Effects of intramuscular administration of lidocaine or bupivacaine on induction and maintenance doses of propofol evaluated by bispectral index

Multiple intramuscular ropivacaine injections to donor sites reduces pain in deep inferior epigastric artery perforator flap breast reconstruction

INTRODUCTION

Local anesthetic infiltration at the surgical site has been studied in various surgical disciplines; however, its impact on deep inferior epigastric artery perforator (DIEP) flap breast reconstruction has not been previously assessed. This study aimed to evaluate the effects of multiple intramuscular ropivacaine injections on donor site pain during DIEP flap breast reconstruction.

METHODS

The study included 65 patients who received local ropivacaine injections during DIEP reconstructions between March 2022 and February 2023, compared to 55 patients who underwent surgeries without ropivacaine from October 2018 to July 2020. A total of 20 cc of 0.75% ropivacaine solution was evenly administered at 20 sites along the abdominal wall muscles. The effect of intramuscular ropivacaine injection on postoperative visual analog scale (VAS) was evaluated using linear mixed-effect model. Opioid consumption and hospital days were also compared.

RESULTS

The daily median VAS score was lower in the ropivacaine group (all p-values < 0.001). When analyzed using a linear mixed-effects model, those who received ropivacaine had significantly lower VAS scores over the first 5 days postoperatively (p-value < 0.001). The rate of VAS score decline was also faster in the ropivacaine group over the first 24 h postoperative (p-value = 0.045). Although opioid consumption was comparable between the groups, those receiving ropivacaine had significantly shorter hospital stay (p-value = 0.001) and no complications related to the injections were observed.

CONCLUSION

Multiple intramuscular injections of ropivacaine to the donor site may reduce postoperative pain and shorten hospital stays, without increasing opioid consumption.

Total intravenous anesthesia management with simultaneous use of remimazolam and propofol: A case series of three patients

Remimazolam is an ultra-short-acting benzodiazepine anesthetic agent. Because of pharmacodynamic interactions in the sedation effect between benzodiazepines and propofol, the combination of remimazolam and propofol may allow for a dose reduction of each agent while providing effective sedation for general anesthesia. We experienced three cases in which general anesthesia was induced with remimazolam and maintained with relatively small doses of remimazolam and propofol target-controlled infusion. In all cases, electroencephalogram changes associated with sedation induced by remimazolam were carefully observed during anesthesia induction before administration of propofol. The time required for recovery from anesthesia was 8-13 min. This is the first report in which remimazolam and propofol were concomitantly used for general anesthesia based on the concept of pharmacodynamic interaction. This anesthetic combination may be beneficial in reducing doses of each anesthetic and avoiding delayed recovery from anesthesia, although further study is needed to confirm this.

A Potential Mechanism of Sodium Channel Mediating the General Anesthesia Induced by Propofol

General anesthesia has revolutionized healthcare over the past 200 years and continues to show advancements. However, many phenomena induced by general anesthetics including paradoxical excitation are still poorly understood. Voltage-gated sodium channels (Na_V) were believed to be one of the proteins targeted during general anesthesia. Based on electrophysiological measurements before and after propofol treatments of different concentrations, we mathematically modified the Hodgkin–Huxley sodium channel formulations and constructed a thalamocortical model to investigate the potential roles of Na_V. The ion channels of individual neurons were modeled using the Hodgkin–Huxley type equations. The enhancement of propofol-induced GABAa current was simulated by increasing the maximal conductance and the time-constant of decay. Electroencephalogram (EEG) was evaluated as the post-synaptic potential from pyramidal (PY) cells. We found that a left shift in activation of Na_V was induced primarily by a low concentration of propofol (0.3–10 μM), while a left shift in inactivation of Na_V was induced by an increasing concentration (0.3–30 μM). Mathematical simulation indicated that a left shift of Na_V activation produced a Hopf bifurcation, leading to cell oscillations. Left shift of Na_V activation around a value of 5.5 mV in the thalamocortical models suppressed normal bursting of thalamocortical (TC) cells by triggering its chaotic oscillations. This led to irregular spiking of PY cells and an increased frequency in EEG readings. This observation suggests a mechanism leading to paradoxical excitation during general anesthesia. While a left shift in inactivation led to light hyperpolarization in individual cells, it inhibited the activity of the thalamocortical model after a certain depth of anesthesia. This finding implies that high doses of propofol inhibit the network partly by accelerating Na_V toward inactivation. Additionally, this result explains why the application of sodium channel blockers decreases the requirement for general anesthetics. Our study provides an insight into the roles that Na_V plays in the mechanism of general anesthesia. Since the activation and inactivation of Na_V are structurally independent, it should be possible to avoid side effects by state-dependent binding to the Na_V to achieve precision medicine in the future.

