Dexmedetomidine premedication before intravenous regional anesthesia in minor outpatient hand surgery

Effect of real-time binaural music on sedation with dexmedetomidine during spinal anesthesia: A triple-arm, assessor-blind, randomized controlled trial

STUDY OBJECTIVE

Binaural audio induces sedation and reduces pain and anxiety in surgical patients. This study tested the hypothesis that dexmedetomidine requirement for adequate sedation during spinal anesthesia would be lower in patients listening to music with binaural sound than that in patients listening to plain or no music.

DESIGN

A triple-arm, assessor-blind, randomized controlled study.

SETTING

Operating room.

PATIENTS

One hundred and eighty-nine patients undergoing orthopedic surgery under spinal anesthesia.

INTERVENTIONS

Patients were randomly assigned to music with binaural sound, plain music, or no music groups. Dexmedetomidine was infused for sedation during surgery. The loading infusion rate was 6 μg/kg predicted body weight (PBW)/h, followed by continuous infusion at 0.6 μg/kg PBW/hr. Loading was stopped after achieving adequate sedation, defined as the Observer's Assessment of Alertness/Sedation (OAA/S) scale score of 3. Infusion rate was adjusted every 30 min per the OAA/S scale.

MEASUREMENTS

Primary outcomes were the difference in the dexmedetomidine loading dose adjusted for the patient's PBW between (1) the binaural and plain music groups and (2) the binaural and control groups. Secondary outcomes were the total dose and total loading time of dexmedetomidine; Patient State Index; relative powers of the alpha, theta, and delta bands; recovery from sedation; and patient satisfaction score.

MAIN RESULTS

The final analyses included 184 patients. The PBW-adjusted dexmedetomidine loading dose was significantly lower in patients listening to music with binaural sound (1.15 ± 0.30 μg/kg PBW) than that in patients without music (1.33 ± 0.33 μg/kg PBW; mean difference, 0.18 μg/kg PBW; 95% confidence interval [CI], 0.06 to 0.29; P = 0.002). However, the difference was not statistically significant when compared with the plain music group (1.26 ± 0.36 μg/kg PBW; mean difference, 0.11 μg/kg PBW; 95% CI, -0.01 to 0.23; P = 0.070). Dexmedetomidine total dose, recovery from sedation, and patient satisfaction score showed no difference among the three groups.

CONCLUSIONS

Compared with no music, music with binaural sound reduced the dexmedetomidine loading dose; however, this sedative-sparing effect of binaural sound was not found when compared to plain music.

Pharmacokinetics and Pharmacodynamics of 3 Doses of Oral-Mucosal Dexmedetomidine Gel for Sedative Premedication in Women Undergoing Modified Radical Mastectomy for Breast Cancer

BACKGROUND

Buccal dexmedetomidine (DEX) produces adequate preoperative sedation and anxiolysis when used as a premedication. Formulating the drug as a gel decreases oral losses and improves the absorption of buccal DEX. We compared pharmacokinetic and pharmacodynamic properties of 3 doses of buccal DEX gel formulated in our pharmaceutical laboratory for sedative premedication in women undergoing modified radical mastectomy for breast cancer.

METHODS

Thirty-six patients enrolled in 3 groups (n = 12) to receive buccal DEX gel 30 minutes before surgery at 0.5 µg/kg (DEX 0.5 group), 0.75 µg/kg (DEX 0.75 group), or 1 µg/kg (DEX 1 group). Assessments included plasma concentrations of DEX, and pharmacokinetic variables calculated with noncompartmental methods, sedative, hemodynamic and analgesic effects, and adverse effects.

RESULTS

The median time to reach peak serum concentration of DEX (Tmax) was significantly shorter in patients who received 1 µg/kg (60 minutes) compared with those who received 0.5 µg/kg (120 minutes; P = .003) and 0.75 µg/kg (120 minutes; P = .004). The median (first quartile-third quartile) peak concentration of DEX (maximum plasma concentration [Cmax]) in plasma was 0.35 ng/mL (0.31-0.49), 0.37 ng/mL (0.34-0.40), and 0.54 ng/mL (0.45-0.61) in DEX 0.5, DEX 0.75, and DEX 1 groups (P = .082). The 3 doses did not produce preoperative sedation. The 1 µg/kg buccal DEX gel produced early postoperative sedation and lower intraoperative and postoperative heart rate values. Postoperative analgesia was evident in the 3 doses in a dose-dependent manner with no adverse effects.

CONCLUSIONS

Provided that it is administered 60-120 minutes before surgery, sublingual administration of DEX formulated as an oral-mucosal gel may provide a safe and practical means of sedative premedication in adults.

The Effect of Midazolam and Dexmedetomidine Sedation on Block Characteristic Following Spinal Bupivacaine: A Randomized Comparative Study

Background:

Dexmedetomidine is widely used as an adjunct to general as well as regional anesthesia.

Aims:

This study was conducted to compare and evaluate the synergistic effect of single intravenous (i.v.) bolus dose of dexmedetomidine with midazolam on spinal block duration, analgesia, and sedation in patients undergoing infra-umbilical surgeries.

Settings and Design:

Prospective, randomized, comparative, and double-blinded study.

Materials and Methods:

One hundred patients between 18 and 60 years of age of American Society of Anesthesiologists physical status I and II posted for elective infra-umbilical surgery under subarachnoid block were randomly divided into two groups (Group D and Group M). Patients of Group D received i.v. dexmedetomidine 0.5 μg.kg⁻¹ and of Group M received i.v. midazolam 0.05 mg.kg⁻¹ as premedication 5 min before spinal anesthesia over 10 min. Vital parameters, Ramsay sedation score, level of sensory and motor block, recovery time for sensory blockade, postoperative numerical rating scale, time of requirement of the first dose of postoperative rescue analgesic, and duration of analgesia were recorded and analyzed.

Statistical Analysis:

Chi-square test, t-test, and analysis of variance test were applied to analyze data using SPSS package for Windows.

Results and Conclusion:

Premedication with single i.v. dexmedetomidine prolonged the duration and increased the maximum upper level of only sensory component of spinal anesthesia (6.42 ± 3.21 vs. 4.8 ± 1.21 thoracic segments higher than with midazolam sedation). This property can be beneficial in preventing undesirable prolongation of motor block and facilitating early ambulation in shorter duration of infra-umbilical surgeries. In addition, dexmedetomidine slowed the regression of sensory block and increased the time of the first request of analgesic.

Dexmedetomidine Provides Fewer Respiratory Events Compared With Propofol and Fentanyl During Third Molar Surgery: A Randomized Clinical Trial

PURPOSE

Propofol and fentanyl can cause airway obstruction and respiratory depression when used together for intravenous sedation. This study investigated whether dexmedetomidine and midazolam would decrease respiratory events requiring intervention during deep sedation compared with propofol, fentanyl, and midazolam.

PATIENTS AND METHODS

A prospective, randomized, double-blinded, controlled trial was designed to assess 2 intravenous treatment groups during third molar surgery. Patients were randomized into 2 groups. The control group (group P) received 0.8 μg/kg of fentanyl followed by propofol infusion at 125 μg/kg per minute over a 10-minute period with intraoperative boluses of 0.1 μg/kg. The study group (group D) received dexmedetomidine bolus infusion of 1 μg/kg over a 10-minute period followed by maintenance infusion at 0.5 μg/kg per hour. Both groups were given 0.03 mg/kg of midazolam before infusion. Scorers, masked to group, viewed the procedure remotely and evaluated the primary outcome variable of respiratory events requiring intervention. Secondary outcome variables evaluated by the scorers included the Behavioral Pain Scale for non-intubated patients at initial injection, cooperation score at 5 and 15 minutes, and time to ambulation and discharge. Patient satisfaction and hemodynamic stability were measured. The difference between groups regarding the occurrence of respiratory events was tested using the Fisher exact test, and mixed-effects models were used to compare repeated vital signs.

