Mean Intracranial Pressure Values Research Articles

Effects of unilateral decompressive craniectomy on patients with unilateral acute post-traumatic brain swelling after severe traumatic brain injury

IntroductionAcute post-traumatic brain swelling (BS) is one of the pathological forms that need emergent treatment following traumatic brain injury. There is controversy about the effects of craniotomy on acute post-traumatic BS. The aim of the present clinical study was to assess the efficacy of unilateral decompressive craniectomy (DC) or unilateral routine temporoparietal craniectomy on patients with unilateral acute post-traumatic BS.MethodsSeventy-four patients of unilateral acute post-traumatic BS with midline shifting more than 5 mm were divided randomly into two groups: unilateral DC group (n = 37) and unilateral routine temporoparietal craniectomy group (control group, n = 37). The vital signs, the intracranial pressure (ICP), the Glasgow outcome scale (GOS), the mortality rate and the complications were prospectively analysed.ResultsThe mean ICP values of patients in the unilateral DC group at hour 24, hour 48, hour 72 and hour 96 after injury were much lower than those of the control group (15.19 +/- 2.18 mmHg, 16.53 +/- 1.53 mmHg, 15.98 +/- 2.24 mmHg and 13.518 +/- 2.33 mmHg versus 19.95 +/- 2.24 mmHg, 18.32 +/- 1.77 mmHg, 21.05 +/- 2.23 mmHg and 17.68 +/- 1.40 mmHg, respectively). The mortality rates at 1 month after treatment were 27% in the unilateral DC group and 57% in the control group (p = 0.010). Good neurological outcome (GOS Score of 4 to 5) rates 1 year after injury for the groups were 56.8% and 32.4%, respectively (p = 0.035). The incidences of delayed intracranial hematoma and subdural effusion were 21.6% and 10.8% versus 5.4% and 0, respectively (p = 0.041 and 0.040).ConclusionsOur data suggest that unilateral DC has superiority in lowering ICP, reducing the mortality rate and improving neurological outcomes over unilateral routine temporoparietal craniectomy. However, it increases the incidence of delayed intracranial hematomas and subdural effusion, some of which need secondary surgical intervention. These results provide information important for further large and multicenter clinical trials on the effects of DC in patients with acute post-traumatic BS.Trial registrationISRCTN14110527

Time Course of Intracranial Hypertension after Traumatic Brain Injury

High intracranial pressure (HICP) may be a very early event after traumatic brain injury (TBI), but in most cases, especially when contusions and edema develop over time, HICP will worsen over succeeding days. This study describes the incidence and severity of elevated intracranial pressure (ICP) after TBI and attempts to document its time course. In this prospective study, 201 TBI patients in whom ICP was monitored for more than 12 h were evaluated. ICP was measured, digitalized, and analyzed after manual filtering. The number of episodes of HICP and the mean ICP value for every 12-h interval were calculated. When monitoring was concluded, the highest mean ICP collected in every patient was identified. A total of 21,000 h of ICP monitoring were recorded. Active treatment to prevent or reduce HICP was used in 200 patients. HICP was documented in 155 cases. Half of the patients had their highest mean ICP during the first 3 days after injury, but many showed delayed ICP elevation, with 25% showing highest mean ICP after day 5. In these cases, HICP was significantly worse and required more intense therapies.

Is intracranial pressure monitoring in the epidural space reliable? Fact and fiction

Epidural pressures have been reported as being systematically higher than ventricular fluid pressures. These discrepancies have been attributed both to the characteristics of the sensor and to the particular anatomy of the epidural space. To determine which of these two possible causes better explains higher epidural readings, the authors compared pressure values obtained during simultaneous epidural and lumbar pressure monitoring in 53 patients and during simultaneous subdural and lumbar pressure monitoring in 22 patients. The same nonfluid coupled sensor device was used in all compartments. All 75 patients had normal craniospinal communication. Simultaneous intracranial and lumbar readings were performed every 30 seconds. The epidural-lumbar and subdural-lumbar pressure values were compared using correlation analysis and the Bland-Altman method. The median differences in initial epidural-lumbar and subdural-lumbar pressure values were 11 mm Hg (interquartile range 2-24 mm Hg) and 0 mm Hg (interquartile range -2 to 1 mm Hg), respectively. The correlation coefficients of the mean epidural-lumbar and subdural-lumbar intracranial pressure (ICP) values were p = 0.48 (p < 0.001) and p = 0.88 (p < 0.001), respectively. Using the Bland-Altman analysis, epidural-lumbar methods showed a mean difference of -20.93 mm Hg; epidural pressure values were systematically higher than lumbar values, and these discrepancies were greater with higher ICP values. Subdural-lumbar methods showed a mean difference of 0.35 mm Hg and both were equally valid with all mean ICP values. Epidural ICP monitoring produces artifactually high values. These values are not related to the type of sensor used but to the specific characteristics of the epidural intracranial space.

