Detection of cerebral hypoperfusion with bispectral index during paediatric cardiac surgery

Use of bispectral index for detection of partial cerebral hypoperfusion during cervical spine surgery: A case report

The BIS value may decrease by cerebral hypoperfusion. We report a case in which the BIS value suddenly decreased during cervical spine surgery, which led us to find cervical screws compressing the vertebral arteries. In a 79-year-old man undergoing cervical spine surgery, the BIS suddenly decreased from about 40 to 10-20, about 4 h after the start of surgery. Intraoperative 3-dementional computed tomography indicated that both the two tips of cervical screws inserted in the 6th cervical vertebra were within bilateral transverse foramens. These cervical screws were removed, and the BIS increased immediately. The cervical screws were re-inserted again thorough the same vertebra into the bilateral transverse foramens, and the BIS decreased immediately. Postoperatively, cerebral hypoperfusion due to compression of bilateral vertebral arteries by two cervical screws was identified. The BIS may be a useful to detect cerebral hypoperfusion due to compression of the vertebral artery by a cervical screw.

The use of processed electroencephalography (pEEG) in obstetric anaesthesia: a narrative review

Accidental awareness under general anaesthesia (AAGA) remains a major complication of anaesthesia. The incidence of AAGA during obstetric anaesthesia is high relative to other specialities. The use of processed electroencephalography (pEEG) in the form of "depth of anaesthesia" monitoring has been shown to reduce the incidence of AAGA in the non-obstetric population. The evidence for using pEEG to prevent AAGA in the obstetric population is poor and requires further exploration. Furthermore, pregnancy and disease states affecting the central nervous system, such as pre-eclampsia, may alter the interpretation of pEEG waveforms although this has not been fully characterised. National guidelines exist for pEEG monitoring with total intravenous anaesthesia and for "high-risk" cases regardless of technique, including the obstetric population. However, none of the currently available guidelines relates specifically to obstetric anaesthesia. Using pEEG monitoring for obstetric anaesthesia may also provide additional benefits beyond a reduction in risk of AAGA. These potential benefits include reduced postoperative nausea and vomiting, reduced anaesthetic agent use, a shorter post-anaesthetic recovery stay. In addition, pEEG acts as a surrogate marker of cerebral perfusion, and thus as an additional monitor for impending cardiovascular collapse, as seen in amniotic fluid embolism. The subtle physiological and pathological changes in EEG activity that may occur during pregnancy are an unexplored research area in the context of anaesthetic pEEG monitors. We believe that the direction of clinical practice is moving towards greater use of pEEG monitoring and individualisation of anaesthesia.

Associations among preoperative transthoracic echocardiography variables and cerebral near-infrared spectroscopy values at baseline before anesthesia in patients undergoing cardiac surgery: a retrospective observational study

Cerebral tissue oximetry with near-infrared spectroscopy (NIRS) is used to monitor cerebral oxygenation during cardiac surgery. To date, reduced baseline cerebral NIRS values have been attributed to reduced cerebral blood flow primarily based on a significant positive correlation between left ventricular ejection fraction (LVEF) and baseline rSO₂ measured with the INVOS 5100C oximeter. Reportedly, however, rSO₂, but not StO₂ measured with the FORESIGHT Elite oximeter, correlated with LVEF. We, thus, investigated associations among baseline NIRS values measured with three different oximeters before anesthesia for cardiac surgery and preoperative transthoracic echocardiography (TTE) variables, including LVEF, to examine whether there are inter-device differences in associations among baseline NIRS values and TTE variables. Using Spearman's correlation coefficient, we retrospectively investigated associations among 15 preoperative TTE variables, including LVEF, and baseline NIRS values, including rSO₂, StO₂, and TOI with the NIRO-200NX oximeter in 1346, 515, and 301 patients, respectively. Only rSO₂ (p < 0.00001), but not TOI or StO₂ (p > 0.05), positively correlated with LVEF. On the other hand, baseline rSO₂, TOI, and StO₂ consistently, negatively correlated with the left atrial diameter index (LADI), early diastolic transmitral flow velocity (E), E-to-early diastolic mitral annular velocity ratio (E/e'), estimated right ventricular systolic pressure (eRVP), and inferior vena cava diameter index (IVCDI) (p < 0.0005 to p < 0.00001). Because all of these five TTE variables could be positively associated with right as well as left ventricular filling pressure, our results indicated that reduced baseline NIRS values were consistently associated not with reduced LVEF but with TTE findings indicative of elevated biventricular filling pressure. Our data suggest that regional venous congestion greatly contributes to reduced baseline NIRS values in patients undergoing cardiac surgery.

The association of bispectral index values and metrics of cerebral perfusion during cardiopulmonary bypass

STUDY OBJECTIVE

Low bispectral index (BIS) values have been associated with adverse postoperative outcomes. However, trials of optimizing BIS by titrating anesthetic administration have reported conflicting results. One potential explanation is that cerebral perfusion may also affect BIS, but the extent of this relationship is not clear. Therefore, we examined whether BIS would be associated with cerebral perfusion during cardiopulmonary bypass, when anesthetic concentration was constant.

DESIGN

Observational cohort study.

SETTING

Cardiac operating room.

