Sedation during spinal anesthesia

Effects of Earmuffs and Eye Masks on Propofol Sedation during Spinal Anesthesia for Orthopedic Surgery: A Randomized Controlled Trial

Intravenous sedative drugs are commonly administered during regional anesthesia. However, reducing the excessive use of sedatives while providing adequate sedation is important from the clinical perspective, since the use of sedatives can cause considerable complications. We hypothesized that the application of earmuffs and eye masks would help reduce the sedative dose required to maintain proper sedation by blocking external stimuli. Patients who underwent orthopedic surgery under spinal anesthesia were randomly allocated to the control (no intervention) or intervention group (wearing earmuffs and eye masks). Intravenous sedation was administered using target-controlled infusion of propofol. The target concentration was controlled to maintain a Modified Observer's Assessment of Alertness and Sedation score of 3 or 4. The primary outcome was the intraoperative propofol requirement. We also investigated the incidence of apnea, and patient satisfaction. Propofol requirement was significantly lower in the intervention group than that in the control group (2.3 (2.0-2.7) vs. 3.1 (2.7-3.4) mg·kg^-1·h^-1; p < 0.001). Intraoperative apnea occurred less frequently (p = 0.038) and patient satisfaction was higher (p = 0.002) in the intervention group compared to the control group. This study demonstrated that the use of earmuffs and eye masks during sedation was associated with lower propofol requirement and improved sedation quality.

Fractal Properties of Heart Rate Dynamics: A New Biomarker for Anesthesia-Biphasic Changes in General Anesthesia and Decrease in Spinal Anesthesia

Processed electroencephalogram (EEG) has been considered a useful tool for measuring the depth of anesthesia (DOA). However, because of its inability to detect the activities of the brain stem and spinal cord responsible for most of the vital signs, a new biomarker for measuring the multidimensional activities of the central nervous system under anesthesia is required. Detrended fluctuation analysis (DFA) is a new technique for detecting the scaling properties of nonstationary heart rate (HR) behavior. This study investigated the changes in fractal properties of heart rate variability (HRV), a nonlinear analysis, under intravenous propofol, inhalational desflurane, and spinal anesthesia. We compared the DFA method with traditional spectral analysis to evaluate its potential as an alternative biomarker under different levels of anesthesia. Eighty patients receiving elective procedures were randomly allocated different anesthesia. HRV was measured with spectral analysis and DFA short-term (4-11 beats) scaling exponent (DFAα1). An increase in DFAα1 followed by a decrease at higher concentrations during propofol or desflurane anesthesia is observed. Spinal anesthesia decreased the DFAα1 and low-/high-frequency ratio (LF/HF ratio). DFAα1 of HRV is a sensitive and specific method for distinguishing changes from baseline to anesthesia state. The DFAα1 provides a potential real-time biomarker to measure HRV as one of the multiple dimensions of the DOA.

Midazolam versus Dexmedetomidine in Patients at Risk of Obstructive Sleep Apnea during Urology Procedures: A Randomized Controlled Trial

Benzodiazepines are the most commonly used sedatives for the reduction of patient anxiety. However, they have adverse intraoperative effects, especially in obstructive sleep apnea (OSA) patients. This study aimed to compare dexmedetomidine (DEX) and midazolam (MDZ) sedation considering intraoperative complications during transurethral resections of the bladder and prostate regarding the risk for OSA. This study was a blinded randomized clinical trial, which included 115 adult patients with a mean age of 65 undergoing urological procedures. Patients were divided into four groups regarding OSA risk (low to medium and high) and choice of either MDZ or DEX. The doses were titrated to reach a Ramsay sedation scale score of 4/5. The intraoperative complications were recorded. Incidence rates of desaturations (44% vs. 12.7%, p = 0.0001), snoring (76% vs. 49%, p = 0.0008), restlessness (26.7% vs. 1.8%, p = 0.0044), and coughing (42.1% vs. 14.5%, p = 0.0001) were higher in the MDZ group compared with DEX, independently of OSA risk. Having a high risk for OSA increased the incidence rates of desaturation (51.2% vs. 15.7%, p < 0.0001) and snoring (90% vs. 47.1%, p < 0.0001), regardless of the sedative choice. DEX produced fewer intraoperative complications over MDZ during sedation in both low to medium risk and high-risk OSA patients.

Perioperative sedation requirements of infants aged 0 to 3 months subjected to lower-body surgery under caudal blockade: a randomized controlled trial

BACKGROUND

It remains unclear how much sedation is required for subumbilical surgery under caudal blockade, and sedatives may carry a poorly understood risk of late sequelae in infants. We designed a randomized controlled study to evaluate total propofol consumption and perioperative sedation quality with the avoidance of continuous perioperative sedation in infants undergoing surgery under caudal anesthesia.

METHODS

Thirty-two infants (age: 0-3 months) were randomized to one of two groups in which perioperative administration of propofol was provided either "as needed" or by continuous infusion (5 mg kg-1 h-1). After induction of anesthesia via a facemask with sevoflurane, a venous access was established and 1 ml kg-1 of ropivacaine 0.35% was injected for caudal anesthesia. Intraoperative stress was assessed by repeated recording Comfort Behavioral Scale scores and heart rates.

RESULTS

Significantly (p = 0.0001) less propofol was administered in the as-needed group (0.7 ± 1.4 mg/kg) than in the continuous-infusion group (3.0 ± 1.6 mg/kg). This difference was not reflected in different requirements of additional intraoperative sedation (0.5 ± 0.8 mg/kg in 5 versus 0.6 ± 1.0 mg/kg in 4 cases; p = 0.76).

CONCLUSIONS

As needed propofol administration offers no disadvantage in terms of intraoperative sedation, but significant dose reductions can be achieved by avoiding continuous propofol infusion.

Effect of lumbar epidural blockade and propofol on mean arterial pressure, cardiac output and bispectral index: A randomised controlled and pharmacodynamic modelling study

BACKGROUND

It is generally accepted that a neuraxial blockade strengthens the sedative effects of propofol. Deafferentation caused by neuraxial blockade is thought to play a key role.

OBJECTIVES

The objective is to determine whether epidural blockade affects the bispectral index (BIS) of propofol and two other pharmacodynamic endpoints, mean arterial pressure (MAP) and cardiac output (CO).

DESIGN

Randomised, placebo-controlled study.

SETTING

University hospital.

PATIENTS

Patients scheduled for surgery needing epidural analgesia.

INTERVENTION

28 ASA one or two patients received 0, 50, 100 or 150 mg of epidural ropivacaine. After stabilisation of the epidural blockade, propofol was given by target-controlled infusion. The propofol plasma target concentrations were increased at 6-min intervals from 0 to 1, 2.5, 4 and 6 μg ml-1. The study was performed before surgery.

MAIN OUTCOME MEASURES

Three endpoints, BIS, mean arterial blood pressure and CO were measured from baseline (prior to the administration of epidural ropivacaine) until 2 h after the start of propofol infusion. The propofol concentration-effect data were analysed to determine the interaction between epidural blockade and propofol sedation.

