Balanced Opioid-free Anesthesia with Dexmedetomidine versus Balanced Anesthesia with Remifentanil for Major or Intermediate Noncardiac Surgery.

BACKGROUND: It is speculated that opioid-free anesthesia may provide adequate pain control while reducing postoperative opioid consumption. However, there is currently no evidence to support the speculation. The authors hypothesized that opioid-free balanced anesthetic with dexmedetomidine reduces postoperative opioid-related adverse events compared with balanced anesthetic with remifentanil. METHODS: Patients were randomized to receive a standard balanced anesthetic with either intraoperative remifentanil plus morphine (remifentanil group) or dexmedetomidine (opioid-free group). All patients received intraoperative propofol, desflurane, dexamethasone, lidocaine infusion, ketamine infusion, neuromuscular blockade, and postoperative lidocaine infusion, paracetamol, nefopam, and patient-controlled morphine. The primary outcome was a composite of postoperative opioid-related adverse events (hypoxemia, ileus, or cognitive dysfunction) within the first 48 h after extubation. The main secondary outcomes were episodes of postoperative pain, opioid consumption, and postoperative nausea and vomiting. RESULTS: The study was stopped prematurely because of five cases of severe bradycardia in the dexmedetomidine group. The primary composite outcome occurred in 122 of 156 (78%) dexmedetomidine group patients compared with 105 of 156 (67%) in the remifentanil group (relative risk, 1.16; 95% CI, 1.01 to 1.33; P = 0.031). Hypoxemia occurred 110 of 152 (72%) of dexmedetomidine group and 94 of 155 (61%) of remifentanil group patients (relative risk, 1.19; 95% CI, 1.02 to 1.40; P = 0.030). There were no differences in ileus or cognitive dysfunction. Cumulative 0 to 48 h postoperative morphine consumption (11 mg [5 to 21] versus 6 mg [0 to 17]) and postoperative nausea and vomiting (58 of 157 [37%] versus 37 of 157 [24%]; relative risk, 0.64; 95% CI, 0.45 to 0.90) were both less in the dexmedetomidine group, whereas measures of analgesia were similar in both groups. Dexmedetomidine patients had more delayed extubation and prolonged postanesthesia care unit stay. CONCLUSIONS: This trial refuted the hypothesis that balanced opioid-free anesthesia with dexmedetomidine, compared with remifentanil, would result in fewer postoperative opioid-related adverse events. Conversely, it did result in a greater incidence of serious adverse events, especially hypoxemia and bradycardia.

Comparison between total intravenous anesthesia and balanced anesthesia on postoperative opioid consumption in patients who underwent laparoscopic-assisted distal gastrectomy.

Remifentanil is the most frequently prescribed opioid for total intravenous anesthesia (TIVA) or balanced anesthesia (BA), due to its favorable pharmacological properties. However, several studies have reported opioid-induced hyperalgesia and/or acute tolerance after intraoperatively using remifentanil. In addition, it is imperative to control postoperative pain with lower doses of opioid anesthetic agents. Therefore, we compared the amount of opioid consumption between TIVA with propofol-remifentanil and BA with desflurane-remifentanil, to control postoperative pain in patients who underwent laparoscopic-assisted distal gastrectomy (LADG) with gastroduodenostomy.We retrospectively evaluated demographic variables (age, gender, height, weight, and smoking habits), the duration of general anesthesia (GA), and intraoperatively administered remifentanil consumption through the electronic medical records of patients who underwent LADG with gastroduodenostomy due to early stomach cancer. The primary outcome was postoperative opioid consumption during postoperative day (POD) 2. The secondary outcomes were the incidence of any rescue opioid analgesics administered, numeric rating scale, and various adverse effects during POD 2. We categorized the data in 2 patient groups to compare TIVA with propofol-remifentanil (TIVA group) to BA with desflurane-remifentanil (BA group) on the postoperative opioid analgesic consumption.We divided 114 patients into the TIVA (46 patients) and BA (68 patients) groups. Opioid consumption as a primary outcome was significantly higher in the BA group than in the TIVA group during POD 2 except in the post-anesthesia care unit. The cumulative opioid consumption was significantly higher in the BA than in the TIVA group. The incidence of rescue analgesic at POD 2 was higher in the BA than in the TIVA group. In the TIVA group, remifentanil consumption was higher, and the duration of GA was shorter than that in the BA group. No statistically significant differences were observed when comparing other variables.Our results indicated that the maintenance of GA with TIVA (propofol-remifentanil) reduces opioid consumption for postoperative pain control compared to BA (desflurane-remifentanil) in patients undergoing LADG with gastroduodenostomy.