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.

Evaluation of the sedative and physiological effects of intramuscular lidocaine in bearded dragons (Pogona vitticeps) sedated with alfaxalone

OBJECTIVE

To evaluate if intramuscular (IM) lidocaine potentiates the sedative effects of alfaxalone and results in cardiopulmonary changes in sedated bearded dragons.

STUDY DESIGN

Prospective experimental crossover study.

ANIMALS

A group of eight adult bearded dragons (Pogona vitticeps) weighing 334 ± 46 g.

METHODS

Animals were administered alfaxalone (10 mg kg^-1 subcutaneously) and 15 minutes later either lidocaine 2% (4 mg kg^-1) or 0.9% sodium chloride (0.2 mL kg^-1) was administered IM in the thoracic limb. The treatments were randomized and separated by 7 days. Sedation was scored based on body position, eye closure, jaw tone, swallowing, pick up response, righting reflex and pelvic limb withdrawal reflex. Heart rate (HR) and respiratory rate (f_R) were recorded every 5 minutes until recovery from sedation.

RESULTS

Lidocaine had no significant effect on duration or depth of alfaxalone sedation. HR increased significantly for <10 minutes following lidocaine administration by a median (interquartile range) of 33% (28-37%; p = 0.024). No clinically significant effects on f_R occurred following lidocaine injection.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of lidocaine 2% (4 mg kg^-1) IM did not potentiate alfaxalone sedation but resulted in a transient clinically relevant increase in HR.

Effect of Nicardipine on Haemodynamic and Bispectral Index Changes following Endotracheal Intubation

We investigated the effect of IV nicardipine on haemodynamic and bispectral index responses to the induction of general anaesthesia and intubation. Forty patients were randomly allocated to two groups of 20 to receive normal saline or nicardipine 15 μg/kg IV 30 s after induction. Ninety seconds later, tracheal intubation was performed. Systolic blood pressure, heart rate and bispectral index were measured at baseline, 1 min after induction, pre-intubation, and every minute until 5 min after endotracheal intubation. Rate–pressure product values were calculated. In the nicardipine group, systolic blood pressure decreased compared with the control group, and heart rate increased compared with the control group. Bispectral index and rate–pressure product showed no differences between the two groups. In conclusion, the administration of 15 μg/kg nicardipine IV does not affect anaesthetic depth in response to the induction of general anaesthesia and intubation.

Clinical effects of midazolam or lidocaine co-induction with a propofol target-controlled infusion (TCI) in dogs

OBJECTIVE

To evaluate the propofol requirement, cardiovascular and respiratory variables using midazolam or lidocaine with a propofol target-controlled infusion (PTCI) for induction of anaesthesia in healthy dogs.

STUDY DESIGN

Prospective, randomized, controlled blinded clinical trial.

ANIMALS

Sixty client-owned dogs [American Society of Anesthesiologists (ASA) I-II] undergoing surgical procedures.

METHODS

Thirty minutes after premedication with acepromazine (0.03 mg kg(-1) ) and morphine (0.2 mg kg(-1) ), PTCI was started and maintained at a plasma target concentration of 1 μg mL(-1) . Three minutes later, dogs (n = 20 per group) received either 5 mL 0.9% sodium chloride (SG), 2 mg kg(-1) of lidocaine (LG) or 0.2 mg kg(-1) of midazolam (MG) intravenously (IV) as a co-induction agent. Two minutes later, suitability for endotracheal intubation was assessed. If intubation was not possible, the propofol target was increased by 0.5 μg mL(-1) every 60 seconds until it was successfully achieved. Heart rate (HR), respiratory rate (fR ), and oscillometric systolic arterial pressure (SAP), mean arterial pressure (MAP) and diastolic arterial pressure (DAP) were recorded immediately prior to commencing PTCI (B0), prior to intubation (BI), immediately after (T0), and at 3 (T3) and 5 (T5) minutes post-intubation. End-tidal partial pressures of carbon dioxide (PE(') CO2 ) were recorded at T0, T3 and T5. The occurrence of excitement at any time point was noted.