RESULTS

In the absence of propofol, the increase in number of epidural blocked segments from 0 to 15.5 (range 6 to 21) reduced the MAP by 30%, without affecting BIS or CO. In the absence of epidural blockade, the increase in propofol concentration to 6 μg ml-1 reduced BIS, MAP and CO. When combined, epidural anaesthesia and intravenous propofol exhibited no pharmacodynamic interaction on any of the three endpoints. In addition, epidural blockade did not affect the propofol effect-site equilibration half-life for its haemodynamic effects (11.5 ± 0.5 min) or for its effects on the BIS (4.6 ± 0.4 min).

CONCLUSION

Epidural blockade reduces the propofol requirements for sedative end points. This is not the result of a pharmacodynamic interaction.

TRIAL REGISTRATION

Dutch trial register CCMO, Central Committee on Research Involving Human Subjects, trial number NL 32295.058.10.

Effect of intravenous lignocaine infusion on bispectral index during spinal anaesthesia for caesarean section: A prospective randomised double-blind study

Background and Aims:

Systemic lignocaine has been shown to have sedative effects. We designed this randomised-double-blind, placebo-controlled study to evaluate the effect of intravenous lignocaine on the bispectral index (BIS) during caesarean section under spinal anaesthesia.

Methods:

80 patients scheduled for elective caesarean section under spinal anaesthesia were randomly allocated to 2 study groups. Group L received intravenous 1.5 mg/kg of lignocaine bolus, 15 minutes before spinal anaesthesia followed by an intravenous infusion 1.5 mg/kg/h for 60 minutes intravenously. The patients in the control group (C group) were given 0.9% sodium chloride in a double-blind fashion. Spinal anaesthesia was performed with 10 mg of 0.5% bupivacaine. The changes of Sao2, BIS and hemodynamic variables during caesarean section, Apgar score of neonate and the incidence of adverse effects were recorded.

Results:

BIS values were lower in the L group compared to C group (P ≤ 0.001). Comparison of mean arterial pressure (MAP) changes during spinal anaesthesia and surgery reveal statistically significant difference between two groups through repeated measure analysis (P ≤ 0.001), but comparision of heart rate (HR) changes during spinal anaesthesia and surgery failed to reveal any statistically significant difference between two groups. (P = 0.261). The Apgar scores did not reveal a significant difference between the two groups at first and five minutes after delivery (P = 0.99).

Conclusion:

Intravenous lignocaine infusion given with spinal anaesthesia in women undergoing elective caesarean delivery providing lower BIS values without respiratory depression, in the absence of foetal compromise.

Efficacy of the bispectral index and Observer's Assessment of Alertness/Sedation Scale in monitoring sedation during spinal anesthesia: A randomized clinical trial

OBJECTIVE

The bispectral index (BIS) has been used to monitor sedation during spinal anesthesia. We evaluated the correlation between BIS and the Observer's Assessment of Alertness/Sedation Scale (OAA/S) in patients sedated with dexmedetomidine, propofol, or midazolam.

METHODS

This prospective, randomized study included 46 patients scheduled for knee arthroplasty under spinal anesthesia with sedation. The patients were randomized to receive sedation with dexmedetomidine (n = 15), propofol (n = 15), or midazolam (n = 16). Correlation between BIS and OAA/S was assessed during sedation in the three groups.

RESULTS

A linear correlation was observed between BIS and OAA/S, and there was no significant difference in BIS score between the groups during mild to moderate sedation status (OAA/S 3-5). During deep sedation (OAA/S 1-2), the BIS score in the midazolam group was significantly higher than that in the propofol and dexmedetomidine groups (74.4 ± 11.9 vs 67.7 ±  9.5 vs 62.6 ± 12.2).

CONCLUSIONS

BIS values differed at the same level of sedation between different sedative agents. Objective sedation scores should therefore be used in combination with BIS values for the assessment of sedation levels during spinal anesthesia.

Investigation of single-dose thoracic paravertebral analgesia for postoperative pain control after thoracoscopic lobectomy - A randomized controlled trial

BACKGROUND

Thoracoscopic lobectomy is less painful than normal thoracotomy, but pain management is still an issue in the postoperative period. Thoracic epidural analgesia (TEA) is considered as the gold standard for post-thoracotomy pain control, but is associated with numerous risks.

METHODS

A total of 114 patients undergoing thoracoscopic lobectomy were randomly divided into three groups. Patients in the PVB-R group received a single-dose 0.5% ropivacaine paravertebral block (PVB), combined with patient-controlled intravenous analgesia (PCIA) after extubation during the 48-h postoperative period; those in the PVB-RD group received a single-dose 0.5% ropivacaine and dexmedetomidine (1 μg/kg) PVB, combined with the same PCIA scheme; and those in the TEA group received intraoperative thoracic epidural anesthesia with 0.5% ropivacaine, and a single dose of epidural morphine (0.03 mg/kg) after extubation combined with the same PCIA scheme. The dose and first time of postoperative analgesia, verbal rating score (VRS), change in catecholamine, cortisol and cytokine levels, change in hemodynamic parameters, and side effects during the postoperative period were recorded.

RESULTS

Compared to the PVB-R group, the dose of postoperative analgesia and VRS were lower and the first time of postoperative analgesia were longer in the PVB-RD and TEA group. Patients in the PVB-RD group had a lower incidence of side effects compared to those in the TEA group.

CONCLUSIONS

Single-dose 0.5% ropivacaine combined with dexmedetomidine (1 μg/kg) PVB provides satisfactory postoperative pain control after thoracoscopic lobectomy, and can reduce the incidence of postoperative side effects.

Effects of intrathecal bupivacaine on the NR2B/CaMKIIα/CREB signaling pathway in the rat lumbar spinal cord

Neuraxial anesthesia produces an anesthetic-sparing, sedative effect. The mechanism underlying this effect potentially involves decreased spinal afferent input. However, the neurochemical mechanisms at the spinal level remain unknown. The N-methyl-D-aspartate receptor 2B subunit/calcium-calmodulin-dependent protein kinase II α/cAMP response element-binding protein (NR2B/CaMKIIα/CREB) signaling pathway serves an important role in regulating the transmittance of peripheral noxious stimulation to supraspinal regions in the process of nociception. The present study investigated the effects of intrathecal bupivacaine on the NR2B/CaMKIIα/CREB signaling pathway. Following catheterization, 36 male Sprague-Dawley rats were randomly assigned to a normal saline (NS) or bupivacaine treatment group, in which each rat intrathecally received 20 µl normal saline or 0.5% bupivacaine, respectively. The expression levels of NR2B, CaMKIIα/p-CaMKIIα, and CREB/phosphorylated (p)-CREB in the lumbar spinal cord were investigated by western blotting, reverse transcription-quantitative polymerase chain reaction and immunohistochemistry (IHC). Following bupivacaine treatment, western blot analysis demonstrated that the protein expression levels of NR2B, p-CaMKIIα, and p-CREB in the spinal cord were reduced by approximately 54, 56 and 33%, respectively, compared with NS control rats. Similar alterations in expression were observed by IHC analysis. Additionally, mRNA expression levels of NR2B, CaMKIIα, and CREB were also downregulated following the intrathecal administration of bupivacaine. Therefore, the sedative effect of subarachnoid blockade with bupivacaine possibly occurs through de-afferentation, which may reduce cortical arousal by downregulating the spinal NR2B/CaMKIIα/CREB pathway in vivo, however further investigation is required in order to verify this.

