The effect of increased positive end expiratory pressure on brain tissue oxygenation and intracranial pressure in acute brain injury patients.

Cerebral hypoxia is an important cause of secondary brain injury. Improving systemic oxygenation may increase brain tissue oxygenation (PbtO2). The effects of increased positive end-expiratory pressure (PEEP) on PbtO2 and intracranial pressure (ICP) needs to be further elucidated. This is a single center retrospective cohort study (2016-2021) conducted in a 34-bed Department of Intensive Care unit. All patients with acute brain injury under mechanical ventilation who were monitored with intracranial pressure and brain tissue oxygenation (PbtO2) catheters and underwent at least one PEEP increment were included in the study. Primary outcome was the rate of PbtO2 responders (increase in PbtO2 > 20% of baseline) after PEEP increase. ΔPEEP was defined as the difference between PEEP at 1 h and PEEP at baseline; similarly ΔPbtO2 was defined as the difference between PbtO2 at 1 h after PEEP incrementation and PbtO2 at baseline. We included 112 patients who underwent 295 episodes of PEEP increase. Overall, the median PEEP increased form 6 (IQR 5-8) to 10 (IQR 8-12) cmH2O (p = 0.001), the median PbtO2 increased from 21 (IQR 16-29) mmHg to 23 (IQR 18-30) mmHg (p = 0.001), while ICP remained unchanged [from 12 (7-18) mmHg to 12 (7-17) mmHg; p = 0.42]. Of 163 episode of PEEP increments with concomitant PbtO2 monitoring, 34 (21%) were PbtO2 responders. A lower baseline PbtO2 (OR 0.83 [0.73-0.96)]) was associated with the probability of being responder. ICP increased in 142/295 episodes of PEEP increments (58%); no baseline variable was able to identify this response. In PbtO2 responders there was a moderate positive correlation between ΔPbtO2 and ΔPEEP (r = 0.459 [95% CI 0.133-0.696]. The response in PbtO2 and ICP to PEEP elevations in brain injury patients is highly variable. Lower PbtO2 values at baseline could predict a significant increase in brain oxygenation after PEEP increase.

Serum LDH levels may predict poor neurological outcome after aneurysmal subarachnoid hemorrhage.

INTRODUCTION: Serum lactate dehydrogenase (LDH) levels are often elevated in cardiovascular diseases. Their prognostic role after subarachnoid hemorrhage (SAH) remains poorly evaluated. METHODS: This is a retrospective single-center study of patients with non-traumatic SAH admitted to the intensive care unit (ICU) of an University Hospital from 2007 to 2022. Exclusion criteria were pregnancy and incomplete medical records or follow-up data. Baseline information, clinical data, radiologic data, the occurrence of neurological complications as well as serum LDH levels during the first 14 days of ICU stay were collected. Unfavorable neurological outcome (UO) at 3 months was defined as a Glasgow Outcome Scale of 1-3. RESULTS: Five hundred and forty-seven patients were included; median serum LDH values on admission and the highest LDH values during the ICU stay were 192 [160-230] IU/L and 263 [202-351] IU/L, respectively. The highest LDH value was recorded after a median of 4 [2-10] days after ICU admission. LDH levels on admission were significantly higher in patients with UO. When compared with patients with favorable outcome (FO), patients with UO had higher serum LDH values over time. In the multivariate logistic regression model, the highest LDH value over the ICU stay (OR 1.004 [95% CI 1.002 - 1.006]) was independently associated with the occurrence of UO; the area under the receiving operator (AUROC) curve for the highest LDH value over the ICU stay showed a moderate accuracy to predict UO (AUC 0.76 [95% CI 0.72-0.80]; p < 0.001), with an optimal threshold of > 272 IU/L (69% sensitivity and 74% specificity). CONCLUSIONS: The results in this study suggest that high serum LDH levels are associated with the occurrence of UO in SAH patients. As a readily and available biomarker, serum LDH levels should be evaluated to help with the prognostication of SAH patients.

The Impact of Invasive Brain Oxygen Pressure Guided Therapy on the Outcome of Patients with Traumatic Brain Injury: A Systematic Review and Meta-Analysis.

Traumatic brain injury (TBI) is a major public health burden, causing death and disability worldwide. Intracranial hypertension and brain hypoxia are the main mechanisms of secondary brain injury. As such, management strategies guided by intracranial pressure (ICP) and brain oxygen (PbtO2) monitoring could improve the prognosis of these patients. Our objective was to summarize the current evidence regarding the impact of PbtO2-guided therapy on the outcome of patients with TBI. We performed a systematic search of PubMed, Scopus, and the Cochrane library databases, following the protocol registered in PROSPERO. Only studies comparing PbtO2/ICP-guided therapy with ICP-guided therapy were selected. Primary outcome was neurological outcome at 3 and 6 months assessed by using the Glasgow Outcome Scale; secondary outcomes included hospital and long-term mortality, burden of intracranial hypertension, and brain tissue hypoxia. Out of 6254 retrieved studies, 15 studies (n = 37,245 patients, of who 2184 received PbtO2-guided therapy) were included in the final analysis. When compared with ICP-guided therapy, the use of combined PbO2/ICP-guided therapy was associated with a higher probability of favorable neurological outcome (odds ratio 2.21 [95% confidence interval 1.72-2.84]) and of hospital survival (odds ratio 1.15 [95% confidence interval 1.04-1.28]). The heterogeneity (I2) of the studies in each analysis was below 40%. However, the quality of evidence was overall low to moderate. In this meta-analysis, PbtO2-guided therapy was associated with reduced mortality and more favorable neurological outcome in patients with TBI. The low-quality evidence underlines the need for the results from ongoing phase III randomized trials.