Evaluation of Renal Function at 24, 48, and 72 Hours and 3 Months After Transplant: Comparison of 3 Anesthetic Techniques.

BACKGROUND: General anesthesia is the conventional management of renal transplant, and its evolution has revolved around the development of new drugs; however, a group of patients meet conditions for neuraxial anesthesia, because of their comorbidities, who are at greater risk of complications with general anesthesia and are not favorable to grafting. METHODS: We conducted a controlled clinical trial of 109 renal transplant recipients where renal function was evaluated at 24, 48, and 72 hours and 3 months after transplant, and we compared regional, general anesthesia with inhaled anesthetic and total intravenous anesthesia. It was performed for 1 year, and serum creatinine, urea nitrogen, and electrolytes were evaluated. During the intraoperative period central venous pressure, mean arterial pressure, vasopressors, fluid therapy, diuretics, surgical time, anesthesia, hot and cold ischemia, immunosuppressants, and antihypertensives were evaluated. They were analyzed with χ2 independence and 1-way and 2-way repeated measures. RESULTS: The type of anesthesia was associated with hemodynamic stability (P = .018), the use of vasopressor (P = .005), and fluid therapy (P = .011). A value of P = .005 was found for central venous pressure at discharge from the operating room, and preincisional mean arterial pressure (P = .015) was among the types of anesthesia. Creatinine, blood urea nitrogen, sodium, and potassium were statistically significant over time (P < .001) but showed no difference between types of anesthesia. CONCLUSION: There is no difference between anesthetic techniques and clinical results over time. The personalized anesthetic technique will improve the neuroendocrine response and surgical stress, decrease the need for vasopressors and analgesics, and reduce complications.

Online monitoring of end-tidal propofol in balanced anesthesia by anisole assisted positive photoionization ion mobility spectrometer.

Online measuring end-tidal propofol concentration during balanced anesthesia is important for anesthetists to learn the patient's anesthesia depth as exhaled propofol concentration is well related to blood propofol concentration. In previous work, exhaled propofol was detected using acetone assisted negative photoionization ion mobility spectrometer, however, the existence of high concentration sevoflurane interfered the response of propofol. In this work, an anisole assisted photoionization ion mobility spectrometer operated in positive mode was developed to sensitively and selectively measure the end-tidal propofol by eliminating the interferences of exhaled humidity and sevoflurane during balanced anesthesia. Anisole molecular ion is stable enough not to go under proton transfer reaction with water presents in the exhaled breath. Hence, the exhaled humidity related peaks were eliminated and only one propofol product ion peak (K0 = 1.50 cm2 V-1 s-1) was observed. The relative standard deviation (RSD) ranging from 0.64%-0.91% showed good repeatability and the quantitative range was 0.2-40 ppbv with a response time of 4 s. Finally, the performance of the proposed method was demonstrated by monitoring end-tidal propofol of balanced anesthetized patients during gastric cancer surgery.

Propofol-based balanced anesthesia is safer in pediatric radiotherapy.

