Esmolol Potentiates Reduction of Minimum Alveolar Isoflurane Concentration by Alfentanil

Effect of esmolol and lidocaine on agitation in awake phase of anesthesia among children: a double-blind, randomized clinical study

Background:

Sevoflurane is widely used to anesthetize children because of its rapid action with minimal irritation of the airways. However, there is a high risk of agitation after emergence from anesthesia. Strabismus surgery, in particular, can trigger agitation because patients have their eyes covered in the postoperative period. The aim of this study was to determine whether or not esmolol and lidocaine could decrease emergence agitation in children.

Methods:

Eighty-four patients aged 3 to 9 years undergoing strabismus surgery were randomly assigned to a control group (saline only), a group that received intravenous lidocaine 1.5 mg/kg, and a group that received intravenous esmolol 0.5 mg/kg and lidocaine 1.5 mg/kg. Agitation was measured using the objective pain score, Cole 5-point score, and Richmond Agitation Sedation Scale score at the end of surgery, on arrival in the recovery room, and 10 and 30 min after arrival.

Results:

The group that received the combination of esmolol and lidocaine showed lower OPS and RASS scores than the other two groups when patients awoke from anesthesia (OPS = 0 (0–4), RASS = –4 [(–5)–1]) and were transferred to the recovery room (OPS = 0 (0–8), RASS = –1 [(–5)–3]) (P < 0.05). There was no significant difference in the severity of agitation among the three groups at other time points (P > 0.05).

Conclusions:

When pediatric strabismus surgery is accompanied by sevoflurane anesthesia, an intravenous injection of esmolol and lidocaine could alleviate agitation until arrival in the recovery room.

Trial registration:

Clinical Research Information Service, No. KCT0002925; https://cris.nih.go.kr/cris/en/search/search_result_st01.jsp?seq=11532

Effect of Continuous Systemic Administration of Esmolol on Intraocular Pressure During Surgery in a Sustained Steep Trendelenburg Position

PURPOSE

To investigate the effects of continuous systemic administration of esmolol on intraocular pressure (IOP) during laparoscopic and robotic surgeries for recto-sigmoid cancer in a steep Trendelenburg position.

MATERIALS AND METHODS

A total of 50 patients undergoing laparoscopic surgery in a steep Trendelenburg position were included. Patients in the esmolol (E) group received a 0.25 mg/kg IV loading dose of esmolol before anesthesia, followed by an infusion of 15 μg/kg/min throughout the operation. Patients in the saline (S) group were infused with the same volume of normal saline. IOP and ocular perfusion pressure were measured 16 times: before anesthetic induction (T1), before administration of the study drug (T2), after administration of anesthetic induction agents (T3), after tracheal intubation (T4), 1, 3, 5, and 10 minutes after tracheal intubation (T5-T8), immediately after intraperitoneal CO2 insufflation (T9), immediately after the steep Trendelenburg position (T10), 1, 2, and 4 hours after the steep Trendelenburg position (T11-T13), just before the supine position (T14), and 10 and 30 minutes after the supine position (T15, T16).

RESULTS

The IOP increased markedly after adopting the steep Trendelenburg position, reaching 28.8±4.4 mm Hg in group S. The IOP at T13 in group S was ∼5.7 mm Hg higher than in group E. The IOP at T13 was ∼10.6 mm Hg higher than in T1 in group S, but only ∼4.4 mm Hg higher than in group E.

CONCLUSIONS

Continuous systemic administration of esmolol can alleviate the increase in IOP during a sustained steep Trendelenburg position without adverse cardiovascular effects.

The effect of esmolol compared to opioids on postoperative nausea and vomiting, postanesthesia care unit discharge time, and analgesia in noncardiac surgery: A meta-analysis

Background and Aims:

Perioperative esmolol as an opioid alternative has been shown to reduce postoperative nausea vomiting using opioid sparing. The aim of this meta-analysis was to compare esmolol and opioids on postoperative nausea and vomiting (PONV), time spent in recovery, and analgesia in noncardiac surgeries.