Effective Loading Dose of Dexmedetomidine to Induce Adequate Sedation in Parturients Undergoing Caesarean Section Under Spinal Anaesthesia

Objective

To calculate the effective dose (ED) of dexmedetomidine for caesarean section under spinal anaesthesia.

Methods

Consecutive parturients scheduled for caesarean section under spinal anaesthesia were included. The loading dose of dexmedetomidine was evaluated using the up-and-down method, starting at 1.0 μg kg^-1 and a step size of 0.1 μg kg^-1. The loading dexmedetomidine was administrated by the venous route for 10 min, and afterwards a maintenance dose began at a rate of 0.3 μg kg^-1 h^-1 in all parturients. Adequate sedation was defined as a Ramsay sedation score ≥3. The ED50 and ED95 of loading dexmedetomidine were calculated using probit regression.

Results

The ED50 and ED95 of loading dexmedetomidine for adequate sedation were 0.82 μg kg^-1 (95% confidence intervals [CI] 0.73-0.89 μg kg^-1) and 0.96 μg kg^-1 (95% CI 0.90-1.39 μg kg^-1), respectively.

Conclusion

The ED50 and ED95 of loading dexmedetomidine to achieve adequate sedation were 0.82 μg kg^-1 and 0.96 μg kg^-1 for caesarean section under spinal anaesthesia.

Epidural Dexmedetomidine Reduces the Requirement of Propofol during Total Intravenous Anaesthesia and Improves Analgesia after Surgery in Patients undergoing Open Thoracic Surgery

The aim of this study was to assess the systemic and analgesic effects of epidural dexmedetomidine in thoracic epidural anaesthesia (TEA) combined with total intravenous anaesthesia during thoracic surgery. Seventy-one patients undergoing open thoracotomy were included in this study and randomly divided into three groups: Control group (Group C): patients received TEA with levobupivacaine alone and were intravenously infused with saline; Epidural group (Group E): patients received TEA with levobupivacaine and dexmedetomidine, and were intravenously infused with saline; Intravenous group (group V): patients received TEA with levobupivacaine alone and were intravenously infused with dexmedetomidine. The doses of propofol used in the induction and maintenance of general anaesthesia, cardiovascular response, dose and first time of postoperative analgesia and verbal rating scale were recorded. The induction and maintenance were significantly lower in the Groups E and V. Verbal rating scale and postoperative analgesic requirements were significantly lower in Group E than in Groups C and V. Patients in Group C had more severe cardiovascular responses, as compared with Groups E and V. Epidural administration of dexmedetomidine reduced the induction and maintenance of propofol, and inhibited the cardiovascular response after intubation and extubation. Moreover, epidural dexmedetomidine provided better analgesia after open thoracotomy.

Comparison of Intravenous Dexmedetomidine with Midazolam in Prolonging Spinal Anaesthesia with Ropivacaine

INTRODUCTION

Midazolam and dexmedetomidine both being sedatives, but the latter with additional analgesic properties is expected to prolong the duration of sensory and motor block obtained with spinal anaesthesia.

AIM

To compare intravenous dexmedetomidine with midazolam and placebo with respect to sensory and motor block duration, analgesia, and sedation in patients undergoing lower limb and lower abdominal surgeries with intrathecal ropivacaine anaesthesia.

MATERIALS AND METHODS

In this single blind placebo controlled trial, 60 patients, classified as American Society of Anaesthesiologists' (ASA) physical status I-II, were randomized into three groups (n=20 per group). All patients were administered ropivacaine (15 mg) for spinal anaesthesia. Intravenous dexmedetomidine was administered in Group D (1 μg/kg loading dose over 10 minutes, followed by a continuous infusion (0.5 μg/kg/hr), intravenous midazolam was administered in Group M (0.05 mg/kg) loading dose, followed by a continuous infusion (0.02 mg/kg/hr) and normal saline was infused in Group C. Intraoperative haemodynamic changes, onset, level and duration of sensory block, onset and duration of motor block, level of sedation, postoperative analgesia and side effects were recorded.

RESULTS

Heart rate was seen to fall significantly in Group D patients for the first 15 minutes. Measurements of mean blood pressure revealed significant decrease in Group D after 40 minutes, whereas the fall in Group C occurred after 15 minutes. Duration of sensory block was significantly longer in Group D patients (208±19.358 mins) as compared to Group M and C where the duration was (177±15.252 mins) and (177±17.800 mins) respectively. Higher levels of sedation were achieved in Group D and M where sedation score was 3 (fully asleep but arousable), 90% cases in Group D and 100% cases in Group M. The time at which first analgesic was given to patients (VAS score 4) was (271.50±21.831) in Group D and (202±25.047) in M and (218.50±38.013) in Group C. Dexmedetomidine significantly prolongs duration of analgesia providing pain relief in intraoperative and postoperative period. Injection of diclofenac sodium 75 mg intramuscular was used as rescue analgesic. The VAS score reached a value of 4 earlier in the midazolam and saline group than dexmedetomidine group.

CONCLUSION

Intravenous dexmedetomidine prolonged spinal anaesthesia, though midazolam did not. It also provided sedation and additional analgesia. Therefore, dexmedetomidine is appropriate during spinal anaesthesia, although heart rate needs to be monitored cautiously.

Relation between fentanyl dose and patient state index during spinal anesthesia for elective cesarean section

Background

In spinal anesthesia for cesarean section, the addition of fentanyl to the local anesthetic has been reported to improve perioperative analgesia. However, there is only limited knowledge on sedative effects of the added fentanyl. We examined whether the patient state index® (PSI) can detect and present the light sedated level with patients undergoing cesarean section.

Findings

We measured respiratory rate (RR), SpO2, and PSI values. Between child delivery and the completion of the operation, the proportions of time with the PSI values <90 and 80 were calculated. RR <8 breaths/min or SpO2 <95 % was defined as respiratory depression. Respiratory depression was not observed in any patient. At fentanyl doses of 10, 15, and 20 μg, the proportions of time with the PSI <90 were 14.5 ± 20.8, 49.4 ± 35.3, and 71.1 ± 22.9 %, respectively (P < 0.01). There were significant differences between 10 and 15 μg (P < 0.05), and 10 and 20 μg (P < 0.01). Similarly, the proportions of time with the PSI values <80 were 0.5 ± 1.8, 21.1 ± 24.1, and 31.8 ± 32.2 %, respectively (P < 0.05). There was a significant difference between 10 and 20 μg (P < 0.05).

Conclusions

The PSI values decreased in a dose-dependent manner with increasing dose of fentanyl, but no respiratory depression was observed. The PSI values decreased to less than 90, when fentanyl was administered more than 15 μg. Furthermore, the PSI values decreased to less than 80, when fentanyl was administered 20 μg.

Intravenous dexmedetomidine versus propofol for intraoperative moderate sedation during spinal anesthesia: A comparative study

BACKGROUND AND AIMS

There has been a paradigm shift of focus toward quality of spinal anesthesia with sedation being an integral aspect of this regional anesthesia technique. Thus, this study was designed to compare efficacy of intravenous dexmedetomidine and propofol for moderate sedation during spinal anesthesia.

