Intracranial Pressure Readings Research Articles

The Presence of Blood in a Strain Gauge Pressure Transducer Has a Clinical Effect on the Accuracy of Intracranial Pressure Readings.

Patients admitted with cerebral hemorrhage or cerebral edema often undergo external ventricular drain (EVD) placement to monitor and manage intracranial pressure (ICP). A strain gauge transducer accompanies the EVD to convert a pressure signal to an electrical waveform and assign a numeric value to the ICP. This study explored ICP accuracy in the presence of blood and other viscous fluid contaminates in the transducer. Preclinical comparative design study. Laboratory setting using two Natus EVDs, two strain gauge transducers, and a sealed pressure chamber. No human subjects or animal models were used. A control transducer primed with saline was compared with an investigational transducer primed with blood or with saline/glycerol mixtures in mass:mass ratios of 25%, 50%, 75%, and 100% glycerol. Volume in a sealed chamber was manipulated to reflect changes in ICP to explore the impact of contaminates on pressure measurement. From 90 paired observations, ICP readings were statistically significantly different between the control (saline) and experimental (glycerol or blood) transducers. The time to a stable pressure reading was significantly different for saline vs. 25% glycerol (< 0.0005), 50% glycerol (< 0.005), 75% glycerol (< 0.0001), 100% glycerol (< 0.0005), and blood (< 0.0005). A difference in resting stable pressure was observed for saline vs. blood primed transducers (0.041). There are statistically significant and clinically relevant differences in time to a stable pressure reading when contaminates are introduced into a closed drainage system. Changing a transducer based on the presence of blood contaminate should be considered to improve accuracy but must be weighed against the risk of introducing infection.

Exploration of the relationship between partial pressure of brain tissue oxygen and intracranial pressure

IntroductionPartial pressure of brain tissue oxygen (PbtO2) has been shown to be a safe an effective monitoring modality to compliment intracranial pressure (ICP) monitoring. It is related to metabolic activity, disease severity and mortality. Research questionUnderstanding the complex relationship between PbtO2 and ICP for patients with traumatic brain injury will enable better clinical decision making beyond simple threshold treatment strategies. Material and methodsPatients with PbtO2 monitoring were identified from the BrainIT database, a multi-centre dataset, containing minute by minute PbtO2 and ICP readings. Missing data was imputed and a multi-level log-normal regression model with a compound symmetry correlation structure was built. This accounted for any increased correlation due to the repeated measurements. The model was adjusted for mean arterial pressure and the partial pressure of carbon dioxide. Non-linearity was assessed using analysis of deviance and trends using expected marginal means. Results11 subjects with over 82,000 readings were included. They had a median age of 38 (IQR: 37–47), 73% were male, a median length of stay of 11.8 (IQR: 6.6–19.7) days and a median extended Glasgow outcome scale of 7.00 (IQR: 5–8).There is a statistically significant (p < 0.001) non-linear effect of ICP on PbtO2. With an overall increase in PbtO2 of 5.2% (95% CI 4%–6.4%, p < 0.001) for a 10 mmHg increase in ICP below 22 mmHg and a decrease of 5.5% (95% CI 2.7%–8.3%, p=<0.001) in PbtO2 for a 10 mmHg increase in ICP above 22 mmHg. As well as a decrease of 40.9% (95% CI 2.3%–64.3%, p = 0.040) in PbtO2 per day in the intensive care unit. Discussion and conclusionThis model demonstrates that there is a significant non-linear relationship between ICP and PbtO2, however, this is a small heterogeneous cohort and further validation will be required.

Intracranial pressure monitoring for severe traumatic brain injury: A retrospective study of 273 consecutive patients.

Intracranial pressure (ICP) monitoring is essential in severe traumatic brain injury (sTBI) cases; yet, the frequency of high ICP occurrences remains debated. This study presents a 9-year analysis of ICP monitoring using intraventricular catheters among sTBI patients. A retrospective review of 1760 sTBI patients (Glasgow Coma Score <9) admitted between January 2011 and December 2019 was conducted. Of these, 280 patients meeting monitoring criteria were included based on Brain Trauma Foundation (BTF) Guidelines. ICP was monitored using intraventricular catheters through right frontal burr holes. Initial ICP readings were recorded intraoperatively, followed by continuous monitoring. Patients with ICP >20 mmHg for 10-15 min during 72 h were categorized with high ICP. Data collected included demographics, computed tomography (CT) findings, intra- and post-operative ICP, and complications. Of 273 patients, 228 were male and 45 females, aged 18-80 (71.30% aged 18-45). Traffic accidents were the primary cause (90.48%). Fifty-two-point seventy-five percent experienced high ICP, correlating significantly with subdural hematoma (P < 0.001), intraventricular hemorrhage (P < 0.013), and compressed basal cisterns (P = 0.046) on initial CT. Twenty patients (7.3%) developed meningitis. Lower mortality rates and improved outcomes were observed in the low ICP group across discharge 3-and 6-month follow-ups. Adherence to BTF guidelines yielded a 52.75% high ICP rate. Significant correlations were found between high ICP and specific CT abnormalities. This study underscores the benefits of ICP monitoring in selected sTBI cases, suggesting a need to review criteria for initiating monitoring protocols.

