Effect of sevoflurane on cerebral blood flow and cerebrovascular resistance at surgical level of anaesthesia: a transcranial Doppler study

Comparison of Effects of Propofol and Sevoflurane on the Cerebral Vasculature Assessed by Digital Subtraction Angiographic Parameters in Patients Treated for Ruptured Cerebral Aneurysm: A Preliminary Study

BACKGROUND

Studies have evaluated the effects of volatile and intravenous anesthetic agents on the cerebral vasculature with inconsistent results. We used digital subtraction angiography to compare the effects of propofol and sevoflurane on the luminal diameter of cerebral vessels and on cerebral transit time in patients with aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

This prospective preliminary study included adult patients with good-grade aSAH scheduled for endovascular coil embolization; patients were randomized to receive propofol or sevoflurane anesthesia during endovascular coiling. The primary outcome was the luminal diameter of 7 cerebral vessel segments measured on the diseased and nondiseased sides of the brain at 3 time points: awake, postinduction of anesthesia, and postcoiling. Cerebral transit time was also measured as a surrogate for cerebral blood flow.

RESULTS

Eighteen patients were included in the analysis (9 per group). Baseline and intraoperative parameters were similar between the groups. Propofol increased the diameter of 1 vessel segment at postinduction and postcoiling on the diseased side and in 1 segment at postcoiling on the nondiseased side of the brain ( P <0.05). Sevoflurane increased vessel diameter in 3 segments at postinduction and in 2 segments at postcoiling on the diseased side, and in 4 segments at postcoiling on the nondiseased side ( P <0.05). Cerebral transit time did not change compared with baseline awake state in either group and was not different between the groups.

CONCLUSIONS

Sevoflurane has cerebral vasodilating properties compared with propofol in patients with good-grade aSAH. However, sevoflurane affects cerebral transit time comparably to propofol.

Vascular and neuronal effects of general anesthesia on the brain: An fMRI study

BACKGROUND AND PURPOSE

A number of functional magnetic resonance imaging (fMRI) studies rely on application of anesthetic agents during scanning that can modulate and complicate interpretation of the measured hemodynamic blood oxygenation level-dependent (BOLD) response. The purpose of the present study was to investigate the effect of general anesthesia on two main components of BOLD signal including neuronal activity and vascular response.

METHODS

Breath-holding (BH) fMRI was conducted in wakefulness and under anesthesia states in 9 patients with drug-resistant epilepsy who needed to get scanned under anesthesia during laser interstitial thermal therapy. BOLD and BOLD cerebrovascular reactivity (BOLD-CVR) maps were compared using t-test between two states to assess the effect of anesthesia on neuronal activity and vascular factors (p < .05).

RESULTS

Overall, our findings revealed an increase in BOLD-CVR and decrease in BOLD response under anesthesia in several brain regions. The results proposed that the modulatory mechanism of anesthetics on neuronal and vascular components of BOLD signal may work in different ways.

CONCLUSION

This experiment for the first human study showed that anesthesia may play an important role in dissociation between neuronal and vascular responses contributed to hemodynamic BOLD signal using BH fMRI imaging that may assist the implication of general anesthesia and interpretation of outcomes in clinical setting.

Sevoflurane sedation attenuates early cerebral oedema formation through stabilisation of the adherens junction protein beta catenin in a model of subarachnoid haemorrhage: A randomised animal study

BACKGROUND

Severe neurological impairment is a problem after subarachnoid haemorrhage (SAH). Although volatile anaesthetics, such as sevoflurane, have demonstrated protective properties in many organs, their use in cerebral injury is controversial. Cerebral vasodilation may lead to increased intracranial pressure (ICP), but at the same time volatile anaesthetics are known to stabilise the SAH-injured endothelial barrier.

OBJECTIVE

To test the effect of sevoflurane on ICP and blood-brain barrier function.

DESIGN

Randomised study.

PARTICIPANTS

One hundred male Wistar rats included, 96 analysed.

INTERVENTIONS

SAH was induced by the endoluminal filament method under ketamine/xylazine anaesthesia. Fifteen minutes after sham surgery or induction of SAH, adult male Wistar rats were randomised to 4 h sedation with either propofol or sevoflurane.