MATERIAL AND METHODS

A total of 120 patients of age group 18-60 years of American Society of Anesthesiologists grade I & II, posted for surgeries under spinal anesthesia were randomly divided in to three groups (n = 40 each); Group D received infusion of dexmedetomidine 1 μg/kg over 10 min followed by maintenance infusion of 0.5 μg/kg/h. Group P received infusion of propofol 6 mg/kg/h for 10 min followed by the infusion maintenance of 2.5 mg/kg/h. Group C (control group) received normal saline. Level of sedation (using observer's assessment of alertness/sedation score), pain intensity (by visual analogue scale), onset and recovery from sedation, hemodynamic changes, and overall patient's satisfaction were assessed.

RESULTS

The onset and recovery from sedation were significantly earlier with propofol (15.57 ± 1.89 min vs. 27.06 ± 2.26 min; P < 0.001) however intraoperative sedation (level 4), and overall patient's satisfaction was significantly better with dexmedetomidine group (p < 0.05). Duration of postoperative analgesia was significantly prolonged with dexmedetomidine (225.53 ± 5.61 min vs. 139.60 ± 3.03 min; P = 0.0013). Mean heart rate and blood pressure were significantly lower in the propofol group (P < 0.05).

CONCLUSION

Dexmedetomidine with its stable cardio-respiratory profile, better sedation, overall patient's satisfaction, and analgesia could be a valuable adjunct for intraoperative sedation during spinal anesthesia.

Sedation in hypoalbuminemic geriatric patients under spinal anesthesia in hip surgery. Midazolam or Propofol?

Objectives:

To compare midazolam and propofol sedation in hypoalbuminemic geriatric patients under spinal anesthesia in hip surgery with bispectral index monitoring.

Methods:

This prospective and randomized study was completed in the Department of Anesthesiology, Okmeydani Training and Research Hospital, Istanbul, Turkey between February 2013 and December 2014. Sixty patients undergoing elective hip surgery under spinal anesthesia in the geriatric age group with albumin levels below 3 g/dl were randomly divided into Group I and Group II. After administration of spinal block, Group I were given 0.05 mg/kg bolus midazolam, and then 0.02-0.1 mg/kg/hr dose infusion was begun. In Group II, 1 mg/kg bolus propofol was given within 10 minutes, and then 1-3 mg/kg/hr infusion was begun. The systolic arterial pressure, diastolic arterial pressure, mean arterial pressure, heart rate, peripheral oxygen saturation values, respiratory rate, and Wilson’s 5-stage sedation score were recorded at 15-minute intervals. At the end of the operation, the recovery time and surgeon satisfaction were recorded.

Results:

The recovery times for patients in Group I were found to be longer than in Group II (p<0.05). The respiration rate in patients in Group I at the start of surgery, 15th minute of surgery, and after surgery were lower than in Group II (p<0.05).

Conclusion:

We conclude that propofol is more reliable in terms of hemodynamic stability than midazolam, as it causes less respiratory depression and faster recovery in the propofol group.

Modelling of the Sedative Effects of Propofol in Patients undergoing Spinal Anaesthesia: A Pharmacodynamic Analysis

Sedation can increase patient comfort during spinal anaesthesia. Understanding the relationship between the propofol effect-site concentration (Ce) and patient sedation level could help clinicians achieve the desired sedation level with minimal side effects. We aimed to model the relationship between the propofol Ce and adequate and deep sedation and also incorporate covariates. Thirty patients scheduled for orthopaedic surgery received spinal anaesthesia with 0.5% bupivacaine. Propofol was administered via an effect-site target-controlled infusion device using the Schnider pharmacokinetic model. The pharmacodynamic models for both adequate sedation [Observer's Assessment of Alertness/Sedation (OAA/S) scores of 3-4] and deep sedation (OAA/S scores of 1-2) were developed using nonlinear mixed-effects modelling. Increments in the propofol Ce were associated with increased depths of sedation. In the basic model, the estimated population Ce50 values for adequate and deep sedation were 0.94 and 1.52 μg/ml, respectively. The inclusion of the patient's age and sensory block level for adequate sedation and of age for deep sedation as covariates significantly improved the basic model by decreasing the objective function's minimum value from 10696.72 to 10677.92 (p = 0.0003). The simulated Ce50 values for adequate sedation in 20-year-old patients with a T12 sensory level and in 80-year-old patients with a T4 level were 1.63 and 0.53 μg/ml, respectively. Both age and sensory block level should be considered for adequate sedation, and the propofol concentration should be reduced for elderly patients with a high spinal block to avoid unnecessarily deep levels of sedation.

Transient Coma Due To Epidural Anesthesia: The Role of Loss of Sensory Input

Patient: Female, 22

Final Diagnosis: Coma due to loss of sensory input

Symptoms: Coma

Medication: Lidocaine

Clinical Procedure: Epidural

Specialty: Anesthesiology

Intraoperative auditory evoked potential recordings are more reliable at signal detection from different sensor sites on the forehead compared to bispectral index

Bispectral index (BIS) and auditory evoked potential (AEP) monitoring require the attachment of forehead sensors, posing difficulties when the surgical field involves the forehead. This study analyzed the relationship between BIS values and AEP indices from different sites on the head to establish alternative sensor locations for AEP recording. Thirty patients scheduled for elective surgery under sevoflurane anesthesia were randomly assigned to the forehead, nose or mandible groups (n = 10 patients per group). AEP sensors were placed at the assigned position for each group and BIS sensors were placed on the forehead. BIS value and AEP index were simultaneously recorded from induction until emergence from general anesthesia. Relationships between BIS values and AEP indices were analyzed using a regression method and compared between groups using Pearson's correlation coefficients. Square regression models better expressed the relationships than linear models in all groups. The z-transformed coefficient in the forehead group was the same as the nose group (p = 0.24) and significantly different in the mandible group (p = 0.0046). These findings suggest that AEPs can be accurately recorded from sensors placed on the nose. Nasal AEP might be useful for monitoring electrical activity in the brain during surgeries involving the forehead.

Effective dose of dexmedetomidine to induce adequate sedation in elderly patients under spinal anesthesia

Background

During sedation with dexmedetomidine, a dose adjustment may be needed based on the invasiveness of the procedure, the patient's general condition, and their age. We aim here to determine the effective dose (ED) of dexmedetomidine to induce an adequate depth of sedation in elderly patients undergoing spinal anesthesia.

Methods

In this study, 47 patients aged 65 years or older, American Society of Anesthesiologists physical status I or II, undergoing spinal anesthesia were included. Patients were randomly allocated into group I, II, III, IV or V according to the dexmedetomidine loading dose of 0.1, 0.3, 0.5, 0.7 and 1.0 µg/kg, respectively. After spinal anesthesia, the assigned loading dose of dexmedetomidine was infused intravenously for 10 minutes, after which infusion was maintained at a rate of 0.3 µg/kg/h for the next 10 minutes in all groups. We assessed the depth of sedation with the Ramsay sedation scale every five minutes and measured vital signs and the oxygen saturation. The ED₅₀ and ED₉₅ of dexmedetomidine to obtain adequate sedation (Ramsay sedation score ≥ 3) upon the completion of the loading dose were calculated with logistic regression.

