Cardiovascular and parasympathetic effects of dexmedetomidine in healthy subjects

Insight into Cardioprotective Effects and Mechanisms of Dexmedetomidine

PURPOSE

Cardiovascular disease remains the leading cause of death worldwide. Dexmedetomidine is a highly selective α2 adrenergic receptor agonist with sedative, analgesic, anxiolytic, and sympatholytic properties, and several studies have shown its possible protective effects in cardiac injury. The aim of this review is to further elucidate the underlying cardioprotective mechanisms of dexmedetomidine, thus suggesting its potential in the clinical management of cardiac injury.

RESULTS AND CONCLUSION

Our review summarizes the findings related to the involvement of dexmedetomidine in cardiac injury and discusses the results in the light of different mechanisms. We found that numerous mechanisms may contribute to the cardioprotective effects of dexmedetomidine, including the regulation of programmed cell death, autophagy and fibrosis, alleviation of inflammatory response, endothelial dysfunction and microcirculatory derangements, improvement of mitochondrial dysregulation, hemodynamics, and arrhythmias. Dexmedetomidine may play a promising and beneficial role in the treatment of cardiovascular disease.

Comparison of the effects of dexmedetomidine and propofol on the cardiovascular autonomic nervous system during spinal anesthesia: preliminary randomized controlled observational study

Spinal anesthesia induces sympatholysis and is usually combined with dexmedetomidine or propofol which induce different hemodynamic changes. The purpose of this study was to compare the effect on autonomic nervous system between dexmedetomidine and propofol combined with spinal anesthesia. Patients aged 20-65 undergoing elective surgery under spinal anesthesia were randomly assigned to dexmedetomidine or propofol group. Heart rate variability (HRV) and hemodynamic variables were measured at four time points: T0, baseline; T1, 10 min after spinal anesthesia; T2, 10 min after sedative administration; and T3, 20 min after sedative administration. In 59 patients, dexmedetomidine and propofol groups had significantly different hemodynamic changes over time (time × group effect P < 0.001). The dexmedetomidine group had slower heart rate at T2 (P = 0.001) and higher blood pressures at T2 and T3 (P < 0.001) than the propofol group. Overall HRV dynamics showed a significant change over time from T0 to T3, but both groups exhibited similar trends. Compared to the baseline data within the group, the low frequency (LF) decreased in both groups but the decrease occurred at T2 in the propofol group and at T3 in the dexmedetomidine group. The high frequency (HF) increased at T2 and T3 only in the dexmedetomidine group. The LF/HF ratio decreased in the dexmedetomidine group at T3. Dexmedetomidine showed slower heart rate and higher blood pressure than propofol when combined with spinal anesthesia, however, dexmedetomidine and propofol exhibited similar trends in HRV dynamics. Compared with the baseline within each group, both agents decreased LF, but only dexmedetomidine increased HF and decreased in the LF/HF ratio significantly.

Impact of Bilateral Quadratus Lumborum Block Using Different Doses of Dexmedetomidine for Postoperative Analgesia in Laparoscopic Myomectomy: A Randomized Controlled Trial

OBJECTIVES

The optimal dosage of dexmedetomidine (DEX) for postoperative analgesia of quadratus lumborum block (QLB) after laparoscopic myomectomy is not clear. Our study evaluated the analgesic and adverse effects of different doses of locally administered DEX.

MATERIALS AND METHODS

Patients underwent laparoscopic myomectomy were enrolled in this randomized controlled trial. Transmuscular bilateral QLB was conducted postoperatively using local anesthetic plus different doses of DEX, as an adjuvant, per side. Numeric rating scales (NRS) of pain score and heart rate (HR) were assessed after performing QLB. Additional analgesics through patient-controlled analgesia pump, recovery time to first flatus, hospital stay, and other outcomes were also compared.

RESULTS

A total of 150 participants were randomly divided into 3 groups (DEX1 group: 0.1 μg/kg; DEX2 group: 0.3 μg/kg; DEX3 group: 0.5 μg/kg), 50 for each group. Compared with the DEX1 group, NRS pain scores were lower in groups DEX2 and DEX3 ( P <0.017) 20 minutes after QLB and the significance lasted for 24 hours. Patients in groups DEX2 and DEX3 needed fewer additional analgesics than the group DEX1 ( P <0.017). HR in groups DEX2 and DEX3 was lower than the group DEX1 10 minutes and 20 minutes after QLB, respectively ( P <0.017). Sixty minutes after QLB, HR in the DEX3 group was still lower than the other groups. More patients in the DEX3 group were found bradycardia. Satisfaction score of postoperative analgesia was higher in groups DEX2 and DEX3 than the DEX1 group ( P <0.017).

DISCUSSION

The results suggest that solution of DEX 0.3 μg/kg in ropivacaine 0.25% for QLB is recommended to relieve postoperative pain after laparoscopic myomectomy effectively and safely.

Sublingual dexmedetomidine (BXCL501) reduces opioid withdrawal symptoms: findings from a multi-site, phase 1b/2, randomized, double-blind, placebo-controlled trial

Background: Like other alpha-2-adrenergic receptor agonists, dexmedetomidine may reduce the severity of opioid withdrawal but with fewer adverse cardiovascular effects.Objective: This study assessed the safety of sublingual dexmedetomidine (BXCL501) and its preliminary efficacy in treating opioid withdrawal (ClinicalTrials.gov: NCT04470050).Methods: Withdrawal was induced among individuals with physiological dependence on opioids via discontinuation of oral morphine (Days 1-5). Participants were randomized to receive placebo or active BXCL501: 30, 60, 90, 120, 180, and 240 μg twice daily (Days 6-12). Treatment-emergent adverse events (TEAEs) were the primary outcome measure. Secondary outcomes included the Clinical and Subjective Opiate Withdrawal Scales (COWS and SOWS-Gossop, respectively), and the Agitation and Calmness Evaluation Scale (ACES).Results: Of 225 participants enrolled, 90 discontinued during morphine stabilization. Post-BXCL501 randomization (Day 6) data were available from 135 participants (73% male), with 33% completing thru Day 12. In total, 36 subjects reported 1 or more TEAE. Higher doses of BXCL501 (i.e. 180 and 240 µg, twice daily) increased the frequency of: hypotension, orthostatic hypotension, and somnolence. TEAEs related to BXCL501 were mild or moderate in severity, except for one participant in the 120 µg condition whose orthostatic hypotension and bradycardia were classified as severe. Higher BXCL501 dose conditions (120, 180, and 240 µg) resulted in statistically significant reductions in COWS & SOWS scores. Mean ratings on the ACES were between 3 (mild), 4 (normal), and 5 (mild calmness), with few significant differences as a function of dose.Conclusions: These findings support the continued development of BXCL501 for the management of opioid withdrawal.