The role of intracranial pressure variability as a predictor of intracranial hypertension and mortality in critically ill patients.

Intracranial pressure (ICP) monitoring is a widely utilized and essential tool for tracking neurosurgical patients, but there are limitations to the use of a solely ICP-based paradigm for guiding management. It has been suggested that ICP variability (ICPV), in addition to mean ICP, may be a useful predictor of neurological outcomes, as it represents an indirect measure of intact cerebral pressure autoregulation. However, the current literature regarding the applicability of ICPV shows conflicting associations between ICPV and mortality. Thus, the authors aimed to investigate the effect of ICPV on intracranial hypertensive episodes and mortality using the eICU Collaborative Research Database version 2.0. The authors extracted from the eICU database 1,815,676 ICP readings from 868 patients with neurosurgical conditions. ICPV was computed using two methods: the rolling standard deviation (RSD) and the absolute deviation from the rolling mean (DRM). An episode of intracranial hypertension was defined as at least 25 minutes of ICP > 22 mm Hg in any 30-minute window. The effects of mean ICPV on intracranial hypertension and mortality were computed using multivariate logistic regression. A recurrent neural network with long short-term memory was used for time-series predictions of ICP and ICPV to prognosticate future episodes of intracranial hypertension. A higher mean ICPV was significantly associated with intracranial hypertension using both ICPV definitions (RSD: aOR 2.82, 95% CI 2.07-3.90, p < 0.001; DRM: aOR 3.93, 95% CI 2.77-5.69, p < 0.001). ICPV was significantly associated with mortality in patients with intracranial hypertension (RSD: aOR 1.28, 95% CI 1.04-1.61, p = 0.026, DRM: aOR 1.39, 95% CI 1.10-1.79, p = 0.007). In the machine learning models, both definitions of ICPV achieved similarly good results, with the best F1 score of 0.685 ± 0.026 and an area under the curve of 0.980 ± 0.003 achieved with the DRM definition over 20 minutes. ICPV may be useful as an adjunct for the prognostication of intracranial hypertensive episodes and mortality in neurosurgical critical care as part of neuromonitoring. Further research on predicting future intracranial hypertensive episodes with ICPV may help clinicians react expediently to ICP changes in patients.

Comparative study between ultrasound guided coronal versus axial optic nerve sheath diameter measurement in patients at risk of increased intracranial pressure

Background: This work intended to contrast the effectiveness as well as precision of ultrasound guided coronal versus axial optic nerve sheath diameter (ONSD) measurement in patients at danger of elevated intracranial pressure (ICP). The optic nerve is a tubular structure of approximately 5 cm in Length, in which its intraorbital segment is evaluable sonographically. Methods: The 70 patients in this prospective, randomised, double-blinded trial spanned in age from 18 to 60 and had moderately to grave traumatic brain injury (TBI) when they were transferred to the intensive care unit (ICU) with a GCS of 3-12. There were two groups of patients: Patients in Group A do not exhibit elevated ICP readings on brain CT scans. Group B: Patients who had elevated ICP found on a brain CT scan. Results: There were non-significant higher mean coronal ONSD in comparison to mean axial ONSD in both groups. significant higher mean ONSD and mean axial and coronal ONSD in patients of group B. The Glasgow Coma Scale (GCS) was considerably lower in group B patients. In addition, there was a substantial inverse correlation between the mean ONSD, mean coronal and axial ONSD (mm), and the GCS for patients in both categories. Conclusions: In patients with trauma to the brain, monitoring the diameter of the optic nerve sheath with bedside ocular ultrasonography is a beneficial non-invasive way to detect excessive intracranial pressure earlier and correlation via the two methods (axial and coronal) gives us more accurate measurements.

Zeroing a Transducer on an External Ventricular Drain.

BACKGROUND: External ventricular drains (EVDs) are commonly used in severely brain-injured patients to diagnose intracranial hypertension. The accuracy of the intracranial pressure reading is dependent on zeroing the external transducer to air. Recent concern about zeroing techniques has been identified in the neuroscience community. The open method requires removing the nonvented cap, and the closed method requires zeroing through the filter at the top of the burette. This critical appraisal seeks to explore whether zeroing a transducer on an EVD through the filter of the burette provides the same baseline zero as opening the transducer to air. METHODS: Independent searches in CINAHL, PubMed, and Web of Science were conducted using "external ventricular drain* OR EVD AND transducer"; secondary search terms included "zero AND transducer" AND "ventric." RESULTS: Database search produced 1 single observation study and 2 clinical practice guidelines from neuroscience professional organizations. The single observation study provided no evidence of equivalence between the 2 zeroing methods; the 2 clinical practice guidelines reference the open method. The transducer manufacturer's instructions for use direct the clinician to open the transducer to air by removing the nonvented cap. CONCLUSION: The question "Does zeroing the transducer on an EVD through the filter of the burette provide the same baseline zero as opening the transducer to air?" cannot be answered with the results of this appraisal. However, evidence found in the literature does suggest an open method to ensure the most accurate physiological value for treatment decisions.