PATIENTS

Seventy-nine patients with cardiopulmonary bypass surgery were included.

MEASUREMENTS

Continuous BIS, mean arterial blood pressure (MAP), cerebral blood flow velocity (CBFV), and regional cerebral oxygen saturation (rSO₂) were monitored, with analysis during a period of constant anesthetic. Mean flow index (Mx) was calculated as Pearson correlation between MAP and CBFV. The lower limit of autoregulation (LLA) was identified as the MAP value at which Mx increased >0.4 with decreasing blood pressure. Postoperative delirium was assessed using the 3D-Confusion Assessment Method.

RESULTS

Mean BIS was lower during periods of MAP < LLA compared with BIS when MAP>LLA (mean 49.35 ± 10.40 vs. 50.72 ± 10.04, p = 0.002, mean difference = 1.38 [standard error: 0.42]). There was a dose response effect, with the BIS proportionately decreasing as MAP decreased below LLA (β = 0.15, 95% CI for the average slope across all patients 0.07 to 0.23, p < 0.001). In contrast, BIS was relatively unchanged when MAP was above LLA (β = 0.03, 95% CI for the average slope across all patients -0.02 to 0.09, p = 0.22). Additionally, increasing CBFV and rSO₂ were associated with increasing BIS. Patients with postoperative delirium had lower mean BIS and higher percentage of time duration with BIS <45 compared to patients without delirium.

CONCLUSIONS

There was an association of BIS and metrics of cerebral perfusion during a period of constant anesthetic administration, but the absolute magnitude of change in BIS as MAP decreased below the LLA was small.

A Review of Bispectral Index Utility in Neurocritical Care Patients

Context: Bispectral Index (BIS) was introduced in 1960 to monitor the depth of anesthesia in the operating rooms. It has been recently used to monitor the sedation in the critically ill patients hospitalized in intensive care and neurocritical care units (NCCU). Evidence Acquisition: Patients in the NCCU, particularly those with prolonged mechanical ventilation require appropriate adjustments in the administration of sedative drugs. Similarly, those who require neuro protection with barbiturates need to be closely monitored in the depth of their coma. Results: BIS may be a useful tool in this situation, and it can also help shorten the duration of mechanical ventilation by determining the appropriate time to eliminate patients from mechanical ventilation. We conducted a literature search to evaluate the utility of BIS monitoring in the NCCU patients with subarachnoid hemorrhage, intracranial hemorrhage, coma, cerebral hypoxia, status epilepticus and traumatic brain injury. Conclusions: BIS monitoring may be a useful adjunct to take care of the patients. However, further studies with a larger population and better design are required to substantiate the role of BIS monitoring in the care of NCCU patients.

Agreement between frontal and occipital regional cerebral oxygen saturation in infants during surgery and general anesthesia an observational study

BACKGROUND

Advances in perioperative pediatric care have resulted in an increased number of procedures requiring anesthesia. During anesthesia and surgery, the patient is subjected to factors that affect the circulatory homeostasis, which can influence oxygenation of the brain. Near-infrared spectroscopy (NIRS) is an easy applicable noninvasive method for monitoring of regional tissue oxygenation (rScO₂%). Alternate placements for NIRS have been investigated; however, no alternative cranial placements have been explored.

AIM

To evaluate the agreement between frontal and occipital recordings of rScO₂% in infants using INVOS^TM during surgery and general anesthesia.

METHOD

A standard frontal monitoring of rScO₂% with NIRS was compared with occipital rScO₂% measurements in fifteen children at an age <1 year, ASA 1-2, undergoing cleft lip and/or palate surgery during general anesthesia with sevoflurane. An agreement analysis was performed according to Bland and Altman.

RESULTS

Mean values of frontal and occipital rScO₂% at baseline were largely similar (70.7 ± 4.77% and 69.40 ± 5.04%, respectively). In the majority of the patients, the frontal and occipital recordings of rScO₂ changed in parallel. There was a moderate positive correlation between frontal and occipital rScO₂% INVOS™ readings (rho[ρ]: 0.513, P < .01). The difference between frontal and occipital rScO₂ ranged from -31 to 28 with a mean difference (bias) of -0.15%. The 95% limit of agreement was -18.04%-17.74%. The error between frontal and occipital rScO₂ recordings was 23%.

CONCLUSION

The agreement between frontal and occipital recordings of brain rScO₂% in infants using INVOS^TM during surgery and general anesthesia was acceptable. In surgical procedures where the frontal region of the head is not available for monitoring, occipital recordings of rScO₂% could be an option for monitoring.

The maximum value of bispectral index predicts outcome in hypoxic-ischemic encephalopathy after resuscitation, better than minimum or mean value

OBJECTIVE

Although bispectral index (BIS) has been widely used for predicting neurological outcomes in clinical practice, its optimal value concerning maximum (BIS_max), minimum (BIS_min) and mean (BIS_mean) on accurately predicting the prognosis of patients with hypoxic-ischemic encephalopathy (HIE) after resuscitation has not been clearly determined.

METHODS

For a total number of 45 cases, the duration of each BIS measurement was 12 h, with the data collected at a 30 min interval. Outcome was recorded as survival and non-survival count 60 days after the resuscitation. Receiver operator characteristic curve was used to assess the BIS_max, BIS_min and BIS_mean for predicting clinical outcome.

