Traumatic brain injury (TBI) is a significant contributor to mortality and morbidity at a global level, disproportionately affecting individuals in their prime working years. This multifaceted health condition has far-reaching economic and social consequences, rendering it a significant public health concern, particularly in developing nations¹⁾. The gravity of the situation demands swift, concerted efforts to mitigate its impact and improve outcomes for those affected.

The most reliable method for monitoring intracranial pressure (ICP) in cases of traumatic brain injury involves the surgical placement of an intracranial sensor, which allows for direct measurement of pressure within the skull²⁾. Three primary locations are utilized for sensor placement: intraventricular, intraparenchymal, and subdural. While this approach is highly effective for tracking patients with severe head trauma, it is also associated with a number of complications, including hemorrhage, obstruction, mispositioning, infection, and reduced accuracy in cases of asymmetric hemispheric lesions²⁾. Furthermore, the invasive nature of this technique requires a neurosurgical procedure, which carries its own set of risks and considerations. Therefore, while intracranial sensor insertion may be the gold standard for ICP monitoring in TBI, it is important to carefully weigh the risks and benefits of this approach before proceeding with treatment.

The concept of intracranial pressure monitoring gained its popularity after the publication of brain trauma foundation (BTF) guidelines on the multimodal management of the traumatic brain injury. The multimodal monitoring suggest for the escalation of therapy in a tiered manner³⁾. The approach for enhancing treatment for herniation syndromes is carried out in a tiered manner and ought to be executed without postponing invasive intracranial monitoring, also known as multimodal monitoring. The initial options that may be considered are placing the patient in an upright position, avoiding neck manipulation, addressing agitation and fever, attempting hyperosmolar therapy, and finally deciding whether urgent surgery is necessary. If there is clinical improvement, such as in pupil dilation or examination, these maneuvers may indicate that the patient is approaching the end of the intracranial volume-pressure curve. These crucial measures must be taken to ensure that the patient's health is preserved and that their herniation syndrome is managed effectively.

Since the start of ICP monitoring in TBI patients, there have been several studies that produce conflicting and mixed results on the outcome in TBI patients with ICP monitoring primarily mortality and length of hospital stay. Using ICP montoring to guide the patient management has its own limitations. ICP monitoring is resource intensive and time consuming and depends on the both the modality used for measurement and location of the probe. Therefore the monitoring may mislead when there is focal point of herniation. This is one of the reason why BTF guidelines recommends on ICP monitoring diffuse pathologies. It is noteworthy that in a study involving malignant stroke, a considerable number of patients exhibited a midline shift and pupillary changes despite ICP monitoring revealing an ICP < 22 mm Hg, thereby indicating that ICP values may not always reflect a concerning clinical picture⁴⁾. One of the study found that the ICP montoring is as good as the clinical examination on the outcomes following TBI⁵⁾.

In severe traumatic brain injury (sTBI), Intracranial pressure monitoring is the preferred method of monitoring. However, the criteria for its insertion remains unclear. The brain trauma foundation Guidelines Edition 3 provided recommendations for ICP monitoring, and in the absence of new evidence, the latest revision defaulted to those recommendations^6,7). Despite this, practice surveys have shown significant variation in the use of monitoring on both individual and institutional levels, with poor adherence to BTF recommendations^8,9). This implies that the decision-making process is inconsistent and poorly understood, a critical issue when assessing the efficacy of ICP monitor-based care in non-controlled studies. Furthermore, some providers may view ICP monitoring data as having little additional clinical value in uncertain situations. Therefore, there is a pressing need for a more comprehensive understanding of the criteria for ICP monitoring insertion and improved adherence to guidelines to enhance the efficacy of ICP monitoring in the management of sTBI.

The precise indications for ICP monitoring in TBI patients are unknonwn and guidelines making recommndations have low penetrance and evidence for the same. Alali et al. pubished the predictors and clinical decision making rule for selecting the ICP monitoring in TBI patients based on the clinical and radiological parameters¹⁰⁾. However there is significant variability on the medthod of ICP monitoring and frequency. As the ICP monitoring is resource intensive, its use if often limited to high resource settings and lower resource settings use alternative methods of ICP management. Therefore there is no confirming evidence that ICP monitoring reduces mortality in TBI patients.

This overview aims to summarize the evidence in Cochrane and non-Cochrane systematic reviews, the effects, and the benefits of monitoring intracranial pressure in patients with head trauma with an indication of ICP monitoring.