RESULTS

The median (range) propofol target concentration for endotracheal intubation was significantly lower in MG, 1.5 (1.0-4.0) μg mL(-1) compared with LG, 2.5 (1.5-4.5) μg mL(-1) or SG, 3.0 (2.0-5.0) μg mL(-1) . Heart rate, MAP, fR and PE(') CO2 were similar in the three groups at all time points. No excitement was reported in any dog.

CONCLUSIONS AND CLINICAL RELEVANCE

Midazolam, but not lidocaine, provided a significant reduction in PTCI requirement for induction of anaesthesia thereby allowing successful intubation. However, cardiovascular and respiratory effects were not different between the groups.

The thermodynamics of general and local anesthesia

General anesthetics are known to cause depression of the freezing point of transitions in biomembranes. This is a consequence of ideal mixing of the anesthetic drugs in the membrane fluid phase and exclusion from the solid phase. Such a generic law provides physical justification of the famous Meyer-Overton rule. We show here that general anesthetics, barbiturates, and local anesthetics all display the same effect on melting transitions. Their effect is reversed by hydrostatic pressure. Thus, the thermodynamic behavior of local anesthetics is very similar to that of general anesthetics. We present a detailed thermodynamic analysis of heat capacity profiles of membranes in the presence of anesthetics. Using this analysis, we are able to describe experimentally observed calorimetric profiles and predict the anesthetic features of arbitrary molecules. In addition, we discuss the thermodynamic origin of the cutoff effect of long-chain alcohols and the additivity of the effect of general and local anesthetics.

Effect of transversus abdominis plane block on cost of laparoscopic cholecystectomy anesthesia

Background

Use of transversus abdominis plane (TAP) block for postoperative analgesia is continuously increasing. However, few studies have investigated intraoperative effects of TAP block. We aimed to study the effects of TAP block in terms of cost-effectiveness and consumption of inhalation agents.

Material/Methods

Forty patients undergoing laparoscopic cholecystectomy were enrolled in this study. Patients were randomly divided into 2 groups: Group 1 (n=20) patients received TAP block and Group 2 (n=20) patients did not receive TAP block. Standard anesthesia induction was used in all patients. For the maintenance of anesthesia, fractional inspired oxygen (FIO2) of 50% in air with desflurane was used with a fresh gas flow of 4 L/min. All patients were monitored with electrocardiography and for peripheral oxygen saturation (SpO2), end-tidal carbon dioxide (ET), heart rate (HR), noninvasive mean blood pressure (MBP), and bispectral index (BIS). Bilateral TAP blocks were performed under ultrasound guidance to Group 1 patients. The BIS value was maintained at between 40 and 50 during the surgery. The Dion formula was used to calculate consumption of desflurane for each patient.

Results

There was no difference between the groups with respect to demographic characteristics of the patients. Duration of anesthesia, surgery time, and dosage of fentanyl were similar in the 2 groups. However, the cost and consumption of desflurane was significantly lower in Group 1.

Conclusions

Total anesthesia consumption was lower and the cost-effectiveness of anesthesia was better in TAP block patients with general anesthesia than in non-TAP block patients undergoing laparoscopic cholecystectomy.

Evaluation of the isoflurane-sparing effects of lidocaine infusion during umbilical surgery in calves

OBJECTIVE

To evaluate the isoflurane-sparing effects of lidocaine administered by constant rate infusion (CRI) during umbilical surgery in calves.

STUDY DESIGN

Randomized 'blinded' prospective clinical study.

ANIMALS

Thirty calves (mean 4.7 ± SD 2.5 weeks old) undergoing umbilical surgery.

