Initial experience with dexmedetomidine for diagnostic and interventional cardiac catheterization in children

BACKGROUND: Children undergoing diagnostic and interventional cardiac catheterization require deep sedation or general anesthesia (GA). Dexmedetomidine, a selective alpha-2 adrenergic agonist, has sedative, analgesic and anxiolytic properties without respiratory depression. These characteristics make it potentially suitable as a sedative agent during diagnostic procedures in children. We report our experience using dexmedetomidine in 20 children aged 3 months to 10 years undergoing cardiac catheterization. METHODS: Following a midazolam premedication, intravenous access was secured facilitated by the inhalation of sevoflurane in oxygen. A loading dose of 1 microg x kg(-1) dexmedetomidine was administered over 10 min followed by an initial infusion rate of 1 microg x kg(-1) x h(-1). Nasal cannulae were applied, allowing endtidal CO2 monitoring with the patients breathing spontaneously. Hemodynamic parameters, Bispectral Index Score (BIS) and sedation score were measured every 5 min. Patient movement or evidence of inadequate sedation were treated with propofol (1 mg x kg(-1)). The dexmedetomidine infusion rate was titrated to the level of sedation to a maximum of 2 microg x kg(-1) x h(-1) to maintain a sedation score of 4-5 and a BIS value <80. RESULTS: Five patients (25%) had some movement on local infiltration or groin vessel access. This did not necessitate restraint or result in difficulty securing vascular access. No patients failed sedation that required the addition of another sedative agent or conversion to GA; eight patients were sedated with dexmedetomidine alone; however, 12 (60%) patients did receive a propofol bolus at some time during the procedure due to movement, increasing BIS value or in anticipation of stimulation. There were no incidences of airway obstruction or respiratory depression. In all cases the heart rate and blood pressure remained within 20% of baseline. No patient required treatment for profound bradycardia or hypotension. The average infusion rate for dexmedetomidine following the loading dose was 1.15 (+/-0.29)microg x kg(-1) x h(-1) (range 0.6-2.0 microg x kg(-1) x h(-1)). CONCLUSIONS: This initial experience showed dexmedetomidine, with or without the addition of propofol, may be a suitable alternative for sedation in spontaneously breathing patients undergoing cardiac catheterization.     

Experience in postoperative sedation with dexmedetomidine for mandibular osteotomy

BACKGROUND: Dexmedetomidine may be suitable for postoperative sedation of patients with mandibular osteotomy. METHODS: Twenty patients were sedated with dexmedetomidine (group D) employing loading infusion at 1.0 microg x kg(-) x hr(-1) and then continuous infusion at 0.7 mg x kg(-1) x hr(-1). Other twenty patients were sedated with midazolam 0.1 mg x kg(-1) (group C). Ramsay score was recorded at 3 hours and 12 hours after infusing sedative drugs. Then, we questioned patients, nurses and doctors. RESULTS: Ramsay score in the group D was higher than that in the group C (P < 0.01). Hypotension and respiratory depression did not occur. But bradycardia occurred in two cases. By adding propofol, group D showed more effective sedation. CONCLUSIONS: This study shows that sedation with dexmedetomidine is more suitable than that with midazolam.     

右美托咪定和丙泊酚用于硬膜外麻醉下妇科手术患者镇静的比较

目的 比较右美托咪定(Dex)和丙泊酚用于硬膜外麻醉下妇科手术患者的镇静效果.方法 硬膜外麻醉下择期行子宫或(和)卵巢切除患者100例,随机均分成Dex组(D组)和丙泊酚组(P组),应用Ramsay镇静评分和脑电双频指数(BIS)对两组患者术中镇静效果进行观察.记录给药前(T0)、切皮前即给药后15 min(T1)、手术开始后15 min(T2)、30 min(T3)、45 min(T4)、术毕(T5)及术后1 h(T6)患者HR、MAP、BIS、Ramsay镇静评分及呼吸抑制情况.结果 T1～T5时D组BIS,MAP明显低于T0时和P组,Ramsay镇静评分低于P组,HR慢于T0时和P组(P<0.05).低血压的发生率P组明显高于D组(P<0.05).结论 Dex用于硬膜外麻醉下妇科手术患者镇静是安全和可行的.     