Results

The ED₅₀ and ED₉₅ of dexmedetomidine for adequate sedation were 0.29 µg/kg (95% confidence intervals [CI] 0.14-0.44) and 0.86 µg/kg (95% CI 0.52-1.20), respectively. Hypotension was frequent in groups IV, V compared to groups I, II, III (31.6 vs. 3.6%, P = 0.013).

Conclusions

ED₉₅ of dexmedetomidine loading dose for adequate sedation is 0.86 µg/kg. However, dose higher than 0.5 µg/kg can lead to hemodynamic instability.

Adequate sedation with single-dose dexmedetomidine in patients undergoing transurethral resection of the prostate with spinal anaesthesia: a dose-response study by age group

Background

Dexmedetomidine (DMT), a highly selective α2-adrenoceptor agonist, has been used safely as a sedative in patients under regional anesthesia. The purpose of this study was to determine the 50% effective dose (ED₅₀) of single-dose DMT to induce adequate light sedation in elderly patients in comparison with younger patients undergoing transurethral resection of the prostate (TURP) with spinal anesthesia.

Methods

Forty-two male patients were recruited. The young age group (Group Y) included patients 45 to 64 years old and the old age group (Group O) included patients 65 to 78 years old. After the spinal anesthesia was performed, a pre-calculated dose of DMT was administered for 10 min. The Observer’s Assessment of Alertness/Sedation (OAA/S) scale, bispectral index score (BIS) were assessed then at 2-min intervals for 20 min. A modified Dixon’s up-and-down method was used to determine the ED₅₀ of the drug for light sedation (OAA/S score 3/4). In the recovery room, regression times of the motor and sensory blocks were recorded.

Results

The ED₅₀ of DMT was 0.25 (95% C.I. 0.15-0.35) μg/kg in Group O and 0.35 (95% C.I. 0.35-0.45) μg/kg in Group Y (p = 0.002). The ED₉₅ was 33% lower in Group O compare with Group Y (0.38 (95% C.I. 0.29-0.39) μg/kg vs. 0.57 (95% C.I. 0.49-0.59) μg/kg). The regression time of sensory block was longer in Group O than in Group Y (109.0 ± 40.2 min vs. 80.0 ± 31.6 min) (p = 0.014).

Conclusion

The single-dose of DMT for light sedation was lower by 21% in Group O compare with Group Y underwent TURP with spinal anesthesia.

Trial registration

ClinicalTrials.gov identifier: NCT01665586. Registered July 31, 2012.

The volume effect of lidocaine on thoracic epidural anesthesia in conscious Beagle dogs

OBJECTIVE

To evaluate the volume effect of local anesthetic solution on thoracic epidural analgesia in dogs.

STUDY DESIGN

Prospective, experimental trial.

ANIMALS

Five healthy adult Beagle dogs weighing 9.7 ± 1.3 kg.

METHODS

A catheter was inserted into the seventh thoracic epidural space using a lumbosacral approach, and secured with suture under total intravenous (IV) anesthesia with propofol. Each dog was administered four volume treatments (0.05, 0.10, 0.15 and 0.20 mL kg(-1)) of 2% lidocaine via the catheter at 12 hour intervals. In every treatment, dogs were re-anesthetized with propofol (6 mg kg(-1), IV) and isoflurane, and received iohexol at each volume to visualize the epidural distribution (ED) through computed tomography. Three hours after epidurography, when dogs had recovered from anesthesia, the appropriate volume of lidocaine was injected through the catheter, and sensory blockade (SB) in dermatomes was evaluated by pinching with a mosquito forceps. Results were presented as median (range), and the volume effect on ED and SB was analyzed with one-way Kruskal-Wallis anova.

RESULTS

In proportion to volumes (0.05, 0.10, 0.15 and 0.20 mL kg(-1)), there were significant increases in the extent of ED from 7.4 (5.5-9.0) to 10.4 (8.0-12.0), 13.2 (12.5-13.0), and 15.2 (13.0-18.0) vertebrae, respectively, p < 0.001, and in SB from 2.7 (1.0-5.0) to 6.8 (4.5-10.5), 9.9 (6.5-13.0), and 13.1 (11.0-15.0) dermatomes, respectively, p < 0.001. Unilateral ED and SB were observed in all treatments with various grades, and this distribution was more frequent in the low volume treatments. In the high volume treatments, temporary complications including Horner's syndrome, ataxia, paraplegia, depression, stupor, and intermittent cough occurred often.

CONCLUSIONS AND CLINICAL RELEVANCE

The increase in volume of local anesthetic solution improved SB by resulting in more consistent bilateral dermatome blockade as well as an extended blockade. However, caution should be exerted, as higher volume injections of lidocaine caused side effects in all dogs.

Comparison of subarachnoid block with bupivacaine and bupivacaine with fentanyl on entropy and sedation: A prospective randomized double-blind study

BACKGROUND AND AIMS

We studied the state entropy to monitor the sedative effect of subarachnoid block (SAB) using bupivacaine alone or combination of bupivacaine and fentanyl. The effect of use of fentanyl via the subarachnoid route on the sedation level was also studied using the entropy scores and the decrease in the requirement of propofol used as an adjuvant sedative drug.

MATERIALS AND METHODS

In this prospective randomized double-blind study, 30 patients of age 18-70 years requiring SAB were enrolled for the study. Patients with any known allergy to study drugs, contraindication for SAB, obesity, neurological or psychiatric disease on concurrent medication and refusal were excluded from the study. Patients were randomly allocated into two groups: Group C: SAB was administered with 2.5 mL (12.5 mg) of 0.5% hyperbaric bupivacaine; Group D: SAB was administered with 2.5 mL of 2 mL (10 mg) of 0.5% hyperbaric bupivacaine and 0.5 mL (25 μg) fentanyl. Propofol infusion was started if the state entropy (SE) value was ≥75, at the rate of 100 μg/kg/min till the SE value reaches in the range of 60-75 (recorded as onset time). Thereafter the infusion rate was titrated to maintain SE value between 60 and 75. The level of sedation was measured with SE and Ramsay sedation (RS) scale.

RESULTS

The demographic profile and baseline parameters, were comparable in two groups (P > 0.05). After SAB, decrease in SE and response entropy was noted in both the groups and fall was significant in Group D (P < 0.0001). The total propfol required in thew two groups were comparable being 3.97 ± 2.14 mg/kg in Group C and 3.41 ± 2.34 mg/kg in Group D (P = 0.342). The change in the mean RS values was from 1.17 ± 0.38 to 1.69 ± 0.47 in Group D (P = 0.06), whereas in Group C it was from 1.03 ± 0.18 to 1.43 ± 0.50 (P = 0.041) within 20 min of SAB.

CONCLUSION

Subarachnoid block causes sedation per se, but the level of sedation is not clinically significant and the sedation caused is not enough to avoid sedative agents for allaying anxiety in patients intraoperatively. The sedative effect of SAB was enhanced by adding intrathecal fentanyl probably because of better quality of SAB. SE showed good correlation with RS scaling system. Therefore, SE may be used as reliable tool to titrate sedation in patients undergoing surgery under SAB.