METHODS

After premedication with xylazine (0.1 mg kg(-1) , IM), anaesthesia was induced with ketamine (4 mg kg(-1) , IV) and maintained with isoflurane in O(2) administered through a circle breathing system. The calves were assigned randomly to receive a bolus of 2 mg kg(-1) lidocaine IV after induction of anaesthesia, followed by CRI of 50 μg kg(-1) minute(-1) (group L, n=15) or a bolus and CRI of 0.9% sodium chloride (NaCl, group S, n=15). End-tidal isoflurane was adjusted to achieve adequate depth of anaesthesia. Heart rate, direct arterial blood pressure and body temperature were measured intraoperatively. Groups were compared by t- tests, anova or Mann-Whitney rank sum test as appropriate.

RESULTS

The end-tidal concentration of isoflurane (median, IQR) was significantly lower in group L [1.0% (0.94-1.1)] compared to group S [1.2% (1.1-1.5)], indicating a 16.7% reduction in anaesthetic requirement during lidocaine CRI. Cardiopulmonary parameters and recovery times did not differ significantly between groups.

CONCLUSION AND CLINICAL RELEVANCE

Lidocaine CRI may be used as a supplement to inhalation anaesthesia during umbilical surgery in calves in countries where such a protocol would be within the legal requirements for veterinary use in food animals. This study did not show any measurable benefit to the calves other than a reduction in isoflurane requirement.

Effect of caudal block on sevoflurane requirement for lower limb surgery in children with cerebral palsy

BACKGROUND

Caudal block is a widely used technique for providing perioperative pain management in children. In this randomized double-blinded study, we evaluated the effects of preoperative caudal block on sevoflurane requirements in children with cerebral palsy (CP) undergoing lower limb surgery while bispectral index (BIS) values were maintained between 45 and 55.

METHODS

52 children undergoing Achilles-tendon lengthening were randomized to receive combined general-caudal anesthesia (caudal group, n = 27) or general anesthesia alone (control group, n = 25). Caudal block was performed with a single dose of 0.7 ml·kg(-1) of 1.0% lidocaine containing epinephrine at 5 μg·ml(-1). The control group received no preoperative caudal block. The endtidal sevoflurane concentrations (ET(sev)) were adjusted every minute to maintain the BIS values between 45 and 55.

RESULTS

The ET(sev) required to maintain the BIS values were not significantly different between the control and caudal groups after induction of anesthesia [2.1 (0.2) vs 2.2 (0.4); P = 0.773]. However, significantly higher ET(sev) was observed in the control group before surgical incision [2.0 (0.2) vs 1.8 (0.3); P = 0.013] and during the first 20 min after surgical incision [2.2 (0.3) vs 1.4 (0.3); P < 0.001]. There was no significant difference in BIS values between the control and caudal groups throughout the study period (P > 0.05). In the caudal group, the caudal block was successful in 25 of 27 (92.6%) patients.

CONCLUSIONS

Caudal block effectively reduced sevoflurane requirements by 36% compared to general anesthesia alone in children with CP undergoing lower limb surgery while BIS values were maintained between 45 and 55.

Local anesthetic inhibits hyperpolarization-activated cationic currents

Systemic administration of local anesthetics has beneficial perioperative properties and an anesthetic-sparing and antiarrhythmic effect, although the detailed mechanisms of these actions remain unclear. In the present study, we investigated the effects of a local anesthetic, lidocaine, on hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels that contribute to the pacemaker currents in rhythmically oscillating cells of the heart and brain. Voltage-clamp recordings were used to examine the properties of cloned HCN subunit currents expressed in Xenopus laevis oocytes and human embryonic kidney (HEK) 293 cells under control condition and lidocaine administration. Lidocaine inhibited HCN1, HCN2, HCN1-HCN2, and HCN4 channel currents at 100 μM in both oocytes and/or HEK 293 cells; it caused a decrease in both tonic and maximal current (∼30-50% inhibition) and slowed current activation kinetics for all subunits. In addition, lidocaine evoked a hyperpolarizing shift in half-activation voltage (ΔV(1/2) of ∼-10 to -14 mV), but only for HCN1 and HCN1-HCN2 channels. By fitting concentration-response data to logistic functions, we estimated half-maximal (EC(50)) concentrations of lidocaine of ∼30 to 40 μM for the shift in V(1/2) observed with HCN1 and HCN1-HCN2; for inhibition of current amplitude, calculated EC(50) values were ∼50 to 70 μM for HCN1, HCN2, and HCN1-HCN2 channels. A lidocaine metabolite, monoethylglycinexylidide (100 μM), had similar inhibitory actions on HCN channels. These results indicate that lidocaine potently inhibits HCN channel subunits in dose-dependent manner over a concentration range relevant for systemic application. The ability of local anesthetics to modulate I(h) in central neurons may contribute to central nervous system depression, whereas effects on I(f) in cardiac pacemaker cells may contribute to the antiarrhythmic and/or cardiovascular toxic action.