RESULTS

By the end of observation, 20 cases (44.4%) survived with a significantly higher BIS_max. The area under the curve for BIS_max of predicting survival was the highest compared to BIS_min and BIS_mean. The optimal cut-off value of BIS_max was 71.5 with 100% sensitivity and 60% specificity. Ten patients presented BIS value down to zero at any time point did not survive the observation.

CONCLUSION

The BIS_max is a better outcome predictor than BIS_min or BIS_mean for patients with HIE after resuscitation. Lower BIS_max represents higher risk of mortality. Additionally, BIS value decreases to zero represents a poor outcome.

Bispectral index as a possible early marker of cerebral hypoperfusion

We report a case of unexplained transient ventricular fibrillation in a child with ventricular septal defect (VSD) scheduled for VSD closure. The bispectral index (BIS) values dropped within 15s of transient cardiac arrest and it showed recovery within 15 s of restoration of circulation. Monitoring BIS during surgery, especially cardiac surgeries may help identify periods of cerebral ischemia early.

Effect of beach chair position on bispectral index values during arthroscopic shoulder surgery

Background

Bispectral index (BIS) monitoring reduces the cases of intraoperative awareness. Several factors can alter BIS readings without affecting the depth of anesthesia. We conducted a study to assess the impact of beach chair position (sitting position) on BIS readings.

Methods

General anesthesia was administered to 30 patients undergoing arthroscopic shoulder surgery. Patients were kept in neutral position (supine) for 10 minutes and BIS readings, mean arterial blood pressure, heart rate, end-tidal carbon dioxide, and end-tidal sevoflurane were recorded. Patients were then shifted to beach chair position. After 15 minutes, data were recorded.

Results

A significant decrease in BIS values (P < 0.01) associated with a position change from neutral position to beach chair position was evident.

Conclusions

BIS values are significantly decreased in the beach chair position compared with the neutral position and might affect interpretation of the depth of anesthesia.

Entropy as an indicator of cerebral perfusion in patients with increased intracranial pressure

Changes in electroencephalogram (EEG) patterns correlate well with changes in cerebral perfusion pressure (CPP) and hence entropy and bispectral index values may also correlate with CPP. To highlight the potential application of entropy, an EEG-based anesthetic depth monitor, on indicating cerebral perfusion in patients with increased intracranial pressure (ICP), we report two cases of emergency neurosurgical procedure in patients with raised ICP where anesthesia was titrated to entropy values and the entropy values suddenly increased after cranial decompression, reflecting the increase in CPP. Maintaining systemic blood pressure in order to maintain the CPP is the anesthetic goal while managing patients with raised ICP. EEG-based anesthetic depth monitors may hold valuable information on guiding anesthetic management in patients with decreased CPP for better neurological outcome.

Effects of acute bleeding followed by hydroxyethyl starch 130/0.4 or a crystalloid on propofol concentrations, cerebral oxygenation, and electroencephalographic and haemodynamic variables in pigs

Bleeding changes the haemodynamics, compromising organ perfusion. In this study, the effects of bleeding followed by replacement with hydroxyethyl starch 130/0.4 (HES) or lactated Ringer's (LR) on cerebral oxygenation and electroencephalogram-derived parameters were investigated. Twelve young pigs under propofol-remifentanil anaesthesia were bled 30 mL/kg and, after a 20-minute waiting period, volume replacement was performed with HES (GHES; N = 6) or LR (GRL; N = 6). Bleeding caused a decrease of more than 50% in mean arterial pressure (P < 0.01) and a decrease in cerebral oximetry (P = 0.039), bispectral index, and electroencephalogram total power (P = 0.04 and P < 0.01, resp.), while propofol plasma concentrations increased (P < 0.01). Both solutions restored the haemodynamics and cerebral oxygenation similarly and were accompanied by an increase in electroencephalogram total power. No differences between groups were found. However, one hour after the end of the volume replacement, the cardiac output (P = 0.03) and the cerebral oxygenation (P = 0.008) decreased in the GLR and were significantly lower than in GHES (P = 0.02). Volume replacement with HES 130/0.4 was capable of maintaining the cardiac output and cerebral oxygenation during a longer period than LR and caused a decrease in the propofol plasma concentrations.

Effect of mild hypocapnia on hemodynamic and bispectral index responses to tracheal intubation during propofol anesthesia in children

The purpose of this study was to investigate the effect of mild hypocapnia on hypertension and arousal response after tracheal intubation in children during propofol anesthesia. Forty-four children, American Society of Anesthesiologists physical status I-II patients, aged 3-9 years were randomly allocated to either the normocapnia group [end-tidal carbon dioxide tension (ETCO2=35 mmHg, n=22)] or the hypocapnia group (ETCO2=25 mmHg, n=22). Anesthesia was induced with propofol 2.5 mg/kg. Five minutes after the administration of rocuronium 0.6 mg/kg, laryngoscopy was attempted. The mean arterial pressure (MAP), heart rate (HR), SpO2 and bispectral index (BIS) were measured during induction and intubation periods. The maximal change in the BIS with tracheal intubation (ΔBIS) was defined as the difference between the baseline value and the maximal value within the first 5 min after intubation. Before tracheal intubation, the change in BIS over time was not different between the groups. After tracheal intubation, the changes in the MAP, HR and BIS over time were not significantly different between the groups. The mean value±SD of ΔBIS was 5.7±5.2 and 7.4±5.5 in the normocapnia and hypocapnia groups, respectively, without any intergroup difference. This study showed that mild hypocapnia did not attenuate hemodynamic and BIS responses to tracheal intubation in children during propofol anesthesia. Our results suggested that hyperventilation has no beneficial effect on hemodynamic and arousal responses to tracheal intubation in children.

