The optimal effective concentration of lidocaine to reduce pain on injection of propofol

The use of remimazolam versus propofol for induction and maintenance of general anesthesia: A systematic review and meta-analysis

Background: The primary objective of this study was to compare the risk of hypotension, as well as the induction and recovery characteristics between remimazolam and propofol in patients receiving surgery under general anesthesia. Methods: The Embase, Medline, Google scholar, and the Cochrane Library databases were searched from inception to March 2022 for randomized controlled trials The primary outcome was the risk of post-induction hypotension between the two agents, while the secondary outcomes included anesthetic depth, induction efficacy, time to loss of consciousness (LOC), hemodynamic profiles, time to eye opening, extubation time as well as the incidence of injection pain and postoperative nausea/vomiting (PONV). Results: Meta-analysis of eight studies published from 2020 to 2022 involving 738 patients revealed a significantly lower risk of post-induction hypotension with the use of remimazolam compared to that with propofol [risk ratio (RR) = 0.57, 95% confidence interval (CI): 0.43 to 0.75, p < 0.0001, I2 = 12%, five studies, 564 patients]. After anesthetic induction, the anesthetic depth measured by bispectral index (BIS) was lighter in the remimazolam group than that in the propofol group (MD = 9.26, 95% confidence interval: 3.06 to 15.47, p = 0.003, I2 = 94%, five studies, 490 patients). The time to loss of consciousness was also longer in the former compared to the latter (MD = 15.49 s, 95%CI: 6.53 to 24.46, p = 0.0007, I2 = 61%, three studies, 331 patients). However, the use of remimazolam correlated with a lower risk of injection pain (RR = 0.03, 95%CI: 0.01 to 0.16, p < 0.0001, I2 = 0%, three studies, 407 patients) despite comparable efficacy of anesthetic induction (RR = 0.98, 95%CI: 0.9 to 1.06, p = 0.57, I2 = 76%, two studies, 319 patients). Our results demonstrated no difference in time to eye opening, extubation time, and risk of PONV between the two groups. Conclusion: Remimazolam was associated with a lower risk of post-induction hypotension after anesthetic induction compared with propofol with similar recovery characteristics. Further studies are required to support our findings. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/; Identifier: CRD42022320658.

Lidocaine for reducing propofol-induced pain on induction of anaesthesia in adults

BACKGROUND

Pain on propofol injection is an untoward effect and this condition can reduce patient satisfaction. Intravenous lidocaine injection has been commonly used to attenuate pain on propofol injection. Although many studies have reported that lidocaine was effective in reducing the incidence and severity of pain, nevertheless, no systematic review focusing on lidocaine for preventing high-intensity pain has been published.

OBJECTIVES

The objective of this review was to determine the efficacy and adverse effects of lidocaine in preventing high-intensity pain on propofol injection.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 10), Ovid MEDLINE (1950 To October 2014), Ovid EMBASE (1988 to October 2014), LILACS (1992 to October 2014) and searched reference lists of articles.We reran the search in November 2015. We found 11potential studies of interest, those studies were added to the list of 'Studies awaiting classification' and will be fully incorporated into the formal review findings when we update the review.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) using intravenous lidocaine injection as an intervention to decrease pain on propofol injection in adults. We excluded studies without a placebo or control group.

DATA COLLECTION AND ANALYSIS

We collected selected studies with relevant criteria. We identified risk of bias in five domains according to the following criteria: random sequence generation, allocation concealment, adequacy of blinding, completeness of outcome data and selective reporting. We performed meta-analysis by direct comparisons of intervention versus control. We estimated the summary odds ratios (ORs) and 95% confidence intervals using the random-effects Mantel-Haenszel method in RevMan 5.3. We used the I(2) statistic to assess statistical heterogeneity. We assessed overall quality of evidence using the GRADE approach.