RESULTS

The sample was composed of 141 patients randomly assigned to either group P (n = 67) or group D (n = 74). No statistically significant differences in the distribution of study variables were found between groups at baseline. A statistically significant difference in respiratory events requiring deliberate intervention existed between group P (25.4%) and group D (2.7%) (P < .0001). No statistically significant difference was found between groups for Behavioral Pain Scale score, cooperation score, time to ambulation or discharge, and patient satisfaction.

CONCLUSIONS

Using dexmedetomidine and midazolam for outpatient surgery resulted in fewer respiratory events requiring deliberate intervention compared with propofol, fentanyl, and midazolam. Ambulation and discharge times were not prolonged using dexmedetomidine.

Pharmacological screening of a new alpha-2 adrenergic receptor agonist, mafedine, in zebrafish

Pharmacological agents acting at alpha-2 adrenergic receptors are widely used in physiology and neuroscience research. Mounting evidence of their potential utility in clinical and experimental psychopharmacology, necessitates new models and novel model organisms for their screening. Here, we characterize behavioral effects of mafedine (6-oxo-1-phenyl-2- (phenylamino)-1,6-dihydropyrimidine-4-sodium olate), a novel drug with alpha-2 adrenergic receptor agonistic effects, in adult zebrafish (Danio rerio) in the novel tank test of anxiety and activity. Following an acute 20-min exposure, mafedine at 60 mg/L produced a mild psychostimulant action with some anxiogenic-like effects. Repeated acute 20-min/day administration of mafedine for 7 consecutive days at 1, 5 and 10 mg/L had a similar action on fish behavior as an acute exposure to 60 mg/L. Since mafedine demonstrated robust behavioral effects in zebrafish - a sensitive vertebrate aquatic model, it is likely that it may modulate rodent and human behavior as well. Thus, further studies are needed to explore this possibility in detail, and whether it may foster clinical application of mafedine and related alpha-2 adrenergic agents.

Pain relief after ambulatory surgery: Progress over the last decade

The concept of fast-track or ambulatory surgery appeared to facilitate early recovery and discharge from the hospital and early resumption of normal daily activities after elective surgical procedures as well to reduce the health-care costs. Multimodal/balanced analgesia is an increasingly popular approach for this. The use of conventional modalities including central neuraxial blockade and opioids cannot be extended to patients undergoing fast-track surgery. Hence, an aggressive perioperative analgesic regimen/protocol is required for effective pain relief, with minimal side effects and which could be managed easily by the patient or the relatives at home away from the hospital setting. Pharmacological therapy and regional anesthesia techniques have been utilized for postoperative pain management. The use of perineural, incisional, and intra-articular catheters and local anesthetic administration through elastomeric and electronic pumps is promising approach for effective pain management at home. The key to successful pain management of such procedures requires individually tailored education to patients or caregivers including information on treatment options for postoperative pain and use of multimodal analgesia. This review provides an overview of the current armamentarium of drugs and modalities available for effective management of patients undergoing day care surgeries and sheds light on newer modalities available.

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

INTRODUCTION

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

AIM

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

A Study on the Efficacy of the Addition of Low Dose Dexmedetomidine as an Adjuvant to Lignocaine in Intravenous Regional Anaesthesia (IVRA)

INTRODUCTION

Intravenous Regional Anaesthesia (IVRA) is a simple, effective method of providing anaesthesia for short duration surgical procedures on the extremities, its chief drawbacks are tourniquet pain, short duration of block and absence of post-operative analgesia. Dexmedetomidine is known to reduce anaesthetic requirements and also provide analgesia to the patient.

AIM

To evaluate the efficacy of dexmedetomidine as an adjuvant to lignocaine in IVRA with respect to the quality of the block, tourniquet pain and post-operative analgesia.

MATERIALS AND METHODS

A prospective, randomized, double-blinded study was conducted on 60 patients scheduled for orthopaedic surgery of the upper limb, of American Society of Anaesthesiologist's physical status grades I and II. They were divided into two groups of 30 each. The control group C received 40ml of 0.5% lignocaine with saline and Group D received dexmedetomidine 0.5μg/kg added to 40ml of 0.5% lignocaine. The time taken for the onset and recovery of sensory and motor block, incidence of tourniquet pain, intra-operative and post-operative Visual Analogue Scale (VAS) scores, duration of post-operative analgesia and any side effects were noted. Student t-test was used for evaluation of the demographic data, haemodynamic variables, the onset and recovery times of block, duration of analgesia and intra-operative analgesic consumption and tourniquet pain. Friedman's test was used for intra-operative and post-operative VAS and sedation scores.

RESULTS

The onset time of both sensory and motor block were significantly shortened, the recovery of sensory and motor block was prolonged, the incidence of tourniquet pain was comparatively lesser and there was significantly increased duration of post-operative analgesia in the dexmedetomidine group. Haemodynamic parameters were similar in both groups.

CONCLUSION

The addition of 0.5μg/kg of dexmedetomidine as an adjuvant to IVRA effectively enhances the anaesthesia and post-operative analgesia obtained with lignocaine. The low dose of dexmedetomidine was effective and did not cause any major side effects.

The timing of administration of intravenous dexmedetomidine during lower limb surgery: a randomized controlled trial

Background

Dexmedetomidine, a selective alpha-2 agonist, has sedative, analgesic, and anxiolytic effects without respiratory depression. Dexmedetomidine can cause a biphasic cardiovascular response, and induce transient hypertension. Hypotension is a common complication of spinal anesthesia. Decreasing anxiety of patients before procedure is important for high quality of procedure. This study aimed to compare the incidence of hypotension and patients’ anxiety and comfort levels when dexmedetomidine was intravenously administered before and after spinal anesthesia.

Methods

Seventy-four patients with American Society of Anesthesiologists physical status classification I or II were randomly allocated into two groups. Spinal anesthesia was performed using 12 mg of 0.5% heavy bupivacaine. In Group A, 1 μg/kg of dexmedetomidine was intravenously administered for 10 min, followed by the maintenance infusion of dexmedetomidine 0.2 μg/kg/hr after 5 min of intrathecal bupivacaine injection. Patients in Group B received same dose of dexmedetomidine by intravenous administration before 5 min of intrathecal bupivacaine injection. Perioperative vital signs, anxiety (using the Spielberger’s State-Trait Anxiety Inventory) and comfort (using the numerical rating scale) were evaluated.

Results

The incidence of hypotension was significantly lower in Group A (16.1%) than in Group B (48.4%) during infusion of dexmedetomidine (p = 0.01). The need for treatment of hypotension is higher in Group B than Group A (p = 0.02). The incidence of bradycardia and desaturation did not significantly differ between the two groups. There were no statistically significant differences regarding the patients’ anxiety and comfort.

Conclusions

Hypotension is more frequently occurred, and the treatment of hypotension is more needed in Group B. The intravenously administration of dexmedetomidine before spinal anesthesia has no advantages in hemodynamic status and patients’ comfort compared to that after spinal anesthesia during lower limb surgery.

Trial registration

ClinicalTrials.gov number, NCT02155010. Retrospectively registered on May 22, 2014.

Pharmacokinetics and pharmacodynamics of dexmedetomidine

Dexmedetomidine is an alpha-2 adrenoceptor agonist and has been used as a general anesthetic, sedative and analgesic for about 30 years. The aim of this paper is to review the pharmacokinetics and pharmacodynamics of dexmedetomidine, evaluate physiological factors that may affect the pharmacokinetics of dexmedetomidine, and summarize the pharmacodynamics of dexmedetomidine at different plasma levels. The pharmacokinetic parameters reported in previous studies according to noncompartmental analyses or population modeling results are compared. We concluded that the pharmacokinetic profile can be adequately described by a two-compartment model in population pharmacokinetic modeling. Body weight, height, albumin level, cardiac output, disease condition and other factors were considered to have significant influence on the clearance and/or distribution volume in different population pharmacokinetic models. The pharmacological effects of dexmedetomidine, such as sedation, heart rate reduction and biphasic change of blood pressure, vary at different plasma levels. These findings provide a reference for individualizing the dose of dexmedetomidine and achieving the desired pharmacological effects in clinical applications.