Effect of Dexmedetomidine IV on the Duration of Spinal Anesthesia with Prilocaine: A Double-Blind, Prospective Study in Adult Surgical Patients

BACKGROUND

The duration of spinal anesthesia with prilocaine has been poorly documented and no English-language study has been published regarding the effects of dexmedetomidine on the duration of anesthesia with spinal prilocaine.

OBJECTIVE

The aim of this study was to assess the effects of dexmedetomidine IV on the duration of action of prilocaine and its associated adverse events (AEs) in spinal anesthesia.

METHODS

In this double-blind, prospective study, patients classified as American Society of Anesthesiologists grade I to II who were to undergo lower abdominal, anorectal, or extremity surgery with a spinal anesthetic were assigned to 1 of 2 groups. All patients were administered prilocaine 2% for spinal anesthesia. Within 10 minutes after spinal anesthesia was initiated, group 1 received a loading dose of dexmedetomidine 1 μg/kg IV, followed by a maintenance dose of 0.4 μg/kg · h for 50 minutes; group 2 (control) received the same amount of physiologic saline in the same time frame. Mean arterial pressure (MAP), heart rate (HR), duration of sensory and motor blockade, and sedation scores were tracked. Patients were observed for 4.5 hours after surgery, with follow-ups occurring up to 96 hours after surgery.

RESULTS

Eighty-three patients were assessed for study inclusion, 23 of whom were excluded. Sixty patients (42 men, 18 women; mean [SD] age, 40.56 [16.86] years) were included in the study. MAP was similar in the 2 groups throughout the study. Mean (SD) HR was significantly lower in group 1 compared with group 2 at 20 minutes (70.43 [19.28] vs 77.63 [18.14] beats per minute, respectively; P = 0.02). The mean (SD) duration of the persistence of sensory anesthesia (ie, the time required for the maximal level of anesthesia to regress 2 dermatomes) was significantly longer in group 1 compared with group 2 (148.33 [21.18] vs 122.83 [18.73] minutes; P < 0.001). The mean (SD) time to complete abolishment of motor blockade was also significantly longer in group 1 than in group 2 (215.16 [25.10] vs 190.83 [18.57] minutes; P < 0.001). The average sedation score in group 1 was significantly higher than in group 2 (P < 0.001) during anesthesia. Significantly more patients in group 1 required atropine than those in group 2 (9 vs 2 patients; P < 0.001) to treat bradycardia. There was no significant between-group difference in the number of patients who received ephedrine to treat hypotension. One patient in each group reported waist and back pain; 2 patients in each group reported nausea. Shivering occurred in 0 and 5 patients in groups 1 and 2, respectively; the between-group difference in AEs was not statistically significant. Paresthesia, postdural puncture headache, allergic reactions, total spinal anesthesia, urinary retention, or vomiting-AEs commonly associated with spinal anesthesia-were not observed or reported by either group.

CONCLUSIONS

The results of this study suggest that dexmedetomidine IV significantly prolonged the duration of spinal anesthesia and provided a significantly higher level of sedation compared to placebo in this group of adult surgical patients. The treatment was generally well tolerated in all patients.

Anesthetic requirements and stress hormone responses in chronic spinal cord-injured patients undergoing surgery below the level of injury: nitrous oxide vs remifentanil

BACKGROUND

Nitrous oxide (N2O) and remifentanil both have anesthetic-reducing and antinociceptive effects. We aimed to determine the anesthetic requirements and stress hormone responses in spinal cord-injured (SCI) patients undergoing surgery under sevoflurane anesthesia with or without pharmacodynamically equivalent doses of N2O or remifentanil.

METHODS

Forty-five chronic, complete SCI patients undergoing surgery below the level of injury were randomly allocated to receive sevoflurane alone (control, n = 15), or in combination with 67% N2O (n = 15) or target-controlled infusion of 1.37 ng/ml remifentanil (n = 15). Sevoflurane concentrations were titrated to maintain a Bispectral Index (BIS) value between 40 and 50. Measurements included end-tidal sevoflurane concentrations, mean arterial blood pressure (MAP), heart rate (HR), and plasma catecholamine and cortisol concentrations.

RESULTS

During surgery, MAP, HR, and BIS did not differ among the groups. Sevoflurane concentrations were lower in the N2O group (0.94 ± 0.30%) and the remifentanil group (1.06 ± 0.29%) than in the control group (1.55 ± 0.34%) (P < 0.001, both). Plasma concentrations of norepinephrine remained unchanged compared to baseline values in each group, with no significant differences among groups throughout the study. Cortisol levels decreased during surgery as compared to baseline values, and returned to levels higher than baseline at 1 h after surgery (P < 0.05) without inter-group differences.

CONCLUSIONS

Remifentanil (1.37 ng/ml) and N2O (67%) reduced the sevoflurane requirements similarly by 31-39%, with no significant differences in hemodynamic and neuroendocrine responses. Either remifentanil or N2O can be used as an anesthetic adjuvant during sevoflurane anesthesia in SCI patients undergoing surgery below the level of injury.

Optimal dose of dexmedetomidine for sedation during spinal anesthesia

Background

Sedation in spinal anesthesia can reduce patient's anxiety and discomfort. Dexmedetomidine has a sedative, hypnotic, analgesic, and minimal respiratory depression effect. However, use of the dexmedetomidine is associated with prolonged recovery. This study was designed to investigate the optimal dose of intravenous dexmedetomidine for proper sedation with minimal recovery time in spinal anesthesia.

Methods

One hundred twenty eight patients, aged 20-70 years (58.8 ± 0.7), were recruited. After performing the spinal anesthesia with hyperbaric bupivacaine (13 mg), a loading dose of dexmedetomidine (1 µg/kg) was administered for 10 min, followed by the maintenance infusion of the following: Group A (n = 33; normal saline), Group B (n = 35; dexmedetomidine 0.2 µg/kg/hr), and Group C (n = 39; dexmedetomidine 0.4 µg/kg/hr). Heart rate, blood pressure, and the bispectral index score (BIS) were recorded during the operation. In the recovery room, modified aldrete score (MAS) was measured.

Results

There were no significant differences in mean blood pressure and heart rate among the three groups. BIS was not significantly different among the three groups from baseline to 60 min after the infusion of dexmedetomidine. BIS were significantly increased in Group A after 70 and 80 min, and Group A and B after 90, 100, 110 min of dexmedetomidine infusion (P < 0.05). MAS was higher in Group A as compared to Group B and C, within 30 min after admission in the recovery room (P < 0.05).

Conclusions

The loading dose (1 µg/kg/10 min) of dexmedetomidine was sufficient for surgery of less than 60 min. Dexmedetomidine infusion followed by maintenance dose (0.2 µg/kg/hr) was sufficient for surgery within 90 min.

Association between bispectral index and age and use of sedative drugs in high spinal anaesthesia

OBJECTIVES

A prospective, randomized, double-blind study using bispectral index values to objectively quantify the sedative effect of high spinal anaesthesia in patients stratified according to age, and to determine whether sedative drugs are associated with additional adverse respiratory and haemodynamic effects in older patients.

METHODS

Patients who were electively scheduled for lower limb or abdominal surgery were recruited and allocated into one of three groups according to their age and whether midazolam and fentanyl were used: younger (20-40 years); and older (61-80 years) with or without midazolam and fentanyl intravenous infusion.