Non-Invasive Assessment of Intracranial Hypertension in Patients with Traumatic Brain Injury Using Computed Tomography Radiomic Features: A Pilot Study.

This study aimed to assess intracranial hypertension in patients with traumatic brain injury non-invasively using computed tomography (CT) radiomic features. Fifty patients from the primary cohort were enrolled in this study. The clinical data, pre-operative cranial CT images, and initial intracranial pressure readings were collected and used to develop a prediction model. Data of 20 patients from another hospital were used to validate the model. Clinical features including age, sex, midline shift, basilar cistern status, and ventriculocranial ratio were measured. Radiomic features-i.e., 18 first-order and 40 second-order features- were extracted from the CT images. LASSO method was used for features filtration. Multi-variate logistic regression was used to develop three prediction models with clinical (CF model), first-order (FO model), and second-order features (SO model). The SO model achieved the most robust ability to predict intracranial hypertension. Internal validation showed that the C-statistic of the model was 0.811 (95% confidence interval [CI]: 0.691-0.931) with the bootstrapping method. The Hosmer Lemeshow test and calibration curve also showed that the SO model had excellent performance. The external validation results showed a good discrimination with an area under the curve of 0.725 (95% CI: 0.500-0.951). Although the FO model was inferior to the SO model, it had better prediction ability than the CF model. The study shows that the radiomic features analysis, especially second-order features, can be used to evaluate intracranial hypertension non-invasively compared with conventional clinical features, given its potential for clinical practice and further research.

Prediction of Intracranial Hypertension and Brain Tissue Hypoxia Utilizing High-Resolution Data from the BOOST-II Clinical Trial.

The current approach to intracranial hypertension and brain tissue hypoxia is reactive, based on fixed thresholds. We used statistical machine learning on high-frequency intracranial pressure (ICP) and partial brain tissue oxygen tension (PbtO2) data obtained from the BOOST-II trial with the goal of constructing robust quantitative models to predict ICP/PbtO2 crises. We derived the following machine learning models: logistic regression (LR), elastic net, and random forest. We split the data set into 70-30% for training and testing and utilized a discrete-time survival analysis framework and 5-fold hyperparameter optimization strategy for all models. We compared model performances on discrimination between events and non-events of increased ICP or low PbtO2 with the area under the receiver operating characteristic (AUROC) curve. We further analyzed clinical utility through a decision curve analysis (DCA). When considering discrimination, the number of features, and interpretability, we identified the RF model that combined the most recent ICP reading, episode number, and longitudinal trends over the preceding 30 min as the best performing for predicting ICP crisis events within the next 30 min (AUC 0.78). For PbtO2, the LR model utilizing the most recent reading, episode number, and longitudinal trends over the preceding 30 min was the best performing (AUC, 0.84). The DCA showed clinical usefulness for wide risk of thresholds for both ICP and PbtO2 predictions. Acceptable alerting thresholds could range from 20% to 80% depending on a patient-specific assessment of the benefit-risk ratio of a given intervention in response to the alert.

Predictive Values for Time from Transducer Stopcock Closure to Accurate Intracranial Pressure Reading.

When using an external ventricular drain (EVD) to monitor intracranial pressure (ICP), nurses need to know how long to wait after each manipulation of the transducer before the displayed ICP value represents an accurate signal. This study explores ICP signal equilibration time (EqT) under clinical conditions. This was a prospective ex vivo study using a simulated skull, standard EVD tubing, and a strain gauge transducer. All 270 trials simulating 90 combinations of different pressures and common clinical conditions were completed in August 2021. Each trial was recorded on video. Videos were scored using video editing software to obtain the exact start and stop time for each trial. The mean EqT was 44.90 (18.77) seconds. One hundred fifty (55.56%) observations did not reach their expected value within 60s. The longest mean EqTs were noted when blood was present in the EVD tubing (57.67 [8.91] seconds), when air bubbles were in the tubing (57.41 [8.73] seconds), and when EVD tubing was not flat (level) (50.77 [15.43] seconds). An omnibus test comparing mean EqT for conditions with no variables manipulated (30.08 [16.07] seconds) against mean EqT for all others (47.18 [18.13] seconds) found that mean EqTs were significantly different (P < 0.001). Even when no additional variables were introduced, the mean EqTs were ~ 30s. Common clinical variables increase the length of time before a transducer connected to an EVD will provide an accurate reading. Nurses should wait at least 30s after turning the EVD stopcock before assuming ICP value reflects accurate ICP.