Ultrasound-guided bilateral combined inguinal femoral and subgluteal sciatic nerve blocks for simultaneous bilateral below-knee amputations due to bilateral diabetic foot gangrene unresponsive to peripheral arterial angioplasty and bypass surgery in a coagulopathic patient on antiplatelet therapy with a history of percutaneous coronary intervention for ischemic heart disease: A case report

BACKGROUND

Patients on antiplatelet therapy following percutaneous coronary intervention can become coagulopathic due to infection. Performing regional anesthesia for bilateral surgery in such cases is challenging. We report a case of successful combined inguinal femoral and subgluteal sciatic nerve blocks (CFSNBs) for simultaneous bilateral below-knee amputations in a coagulopathic patient on antiplatelet therapy.

METHODS

A 70-year-old male patient presented with pain in both feet due to diabetic foot syndrome. The condition could not be managed by open amputations of the toes at the metatarsal bones and subsequent antibiotic therapy. Computed tomographic angiography showed significant stenosis in the arteries supplying the lower limbs, indicating atherosclerotic gangrene in both feet. Balloon angioplasty and bypass surgery with subsequent debridements with application of negative-pressure wound therapy and additional open amputations did not improve the patient's clinical condition: his leukocyte counts and C-reactive protein levels were above the normal range, and his prothrombin and activated partial thromboplastin times were increased.

RESULTS

Simultaneous bilateral below-knee amputations were performed under ultrasound-guided CFSNBs. Following left CFSNBs using 45 mL of a local anesthetic mixture (1:1 ratio of 1.0% mepivacaine and 0.75% ropivacaine), the left below-knee amputation was performed for 76 minutes. Subsequently, under right CFSNBs using 47 mL of the local anesthetic mixture, the right below-knee amputation proceeded for 85 minutes. Throughout each surgery, dexmedetomidine was continuously administered, and a sensory blockade was well maintained in both limbs. The patient did not complain of pain due to regression of the first CFSNBs during the second surgery. The CFSNBs successfully prevented tourniquet pain. Local anesthetic systemic toxicity (LAST) and hemodynamic instability due to tourniquet deflation and administration of dexmedetomidine did not occur. No additional analgesic was required to supplement insufficient surgical anesthesia. Postoperatively, no neurologic complications related to the CFSNBs were reported.

CONCLUSION

The timely placement of bilateral CFSNBs immediately before the corresponding limb surgery, which lasted for less than 2 hours, provided successful surgical anesthesia in both lower limbs without LAST or pain due to regression of the CFSNBs that were performed during the first surgery.

Sedation in oral and maxillofacial day care surgery: A comparative study between intravenous dexmedetomidine and midazolam

Introduction:

Sedation is an important component of day care oral and maxillofacial surgical procedures under local anesthesia. Although various sedative drugs in different regimens have been used for sedation, an ideal agent and regimen are yet to be established.

Aim:

The aim of this study is to compare the efficacy of intravenous (IV) dexmedetomidine and midazolam as a sedative agent for day care oral and maxillofacial surgical procedures.

Settings:

The study was conducted in the Department of Oral and Maxillofacial Surgery, SCB Dental College and Hospital, Cuttack, Odisha, India.

Materials and Methods:

A total of sixty adult patients of age group 18–65 years, of either sex were randomly selected equally in two groups for the study. One group named Group D received dexmedetomidine and the other named Group M received midazolam. Patients were evaluated for oxygen saturation (SPO₂), respiration rate (RR), systolic blood pressure (SBP), diastolic blood pressure (DBP), Ramsay sedation score, bispectral index (BIS) score, amnesia, Aldrete score, relaxation during the surgery, and drug preference.

Results:

Midazolam was associated with greater amnesia. Dexmedetomidine was associated with lower heart rate, SBP, and DBP. There was no significant difference in SPO₂, RR, Aldrete score, Ramsay sedation score, and BIS score between the two drugs. Patient preference and relaxation were more in dexmedetomidine group.

Conclusion:

IV dexmedetomidine is a comparable alternative to midazolam for sedation in day care oral and maxillofacial surgery under local anesthesia. It is the preferred drug when a lower heart rate and blood pressure or less amnesia is needed without any serious side effects.

Comparison of the effects of low volume prilocaine and alkalinized prilocaine for the regional intravenous anesthesia technique in hand and wrist surgery

Aim. Comparing the effectivity of prilocaine and prilocaine alkalinized with 8.4% NaHCO₃ in terms of sensory and motor block onset and termination durations in RIVA technique considering patients' satisfaction and tolerance with application of tourniquet undergoing hand-wrist surgery. Materials and Methods. 64 patients were randomised into two groups. First group (Group P) was administered prilocaine and second group (Group PN) was administered prilocaine + %8.4 NaHCO₃. Sensory and motor block onset and termination times and onset of tourniquet pain were recorded. Results. No significant difference was found between the two groups in terms of onset and termination of sensory block and the onset of motor block. The duration of the motor block was longer in Group PN than in Group P (P < 0.05). Tourniquet pain was more intense in Group P (P = 0.036). In Group PN, the use of additional drugs was recorded at a lower rate and patients' satisfaction was higher than Group P. Conclusion. In the present study, it was established that alkalinization of prilocaine had no effect on the duration of sensory block and it prolonged the duration of motor block, increased patients' satisfaction, and decreased tourniquet pain. It is our suggestion that future studies should be carried out on the issue by using different volumes.

The effects of preemptive tramadol and dexmedetomidine on shivering during arthroscopy

Background:

Shivering, the rate of which in regional anesthesia is 39% is an undesired complication seen postoperatively.

Aims:

This study aims to compare the ability of preventing the shivering of preemptive tramadol and dexmedetomidine during the spinal anesthesia (SA).

Methods:

A total of 90 patients with American Society of Anesthesiologists physical status I-II, aged 18-60 years and undergoing elective arthroscopic surgery with SA were divided into three groups randomly. After spinal block, 100 mg tramadol in 100 ml saline was applied in group T- (n = 30) and 0.5 μg/kg dexmedetomidine in 100 ml saline was applied in group D- (n = 30) and 100 ml saline was administered in group P- (n = 30) in 10 min. The hemodynamics, oxygen saturation, tympanic temperature, shivering and sedation scores were evaluated and recorded intraoperatively and 45 min after a postoperative period.

Results:

In group T and D, shivering scores were significantly lower when compared with group P in the intraoperative 20^th min (P = 0.01). Sedation scores in group D were significantly higher than the baseline values (P = 0.03) and values in group T and P (P = 0.04).

Conclusions:

Preemptive tramadol and dexmedetomidine are effective in preventing the shivering under SA. In addition, dexmedetomidine was superior in increasing the level of sedation which is sufficient to prevent the anxiety without any adverse effects.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects of intravenous and intrathecal dexmedetomidine in spinal anesthesia: a meta-analysis

PURPOSE

To assess the effects of dexmedetomidine on the duration of sensory and motor block, postoperative analgesia, hypotension, bradycardia, and side effects in patients undergoing spinal anesthesia.

METHODS

Two researchers searched MEDLINE, EMBASE, and the Cochrane controlled trial register independently for randomized controlled trials comparing dexmedetomidine with a placebo without any language restrictions.

RESULTS

A total of 412 patients from eight trials were included in this study. The results revealed that dexmedetomidine was statistically significant in prolonging the duration of sensory block (mean difference, MD = 73.55; 95% CI, [55.69, 91.40] P < 0.00001, I(2)  = 89%) and motor block (MD = 59.11; 95% CI, [29.58, 88.65] P < 0.00001, I(2)  = 91%) and the time to first request for postoperative analgesia (MD = 245.77, 95% CI, [143.53, 348.00] P < 0.00001, I(2)  = 98%). The occurrence of hypotension (OR = 0.60, 95% CI, [0.3-1.23], P = 0.40, I(2)  = 3%) and side effects (OR = 0.9, 95% CI, [0.36-2.22], P = 0.88, I(2)  = 0%) was not significantly different between dexmedetomidine and placebo. However, dexmedetomidine was associated with more frequent bradycardia requiring atropine (OR = 7.55; 95% CI, [2.76-20.63], P = 0.63, I(2)  = 0%).