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.     

右美托咪啶与异丙酚镇静下允许性高碳酸血症患者颅内压及脑氧代谢的比较

目的 比较右美托咪啶与异丙酚镇静下允许性高碳酸血症患者的颅内压及脑氧代谢情况.方法行允许性高碳酸血症通气、Ramsay评分≤2分的急性呼吸窘迫综合征患者24例,年龄28～64岁,APACHE-Ⅱ评分11～18分,采用随机数字表法,将患者随机分为2组(n=12):右美托咪啶组(D组)和异丙酚组(P组).调节右美托咪啶输注速率或异丙酚血浆靶浓度使D组和P组患者Ramsay评分逐步达到3、4、5分.于给药前(T0)、达各目标镇静水平后30 min(T1～3)时采用经颅多普勒超声测定大脑中动脉脑血流速率(CBFW)、搏动指数(PI)和阻力指数(RI),抽取桡动脉血样和颈内静脉球部血样行血气分析,计算脑氧代谢率(CNRO2)、动脉-颈内静脉氧含量差(Da-jvO2)、脑氧摄取率(CERO2).结果 与T0时比较,D组和P组T1～3时MAP、BIS值、CBFV、PI、RI和CMRO2降低(P＜0.05或0.01);两组各时点Da-jvO2、CERO2差异无统计学意义(P＞0.05);与P组比较,D组各时点BIS值和MAP差异无统计学意义(P＞0.05),CBF、PI和RI降低(P＜0.05).D组和P组CBFV与CMRO2均呈正相关(相关系数分别为0.80、0.76,P＜0.05).结论 在不同镇静水平,右美托咪啶较异丙酚可明显降低允许性高碳酸血症患者的颅内压,且可保持脑氧供需平衡.

Abstract：

Objective To compare the effects of sedation induced with dexmedetomidine and propofol on intracranial pressure and cerebral oxygen metabolism in patients with permissive hypercapnia. Methods Twentyfour patients with acute respiratory distress syndrome (ARDS) were randomly divided into 2 groups ( n = 12 each) :dexmedetomidine group (group D) and propofol group (group P) . Their APACHE Ⅱ scores were 11-18. The patients were mechanically ventilated (VT 5-7 ml/kg, RR 12-17 bpm, PEEP 6-10 cm H2O, FiO2 40-60%). PaCO2 was maintained at 50-65 mm Hg. Radial artery was cannulated for direct BP monitoring and blood sampling. Right internal jugular vein was cannulated and the catheter was advanced cephalad until jugular bulb. Continuous infusion of dexmedetomidine was started at 0.5 μg· kg-1· h-1 and TCI of propofol was started at target plasma concentration (Cp) of 0.4 μg/ml. The infusion of both drugs was gradually increased until Ramsay score (1= fully awake, 6 =asleep, unresponsive to loud verbal stimulus) reached 3,4,5. Transcranial Doppler monitoring was used to determine cerebral blood flow velocity (CBFV), pulsatility index (PI) and resistance index (RI) before administration of dexmedetomidine and propofol (T0 ) and at 30 min after the 3 levels of sedation were reached (T1-3) . Meanwhile blood samples were taken from radial artery and jugular bulb for blood gas analyses. Cerebral O2 metabolic rate (CMRO2), cerebral A-V O2 content differences (Da-jvO2) and cerebral O2 extraction rate (CERO2) were calculated .ResultsCBFV, PI, RI and CMRO2 were significantly decreased at T1-3 as compared with the baseline values at T0 in both groups. CBFV was positively correlated with CMRO2 in both group D (r = 0.80) and group P ( r = 0.76) . CBFV, PI and RI were significantly lower at T1-3 in group D than in group P. There was no significant change in Da-jvO2 and CERO2 at T1-3 as compared with the baseline values at T0 in both groups. Conclusion At different sedation levels, dexmedetomidine results in lower intracranial pressure than propofol and maintains the balance between cerebral O2 supply and demand in patients with permissive hypercapnia.     