Decrease in bispectral index prior to cardiovascular collapse during Caesarean sections

We report a case of significant reduction in bispectral index (BIS) associated with suspected amniotic fluid embolism (AFE) that occurred prior to change in haemodynamic variables. The patient was a 29-year-old nulliparous, who was admitted for Caesarean section under general anaesthesia in the 33rd week of pregnancy. After the baby was born, the BIS value suddenly decreased to 0, with suppression ratio of 100. One minute later, saturation decreased abruptly to 85%, end-tidal carbon dioxide (EtCO2) decreased to 5 mmHg, peak inspiratory pressure increased to 35 cm H2O, and non-invasive blood pressure (BP) failed to obtain a reading. After administration of vasoactive drugs, the systolic BP was maintained at 100 mmHg or higher, the BIS value rose to 10-20, and the EtCO2 increased to 24-33 mmHg. In this case, the BIS monitoring may provide an earlier warning of impending cardiovascular collapse in the case of AFE.

[Usefulness of Bispectral Index (BIS) monitoring for early detection of cerebral hypoperfusions]

OBJECTIVES

The goal of the study was to assess whether clinically significant cerebral hypoperfusion in awake patients would be associated with some alterations in the values of the bispectral index (BIS) monitoring.

STUDY DESIGN

Observational study.

POPULATION AND METHODS

We monitored the BIS during endovascular carotid artery occlusion testing in awake patients.

RESULTS

Twenty-eight patients were included. Twenty-one adequately tolerated the procedure. Their BIS value remained stable throughout the procedure. Four patients had poor angiographic tolerance, but no clinical symptoms. Their BIS value slightly decreased during the test (minimal BIS: 83 [79-87]). Three patients had poor clinical and angiographic tolerance of the occlusion. They all experienced an immediate and dramatic decrease in their BIS value (minimal BIS: ipsilateral to clamping: 50 [45-60]; contralateral to clamping: 48 [45-52]). In all patients, the clinical symptoms and the BIS normalized after deflating the occlusion balloon.

CONCLUSION

In awake patients, the observed values of the BIS monitoring seem to be associated with clinically relevant cerebral hypoperfusion.

Cerebral oxygenation monitoring of patients during arthroscopic shoulder surgery in the sitting position

Background

Cerebral hypotension and desaturation can occur during shoulder surgery in the seated position. We evaluated the correlation of cerebral oxygen saturation (rSO₂) using near infra-red spectroscopy (NIRS) and mean arterial pressures (MAP) (at the levels of the brain and heart).

Methods

Fifty patients, scheduled for the arthroscopic shoulder surgery in the seated position, were enrolled to monitor the rSO₂, bispectral Index (BIS), and MAPs at the levels of the brain and heart. The values of each parameter were collected at 5 min after intubation, immediately after placing the patient in the sitting position, 5 min after the patient was seated, immediately after the surgical incision, and every 30 min after incision.

Results

A correlation between the cerebral rSO₂ and the MAP at the level of brain were statistically significant. Cerebral rSO₂ and MAP after a change of posture from supine to sitting position were significantly decreased, compared to the baseline value.

Conclusions

Monitoring cerebral rSO₂ and MAP at the level of brain can be helpful to detect the possibility of cerebral deoxygenation earlier.

Influence of progressive hemorrhage and subsequent cardiopulmonary resuscitation on the bispectral index during isoflurane anesthesia in a swine model

BACKGROUND

The bispectral index for measurement of anesthetic depth may be modified by extreme hypotension during hemorrhagic shock. In this study, the influence of progressive hemorrhage and subsequent cardiopulmonary resuscitation on the bispectral index was investigated under controlled anesthetic depth.

METHODS

Fifteen swine were anesthetized through inhalation of isoflurane under bispectral index monitoring. Hemorrhagic shock was induced using a stepwise hemorrhage model in which 20%, 10%, and 10% of estimated blood volume were removed over three 30-minute periods and then 5% was removed every 30 minutes until the mean arterial pressure was less than 10 mm Hg. After reaching this criterion, chest compression with 0.2-mg/kg epinephrine and hydroxyethyl starch infusion was performed for 20 minutes or until the mean arterial pressure exceeded 50 mm Hg. The pharmacodynamics of the isoflurane effect was examined before hemorrhage, after 40% bleeding, and after resuscitation.