Peak Systolic Velocity in Middle Cerebral Artery in Patients with Severe Traumatic Brain Injury as an Indicator of Detrimental Rise in Intracranial Pressure

Background Intracranial pressure (ICP) is the major concern for neurosurgeons while treating patients with severe traumatic brain injury, as any troublesome escalation in intracranial pressure heralds feared complications leading to definite morbidity or even mortality.&#x0D; Objective This study focuses on analyzing the correlation between peak systolic velocity in middle cerebral artery derived from transcranial doppler ultrasonographic spectral analysis and intracranial pressure values derived from invasive intracranial pressure monitoring system in a patient with severe traumatic brain injury.&#x0D; Method A prospective observational study was performed using a convenience sample technique including all adult patients with severe traumatic brain injury who had invasive intracranial monitors placed as part of their clinical care. Transcranial doppler ultrasonography was performed with a 2 MHz linear probe of ACUSON X300 ultrasound system while simultaneous intracranial pressure readings were obtained directly from invasive intracranial pressure monitoring. The association between peak systolic velocity in the middle cerebral artery and invasive intracranial pressure was assessed with Pearson’s correlation coefficient.&#x0D; Result One hundred one transcranial doppler ultrasound spectral analysis was performed on 26 individual patients. The mean age of the population involved in this study is 43.57 years ± S.D. 19.95 (range 18-78 years), with male preponderance in a ratio of 5.5:1. Pearson’s correlation coefficient of peak systolic velocity in middle cerebral artery and intracranial pressure was 0.715 (p &lt; 0.000) demonstrating a significant positive correlation. With further evaluation of area under curve characteristics, peak systolic velocity in middle cerebral artery of 39.6 cm/s yielded the most favorable balance of test characteristics to diagnose elevation of intracranial pressure, with a resulting sensitivity of 82.1% and specificity of 84.4%.&#x0D; Conclusion Peak systolic velocity in middle cerebral artery can be explored further as a dependable screening tool to evaluate intracranial pressure among patients with severe traumatic brain injury in settings with unavailability of invasive intracranial pressure monitoring facilities.

Intracranial Pressure and Cerebral Perfusion Pressure in Large Spontaneous Intracranial Hemorrhage and Impact of Minimally Invasive Surgery

Introduction: We investigated the effect of hematoma volume reduction with minimally invasive surgery (MIS) on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in patients with large spontaneous intracerebral hemorrhage (ICH).Methods:Post-hoc analysis of the Minimally Invasive Surgery Plus Alteplase for Intracerebral Hemorrhage Evacuation (MISTIE III) study, a clinical trial with blinded outcome assessments. The primary outcome was the proportion of ICP readings ≥20 and 30 mmHg, and CPP readings <70 and 60 mm Hg. Secondary outcomes included major disability (modified Rankin scale >3) and mortality at 30 and 365 days. We assessed the relationship between proportion of high ICP and low CPP events and MIS using binomial generalized linear models, and outcomes using multiple logistic regression.Results: Of 499 patients enrolled in MISTIE III, 72 patients had guideline based ICP monitors placed, 34 in the MIS group and 38 in control (no surgery) group. Threshold ICP and CPP events ≥20/ <70 mmHg occurred in 31 (43.1%) and 52 (72.2%) patients respectively. On adjusted analyses, proportion of ICP readings ≥20 and 30 mmHg were significantly lower in the MIS group vs. control group [Odds Ratio (OR) 0.27, 95% Confidence Interval [CI] 0.11–0.63 (p = 0.002); OR = 0.18, 0.04–0.75, p = 0.02], respectively. Proportion of CPP readings <70 and 60 mm Hg were also significantly lower in MIS patients [OR 0.31, 95% CI 0.15–0.63 (p = 0.001); OR 0.30, 95% CI 0.11–0.83 (p = 0.02)], respectively. Higher proportions of CPP readings <70 and 60 mm were significantly associated with short term mortality (p = 0.04), and (p = 0.006), respectively. Long term mortality was significantly associated with higher proportion of time with ICP ≥ 20 (p = 0.04), ICP ≥ 30 (p = 0.04), and CPP <70 mmHg (p = 0.01).Conclusion: Our results are consistent with the hypothesis that surgical reduction of ICH volume decreases proportion of high ICP and low CPP events and that these variables are associated with short- and long-term mortality.