Effects of Dexmedetomidine on Basic Cardiac Electrophysiology in Adults; a Descriptive Review and a Prospective Case Study

Dexmedetomidine (DEX) is a commonly used sedative agent with no or minimal effects on breathing. DEX may also be beneficial in myocardial protection. Since the mechanisms of cardiac effects are not well known, we carried out a descriptive review and examined the effects of DEX on myocardial electrical conduction in a prospective and controlled manner. For the review, clinical studies exploring DEX in myocardial protection published between 2020-2022 were explored. A case study included 11 consecutive patients at a median (range) age of 48 (38-59), scheduled for elective radiofrequency ablation of paroxysmal atrial fibrillation. A bolus dose of DEX 1 µg/kg given in 15 min was followed by a continuous infusion of 0.2-0.7 µg/kg/h. Direct intracardiac electrophysiologic measurements, hemodynamics and oxygenation were measured before and after the DEX bolus. Experimental studies show that DEX protects the heart both via stabilizing cardiac electrophysiology and reducing apoptosis and autophagy after cell injury. The clinical evidence shows that DEX provides cardiac protection during different surgeries. In a clinical study, DEX increased the corrected sinus node recovery time, prolongated the atrioventricular (AV) nodal refractory period and cycle length producing AV nodal Wenckebach retrograde conduction block. DEX has a putative role in organ protection against hypoxic, oxidative and reperfusion injury. DEX slows down the firing of the sinus node and prolongs AV refractoriness.

Dexmedetomidine dosage in critically ill patients undergoing intraoperative wake-up test: A randomized controlled trial

OBJECTIVE

The aim of this study was to find the optimum dosage of dexmedetomidine in Spinal Orthopedic Scoliosis Correction Surgery when used in combination with propofol and remifentanil in American Society of Anesthesiologists (ASA) III patients with severe scoliosis undergoing intraoperative wake-up test.

MATERIALS AND METHODS

We selected a total of 60 ASA III ≤40 years old patients who underwent Spinal Orthopedic Scoliosis Correction Surgery (SOSCS) and randomized them into groups A, B, and C. Group A was administered 0.2 μg/(kg·h) of dexmedetomidine, group B 0.3 μg/(kg·h), and group C 0.4 μg/(kg·h). The main parameters monitored were: wake-up time; wake-up quality; adverse effects that occur while the patient is awake; postoperative awareness of intraoperative wake-up test; heart rate (HR); mean arterial pressure (MAP); and oxygen saturation (SpO2). Values of these parameters were monitored at 7 timestamps separated by 5 minutes >30 minutes.

RESULTS

Group B had a higher MAP at 10 minutes before wake-up (P = .03) and at the moment of wake-up (P = .04) than group A. The Wake-up time of group A was 14.95 ± 7.42 minutes, group B was 14.7 ± 6.52 minutes, which was significantly shorter than that of group C 21.3 ± 10.02 minutes (P = .02). The wake-up quality was excellent. All other parameters had no significant statistical differences.

CONCLUSION

Doses of 0.2 to 0.3 μg/(kg·h) have shorter wake-up time and fewer hemodynamic fluctuations compared to 0.4 μg/(kg·h).

Development of Sedative Dexmedetomidine Sublingual In Situ Gels: In Vitro and In Vivo Evaluations

Intravenous dexmedetomidine (DEX) is currently approved by the FDA for the sedation of intubated patients in intensive care units to reduce anxiety and to augment postoperative analgesia. Bradycardia and hypotension are limitations associated with the intravenous administration of DEX. In this study, DEX sublingual in situ gels were developed and assessed for their pH, gelling capacity, viscosity, mucoadhesion and in vitro drug release. The optimized gelling system demonstrated enhanced mucoadhesion, superior gelling capacity, reasonable pH and optimal rheological profile. In vivo, compared to the oral solution, the optimal sublingual gel resulted in a significant higher rate and extent of bioavailability. Although the in situ gel had comparable plasma levels to those observed following intravenous administration, significant amelioration of the systemic adverse reactions were attained. As demonstrated by the hot plate method, a sustained duration of analgesia in rats was observed after sublingual administration of DEX gel compared to the intravenously administered DEX solution. Furthermore, no changes in systolic blood pressure and heart rate were recorded in rats and rabbits, respectively, after sublingual administration of DEX. Sublingual administration of DEX in situ gel provides a promising approach for analgesia and sedation, while circumventing the reported adverse reactions associated with intravenous administration of DEX.

Acupuncture for postoperative delirium (POD): A systematic review and meta-analysis protocol

BACKGROUND

Postoperative delirium (POD) is a form of delirium that is newly diagnosed after a surgical procedure. This study aims to examine the effectiveness and safety of acupuncture treatment for POD in patients who underwent surgery.

METHODS

Randomized controlled trials for patients diagnosed with POD using validated delirium assessment scales will be included in this review. Electronic databases, such as MEDLINE, EMBASE, CENTRAL, CINAHL (English DB), CNKI, Wanfang, VIP (Chinese database), KoreaMed, RISS, KISS, DBpia, OASIS (Korean DB), and J-STAGE (Japanese DB) will be searched without language limitation from their inception to October 2020. The intervention group will include patients who have received any type of acupuncture treatment for POD. The control group will include individuals with no treatment, sham acupuncture treatment, and conventional treatment. The primary outcome is the incidence of POD in each study. Quality assessment will be performed using the Cochrane risk of bias tool. A meta-analysis will be performed to pool the estimated effect.

CONCLUSION

This study will provide evidence for acupuncture as a potential treatment for POD, in researchers, patients, and policy makers.

DISSEMINATION

The result of the study will be disseminated through posters, press releases, conference presentations, and peer-reviewed papers.

TRIAL REGISTRATION NUMBER

OSF 2020: (https://osf.io/usvdg).