Material and Methods:

OVID Medline (1980–February 2014), OVID EMBASE, EBSCO, CINAHL, and the Cochrane Register of Controlled Trials were searched for randomized controlled trials (RCTs) comparing esmolol and opioids on early postoperative recovery and pain intensity during general anesthesia in noncardiac surgeries. The primary outcomes were related to PONV and postanesthesia care unit (PACU) discharge time, whereas secondary outcomes were related to early postoperative pain.

Results:

Eight trials were identified involving 439 patients, 228 of whom received esmolol while 211 received opioids. A random-effects meta-analysis showed that in comparison with opioids, esmolol led to a 69% reduction in the incidence of PONV (odds ratio 0.31, 95% confidence interval [CI] 0.13–0.74, P = 0.008, I² = 44.1%). An increase in the volatile anesthetic requirement was evident in the esmolol group compared with opioid (MD + 0.67% desflurane equivalent, 95% CI 0.27–1.08, P = 0.001, I² =23.5%). There was no statistically significant difference between the esmolol and opioid groups in relation to PACU discharge time, early postoperative pain scores, opioid requirement, and cumulative opioid consumption. Significant heterogeneity was noted between studies. No significant adverse effects were noted.

Conclusion:

Compared with opioids, perioperative esmolol may reduce the incidence of postoperative nausea vomiting and increase the volatile anesthetic requirement. Esmolol administration may not improve the early postoperaive pain intensity. Nonetheless, these findings are limited by the absence of high-quality RCTs and the heterogeneity among studies. Further, large-scale studies are needed to explore these results.

Comparative evaluation of the effect of remifentanil and 2 different doses of esmolol on pain during propofol injection: A double-blind, randomized clinical consort study

BACKGROUND

Propofol is associated with pain during injection, which is stressful to patients. The present study was designed to investigate the analgesic effect of pretreatment with remifentanil and esmolol in minimizing propofol injection pain, compared with placebo.

METHODS

In a randomized, double-blind, prospective trial, 120 patients, scheduled for elective dental surgery under general anesthesia, were randomized to 1 of the 4 treatment arms (n = 30 each) receiving normal saline, remifentanil 0.35 μg/kg, esmolol 0.5 mg/kg, and 1 mg/kg before administration of propofol. During injection of 1% propofol 0.5 mg/kg, pain was evaluated by a 4-point score (0 = none, 1 = mild, 2 = moderate, 3 = severe). Any adverse effects such as hypotension and bradycardia were recorded during the perioperative periods.

RESULTS

In all, 120 patients completed this study. There were no significant differences in terms of demographic data. The incidence of pain on injection of propofol was 11 (36.7%) with remifentanil 0.35 μg/kg, 12 (40%) with esmolol 0.5 mg/kg, and 11 (36.7%) with esmolol 1 mg/kg, compared with 25 (83.3%) with normal saline (respectively, P < 0.05). There were no significant differences in the incidence of pain between groups with remifentanil 0.35 μg/kg, and esmolol 0.5 mg/kg and 1 mg/kg. There were no emergence reactions such as hypotension and bradycardia in all groups.

CONCLUSIONS

Pretreatment with esmolol 0.5 mg/kg and 1 mg/kg and remifentanil 0.35 μg/kg equally decreased pain during propofol injection.

The effect of perioperative esmolol on early postoperative pain: A systematic review and meta-analysis

Esmolol has been shown to improve postoperative pain and reduce opioid requirements. The aim of this systematic review was to evaluate the effect of perioperative esmolol as an adjunct on early postoperative pain intensity, recovery profile, and anesthetic requirement. Databases were searched for randomized placebo-controlled trials evaluating the effects of esmolol during general anesthesia. Primary outcomes were related to early postoperative pain whereas secondary outcomes were related to emergence time, postoperative nausea and vomiting, and intraoperative anesthetic requirement. Nineteen trials were identified involving 936 patients (esmolol = 470, placebo = 466). In esmolol group, numeric pain scores at rest in the immediate postoperative period were reduced by 1.16 (95% confidence interval [CI]: 1.97–0.35, I² = 96.7%) out of 10. Opioid consumption was also decreased in the postanesthesia care unit compared with placebo, mean difference of 5.1 mg (95% CI: 7.0–3.2, I² = 96.9%) morphine IV equivalents; a 69% reduction in opioid rescue dosing was noted (odds ratio [OR]: 0.31, 95% CI: 0.16–0.80, I² = 0.0%). A 61% reduction in postoperative nausea and vomiting was also evident (OR: 0.39, 95% CI: 0.20–0.75, I² = 60.7%). A reduction in propofol induction dose was noted in the esmolol group (mean difference: −0.53 mg/kg, 95% CI: −0.63–−0.44, I² = 0.0%). A decrease in end-tidal desflurane equivalent (mean difference: 1.70%, 95% CI: −2.39–−1.02, I² = 92.0%) and intraoperative opioid usage (fentanyl equivalent, mean difference: 440 μg, 95% CI: −637–−244, I² = 99.6%) was observed in esmolol group. Esmolol had no effect on the emergence time. Perioperative esmolol as an adjunct may reduce postoperative pain intensity, opioid consumption, and postoperative nausea vomiting. Given the heterogeneity, larger clinical trials are warranted to confirm these findings.