Effect of inotropic agents on oxygenation and cerebral perfusion in acute brain injury.

Introduction: Tissue hypoxia and insufficient energy delivery is one of the mechanisms behind the occurrence of several complications in acute brain injured patients. Several interventions can improve cerebral oxygenation; however, the effects of inotropic agents remain poorly characterized. Methods: Retrospective analysis including patients suffering from acute brain injury and monitored with brain oxygen pressure (PbtO2) catheter, in whom inotropic agents were administered according to the decision of the treating physician's decision; PbtO2 values were collected before, 1 and 2 h after the initiation of therapy from the patient data monitoring system. PbtO2 "responders" were patients with a relative increase in PbtO2 from baseline values of at least 20%. Results: A total of 35 patients were included in this study. Most of them (31/35, 89%) suffered from non-traumatic subarachnoid hemorrhage (SAH). Compared with baseline values [20 (14-24) mmHg], PbtO2 did not significantly increase over time [19 (15-25) mmHg at 1 h and 19 (17-25) mmHg at 2 h, respectively; p = 0.052]. A total of 12/35 (34%) patients were PbtO2 "responders," in particular if low PbtO2 was observed at baseline. A PbtO2 of 17 mmHg at baseline had a sensibility of 84% and a specificity of 91% to predict a PbtO2 responder. A significant direct correlation between changes in PbtO2 and cardiac output [r = 0.496 (95% CI 0.122 to 0.746), p = 0.01; n = 25] and a significant negative correlation between changes in PbtO2 and cerebral perfusion pressure [r = -0.389 (95% CI -0.681 to -0.010), p = 0.05] were observed. Conclusions: In this study, inotropic administration significantly increased brain oxygenation in one third of brain injured patients, especially when tissue hypoxia was present at baseline. Future studies should highlight the role of inotropic agents in the management of tissue hypoxia in this setting.

Phosphatase alkaline levels are not associated with poor outcomes in subarachnoid hemorrhage patients.

INTRODUCTION: Alkaline phosphatase (ALP) levels are often elevated in cerebrovascular and cardiovascular disease. Their prognostic role after subarachnoid hemorrhage (SAH) remains to be elucidated. METHODS: We performed a retrospective single center study of patients with non-traumatic SAH admitted to the intensive care unit (ICU) of Erasme Hospital (Brussels, Belgium) from 2006 to 2019. Exclusion criteria were previous history of liver cirrhosis or malignancies and early death (i.e. within 24 h from ICU admission). Baseline information, clinical data, radiologic data were collected, the occurrence of DCI as well as serum ALP levels during the first 12 days of ICU stay. Unfavorable neurological outcome (UO) at 3 months was defined as a Glasgow Outcome Scale of 1-3. RESULTS: Six hundred and fifty patients were included; ALP levels increased from baseline after day 6 from admission, in particular among patients with an initial poor clinical status. There was no difference in the ALP levels between patients with or without DCI over time. Patients with UO had higher ALP levels over time than others; however, in the multivariable analysis, nor ALP levels on admission or the highest ALP value during the ICU stay were independently associated with UO. CONCLUSIONS: The results of this study suggested that ALP levels had no prognostic role in SAH patients. Other possible prognostic biomarkers should be evaluated in this setting.

Use of Sedatives and Neuromuscular-Blocking Agents in Mechanically Ventilated Patients with COVID-19 ARDS.

OBJECTIVES: To assess differences in the use of analgesics, sedatives and neuromuscular-blocking agents (NMBA) in patients with acute respiratory distress syndrome (ARDS) due to COVID-19 or other conditions. METHODS: Retrospective observational cohort study, single-center tertiary Intensive Care Unit. COVID-19 patients with ARDS (March-May 2020) and non-COVID ARDS patients (2017-2020) on mechanical ventilation and receiving sedation for at least 48 h. RESULTS: A total of 39 patients met the inclusion criteria in each group, with similar demographics at baseline. COVID-19 patients had a longer duration of MV (median 22 (IQRs 16-29) vs. 9 (6-18) days; p < 0.01), of sedatives administration (18 (11-22) vs. 5 (4-9) days; p < 0.01) and NMBA therapy (12 (9-16) vs. 3 (2-7) days; p < 0.01). During the first 7 days of sedation, compared to non-COVID patients, COVID patients received more frequently a combination of multiple sedative drugs (76.9% vs. 28.2%; p < 0.01) and a higher NMBA regimen (cisatracurium: 3.0 (2.1-3.7) vs. 1.3 (0.9-1.9) mg/kg/day; p < 0.01). CONCLUSIONS: The duration and consumption of sedatives and NMBA was significantly increased in patients with COVID-19 related ARDS than in non-COVID ARDS. Different sedation strategies and protocols might be needed in COVID-19 patients with ARDS, with potential implications on long-term complications and drugs availability.