MAIN OUTCOME MEASURES

Mean arterial pressure (MAP), ICP, extravasation of water (small), Evan's blue (intermediate) and IgG (large molecule) were measured. Zonula occludens-1 (ZO-1) and beta-catenin (β-catenin), as important representatives of tight and adherens junction proteins, were determined by western blot.

RESULTS

Propofol and sevoflurane sedation did not affect MAP or ICP in SAH animals. Extravasation of small molecules was higher in SAH-propofol compared with SAH-sevoflurane animals (79.1 ± 0.9 vs. 78.0 ± 0.7%, P = 0.04). For intermediate and large molecules, no difference was detected (P = 0.6 and P = 0.2). Both membrane and cytosolic fractions of ZO-1 as well as membrane β-catenin remained unaffected by the injury and type of sedation. Decreased cytosolic fraction of β-catenin in propofol-SAH animals (59 ± 15%) was found to reach values of sham animals (100%) in the presence of sevoflurane in SAH animals (89 ± 21%; P = 0.04).

CONCLUSION

This experiment demonstrates that low-dose short-term sevoflurane sedation after SAH in vivo did not affect ICP and MAP and at the same time may attenuate early brain oedema formation, potentially by preserving adherens junctions.

TRIAL REGISTRATION

No 115/2014 Veterinäramt Zürich.

Effect of dexmedetomidine on dynamic cerebral autoregulation and carbon dioxide reactivity during sevoflurane anesthesia in healthy patients

BACKGROUND

There are conflicting opinions on the effect of dexmedetomidine on cerebral autoregulation. This study assessed its effect on dynamic cerebral autoregulation (dCA) using a transcranial Doppler (TCD).

METHODS

Thirty American Society of Anesthesiologists physical status I and II patients between 18 and 60 years, who underwent lumbar spine surgery, received infusions of dexmedetomidine (Group D) or normal saline (Group C), followed by anesthesia with propofol and fentanyl, and maintenance with oxygen, nitrous oxide and sevoflurane. After five minutes of normocapnic ventilation and stable bispectral index value (BIS) of 40-50, the right middle cerebral artery flow velocity (MCAFV) was recorded with TCD. The transient hyperemic response (THR) test was performed by compressing the right common carotid artery for 5-7 seconds. The lungs were hyperventilated to test carbon dioxide (CO2) reactivity. Hemodynamic parameters, arterial CO2 tension, pulse oximetry (SpO2), MCAFV and BIS were measured before and after hyperventilation. Dexmedetomidine infusion was discontinued ten minutes before skin-closure. Time to recovery and extubation, modified Aldrete score, and emergence agitation were recorded.

RESULTS

Demographic parameters, durations of surgery and anesthesia, THR ratio (Group D: 1.26 ± 0.11 vs. Group C: 1.23 ± 0.04; P = 0.357), relative CO2 reactivity (Group D: 1.19 ± 0.34 %/mmHg vs. Group C: 1.23 ± 0.25 %/mmHg; P = 0.547), blood pressure, SpO2, BIS, MCAFV, time to recovery, time to extubation and modified Aldrete scores were comparable.

CONCLUSIONS

Dexmedetomidine administration does not impair dCA and CO2 reactivity in patients undergoing spine surgery under sevoflurane anesthesia.

Pathophysiological and clinical considerations in the perioperative care of patients with a previous ischaemic stroke: a multidisciplinary narrative review

With an ageing population and increasing incidence of cerebrovascular disease, an increasing number of patients presenting for routine and emergency surgery have a prior history of stroke. This presents a challenge for pre-, intra-, and postoperative management as the neurological risk is considerably higher. Evidence is lacking around anaesthetic practice for patients with vascular neurological vulnerability. Through understanding the pathophysiological changes that occur after stroke, insight into the susceptibilities of the cerebral vasculature to intrinsic and extrinsic factors can be developed. Increasing understanding of post-stroke systemic and cerebral haemodynamics has provided improved outcomes from stroke and more robust secondary prevention, although this knowledge has yet to be applied to our delivery of anaesthesia in those with prior stroke. This review describes the key pathophysiological and clinical considerations that inform clinicians providing perioperative care for patients with a prior diagnosis of stroke.