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.

Lidocaine infusion as a rescue analgesic in the perioperative setting

In the present case series, three patients for whom regional anesthesia may have been the optimum technique for controlling postoperative pain are discussed. However, due to prevailing circumstances, regional anesthesia could not be provided. An intravenous infusion of lidocaine at 4 mg/min was administered perioperatively as an alternative 'rescue' analgesic technique. This infusion rate, based on previous extensive pharmacokinetic studies, is widely considered to be safe. Postoperative pain was lower than expected for the type of surgery. Anecdotal experience suggests that hospital length of stay may also be reduced, with both patient and economic benefits.

Comparison of 1.5% lidocaine and 0.5% ropivacaine epidural anesthesia combined with propofol general anesthesia guided by bispectral index

OBJECTIVE

To compare the effects of epidural anesthesia with 1.5% lidocaine and 0.5% ropivacaine on propofol requirements, the time to loss of consciousness (LOC), effect-site propofol concentrations, and the hemodynamic variables during induction of general anesthesia guided by bispectral index (BIS) were studied.

METHODS

Forty-five patients were divided into three groups to receive epidurally administered saline (Group S), 1.5% (w/w) lidocaine (Group L), or 0.5% (w/w) ropivacaine (Group R). Propofol infusion was started to produce blood concentration of 4 mug/ml. Once the BIS value reached 40~50, endotracheal intubation was facilitated by 0.1 mg/kg vecuronium. Measurements included the time to LOC, effect-site propofol concentrations, total propofol dose, mean arterial blood pressure (MABP), and heart rate (HR) at different study time points.

RESULTS

During induction of anesthesia, both Groups L and R were similar for the time to LOC, effect-site propofol concentrations, total propofol dose, MABP, HR, and BIS. The total doses of propofol administered until 1 min post-intubation were significantly less in patients of Groups R and L compared with Group S. MABP and HR were significantly lower following propofol induction compared with baseline values in the three groups, or MABP was significantly increased following intubation as compared with that prior to intubation in Group S but not in Groups R and L while HR was significantly increased following intubation in the three groups.

CONCLUSION

Epidural anesthesia with 1.5% lidocaine and 0.5% ropivacaine has similar effects on the time to LOC, effect-site propofol concentrations, total propofol dose, and the hemodynamic variables during induction of general anesthesia.

Effect of intravenous lidocaine and ketamine on the minimum alveolar concentration of isoflurane in goats

OBJECTIVE

To evaluate the effects of i.v. lidocaine (L) and ketamine (K), alone and in combination (LK), on the minimum alveolar concentration (MAC) of isoflurane (ISO) in goats.

STUDY DESIGN

Randomized crossover design.

ANIMALS

Eight, adult mixed breed castrated male goats, aged 1-2 years weighing 24-51 kg.

METHODS

Anesthesia was induced with ISO that was delivered via a mask. The tracheas were intubated and the animals ventilated to maintain an end-tidal carbon dioxide partial pressure between 25 and 30 mmHg (3.3-4 kPa). Baseline MAC (MAC(B)) that prevented purposeful movement in response to clamping a claw was determined in triplicate. After MAC(B) determination, each goat received one of the following treatments, which were administered as a loading (LD) dose followed by a constant rate infusion, IV: L (2.5 mg kg(-1); 100 microg kg(-1) minute(-1)), K (1.5 mg kg(-1); 50 microg kg(-1) minute(-1)), L and K combination or saline, and the MAC (MAC(T)) was re-determined in triplicate. Plasma concentrations of L and K were measured around each MAC point and the values averaged.

