Bispectral index and regional cerebral oxygen saturation during propofol/N2O anesthesia

Cerebral oximetry monitoring in non-intubated patients undergoing endoscopic retrograde cholangiopancreatography under propofol-induced sedation: a prospective observational study

Background

Prolonged propofol-induced deep sedation increases the risk for sedation-related complications. Cerebral oximetry enables prompt assessment of tissue oxygenation by demonstrating the regional hemoglobin oxygen saturation (rSO₂) of the cerebral cortex. This study aimed to: evaluate cerebral oxygenation under deep sedation during an endoscopic retrograde cholangiopancreatography (ERCP) procedure; determine the cerebral desaturation event (CDE) rate; and assess the predictive capacity of CDEs for sedation-related complications.

Methods

All consecutive patients who underwent ERCP between September and December 2019 were included prospectively. Propofol monotherapy was used and sedation level was assessed using the bispectral index (BIS). The target level of sedation was deep sedation, defined by BIS values 40-60. Participants were monitored with arterial blood gas analysis and INVOS 5100C cerebral oximeter. RSO₂ values were registered prior to sedation (baseline value), every 5 min during the sedation period and at recovery of consciousness. BIS values were recorded simultaneously. CDE was defined as a drop >10% from individual baseline rSO₂.

Results

Sixty patients were enrolled. Mean baseline rSO₂ was 65.1% and BIS values ranged from 18-85. No significant correlation was observed between mean rSO₂ measurements and mean BIS values throughout the recordings (P = 0.193). Data from patients aged ≥65 years were analyzed separately and the results were similar. The CDE rate was 2.7%, but no CDE was associated with clinical manifestations. Twelve sedation-related complications occurred without the presence of cerebral desaturation.

Conclusion

Cerebral oxygenation remained independent of changes in sedation depth and cerebral oximetry monitoring did not detect complications earlier than standard monitors.

Monitoring the Depth of Anesthesia Through the Use of Cerebral Hemodynamic Measurements Based on Sample Entropy Algorithm

OBJECTIVE

The aim of this study is to explore the relationship between the depth of anesthesia and the cerebral hemodynamic variables during the complete anesthesia process.

METHODS

In this study, near-infrared spectroscopy signals were used to record eight kinds of cerebral hemodynamic variables, including left, right, proximal, distal deoxygenated (Hb) and oxygenated (HbO₂) hemoglobin concentration changes. Then, by measuring the complexity information of cerebral hemodynamic variables, the sample entropy was calculated as a new index of monitoring the depth of anesthesia.

RESULTS

By means of receiver operating characteristic curve analysis, the sample entropy approach was proved to effectively discriminate anesthesia maintenance and waking phases. The discriminatory ability of HbO₂ signals was stronger than that of Hb signals and the distal signals had weaker discrimination capability when compared with the proximal signals. In addition, there was statistical consistency between the bispectral index and sample entropy of cerebral hemodynamic variables during the complete anesthesia process. Moreover, the cerebral hemodynamic signals could not be interfered by clinical electrical devices.

CONCLUSION

The sample entropy of cerebral hemodynamic variables could be suitable as a new index for monitoring the depth of anesthesia.

SIGNIFICANCE

This study is very meaningful for developing new modality and decoding methods in perspective of anesthesia surveillance and may result in the anesthesia monitoring system with high performance.

Near-infrared spectroscopy for the evaluation of anesthetic depth

The standard-of-care guidelines published by the American Society of Anesthesiologists (ASA) recommend monitoring of pulse oximetry, blood pressure, heart rate, and end tidal CO2 during the use of anesthesia and sedation. This information can help to identify adverse events that may occur during procedures. However, these parameters are not specific to the effects of anesthetics or sedatives, and therefore they offer little, to no, real time information regarding the effects of those agents and do not give the clinician the lead-time necessary to prevent patient "awareness." Since no "gold-standard" method is available to continuously, reliably, and effectively monitor the effects of sedatives and anesthetics, such a method is greatly needed. Investigation of the use of functional near-infrared spectroscopy (fNIRS) as a method for anesthesia or sedation monitoring and for the assessment of the effects of various anesthetic drugs on cerebral oxygenation has started to be conducted. The objective of this paper is to provide a thorough review of the currently available published scientific studies regarding the use of fNIRS in the fields of anesthesia and sedation monitoring, comment on their findings, and discuss the future work required for the translation of this technology to the clinical setting.

Improvement of cerebral oxygen saturation after successful electrical cardioversion of atrial fibrillation

AIMS

Cerebral and microvascular perfusion is reduced in atrial fibrillation (AF). Maintenance of brain perfusion is important in acute disease and long-term course. Assessment of brain perfusion and oxygenation is difficult in clinical practice. Our study aimed to determine changes in cerebral tissue oxygen saturation (SctO2) with bedside near-infrared spectroscopy (NIRS).

METHODS AND RESULTS

Twenty patients (mean age 67.7 ± 10.2 years, 50% men) in whom electrical cardioversion (CV) was successful were prospectively studied. Ten patients (mean age 64.2 ± 7.7 years, 80% men) in whom CV was not successful served as control group. Bilateral SctO2, mean arterial pressure (MAP), arterial oxygen saturation (SaO2), and heart rate were recorded and changes of all parameters before and after CV were compared between the groups. Our results show an increase in SctO2 after successful CV that was significantly higher compared with patients who remained in AF (right SctO2 3.25 ± 2.5 vs. -0.13 ± 0.52%, P = 0.001; left SctO2 4.27 ± 3.56 vs. -0.38 ± 2.4%, P < 0.001). Neither arterial blood pressure nor SaO2 changes differed significantly between the two groups. No correlation could be detected between the significant increase of SctO2 after successful CV and arterial blood pressure, SaO2, or heart rate.