Effect of sevoflurane on systemic and cerebral circulation, cerebral autoregulation and CO2 reactivity

Background

Sevoflurane is one of the most frequently used inhaled anesthetics for general anesthesia. Previously it has been reported that at clinically used doses of sevoflurane, cerebral vasoreactivity is maintained. However, there are no data how sevoflurane influences systemic and cerebral circulation in parallel. The aim of our study was to assess systemic and cerebral hemodynamic changes as well as cerebral CO₂-reactivity during sevoflurane anesthesia.

Methods

Twenty nine patients undergoing general anesthesia were enrolled. Anesthesia was maintained with 1 MAC sevoflurane in 40% oxygen. Ventilatory settings (respiratory rate and tidal volume) were adjusted to reach and maintain 40, 35 and 30 mmHg EtCO₂ for 5 min respectively. At the end of each period, transcranial Doppler and hemodynamic parameters using applanation tonometry were recorded.

Results

Systemic mean arterial pressure significantly decreased during anesthetic induction and remained unchanged during the entire study period. Central aortic and peripherial pulse pressure and augmentation index as markers of arterial stiffness significantly increased during the anesthetic induction and remained stable at the time points when target CO₂ levels were reached. Both cerebral autoregulation and cerebral CO₂-reactivity was maintained at 1 MAC sevoflurane.

Discussion

Cerebral autoregulation and CO₂-reactivity is preserved at 1 MAC sevoflurane. Cerebrovascular effects of anesthetic compounds have to be assessed together with systemic circulatory effects.

Trial registration

The study was registered at http://www.clinicaltrials.gov, identifier: NCT02054143, retrospectively registered. Date of registration: February 4, 2014.

Effects of anesthesia on cerebral blood flow, metabolism, and neuroprotection

Administration of anesthetic agents fundamentally shifts the responsibility for maintenance of homeostasis from the patient and their intrinsic physiological regulatory mechanisms to the anesthesiologist. Continuous delivery of oxygen and nutrients to the brain is necessary to prevent irreversible injury and arises from a complex series of regulatory mechanisms that ensure uninterrupted cerebral blood flow. Our understanding of these regulatory mechanisms and the effects of anesthetics on them has been driven by the tireless work of pioneers in the field. It is of paramount importance that the anesthesiologist shares this understanding. Herein, we will review the physiological determinants of cerebral blood flow and how delivery of anesthesia impacts these processes.

Changes in Rat Brain MicroRNA Expression Profiles Following Sevoflurane and Propofol Anesthesia

BACKGROUND

Sevoflurane and propofol are widely used anesthetics for surgery. Studies on the mechanisms of general anesthesia have focused on changes in protein expression properties and membrane lipid. MicroRNAs (miRNAs) regulate neural function by altering protein expression. We hypothesize that sevoflurane and propofol affect miRNA expression profiles in the brain, expect to understand the mechanism of anesthetic agents.

METHODS

Rats were randomly assigned to a 2% sevoflurane group, 600 μg·kg - 1·min - 1 propofol group, and a control group without anesthesia (n = 4, respectively). Treatment group was under anesthesia for 6 h, and all rats breathed spontaneously with continuous monitoring of respiration and blood gases. Changes in rat cortex miRNA expression profiles were analyzed by miRNA microarrays and validated by quantitative real-time polymerase chain reaction (qRT-PCR). Differential expression of miRNA using qRT-PCR among the control, sevoflurane, and propofol groups were compared using one-way analysis of variance (ANOVA).

RESULTS

Of 677 preloaded rat miRNAs, the microarray detected the expression of 277 miRNAs in rat cortex (40.9%), of which 9 were regulated by propofol and (or) sevoflurane. Expression levels of three miRNAs (rno-miR-339-3p, rno-miR-448, rno-miR-466b-1FNx01) were significantly increased following sevoflurane and six (rno-miR-339-3p, rno-miR-347, rno-miR-378FNx01, rno-miR-412FNx01, rno-miR-702-3p, and rno-miR-7a-2FNx01) following propofol. Three miRNAs (rno-miR-466b-1FNx01, rno-miR-3584-5p and rno-miR-702-3p) were differentially expressed by the two anesthetic treatment groups.