Best practice in the administration of analgesia in postoncological surgery

The rationale for using multimodal analgesia after any major surgery is achievement of adequate analgesia while avoiding the unwanted effects of large doses of any analgesic, in particular opioids. There are two reasons why we can hypothesize that multimodal analgesia might have a significant impact on cancer-related outcomes in the context of oncological orthopedic surgery. First, because multimodal analgesia is a key component of enhanced-recovery pathways and can accelerate return to intended oncological therapy. And second, because some of the analgesic used in multimodal analgesia (i.e., COX inhibitors, local analgesics and dexamethasone) can induce apoptosis in cancer cells and/or diminish the inflammatory response during surgery which itself can facilitate tumor growth.

[The effect of different doses of esmolol on hemodynamic, bispectral index and movement response during orotracheal intubation: prospective, randomized, double-blind study]

OBJECTIVE

A prospective, randomized and double-blind study was planned to identify the optimum dose of esmolol infusion to suppress the increase in bispectral index values and the movement and hemodynamic responses to tracheal intubation.

MATERIALS AND METHODS

120 patients were randomly allocated to one of three groups in a double-blind fashion. 2.5mgkg(-1) propofol was administered for anesthesia induction. After loss of consciousness, and before administration of 0.6mgkg(-1) rocuronium, a tourniquet was applied to one arm and inflated to 50mmHg greater than systolic pressure. The patients were divided into 3 groups; 1mgkg(-1)h(-1) esmolol was given as the loading dose and in Group Es50 50μgkg(-1)min(-1), in Group Es150 150μgkg(-1)min(-1), and in Group Es250 250μgkg(-1)min(-1) esmolol infusion was started. Five minutes after the esmolol has been begun, the trachea was intubated; gross movement within the first minute after orotracheal intubation was recorded.

RESULTS

Incidence of movement response and the ΔBIS max values were comparable in Group Es250 and Group Es150, but these values were significantly higher in Group Es50 than in the other two groups. In all three groups in the 1st minute after tracheal intubation heart rate and mean arterial pressure were significantly higher compared to values from before intubation (p<0.05). In the study period there was no significant difference between the groups in terms of heart rate and mean arterial pressure.

CONCLUSION

In clinical practise we believe that after 1mgkg(-1) loading dose, 150μgkg(-1)min(-1) iv esmolol dose is sufficient to suppress responses to tracheal intubation without increasing side effects.

[Intraoperative esmolol infusion reduces postoperative analgesic consumption and anaesthetic use during septorhinoplasty: a randomized trial]

BACKGROUND AND OBJECTIVES

Esmolol is known to have no analgesic activity and no anaesthetic properties; however, it could potentiate the reduction in anaesthetic requirements and reduce postoperative analgesic use. The objective of this study is to evaluate the effect of intravenous esmolol infusion on intraoperative and postoperative analgesic consumptions as well as its effect on depth of anaesthesia.

METHOD

This randomized-controlled double blind study was conducted in a tertiary care hospital between March and June 2010. Sixty patients undergoing septorhinoplasty were randomized into two groups. History of allergy to drugs used in the study, ischaemic heart disease, heart block, bronchial asthma, hepatic or renal dysfunction, obesity and a history of chronic use of analgesic or β-blockers were considered cause for exclusion from the study. Thirty patients received esmolol and remifentanil (esmolol group) and 30 patients received normal saline and remifentanil (control group) as an intravenous infusion during the procedure. Mean arterial pressure, heart rate, and bispectral index values were recorded every 10min. Total remifentanil consumption, visual analogue scale scores, time to first analgesia and total postoperative morphine consumption were recorded.