This comprehensive review provides a summary of the published evidence on the impact of ICP monitoring on the duration of hospital stays, mortality rates, and procedure-related adverse events in adult patients suffering from traumatic brain injury. This review is based on a total of 49 primary research studies and 19 unique primary studies, as analyzed by the five SR-MAs. Mortality was reported as outcome in majority of the primary studies. Only one SR-MA found that the use of ICP monitoring lowered the mortality in the TBI patients¹⁵⁾. SR-MAs found that there was no significant effect on the reduction of mortality with ICP monitoring^5,17). In two SR-MAs the results varied according to the time of publication of primary studies with later studies having a positive effect of ICP monitoring on reducing the mortality while earlier studies did not find any significant effect^16,18). One of the SR-MA found that the resources used in the ICU were less with the use of ICP monitoring group due to better targeted therapy⁵⁾. The effect of ICP monitoring on the length of hospital stay was reduced in the ICP monitoring group in one of the SR-MA^5,18) while it was prolonged in the other¹⁵⁾. There was high heterogeneity in the SR-MAs^5,15-18). The high heterogeneity in the included primary research studies could be due to the combination of different study types in the systematic reviews, heterogenous population and mode of ICP monitoring. The variables studied in each of the primary research studies were varying and that could add to the heterogeneity. Though most of the primary research studies focused on adult patients with both genders and severe traumatic brain injury, the classification of severity of the brain in jury was not uniform in all of the studies. The study by Quesda et al. was the only SR-MA that assessed the neurpsychological function as the outcome and found that there was no significant impact of ICP monitoring on the neuropsychological function of TBI patients⁵⁾. The study included two RCTs and was rated as high quality of evidence; however among the two studies the study by Chestnut et al. was at low risk of bias while there was unclear risk of bias in the study by Kostic et al. domains of random sequence generation, allocation concealment, reporting bias and other biases of the Cochrane risk of bias tool. Three SR-Mas have combined the observational studies with RCTs and performed the subgroup analysis and found that though there was no significant decrease in mortality with the ICP monitoring in the RCTs, observational studies tend to show more effect of reduced mortality. These results were extracted from a pool of five SR-Mas of which one was rated of moderate quality and rest four as high quality by the AMSTAR tool. Because of high heterogeneity in the included studies included in the present overview and inclusion of RCTs and observational studies, we have high degree of certainity in the conclusions from the present overview. The findings from the present overview align with the RCTs and most of the recent systematic reviews that there is no significant effect of ICP monitoring on reducing the mortality. The studies on the procedure related events, neurpsychological outcomes and length of hospital stay are limited in number to make any meaningful conclusions and more primary research studies are required to find the association.

Shibahashi et al. have published the results of the real world experience in a propensity score matched analysis of 31,660 patients from 765 hospitals from the Japanese inpatient nationwide database and found that there was significantly reduced mortality in ICP monitoring group (31.9% vs. 39.1 %) and a longer duration of hospital stay (35 vs. 28 days) ¹⁹⁾. The gaps in the evidence is likely to filled by more studies on the topic gathering real world experience and avoiding the potential confounders.

One of the reasons for conflicting evidence could also be due to the fact that it is not known from the primary researcg studies as to what was the objective of the placement of the ICP monitoring devices. As found in the several studies, the focus has been on utilizing the values obtained from the ICP monitoring in guiding the management, while the ICP monitoring device itself can be used to lower the ICP when placed inside the ventricles with intermittent CSF release^20-22). In one of the retrospective study with different protocols of ICP monitoring from two different trauma centres, authors reported that there was no significant difference in mortality and the complications varied according to the device used for ICP monitoring²³⁾. According to a study conducted by the National Trauma Databank, the monitoring of ICPdemonstrated an association with a notable 45% rise in mortality rates. This correlation remained significant even after accounting for head Abbreviated Injury Scale (AIS) and Injury Severity Score (ISS) ²⁴⁾. The difference in outcomes with ICP monitoring in individual studies could also be due to difference in adherence to the management guidelines and delay in insertion of the ICP monitoring. As found in the study by shafi etal. The adherence and compliance was only 45%²⁴⁾. The strict adherence to a protocol-driven management strategy for TBI, which involves the placement of an ICPmonitor for all severe TBI (sTBI) patients, resulted in a noteworthy reduction in mortality rates that, while not statistically significant, is nevertheless noteworthy²⁵⁾. Furthermore, this approach also led to a marked reduction in overall costs, as well as a significant decrease in both ICU and hospital stay durations²⁵⁾.

Notwithstanding the limitations, in the present literature synthesis we have found that the studies showed mixed results on the effect of ICP monitoring in outcomes following traumatic brain injury and there is no compelling evidence that ICP monitonring reduces the mortality. We have found high heterogeneity in the studies and future studies addressing the mentioned limitations might help us to answer the question and increase the strength of evidence on use of ICP monitoring. Due to lack of evidence on the role of ICP monitoring in reducing the mortality in TBI patients, and increased use of ICP monitoring post brain trauma foundation guidelines, it has been found that more ICP targeted therapies are used in the pateints undergoing ICP monitoring. Therefore, the present overview suggest that the outcomes of ICP monitoring has been continuously evolving with time and therefore there is no compelling evidence to recommend its universal use or to remove it from use till stronger evidence is found either in support or againt ICP monitoring. ICP monitoring should be used as stated in the brain trauma foundation guidelines in an level one traumacentre facility with the availability of targeted ICP management therapies.