Correlation between Invasive Intracranial Pressure Monitoring and Optic Nerve Sheath Diameter in Patients with Traumatic Brain Injury

Background In management of patients with traumatic brain injury, intracranial pressure holds an important place. Any untoward rise in intracranial pressure portends dreaded complications. Hence, any delay in detecting the issue is considered unacceptable.&#x0D; Objective This study focuses on analyzing the correlation between ultrasound derived optic nerve sheath diameter and intracranial pressure values derived from invasive intracranial pressure monitoring system in a neurosurgical patient with severe traumatic brain injury.&#x0D; Method A prospective observational study was performed using a convenience sample technique including all adult patients with traumatic brain injury who had invasive intracranial monitors placed as part of their clinical care. Ocular ultrasound was performed with 5 - 7.5 MHz linear probe of ACUSON X300 ultrasound system while simultaneous intracranial pressure readings were obtained directly from an invasive intracranial pressure monitoring system. The association between optic nerve sheath diameter and invasive intracranial pressure reading was assessed with the Pearson’s correlation coefficient and a receiver operator characteristic curve was created to determine the optimal optic nerve sheath diameter cutoff to detect intracranial pressure &gt; 15 cm H2O.&#x0D; Result One hundred and fifteen ocular ultrasounds were performed on 30 individual patients. The mean age of the population involved in this study is 42.13 years ± 1.89 with male preponderance in the ratio of 6:1. Pearson’s correlation coefficient of optic nerve sheath diameter and intracranial pressure was found to be 0.844 (p &lt; 0.000) demonstrating a significant positive correlation. The area under the receiver operating characteristic curve was found to be 0.961 (95% confidence interval = 0.93 to 0.99). Based on analysis of the receiver operating characteristic curve, optic nerve sheath diameter &gt; 4.85 mm performed best to detect intracranial pressure &gt; 15 cm H2O with a sensitivity of 93.5% and specificity of 83%.&#x0D; Conclusion Optic nerve sheath diameter is a dependable screening tool to evaluate for elevated intracranial pressure among patients with traumatic nerve injury.

Abstract P447: Intracranial Pressure and Cerebral Perfusion Pressure Monitoring in Spontaneous Intracranial Hemorrhage: A Secondary Analysis of the Mistie III Trial

Introduction: Intracerebral hemorrhage (ICH) management guidelines recommend maintaining intracranial pressure (ICP) &lt;20 and cerebral perfusion pressure (CPP) between 50-70 mmHg. We did subgroup analyses of MISTIE III trial to explore whether minimally invasive surgery (MIS) improves ICP or CPP and whether thresholds are associated with long term outcomes. Methods: MISTIE III was a randomized clinical trial including 499 patients with spontaneous ICH randomized to MIS+Alteplase or standard medical care (SMC). Primary outcomes were any threshold event of ICP &gt;20 and CPP &lt;60/70 mmHg. Secondary outcomes were poor modified Rankin Scale at one year and mortality at 30/365 days. We used multivariable models to investigate factors associated with ICP/CPP events and outcomes. Results: Of 72 patients with ICP monitored for median 92 (72-96) hours, 31 (43.1%) had at least one ICP reading &gt;20 and 52/35 (72.2/34.7%) had at least one CPP reading &lt;70/60 mmHg. Lower intraventricular hemorrhage volume and SMC group were associated with having any ICP threshold event &gt;20 and CPP event &lt;70 mmHg whereas CPP&lt;60 mmHg was associated with end of treatment (EOT) ICH volume, hydrocephalus on diagnostic CT and no prior antiplatelet agent use. On adjusted analyses, percentage of ICP readings &gt;20 were significantly less likely in patients undergoing MIS vs SMC (Coefficient -0.79, 95% Confidence Interval [CI] [(-)1.46-(-)0.11]; p=0.02). Percentage of CPP readings &lt;70 were significantly less frequent in MIS group (Coefficient -1.59 [(-)2.58-(-)0.59]; p=0.002). Patients who underwent successful MIS with EOT ICH volume &lt;15mL also had significantly lower percentage of readings at ICP&lt;20 (p=0.02), and CPP&lt;70 (p=0.05). Lower percentage of CPP readings &lt;60 mmHg was independently associated with lower mortality at 30 and 365 days (p=0.02 and 0.04) and CPP &lt;70 was associated with lower one-year mortality (p=0.04). There were no significant associations with one-year functional outcome. Conclusion: Elevated ICP and inadequate CPP are not infrequent during ICP monitoring for large ICH. Burden of low CPP events predict higher short and long term mortality, but not functional outcomes. CPP may be more significant than ICP. MIS appears to mitigate ICP and CPP threshold events.

Accuracy of Physical Examination and Imaging Findings for the Diagnosis of Elevated Intracranial Pressure.

