Cerebral Oximetry in General Anaesthesia

Correlation and agreement of regional cerebral oxygen saturation measured from sensor sites at frontal and temporal areas in adult patients undergoing cardiovascular anesthesia

Background

The function and viability of the brain depend on adequate oxygen supply. A decrease in cerebral blood supply causing cerebral desaturation may lead to many neurological complications. Direct measurement of regional cerebral oxygen saturation (rScO₂) assists in early detection and management. Near-infrared spectroscopy (NIRS) has been introduced for measuring rScO₂. A pair of sensors are attached to the right and left forehead. However, there are some situations where the forehead of the patient is not accessible for sensor attachment (e.g., neurosurgery involving the frontal area; a bispectral index (BIS) sensor already attached, or a wound to the forehead); therefore, alternate sites for sensor attachment are required. The temporal area was proposed as an alternate site. The objective of this study was to assess the correlation and agreement of rScO₂ measured at the forehead vs. the temporal area.

Methods

Adult patients undergoing cardiothoracic or vascular surgery were monitored for rScO₂ using two pairs of ForeSight sensors. The first pair (A1 and A2) were attached to the right and left forehead, while the second pair (B1 and B2) were attached to the right and left temporal area. The rScO₂ values measured from A1 vs. B1 and A2 vs. B2 were assessed for correlation and agreement using the Bland-Altman analysis.

Results

Data from 19 patients with 14,364 sets of data were analyzed. The data from A1 vs. B1 and A2 vs. B2 showed moderate positive correlation (r = 0.627; P < 0.0001 and r = 0.548; P < 0.0001). The biases of A1 vs. B1 and A2 vs. B2 were -2.3% (95% CI [-2.5 to -2.2]; P < 0.0001) and 0.7% (95% CI [0.6-0.8]; P < 0.0001). The lower and upper limits of agreement of A1 vs. B1 were -17.5% (95% CI [-17.7 to -17.3]) and 12.8% (95% CI [12.6-13.0]). The lower and upper limits of agreement of A2 vs. B2 were -14.6% (95% CI [-14.8 to -14.4]) and 16.0% (95% [CI 15.8-16.3]).

Conclusions

The rScO₂ values measured from sensors at the frontal and temporal areas show a moderate correlation with sufficiently good agreement. The temporal area may be an alternative to the frontal area for cerebral oximetry monitoring.

Intraoperative hyperoxygenation may negatively affect postoperative cognitive functions in coronary artery bypass graft operations: A randomized controlled study

OBJECTIVE

In this study, it was aimed to compare various parameters during surgery and postoperative cognitive functions in patients undergoing coronary artery bypass graft (CABG) surgery using different levels of perioperative oxygen.

METHODS

One hundred patients scheduled for elective CABG surgery were included in the study. The patients were divided into two groups according to arterial oxygen levels during surgery. In the normoxia group (NG) (n = 50), partial arterial oxygen pressure (PaO₂ ) was between ≥100 and <180 mmHg with at least 40% fraction of inspired oxygen (FiO₂ ) mechanical ventilation (MV), and in the hyperoxia group (HG) (n = 50), PaO₂ was ≥180 mmHg with 100% FiO₂ MV. Hemodynamic parameters, peripheral oxygen saturation (SpO₂ ), regional cerebral oxygen saturation (rSO₂ ) measured from bilateral sensors, and blood gas values were recorded at the planned measurement times. Postoperative features (mortality and infection rates, length of stay in the hospital, and intensive care unit) and complications of the patients have been recorded (low cardiac output syndrome, renal failure, delirium). Mini-Mental State Examination (MMSE) test was applied to the patients before and at the 12th, 24th hours; on the first, third, sixth months after surgery.

RESULTS

Extubation time was found to be shorter in NG (p < .05). Between the groups, rSO₂ and mean arterial pressure were found to be significantly lower in HG at the time of T4 measurement (p = .042, p = .038, respectively). MMSE values of the groups at the first, third, and sixth months were found to be significantly higher in NG (p = .017, p = .014, p = .002, respectively).

CONCLUSION

Hyperoxemia application during CABG may be associated with worse postoperative late-term cognitive functions.

