Protecting the brain during neurosurgical procedures: strategies that can work

Crystalloids vs. colloids for fluid optimization in patients undergoing brain tumour surgery

BACKGROUND

This randomised, double-blinded, single-centre study prospectively investigated the impact of goal directed therapy and fluid optimization with crystalloids or colloids on perioperative complications in patients undergoing brain tumour surgery. Main aim of the study was to investigate the impact of fluid type on postoperative complications.

PATIENTS AND METHODS

80 patients were allocated into two equal groups to be optimised with either crystalloids (n = 40) or colloids (n = 40). Invasive hemodynamic monitoring was used to adjust and maintain mean arterial pressure and cerebral oxygenation within the baseline values (± 20%) and stroke volume variation (SVV) ≤ 10%. Postoperative complications from different organ systems were monitored during the first 15 days after surgery. Hospital stay was also recorded.

RESULTS

Crystalloid group received significantly more fluids (p = 0.003) and phenylephrine (p = 0.02) compared to colloid group. This did not have any significant impact on perioperative complications and hospital stay, since no differences between groups were observed.

CONCLUSIONS

Either crystalloids or colloids could be used for fluid optimization in brain tumour surgery. If protocolised perioperative haemodynamic management is used, the type of fluid does not have significant impact on the outcome.

Comparison of Propofol and Sevoflurane on Cerebral Oxygenation Using Juglar Venous Oximetery (SjVo2) in Patients Undergoing Surgery for Traumatic Brain Injury

Background:

Traumatic brain injury (TBI) induces major insult to the normal cerebral physiology. The anesthetic agents may infrequently produce deleterious effects and further aggravate damage to the injured brain. This study was conducted to evaluate the effects of propofol and sevoflurane on cerebral oxygenation, brain relaxation, systemic hemodynamic parameters and levels of interleukin-6 (IL-6) in patients with severe TBI undergoing decompressive craniectomy.

Methods:

A prospective randomized comparative study was conducted on 42 patients undergoing surgery for severe TBI. Patients were randomized into two groups, Group P received propofol and Group S received sevoflurane for maintenance of anesthesia. All patients were induced with fentanyl, propofol, and vecuronium. The effect of these agents on cerebral oxygenation was assessed by jugular venous oxygen saturation (SjVO₂). Hemodynamic changes and quality of intraoperative brain relaxation were also assessed. The serum levels of IL-6 were quantitated using enzyme-linked immunosorbent assay technique.

Results:

SjVO₂ values were comparable and mean arterial pressure (MAP) was found to be significantly lower in Group P as compared to those in Group S (P < 0.05). Brain relaxation scores were comparable between the groups. The level of IL-6 decreased significantly at the end of surgery compared to baseline in patients receiving sevoflurane (P = 0.040).

Conclusions:

Cerebral oxygenation measured by SjVO₂ was comparable when anesthesia was maintained with propofol or sevoflurane. However, significant reduction in MAP by propofol needs attention in patients with severe TBI. The decrease in IL-6 level reflects anti-inflammatory effect and probable neuroprotective potential of propofol and sevoflurane.

Effect of propofol and remifentanil on cerebral perfusion and oxygenation in pigs: a systematic review

The objective of this review is to evaluate the existing literature with regard to the influence of propofol and remifentanil total intravenous anaesthesia (TIVA) on cerebral perfusion and oxygenation in healthy pigs. Anaesthesia has influence on cerebral haemodynamics and it is important not only in human but also in veterinary anaesthesia to preserve optimal regulation of cerebral haemodynamics. Propofol and remifentanil are widely used in neuroanaesthesia and are increasingly used in experimental animal studies. In translational models, the pig has advantages compared to small laboratory animals because of brain anatomy, metabolism, neurophysiological maturation, and cerebral haemodynamics. However, reported effects of propofol and remifentanil on cerebral perfusion and oxygenation in pigs have not been reviewed. An electronic search identified 99 articles in English. Title and abstract screening selected 29 articles for full-text evaluation of which 19 were excluded with reasons. Of the 10 peer-reviewed articles included for review, only three had propofol or remifentanil anaesthesia as the primary study objective and only two directly investigated the effect of anaesthesia on cerebral perfusion and oxygenation (CPO). The evidence evaluated in this systematic review is limited, not focused on propofol and remifentanil and possibly influenced by factors of potential importance for CPO assessment. In one study of healthy pigs, CPO measures were within normal ranges following propofol-remifentanil anaesthesia, and addition of a single remifentanil bolus did not affect regional cerebral oxygen saturation (rSO2). Even though the pool of evidence suggests that propofol and remifentanil alone or in combination have limited effects on CPO in healthy pigs, confirmative evidence is lacking.