CONCLUSIONS

Sevoflurane and propofol anesthesia induced distinct changes in brain miRNA expression patterns, suggesting differential regulation of protein expression. Determining the targets of these differentially expressed miRNAs may help reveal both the common and agent-specific actions of anesthetics on neurological and physiological function.

Cerebral blood flow change during volatile induction in large-dose sevoflurane versus intravenous propofol induction: transcranial Doppler study

Background

The impact of volatile induction using large-dose sevoflurane (VI-S) on cerebral blood flow has not been well investigated. The present study compared the changes in cerebral blood flow of middle cerebral artery using transcranial Doppler (TCD) during VI-S and conventional induction using propofol.

Methods

Patients undergoing elective lumbar discectomy were randomly allocated to receive either sevoflurane (8%, Group VI-S, n = 11) or target-controlled infusion of propofol (effect site concentration, 3.0 µg/ml; Group P, n = 11) for induction of anesthesia. The following data were recorded before and at 1, 2, and 3 min after commencement of anesthetic induction (T0, T1, T2, and T3, respectively): mean velocity of the middle cerebral artery (V_MCA) by TCD, mean blood pressure (MBP), heart rate, bispectral index score (BIS) and end-tidal CO₂ (ETCO₂). Changes in V_MCA and MBP from their values at T0 (ΔV_MCA and ΔMBP) at T1, T2, and T3 were also determined.

Results

BISs at T1, T2 and T3 were significantly less than that at T0 in both groups (P < 0.05). ΔVMCA in Group VI-S at T2 and T3 (18.1% and 12.4%, respectively) were significantly greater than those in Group P (-7.6% and -19.8%, P = 0.006 and P < 0.001, respectively), whereas ETCO₂ and ΔMBP showed no significant intergroup difference.

Conclusions

VI-S using large-dose sevoflurane increases cerebral blood flow resulting in luxury cerebral flow-metabolism mismatch, while conventional propofol induction maintains cerebral flow-metabolism coupling. This mismatch in VI-S may have to be considered in clinical application of VI-S.

Changes of dorsalis pedis artery flow pattern after caudal block in children: observational study using a duplex sonography

OBJECTIVE

To evaluate the changes of the flow velocity, the volume flow, and the diameter of dorsalis pedis artery using a duplex ultrasonography after caudal block with sevoflurane anesthesia in children.

AIM

To know the acute change in peripheral arterial flow patterns of sympathetically blocked lower limbs in anesthetized children.

BACKGROUND

Caudal analgesia in combination with general anesthesia may affect the circulatory hemodynamics due to sympatholytic vasodilating effects.

METHODS

After approval by the Ethics Committee, we evaluated the changes of peripheral hemodynamics using a duplex ultrasonography before and after a caudal block in sevoflurane-anesthetized children.

RESULTS

A caudal block using 0.15% ropivacaine 1.5 ml·kg(-1) significantly altered the arterial flow patterns; increased peak velocity (24%) and volume flow (76%), and the diameter of the dorsalis pedis artery (20%) in children. However, blood pressures and heart rates were not affected significantly by caudal block.

CONCLUSIONS

Duplex sonographic measurements indicate that a caudal block changes the flow patterns of the dorsalis pedis artery significantly in the anesthetized children.

[Transcranial Doppler ultrasound, bispectral index, and electroencephalographic monitoring of entropy during pediatric total intravenous anesthesia]

BACKGROUND AND OBJECTIVE

Transcranial Doppler ultrasound is a noninvasive technique for monitoring the velocity of blood flow in the main intracranial arteries, particularly those in the circle of Willis. Our aim was to assess whether changes in cerebral arterial blood flow in anesthetized pediatric patients detected by pulsed Doppler ultrasound correlate with changes in the bispectral (BIS) index and electroencephalographic state and response entropy (ES and ER, respectively).

MATERIAL AND METHODS

Prospective, blinded observational study of 36 pediatric patients (age range, 5 to 11 years) under total intravenous anesthesia for minor surgical procedures. Propofol and fentanyl were used for induction; propofol and remifentanil in continuous perfusion and a single dose of cisatracurium were used for maintenance. In all patients we monitored hemodynamic and respiratory patterns, gases, temperature, and hypnosis (BIS, ES and ER) as well as cerebral blood flow estimated by pulsed Doppler ultrasound in the middle cerebral artery. Raw data were subjected to statistical smoothing. The resistance index, pulsatility index, mean velocity, and estimated baseline cerebral blood flow were calculated from the Doppler sonogram. We then studied the correlations between the Doppler-derived values and BIS, ES, ER, fraction of end-tidal carbon dioxide, and temperature. The variables were entered into logistic regression.