Comparative efficacy and acceptability of pharmacological interventions for the treatment and prevention of delirium: A systematic review and network meta-analysis

We performed a network meta-analysis to build clear hierarchies of efficacy and tolerability of pharmacological interventions for the treatment and prevention of delirium. Electronic databases including PubMed, Google Scholar, Embase, Cochrane Central Register of Controlled Trials, PsycINFO, and MEDLINE were searched published up to February 22, 2019. A total of 108 randomized controlled trials (RCTs) investigating pharmacotherapy on delirium were included for analysis, and the strength of evidence (SoE) was evaluated for critical outcomes. In terms of treatment, quetiapine (low SoE), morphine (low SoE), and dexmedetomidine (moderate SoE) were effective in the intensive care unit (ICU) patients. In terms of prevention, dexmedetomidine (high SoE) and risperidone (high SoE) significantly reduced the incidence of delirium in ICU surgical patients, while ramelteon (high SoE) reduced the incidence of delirium in ICU medical patients. Despite the efficacy, dexmedetomidine and risperidone demonstrated higher drop-out rate (moderate to high SoE). Haloperidol and other antipsychotics, except for quetiapine and risperidone, showed no benefit. None of the agents showed benefit in non-ICU patients. In conclusion, dexmedetomidine may be a drug of choice for both treating and preventing delirium of the ICU and postsurgical patients. However, it may be less tolerable, and side-effects should be adequately managed. Current evidence does not support the routine use of antipsychotics. For medical patients, oral ramelteon might be useful for prevention.

Experimental study on the effects of isoflurane with and without remifentanil or dexmedetomidine on heart rate variability before and after nociceptive stimulation at different MAC multiples in cats

BACKGROUND

Heart rate variability (HRV) provides information about autonomic nervous system (ANS) activity and is therefore a possible tool with which to assess anaesthetic depth. The aim of the present study was to evaluate the effects of isoflurane, remifentanil and dexmedetomidine on HRV before and after nociceptive stimulation at different anaesthetic depths. Seven healthy domestic short-hair cats were used, and each cat was anaesthetized three times - group I with isoflurane alone, group IR with isoflurane and a constant rate infusion (CRI) of remifentanil (18 μg/kg/h), and group ID with isoflurane and a CRI of dexmedetomidine (3 μg/kg/h). Minimum alveolar concentration (MAC) values were determined via electrical supramaximal nociceptive stimulation for each treatment group. Nociceptive stimulation was repeated at 3 different MAC multiples (0.75, 1.0 and 1.5 MAC), and electrocardiographic recordings were performed for 3 min before and after stimulation. Only the 1 min epochs were used for further statistical analysis. Electrocardiographic data were exported for offline HRV analysis.

RESULTS

The mean isoflurane MAC ± standard deviation (SD) was 1.83 ± 0.22 vol% in group I, 1.65 ± 0.13 vol% in group IR and 0.82 ± 0.20 vol% in group ID. Nociception was indicated by several HRV parameters, however, with high variability between treatments. The best correlation with MAC was found for the SD of heart rate (STD HR) in group I (r_s = - 0.76, p = 0.0001, r² = 0.46). STD HR was also able to distinguish 0.75 MAC from 1.5 MAC and 1.0 MAC from 1.5 MAC in group I, as well as 0.75 MAC from 1.5 MAC in group ID.

CONCLUSIONS

The choice of anaesthetic protocol influences the HRV parameters in cats. Frequency domain parameters respond to nociception at lower MAC levels. The STD HR has the potential to provide additional information for the assessment of anaesthetic depth in isoflurane-anaesthetized cats. The utility of HRV analysis for the assessment of anaesthetic depth in cats is still questionable.

Dexmedetomidine: present and future directions

Dexmedetomidine is a potent, highly selective α-2 adrenoceptor agonist, with sedative, analgesic, anxiolytic, sympatholytic, and opioid-sparing properties. Dexmedetomidine induces a unique sedative response, which shows an easy transition from sleep to wakefulness, thus allowing a patient to be cooperative and communicative when stimulated. Dexmedetomidine may produce less delirium than other sedatives or even prevent delirium. The analgesic effect of dexmedetomidine is not strong; however, it can be administered as a useful analgesic adjuvant. As an anesthetic adjuvant, dexmedetomidine decreases the need for opioids, inhalational anesthetics, and intravenous anesthetics. The sympatholytic effect of dexmedetomidine may provide stable hemodynamics during the perioperative period. Dexmedetomidine-induced cooperative sedation with minimal respiratory depression provides safe and acceptable conditions during neurosurgical procedures in awake patients and awake fiberoptic intubation. Despite the lack of pediatric labelling, dexmedetomidine has been widely studied for pediatric use in various applications. Most adverse events associated with dexmedetomidine occur during or shortly after a loading infusion. There are some case reports of dexmedetomidine-related cardiac arrest following severe bradycardia. Some extended applications of dexmedetomidine discussed in this review are promising, but still limited, and further research is required. The pharmacological properties and possible adverse effects of dexmedetomidine should be well understood by the anesthesiologist prior to use. Moreover, it is necessary to select patients carefully and to determine the appropriate dosage of dexmedetomidine to ensure patient safety.

Cardiopulmonary effects of dexmedetomidine, with and without vatinoxan, in isoflurane-anesthetized cats

OBJECTIVE

To characterize the cardiopulmonary effects of dexmedetomidine, with or without vatinoxan, in isoflurane-anesthetized cats.

STUDY DESIGN

Randomized, crossover experimental study.

ANIMALS

A group of six adult healthy male neutered cats.

METHODS

Cats were instrumented during anesthesia with isoflurane in oxygen. Isoflurane end-tidal concentration was set to 1.25 minimum alveolar concentration (MAC). Dexmedetomidine was administered using a target-controlled infusion system to achieve and maintain 10 target plasma concentrations ranging from 0 to 40 ng mL^-1. Furthermore, vatinoxan or an equivalent volume of saline was administered using a target-controlled infusion system to achieve and maintain a target plasma concentration of 4 μg mL^-1. Isoflurane concentration was adjusted after each change in dexmedetomidine concentration to maintain a concentration equivalent to 1.25 MAC. Heart rate (HR), arterial blood pressure, central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary artery occlusion pressure (PAOP), body temperature, cardiac output, arterial and mixed-venous blood gas and pH and drug concentrations were measured. Additional variables were calculated from the measurements.