RESULTS

A mean (SD) volume of 836 (78) mL of blood was drained before resuscitation. The bispectral index suddenly decreased at a mean (SD) arterial pressure of 22 (3) mm Hg and showed isoelectric activity in most animals before resuscitation. Eight pigs were resuscitated, and the bispectral index recovered during a range of periods after recovery of the mean arterial pressure. The pharmacodynamic effect of isoflurane did not change after 40% bleeding but increased after resuscitation, with the alteration correlated with the time for resuscitation.

CONCLUSION

In hemorrhagic shock, the bispectral index merely reflects the anesthetic depth until development of lethal hypotension at which brain electrical activity cannot be sustained. After recovery from depression, the potency of isoflurane can increase depending on the cerebral hypoperfusion time. The increased bispectral index for anesthetics after resuscitation might reflect the degree of cerebral damage due to hypoperfusion.

Cerebral hypoperfusion during pediatric cardiac surgery detected by combined bispectral index monitoring and transcranial doppler ultrasonography

Bispectral index monitoring (BIS) measures depth of anesthesia and sedation. The case of a neonatal patient who underwent surgical repair for a double aortic arch is presented. During surgery, BIS decreased to 0, and cerebral blood flow (CBF), as measured by transcranial doppler ultrasonography, could not be detected immediately after clamping of the arch. BIS returned to baseline, and CBF was detected only after the aortic arch was unclamped. The arch was then carefully reclamped during close BIS and CBF monitoring.

Changes in BiSpecteral Index (BiS) Values During Cardiopulmonary Bypass (CPB)

BACKGROUND

BiSpecteral Index (BiS) monitoring is standard monitoring regimen in anaesthesia practice. It has also been used in cardiac surgery. It is especially important due to the high incidence of neurological injury or dysfunction that occurs following CPB. This is a retrospective study of 33 cases that were monitored with BiS during the course of coronary artery or valvular surgery, including the period of CPB.

METHODS

Thirty three cases monitored with BiS were studied retrospectively.

RESULT

From the recordings it was determined that the value of BiS which was ranging between 40 to 60 after induction, dropped below 25 at the onset of CPB. This change was statistically significant (p<0.05).

CONCLUSION

This decrease in the BiS value is probably a result of hypo-perfusion and due to clear, oxygen - poor priming fluid reaching the brain. Other periods of hypotension also correlated with the low values of BiS. This cerebral hypoxia which would occur at this time could be the cause of the incidence of neurological dysfunction that is known to occur following CPB.

Neurocognitive monitoring and care during pediatric cardiopulmonary bypass-current and future directions

Neurologic injury in patients with congenital heart disease remains an important source of morbidity and mortality. Advances in surgical repair and perioperative management have resulted in longer life expectancies for these patients. Current practice and research must focus on identifying treatable risk factors for neurocognitive dysfunction, advancing methods for perioperative neuromonitoring, and refining treatment and care of the congenital heart patient with potential neurologic injury. Techniques for neuromonitoring and future directions will be discussed.

Monitoring the depth of anaesthesia

One of the current challenges in medicine is monitoring the patients’ depth of general anaesthesia (DGA). Accurate assessment of the depth of anaesthesia contributes to tailoring drug administration to the individual patient, thus preventing awareness or excessive anaesthetic depth and improving patients’ outcomes. In the past decade, there has been a significant increase in the number of studies on the development, comparison and validation of commercial devices that estimate the DGA by analyzing electrical activity of the brain (i.e., evoked potentials or brain waves). In this paper we review the most frequently used sensors and mathematical methods for monitoring the DGA, their validation in clinical practice and discuss the central question of whether these approaches can, compared to other conventional methods, reduce the risk of patient awareness during surgical procedures.

Bispectral index variations in patients with neurological deficits during awake carotid endarterectomy

BACKGROUND AND OBJECTIVE

The bispectral index (BIS) is derived from the EEG and therefore may be useful to diagnose intraoperative cerebral ischaemia. This study was undertaken to investigate BIS changes in awake patients with and without neurological deficits during carotid endarterectomy under regional anaesthesia.

METHODS

Seventy consecutive carotid endarterectomies under regional anaesthesia were divided into two surgical groups: patients with and patients without neurological deficits. Patients' neurological status was evaluated and neurological deficits were compared with BIS values. Measurements were made at different surgical stages: baseline, after sedation, at the beginning of surgery, at preclamping, at the 3 min clamping test, during shunt insertion, at declamping, 15 min after declamping and at the end of surgery. We performed intergroup and intragroup comparisons of BIS values. A decrease in BIS of at least 10 associated with neurological deficits was taken as the cut-off point for the classification of patients with logistic regression models (crude and adjusted for potential confounders).

RESULTS

Thirteen patients (18.6% of the total) developed clinical cerebral ischaemia, though BIS values decreased in 10 of these patients (76.9%). The mean BIS values were 92.5+/-5.6 and 84.7+/-12.3 for patients without and with neurological deficits, respectively (P value<0.05). The odds ratios of a BIS decrease associated with neurological deficits were 8.5 (95% confidence interval 2.1-35.1) and 5.4 (95% confidence interval 1.2-24.3) adjusted for contralateral stenosis.

CONCLUSION

Our results describe a relationship between BIS reductions and neurological deficits during carotid surgery in awake patients.

[Cerebral oximetry monitoring during bypass surgery: can the approach be changed?]