BACKROUND AND PURPOSE: To investigate the incidence of complications related to propofol-based anesthesia and the factors associated with complications in children with radiotherapy. MATERIALS AND METHODS: Patients who underwent anesthesia for external beam radiotherapy between May 2013 and November 2017 were included in the study. We assessed the age/weight, sex, oncologic diagnosis, type of radiotherapy procedure, duration of anesthesia, applied agents, and complications related to anesthesia. Complications were evaluated between group I (only propofol group) and group II (propofol plus adjuvant drugs) as respiratory and cardiac. RESULTS: In 130 patients, sedation was given for 1376 radiotherapy procedures. Of these, 1274 (1140 radiation treatment sessions and 134 computed tomography simulations) in 126 patients were propofol-based and were included in the analysis. Although respiratory complications are the most common in both groups, there were no episodes of laryngospasm, broncospasm, and no use of advanced airway intervention. The rate of complication was significantly higher in only propofol anesthesia group than in patients treated with propofol plus adjuvant drugs. In the multivariate analysis, we found three factors that were significantly associated with the risk of complications: total dose of propofol (mg/kg) (p < 0.001), anesthesia with propofol alone (as compared to propofol plus adjunct agents) (p = 0.001), and diagnosis of neuroblastoma (as compared to other diagnosis) (p = 0.043). CONCLUSION: Propofol-based anesthesia is preferred in order to minimize the rate of complications in radiotherapy anesthesia applications. The use of non-opioid adjuvants in combination with propofol to achieve a balanced anesthesia will also reduce the complications that may be encountered.

Hypnosis closed loop TCI systems in outpatient surgery. / Sistemas de TCI en circuito cerrado para la hipnosis en cirugía ambulatoria.

OBJECTIVE: Determine the influence of general anaesthesia with closed-loop systems in the results of outpatient varicose vein surgery. PATIENTS AND METHODS: Retrospective observational study including data from 270 outpatients between 2014 and 2015. The patients were divided into 2 groups according to the type of general anaesthesia used. The CL Group included patients who received propofol in closed-loop guided by BIS and remifentanil using TCI, and the C Group received non-closed-loop anaesthesia. Age, sex, surgical time, discharge time and failure of outpatient surgery were recorded. Quantitative data were checked for normal distribution by the method of Kolmogorov-Smirnov-Lilliefors. Differences between groups were analysed by a Student-t-test or Mann-Whitney-Wilcoxon test, depending on their distribution. Categorical data were analysed by a Chi-squared test. We used Kaplan-Meier estimator and the effect size (calculated by Cohen's d) to study the discharge time. Statistical analysis was performed using R 3.2.3 binary for Mac OS X 10.9. RESULTS: There were no significant differences in age, sex and surgical time and failure of outpatient surgery. Discharge time was different in both groups: 200 (100) vs. 180 (82.5) minutes, C Group and CL Group, respectively (data are median and interquartile rank); P=.005. CONCLUSION: The use of closed-loop devices for the hypnotic component of anaesthesia hastens discharge time. However, for this effect to be clinically significant, some improvements still need to be made in our outpatient surgery units.

[ANAESTHETIC MANAGEMENT OF RECONSTRUCTIVE SURGERY ON THE AORTIC ARCH: THE NUANCES OF ORGAN PROTECTION].