右美托咪定复合小剂量氯胺酮在困难气道纤维支气管镜插管中镇静遗忘的效果

目的观察右美托咪定复合小剂量氯胺酮在择期手术困难气道患者纤维支气管镜经鼻气管插管中的镇静遗忘的效果。方法择期困难气道纤维支气管镜经鼻插管患者90例,ASAⅠ或Ⅱ级,按照随机数字表法均分为三组:右美托咪定1.0μg/kg+氯胺酮0.5 mg·kg-1·h-1(DK组)、右美托咪定1.0μg/kg+丙泊酚2.0mg·kg-1·h-1(DP组)和右美托咪定1.0μg/kg+瑞芬太尼5.0μg·kg-1·h-1(DR组)。比较三组患者入室后安静10min(T0)、纤维支气管镜置入前(T1)、气管导管进入声门即刻(T2)及插管后5min(T3)时HR、MAP、SpO2及Ramsay镇静评分和不良反应,及术后24h随访患者对气管插管过程的知晓情况。结果与T0时比较,T1时DP和DR组HR明显减慢,MAP明显下降,T1时DP组SpO2明显降低(P0.05);T3时DP和DR组HR明显加快,DR组MAP明显增高(P0.05);T2时DR组MAP明显高于DP组。T2时DP组和DR组Ramsay镇静评分明显低于DK组,T3时DR组Ramsay镇静评分明显低于DK和DP组(P0.05);DP组心动过缓、呼吸抑制发生率明显高于DK组,DR组呛咳、躁动、心动过速、插管知晓发生率明显高于DK组(P0.05)。结论右美托咪定复合小剂量氯胺酮用于困难气道患者经鼻纤支镜插管可保证良好的镇静遗忘效果,维持稳定的血流动力学,并且不良反应发生率低。     

Monitored anesthesia care with a combination of ketamine and dexmedetomidine during magnetic resonance imaging in three children with trisomy 21 and obstructive sleep apnea

We present a series of three children with trisomy 21 and obstructive sleep apnea who required sedation during magnetic resonance imaging of the upper airway. In an effort to provide effective sedation with limited effects on cardiovascular and ventilatory function, sedation was provided by a combination of ketamine and dexmedetomidine. Sedation was initiated with a bolus dose of ketamine (1 mg x kg(-1)) and dexmedetomidine (1 microg x kg(-1)) and maintained by a continuous infusion of dexmedetomidine (1 microg x kg(-1) x h(-1)). One patient required a repeat of the bolus doses of ketamine and dexmedetomidine and an increase of the dexmedetomidine infusion to 2 microg x kg(-1) x h(-1). Effective sedation was provided for all three patients. We noted no clinically significant hemodynamic or respiratory effects. No central apnea was noted although there was a brief episode of upper airway obstruction in one patient which responded to repositioning of the airway. All three patients developed some degree of hypercarbia with maximum P(E)(CO2) values of 6.4, 6.9, and 6.8 kPa (49, 53, and 52 mmHg), respectively. To date, this is the first report regarding the use of this combination in pediatric patients. Given the preliminary success noted in our three patients, prospective trials evaluating the efficacy of a dexmedetomidine-ketamine combination appears warranted.     