RESULTS

Dexmedetomidine alone resulted in decreased HR, cardiac index, stroke index and oxygen delivery, and increased systolic, mean (MAP) and diastolic arterial pressure, CVP, PAP, PAOP, systemic vascular resistance index, rate-pressure product, left ventricular stroke work index and oxygen extraction ratio. Vatinoxan resulted in severe hypotension at target plasma dexmedetomidine concentrations <10 ng mL^-1. Vatinoxan attenuated the cardiovascular effects of dexmedetomidine at the 10 and 20 ng mL^-1 targets, but MAP could be maintained above 60 mmHg only when isoflurane concentration was <1.25 MAC. Less improvement in cardiovascular function was seen with vatinoxan at the 40 ng mL^-1 target plasma dexmedetomidine concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Vatinoxan, at the plasma concentration maintained in this study, attenuated the cardiovascular effects of dexmedetomidine in isoflurane-anesthetized cats. However, its administration resulted in hypotension, which may limit its clinical usefulness.

Dexmedetomidine enhances glymphatic brain delivery of intrathecally administered drugs

Drug delivery to the central nervous system remains a major problem due to biological barriers. The blood-brain-barrier can be bypassed by administering drugs intrathecally directly to the cerebrospinal fluid (CSF). The glymphatic system, a network of perivascular spaces promoting fluid exchange between CSF and interstitial space, could be utilized to enhance convective drug delivery from the CSF to the parenchyma. Glymphatic flow is highest during sleep and anesthesia regimens that induce a slow-wave sleep-like state. Here, using mass spectrometry and fluorescent imaging techniques, we show that the clinically used α₂-adrenergic agonist dexmedetomidine that enhances EEG slow-wave activity, increases brain and spinal cord drug exposure of intrathecally administered drugs in mice and rats. Using oxycodone, naloxone, and an IgG-sized antibody as relevant model drugs we demonstrate that modulation of glymphatic flow has a distinct impact on the distribution of intrathecally administered therapeutics. These findings can be exploited in the clinic to improve the efficacy and safety of intrathecally administered therapeutics.

Effect of two different doses of dexmedetomidine on the incidence of emergence agitation after strabismus surgery: a randomized clinical trial

Background and objective

Emergence agitation is a postoperative negative behavior that affects mainly children. We studied the effect of two different doses of dexmedetomidine on the incidence and degree of EA in children undergoing strabismus surgery.

Methods

90 patients were allocated into three equal groups; patients received 0.5 μg.kg⁻¹ of dexmedetomidine in high Dex group, 0.25 μg.kg⁻¹ of dexmedetomidine in low Dex group, or normal saline in the placebo group. All drugs were received with the closure of the conjunctiva before the end of the surgery. Pediatric Anesthesia Emergence Delirium (PAED) scale was used to evaluate the agitation, and Face, Legs, Activity, Cry, Consolability (FLACC) scale was used for pain assessment. Adverse effects of dexmedetomidine and recovery times were recorded.

Results

The incidence of agitation was significantly lower in high Dex group compared to other groups and it was significantly lower in low Dex group compared to placebo group. The median (range) of FLACC score was significantly lower in both Dex groups compared to placebo group. Recovery times; time from removal of laryngeal mask to eye opening and time stay in post anesthesia care unit was significantly longer in high Dex group compared to other groups. No significant bradycardia or hypotension was recorded. Recovery time was significantly longer in high Dex group compared to the other two groups.

Conclusion

Dexmedetomidine (0.5 μg.kg⁻¹) before emergence from general anesthesia resulted in a reduction in the incidence of emergence agitation compared to a dexmedetomidine (0.25 μg.kg⁻¹) but on the expense of recovery times without adverse effects.

[Effect of two different doses of dexmedetomidine on the incidence of emergence agitation after strabismus surgery: a randomized clinical trial]

BACKGROUND AND OBJECTIVE

Emergence agitation is a postoperative negative behavior that affects mainly children. We studied the effect of two different doses of dexmedetomidine on the incidence and degree of EA in children undergoing strabismus surgery.

METHODS

90 patients were allocated into three equal groups; patients received 0.5μg.kg^-1 of dexmedetomidine in high Dex group, 0.25μg.kg^-1 of dexmedetomidine in low Dex group, or normal saline in the placebo group. All drugs were received with the closure of the conjunctiva before the end of the surgery. Pediatric Anesthesia Emergence Delirium (PAED) scale was used to evaluate the agitation, and Face, Legs, Activity, Cry, Consolability (FLACC) scale was used for pain assessment. Adverse effects of dexmedetomidine and recovery times were recorded.

RESULTS

The incidence of agitation was significantly lower in high Dex group compared to other groups and it was significantly lower in low Dex group compared to placebo group. The median (range) of FLACC score was significantly lower in both Dex groups compared to placebo group. Recovery times; time from removal of laryngeal mask to eye opening and time stay in post anesthesia care unit was significantly longer in high Dex group compared to other groups. No significant bradycardia or hypotension was recorded. Recovery time was significantly longer in high Dex group compared to the other two groups.

CONCLUSION

Dexmedetomidine (0.5μg.kg^-1) before emergence from general anesthesia resulted in a reduction in the incidence of emergence agitation compared to a dexmedetomidine (0.25μg.kg^-1) but on the expense of recovery times without adverse effects.

Impact of local administration of various doses of dexmedetomidine on ropivacaine-induced lumbar plexus-sciatic nerve block

The present study aimed to investigate the impact of various doses of dexmedetomidine (DEX) on ropivacaine (ROP)-induced lumbar plexus-sciatic nerve block (LSB). A total of 80 patients who underwent ankle surgery under LSB were divided into group R (applied with 30 ml 5% ROP), Dex1 (30 ml 0.5% ROP + 1 µg/kg DEX), Dex2 (30 ml 0.5% ROP + 1.5 µg/kg DEX) and Dex3 (30 ml 0.5% ROP + 2 µg/kg DEX), with 20 cases in each group. The onset time and duration of sensory and motor block, mean arterial pressure (MAP), heart rate (HR), oxygen saturation, Ramsay score, serum vascular endothelial growth factor (VEGF) level and adverse reactions in the four groups were observed. Results demonstrated that the durations of sensory and motor block in group R were shorter than those in groups Dex1-3 (P<0.01), followed by the sequence of group Dex1<Dex2<Dex3 (P<0.05). MAP and HR in groups Dex1-3 at T2-T5 were significantly lower than those in group R (P<0.01), and HR in group Dex3 at T3 and T4 was significantly lower than that in groups Dex1 and Dex2 (P<0.05). Ramsay scores in groups Dex1-3 at T2-T4 were significantly higher than those in group R (P<0.05). Serum VEGF levels in groups Dex2 and Dex3 at T2-T5 were significantly higher than those in group R (P<0.01). The incidences of over-sedation, bradycardia and dry mouth in group Dex3 were notably higher than those in the other groups. In conclusion, 1.5 µg/kg DEX exhibits a superior effect in improving ROP-induced LSB.