CONCLUSIONS

This meta-analysis has shown that dexmedetomidine prolonged the duration of spinal anesthesia and improved postoperative analgesia and did not increase the incidence of hypotension and adverse events, but needs more atropine to reverse bradycardia.

Dexmedetomidine for sedation of patients undergoing elective surgery under regional anesthesia

BACKGROUND

Dexmedetomidine may be useful as a sedative agent. However, it has been reported that dexmedetomidine decreases systemic blood pressure, heart rate, and cardiac output in a dose-dependent manner. The purpose of this study was to determine the appropriate dose of intravenously administered dexmedetomidine for sedation.

METHODS

Forty-five American Society of Anesthesiologists physical status I-II patients under spinal anesthesia received dexmedetomidine 1 µg/kg intravenously as a loading dose. The patients were randomly allocated to one of three groups for maintenance dose: Group A (0.25 µg/kg/hr), Group B (0.50 µg/kg/hr), and Group C (0.75 µg/kg/hr). The hemodynamic variables and the Ramsay Sedation Scale (RSS) score were recorded for all patients. The numbers of patients who developed hypotension, bradycardia, or inadequate sedation necessitating further drug treatment were also recorded.

RESULTS

Systolic blood pressure, heart rate, and SpO2 were decreased, and RSS score was increased significantly at both 20 min and 40 min after injection of dexmedetomidine in the three study groups compared to baseline, without significant differences between the groups. The prevalence of hypotension, but not that of bradycardia or adjunctive midazolam administration, exhibited a positive correlation with the dose of dexmedetomidine.

CONCLUSIONS

Intravenous injection of dexmedetomidine 1 µg/kg followed by continuous administration at infusion rates of 0.25, 0.50, or 0.75 µg/kg/hr produced adequate levels of sedation. However, there was a tendency for the incidence of hypotension to increase as the dose increased. To minimize the risk of hemodynamic instability, a dose of 0.25 µg/kg/hr may be the most appropriate for continuous administration of dexmedetomidine.

Effect of supplementation of low dose intravenous dexmedetomidine on characteristics of spinal anaesthesia with hyperbaric bupivacaine

Aims:

Intravenous (IV) dexmedetomidine with excellent sedative properties has been shown to reduce analgesic requirements during general anaesthesia. A study was conducted to assess the effects of IV dexmedetomidine on sensory, motor, haemodynamic parameters and sedation during subarachnoid block (SAB).

Methods:

A total of 50 patients undergoing infraumbilical and lower limb surgeries under SAB were selected. Group D received IV dexmedetomidine 0.5 mcg/kg bolus over 10 min prior to SAB, followed by an infusion of 0.5 mcg/kg/h for the duration of the surgery. Group C received similar volume of normal saline infusion. Time for the onset of sensory and motor blockade, cephalad level of analgesia and duration of analgesia were noted. Sedation scores using Ramsay Sedation Score (RSS) and haemodynamic parameters were assessed.

Results:

Demographic parameters, duration and type of surgery were comparable. Onset of sensory block was 66±44.14 s in Group D compared with 129.6±102.4 s in Group C. The time for two segment regression was 111.52±30.9 min in Group D and 53.6±18.22 min in Group C and duration of analgesia was 222.8±123.4 min in Group D and 138.36±21.62 min in Group C. The duration of motor blockade was prolonged in Group D compared with Group C. There was clinically and statistically significant decrease in heart rate and blood pressures in Group D. The mean intraoperative RSS was higher in Group D.

Conclusion:

Administration of IV dexmedetomidine during SAB hastens the onset of sensory block and prolongs the duration of sensory and motor block with satisfactory arousable sedation.

Effect of the perioperative infusion of dexmedetomidine on chronic pain after breast surgery

Background:

This prospective double-blind trial was undertaken to analyze the role of perioperatively administered dexmedetomidine on the occurrence of chronic pain in cases undergoing surgery for breast cancer.

Subjects and Methods:

Eighty-six cases were randomly assigned to two groups to receive either dexmedetomidine (2 μg/ml) in group D or saline in group C, in a loading dose of 0.5 ml/kg, intravenous (IV), 30 min prior to induction, followed by a continuous infusion of 0.25 ml/kg/h IV till the completion of surgery, and then the dose tapered to 0.1 ml/kg/h for up to 24 h. The standardized questionnaires that measured chronic pain (Brief Pain Inventory, BPI; Short Form McGill Pain Questionnaire, SF-MPQ2) and quality of life (Quality of Life Scale, QOLS) were gathered after 3 months of surgery as a primary outcome. Pain (verbal numerical score, VNS), sedation scores (Ramsay scoring), and analgesic requirements were also assessed for 72 h postoperatively.

Results:

In total, 84 cases (n=42) were analyzed for acute pain and 69 (34 in group D and 35 in group C) for chronic pain. The consumption of isoflurane/fentanyl intra-operatively and paracetamol postoperatively was significantly lower in Group D. The sedation scores were non-significant between the groups. The VNS at rest and after movement was significantly lower in group D at corresponding times (except at 60 min) throughout the assessment period. The BPI and SF-MPQ2 scores were significantly lower in group D in most of the factors. The QOLS score was significantly better in group D in all items except for relationships, friends, and learning.

Conclusion:

The perioperative infusion of dexmedetomidine has a pivotal role in attenuating the incidence and severity of chronic pain and improving the quality of life in cases undergoing breast cancer surgery.

Facilitatory effects of perineural dexmedetomidine on neuraxial and peripheral nerve block: a systematic review and meta-analysis

Nerve blocks improve postoperative analgesia, but their benefits may be short-lived. This quantitative review examines whether perineural dexmedetomidine as a local anaesthetic (LA) adjuvant for neuraxial and peripheral nerve blocks can prolong the duration of analgesia compared with LA alone. All randomized controlled trials (RCTs) comparing the effect of dexmedetomidine as an LA adjuvant to LA alone on neuraxial and peripheral nerve blocks were reviewed. Sensory block duration, motor block duration, block onset times, analgesic consumption, time to first analgesic request, and side-effects were analysed.

RESULTS

were combined using random-effects modelling. A total of 516 patients were analysed from nine RCTs. Five trials investigated dexmedetomidine as part of spinal anaesthesia and four as part of a brachial plexus (BP) block. Sensory block duration was prolonged by 150 min [95% confidence interval (CI): 96, 205, P<0.00001] with intrathecal dexmedetomidine. Perineural dexmedetomidine used in BP block may prolong the mean duration of sensory block by 284 min (95% CI: 1, 566, P=0.05), but this difference did not reach statistical significance. Motor block duration and time to first analgesic request were prolonged for both intrathecal and BP block. Dexmedetomidine produced reversible bradycardia in 7% of BP block patients, but no effect on the incidence of hypotension. No patients experienced respiratory depression. Dexmedetomidine is a potential LA adjuvant that can exhibit a facilitatory effect when administered intrathecally as part of spinal anaesthesia or peripherally as part of a BP block. However, there are presently insufficient safety data to support perineural dexmedetomidine use in the clinical setting.

Addition of ketamine or dexmedetomidine to lignocaine in intravenous regional anesthesia: A randomized controlled study

Introduction:

Ketamine and dexmedetomidine decrease anesthetic requirement and provide analgesia to patients. We designed this study to compare the effect of dexmedetomidine and ketamine when added to lignocaine in intravenous regional anesthesia (IVRA).