RESULTS

The total remifentanil consumption, visual analogue scale scores at 0, 20 and 60min, total morphine consumption, time to first analgesia and the number of patients who needed an intravenous morphine were lower in the esmolol group.

CONCLUSIONS

Intravenous infusion of esmolol reduced the intraoperative and postoperative analgesic consumption, reduced visual analogue scale scores in the early postoperative period and prolonged the time to first analgesia; however it did not influence the depth of anaesthesia.

Influence of esmolol on requirement of inhalational agent using entropy and assessment of its effect on immediate postoperative pain score

Background and Context:

Beta-blockers have been used for attenuation of stress response, decreasing anaesthetic requirement and augmentation of the effect of opioids during general anaesthesia.

Aims and Objectives:

The present study aims to evaluate the influence of esmolol on the requirement of an inhalational agent while monitoring the depth of anaesthesia by entropy and also its effect on immediate postoperative pain score.

Methods:

Fifty American Society of Anaesthesiologists (ASA) I and II patients, between 25 and 65 years of age who underwent lower abdominal surgeries were randomly allocated to two groups: Group E and Group S of 25 patients each. Group E received esmolol infusion while Group S received the same volume of saline infusion. Demographic data, haemodynamics, amount of isoflurane used, end-tidal isoflurane concentration, postoperative pain score and total dose of morphine consumed in immediate postoperative period of 30 min were analyzed by using appropriate statistical tests. Value of P<0.05 was considered significant and P<0.001 as highly significant.

Results:

The two groups were comparable with respect to age, weight, ASA physical status, duration of surgery and amount of isoflurane used during anaesthesia. Assessment of postoperative pain was assessed by Visual Analogue Scale (VAS) which showed significant difference at 30 min. The total dose of morphine consumption was significantly less (P<0.05) in Group E for relief of postoperative pain.

Conclusions:

We conclude that in light of depth of anaesthesia monitor esmolol has no effect on requirement of isoflurane, but it decreases the postoperative pain as well as postoperative requirement of morphine without increasing the risk of awareness.

Efficacy of intrathecal esmolol on heat-evoked responses in a postoperative pain model

Perioperative tachycardia and hypertension are often treated with esmolol, a short-acting β1-adrenoceptor antagonist. Besides its cardiac effect, esmolol is reported to exert antinociceptive effects. This study examined the efficacy of intrathecal (IT) esmolol on pain responses in a postoperative pain model. Male Sprague-Dawley rats (250-300 g) were anesthetized with sevoflurane and an IT catheter was implanted. Six days after catheter implantation, a postoperative pain model was established by plantar incision under sevoflurane anesthesia. Withdrawal latencies were assessed by applying a focused radiant heat source before plantar incision; 1 day after the incision (before esmolol administration); and 5, 10, and 15 minutes after bolus administration of IT esmolol. Plantar incision produced hypersensitivity in the postoperative pain model expressed as decreased withdrawal latency to heat stimulation (before incision: 13.9 ± 0.29 seconds and 1 day after incision: 6.3 ± 0.26 seconds). These decreased latencies caused by incision were significantly increased by esmolol administration (40 μg, 80 μg) at 5 minutes (10.7 ± 1.16 seconds, 10.5 ± 1.16 seconds). No postoperative antinociceptive effects of esmolol were observed at 10 or 15 minutes. IT administration of esmolol produced antinociceptive effects of short duration in a rat postoperative pain model. These results suggest that IT esmolol could offer a new strategy for managing perioperative pain, although an alternative approach is necessary to lengthen the duration of the analgesia.

Esmolol versus ketamine-remifentanil combination for early postoperative analgesia after laparoscopic cholecystectomy: a randomized controlled trial

PURPOSE

Controversy surrounds the optimal technique to moderate pain after laparoscopic cholecystectomy (LC). Opioid analgesics, sympatholytic drugs, and adjuvants, such as ketamine, have all been used. We compared esmolol with a combination of remifentanil plus ketamine in patients undergoing LC to determine the impact of these drugs on morphine requirements and pain control.