We describe the detection of postoperative neurologic complications by means of monitoring cerebral oximetry during cardiac surgery. A 54-year-old man underwent emergency surgery for aortic dissection, type A. Cerebral oximetry was monitored by near-infrared spectroscopy. At the start of total cardiopulmonary bypass through the axillary artery, cerebral oxygen saturation fell more than 50% from baseline in both hemispheres. Saturation did not improve on optimizing factors that influence cerebral blood flow. Improvement came only when the recently inserted arterial cannula was switched to the ascending aortic prosthetic graft. After surgery, the patient was diagnosed with anoxic brain injury. We believe that the detected fall in cerebral oxygen saturation during axillary artery cannulization probably coincided with the occurrence of anoxic brain injury.

Does bilateral bispectral index monitoring (BIS) detect the discrepancy of cerebral reperfusion during carotid endarterectomy?

The case of a 70 year-old man undergoing bilateral carotid endarterectomy (CEA), for whom alterations in his bispectral index (BIS) values were noted during general anesthesia, is presented. Prior to bypass of the internal carotid artery (ICA), there were no significant differences in bilateral BIS values. After bypass of the left ICA, the left BIS increased to approximately 60, while the right BIS remained at 40. Four months later, no such phenomenon was found during a right CEA. BIS is useful in detecting cerebral hypoperfusion during a lower limit of autoregulation. Attaching bilateral BIS monitors may indicate successful reperfusion of cerebral blood flow in CEA.

Index of consciousness and bispectral index values are interchangeable during normotension and hypotension but not during non pulsatile flow state during cardiac surgical procedures: a prospective study

OBJECTIVES

Awareness under anesthesia is an avoidable complication during general anesthesia. Anesthetic depth monitors assist anesthesiologists in providing appropriate levels of anesthesia. Index of consciousness monitoring is a recently introduced monitor in the array of anesthesia depth monitors. The objective of this study was to assess the interchangeability of bispectral index, which is already in clinical use and the recently introduced index of consciousness techniques. The other objective was to assess this interchangeability during normotension, hypotension and during pulseless state in patients undergoing coronary artery bypass graft surgery. This study is a prospective observational study, conducted in a tertiary referral hospital.

MEASUREMENTS AND MAIN RESULTS

Fifteen cardiac surgical patients undergoing off pump and conventional coronary artery bypass under cardiopulmonary bypass participated in the study. Bispectral index and index of consciousness monitoring were carried out simultaneously during various stages of consciousness, and assessed for interchangeability. Bland Altman plotting and 'mountain plot' were used to assess the interchangeability. Eleven in the cohort underwent off pump and the rest (n = 4) conventional coronary artery bypass surgery under cardiopulmonary bypass. A set of 887 data were obtained during the study period. The data were classified as those obtained during normotension, hypotension and pulseless state during cardiopulmonary bypass.

RESULTS

732 sets of data were obtained during normotension, 84 during hypotension and 71 during cardiopulmonary bypass. Overall interchangeability was good, suggested by low bias (0.96), high precision (0.54), r value of 0.7 and P value of <0.0001. It was found that the data obtained during normotension was also interchangeable, suggested by low bias (0.8), high precision (0.54) and r value of 0.7. The data obtained during hypotension was not as highly interchangeable as during normotension-bias 0.4, precision 1.66 and r value of 0.7. The analysis of value during cardiopulmonary bypass suggested non interchangeability (bias 3.87, precision 3.05, r value 0.3 and P value = 0.0067.

CONCLUSIONS

The bispectral index and index of consciousness values may be interchangeable. The interchangeability is better appreciated during normotension and hypotension but not during non pulsatile state of cardiopulmonary bypass.

Bispectral index changes in carotid surgery

BACKGROUND

Intraoperative monitoring of cerebral ischemia with shunting during carotid endarterectomy (CEA) remains controversial. Our objective was to evaluate the sensitivity and specificity of BIS changes during carotid clamping in relation to shunted patients in awake CEA.

METHODS

Eighty CEAs under cervical block were included. There were two patient groups: with clinical signs of cerebral ischemia (shunted patients) and without signs of cerebral ischemia (nonshunted patients). Data were based on bispectral index (BIS) values and neurological monitoring at different surgery time points, with special attention paid during carotid clamping. BIS values were compared between shunted and nonshunted patients. Sensitivity and specificity, along with positive and negative predictive values of a percentage BIS value decrease during carotid clamping from baseline BIS values, were calculated in both patient groups.

RESULTS

Shunting was performed in 11 patients with cerebral ischemia at carotid clamping. Mean BIS values were 82.82+/-11.98 in shunted patients and 92.31+/-5.42 in nonshunted patients at carotid clamping (p<0.001). Relative decreased BIS values in relation to basal BIS values were 13.57% in shunted patients and 3.68% in nonshunted patients (p<0.05). The percentage decrease in BIS was 14%, sensitivity was 81.8% (95% CI 49.9-96.8), and specificity was 89.7% (95% CI 79.3-95.4).