UNLABELLED: Aortic arch reconstruction is one of the most difficult surgical procedures. Therefore the aims of our study were: to choose appropriate flow rate for antegrade cerebral perfusion and assess its adequacy in relation to cerebral metabolic demands; to evaluate safety of temperature settings during the surgery; to assess the effectiveness of chosen protocol for brain and visceral organ protection during aortic arch reconstruction surgery. Our study included 67 patients. Patients of the first group (n = 33) underwent aortic arch reconstruction with antegrade cerebral perfusion and hypothermic circulatory arrest (target core temperature 26 °C). The second group (n = 34) underwent ascending aorta repair using cardiopulmonary bypass with modest hypothermia (target core temperature 32 °C). Cerebral and tissue oxygenation monitoring was performed in all patients. In the first group transcranial Doppler monitoring and jugular venous bulb catheterization were performed. Target core temperature during rewarming was 36 °C. In the first group air-warming device in addition to fluid warming was used. In all patients cognitive function was assessed before and after surgery. The multimodal monitoring allowed to dynamically adjust flow rate of antegrade cerebral perfusion. As a result cerebral SO2 and linear velocity were maintained in acceptable range, while flow rate varied significantly from 5.8 to 16.5 ml/ kg/min (average rate 13.4 ± 3.69 ml/kg/min). CONCLUSION: Combined use of cerebral oximetry and transcranial Doppler monitoring allows assessing how oxygen delivery meets metabolic demands of the brain during antegrade cerebral perfusion. This method allows to maintain the proper flow rate of antegrade cerebral perfusion and to choose an appropriate modification of perfusion (unilateral vs bilateral). Multichannel monitoring of core temperature and combined use of air- and fluid warming techniques are required for effective temperature management.

Intraoperative neurophysiological monitoring during spine surgery with total intravenous anesthesia or balanced anesthesia with 3% desflurane.

Total intravenous anesthesia (TIVA) with propofol and opioids is frequently utilized for spinal surgery when somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (tcMEPs) are monitored. Many anesthesiologists would prefer to utilize low dose halogenated anesthetics (e.g. 1/2 MAC). We examined our recent experience using 3% desflurane or TIVA during spine surgery to determine the impact on propofol usage and on the evoked potential responses. After institutional review board approval we conducted a retrospective review of a 6 month period for adult spine patients who were monitored with SSEPs and tcMEPs. Cases were included for the study if anesthesia was conducted with propofol-opioid TIVA or 3% desflurane supplemented with propofol or opioid infusions as needed. We evaluated the propofol infusion rate, cortical amplitudes of the SSEPs (median nerve, posterior tibial nerve), amplitudes and stimulation voltage for eliciting the tcMEPs (adductor pollicis brevis, tibialis anterior) and the amplitude variability of the SSEP and tcMEP responses as assessed by the average percentage trial to trial change. Of the 156 spine cases included in the study, 95 had TIVA with propofol-opioid (TIVA) and 61 had 3% expired desflurane (INHAL). Three INHAL cases were excluded because the desflurane was eliminated because of inadequate responses and 26 cases (16 TIVA and 10 INHAL) were excluded due to significant changes during monitoring. Propofol infusion rates in the INHAL group were reduced from the TIVA group (average 115-45 µg/kg/min) (p<0.00001) with 21 cases where propofol was not used. No statistically significant differences in cortical SSEP or tcMEP amplitudes, tcMEP stimulation voltages nor in the average trial to trial amplitude variability were seen. The data from these cases indicates that 1/2 MAC (3%) desflurane can be used in conjunction with SSEP and tcMEP monitoring for some adult patients undergoing spine surgery. Further studies are needed to confirm the relative benefits versus negative effects of the use of desflurane and other halogenated agents for anesthesia during procedures on neurophysiological monitoring involving tcMEPs. Further studies are also needed to characterize which patients may or may not be candidates for supplementation such as those with neural dysfunction or who are opioid tolerant from chronic use.

Balanced anesthesia with sevoflurane does not alter redox status in patients undergoing surgical procedures.

Despite the effectiveness and safety of anesthetics, some unanswered questions remain concerning their toxicity and effects on cellular redox balance. To test for possible toxic effects of balanced anesthesia maintained with the volatile anesthetic sevoflurane, we evaluated oxidative stress during and after general anesthesia in 15 adult patients without comorbidities who underwent elective minor surgical procedures. Venous blood samples were collected at baseline, before anesthesia (t0); after anesthesia induction and immediately before surgery (t1); 2h after the beginning of anesthesia (t2); and on the day following surgery (t3). Antioxidant defense was determined by fluorometry. Oxidative stress markers included oxidative DNA damage, evaluated by the alkaline comet assay, and plasma malondialdehyde (MDA), assessed by high performance liquid chromatography (HPLC). No increase in oxidized DNA damage or antioxidant defense was observed. Plasma MDA increased only at t3 compared with t2. Balanced sevoflurane-maintained anesthesia appears neither to damage DNA nor to alter redox status.