Feasibility of dexmedetomidine as sole analgesic agent during robotic urological surgery: A pilot study

BACKGROUND AND AIMS

Opioid-free anesthesia decreases postoperative nausea and vomiting, emergence agitation, prolonged sedation, ileus, and urinary retention. The feasibility of the use of dexmedetomidine as sole analgesic agent has been shown in patients undergoing bariatric and gynecological laparoscopic surgery. We explored its use for robotic urological surgery.

MATERIAL AND METHODS

Thirty patients were randomized to receive either dexmedetomidine (Group D) or fentanyl (Group F) along with total intravenous anesthesia with propofol. The hemodynamic parameters and number of doses of rescue analgesics used intraoperatively and postoperatively were noted. Recovery parameters at the end of surgery were also recorded.

RESULTS

The dose of intraoperative rescue fentanyl was not significantly different between groups (P = 0.13). The hemodynamic profile of patients in the two groups was comparable except the heart rate was significantly more in Group D after intubation and at 60 min. The mean arterial pressure was significantly lower after the initial loading dose of study drug in Group D. The recovery profiles were not significantly different between groups.

CONCLUSION

The study reveals that dexmedetomidine has equal analgesic efficacy as fentanyl for intraoperative use and can be used as the sole analgesic agent in patients undergoing robotic urological surgery.

Effect of dexmedetomidine on diseased coronary vessel diameter and myocardial protection in percutaneous coronary interventional patients

Introduction:

Dexmedetomidine is an alpha-2 agonist used for conscious sedation. It has also been shown to have a myocardial protective effect in off-pump coronary artery bypass patients. The aim of the study was to assess the effect of dexmedetomidine for myocardial protection in percutaneous coronary interventional patients.

Methodology:

A total of 60 patients (group dexmedetomidine, n = 30 and group normal saline, n = 30) were enrolled in the study. Dexmedetomidine infusion (1 mcg/kg) over 15 min was given as a loading dose after coronary angiography in group dexmedetomidine (D) while normal saline was given in the control group (C) and later maintenance infusion was started at 0.5 mcg/kg/h in both the groups. Coronary vessel diameter was noted before (T0) and after (T1) loading dose of dexmedetomidine/saline in each group. Troponin T (Trop T) values were noted at baseline (T0), 6 h (T2), 12 h (T3) and 24 h (T4) after starting the loading dose. Hemodynamic variables (heart rate [HR] and blood pressure) were monitored at T0, T1, and at regular intervals till 2 h postprocedure.

Results:

Coronary vessel diameter and HR significantly decreased in group D as compared to control group (P < 0.05) whereas the decrease in Trop T at 6 h, 12 h, and 24 h were not statistically significant between the two groups.

Conclusion:

Dexmedetomidine decreases the coronary vessel diameter, but maintains the myocardial oxygen demand-supply ratio by decreasing the HR. The decrease in Trop T is statistically insignificant at the doses used.

Intravenous Dexmedetomidine Infusion Compared with that of Fentanyl in Patients Undergoing Arthroscopic Shoulder Surgery under General Anesthesia

Background

Anesthesia for arthroscopic shoulder surgery is challenging due to the need for oligaemic surgical field as well as a good postoperative recovery profile.

Aim

The present study was prospective, randomized to evaluate the efficacy of dexmdetomidine infusion compared to that of fentanyl in patients undergoing arthroscopic shoulder surgery under general anesthesia.

Patients and Methods

A total of 60 patients aged from thirty to fifty years, American Society of Anesthesiologists Class I/II of either sex for arthroscopic shoulder surgery, were included. The patients were divided into two groups of 30 patients each. Group I received dexmedetomidine loading 1 μg/kg over 10 min followed by maintenance 0.5 μg/kg/h and Group II Fentanyl loading 1 μg/kg followed by maintenance 0.5 μg/kg/h.

Measurements

Hemodynamic readings (Heart rate HR, and mean arterial blood pressure MAP) were recorded after the start of the study drug infusion (T1), after intubation (T2), then every 15 minutes till the end of surgery (T15, T30, T45, T60, T75, T90). In the PACU, MAP, and HR were recorded on arrival, after 30 min, 1 hr, and 2 hrs (R0, R30, R1 hr, R2 hr) Postoperative analgesia was assessed by visual analogue scale (VAS), Modified Observers's Assessment of Alertness and Sedation OAA/S was recorded on arrival to PACU.

Results

This study showed that in the dexmedatomidine group there was statistically significant decrease of MAP and HR after drug infusion up to two hours in the recovery period, more sedation, better control of pain and surgeon satisfaction.

Conclusion

Iv infusion of dexamedatomidine may be an attractive option during arthroscopic shoulder surgery as it provided a better hypotensive anesthesia by lowering MAP and HR which leads to better surgical field and surgeon satisfaction than iv infusion fentanyl along with a better postoperative VAS.

Assessment of dexmedetomidine effects on left ventricular function using pressure-volume loops in rats

PURPOSE

The role of dexmedetomidine on left ventricular function is ambiguous. We analyzed pressure-volume loops to investigate whether dexmedetomidine has a myocardial depressive effect.

METHODS

Thirty-two Sprague-Dawley rats were anesthetized and a pressure-volume loop catheter was advanced into the left ventricle. Rats were divided into four groups (n = 8 each). The control group received a 10-min infusion of 0.1 ml of normal saline, and the other three groups received 1.0 (Dex1.0 group) , 2.5 (Dex2.5 group), and 5.0 μg/kg (Dex5.0 group) dexmedetomidine in a similar fashion to the control group. Steady-state hemodynamic parameters were recorded. The inferior vena cava was occluded intermittently to assess preload-independent indices.