Predictive value of initial computerized tomography scan, intracranial pressure, and state of autoregulation in patients with traumatic brain injury

The authors explored the relationship between computerized tomography (CT) scan findings and intracranial pressure (ICP) measurements obtained in the first 24 hours of monitoring to identify parameters predicting outcome in patients with severe traumatic brain injury (TBI). Intracranial pressure, mean arterial blood pressure, cerebral perfusion pressure (CPP), and pressure reactivity index were measured continuously in 126 patients with severe TBI who were admitted to a neuroscience critical care unit. Mean values in the initial 24 hours of monitoring and in the total period of monitoring were compared with types of injury categorized on the basis of the initial CT scan according to the classification of Marshall, et al., and with Glasgow Outcome Scale scores. The initial CT scan classification correlated significantly but weakly with ICP measured during the first 24 hours of monitoring (p = 0.036) but not with mean ICP over the total time of intensive care. Both midline shift and the ratio of frontal horn diameter to internal diameter correlated with ICP in the first 24 hours (p < 0.007) and with ICP over the total monitoring period (p < 0.03). Outcome score correlated with initial CT scan findings (p = 0.018), ICP over the total monitoring period (p < 0.0023), pressure reactivity over the total monitoring period (p < 0.0002), and pressure reactivity in the first 24 hours (p < 0.0001) but not with ICP in the first 24 hours. Patients with disturbed pressure reactivity in the first 24 hours after injury had a significantly higher mortality rate than patients with intact pressure reactivity (28.6% compared with 9.5%; p < 0.001). Patients with severe TBI who have early loss of autoregulation have a worse prognosis. Mean ICP values in patients with diffuse TBI cannot be predicted by using the Marshall CT scan classification.

Comparison of simultaneous continuous intracranial pressure (ICP) signals from a Codman and a Camino ICP sensor

Simultaneous continuous intracranial pressure (ICP) signals from two different sensors were compared. Continuous ICP monitoring from two ICP sensors (i.e. Codman ICP MicroSensor; Johnson & Johnson, Raynham, MA and Camino OLM ICP; Camino Laboratories, San Diego, CA) placed within the brain parenchyma was performed in three patients within the intensive care unit (ICU) as part of routine management of severe subarachnoid hemorrhage. For each 6 s time window mean ICP was computed, showing large differences in mean ICP values between the signals. Differences above 5 mmHg were observed in 13% of the 128,425 time windows derived from 214 h ICP recordings in these three patients. In one patient, mean ICP differed more than 10 mmHg in 23% of the time windows. Comparisons of 675,503 individual single pressure wave pairs of these 128,425 time windows revealed marginal differences in single wave amplitude (d P, i.e. pulse pressure) and latency (d T, i.e. rise time) values, suggesting that differences in mean ICP were caused by differences in baseline pressure. For the individual time windows were computed the mean wave amplitude and mean wave latency values according to a new algorithm. There were as well marginal differences between signals of mean wave amplitude and latency values. Thus, changes in baseline pressure affect mean ICP but not single pressure wave characteristics such as amplitude (d P) and (d T) latency values.

