ultrasonographic ONSD measurements. Non-traumatic radiographic cerebral edema [NTRCE] was defined as > 5 mm midline shift, cisternal, sulcal effacement, or hydrocephalus on CT.ResultsNTRCE was identified in 31 of 102 patients [30.4 %]. The area under the ROC curve for detecting radiographic edema by ONSD was 0.785 [95 % CI 0.695–0.874, p <0.001]. ONSD diameter of 0.57 cm was found to be the best cutoff threshold with a sensitivity 84 % and specificity 71 %, AUC 0.785 [95 % CI 0.695–0.874, p <0.001]. Using ONSD as a bedside test increased the post-test odds ratio [OR] for NTRCE by 2.89 times [positive likelihood ratio], whereas post-test OR for NTRCE decreased markedly given a negative ONSD test [ONSD measurement less than 0.57 cm]; negative likelihood ratio 0.22.ConclusionsThe use of ONSD as a bedside test in patients with non-traumatic coma has diagnostic value in identifying patients with non-traumatic radiographic cerebral edema.
Highlights
Unexplained coma after critical illness can be multifactorial
Patients who were admitted with decompensated liver cirrhosis, were managed when they continued to remain comatose (GCS
Non-traumatic radiographic cerebral edema was confirmed by CT scanning in in 30 % [31 patients]
Summary
We evaluated the diagnostic ability of bedside Optic Nerve Sheath Diameter [ONSD] as a screening test for non-traumatic radiographic cerebral edema. Delayed elimination of sedatives and metabolic factors are considered as explanations for unexplained coma in intensive care unit [ICU] patients. Most patients with non-traumatic coma do not have direct intracranial pressure monitoring, either due to coagulopathy or because it is not routinely recommended. A reliable bedside screening test would be extremely useful to detect non-traumatic radiographic cerebral edema and thereby stratify patients that require urgent diagnostic. The optic nerve attaches to the globe posteriorly and is wrapped in a sheath that contains cerebrospinal fluid. The optic nerve sheath is contiguous with the dura mater and has a trabeculated arachnoid space through which cerebrospinal fluid slowly percolates.
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