METHODS

Sixty American Society of Anesthesiologists physical status I-II patients undergoing LC and anesthetized with sevoflurane were randomized to one of two groups. Group E patients received a bolus of esmolol 0.5 mg·kg(-1) iv at induction followed by an infusion of 5-15 μg·kg(-1)·min(-1), and Group R-K patients received a bolus of ketamine 0.5 mg·kg(-1) iv and remifentanil 0.5 μg·kg(-1) iv at induction followed by a remifentanil infusion titrated over a range of 0.1-0.5 μg·kg(-1)·min(-1). All patients received paracetamol, dexketoprofen, and levobupivacaine via infiltration of laparoscopic port sites. After surgery, a predetermined bolus of morphine was administered according to a verbal numerical rating scale (VNRS) for pain intensity. The primary outcome of interest was postoperative morphine requirement.

RESULTS

Median consumption of morphine was higher in Group R-K than in Group E (5 mg [4-6] vs 0 mg [0-2], respectively; P < 0.001). In the postanesthesia care unit, patients in Group R-K had higher pain scores than patients in Group E (difference in maximum VNRS, -11; 95% confidence interval (CI), -19 to -3). The concentration of sevoflurane to maintain a bispectral index~40 was higher in Group E than in Group R-K (between-group difference 0.3%; 95% CI, 0.15 to 0.40). The incidence of postoperative nausea and vomiting was similar between the two groups.

CONCLUSION

Intraoperative esmolol infusion reduces morphine requirements and provides more effective analgesia compared with a combination of remifentanil-ketamine given by infusion in patients undergoing LC.

Intravenous landiolol, a novel β(1)-adrenergic blocker, reduces the minimum alveolar concentration of sevoflurane in women

STUDY OBJECTIVE

To investigate the effect of intravenous (IV) landiolol, a novel β(1)-adrenergic blocker, on the minimum alveolar concentration (MAC) of sevoflurane in adult women.

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PATIENTS

42 ASA physical status 1 and 2 women, aged 24-57 years, who were scheduled to undergo elective abdominal surgery.

INTERVENTIONS

Anesthesia was induced in all patients by vital capacity rapid inhalation induction of sevoflurane. In the landiolol group, administration of landiolol began when patients took a vital-capacity breath: 0.125 mg/kg/min for one minute and then 0.04 mg/kg/min. Normal saline was administered in the control group.

MEASUREMENTS

MAC was determined by a technique adapted from the conventional up-down method.

MAIN RESULTS

The MAC of sevoflurane was 2.2% ± 0.2% in the control group and 1.7% ± 0.2% in the landiolol group, a statistically significant difference (P = 0.0005).

CONCLUSIONS

IV landiolol reduces the MAC of sevoflurane in women by approximately 20%.

The Sparing Effect of Low-Dose Esmolol on Sevoflurane during Laparoscopic Gynaecological Surgery

This double-blind, randomized, placebocontrolled study evaluated the sparing effect of esmolol on sevoflurane during laparoscopic gynaecological surgery in 54 patients between December 2009 and May 2010. The concentration of sevoflurane required to maintain adequate anaesthesia was determined. Patients received either a 0.5 mg/kg esmolol intravenous loading dose followed by infusion of 30 μg/kg per min or an identical volume of normal saline (placebo). During surgery the input concentration of sevoflurane was adjusted every 5 min to maintain systolic blood pressure within 15% of baseline and bispectral index at 50–60. Infusion of esmolol resulted in an 18.2% decrease in mean sevoflurane input concentration. Patients receiving esmolol had an earlier discharge from the postanaesthetic care unit and a lower mean fentanyl dose. In conclusion, intraoperative esmolol infusion decreased both the requirement for sevoflurane and postoperative administration of fentanyl.

Esmolol modulates inhibitory neurotransmission in the substantia gelatinosa of the spinal trigeminal nucleus of the rat

Background

β₁-adrenaline receptor antagonists are often used to avoid circulatory complications during anesthesia in patients with cardiovascular diseases. Of these drugs, esmolol, a short-acting β antagonist, is also reported to exert antinociceptive and anesthetic sparing effects. This study was designed to identify the central mechanism underlying the antinociceptive effect of esmolol.