RESULTS

The study recruited a total of 90 patients (n = 30 per group). Intraoperative bispectral index values were significantly lower than preoperative values in all groups. Patients in the older age group had significantly lower intraoperative bispectral index values than younger patients. Older patients were significantly more likely to experience respiratory depression (arterial oxyhaemoglobin saturation <90%) than younger patients.

CONCLUSIONS

The sedative effect of high spinal anaesthesia is greater in older patients than in younger patients, with an increase in respiratory instability.

Effects of intravenous dexmedetomidine on low-dose bupivacaine spinal anaesthesia in elderly patients

BACKGROUND

Dexmedetomidine (DMT) has been shown to prolong spinal anaesthesia. We evaluated the effects of intravenous DMT on low-dose bupivacaine spinal anaesthesia in elderly patients.

METHODS

Fifty-one elderly patients undergoing transurethral resection of the prostate were randomized into two groups receiving either 1.0 μg/kg DMT (DMT group, n = 26) or normal saline (control group n = 25) intravenously prior to spinal anaesthesia with 1.2 ml of bupivacaine, 5 mg/ml.

RESULTS

The mean time to two-segment regression (39 min vs. 78 min for cold, 41 min vs. 61 min for pinprick) and that to motor regression (23 min vs. 46 min) were longer in the DMT group than in the control group. The atropine-requiring bradycardia was more frequent in the DMT group than in the control group (24.0% vs. 3.8%). The median sedation scores (ranges) during surgery were 4 (2-6) in the DMT group and 2 (1-3) in the control group (P < 0.001). Two patients in the DMT group showed oxygen desaturation (peripheral oxygen saturation < 90%) during surgery. The duration of post-operative care unit stay was longer in the DMT group than in the control group (58 min vs. 96 min). Post-operative pain intensity was lower and the mean time to first request for post-operative analgesia was longer in the DMT group compared to the control group (6.6 h vs. 2.1 h).

CONCLUSION

Intravenous DMT prolonged the duration of spinal anaesthesia and improved post-operative analgesia. However, more profound sedation with desaturation was observed with more frequent bradycardia, and delayed recovery should be considered in elderly patients.

A prospective randomized study of intraoperative thoracic epidural analgesia in off-pump coronary artery bypass surgery

OBJECTIVE

The purpose of this study was to test the hypothesis that general anesthesia (GA) plus thoracic epidural anesthesia (TEA) has no impact on the outcomes of off-pump coronary artery bypass surgery (OPCABs) compared to GA followed by patient-controlled TEA (PCTEA), while GA plus TEA leads to a higher requirement for vasoactive drug use.

METHODS

Sixty-four patients, American Society of Anesthesiologists physical status II and III, who were scheduled for elective OPCABs, were offered an epidural catheter inserted at the T2-3 interspace and then randomized into 1 of 2 groups according to whether TEA was applied intraoperatively. The TEA(perio) group received GA plus TEA, while the TEA(post) group received GA alone. All groups had postoperative PCTEA. The number of requirements for vasoactive drugs and the extubation times were recorded. The analgesic effect was monitored by visual analog scale (VAS) pain scores. Heart rate, blood pressure, and blood gases were also monitored. The data are presented as mean values ± standard deviation, or medians with quartiles.

RESULTS

The proportion of vasoactive drug use was significantly higher in the TEA(perio) group intraoperatively (before or during completion of anastomoses: 59.4 vs. 20.7%, p = 0.004; after completion of anastomoses: 53.1 vs. 17.2%, p = 0.007). There was no statistically significant difference in extubation times or VAS scores between the 2 groups.

CONCLUSIONS

We conclude that GA plus TEA has no impact on the outcomes of OPCABs, while its use leads to a higher requirement for vasoactive drug use. GA followed by PCTEA facilitates the anesthesia administration, while it does not affect the extubation time and the postoperative analgesic effect.

Target-controlled infusion of remifentanil for conscious sedation during spinal anesthesia

Background

The aim of this study was to define the optimal target concentration of remifentanil which effectively achieves conscious sedation without significant vital sign changes and side effects during spinal anesthesia.

Methods

Sixty patients underwent spinal anesthesia with 0.5% hyperbaric bupivacaine (8-16 mg), and were infused with a target controlled infusion (TCI) of remifentanil at 1.0 ng/ml (group R10, n = 15), 2.0 ng/ml (group R20, n = 15), 3.0 ng/ml (group R30, n = 15), and 3.5 ng/ml (group R35, n = 15). Observer's assessment of alertness/sedation (OAA/S) scale, the bispectral index (BIS), anxiety levels and infusion rate of remifentanil were monitored during the operation.

Results

OAA/S scale was significantly lower in groups R30 (3.96) and R35 (3.34) than groups R10 (4.31) and R20 (4.26). Incidence of intraoperative respiratory depression events, post operative nausea and vomiting were significantly higher in group R35 than the other groups. There were no significant differences in BIS, anxiety level and incidences of recall of the operative procedure among the groups.

Conclusions

We conclude that the TCI of remifentanil at 3.0 ng/ml produces an effective sedation and anti-anxiety effects without significant side effects during spinal anesthesia.

The effect-site concentration of propofol producing respiratory depression during spinal anesthesia

BACKGROUND

Propofol is used worldwide for its sedative effective; nonetheless, has the serious side effect of respiratory depression. An increased blood concentration of propofol is well known to be associated with increased respiratory depression. However, there are no studies of the effect site concentration inducing respiratory depression. The purpose of this study was to determine the effect site concentration inducing respiratory depression of propofol when sedating a patient after spinal anesthesia.

METHODS

This study included thirty seven males who received operations with spinal anesthesia, which was performed on L3-4 and L4-5. All patients were monitored with the bispectral index and were continuously infused with propofol using target controlled infusion. Respiratory depression was diagnosed when one of the following was evident without upper respiratory obstructive signs: a greater than 20% increase of end tidal carbon dioxide from baseline pressure or pulse oximetry oxygen saturation lower than 95%. We obtained the EC(5), EC(10), and EC(50) of the effect site propofol for respiratory depression.

RESULTS

The EC(5) of propofol for respiratory depression was 3.09 mcg/ml (95% CI, 2.60-3.58). The EC(10) of propofol for respiratory depression was 3.18 mcg/ml (95% CI, 2.57-3.80). The EC(50) of propofol for respiratory depression was 3.99 mcg/ml (95% CI, 2.36-5.61).

CONCLUSIONS

The EC(5), EC(10), and EC(50) of effect site propofol for respiratory depression during spinal anesthesia were 3.09 mcg/ml ,3.18 mcg/ml, and 3.99 mcg/ml, respectively.

General anesthesia occurs frequently in elderly patients during propofol-based sedation and spinal anesthesia

STUDY OBJECTIVE

To test the hypothesis that sedation in elderly patients is often electrophysiologically equivalent to general anesthesia (GA).

DESIGN

Prospective, observational study.

SETTING

Operating room of a university medical center.

PATIENTS

40 elderly patients (>or=65 yrs of age) undergoing hip fracture repair with spinal anesthesia and propofol-based sedation.