RESULTS

The pattern at induction indicated high resistance (low mean velocities and high pulsatility indexes) until the lowest BIS and ES values of 31 and 29, respectively, were reached. During maintenance, the Doppler sonogram pattern was slower (normalization of the pulsatility index, the resistance index, and mean velocity). Changes in flow and absolute entropy and BIS values were statistically correlated (Pearson's r values > or = 0.91); there was 95.6% agreement between Doppler values and BIS and agreement between BIS and ES values of 35-45. On awakening, flow velocities approached baseline values when BIS and ES rose to between 90 and 98. The estimated cerebral blood flow underwent fluctuations coinciding with an approximately concomitant increase or decrease in BIS (r > 0.95); the response of BIS was slightly delayed by no more than a minute but there was no corresponding response of entropy measurements.

CONCLUSIONS

We report Doppler ultrasound patterns during anesthesia with propofol. Systems for monitoring hypnosis could be considered indirect measurements of cerebral blood flow; BIS measurements are more sensitive to flow change. Transcranial Doppler ultrasound facilitates the observation of changes in blood flow that occur at different levels of hypnosis during anesthesia.

[Transcranial Doppler ultrasound, bispectral index, and electroencephalographic monitoring of entropy during sevoflurane anesthesia in children]

BACKGROUND AND OBJECTIVE

Transcranial Doppler ultrasound is a noninvasive technique for monitoring the velocity of blood flow in the main intracranial arteries, particularly those in the circle of Willis. Our aim was to assess whether changes in cerebral arterial blood flow in pediatric patients under sevoflurane anesthesia demonstrated by pulsed Doppler ultrasound correlate with changes in the bispectral (BIS) index and electroencephalographic state and response entropy (ES and ER, respectively).

MATERIAL AND METHODS

Prospective, blinded observational study of 36 pediatric patients (age range, 5 to 11 years; ASA physical status classification, 1-2) under sevoflurane anesthesia for minor surgical procedures. Anesthesia was induced with sevoflurane and maintained with 2.5% sevoflurane in an inspired oxygen fraction of 50% in air. A continuous perfusion of remifentanil was provided for analgesia. In all patients we monitored hemodynamic and respiratory patterns, gases, temperature, and hypnosis (BIS, ES and ER) as well as cerebral blood flow estimated by pulsed Doppler ultrasound in the middle cerebral artery. The resistance index, pulsatility index, mean velocity, and estimated baseline cerebral blood flow were calculated from the Doppler sonogram. Correlations (Pearson's r) were calculated between BIS, ES, ER, the pulsatility index, resistance index, mean flow velocity, estimated cerebral blood flow, fraction of end-tidal carbon dioxide, and temperature. A regression model was constructed.

RESULTS

Induction caused a pattern of high velocity (elevated mean velocity and normal or reduced pulsatility index) until the lowest BIS and ES values of 31 and 29, respectively, were reached. During maintenance, the Doppler sonogram pattern was slower (normalization of the pulsatility index, the resistance index, and mean velocity). Changes in flow and absolute entropy and BIS values were statistically correlated (Pearson's r values > or = 0.91); there was 95.6% agreement between Doppler values and BIS and agreement between BIS and ES values of 35 to 45. On awakening, flow velocities approached baseline values when BIS and ES rose to between 90 and 98. The estimated cerebral blood flow underwent fluctuations coinciding with an approximately concomitant increase or decrease in BIS (r > 0.95); the BIS response occurred with a slight delay of no more than a minute. The entropy measurements did not reflect the fluctuations.

CONCLUSIONS

We show Doppler ultrasound patterns during anesthetic induction with sevoflurane. Systems for monitoring hypnosis could be considered indirect measurements of cerebral blood flow; BIS measurements are more sensitive to change. Transcranial Doppler ultrasound facilitates the observation of changes in blood flow that occur at different levels of hypnosis during anesthesia.