To clarify features of photoplethysmography in monitoring balanced anesthesia, compared with Cerebral State Index.

BACKGROUND: Although photoplethysmography and cerebral state index (CSI) have been used as indices in monitoring vital signs perioperatively, there are only a few reports comparing the performance of photoplethysmography with CSI in monitoring anaesthesia depth. The aim of the present study was to clarify features of photoplethysmography in monitoring balanced general anesthesia compared with CSI. MATERIAL AND METHODS: Forty-five patients undergoing elective operation under general anaesthesia were enrolled in this study. Anaesthesia was induced with target-controlled infusion propofol. The photoplethysmogram, CSI, Modified Observer's Assessment of Alertness/Sedation Scale (MOAAS), and mean arterial pressure (MAP) were continuously monitored and recorded. Finger photoplethysmogram amplitude (PPGA) and pulse beat interval (PBI) were calculated off-line. RESULTS: For the period of time from pre-induction to pre-intubation, the coefficient of correlation between MOAAS and CSI was higher than those between MOAAS and PPGA, PBI, and MAP. CSI showed higher prediction probabilities (Pk) to differentiate the levels of MOAAS than did PPGA, PBI, and MAP. PPGA, PBI, and MAP values showed significant differences between before and after intubation, as well as pre- and post-incision (P<0.05), but no significant changes in cerebral state index (P>0.05). CONCLUSIONS: The present study shows that photoplethysmography-derived parameters appear to be more suitable in monitoring the nociceptive component of balanced general anesthesia, while CSI performs well in detecting the sedation or hypnotic component of balanced general anesthesia.

Short-term Parameters of Heart Rate Variability During Balanced Anaesthesia with Administration of Two Different Inhalation Anaesthetics.

INTRODUCTION: Heart rate variability which denotes variations of the length of consecutive heart cycles has been suggested to reflect the modulation of heart rate by autonomic nervous system. METHODS: Sixty four patients of ASA I and ASA II status scheduled for elective abdominal surgical procedures were randomly allocated to group 1 and group 2. Premedication and induction of anaesthesia were performed with same agents. After orotracheal intubation maintenance of balanced anaesthesia was based on administration of same induction agents,opioids and muscle relaxant while delivery of gaseous mixture with sevoflurane in the group 1 (n=32) and isoflurane in the group 2(n=32). Haemodynamic parameters were monitored in perioperative and electrocardiogram was recorded by holter ECG recorder, while the analysis of the parameters were performed by corresponding softwares . Data were presented as mean values of logarithmic (natural logarithm) values of the power of the total spectrum of heart rate variability(TP), mean values of the logarithmic values of low frequency band (LF), mean values of the logarithmic values of high frequency range(HF), and mean values of SD1 and SD2 parameters. RESULTS: Analysis of the values of hemodynamic parameters has shown changes of haemodynamic parameters during perioperative period without significant statistical differences between the groups. Analysis of the logarhitmic values of parameters of heart rate variability of frequency domain has shown changes of the total spectrum power and LF and HF spestra with variations of the values of total power spectrum and individual components of the spectrum of heart rate variability during the balanced anaesthesia with administration of two different inhalation anaesthetics, without statistically significant differences between the groups. CONCLUSION: The results have shown that during balanced anaesthesia with two different inhalation anaesthetics there are variations of haemodynamic variables and parameters of heart rate variability without statistically significance that could show the difference between the groups and different agents administered.

Effects of lidocaine administration via continuous rate infusion on the minimum alveolar concentration of isoflurane in New Zealand White rabbits (Oryctolagus cuniculus).