Methods

Wistar rats (7-21 d, 17-50 g) were anesthetized with ketamine (100-150 mg/kg) or isoflurane (5%) and decapitated. Horizontal slices (400-μm thick) of the lower brainstem containing the substantia gelatinosa (SG) of the caudal part of the spinal trigeminal nucleus (Sp5c), in which the nociceptive primary afferents form the first intracranial synapses, were made with a vibrating slicer. The miniature inhibitory and excitatory postsynaptic currents (mIPSCs and mEPSCs, respectively) were simultaneously recorded from visually identified SG neurons of the Sp5c in the presence of tetrodotoxin (1 μM). Additionally, mIPSCs were recorded during pharmacological isolation of GABA- and glycine-mediated mIPSCs with kynurenic acid (1 mM).

Results

Esmolol (500 μM) significantly and selectively increased the mIPSC frequency (to 214.2% ± 34.2% of the control, mean ± SEM, n = 35; P < 0.001), but not that of mEPSCs, without changing their amplitude. The increase in mIPSC frequency with esmolol was not affected by prior activation of β receptors with isoproterenol (100 μM) but it was significantly attenuated by removal of extracellular Ca²⁺.

Conclusions

These data suggest that esmolol modulates inhibitory transmitter release in the Sp5c through a mechanism involving Ca²⁺-entry but in a β₁-adrenoceptor-independent manner. The present results suggest that the facilitation of inhibitory transmitter release in the central nociceptive network underlies, at least in part, the antinociceptive effect of esmolol.

Landiolol, a new ultra-short-acting beta1-blocker, reduces anaesthetic requirement during sevoflurane/N(2)O/fentanyl anaesthesia in surgical patients

BACKGROUND AND OBJECTIVE

It is known that esmolol, a short-acting beta1-blocker, reduces anaesthetic requirement. In this study, we evaluated whether a low dose of landiolol, a new ultra-short-acting beta1-blocker, can reduce the sevoflurane requirement.

METHODS

Twenty-five patients undergoing hip surgery were randomly divided into two groups. Group A (n = 13) received landiolol (bolus injection of 0.031 mg.kg(-1) and continuous infusion at a rate of 0.01 mg.kg(-1).min(-1)). Group B (n = 12) received physiological saline. Landiolol and physiological saline were started before the induction of anaesthesia and continued until the end of anaesthesia. Anaesthesia was maintained with sevoflurane, 60% N(2)O and fentanyl. Sevoflurane concentration was controlled to keep the bispectral index at approximately 50. The end-tidal sevoflurane concentration and haemodynamics were measured during anaesthesia.

RESULTS

The average end-tidal sevoflurane concentration in group A was significantly lower than that in group B (1.2 +/- 0.30 vs. 1.8 +/- 0.3%, P < 0.01). Maximum values of systolic arterial pressure showed no difference between the groups, whereas the maximum value of heart rate in group A was significantly less than that in group B (61 +/- 10 vs. 76 +/- 14 beats min(-1), P < 0.05).

CONCLUSION

The results suggest that a low dose of landiolol significantly reduces the intraoperative sevoflurane requirement during sevoflurane/N(2)O/fentanyl anaesthesia in patients undergoing hip surgery.

Comparative effects of ultra-short-acting beta1-blockers on voltage-gated tetrodotoxin-resistant Na+ channels in rat sensory neurons

BACKGROUND AND OBJECTIVE

To examine a possible mechanism for their antinociceptive actions, we compared the effects of two clinically used ultra-short-acting beta1-blockers, landiolol and esmolol, on tetrodotoxin-resistant sodium (TTX-r Na) channels in rat dorsal root ganglion neurons, which are important for nociception.