MAIN RESULTS

We included 87 studies, 84 of which (10,460 participants) were eligible for quantitative analysis in the review. All participants, aged 13 years to 89 years, were American Society of Anesthesiologists (ASA) I-III patients undergoing elective surgery. Each study was conducted in a single centre in high- , middle- and low-income countries worldwide. According to the risk of bias assessment, all except five studies were identified as being of satisfactory methodological quality, allowing 84 studies to be combined in the meta-analysis. Five of the 84 studies were assessed as high risk of bias: one for participant and personnel blinding, one for incomplete outcome data, and three for other potential sources of bias.The overall incidence of pain and high-intensity pain following propofol injection in the control group were 64% (95% CI 60% to 67.9%) and 38.1% (95% CI 33.4% to 43.1%), respectively while those in the lidocaine group were 30.2% (95% CI 26.7% to 33.7%) and 11.8% (95% CI 9.7% to 13.8%). Both lidocaine admixture and pretreatment were effective in reducing pain on propofol injection (lidocaine admixture OR 0.19, 95% CI 0.15 to 0.25, 31 studies, 4927 participants, high-quality evidence; lidocaine pretreatment OR 0.13, 95% CI 0.10 to 0.18, 43 RCTs, 4028 participants, high-quality evidence). Similarly, lidocaine administration could considerably decrease the incidence of pain when premixed with the propofol (OR 0.19, 95% CI 0.15 to 0.24, 36 studies, 5628 participants, high-quality evidence) or pretreated prior to propofol injection (OR 0.14, 95% CI 0.11 to 0.18, 52 studies, 4832 participants, high-quality evidence). Adverse effects of lidocaine administration were rare. Thrombophlebitis was reported in only two studies (OR not estimated, low-quality evidence). No studies reported patient satisfaction.

AUTHORS' CONCLUSIONS

Overall, the quality of the evidence was high. Currently available data from RCTs are sufficient to confirm that both lidocaine admixture and pretreatment were effective in reducing pain on propofol injection. Furthermore, there were no significant differences of effect between the two techniques.

Intravenous lidocaine increases the depth of anaesthesia of propofol for skin incision--a randomised controlled trial

BACKGROUND

The anaesthetic potency of intravenous propofol is quantified by its Cp50 value, which is defined as the plasma concentration required to prevent movement response in 50% of patients to surgical stimuli. We hypothesised that, in addition to propofol anaesthesia, an intravenous bolus of lidocaine 1.5 mg/kg will decrease the Cp50 value of propofol during anaesthesia.

METHODS

We enrolled 54 elective surgical patients undergoing propofol-based anaesthesia, and randomised them to either lidocaine 1.5 mg/kg, lidocaine 0.5 mg/kg or placebo (NaCl 0.9%) 3 min before skin incision. The propofol Cp50 value was then calculated using the 'up-and-down' method of Dixon and Massey.

RESULTS

There was no significant reduction in propofol requirements after the administration of 0.5 mg/kg lidocaine from 8.5 μg/ml [confidence interval (CI) 6.0-11.625] to 8.25 μg/ml (CI 6.75-9.76); however, a bolus of 1.5 mg/kg lidocaine decreased the Cp50 value of propofol by 42% from 8.5 μg/ml (CI 6.0-11.625) to 4.92 μg/ml (CI 4.5-5.78) (P < 0.05).

CONCLUSION

An intravenous bolus injection of 1.5 mg/kg lidocaine 2% caused a significant reduction of the propofol Cp50 value.

Efficacy of different doses of lidocaine in the prevention of pain due to propofol injection: a randomized, open-label trial in 120 patients

BACKGROUND

The incidence of pain due to propofol injection is high, but the most efficacious method of preventing this pain has not been identified.

OBJECTIVE

The aim of this study was to investigate the efficacy of lidocaine, at different doses and schedules, on propofol injection pain.

METHODS

In this open-label study, conducted at the Department of Anaesthesiology, Erciyes University Gevher Nesibe Hospital (Kayseri, Turkey), patients with American Society of Anesthesiologists Patient Acuity Classification I-II (ASA I-II) (ie, patients with absent [I] or mild [II] underlying systemic disease) aged 18 to 60 years undergoing various types of surgery were eligible. Patients were randomized to 1 of 4 treatment groups: group 1 received propofol; group 2, a combination of propofol plus lidocaine 10 mg; group 3, lidocaine 10 mg 30 seconds before propofol administration; and group 4, lidocaine 1 mg/kg 30 seconds before propofol administration (all drugs were administered intravenously). After cessation of the standard replacement fluid infusion (isotonic saline), propofol was given at a rate of 2 mL every 5 seconds until a dose of 2 mg/kg was reached. The patients were asked to rate their pain according to the following scale: 0 = none, 1 = mild, 2 = moderate, and 3 = severe.