Materials and Methods:

Seventy two patients undergoing hand surgery were randomly assigned to three groups to receive IVRA. They received 20 ml of 1% lignocaine and either 1 ml of isotonic saline (Group L, n = 24); or 0.5 mg/kg body weight ketamine (Group LK, n = 24) or 1 mcg/kg body weight dexmedetomidine (Group LD, n = 24). Sensory and motor block onset and recovery time were noted. After the tourniquet deflation, pain and sedation values, time to first analgesic requirement and any side effects were noted.

Results:

Shortened sensory and motor block onset times (69.17 min and 7.83 min respectively, P < 0.0001) and improved quality of anesthesia (satisfaction score = 3, P < 0.05) were found in ketamine group. Visual analog scale scores (3.21 ± 0.41) were comparable while time to first analgesic requirement (166.25 ± 25.89 min, P < 0.0001) was significantly longer in dexmedetomidine group after tourniquet release.

Conclusion:

We conclude that the addition of 1 mcg/kg of body weight dexmedetomidine or 0.5 mg/kg of body weight ketamine to lignocaine for IVRA improves quality of anesthesia and perioperative analgesia without causing side effects. We considered ketamine reduced the time for onset of block, delayed the onset of tourniquet pain, and reduced postoperative analgesic requirement and had a better patient satisfaction than placebo or dexmedetomidine.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Comparison of an Intraoperative Infusion of Dexmedetomidine or Remifentanil on Perioperative Haemodynamics, Hypnosis and Sedation, and Postoperative Pain Control

This prospective, randomized, double-blind study compared the effects of dexmedetomidine and remifentanil on haemodynamic stability, sedation and postoperative pain control in the postanaesthetic care unit (PACU). Fifty consecutive patients scheduled for total laparoscopic hysterectomy were randomly assigned to receive infusions of either dexmedetomidine (1 μg/kg) i.v. over 10 min followed by 0.2-0.7 μg/kg per h continuous i.v. infusion or remifentanil (0.8-1.2 μg/kg) i.v. over 1 min followed by 0.05-0.1 μg/kg i.v. per min, starting at the end of surgery to the time in the PACU. Modified observer's assessment of alertness scores were significantly lower in the dexmedetomidine group than in the remifentanil group at 0, 5 and 10 min after arrival in the PACU. Blood pressure and heart rate in the dexmedetomidine group were significantly lower than that recorded in the remifentanil group in the PACU. Dexmedetomidine, at the doses used in this study, had a significant advantage over remifentanil in terms of postoperative haemodynamic stability.

Dexmedetomidine for the prevention of shivering during spinal anesthesia

PURPOSE

The aim of this study was to evaluate the effect of dexmedetomidine on shivering during spinal anesthesia.

METHODS

Sixty patients (American Society of Anesthesiologists physical status I or II, aged 18-50 years), scheduled for elective minor surgical operations under spinal anesthesia with hyperbaric bupivacaine, were enrolled. They were administered saline (group C, n = 30) or dexmedetomidine (group D, n = 30). Motor block was assessed using a Modified Bromage Scale. The presence of shivering was assessed by a blinded observer after the completion of subarachnoid drug injection.

RESULTS

Hypothermia was observed in 21 patients (70%) in group D and in 20 patients (66.7%) in group C (p = 0.781). Three patients (10%) in group D and 17 patients (56.7%) in group C experienced shivering (p = 0.001). The intensity of shivering was lower in group D than in group C (p = 0.001). Time from baseline to onset of shivering was 10 (5-15) min in group D and 15 (5-45) min in group C (p = 0.207).

CONCLUSION

Dexmedetomidine infusion in the perioperative period significantly reduced shivering associated with spinal anesthesia during minor surgical procedures without any major adverse effect during the perioperative period. Therefore, we conclude that dexmedetomidine infusion is an effective drug for preventing shivering and providing sedation in patients during spinal anesthesia.

Dexmedetomidine: clinical application as an adjunct for intravenous regional anesthesia

The selective α-2 adrenoceptor agonist, dexmedetomidine, has been shown to be a useful, safe adjunct in perioperative medicine. Intravenous regional anesthesia is one of the simplest forms of regional anesthesia and has a high degree of success. However, intravenous regional anesthesia is limited by the development of tourniquet pain and its inability to provide postoperative analgesia. To improve block quality, prolong postdeflation analgesia, and decrease tourniquet pain, various chemical additives have been combined with local anesthetics, although with limited success. The antinociceptive effects of α-2 adrenoceptor agonists have been shown in animals and in humans. However, less is known about the clinical effects of dexmedetomidine when coadministered with local anesthetics in patients undergoing intravenous regional anesthesia. This review examines what is currently known to improve our understanding of the properties and application of dexmedetomidine when used as an adjunct in intravenous regional anesthesia.

The effects of intravenous dexmedetomidine on spinal hyperbaric ropivacaine anesthesia

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The role of the alpha 2A-adrenoceptor in mouse stress-coping behaviour

Acute stress is known to impair memory functions in both men and laboratory rodents. In human the alpha 2A-adrenoceptor system is known to play a critical role in regulating acute neuropsychological stress responses and, ultimately, stress-coping behaviour. In search for neurobiological and central nervous mechanisms behind these behaviours we investigated if the alpha 2A-adrenoceptor is involved in these mechanisms in mice. Phenotypical differences between the A/J and C57BL/6J (B6) mouse inbred strains were evaluated in previous studies. These data showed significant strain differences in various motivational systems (anxiety, exploration, locomotion, memory etc.). From the literature it is known that chromosome 19 contains the gene for the adrenergic alpha 2A receptor that is thought to be involved in emotional behaviours, among others anxiety-related avoidance behaviour and arousal. We investigated if this pathway could possibly be involved in avoidance/arousal susceptibility by applying an agonist (dexmedetomidine) and an antagonist (atipamezole) of the alpha 2A-adrenoceptor to male mice from a consomic strain (C57BL/6J-Chr 19(A)/NaJ, abbreviated to CSS19=anxious), and the corresponding donor (A/J=anxious) and host (B6=non-anxious) strains. The mice were tested in the modified hole board (mHB) test which allows for the assessment of a variety of behavioural patterns by use of only one test. In addition, a forced swimming test (FST) was conducted to test for stress-coping behaviour. Results of the behavioural testing in the mHB-test showed significant strains differences and strain-specific treatment effects for parameters describing anxiety-related endophenotypes. The FST revealed effects of dexmedetomidine and atipamezole on stress-coping behaviour. In conclusion, the involvement of the alpha 2A-adrenoceptor, located on mouse chromosome 19, on anxiety-related behaviour remains unclear and will possibly not play a main role in the development of anxiety-related behaviour in mice. However, we could show involvement of this receptor in stress-coping behaviour in mice.

Intravenous dexmedetomidine, but not midazolam, prolongs bupivacaine spinal anesthesia

PURPOSE

Midazolam has only sedative properties. However, dexmedetomidine has both analgesic and sedative properties that may prolong the duration of sensory and motor block obtained with spinal anesthesia. This study was designed to compare intravenous dexmedetomidine with midazolam and placebo on spinal block duration, analgesia, and sedation in patients undergoing transurethral resection of the prostate.

METHODS

In this double-blind randomized placebo-controlled trial, 75 American Society of Anesthesiologists' I and II patients received dexmedetomidine 0.5 microg . kg(-1), midazolam 0.05 mg . kg(-1), or saline intravenously before spinal anesthesia with bupivacaine 0.5% 15 mg (n = 25 per group). The maximum upper level of sensory block and sensory and motor regression times were recorded. Postoperative analgesic requirements and sedation were also recorded.

RESULTS

Sensory block was higher with dexmedetomidine (T 4.6 +/- 0.6) than with midazolam (T 6.4 +/- 0.9; P < 0.001) or saline (T 6.4 +/- 0.8; P < 0.001). Time for sensory regression of two dermatomes was 145 +/- 26 min in the dexmedetomidine group, longer (P < 0.001) than in the midazolam (106 +/- 39 min) or the saline (97 +/- 27 min) groups. Duration of motor block was similar in all groups. Dexmedetomidine also increased the time to first request for postoperative analgesia (P < 0.01 compared with midazolam and saline) and decreased analgesic requirements (P < 0.05). The maximum Ramsay sedation score was greater in the dexmedetomidine and midazolam groups than in the saline group (P < 0.001).