RESULTS

Compared with the control group, changes in the Dex1.0 group were insignificant. In the Dex2.5 group, only the systolic blood pressure was higher (vs control, P = 0.03), and other parameters were insignificant. The Dex5.0 group exhibited a lower heart rate, higher systolic blood pressure, higher arterial elastance (vs control, all P < 0.001), and unaltered cardiac output. The Dex5.0 group showed steeper slopes of end-systolic pressure increment and end-systolic pressure-volume relationship than the control, Dex1.0, and Dex2.5 groups (all P < 0.001). Slopes of end-diastolic pressure decrement and end-diastolic pressure-volume relationship did not differ among groups.

CONCLUSION

Dexmedetomidine had no direct myocardial depressant effect in the rat heart in doses that are similar to those encountered under clinical conditions. Dexmedetomidine did not significantly alter the ability of the heart to cope with bradycardia and greatly increased afterload. Their potentially negative impact on cardiac output was effectively attenuated by improved myocardial contractility and preserved diastolic function in healthy subjects.

Attenuation of circulatory and airway responses to endotracheal extubation in craniotomies for intracerebral space occupying lesions: Dexmedetomidine versus lignocaine

OBJECTIVES

The objective of the study is to compare the effect of dexmedetomidine versus lignocaine in attenuation of circulatory and airway responses during endotracheal extubation in craniotomies for intracerebral space occupying lesions (ICSOL).

MATERIALS AND METHODS

A total of 50 patients of American Society of Anesthesiologists Grade I and II of either sex, aged 18-50 years undergoing craniotomies for non-vascular ICSOL under general anesthesia were divided into two groups according to drug received. Group D (n = 25) received dexmedetomidine (0.5 mcg/kg) whereas group L (n = 25) received lignocaine (1.5 mg/kg). Both the drugs were given 5 min before the extubation over a period of 60 s. Values for heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), were recorded just before (A0) and 1, 3, 5 (A1, A3, A5) min after the study drug administration, at extubation (E) and 1, 3, 5, 10, 15 min after extubation (E1, E3, E5, E10 and E15). Respiratory rate, oxygen saturation and airway responses like coughing, breath-holding, laryngospasm/bronchospasm were recorded only at extubation (E) and 1, 3, 5, 10, 15 min after extubation (E1, E3, E5, E10, E15). Quality of extubation was recorded with four point scale. After extubation all these patients were also observed for sedation by Ramsey sedation score.

RESULTS

Both groups showed a statistically significant increase (D < L) in HR, SBP and DBP during (E) and immediately after extubation (E1) (P < 0.05). Dexmedetomidine (72%) produced a higher degree of sedation (Grade 3) as compare with lignocaine (0%) and with no incidence of coughing or breath holding (P < 0.05).

CONCLUSION

Single dose of dexmedetomidine (0.5 mcg/kg) given 5 min before extubation produced significant attenuation of circulatory and airway responses produced during extubation as compared to Lignocaine (1.5 mg/kg) in ICSOL.

Vasovagal syncope and severe bradycardia following intranasal dexmedetomidine for pediatric procedural sedation

We report syncope and bradycardia in an 11-year-old girl following administration of intranasal dexmedetomidine for sedation for a voiding cystourethrogram. Following successful completion of VCUG and a 60-min recovery period, the patient's level of consciousness and vital signs returned to presedation levels. Upon leaving the sedation area, the patient collapsed, with no apparent inciting event. The patient quickly regained consciousness and no injury occurred. The primary abnormality found was persistent bradycardia, and she was admitted to the hospital for telemetric observation. The bradycardia lasted ~2 h, and further cardiac workup revealed no underlying abnormality. Unanticipated and previously unreported outcomes may be witnessed as we expand the use of certain sedatives to alternative routes of administration.

Protective effect of dexmedetomidine in coronary artery bypass grafting surgery

The aim of this study was to observe the impact of dexmedetomidine on postoperative myocardial injury in patients undergoing off-pump coronary artery bypass (OPCAB) grafting. One hundred and sixty-two patients who were undergoing OPCAB surgery were randomly divided into control and dexmedetomidine groups (groups C and Dex, respectively). Following the first vascular anastomosis grafting, the patients in group Dex received a continuous intravenous infusion of 0.2–0.5 μg/kg/h dexmedetomidine, until they were transferred to the Cardiac Surgery intensive care unit (ICU) for 12 h. Patients in group C received physiological saline intraoperatively and an intravenous infusion of 2–4 mg/kg/h isopropylphenol for postoperative sedation. Invasive arterial pressure and heart rate were continuously monitored for 5 min subsequent to entry into the operating theatre (T0), immediately following surgery (T1), 12 h post-surgery (T2), 24 h post-surgery(T3), 48 h post-surgery(T4) and 72 h post-surgery (T5). Blood samples were taken to determine the plasma levels of cardiac troponin I (cTnI) and creatine kinase-MB (CK-MB) at each time point. At 72 h post-surgery, a dynamic electrocardiogram was monitored. The blood pressure, heart rate, levels of cTnI, CK-MB, norepinephrine and cortisol, and postoperative arrhythmic events in the patients in group Dex all decreased compared with those in group C. The duration of mechanical ventilation and ICU residence time were also shorter than those in the control group (P<0.05). Dexmedetomidine reduced post-surgical myocardial injury in patients who had undergone OPCAB surgery.

Dexmedetomidine: current role in anesthesia and intensive care

BACKGROUND AND OBJECTIVES

To update and review the application of dexmedetomidine in anesthesia and intensive care. This study is a comprehensive review of clinical uses, pharmacology, pharmacokinetics, mechanism of action and adverse effects of dexmedetomidine.

CONTENT

The effective use of sedative-hypnotic agents and analgesics is an integral part of comfort and safety of patients. Dexmedetomidine is a potent and highly selective α-2 adrenoceptor agonist with sympatholytic, sedative, amnestic, and analgesic properties, which has been described as a useful and safe adjunct in many clinical applications. It provides a unique "conscious sedation", analgesia, without respiratory depression. The current reviewed uses include sedation at Intensive Care Unit-ICU (both adult and pediatric), emergency department, regional and general anesthesia, neurosurgery, sedation for pediatric procedures, awake fiber-optic intubation, cardiac surgery and bariatric surgery.

CONCLUSIONS

Dexmedetomidine offers a unique ability of providing both sedation and analgesia without respiratory depression. It is a new agent with a wide safety margin, excellent sedative capacity and moderate analgesic properties. Although its wide use is currently in patients of surgical and non-surgical intensive care units, dexmedetomidine seems to have promising future applications in neuroprotection, cardioprotection and renoprotection. More detailed studies are required to define its role as sedative in critical, neurosurgical and pediatric patients, as anesthesia adjunct and sedative during procedures.