LR+: 2.0 for pupillary dilation LR+: 2.20 for compression or absence of the basal cisterns on CT LR+: 1.92 for midline shift > 10 mm on CT LR−: 0.84 for pupillary dilation LR−: 0.23 for compression or absence of the basal cisterns on CT LR−: 0.89 for midline shift > 10 mm on CT Elevated intracranial pressure (ICP) is a common but severe complication of several medical and traumatic conditions.1, 2 Prolonged increases in ICP are associated with poor patient outcomes in a variety of conditions, including traumatic brain injury (TBI), spontaneous subarachnoid or intracerebral hemorrhage, space-occupying lesion, meningitis, cerebral infarct, and cerebral edema from hepatic encephalopathy.3-5 Invasive ICP monitoring is the reference standard for cases suspected of increased ICP but is not universally available and has several potential complications, including intracranial infection and hemorrhage.5, 6 Consequently, clinicians must often rely on noninvasive methods for assessing increased ICP. The systematic review and meta-analysis discussed here included all retrospective, prospective observational, and randomized controlled trials of adult patients (age ≥ 16 years) in the emergency department or intensive care unit that assessed physical examination findings, brain computed tomography (CT), ocular nerve sheath diameter on ultrasound, or transcranial Doppler indices.7 The reference standard consisted of either an ICP reading> 20 mm Hg on invasive ICP monitoring or craniectomy with an operative diagnosis of elevated ICP. The primary outcome was the diagnostic accuracy of the aforementioned tests for diagnosing increased ICP. The systematic review identified 40 studies (n = 5,123 patients) who met the inclusion criteria. Twenty-four studies were prospective cohort studies, 15 were retrospective, and one was a randomized controlled trial. Twenty studies included patients with TBI, three subarachnoid hemorrhage, two intracerebral hemorrhage, two hepatic failure, one ischemic stroke, and 12 mixed populations of primary brain injury. Only three physical examination findings (pupillary dilatation, motor posturing, and altered mental status) had adequate relevant studies to allow for a meta-analysis. Table 1 demonstrates the findings associated with elevated ICP. Measuring ocular nerve sheath diameter with ultrasound appeared to have a high discriminatory power with the pooled area under the receiver operating characteristic (AUROC) curve of 0.94 (95% confidence interval [CI] = 0.91 to 0.96). The sensitivity and specificity of the test were dependent on the cutoff used for increased optic nerve sheath in each study, precluding the possibility of meta-analysis to calculate pooled sensitivity and specificity. Authors calculated AUROC values for transcranial doppler pulsatility index (TCD-PI) to detect ICP ≥ 20 mm Hg based on three studies, finding a pooled AUROC value of 0.85 (95% CI = 0.78 to 0.91) with use of combined TCD arterial blood pressure methods. This study has several important limitations. Most of the included studies were relatively small, with only 13 studies enrolling more than 100 people. Additionally, the prevalence varied significantly between studies which may lead to spectrum bias, and evidence quality for findings suggestive of elevated ICP was predominantly low or moderate, with only midline shift > 10 mm on CT associated with high evidence quality. Nearly one-third of the studies were retrospective in nature. There was also significant heterogeneity with regard to the etiology and severity of the associated injuries, with no definition of the search strategy pertaining to the specific etiology of elevated ICP. Clinical signs were evaluated independently, which is not typical of clinical practice, and it is unclear how the diagnostic accuracy would change when using combinations of findings. Moreover, the inclusion of studies with either invasive monitoring or intraoperative diagnosis may lead to misclassification of the target condition in the latter case. Advances in imaging quality may limit the external validity of older studies with regard to current imaging. Furthermore, while 10 studies (1,035 patients) evaluated ocular nerve sheath diameter, the variations in ocular nerve sheath diameter thresholds precluded the ability to perform meta-analyses on this group. Finally, there were limited data on transcranial Doppler with differences in both the parameters assessed between studies. Based on the existing evidence, most findings are insufficiently sensitive or specific for the diagnosis of increased ICP. Therefore, physical examination findings, CT, ocular nerve sheath diameter, and transcranial Doppler do not appear to be reliable in identifying or excluding increased ICP.

Intracranial Hypertension and Cerebral Perfusion Pressure Insults in Adult Hypertensive Intraventricular Hemorrhage: Occurrence and Associations With Outcome.