Effect of propofol and sevoflurane on the inflammatory response of patients undergoing craniotomy

BACKGROUND

The purpose of this randomised, single-centre study was to prospectively investigate the impact of anaesthetic techniques for craniotomy on the release of cytokines IL-6, IL-8, IL-10, and to determine whether intravenous anaesthesia compared to inhalational anaesthesia attenuates the inflammatory response.

METHODS

The study enroled 40 patients undergoing craniotomy, allocated into two equal groups to receive either sevoflurane (n = 20) or propofol (n = 20) in conjunction with remifentanil and rocuronium. The lungs were ventilated mechanically to maintain normocapnia. Remifentanil infusion was adjusted according to the degree of surgical manipulation and increased when mean arterial pressure and the heart rate increased by more than 30 % from baseline. The depth of anaesthesia was adjusted to maintain a bispectral index (BIS) of 40-60. Invasive haemodynamic monitoring was used. Serum levels of IL-6, IL-8 and IL-10 were measured before surgery and anaesthesia, during tumour removal, at the end of surgery, and at 24 and 48 h after surgery. Postoperative complications (pain, vomiting, changes in blood pressure, infection and pulmonary, cardiovascular and neurological events) were monitored during the first 15 days after surgery.

RESULTS

Compared with patients anaesthetised with sevoflurane, patients who received propofol had higher levels of IL-10 (p = 0.0001) and lower IL-6/IL-10 concentration ratio during and at the end of surgery (p = 0.0001). Both groups showed only a minor response of IL- 8 during and at the end of the surgery (p = 0.57).

CONCLUSIONS

Patients who received propofol had higher levels of IL-10 during surgery. Neither sevoflurane nor propofol had any significant impact on the occurrence of postoperative complications. Our findings should incite future studies to prove a potential medically important anti-inflammatory role of propofol in neuroanaesthesia.

CLINICAL TRIAL REGISTRATION

Identified as NCT02229201 at www.clinicaltrials.gov.

Cooling for cerebral protection during brain surgery

BACKGROUND

Patients undergoing neurosurgery are at risk of cerebral ischaemia with resultant cerebral hypoxia and neuronal cell death. This can increase both the risk of mortality and long term neurological disability. Induced hypothermia has been shown to reduce the risk of cerebral ischaemic damage in both animal studies and in humans who have been resuscitated following cardiac arrest. This had lead to an increasing interest in its neuroprotective potential in neurosurgical patients. This review was originally published in 2011 and did not find any evidence of either effectiveness or harm in these patients. This updated review was designed to capture current evidence to readdress these issues.

OBJECTIVES

To evaluate the effectiveness and safety profile of induced hypothermia versus normothermia for neuroprotection in patients undergoing brain surgery. Effectiveness was to be measured in terms of short and long term mortality and functional neurological outcomes. Safety was to be assessed in terms of the rate of the adverse events infection, myocardial infarction, ischaemic stroke, congestive cardiac failure and any other adverse events reported by the authors of the included studies.

SEARCH METHODS

For the original review, the authors searched the databases Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OvidSP), EMBASE (OvidSP) and LILACS to November 2010. For the updated review all these databases were re-searched from November 2010 to May 2014.For both the original and updated versions, grey literature was sought by searching reference lists of identified studies and relevant review articles, and conference proceedings. No language restrictions were applied.

SELECTION CRITERIA

As in the original review, we included randomized controlled trials (RCTs) of induced hypothermia versus normothermia for neuroprotection in patients of any age and gender undergoing brain surgery, which addressed mortality, neurological morbidity or adverse event outcomes.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted data and two independently assessed the risk of bias of the included studies. Any discrepancies were resolved by discussion between authors.