INTERVENTIONS

In the routine practice group (RP; n = 15), propofol sedation was administered per the usual routine of the anesthesiologist. In the targeted sedation group (TS; n = 25), sedation was titrated to an observer's assessment of alertness/sedation (OAA/S) score of 4 (ie, lethargic in response to name called) to 5 (ie, awake and alert).

MEASUREMENTS

Both patient groups underwent processed electroencephalographic monitoring using bispectral index (BIS) intraoperatively. BIS levels were compared between groups to determine amount of surgical time spent in GA (BIS <or= 60).

MAIN RESULTS

In the RP group, subjects spent 32.2% of surgical time at BIS levels consistent with GA. Although averaged BIS values during surgery increased from (mean +/- SD) 71 +/- 16 to 88 +/- 9 (P < 0.001), GA was still observed during 5% of surgical time in the TS group. Overall, 13 of 15 (87%) RP group patients and 11 of 25 (44%) TS group patients (P < 0.010) experienced some period of GA.

CONCLUSIONS

BIS levels consistent with GA occur frequently in elderly patients during propofol-based sedation for spinal anesthesia. Altering routine practice such that sedation is titrated to a targeted clinically-determined sedation level reduces - but does not eliminate - this incidence.

Effect of epidural neuraxial blockade-dependent sedation on the Ramsay Sedation Scale and the composite auditory evoked potentials index in surgical intensive care patients

BACKGROUND/PURPOSE

Peripheral deafferentation induced by neuraxial anesthesia reduces the degree of cortical arousal. This study investigated whether epidural analgesia blockade decreased sedation, as measured by the rapidly extracted auditory evoked potentials index, A-line autoregressive index (AAI) and Ramsay Sedation Scale (RSS) in sedated surgical intensive care patients, and looked at whether this was a concentration-dependent effect of lidocaine.

METHODS

Forty patients underwent major lower abdominal surgery and received epidural analgesia in the surgical intensive care unit. Patients were continuously sedated with propofol to achieve an RSS value of 3, randomly divided into two groups, and received epidural analgesia with 10 mL of 0.5% or 1% lidocaine. Sedation was evaluated using the RSS and AAI, and analgesia was evaluated using a visual analog scale (VAS). RSS, AAI, electromyography (EMG) activity of AAI and VAS values were recorded at 5 minutes before and 30, 60 and 90 minutes after epidural lidocaine administration.

RESULTS

Epidural 0.5% lidocaine produced a reduction of AAI, EMG and VAS at 30, 60 and 90 minutes after administration. For 1% epidural lidocaine administration, AAI, EMG and VAS were also reduced at 30, 60 and 90 minutes after epidural lidocaine administration. However, there was no difference in the AAI between the two concentrations; moreover, no significant change was observed in the RSS.

CONCLUSION

Epidural lidocaine analgesia could potentiate sedation in patients evaluated by the AAI, but had no effect on the RSS. The present study suggests that the AAI could provide an objective and more precise index than the RSS in evaluation of sedation level in patients who are undergoing epidural pain management in the intensive care unit.

The effects of intravenous dexmedetomidine on spinal hyperbaric ropivacaine anesthesia

PURPOSE

In this study we investigated the effects of intravenously administered dexmedetomidine on the duration of hyperbaric ropivacaine in spinal anesthesia, and the side effects.

METHODS

In a prospective, double-blind study, sixty ASA I-II patients were randomized to two groups of 30 individuals. All patients were administered hyperbaric ropivacaine (22.5 mg) for spinal anesthesia. Intravenous dexmedetomidine was administered in group I for 60 min, physiological saline at the same amount and duration was infused in group II.

RESULTS

Measurements of mean blood pressure before and after the procedure revealed significant decreases in group I compared with group II after 20, 25, and 30 min. The times for two dermatomes regression of the blockade and complete resolution of motor blockade were significantly prolonged in group I. The sedation score in the dexmedetomidine group was significantly increased compared with controls. Atropine requirement was found to be significantly higher in group I than in group II.

CONCLUSION

Our results show that intravenously administered dexmedetomidine prolonged the duration of spinal anesthesia, provided sufficient sedation, and had few side effects. Therefore, dexmedetomidine is appropriate during spinal anesthesia, if the anesthesiologist is alert for development of bradycardia.

Neostigmine decreases bupivacaine use by patient-controlled epidural analgesia during labor: a randomized controlled study

BACKGROUND

Intrathecal neostigmine not only produces analgesia but also severe nausea. In contrast, epidural neostigmine enhances opioid and local anesthetic analgesia without causing nausea. Previous studies examined only single epidural neostigmine bolus administration and did not assess the efficacy of continuous epidural infusion or several aspects of maternal and fetal safety. We therefore tested the hypothesis that epidural neostigmine in combination with bupivacaine by continuous infusion during labor would reduce the amount of bupivacaine required.

METHODS

Twelve healthy women scheduled for elective cesarean delivery were assigned to receive epidural neostigmine, 40 microg (first six subjects) or 80 microg (second six subjects) as a single bolus, with fetal heart rate (FHR) and uterine contractions monitored for 20 min. In a subsequent experiment, 40 healthy laboring women were randomized to receive bupivacaine 1.25 mg/mL alone or with neostigmine 4 microg/mL by patient-controlled epidural analgesia. The primary outcome measure was hourly bupivacaine use.

RESULTS

Epidural neostigmine bolus did not alter baseline FHR, induce contractions, or produce nausea. Epidural neostigmine infusion reduced bupivacaine requirement by 19% in all patients and 25% in those with >4 h of treatment (P < 0.05 for both) but might have contributed to the incidence of mild sedation. Mode of delivery, incidence of maternal nausea, and FHR abnormality were similar between groups.

CONCLUSIONS

These data show that adding epidural neostigmine 4 microg/mL reduces the hourly bupivacaine requirement by 19%-25% with patient-controlled epidural analgesia during labor. Administered as a bolus and by continuous infusion at the studied doses, epidural neostigmine does not cause nausea and does not induce uterine contractions or FHR abnormalities, but mild sedation can occur.

Sympathovagal effects of spinal anaesthesia with intrathecal or intravenous fentanyl assessed by heart rate variability

BACKGROUND

Although many investigators previously reported the sympathovagal effect of spinal anaesthesia, there is no information about the sympathovagal effects of supplementation with fentanyl. The aim of this study was to evaluate the sympathovagal effects of intrathecal or intravenous fentanyl added to spinal anaesthesia.

METHODS

One hundred and twenty patients undergoing elective transurethral surgery under spinal anaesthesia were randomly allocated to receive intrathecally either isobaric bupivacaine alone (Group B), bupivacaine supplemented with intrathecal (Group Ft) or with intravenous fentanyl (Group Fv). Heart rate variability was estimated using the MemCalc method (Tarawa, Suwa Trust, Japan) before and after spinal anaesthesia.

RESULTS

In all groups, spinal anaesthesia significantly decreased low frequency/high frequency (LF/HF) as a marker of sympathovagal balance. However, patients in Group B with a low block height developed a marked increase in LF/HF after spinal anaesthesia, which was attenuated in Group Ft. Meanwhile, intravenous fentanyl did not attenuate this response.

CONCLUSION

We conclude that sympathetic activation observed in patients with a low block height was attenuated by intrathecal fentanyl but not by intravenous fentanyl.