In eleven patients (median age of 47 [range 20-71], 8 male and 3 female). There was a linear relationship between ICP and non-invasive estimators of ICP (nICP) with optic nerve sheath diameter ultrasonography (ONSD) (R = 0.53 [p < 0.0001]), JVP (R = 0.38 [p < 0.001]) and transcranial Doppler ultrasonography (TCD) (R = 0.30 [p < 0.01]). The ability to predict intracranial hypertension was highest for ONSD and TCD (AUC = 0.96 [95% CI: 0.90-1.00] and AUC = 0.91 [95% CI: 0.83-1.00], respectively). Jugular venous bulb pressure (JVP). presented the weakest prediction ability (AUC = 0.75 [95% CI: 0.56-0.94]).
ONSD and TCD methods demonstrated agreement with invasively-monitored ICP, suggesting their potential roles in the detection of intracranial hypertension in hypoxic ischaemic brain injury (HIBI) after cardiac arrest 1).
A prospective observational study was performed using convenience sample of 41 adult neurosurgical patients treated in neurosurgical intensive care unit with invasive intracranial pressure monitoring placed in-situ as part of their clinical care. Portable SonoSite ultrasound machine with 7 MHz linear probe were used to measure optic nerve sheath diameter using the standard technique. Simultaneous ICP readings were obtained directly from the invasive monitoring.
Seventy-five measurements were performed on 41 patients. The non-parametric Spearman correlation test revealed a significant correlation at the 0.01 level between the ICP and ONSD value, with correlation coefficient of 0.820. The receiver operating characteristic curve generated an area under the curve with the value of 0.964, and with standard error of 0.22. From the receiver operating characteristic curve, we found that the ONSD value of 5.205 mm is 95.8% sensitive and 80.4% specific in detecting raised ICP.
ONSD value of 5.205 is sensitive and specific in detecting raised ICP. Bedside ultrasound measurement of ONSD is readily learned, and is reproducible and reliable in predicting raised ICP. This non-invasive technique can be a useful adjunct to the current invasive intracranial catheter monitoring, and has wide potential clinical applications in district hospitals, emergency departments and intensive care units 2).