CONCLUSION

Intravenous dexmedetomidine, but not midazolam, prolonged spinal bupivacaine sensory blockade. It also provided sedation and additional analgesia.

Melatonin improves tourniquet tolerance and enhances postoperative analgesia in patients receiving intravenous regional anesthesia

BACKGROUND

Melatonin has anxiolytic and potential analgesic effects. We assessed the efficacy of melatonin premedication in reducing tourniquet-related pain and improving analgesia in patients receiving IV regional anesthesia (IVRA).

METHODS

Forty patients undergoing elective hand surgery under IVRA were randomly assigned into two groups (20 patients each) to receive either melatonin 10 mg (melatonin group) or placebo (control group) as oral premedication. IVRA was achieved with lidocaine, 3 mg/kg, diluted with saline to a total volume of 40 mL. Anxiety scores, hemodynamic changes, sensory and motor block onset and recovery times, tourniquet pain, the quality of intraoperative anesthesia, time to first analgesic request, and 24 h analgesic requirements were recorded.

RESULTS

After premedication, the anxiety scores were significantly reduced in the melatonin group (P=0.023). During surgery, patients who received melatonin premedication had better tourniquet tolerance (lower verbal pain scores at 30, 40, and 50 min after tourniquet inflation, P<0.05), lower rescue fentanyl requirements (15.6+/-21.9 vs 45.7+/-33.4 microg, P=0.002), longer time to the first postoperative analgesic request (145.4+/-20.2 min vs 74.6+/-12.8, P<0.001) and lower postoperative diclofenac consumption at 24 h (86.3+/-27.5 mg vs 116.3+/-38.3 mg, P=0.007) compared with the control group.

CONCLUSIONS

Melatonin is an effective premedication before IVRA since it reduced patient anxiety, decreased tourniquet-related pain, and improved perioperative analgesia.

Autonomic activity during dexmedetomidine or fentanyl infusion with desflurane anesthesia

STUDY OBJECTIVE

To evaluate autonomic activity with dexmedetomidine or fentanyl infusion and desflurane anesthesia during laparoscopic gastric banding.

STUDY DESIGN

Randomized, single-blinded, open-label study.

SETTING

Operating rooms at a university hospital.

SUBJECTS

40 patients scheduled for laparoscopic gastric banding with a mean body mass index of 50 kg/m2.

INTERVENTIONS

Patients received either dexmedetomidine (0.5 microg/kg given intravenously over 10 minutes, 0.4 microg.kg-1.h-1, n=20) or fentanyl (0.5 microg.kg-1 bolus, 1 microg.kg-1.h-1, n=20) during anesthesia. Response entropy of the electroencephalogram was maintained at 45+/-5 by adjusting end-tidal desflurane concentration.

MEASUREMENTS

In the operating room, blood pressure, heart rate (HR), response entropy, end-tidal desflurane concentration, tone entropy, and power-spectral analysis of HR were measured with the patient awake; 20, 40, and 60 minutes from intubation and the start of drug infusion; and at extubation.

MAIN RESULTS

The mean end-tidal desflurane concentration during anesthesia was 4.0%+/-0.6% with dexmedetomidine and 4.1%+/-0.7% with fentanyl, indicating a similar anesthetic requirement in both groups. Autonomic activity, determined by tone entropy and spectral analysis of HR, decreased by 50% during anesthesia in both groups. The dexmedetomidine group showed a greater decrease in sympathovagal balance during anesthesia.

CONCLUSION

Both dexmedetomidine and fentanyl facilitated anesthesia and attenuated autonomic activity. Dexmedetomidine produced a greater decrease in sympathovagal balance than fentanyl.

Effects of dexmedetomidine on the duration of anaesthesia and wakefulness in bupivacaine epidural block

BACKGROUND

The purpose of this study was to examine the effects of intravenous dexmedetomidine on the duration of bupivacaine-induced epidural anaesthesia and level of wakefulness and the respective side-effects.

METHODS

Sixty ASA I-II patients were included in the study. Consecutive patients were allocated to groups according to the last digit (odd/even) of their admission numbers. All patients had epidural anaesthesia with bupivacaine 0.5% performed by the same experienced anaesthesiologist. In the first group, the patients were administered intravenous dexmedetomidine infusion just after the epidural block and continued during the operation, while those in the second group were administered physiologic saline infusion at the same amount and duration.

RESULTS

The recovery time of sensory block was significantly longer in the first group. The bispectral index values were lower in the first group than in the second. Also, heart rate was significantly lower in Group I than in Group II. Regarding side-effects, shivering was significantly less frequent in the first group, whereas there was a significant increase in the requirement of atropine in the first group as dexmedetomidine caused bradycardia.

CONCLUSION

Intravenous administration of dexmedetomidine prolonged the duration of epidural anaesthesia, provided sedation and had few side-effects.

Intraoperative infusion of dexmedetomidine reduces perioperative analgesic requirements

PURPOSE

This prospective, randomized, double-blind study was designed to assess whether intraoperative infusion of dexmedetomidine provides effective postoperative analgesia. Postoperative pain scores and morphine consumption were compared in a treated group and a placebo group, both of which received patient-controlled morphine after total abdominal hysterectomy.

METHODS

Fifty women were randomly assigned to two groups. Group D (n = 25) received a loading dose of dexmedetomidine 1 mug.kg(-1) iv during induction of anesthesia, followed by a continuous infusion at a rate of 0.5 mug.kg(-1).hr(-1) throughout the operation. Group P (n = 25) received a volume-matched bolus and infusion of placebo (0.9% saline). For each case, heart rate, peripheral oxygen saturation, and systolic and diastolic blood pressure were recorded intraoperatively and for 48 hr postoperatively. Patients used a patient-controlled analgesia device to receive bolus doses of morphine after surgery. Total morphine consumption, pain scores, and sedation scores were recorded for the first 48 hr (two hours in the postanesthesia care unit and 46 hr on the ward).

RESULTS

The groups were similar with respect to mean times to extubation of the trachea. Pain and sedation scores were also similar between groups at all corresponding times throughout the 48-hr period of observation. Group D patients consumed significantly less morphine in the postanesthesia care unit and on the ward (P < 0.05 and P < 0.01, respectively). Fewer patients in Group D experienced itching or nausea/vomiting (P < 0.05).

CONCLUSION

Continuous iv dexmedetomidine during abdominal surgery provides effective postoperative analgesia, and reduces postoperative morphine requirements without increasing the incidence of side effects.

Comparison of buccal and intramuscular dexmedetomidine premedication for arthroscopic knee surgery

STUDY OBJECTIVE

To compare the sedative, anxiolytic, analgesic, hemodynamic, and respiratory effects of buccal dexmedetomidine with intramuscular (IM) dexmedetomidine for premedication in patients undergoing arthroscopic knee surgery during spinal anesthesia.

DESIGN

Randomized, placebo-controlled trial.

SETTING

University medical center.

PATIENTS

75 ASA physical status I and II patients undergoing arthroscopic knee surgery with spinal anesthesia.

INTERVENTIONS

Patients were randomized to one of three groups for premedication: group B, buccal dexmedetomidine 2.5 microg kg(-1); group IM, IM dexmedetomidine 2.5 microg kg(-1); and group P, buccal 0.9% and NaCl 2 mL.

MEASUREMENTS

Noninvasive blood pressure, heart rate, respiratory rate, and peripheral oxygen saturation were recorded. Sedation and anxiety levels were consecutively assessed with Ramsay sedation scores and Visual Analog Scale (VAS) scores of anxiety before premedication, before spinal anesthesia, during surgery, and at the end of surgery. Two, 4, and 8 hours after surgery, sedation levels, postoperative VAS pain scores, and consumption of analgesics (diclofenac sodium) were recorded.