MAIN RESULTS

In this updated review, one new ongoing study was found but no new eligible completed studies were identified. This update was therefore conducted using the same four studies included in the original review. These studies included a total of 1219 participants, mean age 40 to 54 years. All included studies were reported as RCTs. Two were multicentred, together including a total of 1114 patients who underwent cerebral aneurysm clipping, and were judged to have an overall low risk of bias. The other two studies were single centred. One included 80 patients who had a craniotomy following severe traumatic brain injury and was judged to have an unclear or low risk of bias. The other study included 25 patients who underwent hemicranicectomy to relieve oedema following cerebral infarction and was judged to have an unclear or high risk of bias. All studies assessed hypothermia versus normothermia. Overall 608 participants received hypothermia with target temperatures ranging from 32.5 °C to 35 °C, and 611 were assigned to normothermia with the actual temperatures recorded in this group ranging form 36.5 °C to 38 °C. For those who were cooled, 556 had cooling commenced immediately after induction of anaesthesia that was continued until the surgical objective of aneurysm clipping was achieved, and 52 had cooling commenced immediately after surgery and continued for 48 to 96 hours.Pooled estimates of effect were calculated for the outcomes mortality during treatment or follow-up (ranging from in-hospital to one year); neurological outcome measured in terms of the Glasgow Outcome Score (GOS) of 3 or less; and adverse events of infections, myocardial infarction, ischaemic stroke and congestive cardiac failure. With regards to mortality, the risk of dying if allocated to hypothermia compared to normothermia was not statistically significantly different (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.59 to 1.27, P = 0.47). There was no indication that the time at which cooling was started affected the risk of dying (RR with intraoperative cooling 0.95, 95% CI 0.60 to 1.51, P = 0.83; RR for cooling postoperatively 0.67, 95% CI 0.34 to 1.35, P = 0.26). For the neurological outcome, the risk of having a poor outcome with a GOS of 3 or less was not statistically different in those who received hypothermia versus normothermia (RR 0.80, 95% CI 0.61 to 1.04, P = 0.09). Again there was no indication that the time at which cooling was started affected this result. Regarding adverse events, there was no statistically significant difference in the incidence in those allocated to hypothermia versus normothermia for risk of surgical infection (RR 1.20, 95% CI 0.73 to 1.97, P = 0.48), myocardial infarction (RR 1.86, 95% CI 0.69 to 4.98, P = 0.22), ischaemic stroke (RR 0.93, 95% CI 0.82 to 1.05, P = 0.24) or congestive heart failure (RR 0.85, 95% CI 0.60 to 1.21, P = 0.38). In contrast to other outcomes, where time of application of cooling did not change the statistical significance of the effect estimates, there was a weak statistically significant increased risk of infection in those who were cooled postoperatively versus those who were not cooled (RR 1.77, 95% CI 1.05 to 2.98, P = 0.03). Overall, as in the original review, no evidence was found that the use of induced hypothermia was either beneficial or harmful in patients undergoing neurosurgery.

AUTHORS' CONCLUSIONS

We found no evidence that the use of induced hypothermia was associated with a significant reduction in mortality or severe neurological disability, or an increase in harm in patients undergoing neurosurgery.

Principles of neuroanesthesia in aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage is associated with high mortality. Understanding of the underlying pathophysiology is important as early intervention can improve outcome. Increasing age, altered sensorium and poor Hunt and Hess grade are independent predictors of adverse outcome. Early operative interventions imposes an onus on anesthesiologists to provide brain relaxation. Coiling and clipping are the two treatment options with increasing trends toward coiling. Intraoperatively, tight control of blood pressure and adequate brain relaxation is desirable, so that accidental aneurysm rupture can be averted. Patients with poor grades tolerate higher blood pressures, but are prone to ischemia whereas patients with lower grades tolerate lower blood pressure, but are prone to aneurysm rupture if blood pressure increases. Patients with Hunt and Hess Grade I or II with uneventful intraoperative course are extubated in operation theater, whereas, higher grades are kept electively ventilated. Postoperative management includes attention toward fluid status and early management of vasospasm.