CONCLUSION

BIS monitoring during carotid clamping is an easy, noninvasive method which correlates with cerebral ischemia in patients undergoing CEA. A decrease>or=14% from the basal BIS value presents a high negative predictive value, and ischemia is unlikely without a decrease. Nonetheless, a decrease may not always indicate cerebral ischemia with a low positive predictive value.

Adenosine-induced Cardiac Standstill to Facilitate Endovascular Embolisation of Cerebral Arteriovenous Malformations in Children

This report describes three children, aged eight to 11 years, with high-flow cerebral arteriovenous malformations who underwent interventional neuroradiological procedures involving glue (N-butyl cyanoacrylate) embolisation under general anaesthesia. The procedure was facilitated by relative hypotension induced by esmolol infusion and intravenous adenosine boluses. To allow controlled deposition of N-butyl cyanoacrylate into the arteriovenous malformations, glue injection was synchronised with the onset of adenosine-induced brief cardiac standstill. This resulted in satisfactory obliteration of the arteriovenous malformations nidus in all cases. The haemodynamic modulations, including the adenosine-induced brief cardiac standstill, was noted to not affect the BIS values in our patients. All patients had satisfactory obliteration of their arteriovenous malformations and had good neurological outcomes at one-year follow-up.

Early detection of an acute cerebral event during cardiopulmonary bypass using a bispectral index monitor

A case in which the bispectral index monitor underwent an acute change that was most likely the earliest indicator of an intraoperative stroke during replacement of an aortic valve is discussed in this study. The timely response to this intraoperative event may have facilitated a better outcome by virtue of more rapid interventions to limit the severity of the injury.

Efeitos de diferentes frações inspiradas de oxigênio no índice biespectral em cães submetidos à infusão contínua de propofol

Avaliaram-se os efeitos do fornecimento de diferentes frações inspiradas de oxigênio (FiO2) sobre o índice biespectral (BIS) em cães submetidos a infusão contínua de propofol e mantidos em ventilação espontânea. Oito cães foram submetidos a cinco anestesias, diferenciando-se uma da outra pela FiO2 fornecida. Formaram-se cinco grupos denominados G100 (FiO2 = 1); G80 (FiO2 = 0,8); G60 (FiO2 = 0,6); G40 (FiO2 = 0,4) e G20 (FiO2 = 0,21). Os animais foram induzidos à anestesia com propofol na dose necessária para intubação, e, ato contínuo, iniciaram-se a infusão do fármaco e o fornecimento de oxigênio, conforme a FiO2 determinada para cada grupo. As primeiras mensurações (M0) foram efetuadas 30 minutos após o início da infusão do anestésico e, depois, em intervalos de 15 minutos (M15, M30, M45 e M60). A pressão parcial de oxigênio no sangue arterial (PaO2) variou conforme a FiO2, ou seja, quanto maior a FiO2, maior foi a PaO2. Para a pressão parcial de dióxido de carbono no sangue arterial (PaCO2), foram registradas diferenças em M30, no qual G100 foi maior que G20. Não foram observadas diferenças significativas nas variáveis estudadas do BIS. Os intervalos de médias registrados para o BIS foram, para G100, de 68 a 62; G80, de 71 a 58; G60, de 72 a 62; G40, de 76 a 68; e G20, de 77 a 68. Conclui-se que as variáveis relacionadas ao BIS não são afetadas pelo emprego de diferentes FiO2, e sugere-se que o monitoramento pelo BIS foi capaz de detectar alterações no equilíbrio do fluxo sangüíneo cerebral, oriundas das alterações ocasionadas na dinâmica respiratória pelo emprego de diferentes frações inspiradas de oxigênio.

Anesthesia management in a child with PHACE syndrome and agenesis of bilateral internal carotid arteries

This is the first case report of successful anesthesia management in a high-risk neurological procedure in a patient with PHACE syndrome. PHACE syndrome is rare but an important clinical entity. Anesthesiologists should be aware of the neurological, otolaryngogical, and vascular risk associated with this syndrome.

Bispectral index monitoring in pediatric anesthesia

PURPOSE OF REVIEW

Anesthetic management guided by bispectral index monitoring has been demonstrated to facilitate earlier recovery in adults. Recent preliminary data also suggest that titration of drugs to achieve a specific bispectral index value may reduce the incidence of intraoperative awareness in high-risk adults. It is unclear, however, if this technology will benefit children as it is based on an algorithm developed from adults. This article reviews the literature on the use of the bispectral index monitor in children.

RECENT FINDINGS

In recent studies, bispectral index scores were shown to correlate well with sedation scores during conscious and deep sedation in pediatric patients, and also with end-tidal concentrations of inhalation agents in children, although bispectral index values may differ with equipotent doses of different agents. Other studies have shown that titrating anesthetic agents to a specific bispectral index value during general anesthesia in the pediatric age group is associated with the use of lower amounts of anesthetic agents and faster recovery from anesthesia in children over 2 years old. However, the utility of bispectral index monitoring in infants, particularly those less than 6 months old, is questionable, as there is little correlation between bispectral index values and other measures of the depth of anesthesia in this subset of patients.

SUMMARY

Bispectral index monitoring may be used to guide anesthetic administration in older children, but its use as a tool for guiding sedation in the younger pediatric patient needs further investigation. It may be necessary to develop a different bispectral index algorithm for children in the younger age groups.