Dexmedetomidine for sedation during electroencephalographic analysis in children with autism, pervasive developmental disorders, and seizure disorders

STUDY OBJECTIVE: To assess the efficacy of dexmedetomidine in providing sedation during electroencephalographic (EEG) analysis in children with autism, seizure disorders, or pervasive developmental disorders (PDDs). DESIGN: Retrospective chart review. SETTING: University medical center. MEASUREMENTS: The charts of 42 children, aged two to 11 years, who received dexmedetomidine for sedation during EEG analysis, were studied. Information collected included route of administration of dexmedetomidine (oral and/or intravenous [IV]), loading dose, and infusion rate. Heart rate, blood pressure, respiratory rate, and level of sedation were monitored every 5 minutes, and oxygen saturation was monitored continuously during the procedure. Interventions (administration of fluid or use of an anticholinergic agent) for hypotension or bradycardia were identified. MAIN RESULTS: 18 children received oral dexmedetomidine (range, 2.9-4.4 mug/kg) before placement of an IV. Forty patients received an IV loading dose of dexmedetomidine (2.1 +/- 0.8 mug/kg), which was given in increments of 0.5 to one mug/kg every three to 5 minutes until a sedation score of 3 to 4 was achieved. Effective sedation was eventually achieved in all patients. An IV infusion of dexmedetomidine was started (1.5 +/- 0.2 mug kg(-1) hr(-1)) in all patients. During performance of the EEG, adjustments in the infusion rate (increase or decrease) or additional bolus doses were necessary in 25 patients. No significant hemodynamic or respiratory effects were noted. CONCLUSIONS: Dexmedetomidine provides effective sedation during EEG analysis in children with autism or PDD.     

Rescue sedation with dexmedetomidine for diagnostic imaging: a preliminary report

BACKGROUND: Sedation is frequently required during noninvasive radiological imaging in children. Although commonly used agents such as chloral hydrate and midazolam are generally effective, failures may occur. The authors report their experience with dexmedetomidine for rescue sedation during magnetic resonance imaging. METHODS: A retrospective chart review was undertaken. RESULTS: The cohort included five patients ranging in age from 11 months to 16 years. Following the failure of other agents (chloral hydrate and/or midazolam), dexmedetomidine was administered as a loading dose of 0.3-1.0 microg x kg(-1) x min(-1) over 5-10 min followed by an infusion of 0.5-1.0 microg x kg(-1) x h(-1). The dexmedetomidine loading dose required to induce sedation was 0.78 +/- 0.42 microg x kg(-1) (range 0.3-1.2). The maintenance infusion rate was 0.57 +/- 0.06 microg x kg(-1) x h(-1) (range 0.48-0.69). The imaging procedures were completed without difficulty. No patient required additional bolus administrations or changes in the infusion rate. The duration of the dexmedetomidine infusion ranged from 30 to 50 min. The mean decrease in heart rate was 13.6 +/- 5.1 b x min(-1) (14.3 +/- 5.0% from baseline; P = 0.02), the mean decrease in systolic blood pressure was 26.4 +/- 15.2 mmHg (24.6 +/- 12.4% decrease from baseline; P = 0.004), and the mean decrease in respiratory rate was 1.4 +/- 1.5 min(-1) (7.5 +/- 7.9% decrease from baseline; P = NS). P(E)CO2 exceeded 6.5 kPa (50 mmHg) in one patient [maximum 6.6 kPa (51 mmHg)] with a maximum value of 6.0 +/- 0.4 kPa (46 +/- 3 mmHg). Oxygen saturation decreased from 98 +/- 1 to 95 +/- 1%; P = 0.001. No patient developed hypoxemia (oxygen saturation less than 90%). Mean time to recovery to baseline status was 112.5 +/- 50.6 min and time to discharge was 173.8 +/- 83.8 min. CONCLUSIONS: Our preliminary experience suggests that dexmedetomidine may be an effective agent for procedural sedation during radiological imaging. Its potential application in this setting is discussed and other reports regarding its use in pediatric patients are reviewed.     