OBJECTIVE: To evaluate the effect of a continuous rate infusion (CRI) of lidocaine on the minimum alveolar concentration (MAC) of isoflurane in rabbits. ANIMALS: Five 12-month-old female New Zealand White rabbits (Oryctolagus cuniculus). PROCEDURES: Rabbits were anesthetized with isoflurane. Baseline isoflurane MAC was determined by use of the tail clamp technique. A loading dose of lidocaine (2.0 mg/kg, IV) was administered followed by a CRI of lidocaine at 50 µg/kg/min. After 30 minutes, isoflurane MAC was determined. Another loading dose was administered, and the lidocaine CRI then was increased to 100 µg/kg/min. After 30 minutes, isoflurane MAC was determined again. Plasma samples were obtained for lidocaine analysis after each MAC determination. RESULTS: Baseline isoflurane MAC was 2.09%, which was similar to previously reported values in this species. Lidocaine CRI at 50 and 100 µg/kg/min induced significant reductions in MAC. The 50 µg/kg/min CRI resulted in a mean plasma lidocaine concentration of 0.654 µg/mL and reduction of MAC by 10.5%. The 100 µg/kg/min CRI of lidocaine resulted in a mean plasma concentration of 1.578 µg/mL and reduction of MAC by 21.7%. Lidocaine also induced significant decreases in arterial blood pressure and heart rate. All cardiopulmonary variables were within reference ranges for rabbits anesthetized with inhalation anesthetics. No adverse effects were detected; all rabbits had an uncomplicated recovery from anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE: Lidocaine administered as a CRI at 50 and 100 µg/kg/min decreased isoflurane MAC in rabbits. The IV administration of lidocaine may be a useful adjunct in anesthesia of rabbits.

Balanced anesthesia and constant-rate infusions in horses.

Balanced anesthetic techniques are commonly used in equine patients, and include the combination of a volatile anesthetic with at least one injectable anesthetic throughout the maintenance period. Injectable anesthetics used in balanced anesthesia include the α2-agonists, lidocaine, ketamine, and opioids, and those with muscle-relaxant properties such as benzodiazepines and guaifenesin. Administration of these injectable anesthetics is best using constant-rate infusions based on the pharmacokinetics of the drug, which allows steady-state concentrations and predictable pharmacodynamic actions. This review summarizes the different drug combinations used in horses, and provides calculated recommended doses based on the pharmacokinetics of individual drugs.

Avaliação da resposta clínica, inflamatória e infecciosa de crianças submetidas à cirurgia de coarctação da aorta com ou sem uso de precondicionamento isquêmico por pinçamento da aorta torácica descendente / Assessment of clinical, inflammatory and infectious response in children undergoing surgery for aortic coarctation with or without ischemic preconditioning by clamping of the descending thoracic aorta

O precondicionamento isquêmico é o mais poderoso método experimental de proteção celular e pode ser aplicado em cirurgias que ocasionem isquemia tecidual como na correção de coarctação da aorta. Objetivo: Avaliar os resultados clínicos, inflamatórios e infecciosos de crianças submetidas à cirurgia de coarctação da aorta com ou sem uso de precondicionamento isquêmico por pinçamento da aorta torácica. Como desfechos primários foram avaliados os Eventos Adversos Principais (EAP) e o óbito em até 30 dias. Método: Foram analisados retrospectivamente os dados clínicos de 104 pacientes submetidos consecutivamente a cirurgia de coarctação da aorta entre dezembro de 2007 e dezembro de 2012 no Instituto Nacional de Cardiologia, Centro Pediátrico da Lagoa e Hospital Prontobaby na cidade do Rio de Janeiro. Foram constituídos dois grupos, G PRE: 27 pacientes submetidos ao precondicionamento e G CONT: 77 pacientes de controle. Resultados: Houve predomínio do sexo masculino, 62,5 por cento, a média de peso foi de 4,04±3,07 kg e 11,53 por cento tinham peso < 2,5kg. A média de idade foi de 3,82±2, com mediana de 1,04 meses. A cirurgia foi realizada em caráter de emergência em 81,48 por cento no G PRE (p<0,001) e o Basic e o Comprehensive Aristotle Score foram maiores no G CONT (p<0,001). A bandagem da artéria pulmonar foi realizada em 37,9 por cento do G PRE contra 9,09 por cento do G CONT e 81,48 por cento do G PRE tiveram anastomose estendida no arco aórtico (p<0,001). As complicações aconteceram em 66,23 por cento no G CONT e em 22,22% no G PRE (p<0,001)...