Cerebrovascular resuscitation after polytrauma and fluid restriction

BACKGROUND

There are few reproducible models of blast injury, so it is difficult to evaluate new or existing therapies. We developed a clinically relevant polytrauma model to test the hypothesis that cerebrovascular resuscitation is optimized when intravenous fluid is restricted.

STUDY DESIGN

Anesthetized swine (42+/-5 kg, n=35) received blasts to the head and bilateral chests with captive bolt guns, followed by hypoventilation (4 breaths/min; FiO(2)=0.21). After 30 minutes, resuscitation was divided into phases to simulate typical prehospital, emergency room, and ICU care. For 30 to 45 minutes, group 1, the control group (n=5), received 1L of normal saline (NS). For 45 to 120 minutes, additional NS was titrated to mean arterial pressure (MAP) > 60 mmHg. After 120 minutes, mannitol (1g/kg) and phenylephrine were administered to manage cerebral perfusion pressure (CPP) > 70 mmHg, plus additional NS was given to maintain central venous pressure (CVP) > 12 mmHg. In group 2 (n=5), MAP and CPP targets were the same, but the CVP target was>8 mmHg. Group 3 (n=5) received 1 L of NS followed only by CPP management. Group 4 (n=5) received Hextend (Abbott Laboratories), instead of NS, to the same MAP and CPP targets as group 2.

RESULTS

Polytrauma caused 13 deaths in the 35 animals. In survivors, at 30 minutes, MAP was 60 to 65 mmHg, heart rate was >100 beats/min, PaO(2) was < 50 mmHg, and lactate was>5 mmol/L. In two experiments, no fluid or pressor was administered; the tachycardia and hypotension persisted. The first liter of intravenous fluid partially corrected these variables, and also partially corrected mixed venous O(2), gastric and portal venous O(2), cardiac output, renal blood flow, and urine output. Additional NS (total of 36+/-1 mL/kg/h and 17+/-6 mL/kg/h, in groups 1 and 2, respectively) correlated with increased intracranial pressure to 38+/-4 mmHg (group 1) and 26+/-4 mmHg (group 2) versus 22+/-4 mmHg in group 3 (who received 5+/-1 mL/kg/h). CPP was maintained only after mannitol and phenylephrine. By 5 hours, brain tissue PO(2) was>20 mmHg in groups 1 and 2, but only 6+/-1 mmHg in group 3. In contrast, minimal Hextend (6+/-3 mL/kg/h) was needed; the corrections in MAP and CPP were immediate and sustained, intracranial pressure was lower (14+/-2 mmHg), and brain tissue PO(2) was> 20 mmHg. Neuropathologic changes were consistent with traumatic brain injury, but there were no statistically significant differences between groups.

CONCLUSIONS

After polytrauma and resuscitation to standard MAP and CPP targets with mannitol and pressor therapy, we concluded that intracranial hypertension was attenuated and brain oxygenation was maintained with intravenous fluid restriction; cerebrovascular resuscitation was optimized with Hextend versus NS; and longer term studies are needed to determine neuropathologic consequences.

Transient decreases in Bispectral Index without associated changes in the level of consciousness during photic stimulation in an epileptic patient

This case report describes a patient with a history of epileptic seizures who showed unusual decreases in the Bispectral Index (BIS) attributable to the induction of abnormal slow electroencephalographic (EEG) waves by photic stimulation, without any associated decrease in his level of consciousness. After starting anticonvulsive therapy, photic stimulation no longer induced abnormal EEG activity nor decreased BIS values. These findings suggest that BIS values may not accurately reflect a patient's actual level of consciousness in the presence of epilepsy-related abnormal EEG activity and that the BIS monitor may be able to track such EEG changes.

Correlation Of Bispectral Index With Glasgow Coma Score In Mild And Moderate Head Injuries

BACKGROUND

Bispectral Index (BIS) derived from electroencephalogram (EEG) is primarily developed to monitor the depth of unconsciousness. Recent evidence suggests that BIS may also help in the detection of cerebral ischemia and prognostication of outcome of traumatic brain injury (TBI). The present study was designed to investigate the correlation between Glasgow Coma Score (GCS) and BIS in mild and moderate head injury.

METHODS

In 29 patients with mild (GCS 13-15) and moderate (GCS 9-12) head injuries who underwent craniotomy, GCS and BIS were measured before surgery, after surgery and once a day for the first 10 days.

RESULTS

A significant correlation was found between GCS and BIS in the data sets from all the patients (r = 0.67; p < 0.001). Mean BIS values increased with increasing GCS scores. However, the scatter of BIS values for any GCS score was high limiting the value of BIS in predicting GCS. Mean BIS values were significantly different between mild and moderate head injuries [65.7 +/- 16.1 vs. 85.7 +/- 6.1, p = 0.006].

CONCLUSION

In patients with mild and moderate head injury, significant correlation exists between GCS and BIS. But the high degree of scatter of BIS values for any given GCS score limits its use as a monitor of depth of coma in TBI. Further studies are required to understand the relation between BIS algorithm and cerebral electrical activity following TBI to define the role of BIS as an electrophysiological correlate of consciousness in TBI.