Sedative, amnestic, and analgesic properties of small-dose dexmedetomidine infusions

This research determined the safety and efficacy of two small-dose infusions of dexmedetomidine by evaluating sedation, analgesia, cognition, and cardiorespiratory function. Seven healthy young volunteers provided informed consent and participated on three occasions with random assignment to drug or placebo. Heart rate, blood pressure, respiratory rate, ETCO(2), O(2) saturation, and processed electroencephalogram (bispectral analysis) were monitored. Baseline hemodynamic measurements were acquired, and psychometric tests were performed (visual analog scale for sedation; observer's assessment of alertness/sedation scale; digit symbol substitution test; and memory). The pain from a 1-min cold pressor test was quantified with a visual analog scale. After a 10-min initial dose of saline or 6 microg. kg(-1). h(-1) dexmedetomidine, volunteers received 50-min IV infusions of saline, or 0.2 or 0.6 microg. kg(-1). h(-1) dexmedetomidine. Measurements were repeated at the end of infusion and during recovery. The two dexmedetomidine infusions resulted in similar and significant sedation (30%-60%), impairment of memory (approximately 50%), and psychomotor performance (28%-41%). Hemodynamics, oxygen saturation, ETCO(2), and respiratory rate were well preserved throughout the infusion and recovery periods. Pain to the cold pressor test was reduced by 30% during dexmedetomidine infusion. Small-dose dexmedetomidine provided sedation, analgesia, and memory and cognitive impairment. These properties might prove useful in a postoperative or intensive care unit setting. IMPLICATIPNS: The alpha(2) agonist, dexmedetomidine, has sedation and analgesic properties. This study quantified these effects, as well as cardiorespiratory, memory and psychomotor effects, in healthy volunteers. Dexmedetomidine infusions resulted in reversible sedation, mild analgesia, and memory impairment without cardiorespiratory compromise.     

Sole use of dexmedetomidine has limited utility for conscious sedation during outpatient colonoscopy

BACKGROUND: This study evaluated the ability of dexmedetomidine to provide analgesia and sedation for outpatient colonoscopy, examining outcomes including cardiorespiratory variables, side effects, and discharge readiness. METHODS: Sixty-four patients were randomly assigned to one of three treatment regimens. In group D, patients received 1 microg/kg dexmedetomidine over 15 min followed by an infusion of 0.2 microg x kg x h. Group P received meperidine (1 mg/kg) with midazolam (0.05 mg/kg), and group F received fentanyl (0.1-0.2 mg intravenous) on demand. The assessment included measurements of heart rate, blood pressure, oxygen saturation, respiratory rate, quality of sedation/analgesia, and an evaluation of the recovery time. RESULTS: The study was terminated before the planned 90 patients had been recruited because of adverse events in group D. In all groups, negligible hemoglobin oxygen saturation and respiratory rate variations were observed. In group D, there was a significantly larger decrease in heart rate (to approximately 40 beats/min in 2 of 19 cases) and blood pressure (to less than 50% of the initial value in 4 of 19 patients). Supplemental fentanyl was required in 47% of patients receiving dexmedetomidine to achieve a satisfactory level of analgesia (vs. 42.8% of patients in group P and 79.2% of patients in group F). Vertigo (5 patients), nausea/vomiting (5 patients), and ventricular bigeminy (1 patient) were observed only in group D. Time to home readiness was longest in group D (85 +/- 74, 39 +/- 21, and 32 +/- 13 min in groups D, P and F, respectively; P = 0.007). CONCLUSIONS: The use of dexmedetomidine to provide analgesia/sedation for colonoscopy is limited by distressing side effects, pronounced hemodynamic instability, prolonged recovery, and a complicated administration regimen.     