RESULTS

The least-squares mean MAC(B) for all treatments was 1.13 +/- 0.03%. L, K, and LK reduced (p < 0.05) MAC(B) by 18.3%, 49.6% and 69.4%, respectively. Plasma concentrations for L, K, and LK were 1617 +/- 385, 1535 +/- 251 and 1865 +/- 317/1467 +/- 185 ng mL(-1), respectively. No change (p > 0.05) occurred with saline.

CONCLUSION

Lidocaine and K caused significant decreases in the MAC of ISO. The combination (LK) had an additive effect. However, the plasma L concentrations were less than predicted, as was the MAC reduction with L.

CLINICAL RELEVANCE

The use of L, K and the combination, at the doses studied, will allow a clinically important reduction in the concentration of ISO required to maintain general anesthesia in goats.

The Effect of Too Much Intravenous Lidocaine on Bispectral Index

Systemic local anesthetics have beneficial perioperative properties and have an anesthetic-sparing effect. To assess depth of anesthesia during lidocaine infusion, it would be important to know the effect of systemic local anesthetics on bispectral index (BIS). However, this has not been investigated. We report an inadvertent overdose of i.v. lidocaine in a patient monitored with BIS. BIS decreased to 0 for approximately 15 min, indicating that lidocaine and sevoflurane interact to decrease BIS.

The effects of caudal local anesthesia blockade on the Bispectral Index during general anesthesia in children

BACKGROUND

Peripheral deafferentation induced by epidural or spinal anesthesia reduces the degree of cortical arousal in adults. This study aimed at determining if caudal blockade decreases the level of arousal, as measured by Bispectral Index (BIS) in unstimulated children, and to determine if this effect differed between age groups.

METHODS

Hospital ethics committee approval and parental consent was obtained. Children (age between 24 months and 5 years) and infants (between 6 and 24 months of age) were recruited if they were scheduled for below umbilical surgery that would usually require caudal local anesthesia blockade. Before the procedure, subjects within each age group were randomized to either caudal group (1 ml.kg(-1) 0.25% bupivacaine), or control group (no caudal). In all groups, anesthesia was induced with sevoflurane and maintained at a constant endtidal concentration of 1.5% sevoflurane without N(2)O. Five minutes after induction a baseline BIS was recorded (BIS(1)). In the caudal groups, a caudal block was then performed while in the control groups no block was performed. Fifteen minutes later, the BIS was again recorded (BIS(2)). The change in BIS over this time period was the primary outcome (BIS(Delta)). After measurement, subjects in the control groups received a caudal block before the start of surgery.

RESULTS

Twenty-nine infants and 18 children completed the study protocol. In children, BIS(Delta) was significantly different between the caudal group and control (-5.7 vs -0.7, P = 0.04). In infants, no significant difference was detected in BIS(Delta) between caudal and control groups.

CONCLUSIONS

Caudal blockade decreased the degree of arousal, as measured by BIS, in unstimulated children aged 2-5 years. No change in arousal was detected in infants.

BIS guided sedation with propofol during spinal anaesthesia: influence of anaesthetic level on sedation requirement

BACKGROUND

In this prospective, clinical study we tested the hypothesis whether two different doses of spinal administered bupivacaine and accordingly, two different levels of spinal anaesthesia can affect the dose requirement of propofol during BIS guided sedation.

METHODS

Fifty women undergoing vaginal hysterectomy (high spinal group, HS) or transvaginal tape (TVT) procedure for urinary incontinence (low spinal group, LS) under spinal anaesthesia were enrolled to the study. In group HS, 17.5 mg and in group LS, 7.5 mg of hyperbaric bupivacaine were given intrathecally. After 15 min to obtain the appropriate level of spinal anaesthesia, propofol infusion was started at a rate of 100 microg kg(-1) min(-1) to reach a BIS level of less than 75 (onset time), and titrated to maintain the BIS value between 65 and 75. Propofol infusion was stopped 45 min after placing the spinal to measure the time to reach a BIS level of 90 (recovery time).