Elevated intracranial pressure and inadequate cerebral perfusion pressure may contribute to poor outcomes in hypertensive intraventricular hemorrhage. We characterized the occurrence of elevated intracranial pressure and low cerebral perfusion pressure in obstructive intraventricular hemorrhage requiring extraventricular drainage. Prospective observational cohort. ICUs of 73 academic hospitals. Four hundred ninety-nine patients enrolled in the CLEAR III trial, a multicenter, randomized study to determine if extraventricular drainage plus intraventricular alteplase improved outcome versus extraventricular drainage plus saline. Intracranial pressure and cerebral perfusion pressure were recorded every 4 hours, analyzed over a range of thresholds, as single readings or spans (≥ 2) of readings after adjustment for intracerebral hemorrhage severity. Impact on 30- and 180-days modified Rankin Scale scores was assessed, and receiver operating curves were analyzed to identify optimal thresholds. Of 21,954 intracranial pressure readings, median interquartile range 12 mm Hg (8-16), 9.7% were greater than 20 mm Hg and 1.8% were greater than 30 mm Hg. Proportion of intracranial pressure readings from greater than 18 to greater than 30 mm Hg and combined intracranial pressure greater than 20 plus cerebral perfusion pressure less than 70 mm Hg were associated with day-30 mortality and partially mitigated by intraventricular alteplase. Proportion of cerebral perfusion pressure readings from less than 65 to less than 90 mm Hg and intracranial pressure greater than 20 mm Hg in spans were associated with both 30-day mortality and 180-day mortality. Proportion of cerebral perfusion pressure readings from less than 65 to less than 90 mm Hg and combined intracranial pressure greater than 20 plus cerebral perfusion pressure less than 60 mm Hg were associated with poor day-30 modified Rankin Scale, whereas cerebral perfusion pressure less than 65 and less than 75 mm Hg were associated with poor day-180 modified Rankin Scale. Elevated intracranial pressure and inadequate cerebral perfusion pressure are not infrequent during extraventricular drainage for severe intraventricular hemorrhage, and level and duration predict higher short-term mortality and long-term mortality. Burden of low cerebral perfusion pressure was also associated with poor short- and long-term outcomes and may be more significant than intracranial pressure. Adverse consequences of intracranial pressure-time burden and cerebral perfusion pressure-time burden should be tested prospectively as potential thresholds for therapeutic intervention.

Optical pupillometry in traumatic brain injury: neurological pupil index and its relationship with intracranial pressure through significant event analysis

ABSTRACTPrimary Objective: Treatment paradigms for traumatic brain injury (TBI) rely on invasive monitoring of intracranial pressure (ICP) for planning intervention. Optical pupillometry is a non-invasive, objective monitoring method, measuring parameters of pupillary response and displaying a scalar value – a neurological pupil index (NPi). An impaired response on NPi has been tentatively correlated with ICP, through analysis of mean/peak NPi and ICP readings. We sought to evaluate this relationship more closely.Research Design: Prospective observational.Methods and Procedures: We obtained hourly pupillometry readings, alongside ICP values, from 40 patients with TBI requiring invasive ICP monitoring. Significant events were identified for analysis based on the significant aberration of ICP or NPi.Main Outcomes and Results: On average, individuals experienced a few significant events. There was a weak relationship between ICP events and a preceding NPi event. The results show that there is a weak but statistically insignificant relationship between NPi and ICP, where reduced pupil reactivity may indicate a raised ICP. The strength of this trend appears to diminish post-decompressive surgery.Conclusions: Whilst pupillometry may not be a reliable surrogate marker for ICP, NPi may still prove to be a useful tool in a multimodal prognostic assessment of the patient with acute brain injury.

Best zero level for external ICP transducer

BackgroundContinuous monitoring of intracranial pressure (ICP) was introduced in the 1950s. For correct ICP recordings, the zero-reference point for the external pressure gauge must be placed next to a head anatomical structure. We evaluated different anatomical points as zero reference for the ICP device at different head positions and their relation to brain centre (BC), foramen of Monro (Monro), and brain surface.MethodsPatients referred for neuroimaging due to e.g. headache all having normal 3D MRI scans were selected. Monro, BC, Orbit(O), external auditory meatus (EAM), and orbito-meatal (OM) line were identified and projected to mid-sagittal, or axial images. Each scan was evaluated like lying supine, 45° head elevations, upright, and 45° lateral position. Distances from skin to brain surface, BC, and Monro were measured. All values are presented as mean ± SD and/or range in millimetre. For conversion to mmHg, millimetre was multiplied by 0.074.ResultsTwenty MRI scans were examined. A zero reference at EAM or glabella was ideal at BC when head was strict supine or in the lateral position. At 45° head elevation, an overestimation of the BC-ICP by 4.8 ± 0.8 and in upright 5.6 ± 0.5 mmHg was found, and 45° lateral underestimated ICP-BC by 6.3 ± 1.0 mmHg. Monro was situated 45 ± 5 mm rostral to the mid-OM line and 24 (18–31) mm inferior and 13 (8–17) mm in front of BC. A zero-reference point aligned with the highest point of the head underestimated BC-ICP and Monro-ICP. If the ICP reading was added 5.9 or 6.3 mmHg, respectively, a deviation from BC-ICP was ≤ 1.8 mmHg and Monro-ICP was ≤ 0.9 mmHg in all head positions.ConclusionsEAM and glabella are defined anatomical structures representing BC when strict supine or lateral but with 12 mmHg variation with different head positions used in clinical practice. The OM line follows Monro at head elevation, but not when the head is turned. When the highest external point on the head is used, ICP values at brain surface as well as Monro and BC are underestimated. This underestimation is fairly constant and, when corrected for, provides the most exact ICP reading.

Pupillometry Trends in the Setting of Increased Intracranial Pressure.