RESULTS

A total of 120 patients (61 men, 59 women; mean [SD] age, 38.7 [8.9] years) were enrolled in the study (n = 30 patients in each group). The incidence of injection pain in groups 2 and 4 was significantly lower than that in groups 1 and 3 (all P<0.05), but no significant difference in the incidence of pain was found between groups 1 and 3. The incidence of pain in group 2 was significantly lower than that in group 4 (P<0.05).

CONCLUSIONS

In this study population, the addition of 10 mg of lidocaine to propofol 2 mg/kg, or the administration of 1 mg/kg of lidocaine 30 seconds before the administration of propofol 2 mg/kg, effectively decreased pain caused by propofol injection. Furthermore, a lower dose of lidocaine could be used. Based on our results, we suggest mixing propofol with 10 mg of lidocaine to decrease pain due to propofol injection during anesthesia induction.

Efficacy of intravenous lidocaine to reduce pain and distress associated with propofol infusion in pediatric patients during procedural sedation

BACKGROUND

Research suggests that young children experience an increased incidence and severity of discomfort during propofol infusion. Evaluations of varied interventions to reduce or eliminate this discomfort with adult subjects suggest that premedication with intravenously administered lidocaine (0.5 mg/kg) offers the best overall effectiveness.

OBJECTIVE

Because this regimen's efficacy in a pediatric population is undocumented, we conducted a randomized, double-blind, placebo-controlled study to determine the effectiveness of intravenous lidocaine pretreatment to alleviate pain in pediatric subjects before propofol infusion.

METHODS

Subjects (aged 2-7 years) scheduled for painless diagnostic procedures received either a saline placebo or 1 of 2 lidocaine doses before administering propofol. To capture the patient's baseline behavioral state, a trained observer administered the validated face, legs, activity, cry, consolability pain assessment scale before propofol infusion. During deep sedation induction, the sedating physician, a trained research assistant, and the patient's parent documented maximum distress using a 100-mm visual analog scale (VAS).

RESULTS

Ninety-one subjects participated. We found no difference in VAS pain scores between groups pretreated with lidocaine 0.25 mg/kg, lidocaine 0.5 mg/kg, and placebo. Statistical analysis also found no interrater differences between parents, physician, or observer VAS scores.

CONCLUSIONS

Our data do not support using lidocaine pretreatment to alleviate pain/discomfort in pediatric patients during propofol infusion.

Comparison of auditory evoked potential index and clinical signs as indicator for laryngeal mask airway insertion

OBJECTIVE

Auditory evoked potential (AEP) index is one of the several physiological parameters for assessing the depth of anesthesia. The purpose of this study was to investigate whether the AEP monitoring could provide a better information for assessment of anesthesia level in classic laryngeal mask airway (C-LMA) insertion than the use of clinical signs in general anesthesia with single standard dose of intravenous propofol and fentanyl.

METHODS

One hundred and seventy adult patients requiring general anesthesia for minor surgery were recruited and randomized to receive AEP monitoring (group A) or judgment of clinical signs (group B) for assessment of anesthesia depth and optimal condition to insert the C-LMA. The insertion conditions, including jaw relaxation, movements, presence of airway trauma and airway reflex, successful insertion rate and induction time were recorded and compared.

RESULTS

The two groups were demographically similar. In group A, baseline heart rate was slower than group B (74 ± 14 vs. 78 ± 14 beats/min, p = 0.0267) and persisted throughout the whole study period. There was no significant difference in the change of heart rate during induction of general anesthesia between both groups. The incidence of movement was reduced in group A patients with AEP monitoring in comparison with group B patients (2.4% vs. 28.2%, p < 0.0001); of the unwanted events, swallowing was 0% versus 7.1%, p = 0.0126; laryngospasm was 0% versus 4.7%, p  = 0.0430 and emergence of airway reflex was 1.2% versus 11.8%, p = 0.0050; the successful insertion rate was 100% versus 94.1%, p = 0.0232; and jaw relaxation was 83.5% versus 70.6%, p = 0.0448. There were no differences between both groups in trauma and induction time.

CONCLUSION

This study demonstrated that AEP index provided better information for C-LMA insertion with higher successful rate, less emergence of airway reflex and lower incidence of movement during induction of general anesthesia with single dose of intravenous propofol and fentanyl.