Ischemic preconditioning is the most powerful experimental method for cellprotection and can be applied in surgeries which result in tissue ischemia as correction ofcoarctation of the aorta.Objective: To evaluate the clinical, inflammatory and infectious in children undergoingsurgery for aortic coarctation with and without ischemic preconditioning. As primaryoutcomes will be Major Adverse Events (MAE) and death within 30 days.Methods: We retrospectively evaluated the clinical data of 104 consecutive patientsundergoing surgery for aortic coarctation between December 2007 and December 2012 at theInstituto Nacional de Cardiologia, Centro Pediátrico da Lagoa e Hospital Prontobaby in thecity of Rio de Janeiro. Two groups were composed, G PRE: 27 patients underwentpreconditioning and G CONT: 77 control patients.Results: Male gender were 62.5 percent, the mean weight was 4.04±3.07 kg and 11.53 percent hadweight <2.5 kg. The mean age was 3.82 ± 2.05 with a median of 1.04 months. The G PREhad 81.48% of emergency surgeries (p <0.001) and Basic and Comprehensive Aristotle scorewere higher in G PRE (p <0.001). Pulmonary artery banding was performed in 37.9 percent of GPRE and in 9.09 percent of G CONT and 81.48 percent of G PRE had extended aortic arch anastomosis(p <0.001)...

Effects of lidocaine constant rate infusion on sevoflurane requirement, autonomic responses, and postoperative analgesia in dogs undergoing ovariectomy under opioid-based balanced anesthesia.

The effects of constant rate infusion (CRI) of lidocaine on sevoflurane (SEVO) requirements, autonomic responses to noxious stimulation, and postoperative pain relief were evaluated in dogs undergoing opioid-based balanced anesthesia. Twenty-four dogs scheduled for elective ovariectomy were randomly assigned to one of four groups: BC, receiving buprenorphine without lidocaine; FC, receiving fentanyl without lidocaine; BL, receiving buprenorphine and lidocaine; FL, receiving fentanyl and lidocaine. Dogs were anesthetized with intravenous (IV) diazepam and ketamine and anesthesia maintained with SEVO in oxygen/air. Lidocaine (2mg/kg plus 50 µg/kg/min) or saline were infused in groups BL/FL and BC/FC, respectively. After initiation of lidocaine or saline CRI IV buprenorphine (0.02 mg/kg) or fentanyl (4 µg/kg plus 8 µg/kg/h CRI) were administered IV in BC/BL and FC/FL, respectively. Respiratory and hemodynamic variables, drug plasma concentrations, and end-tidal SEVO concentrations (E'SEVO) were measured. Behaviors and pain scores were subjectively assessed 1 and 2h post-extubation. Lidocaine CRI produced median drug plasma concentrations <0.4 µg/mL during peak surgical stimulation. Lidocaine produced a 14% decrease in E'SEVO in the BL (P<0.01) but none in the FL group and no change in cardio-pulmonary responses to surgery or postoperative behaviors and pain scores in any group. Thus, depending on the opioid used, supplementing opioid-based balanced anesthesia with lidocaine (50 µg/kg/min) may not have any or only a minor impact on anesthetic outcome in terms of total anesthetic dose, autonomic responses to visceral nociception, and postoperative analgesia.