METHODS

In small (<30 microm) dorsal root ganglion neurons from Sprague-Dawley rats, recordings of whole-cell membrane currents were made using the patch-clamp technique. To examine the effects of landiolol and esmolol on TTX-r Na currents, whole-cell membrane Na currents were evoked every 10 s by stepping for 50 ms from a holding potential of -70 to -10 mV. Each drug was applied at stepwise-increased concentrations every 2 min. The voltage dependence of the steady-state inactivation of the TTX-r Na current was investigated by using a conventional double-pulse protocol. To test for use-dependent blockade of TTX-r Na channels by beta-blockers, trains of depolarizing pulses (to -10 from a holding potential of -70 mV) were applied at one of three frequencies (0.2, 5 or 20 Hz) in the absence or presence of drug (landiolol 8 mmol l, esmolol 140 micromol l).

RESULTS

Esmolol blocked TTX-r Na currents in a dose-dependent and use-dependent manner, but a very high concentration of landiolol was required to block TTX-r Na channel activities. The half-maximal inhibitory concentrations (IC50) for the TTX-r Na current were (holding potential, -70 mV) landiolol 7.66 +/- 0.62 mmol l (n = 6) and esmolol 145 +/- 7.5 micromol l (n = 6), and the Hill coefficients were landiolol 1.06 +/- 0.09 (n = 6) and esmolol 0.96 +/- 0.05 (n = 6).

CONCLUSION

Esmolol, but not landiolol, may have useful effects against pain related to TTX-r Na channel activity.

Lipophilic beta-adrenoceptor antagonist propranolol increases the hypnotic and anti-nociceptive effects of isoflurane in a swine model

BACKGROUND

We have previously reported that landiolol, an ultra-short-acting beta1-adrenoceptor antagonist, does not alter the anaesthetic effects of isoflurane. Here, we investigated the influence of propranolol on the electroencephalographic (EEG) effects and minimum alveolar concentration (MAC) of isoflurane.

METHODS

Fourteen swine [25.0 (SD 4.0) kg] were anaesthetized by isoflurane inhalation. The inhalation concentration was decreased to 0.5% and maintained for 25 min, before being returned to 2%, and maintained for a further 25 min. End-tidal isoflurane concentrations and spectral edge frequencies were recorded. Pharmacodynamic analysis was performed using a sigmoidal inhibitory maximal effect model for spectral edge frequency vs effect-site concentration. After measurement of the EEG effect, MAC was determined using the dew-claw clamp technique, in which movement in response to clamping is recorded. After completion of control measurements, a propranolol 4 mg bolus followed by an infusion (2 mg h(-1)) was started. After a 30 min stabilization period, the inhalation concentration of isoflurane was varied as in the control period and MAC was re-assessed.

RESULTS

Propranolol shifted the concentration-effect relationship to the left and decreased the effect-site concentration that produced 50% of the maximal effect from 1.30 (0.18) to 1.13 (0.17)%. Propranolol also decreased isoflurane MAC from 1.91 (0.35) to 1.54 (0.32)%.

CONCLUSIONS

Propranolol alters both the hypnotic and anti-nociceptive effects of isoflurane. In contrast to landiolol, lipophilic beta-adrenoceptor antagonists may increase the potency of inhalational anaesthetics.

Intrathecal landiolol inhibits nociception and spinal c-Fos expression in the mouse formalin test

PURPOSE

The purpose of this study was to determine if intrathecal landiolol, a beta1-blocker, can modulate formalin-induced nociception and spinal c-Fos expression in mice, in the absence of anesthesia.

METHODS

Thirty-two mice were randomly assigned to one of four groups: the control group (n = 8) received intrathecal normal saline 10 microL, while the other three groups (n = 8 for each) received intrathecal landiolol at escalating doses of 250 microg.kg(-1), 500 microg.kg(-1) and 750 microg.kg(-1) respectively, immediately after induction of anesthesia with isoflurane. After awakening, inflammatory pain was induced by 10 microL of 5% formalin solution injected into the dorsal surface of the right hind paw. The nociceptive behaviours including licking, biting and lifting of the injected paw were cumulatively recorded as seconds of behaviours/min during phase I (0-10 min) and phase II (10-45 min). The c-Fos protein expressions in the spinal dorsal horn were detected with immunohistochemical techniques in the control and landiolol 750 microg.kg(-1) groups.