Heart rate variability dynamics during low-dose propofol and dexmedetomidine anesthesia

Heart rate variability (HRV) has been observed to decrease during anesthesia, but changes in HRV during loss and recovery of consciousness have not been studied in detail. In this study, HRV dynamics during low-dose propofol (N = 10) and dexmedetomidine (N = 9) anesthesia were estimated by using time-varying methods. Standard time-domain and frequency-domain measures of HRV were included in the analysis. Frequency-domain parameters like low frequency (LF) and high frequency (HF) component powers were extracted from time-varying spectrum estimates obtained with a Kalman smoother algorithm. The Kalman smoother is a parametric spectrum estimation approach based on time-varying autoregressive (AR) modeling. Prior to loss of consciousness, an increase in HF component power indicating increase in vagal control of heart rate (HR) was observed for both anesthetics. The relative increase of vagal control over sympathetic control of HR was overall larger for dexmedetomidine which is in line with the known sympatholytic effect of this anesthetic. Even though the inter-individual variability in the HRV parameters was substantial, the results suggest the usefulness of HRV analysis in monitoring dexmedetomidine 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.

Safety and efficacy of dexmedetomidine in neurosurgical patients

PRIMARY OBJECTIVE

Very little information regarding effects on ICP, CPP and the safety of dexmedetomidine in neurosurgical patients has been published. The objective of this study is to gather information on the dosage, sedative effects and adverse effects of dexmedetomidine in neurosurgical patients.

RESEARCH DESIGN

The study design was retrospective and descriptive.

METHODS AND PROCEDURES

Computerized data were collected from the records of 39 neurosurgical patients in the ICU who received dexmedetomidine between October 2001 and December 2004. MAP, SBP, DBP, HR, ICP and CPP were recorded. The parameter means and standard deviations were obtained and plotted against time.

EXPERIMENTAL INTERVENTIONS

Dexmedetomidine, an alpha-2 agonist, provides adequate sedation without altering respiratory drive, while facilitating frequent neurological examinations. The FDA approved a dosage range for a loading infusion of 0.1 mcg kg-1 infused over 10 minutes followed by 0.2-0.7 mcg kg-1 h-1 continuous infusion for 24 hours.

MAIN OUTCOMES AND RESULTS

A total of 39 patients were enrolled in the study; 26 men and 13 women. The mean age was 34 years. Of the patients enrolled in the study, 15 were successfully extubated with no adverse reactions while maintaining adequate sedation. Agitation was the predominant adverse reaction. Hypotension occurred in 10 patients. The mean CPP increased and the mean ICP decreased. The standard deviation for the means of the ICP and CPP were small and did not fluctuate as widely as the haemodynamic parameters.

CONCLUSIONS

Dexmedetomidine can be a safe and effective sedative agent for neurosurgical patients. A loading infusion should be avoided and higher maintenance doses may be required to ensure adequate sedation. Further studies are necessary to establish an optimal dosage regimen.

Hemodynamic effects of dexmedetomidine sedation for CT imaging studies

BACKGROUND

Dexmedetomidine sedation for radiological imaging studies is a relatively recent application for this drug. Previous studies have demonstrated some haemodynamic effects of dexmedetomidine, however, the effects remain poorly described in children. The aim of this study was to better define the effect of age on heart rate (HR) and blood pressure changes in children sedated for CT imaging with dexmedetomidine.

METHODS/MATERIALS

At our institution dexmedetomidine is given for sedation for CT imaging as a bolus of 2 mcg.kg(-1) over 10 min followed by an infusion of 1 mcg.kg(-1).h(-1) with a second bolus if required. Detailed quality assurance data sheets document patient demographics, sedation outcomes, adverse events, and hemodynamic data are recorded for each patient.

RESULTS

A total of 250 patients (range 0.1-10.6 years) received dexmedetomidine. ANOVA revealed strong evidence for changes in HR and mean arterial blood pressure during bolus and infusion relative to presedation values (P < 0.001). These changes were apparent in each age group and similar between groups. During the first bolus and during infusion, 82% and 93% of patients respectively were within the age-based normal range for HR. For mean arterial blood pressure, 70% of patients were within the normal range during first bolus and 78% during infusion.

CONCLUSION

In the pediatric population studied, intravenous dexmedetomidine sedation was associated with modest fluctuations in HR and blood pressure. Hemodynamic changes were independent of age, required no pharmacologic interventions and did not result in any adverse events. By anticipating these possible hemodynamic effects and avoiding dexmedetomidine in those patients who may not tolerate such fluctuations in HR and blood pressure, dexmedetomidine is an appropriate sedative for children undergoing CT imaging.

A cardiovascular monitoring system used in conscious cynomolgus monkeys for regulatory safety pharmacology: Part 2: Pharmacological validation

INTRODUCTION

This project addresses the validation study design of a test system using a telemetered non-human primate model for cardiovascular safety pharmacology evaluation.

METHODS

In addition to non-pharmacological validation including installation and operation qualifications, performance qualification (locomotor activity and cardiovascular evaluations) was completed on free-moving cynomolgus monkeys by quantifying the degree of cardiovascular response measured by the telemetric device to various positive control drugs following their intravenous administration. Remifentanil (0.0005, 0.001, 0.002, 0.004, 0.008 and 0.016 mg/kg) was given to induce bradycardia and hypotension. Medetomidine (0.04 mg/kg) was used to induce an initial phase of hypertension followed by hypotension and bradycardia. Esmolol (0.5, 1.0 and 2.0 mg/kg) was used to induce bradycardia. Dopamine (0.002, 0.008, 0.01, 0.02, 0.03 and 0.05 mg/kg/min) was infused over 30 min to induce an increase in arterial and pulse pressures and tachycardia. Amiodarone (0.4, 0.8 and 1.6 mg/kg/min) was infused over 10 min to induce QT interval prolongation. Potassium chloride (0.08 mEq/kg/min) was infused for periods of less than 30 min to induce electrocardiographic (EKG) changes characteristic of hyperkalemia. Reliability was evaluated over 60 days.

RESULTS

Monitoring with a reference methodology and the telemetry system was important in order to evaluate precision and accuracy of the test system. Positive control drugs produced a wide range of cardiovascular effects with different amplitudes, which were useful in identification of the limits of the test system.