MAIN RESULTS

Before spinal anesthesia, during surgery, and at the end of surgery, sedation and anxiety scores of the patients receiving buccal or IM dexmedetomidine were, respectively, higher and lower than in group P. Patients receiving buccal dexmedetomidine (group B) had lower requirement of diclofenac sodium than group P and lower pain scores than groups P and IM. Mild hypotension and bradycardia were observed in the buccal and IM dexmedetomidine patients.

CONCLUSIONS

Buccal dexmedetomidine for premedication in arthroscopic knee surgery provided equal levels of sedation and anxiolysis, and more evident analgesia compared with IM dexmedetomidine.

Dexmedetomidine Versus Midazolam in Outpatient Third Molar Surgery

PURPOSE

The aim of this study was to compare the use of dexmedetomidine with the use of midazolam during intravenous conscious sedation in third molar surgery.

PATIENTS AND METHODS

Twenty healthy patients with symmetrically impacted mandibular third molars were included in this double-blind, crossover, randomized study. Either dexmedetomidine (group D) (4 microg.kg(-1).h(-1)) or midazolam (group M) (0.4 mg.kg(-1).h(-1)) was administered intravenously for 15 minutes before the first operation. At the second operation, the other agent was applied. Cardiorespiratory data were collected. The intraoperative sedation level, patient cooperation, and postoperative performance were scored and any pain reaction during the local anesthetic injection was recorded. Visual analog scales were additionally used for the subjective assessment of pain and patient satisfaction. Amnesia was evaluated by the patients' ability to recall the objects shown during the operations and the local anesthetic injection. Patients' preferences were recorded during the interview at the end of the second operations.

RESULTS

The mean heart rate and blood pressure measurements were significantly lower in group D. There was no significant difference in the respiratory findings. A significantly higher number of patients showed pain reactions in group M. Sedation level, postoperative performance, and VAS pain scores were not statistically significant, whereas the differences in cooperation score and VAS for patient satisfaction were significant. Adequate amnesia was obtained in group M, however, no amnesia was demonstrated in group D. Sixty-five percent of the patients indicated a preference for dexmedetomidine sedation.

CONCLUSION

Dexmedetomidine may be a remarkable alternative to midazolam for intravenous sedation because it seems to be a reliable and safe method, with additional analgesic effect providing a satisfactory sedation level without any serious side effects during impacted third molar surgery.

The changing role of non-opioid analgesic techniques in the management of postoperative pain

Given the expanding role of ambulatory surgery and the need to facilitate an earlier hospital discharge, improving postoperative pain control has become an increasingly important issue for all anesthesiologists. As a result of the shift from inpatient to outpatient surgery, the use of IV patient-controlled analgesia and continuous epidural infusions has steadily declined. To manage the pain associated with increasingly complex surgical procedures on an ambulatory or short-stay basis, anesthesiologists and surgeons should prescribe multimodal analgesic regimens that use non-opioid analgesics (e.g., local anesthetics, nonsteroidal antiinflammatory drugs, cyclooxygenase inhibitors, acetaminophen, ketamine, alpha 2-agonists) to supplement opioid analgesics. The opioid-sparing effects of these compounds may lead to reduced nausea, vomiting, constipation, urinary retention, respiratory depression and sedation. Therefore, use of non-opioid analgesic techniques can lead to an improved quality of recovery for surgical patients.

Effect of Dexmedetomidine on Haemodynamic Responses to Laryngoscopy and Intubation

BACKGROUND

Dexmedetomidine reduces the dose requirements for opioids and anaesthetic agents. The purpose of this study was to evaluate the effect of a single pre-induction intravenous dose of dexmedetomidine 1 microg/kg on cardiovascular response resulting from laryngoscopy and endotracheal intubation, need for anaesthetic agent and perioperative haemodynamic stability.

METHODS

Fifty patients scheduled for elective minor surgery were randomised into two groups (dexmedetomidine group and placebo group, n = 25 in each group). During and after drug administration, the Ramsey sedation scale was applied every 5 minutes. Fentanyl 1 microg/kg was administered to all patients and thiopental was given until lash reflex disappeared. Anaesthesia continuation was maintained with 50% : 50%, oxygen : nitrous oxide. Sevoflurane concentration was adjusted to maintain systolic blood pressure within 20% of preoperative values. After extubation, the Steward awakening score was applied at 5 and 10 minutes. Haemodynamic parameters and adverse effects were recorded every 10 minutes for 1 hour after surgery.

RESULTS

During intubation the need for thiopental and sevoflurane concentration were decreased by 39% and 92%, respectively, in the dexmedetomidine group compared with the placebo group. In all groups, blood pressure and heart rate increased after tracheal intubation; both were significantly lower in the dexmedetomidine group than in the placebo group (p < 0.05). Fentanyl requirement during the operation was 74.20 +/- 10.53microg in the dexmedetomidine group and 84.00 +/- 27.04microg in the placebo group (p < 0.05). At 5 minutes, the Steward scores were >6 in 56% of the dexmedetomidine group and in 4% of the placebo group (p < 0.05). At 10 minutes, sedation scores were > or =4 in all patients in the dexmedetomidine group (p < 0.05). Arterial blood pressure and heart rate in the postoperative period were significantly lower in the dexmedetomidine group compared with the placebo group (p < 0.05).

CONCLUSION

Preoperative administration of a single dose of dexmedetomidine resulted in progressive increases in sedation, blunted the haemodynamic responses during laryngoscopy, and reduced opioid and anaesthetic requirements. Furthermore, dexmedetomidine decreased blood pressure and heart rate as well as the recovery time after the operation.

Adding dexmedetomidine to lidocaine for intravenous regional anesthesia

Dexmedetomidine is approximately 8 times more selective toward the alpha-2-adrenoceptors than clonidine. It decreases anesthetic requirements by up to 90% and induces analgesia in patients. We designed this study to evaluate the effect of dexmedetomidine when added to lidocaine in IV regional anesthesia (IVRA). We investigated onset and duration of sensory and motor blocks, the quality of the anesthesia, intraoperative-postoperative hemodynamic variables, and intraoperative-postoperative pain and sedation. Thirty patients undergoing hand surgery were randomly assigned to 2 groups to receive IVRA. They received 40 mL of 0.5% lidocaine and either 1 mL of isotonic saline (group L, n = 15) or 0.5 microg/kg dexmedetomidine (group LD, n = 15). Sensory and motor block onset and recovery times and anesthesia quality were noted. Before and after the tourniquet application at 5, 10, 15, 20, and 40 min, hemodynamic variables, tourniquet pain and sedation, and analgesic use were recorded. After the tourniquet deflation, at 30 min, and 2, 4, 6, 12, and 24 h, hemodynamic variables, pain and sedation values, time to first analgesic requirement, analgesic use, and side effects were noted. Shortened sensory and motor block onset times, prolonged sensory and motor block recovery times, prolonged tolerance for the tourniquet, and improved quality of anesthesia were found in group LD. Visual analog scale scores were significantly less in group LD in the intraoperative period and 30 min, and 2, 4, and 6 h after tourniquet release. Intra-postoperative analgesic requirements were significantly less in group LD. Time to first analgesic requirements was significantly longer in group LD in the postoperative period. We conclude that the addition of 0.5 microg/kg dexmedetomidine to lidocaine for IVRA improves quality of anesthesia and perioperative analgesia without causing side effects.

IMPLICATIONS

This study was designed to evaluate the effect of dexmedetomidine when added to lidocaine for IV regional anesthesia. This is the first clinical study demonstrating that the addition of 0.5 microg/kg dexmedetomidine to lidocaine for IV regional anesthesia improves quality of anesthesia and intraoperative-postoperative analgesia without causing side effects.