Reduction of pain on injection of propofol: combination of pretreatment of remifentanil and premixture of lidocaine with propofol

BACKGROUNDS AND OBJECTIVE

There is a high incidence of pain following intravenous injection of propofol, and many studies have been conducted to find a way of reducing this. The administration of lidocaine and, recently, remifentanil has also been used for this purpose, but it is only partially effective. Thus, the purpose of this study was to investigate the analgesic effect of a combination of pretreatment with remifentanil and premixture of lidocaine with propofol and to compare either treatment alone during propofol injection in dorsal hand-veins.

METHODS

In a prospective, randomized, double-blinded trial, we studied 141 adult patients scheduled for elective surgery. The combination of pretreatment of remifentanil (0.35 microg kg(-1) min(-1)) and a premixture of lidocaine with propofol (mixture of propofol 1% and lidocaine 1% in a 10:1 ratio) was compared with either treatment alone in the prevention of pain on propofol injection. Pain was assessed on a four-point scale (0=none, 1=mild, 2=moderate, 3=severe) during propofol injection. Patients in Group B received remifentanil (0.35 microg kg(-1) min(-1)) 30 s before the injection of propofol.

RESULTS

The reduction of pain on propofol injection was similar in both the remifentanil pretreatment and lidocaine premixture groups (62.2% vs. 62.2%). Combination therapy was associated with a higher incidence of patients without pain (91.3%) than either treatment alone (P<0.001). On analysing the injection pain scores, we found a significant reduction of the score in the remifentanil and lidocaine Group C compared with the lidocaine Group A (P<0.001) and the remifentanil Group B (P<0.001).

CONCLUSIONS

The combination of pretreatment of remifentanil and premixture of lidocaine with propofol was more effective in reducing the incidence of pain on injection of propofol than either treatment alone.

Anesthetic properties of a propofol microemulsion in dogs

Microemulsions of propofol with nanometer droplet diameter are alternatives to soybean macroemulsions for inducing anesthesia, and may have important advantages. We used a propofol (10 mg/mL) microemulsion (particle diameter 24.5 +/- 0.5 nm) and a commercial macroemulsion to induce anesthesia in dogs (n = 10) using a randomized, crossover design separated by a 7-day rest interval. The end points were loss of leg withdrawal after a toe pinch and changes in vital signs. Venous blood samples were acquired at multiple times to measure plasma propofol concentrations and indices of erythrocytes, leukocytes, and coagulation. All dogs were rendered insensitive to pain followed by successful recovery without noticeable complications. Comparing indices between microemulsion and macroemulsion formulations, no differences were noted with respect to dose (10.3 +/- 1.2 and 9.7 +/- 1.6 mg/kg, respectively, P = 0.39), time to induction (1.0 +/- 0.1 and 1.0 +/- 0.2 min, P = 0.39), time to recovery (17.4 +/- 4.6 and 18.2 +/- 3.8 min, P = 0.70), heart rate (P = 0.62), arterial blood pressure (P = 0.81), respiratory rate (P = 0.60), hemogram variables, prothrombin time (P = 0.89), activated partial thromboplastin time (P = 0.76), fibrinogen concentration (P = 0.52), platelet concentration (P = 0.55), or plasma propofol concentrations (P = 0.20). Induction with a propofol microemulsion or macroemulsion did not significantly vary with respect to vital signs, the hemogram, clotting variables, and plasma propofol concentrations.

Preventing pain during injection of propofol: effects of a new emulsion with lidocaine addition

BACKGROUND AND OBJECTIVE

Previous studies found that lidocaine addition to propofol long-chain triglyceride was associated with a lower incidence of injection pain than medium-chain triglyceride/long-chain triglyceride formulation, but the incidence was still high (31-40%). Our study investigated whether the incidence of injection pain could be further reduced by the addition of lidocaine (10 mg, 20:1) to propofol medium-chain triglyceride/long-chain triglyceride.

METHODS

In a randomized double-blind controlled trial 464 patients scheduled to undergo regional anaesthesia were assigned to receive one of the following four options: propofol medium-chain triglyceride/long-chain triglyceride + lidocaine, propofol long-chain triglyceride + lidocaine, propofol medium-chain triglyceride/long-chain triglyceride or propofol long-chain triglyceride. Propofol was injected to reach grade 3 of the Observer's Assessment of Alertness/Sedation scale.