Serial pupil examinations remain a mainstay of neurological assessments performed by neuroscience nurses. Integration of pupillometer technology has increased in recent years, because of its ability to address limitations of manual examinations and to evaluate trended data over time. Preliminary research has linked pupillometer values to intracranial pressure (ICP) values, but data on pupillary changes in the setting of increased ICP remain sparse. The purpose of this study was to determine trends in pupillometer values in the setting of increased ICP among critically ill patients with neurological injury. This is a secondary analysis of data where serial pupillometer and ICP readings were recorded hourly on adult patients with neurological injury necessitating critical care management. More than 2100 paired serial pupillometer and ICP readings were obtained from 76 subjects, with a total of 2107 paired readings for the left eye and 2175 for the right eye. There were statistically significant differences in pupillometry values in the setting of increased ICP. Time series analysis indicates that spikes in ICP values resulted in corresponding variations in pupillometer values. Use of automated pupillometry remains a value adjunct to traditional invasive therapies. Evaluation of trended data may provide insight into ICP elevations in the absence of invasive monitoring and warrants additional research.

Abstract WMP108: Defining Optimal Thresholds for Achieving Clinical Benefit in Spontaneous Intraventricular Hemorrhage

Introduction: Fibrinolytic therapy for spontaneous intraventricular hemorrhage (IVH) appears to reduce mortality with uncertain benefit on long-term functional outcomes. Threshold for volume of IVH which responds to intraventricular fibrinolytic therapy with therapeutic benefit has not been determined. Methods: CLEAR III, a randomized, multi-center, double-blinded, placebo-controlled trial was conducted to determine if pragmatically employed external ventricular drainage (EVD) plus intraventricular Alteplase improved outcome, in comparison to EVD plus saline. We analyzed of IVH volume strata from study randomization: Large IVH: volume ≥50 mL; small IVH: volume&lt;20 mL. We assessed clinical variables and outcomes by IVH volume group. Outcome measures were blinded assessment of modified Rankin score (mRS) at 30, 180 and 365 days, (with mRS&gt;3 signifying poor outcome). We performed logistic regression to evaluate outcomes by IVH volume group. Results: Among the 500 patients enrolled, 55 (11%) had IVH volumes &gt;50 mL and 222 (44.4%) had IVH volume &lt;20mL. Subjects with large volume IVH were older (mean, 62.3 vs. 58.1 years; p=0.01), had smaller ICH volume (6.1 vs. 9.9 mL; p&lt;0.001), less thalamic ICH (16.4% vs. 63.6%; p&lt;0.001), more pre-admission use of anticoagulants and antiplatelet agents and greater proportion of high intracranial pressure readings during monitoring at all thresholds (&gt;20, 30, 40 mmHg), compared to those with IVH volume &lt;50mL. Day 180 mortality and poor mRS were 49.1% and 81.8% in large volume IVH compared to 13.1% and 43.3% in small volume IVH. In logistic regression models adjusted for confounders, drainage of &gt;85% IVH volume was significantly associated with higher odds of good outcome (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.1-3.3) and lower odds of mortality (OR, 0.3; 95% CI, 0.1-0.8) compared to &lt;85% drainage, in patients with baseline volumes &lt;50mL. Removal of &gt;85% IVH volume (n=3/55) was not associated with improved outcomes in patients with large IVH. Conclusions: IVH volume &gt;50mL may represent a cohort without identified benefit from fibrinolytic treatment. Defining an upper limit for IVH volume would benefit from a larger sample and other methods of achieving IVH reduction.

Volumetric Ophthalmic Ultrasound for Inflight Monitoring of Visual Impairment and Intracranial Pressure.

The objective is enhanced ophthalmic ultrasound imaging to monitor ocular structure and intracranial dynamics changes related to visual impairment and intracranial pressure (ICP) induced by microgravity. The goals are to improve the ease of use and reduce operator variability by automatically rendering improved views of the anatomy and deriving new metrics of the morphology and dynamics. A prototype three-dimensional (3-D) probe was integrated onto a portable ultrasound scanner. Image analysis algorithms were developed to automatically detect the ocular anatomy and simultaneously render views of the optic nerve with improved sheath definition. Curvature metrics were calculated from 3-D retinal surfaces to quantify posterior globe flattening, and tissue velocity waveforms of the optic nerve were analyzed to assess intracranial dynamics. New 3-D structural measurements were evaluated in a head-down tilt study. The response of optic nerve sheath and globe flattening metrics were quantified in 11 healthy volunteers from baseline to moderately elevated ICP. The optic nerve measurements showed good correlation with existing two-dimensional (2-D) methods and an acute response to increased ICP, while globe flattening did not show an acute response. The tissue velocities were evaluated in a porcine model from baseline to significantly elevated ICP and correlated with invasive ICP readings in four animals. Volumetric ophthalmic imaging was demonstrated on a portable ultrasound system and structural measurements validated with existing methods. New 3-D structural measurements and dynamic measurements were evaluation during in vivo studies. Further investigations are needed to evaluate improvements in performance for non-experts and application to clinically relevant conditions.