Relevance of ICP and ptiO2 for indication and timing of decompressive craniectomy in patients with malignant brain edema

The exact effects of decompressive craniectomy on intracranial pressure (ICP) and cerebral tissue oxygenation (ptiO2) are still unclear. Therefore, we have monitored ICP and ptiO2 intra-operatively and correlated these values to different operative steps during craniectomy. ICP and ptiO2 values have been monitored both, simultaneously and continuously, in 15 patients with cerebral edema due to posttraumatic or postischemic brain swelling. Indications for craniectomy were an increase in ICP above 25 mmHg or a decrease in ptiO2 below 10 mmHg resistant to conservative treatment (e.g. mannitol, hyperventilation, adequate arterial blood oxygenation, etc.). In all cases, we performed a fronto-temporo-parietal craniectomy (15 x 12 cm) and dura enlargement with galea-periosteum. During craniectomy, monitoring of ICP and ptiO2 in the affected hemisphere was continued. Values were recorded and correlated with the different operative steps. We performed craniectomy according to our treatment protocol in 5 patients. Prior to surgery, mean ICP values were 25.6 mmHg (range: 23-29 mmHg), mean ptiO2 values were 5.9 mmHg (range: 2.4-9.5 mmHg), and mean CPP values were 66 mmHg (range: 60-70 mmHg). After removing the bone flap, ICP values dropped to physiological values (mean: 7.4 mmHg), whereas ptiO2 values increased only slightly (mean: 11 mmHg). Opening of the dura resulted in a further decrease of ICP (mean 4.8 mmHg) and an increase of ptiO2 to normal limits (mean: 18.8 mmHg). After skin closure, mean ICP was 6.8 mmHg and mean ptiO2 was 21.7 mmHg, respectively. We found a significant decrease of ICP after craniectomy (p<0.042) and after dura enlargement (p<0.039) as well as a statistically significant increase in ptiO2 after craniectomy (p<0.043) and after dura enlargement (p<0.041). As a large bone flap in decompressive craniectomy is essential for adequate ICP reduction, the results of the presented cases suggest that dura enlargement is the crucial step to restore adequate brain tissue oxygenation and that ptiO2 monitoring could be an important tool for timing craniectomy in the future.

Effect of hyperbaric oxygenation on intracranial pressure elevation rate in rats during the early phase of severe traumatic brain injury

Intracranial pressure (ICP) was monitored to evaluate the therapeutic effect of hyperbaric oxygen (HBO 2) treatment following traumatic brain injury (TBI). This subject is controversial. The aim of our study was to determine whether HBO 2 treatment has a therapeutic effect on ICP dynamics and survival following severe fluid percussion brain injury (FPBI) in rats. Changes in ICP level were analyzed every 30 min during an 8-h monitoring period following trauma and at the end of experiment (20 h). The control (A) and experimental (B) groups consisted of 7 and 4 rats, respectively. Group B was subjected to 1.5 atmospheres absolute (ATA) 100% oxygen for 60 min beginning 2 h after FPBI. No significant differences in ICP were noted between groups A and B before and after HBO 2 treatment until 3.5 h after trauma. At 4 h, for the first time, the difference became significant ( P = 0.025; n = 11) and remained significant ( P < 0.05) for all measurement points until end of monitoring, when mean ICP values reached 37.17 ± 14.25 and 20.25 ± 2.63 mm Hg in groups A and B, respectively. Linear approximation models showed different trends (b1 = 3.80 ± 0.23; r 2 = 0.65, P < 0.001 and b1 = 1.56 ± 0.25; r 2 = 0.77, P < 0.001) for groups A and B, respectively. Covariance analysis confirmed significant differences between slopes for groups A and B ( F = 148.04, P < 0.001; df = 2,177), i.e., a significant difference in mean rate of ICP elevation. By the end of the experiment, 3 out of 7 rats from group A had died, but none from group B. We conclude that the application of HBO 2 during the early phase of severe FPBI significantly diminished ICP elevation rate and decreased mortality level.

Intracranial pressure monitoring in children with single suture and complex craniosynostosis: a review

One third of patients with craniofacial dysostosis syndromes and about 15-20% of children with single suture craniostenosis have a documented increase in intracranial pressure (ICP). The early detection of intracranial hypertension is important in order to reduce the risks for brain development and visual function. However, in children with craniosynostosis, the clinical manifestations of abnormally increased ICP are difficult to detect, as the majority of patients may have neither warning signs nor symptoms for a long period of time. Moreover, data from the literature suggest that neither fundoscopic nor radiological findings are necessarily related to intracranial pressure recordings in this type of pathology. In this context prolonged ICP monitoring seems actually to be the most valuable diagnostic tool. Extradural, subdural, and intraparenchymal devices have been used, and different softwares have been employed for PC storage and analysis of the data obtained. Most recent series consider mean ICP combined with plateaux waves as the most sensitive indicators in the final evaluation of the results. The analysis of the literature demonstrates a significant difference in the prevalence of raised ICP preoperatively between non-syndromic and syndromic patients. Among the non-syndromic children, a direct relation between the number of sutures involved and raised ICP is documented. The analysis of plateaux waves seems to be particularly important in children with borderline mean ICP values. Persistent postoperative raised ICP has been described in 6-15% of patients with craniofacial dysostosis. It must be related to the multifactorial etiology of increased ICP in these patients, which includes cerebral venous congestion, upper airway obstruction, and hydrocephalus.