CONCLUSION

Cerebral tissue oxygen saturation increases significantly after restoration of sinus rhythm. Near-infrared spectroscopy monitoring can identify changes of SctO2 after successful CV of AF independent from standard monitoring parameters (MAP, SaO2). Near-infrared spectroscopy can be used to detect cerebral oxygen saturation deficits in AF patients or patients at high risk for AF. Clinical applications may include monitoring during ablation procedures and in critical care.

Comparison of the recovery and respiratory effects of aminophylline and doxapram following total intravenous anesthesia with propofol and remifentanil

STUDY OBJECTIVE

To compare the effects of aminophylline and doxapram on recovery, respiration, and bispectral index (BIS) values in patients after total intravenous anesthesia (TIVA) with propofol and remifentanil.

DESIGN

Prospective, randomized, blinded clinical trial.

SETTING

Operating room of a university hospital.

PATIENTS

90 adult, ASA physical status 1 and 2 patients scheduled for elective laparoscopic vaginal hysterectomy.

INTERVENTIONS

TIVA was performed with the induction target of remifentanil 3 ng/mL and propofol 6 μg/mL, followed by the maintenance target of remifentanil 1-3 ng/mL and propofol 3-5 μg/mL at the effect site, and with BIS scores in 40-50 range. Patients were randomized to three groups to receive intravenous (IV) aminophylline 3 mg/kg (n = 30), IV doxapram 1 mg/kg (n = 30), or normal IV saline (control; n = 30).

MEASUREMENTS AND MAIN RESULTS

After administration of the study drugs, return to spontaneous ventilation differed significantly among the three groups. The times to eye opening and hand squeezing on verbal command were similar. The time to extubation was shortened in both the doxapram and aminophylline groups (P < 0.05). Tidal volumes were increased in the doxapram group at 5-14 minutes and the aminophylline group at 5-12 minutes (P < 0.05). Respiratory rates were increased at 2 to 8 minutes and then showed a decrease at the 12 to 14-minute mark in both the doxapram and aminophylline groups (P < 0.05). No difference was noted between the two groups. BIS values were increased in both the doxapram and aminophylline groups at 4-10 minutes (P < 0.05). Heart rates were increased in the doxapram group for the first 8 minutes and at 1-2 minutes in the aminophylline group (P < 0.05).

CONCLUSION

Aminophylline 3 mg/kg or doxapram 1 mg/kg shortened the time to spontaneous ventilation and improved early recovery from TIVA without appreciable side effects. The more rapid emergence correlates with higher BIS values when compared with the saline control group. The arousal and respiratory effects of aminophylline were comparable to those of doxapram.

The effects of aminophylline on bispectral index during inhalational and total intravenous anaesthesia

Aminophylline is usually used during anaesthesia to treat bronchospasm but recent findings suggest that it can also be used to shorten recovery time after general anaesthesia. However, it is unclear whether aminophylline shows similar properties during a steady-state phase of deep surgical anaesthesia. We therefore wanted to test the hypothesis that the administration of aminophylline leads to an increase in bispectral index as a surrogate parameter suggesting a lighter plane of anaesthesia. The study was designed as a double-blind, randomised, controlled trial with two main groups (aminophylline and placebo) and two subgroups (sevoflurane and propofol). We studied 60 patients. The injection of aminophylline 3 mg x kg(-1) was associated with significant increases in bispectral index up to 10 min after its injection, while heart rate and blood pressure did not change. It appears that aminophylline has the ability to partially antagonise the sedative effects of general anaesthetics.

The influence of sevoflurane on the bispectral index, regional cerebral oxygen saturation, and propofol concentration during propofol/N2O anesthesia

OBJECTIVE

This study was undertaken to investigate the influence of sevoflurane on the bispectral index (BIS), regional cerebral oxygen saturation (rSO(2)), and serum propofol concentration during propofol/N(2)O anesthesia. This study tested the hypothesis that sevoflurane affect BIS values, rSO(2), and the pharmacokinetics of propofol during propofol/ N(2)O anesthesia.

METHODS

General anesthesia was administered to 15 ASA I-II patients with a continuous infusion of propofol to maintain a BIS value of 45 +/- 5. After recording baseline values, patients were assigned to receive sevoflurane (2.0%, 20 min). BIS values, rSO(2) using near-infrared spectroscopy, and hemodynamic parameters were recorded for 60 min. Cardiac output (CO) and stroke volume (SV) were evaluated using impedance cardiograph methods. Propofol concentration was determined using high-performance liquid chromatography.

RESULTS

Sevoflurane (2.0%, 20 min) decreased the BIS score from 47.4 +/- 8.2 to 27.3 +/- 5.9 (P < 0.01, n = 15) without affecting rSO(2). Sevoflurane decreased systolic blood pressure from 112.1 +/- 14.0 mmHg to 96.5 +/- 13.2 mmHg (P < 0.001, n = 15) without affecting heart rate. Both CO and SV were significantly decreased during sevoflurane application. Propofol concentration was increased from 2.71 +/- 0.51 microg/ml to 3.30 +/- 0.57 microg/ml (P < 0.05) after sevoflurane application, and was returned to baseline after sevoflurane washout.

CONCLUSIONS

We have shown that sevoflurane decreases BIS values during propofol/N(2)O anesthesia without affecting rSO(2) and that this change is accompanied by an increase in serum propofol concentration. Changes in propofol concentration may be due to, at least in part, hemodynamic changes such as decreased CO produced by sevoflurane.