Single-dose dexmedetomidine reduces agitation after sevoflurane anesthesia in children

Emergence agitation is a common side effect of sevoflurane anesthesia in children. Dexmedetomidine, because of its sedative and analgesic properties, might be useful for the management of this adverse effect. We studied the effect of dexmedetomidine on recovery characteristics in 90 children aged 1 to 10 yr scheduled to undergo superficial lower abdominal and genital surgery. After inhaled induction with sevoflurane, patients were randomly assigned to receive saline (Group 1, n = 30), dexmedetomidine 0.15 micro g/kg (Group 2, n = 30), or dexmedetomidine 0.30 micro g/kg (Group 3, n = 30). After a laryngeal mask airway insertion a caudal block was performed in all patients. Maintenance of anesthesia was with 1% end-tidal sevoflurane and 50% nitrous oxide and spontaneous ventilation. Intraoperative hemodynamic and respiratory variables were recorded every 5 min. At the end of anesthesia time to eyes opening (TEO) and characteristics of emergence were recorded. General and intraoperative variables were similar in the 3 groups. The TEO was 7.5 +/- 5.0 min in Group 1, 8.2 +/- 5.0 min in Group 2, and 9.8 +/- 4.0 min in Group 3 (NS). The incidence (95% confidence interval) of agitation was 37% (20%-54%) in Group 1, 17% (4%-30%) in Group 2, and 10% (0%-21%) in Group 3 (P < 0.05). Paired comparisons showed a significant difference for Group 1 versus Group 3 (P < 0.05, 95% confidence interval of the difference: 7%-47%). The time to discharge from the postanesthesia care unit was similar for the 3 groups. We conclude that a dose of dexmedetomidine 0.3 micro g/kg administered after induction of anesthesia reduces the postsevoflurane agitation in children and with no adverse effects.

IMPLICATIONS

In children undergoing surgery using sevoflurane anesthesia, dexmedetomidine 0.3 micro g/kg administered in 10 min after induction reduced the incidence of emergence agitation from 37% in the control group to 10%. No adverse effects attributable to dexmedetomidine were observed.

Oral Clonidine Premedication Exacerbates Hypotension Following Tourniquet Deflation by Inhibiting Noradrenaline Release

Clonidine premedication prevents tourniquet pain and reduces sympathetic nerve activity. We evaluated hemodynamic changes and catecholamine release following tourniquet deflation during spinal anesthesia in patients who received oral clonidine premedication. The final analysis included 24 otherwise healthy patients undergoing lower-limb surgery randomly assigned to two groups: those receiving approximately 5 micrograms/kg of oral clonidine 1 hr before anesthesia (clonidine group, n = 12), and those receiving no premedication (control group, n = 12). After lumbar anesthesia, a tourniquet was applied for approximately 60 minutes to each patient. Electrocardiogram, arterial blood pressure, and consumption of butorphanol for tourniquet pain were monitored. Blood samples were obtained at different times to measure serum concentration of catecholamine. In the clonidine group, mean blood pressure decreased from 87 +/- 7 mmHg at baseline to 65 +/- 10 mmHg after tourniquet deflation (P < 0.05). This peak reduction of mean blood pressure in the clonidine group was significantly lower than in the control group. After receiving clonidine premedication, the plasma noradrenaline concentrations in the clonidine group were significantly lower than those in the control group. Noradrenaline concentration increased in the control group from 162.3 +/- 89.2 pg/mL before tourniquet deflation to 199.3 +/- 95.7 pg/mL afterward (P < 0.01), but there was no significant change in noradrenaline concentration after tourniquet deflation in the clonidine group. We conclude that oral clonidine premedication exacerbated the reduction in mean blood pressure following tourniquet deflation by inhibiting noradrenaline release.

Bispectral index-guided sedation with dexmedetomidine in intensive care: a prospective, randomized, double blind, placebo-controlled phase II study

OBJECTIVE

To compare dexmedetomidine vs. placebo with respect to the amount of additional propofol and morphine used for bispectral index-guided sedation and analgesia in mechanically ventilated, intensive care patients after surgery.

DESIGN

Prospective, randomized, double blind, placebo-controlled, phase II clinical trial.

SETTING

General surgical and cardiac surgical intensive care units.

PATIENTS

Thirty patients scheduled for major surgery requiring mechanical ventilation for a minimum of 6 hrs were included in the study.

INTERVENTIONS

Patients were assigned randomly to receive either dexmedetomidine (loading infusion, 6.0 microg x kg(-1) x hr(-1) for 10 mins; maintenance infusion, 0.1-0.7 microg x kg(-1) x hr(-1)) or placebo after intensive care unit admission.

MEASUREMENTS AND MAIN RESULTS

Sedation was guided by using the electroencephalographic parameter bispectral index, a new noninvasive method to estimate the level of sedation. We aimed at maintaining bispectral index ranges between 60 and 70 during mechanical ventilation before starting weaning, 65 and 95 during weaning, and 85 to 95 postextubation. Additional sedative and analgesic medication was given (propofol and morphine) as clinically indicated and within the previously mentioned bispectral index ranges. Patients receiving dexmedetomidine required significantly less propofol during mechanical ventilation (0.87 +/- 0.21 vs. 1.52 +/- 0.30 mg x kg(-1) x hr(-1); p <.01) and weaning (0.17 +/- 0.06 vs. 0.62 +/- 0.21 mg x kg(-1) x hr(-1); p <.001) to maintain the target bispectral index range. During study drug administration, morphine requirements for dexmedetomidine-treated patients were reduced by 58% (p =.05). Hemodynamic stability during weaning and after extubation was better maintained in patients receiving dexmedetomidine.

CONCLUSIONS

Dexmedetomidine reduced propofol requirements and improved hemodynamic stability during bispectral index-guided intensive care unit sedation.

New agents for sedation in the intensive care unit

Several advances are likely to benefit the ICU patient requiring sedation, analgesia, and anxiolysis. The cooperative sedation induced by dexmedetomidine is a unique and valuable state that allows patients to be aroused easily and interferes little with ventilation. Remifentanil is the prototype of short-acting drugs, providing fast onset and offset; its relatively high cost may be balanced by limiting the risk for long-lasting respiratory depression. Lorazepam seems to be finding more proponents, especially in long-term ICU sedation where the costs of the newer agents may be prohibitive.

Effect of dexmedetomidine on propofol requirements in healthy subjects

Dexmedetomidine-propofol pharmacodynamic interaction was evaluated in nine healthy subjects in a crossover design. Dexmedetomidine/placebo was infused using a computer-controlled infusion pump (CCIP) to maintain a pseudo-steady-state plasma concentration of 0.66 +/- 0.080 or 0 ng/mL, respectively. Forty-five minutes after the dexmedetomidine/placebo infusion was started, propofol was infused using a second CCIP to achieve a stepwise logarithmically ascending propofol concentration (1.00 to 13.8 microg/mL) profile. Each propofol step lasted 10 min. Blood was sampled for plasma concentration determination, and pharmacodynamic endpoint assessments were made during the study. Propofol and dexmedetomidine/placebo infusions were terminated when three endpoints (subjects were too sedated to hold a syringe, followed by loss of eyelash reflex, followed by loss of motor response to electrical stimulation) were achieved sequentially. The concentration of propofol associated with 50% probability of achieving a pharmacodynamic endpoint in the absence of dexmedetomidine (EC50; placebo treatment) was 6.63 microg/mL for motor response to electrical stimulation and ranged from 1.14 to 1.98 microg/mL for the ability to hold a syringe, eyelash reflex, and sedation scores. The apparent EC50 values of propofol (EC50APP; concentration of propofol at which the probability of achieving a pharmacodynamic endpoint is 50% in the presence of dexmedetomidine concentrations observed in the current study; dexmedetomidine treatment) were 0.273, 0.544-0.643, and 3.89 microg/mL for the ability to hold a syringe, sedation scores, and motor response, respectively. Dexmedetomidine reduced propofol concentrations required for sedation and suppression of motor response. Therefore, the propofol dose required for sedation and induction of anesthesia may have to be reduced in the presence of dexmedetomidine.