Noninvasive intracranial compliance and pressure based on dynamic magnetic resonance imaging of blood flow and cerebrospinal fluid flow: review of principles, implementation, and other noninvasive approaches

Current techniques for intracranial pressure (ICP) measurement are invasive. All require a surgical procedure for placement of a pressure probe in the central nervous system and, as such, are associated with risk and morbidity. These considerations have driven investigators to develop noninvasive techniques for pressure estimation. A recently developed magnetic resonance (MR) imaging-based method to measure intracranial compliance and pressure is described. In this method the small changes in intracranial volume and ICP that occur naturally with each cardiac cycle are considered. The pressure change during the cardiac cycle is derived from the cerebrospinal fluid (CSF) pressure gradient waveform calculated from the CSF velocities. The intracranial volume change is determined by the instantaneous differences between arterial blood inflow, venous blood outflow, and CSF volumetric flow rates into and out of the cranial vault. Elastance (the inverse of compliance) is derived from the ratio of the measured pressure and volume changes. A mean ICP value is then derived based on a linear relationship that exists between intracranial elastance and ICP. The method has been validated in baboons, flow phantoms, and computer simulations. To date studies in humans demonstrate good measurement reproducibility and reliability. Several other noninvasive approaches for ICP measurement, mostly nonimaging based, are also reviewed. Magnetic resonance imaging-based ICP measurement may prove valuable in the diagnosis and serial evaluation of patients with a variety of disorders associated with alterations in ICP.

Evalution of an Epidural Intracranial Pressure Monitoring System in Cats

SummaryThe accuracy of an inexpensive, easily implantable, epidural intracranial pressure (ICP) monitoring system was assessed in six normal cats by comparing measurements from this system to those obtained with a fiberoptic intraparenchymal monitoring system. The epidural monitoring system consisted of a three‐way stopcock and saline‐filled extension tubing, connected to a standard blood pressure transducer. Each cat was placed under halothane anesthesia and mechanically ventilated. Both an epidural and a fiberoptic intraparenchymal monitoring device were placed in the left cranium of each cat; correct placement was verified by computed tomography. Mean ICP values were simultaneously recorded from both monitoring devices. After obtaining baseline ICP measurements, the ICP was manipulated via ventilation, jugular compression, and pharmacologic agents. Arterial blood pressure levels, arterial blood gas values, end‐tidal carbon dioxide levels, and end‐tidal halothane levels were recorded throughout the study. Cerebral perfusion pressure was calculated for each level of ICP. Repeated measures analysis of variance method was used to compare mean ICP values between the two monitoring systems. No significant differences in ICP values obtained from the two systems were found (p&gt;0.05) at any level of ICP. The results of this study show that the epidural monitoring system is a reliable alternative to the fiberoptic intraparenchymal ICP monitoring system in normal cats. The accuracy of the epidural monitoring system in pathologic states needs to be investigated.

Detection of the B waves in the oscillation of intracranial pressure by fast Fourier transform

Intracranial pressure (ICP) oscillation consists of a cardiac-induced component, a respiration-induced component and fluctuation of the base level of ICP. Lundberg reported three types of fluctuations of the base level of ICP with increasing ICP which were referred to as A, B and C waves. Computer algorithms for sampling, processing and displaying ICP data were investigated to depict the power spectrum of ICP oscillations by fast Fourier transform (FFT), thus enabling the B wave to be automatically detected. A power peak was found in the ICP power spectrum between 30 and 120 s, which corresponds to the frequency of the B wave. The maximum power, corresponding to the B-wave amplitude was above 0 dB. An appropriate sampling interval for FFT inputs was about 8 s for real-time processing of the ICP data. The mean ICP value was found useful for making the B-wave peak clearer by reducing the cardiac and respiratory components of ICP oscillations; the window function had no effect on B-wave detection in the ICP power spectrum.