RESULTS

Median anaesthetic level was T3 (T1-4) in the HS group and T10 (T9-11) in the LS group. In both the HS and the LS groups, onset time was 226 (47) vs 273 (48) s (P=0.001), recovery time was 234 (47) vs 202 (56) s (P=0.03), total dose of propofol was 2.17 (0.43) vs 3.14 (0.56) mg kg(-1) (P<0.001), respectively.

CONCLUSION

A high spinal block obtained with hyperbaric bupivacaine 17.5 mg was associated with a faster onset, delayed recovery and lower doses of propofol sedation compared with a low spinal block with 7.5 mg of the same drug.

Lidocaine does not prevent bispectral index increases in response to endotracheal intubation

We investigated the effect of IV lidocaine on the hemodynamic and bispectral index responses to induction of general anesthesia and endotracheal intubation. Forty patients (ASA I) were randomly allocated into 2 groups of 20 to receive normal saline or lidocaine 1.5 mg/kg IV 30 s after induction. Ninety seconds later, endotracheal intubation was performed. Systolic blood pressure, heart rate, and bispectral index were measured at baseline, 1 min after induction, at preintubation, and every minute until 5 min after endotracheal intubation. Bispectral index at 1 min after induction and preintubation in the lidocaine group were significantly lower compared with the control group (P < 0.05). Systolic blood pressure increased significantly at 1 and 2 min after intubation in the control group compared with the baseline value (P < 0.05) but did not increase significantly in the lidocaine group. Heart rate increased at 1 to 3 min in both groups (P < 0.05), but there was no significant difference between the two groups. One patient in the control group had recall of the procedure. We conclude that the administration of IV lidocaine (1.5 mg/kg) does not suppress the hypnotic response to endotracheal intubation.

The Effect of Epidural Bupivacaine on Induction and Maintenance Doses of Propofol (Evaluated by Bispectral Index) and Maintenance Doses of Fentanyl and Vecuronium

The growing interest in combining local and general anesthesia has led to studies investigating possible interactions between general anesthesia and local anesthetics administered via spinal, epidural, IV, or IM routes. However, no study has evaluated the effect of local anesthetics on all three components of balanced anesthesia, i.e., hypnosis, analgesia, and muscle relaxation. In this prospective, randomized, double-blind study, we investigated the effect of epidural bupivacaine on the dose requirement of propofol (as evaluated by using the bispectral index [BIS]), fentanyl, and vecuronium for general anesthesia. This study consisted of 30 adults, ASA physical status I and II, undergoing Whipple's pancreaticoduodenectomy for periampullary carcinoma lasting >4 h. An epidural catheter was placed between T9-10. Depending on the group allocation, 10 mL of the study drug was administered as a bolus followed by an infusion at 6 mL/h via the epidural catheter. Patients were divided into 2 groups of 15 each. Patients in the control group received epidural normal saline whereas those in the bupivacaine group received epidural bupivacaine 0.1%. Induction of anesthesia was performed with IV fentanyl 2 mug/kg and propofol titrated to achieve BIS between 40-50. Endotracheal intubation was facilitated by the IV administration of vecuronium 0.1 mg/kg and patient's lungs were ventilated with 66% nitrous oxide in oxygen. After intubation, infusion of propofol 1% was titrated to maintain BIS between 40-50. Inadequate analgesia was defined as an increase in systolic blood pressure and/or heart rate by >20% of baseline values in response to surgical stimulus and was treated with bolus fentanyl 0.5 mug/kg. Neuromuscular monitoring was used to assess the need for additional doses of vecuronium. Data were analyzed by using the Student's t-test and P </= 0.05 was considered significant. The requirement of propofol for induction and maintenance of anesthesia in the bupivacaine group was 1.3 +/- 0.3 mg/kg and 2.4 +/- 0.9 mg . kg(-1) . h(-1), respectively, compared with 2.4 +/- 0.6 mg/kg and 4.4 +/- 1.6 mg . kg(-1) . h(-1) observed in the control group (P < 0.05). Significant reduction was also observed in the requirement of vecuronium and fentanyl during maintenance in the bupivacaine group (P < 0.05). We conclude that epidural bupivacaine given before induction of anesthesia reduces the requirement of propofol, fentanyl, and vecuronium during general anesthesia.