Theta burst stimulation over the prefrontal cortex: Effects on cerebral oximetry and cardiovascular measures in healthy humans

Theta Burst Stimulation (TBS) is a non-invasive neurophysiological technique, able to induce changes in synaptic activity. Research suggests that TBS may induce changes in cerebral oxygenation, cerebral blood flow, blood pressure and heart rate but there are conflicting results across studies. Thus, the objective of our sham-controlled study is to evaluate if TBS applied to the dorsolateral prefrontal cortex (DLPFC) of healthy volunteers produces changes in cerebral oximetry, heart rate and blood pressure. Forty-nine volunteers of both sexes were randomly allocated to one of five stimulation groups. Before and after real TBS or sham stimulation, blood pressure, heart rate, and cerebral oxygenation of the volunteers were measured. Cerebral oxygenation values were obtained with a near infra-red spectroscopy system. We found a significant reduction in left cortex oximetry after continuous TBS (cTBS) over the left DLPFC (p = 0.039) and a non-significant reduction in right cortex oximetry (p = 0.052). Right hemisphere inhibition (using cTBS) seemed to originate a significant reduction of 8 mmHg in systolic arterial pressure. No other changes were seen in oximetry, cardiac frequency and diastolic arterial pressure. In our group of normal subjects, cTBS applied to the left DLPFC was able to reduce oxygenation in the left cortex. Right hemisphere inhibition was associated with a significant reduction in systolic pressure.

THE IMPORTANCE OF NON-INVASIVE REGIONAL BRAIN OXIMETRY IN PREVENTING POSTOPERATIVE COGNITIVE DYSFUNCTION DURING LAPAROSCOPIC CHOLECYSTECTOMY IN ELDERLY AND SENILE PATIENTS

The adverse effect of general anesthesia in elderly patients during surgery requires monitoring of functions and processes to identify their dangerous abnormalities to prevent complications. The aim of the study. To establish the effectiveness of non-invasive regional brain oximetry with rSO2 determination during anesthetic support in laparoscopic cholecystectomy (LCE) to prevent postoperative cognitive dysfunction in elderly and senile patients. Material and methods. 84 elderly and senile patients with diagnosed gallstone disease, acute cholecystitis, who underwent LCE with sevofluran inhalational anesthesia and total intravenous anesthesia with propofol were examined. rSO2 was monitored. Cognitive functions were assessed using neuropsychological scales and the MMSE mental state examination scale. Results. rSO2 was found to be significantly decreased during the carbon dioxide insufflation as compared to before premedication: in LH (left hemisphere) – by 7.0 %, in RH (right hemisphere) – by 6.9 % (Group I); in LH – by 7.4 %, in RH – by 7.5 % (Group II). rSO2 was significantly increased during the surgery, particularly in the middle of the operation, as compared to before premedication: in LH – by 14.66 %, in RH – by 13.94 % (Group I); in LH – by 11.60 %, in RH – by 11.53 % (Group II). The day following the surgery, cognitive functions significantly decreased by 8.7 % on the Luria's test, by 6.0 % on the MMSE test (Group I); in Group II – by 10.1 % and 6.3 %, respectively, as compared to before premedication. On Day 5 after the surgery, cognitive functions decreased by 2.7 % on the Luria's test, by 0.35 % on the MMSE test (Group I); in Group II – by 2.7 % and 0.35 %, respectively, as compared to before premedication. Conclusions. A decrease in rSO2 can occur during LCE in the Trendelenburg position, despite the fact that other intraoperative indicators remain stable, which allows it to remain unrecognized. rSO2 monitoring in the perioperative period contributes to alertness and timely measures to prevent postoperative cognitive dysfunction.

Comparison of effects of low-flow and normal-flow anesthesia on cerebral oxygenation and bispectral index in morbidly obese patients undergoing laparoscopic sleeve gastrectomy: a prospective, randomized clinical trial

Introduction

The effects of low-flow anesthesia on cerebral oxygenation in high-risk, morbidly obese patients are not well known.

Aim

In this prospective randomized study, we compared the effects of low-flow (0.75 l/min) and normal-flow (1.5 l/min) anesthesia on regional cerebral oxygen saturation (rSO₂) and the bispectral index (BIS) in morbidly obese patients undergoing laparoscopic bariatric surgery.

Material and methods

Fifty-two morbidly obese patients undergoing laparoscopic bariatric surgery (sleeve gastrectomy) were enrolled in this study. Patients were randomly allocated to two study groups: low-flow and normal-flow anesthesia groups. Heart rate, mean arterial pressure, peripheral oxygen saturation, end-tidal carbon dioxide, BIS, left and right rSO₂, and duration of anesthesia and surgery were recorded.

Results

The groups were similar with respect to age, gender, height, weight, body mass index, American Society of Anesthesiology physical status, heart rate, duration of anesthesia, and procedure. Mean arterial pressure and end-tidal carbon dioxide, both before and after insufflation of carbon dioxide and after the reverse Trendelenburg position, were significantly higher in the low-flow group. BIS values and left and right rSO₂ during the preoperative and intraoperative periods were similar. Although the difference in right rSO₂ between the two groups after awakening from anesthesia was statistically significant, the results of both groups remained within the normal range and were not clinically meaningful.

Conclusions

Low-flow anesthesia is safe regarding hemodynamic and respiratory characteristics, depth of anesthesia, and regional cerebral oxygen saturation in morbidly obese patients undergoing laparoscopic bariatric surgery.