RESULTS

Incidence of injection pain was 18% in the propofol medium-chain triglyceride/long-chain triglyceride + lidocaine group, 31% in the propofol long-chain triglyceride + lidocaine group, 47% in the propofol medium-chain triglyceride/long-chain triglyceride group and 60% in the long-chain triglyceride group. Propofol medium-chain triglyceride/long-chain triglyceride + lidocaine was associated with a statistically significant reduced incidence of injection pain compared with propofol long-chain triglyceride +lidocaine (P =0.0249, number needed to treat =7.7).

CONCLUSIONS

Premixing propofol medium-chain triglyceride/long-chain triglyceride with lidocaine is one of the most effective measures currently available to reduce the incidence of injection pain in sedated patients during regional anaesthesia.

Clonidine-ephedrine combination reduces pain on injection of propofol and blunts hemodynamic stress responses during the induction sequence

STUDY OBJECTIVES

To evaluate the effects of clonidine and ephedrine on propofol-induced pain and on hemodynamic changes during the induction sequence.

DESIGN

This was a prospective, randomized, double-blind study.

SETTING

The study was conducted at a university hospital.

PATIENTS

200 ASA physical status I or II adult patients scheduled for elective surgery.

INTERVENTIONS

Patients were randomly allocated to one of 4 groups (50 patients per group): clonidine-ephedrine (CE), clonidine-saline (CS), diazepam-ephedrine (DE), and diazepam-saline (DS). Thirty seconds after the administration of ephedrine or saline, propofol 2 mg/kg was infused at a rate of 18.3 mL/min.

MEASUREMENTS

Patients were asked whether they had pain due to propofol injection. A blinded investigator evaluated the pain score: 0 = no pain, 1 = mild pain, 2 = severe pain without behavioral signs such as grimace or arm withdrawal movement, and 3 = severe pain accompanied by behavioral signs. Mean arterial blood pressure (MAP) and heart rate (HR) were measured at 1-minute intervals from just before the administration of ephedrine or saline to 5 minutes after the tracheal intubation.

MAIN RESULTS

Median pain score in CE was significantly lower than those in the other groups (P < 0.0001). Pain scores in CS and DE were significantly lower than that in DS (P < 0.05). Ephedrine increased HR in CE and DE (P < 0.05), but clonidine did not augment the effect. Mean arterial blood pressure before tracheal intubation decreased to comparable values in all groups. After the intubation, mean arterial blood pressure and HR in CE and CS were significantly lower than those in DE and DS (P < 0.05).

CONCLUSIONS

Combination of clonidine and ephedrine effectively reduced propofol-induced pain, but did not prevent propofol-induced hypotension. Clonidine did not augment low dose of ephedrine-induced increase in HR and produced stable hemodynamic condition during the induction sequence.

Propofol-Induced Injection Pain: Comparison of a Modified Propofol Emulsion to Standard Propofol with Premixed Lidocaine

Propofol is well known for its association with pain on injection. The most frequently used method to reduce this pain is premixture with lidocaine. Recently, a modified lipid emulsion of propofol containing medium-chain triglycerides (MCT) with long-chain triglycerides (LCT), in contrast to the usual LCT formulation, has been advocated to alleviate pain. In a randomized, prospective, controlled, double-blind study on 222 surgical patients, we compared the effect of the two solutions on the incidence and intensity of injection pain. Patients were randomly allocated to receive either propofol MCT/LCT (group M; n = 109) or standard propofol LCT with the addition of 20 mg of lidocaine (2 mL of lidocaine 1%) to 200 mg of propofol (group L; n = 113). Pain scores were assessed using a verbal analog scale (VAS) ranging from 0-10. Group L was found to have significantly less pain on the injection of propofol (mean VAS, 2.5 +/- 2.9) (mean +/- sd) than group M (mean VAS, 3.8 +/- 3.2; P = 0.002). Regarding postoperative recall of pain on injection, patients in group L indicated significantly less pain (mean VAS, 2.2 +/- 2.4) than patients in group M (mean VAS, 3.0 +/- 2.7; P = 0.02). Premixing of 20 mg of lidocaine (2 mL of lidocaine 1%) to 200 mg of standard propofol LCT causes less pain on injection than propofol MCT/LCT and thus increases patient comfort.

