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Published on: September 13, 2014
Noninvasive Intracranial Pressure Assessment in Acute Liver Failure
Venkatakrishna Rajajee1,2, Craig A Williamson3,4, Robert J Fontana5
1Department of Neurosurgery, University of Michigan, Taubman Health Care Center 3522, SPC 5338, 1500 East Medical Center Drive, Ann Arbor, MI, 48109-5338, USA. vrajajee@yahoo.com.
Insights
Noninvasive ultrasound measures like optic nerve sheath diameter and middle cerebral artery pulsatility index do not reliably detect elevated intracranial pressure in acute liver failure. However, ICP estimated from transcranial Doppler flow velocities shows promise for detecting increased intracranial pressure in ALF patients.
Area of Science:
- Neurology
- Hepatology
- Critical Care Medicine
Background:
- Elevated intracranial pressure (ICP) is a critical factor in mortality following acute liver failure (ALF).
- Invasive ICP monitoring (IICPM) is accurate but carries bleeding risks in ALF patients due to coagulopathy.
- Noninvasive methods are needed to assess ICP in ALF.
Purpose of the Study:
- To evaluate the accuracy of three noninvasive ultrasound-based measures for detecting elevated ICP in ALF patients.
- To assess optic nerve sheath diameter (ONSD) via optic nerve ultrasound (ONUS).
- To assess middle cerebral artery pulsatility index (PI) via transcranial Doppler (TCD) and ICP calculated from TCD flow velocities (ICPtcd) using the estimated cerebral perfusion pressure (CPPe) technique.
Main Methods:
- Retrospective study of consecutive ALF patients undergoing IICPM and noninvasive measurements.
- Receiver operating characteristic (ROC) curves were used to assess the ability of ONSD, TCD-PI, and ICPtcd to detect ICP > 20 mmHg.
- Area under the curve (AUC) was calculated to evaluate diagnostic accuracy.
Main Results:
- Of 41 ALF patients, 27 underwent IICPM. ONSD (AUC=0.59) and TCD-PI (AUC=0.55) did not reliably detect elevated ICP.
- ICPtcd demonstrated significant accuracy in detecting elevated ICP (AUC=0.90, p<0.0001).
- None of the noninvasive measures predicted in-hospital mortality.
Conclusions:
- ONSD and TCD-PI are not reliable for detecting elevated ICP in ALF patients.
- ICPtcd, derived from the TCD CPPe technique, shows potential for identifying concurrent ICP elevation.
- Further research with larger cohorts is warranted to validate ICPtcd in ALF.
Background:
Elevated intracranial pressure (ICP) is an important cause of death following acute liver failure (ALF). While invasive ICP monitoring (IICPM) is most accurate, the presence of coagulopathy increases bleeding risk in ALF. Our objective was to evaluate the accuracy of three noninvasive ultrasound-based measures for the detection of concurrent ICP elevation in ALF-optic nerve sheath diameter (ONSD) using optic nerve ultrasound (ONUS); middle cerebral artery pulsatility index (PI) on transcranial Doppler (TCD); and ICP calculated from TCD flow velocities (ICPtcd) using the estimated cerebral perfusion pressure (CPPe) technique.
Methods:
In this retrospective study, consecutive ALF patients admitted over a 6-year period who underwent IICPM as well as measurement of ONSD, TCD-PI or ICPtcd were included. ONSD was measured offline by a blinded investigator from deidentified videos. The ability of highest ONSD, TCD-PI, and ICPtcd to detect concurrent invasive ICP > 20 mmHg was assessed using receiver operating characteristic (ROC) curves. The ROC area under the curve (AUC) was calculated with 95% confidence interval (95% CI) and evaluated against the null hypothesis of AUC = 0.5. Noninvasive measures were also evaluated as predictors of in-hospital death.
Results:
Forty-one ALF patients were admitted during the study period. In total, 27 (66%) underwent IICPM, of these, 23 underwent ONUS and 21 underwent TCD. Eleven out of 23 (48%) patients died (two from intracranial hypertension). Results of ROC analysis for detection of concurrent ICP > 20 mmHg were as follows: ONSD AUC = 0.59 (95% CI 0.37-0.79, p = 0.54); TCD-PI AUC = 0.55 (95% CI 0.34-0.75, p = 0.70); and ICPtcd AUC = 0.90 (0.72-0.98, p < 0.0001). None of the noninvasive measures were significant predictors of death.
Conclusions:
In patients with ALF, neither ONSD nor TCD-PI reliably detected concurrent ICP elevation on invasive monitoring. Estimation of ICP (ICPtcd) using the TCD CPPe technique was associated with concurrent ICP elevation. Additional studies of TCD CPPe in larger numbers of ALF patients may prove worthwhile.
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