DISCUSSION

Reference monitoring methods and selection of a battery of positive control drugs are important to ensure proper test system validation. Drugs inducing not only QT prolongation but also positive and negative chronotropic effects, positive and negative systemic arterial pressure changes and ECG morphology alterations were useful to identify test system limitations during performance qualification. ECG data processing at significantly elevated heart rates revealed that a trained observer should review all cardiac cycles evaluated by computer.

Cardiovascular reactivity to mental stress is not affected by alpha2-adrenoreceptor activation or inhibition

RATIONALE

It has been postulated that cardiovascular reactivity to mental stress varies with tonic central sympathetic nervous system activity, but pharmacological evidence is missing.

OBJECTIVE

To test whether modulation of central sympathetic nervous system activity by alpha2-adrenergic agonism and antagonism affects cardiovascular reactivity to mental stress.

MATERIALS AND METHODS

On three five-stepped dose/concentration-response study days, 12 healthy male volunteers received intravenous infusions of dexmedetomidine (alpha2-agonist, target plasma concentrations: 0.04-0.32 ng/ml), yohimbine (alpha2-antagonist, doses: 0.016-0.125 mg/kg), and placebo, respectively. During each dose step, subjects performed a 5-Choice Reaction Time Task (CRTT) and a Paced Auditory Serial Addition Task (PASAT) to induce moderate mental stress. Prestress baseline, as well as stress-induced responses of heart rate, and noninvasive finger arterial blood pressure (Finapres) were assessed.

RESULTS

Prestress baseline heart rate and blood pressure decreased with increasing doses of dexmedetomidine and increased with increasing doses of yohimbine. However, dexmedetomidine and yohimbine did not affect stress-induced heart-rate and blood-pressure changes.

CONCLUSIONS

Cardiovascular reactivity to mental stress is not related to pharmacologically manipulated tonic central sympathetic nervous system activity by alpha2-adrenergic agonists and antagonists. These results do not support the assumption that cardiovascular reactivity is an index of tonic central sympathetic nervous system activity.

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.

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.

Anesthesia for Endovascular Neurosurgery

Endovascular neurosurgical procedures are complex, requiring significant planning, foresight, and coordination. The neuroanesthetist is an integral part of these procedures, organizing efforts of the technicians and nurses and responding to the needs of the neurointerventionalist. The purpose of this article is to review, in detail, the role of the neuroanesthetist in the endovascular operating room. An overview of all areas either partially or completely managed by the anesthetist is provided.

Analysis of rapid heart rate variability in the assessment of anticholinergic drug effects in humans

Anticholinergic agents have widespread therapeutic indications in clinical medicine. In addition, certain other drug groups-such as neuroleptics, antidepressants and antihistamines-possess distinct anticholinergic properties that reduce tolerance and compliance. Especially in patients with heart disease, attention should be paid to cardiac anticholinergic drug effects. The analysis of short-term heart rate variability (HRV) provides a noninvasive tool to estimate vagal cholinergic outflow. In this review article, we present the basic principles of the most relevant techniques to study rapid HRV: the time domain analysis methods RMSSD and pNN50, and the high-frequency (HF) spectral component of HRV. We provide examples of previously reported effects of anticholinergic agents on these measures and also describe how adrenergic drugs may influence them. We have the following recommendations for a clinical pharmacologist investigating anticholinergic agents. (1) If the breathing rate of the study subject can be controlled during the assessment and the electrocardiogram recordings contain good-quality, stationary segments that are at least a few minutes long, then the HF power of HRV should be the method of choice. (2) During uncontrolled conditions, RMSSD should be included in the analyses, because it is less affected by changes in the respiratory pattern and it can be measured from shorter segments of electrocardiogram data. (3) Reduced short-term HRV suggests an anticholinergic, but not necessarily an antimuscarinic drug effect, since the inhibition of cholinergic vagal efferent activity may also originate from central or peripheral adrenergic influences.

Dexmedetomidine in anaesthesia

PURPOSE OF REVIEW

The development of dexmedetomidine, a potent and highly selective alpha2-adrenoceptor agonist, has created new interest in the use of alpha2-adrenoceptor agonists, and has led to its evaluation in various yet non-approved perioperative settings. The current review focuses on the usefulness of dexmedetomidine in anaesthesia practice.

RECENT FINDINGS

Recently acquired knowledge and experience with dexmedetomidine in perioperative use will be presented and discussed in the context of known pharmacological properties.

SUMMARY

Dexmedetomidine offers beneficial pharmacological properties, providing dose-dependent sedation, analgesia, sympatholysis and anxiolysis without relevant respiratory depression. The side-effects are predictable from the pharmacological profile of (2-adrenoceptor agonists. In particular, the unique sedative properties of dexmedetomidine resulted in several interesting applications in anaesthesia practice, promising benefits in the perioperative use of this compound. However, dexmedetomidine was approved for sedation in the intensive care unit in the USA in 1999, and administration in anaesthesia practice remains an 'off-label' use. Further studies are needed to establish the role of dexmedetomidine in the perioperative period.

Effects of atipamezole--a selective alpha-adrenoceptor antagonist--on cardiac parasympathetic regulation in human subjects

1 This double-blind, cross-over, placebo-controlled study on six healthy male volunteers was designed to evaluate the effects of alpha2-adrenoceptor antagonism on cardiac parasympathetic regulation. 2 The subjects received atipamezole intravenously as a three-step infusion, which aimed at steady-state serum concentrations of 10, 30 and 90 ng ml(-1) at 50-min intervals. 3 Drug effects were assessed with repeated recordings of blood pressure and electrocardiogram, in which the high-frequency (0.15-0.40 Hz) R-R interval variation is supposed to reflect cardiac parasympathetic efferent neuronal activity. 4 At the end of the three steps of the infusion, the mean (+/-SD) concentrations of atipamezole were 10.5 (3.9), 26.8 (5.6) and 81.3 (21.1) ng ml(-1). 5 Within this concentration range, atipamezole appeared to reduce slightly the high-frequency R-R interval fluctuations, indicating a minor vagolytic effect in the heart. 6 Atipamezole increased systolic and diastolic arterial pressure, on average by 20 and 14 mmHg (maxima at the second step of the infusion), which evidently reflects an overall sympathetic augmentation.