Pretreatment with intravenous ketamine reduces propofol injection pain

BACKGROUND

Paediatric procedural sedation using propofol has been shown to be safe and effective and is widely used. Pain at the injection site is a frequent complaint and can be particularly distressing for children, especially for those undergoing repeated procedures. Ketamine has analgesic properties and can diminish the incidence of propofol infusion pain in adults. The aim of the study was to investigate whether pretreatment with ketamine would reduce infusion line pain in propofol sedation in children.

METHODS

We performed a prospective, randomized, double-blind trial in a paediatric sedation unit of a tertiary referral teaching hospital. A total of 122 children admitted for gastroscopy were randomly allocated into two groups. Group 1 received atropine and ketamine before propofol infusion. Group 2 received atropine, normal saline solution, and a mixture of propofol with lidocaine. The main outcome measure evaluated was pain associated with the infusion and secondary outcome measures were mean medium arterial pressure decrease and desaturation.

RESULTS

The incidence of pain of the infusion was significantly lower in patients pretreated with ketamine (8% vs 37%, P = 0.0001).

CONCLUSIONS

Pretreatment with ketamine (0.5 mg.kg-1) is very effective in preventing propofol infusion pain.

In children, nitrous oxide decreases pain on injection of propofol mixed with lidocaine

PURPOSE

To investigate if 50% nitrous oxide reduces the pain during injection of propofol mixed with lidocaine in children.

METHODS

Healthy children undergoing iv induction of general anesthesia for elective surgery were recruited into this prospective, randomized, double-blind study. None of the patients received any premedication except for eutectic mixture of local anesthetics cream. Before induction of anesthesia with propofol 1% mixed with lidocaine 0.05% (propofol dose 3 mg x kg(-1)), the treatment group received 50% N(2)O in O(2) and the control group received 100% oxygen. Pain due to propofol administration was rated with a four-point behavioural scale: none, mild, moderate or severe.

RESULTS

There were 28 subjects in the control group and 26 subjects in the treatment group. Demographic data were similar in both groups. The incidence of pain at induction was 4% after N(2)O and 36% in the control group, P < 0.01. No patients had severe pain. Most patients had mild pain. Three of the ten patients with pain in the control group had moderate pain. The number needed to treat was 3:1.

CONCLUSION

Nitrous oxide reduces pain during induction with propofol mixed with lidocaine in healthy children.

Epidural anesthesia with lidocaine reduces propofol injection pain

PURPOSE

To determine whether epidural lidocaine reduces the severity of propofol injection pain compared with iv lidocaine.

METHODS

A prospective, randomized double-blind clinical study was conducted in 120 female patients scheduled for elective gynecological laparotomy. A lumbar epidural catheter and an iv catheter placed in the cephalic vein of the non-dominant hand were used in all patients. Patients of the control group (Group C) were given epidural normal saline followed by iv normal saline then iv propofol. Patients of Group E were given epidural 2% lidocaine (0.08 mL.cm(-1)) followed by iv normal saline and then propofol. Patients of Group V were given epidural normal saline followed by iv 2% lidocaine (0.05 mL.kg(-1)) then propofol. Pain was scored as no pain=0, minimal pain=1, moderate pain=2, severe pain=3.

RESULTS

The pain scores, in group E; 1 (0-2) and group V; 2 (0-2), were significantly lower than in group C; 2 (1-3); median (25th-75th percentile) (P <0.001). There was no difference in pain score between groups E and V The plasma lidocaine concentration 15 min after epidural lidocaine was 2.74 +/- 0.54 microg.ml(-1), compared with 1.54 +/- 0.31 microg.mL(-1) at three minutes after iv lidocaine.

CONCLUSION

Epidural and iv lidocaine equally reduced the severity of propofol injection pain despite higher lidocaine plasma concentrations in epidurally administered lidocaine.

Primate anesthesia

This article provides an update on some of the recent advances in primate anesthesia. It focuses in particular on some of the newest information available regarding the effects of opioids and alpha-2 agonists in primates, and how these effects are different from what we might expect in other companion animals. It reviews the important properties of the latest induction and inhalation agents, and stresses the need for continuous monitoring of the anesthetized patient.