RESULTS

Compared to the control group, intrathecal injection of landiolol 750 microg.kg(-1) significantly decreased pain-related behaviours in phase I, while intrathecal landiolol 250 microg.kg(-1), 500 microg.kg(-1) and 750 microg.kg(-1) significantly decreased pain-related behaviours in phase II during the formalin test. The numbers of c-Fos immunoreactive nuclei in the L5 spinal dorsal horn were significantly lower in the landiolol 750 microg.kg(-1) group compared to the control group (landiolol 750 microg.kg(-1) 2.4 +/- 1.1 vs control 9.2 +/- 3.9; P < 0.01).

CONCLUSION

The present study indicates that intrathecally administered landiolol produces significant antinociceptive effects in the formalin test. Although further studies exploring the detailed mechanism are needed, these data suggest a potential role of beta1-adrenoreceptors in spinal nociceptive processing.

Atenolol may not modify anesthetic depth indicators in elderly patients--a second look at the data

PURPOSE

Decreased cardiac chronotropic response in elderly patients along with concomitant ss-blockade may suppress the autonomic responsiveness to surgical stimulation and subsequently obscure episodes of "light anesthesia".

METHODS

We analyzed post hoc computerized data from our previous study evaluating the effects of perioperative atenolol administration. Bispectral index (BIS) and the performance of routine anesthetic depth indicators were analyzed in 45 patients undergoing abdominal surgery: Group I (n = 12), isoflurane/fentanyl/nitrous oxide in oxygen anesthesia; Group II (n = 16), isoflurane/fentanyl/nitrous oxide in oxygen with 10 mg atenolol intravenously prior to anesthesia; Group III (n = 17), isoflurane/fentanyl/nitrous oxide in oxygen with a maximum end-tidal isoflurane concentration of 0.4 vol.% and incremental doses of atenolol (5 mg intravenously stepwise). In all groups, blood pressure (BP) was maintained within +/- 20% of preoperatively defined baseline BP and heart rate (HR) between 50-80 beats x min(-1). BP, HR, and end-tidal isoflurane were tested for their potential to predict BIS using a previously described statistical model (P(K)).

RESULTS

Although Group III patients received on average 39.5% less isoflurane compared with Group I patients (P = 0.006), and Groups II and III patients received on average 21% less fentanyl compared with Group I patients (P </= 0.002), similar levels of intraoperative average BIS values (53-54) were obtained for all groups. Higher BIS values were reached at emergence in atenolol-treated patients. The performance of hemodynamic variables or end-tidal isoflurane to predict BIS was moderate even at critical intraoperative events, but unaffected by atenolol.

CONCLUSION

Atenolol reduces anesthetic requirements but may not modify anesthetic depth indicators in elderly patients.

Esmolol promotes electroencephalographic burst suppression during propofol/alfentanil anesthesia

This study examined the effects of an esmolol infusion on the electroencephalogram during propofol/alfentanil IV anesthesia. After informed consent, 20 patients were randomly assigned into four groups on the basis of two target alfentanil concentrations (alfentanil 50 or 150 ng/mL) and of a saline or esmolol infusion. Bispectral index (BIS), burst suppression ratio (SR), and physiologic variables were continuously monitored. A 30-min blinded infusion of saline or esmolol was started after establishing a stable baseline and followed by a washout period. The electroencephalogram was significantly suppressed by esmolol (BIS, 37 +/- 6 to 22 +/- 6, 40% decrease [mean +/- SD]; SR, 5 +/- 7 to 67 +/- 23, 13.4-fold increase) compared with baseline in the small-dose alfentanil groups. Discontinuation of esmolol reversed the response. BIS and SR were unaffected by placebo infusion. Twelve-minute to 16-min hysteresis between esmolol administration and the onset of half-maximal cortical suppression was observed. Physiologic variables and serum propofol and alfentanil concentrations were not significantly altered by esmolol. Although the mechanism remains unclear, significant cortical depression and the onset of burst suppression during a stable, computer-controlled propofol/alfentanil anesthetic was associated with esmolol infusion.

IMPLICATIONS

This study demonstrated the suppression of cerebral cortical electrical activity after blinded esmolol infusion during propofol/alfentanil anesthesia. A significant lag was noted between infusion and half-maximal effect (12-16 min). Whether esmolol, a metabolite, or a secondary process was responsible for this cortical suppression remains unknown and requires further study.