不同速率输注右美托咪定对老年白内障手术患者的镇静效应

目的 观察不同速率输注右美托咪定对老年白内障手术患者球后神经阻滞麻醉下的镇静效应.方法 选择90例60～80岁白内障手术患者,根据应用右美托咪定维持剂量随机均分为右美托咪定Ⅰ组(0.2μg·kg-1·h-1)、Ⅱ组(0.4μg·kg-1·h-1)、Ⅲ组(0.6 μg·kg-1 ·h-1).观察并记录三组患者麻醉前(T0)、神经阻滞完毕即刻(T1)、用药后10 min(T2)、20 min(T3)、30 min(T4)、60 min(T5)的Ramsay评分和MAP、HR、RR、SpO2.结果 T2～T5时各组Ramsay评分高于T0时(P＜0.05),T3～T5时Ⅲ组高于Ⅰ组(P＜0.05).T3～T5时三组HR显著慢于T0时(P＜0.05),以Ⅲ组减慢最明显;T3～T5时三组RR均慢于T0时,但差异无统计学意义;三组间MAP、SpO2差异无统计学意义.结论 静注右美托咪定0.5 μg/kg后以0.2～0.4 μg·kg- 1·h-1维持适合老年白内障手术患者的清醒镇静.     

Dexmedetomidine-ketamine and propofol-ketamine combinations for anesthesia in spontaneously breathing pediatric patients undergoing cardiac catheterization

OBJECTIVE: The purpose of this study was to compare the effects of dexmedetomidine-ketamine and propofol-ketamine combinations on hemodynamics, sedation level, and the recovery period in pediatric patients undergoing cardiac catheterization. DESIGN: Prospective, randomized trial. SETTING: University hospital. PARTICIPANTS: Children (n = 44) undergoing cardiac catheterization. INTERVENTIONS: The dexmedetomidine plus ketamine group (group 1, n = 22) received an infusion over 10 minutes of 1 microg/kg of dexmedetomidine and ketamine, 1 mg/kg, as a bolus, for induction. The patients then received an infusion of 0.7 microg/kg/h of dexmedetomidine and 1 mg/kg/h of ketamine for maintenance. The propofol plus ketamine group (group 2, n = 22) received 1 mg/kg of propofol and 1 mg/kg of ketamine for induction. The patients received 100 microg/kg/min of propofol and 1 mg/kg/h of ketamine by infusion for maintenance. Additional doses of ketamine, 1 mg/kg, were administered when a patient showed discomfort in both groups. MEASUREMENTS AND MAIN RESULTS: Hemodynamic data, respiratory rate, bispectral index, and sedation scores were recorded after induction and every 15 minutes thereafter. The time to reach a Steward recovery score of 6 was recorded. The heart rate in group 1 was significantly lower (average 10-20 beats/min) than group 2 after induction and throughout the procedure. Ketamine consumption in group 1 was significantly more than in group 2 (2.03 mg/kg/h v 1.25 mg/kg/h) for maintenance (p < 0.01). The recovery time was also longer in group 1 than in group 2 (49.54 v 23.16 minutes, respectively; p < 0.01). CONCLUSIONS: The dexmedetomidine-ketamine combination was not superior to a propofol-ketamine combination because of insufficient sedation and analgesia and a longer recovery time.     

小剂量右美托咪定联合丙泊酚用于小儿门诊核磁共振检查镇静的临床研究

目的评价小剂量右美托咪定联合丙泊酚用于小儿门诊核磁共振检查（MRI）镇静的临床应用。 方法选取2019年1月至3月在广州市妇女儿童医疗中心行门诊MRI需要镇静的患儿300例，随机分为三组：水合氯醛镇静组（H组，口服10%水合氯醛镇静）；丙泊酚静脉镇静组（P组，静脉推注丙泊酚镇静）；小剂量右美托咪定联合丙泊酚静脉镇静组（DP组，右美托咪定0.3 μg/kg+丙泊酚静脉镇静），各100例。比较三组患者的镇静成功率，镇静效果，呕吐、躁动发生率，呼吸抑制率。 结果P组及DP组的镇静成功率明显高于H组（χ²=18.560，P<0.001），呕吐、躁动发生率明显低于H组（χ²=54.224、17.023，P<0.001、0.001），三组呼吸抑制发生率及需要呼吸支持例数差异无统计学意义（χ²=1.049、1.798，P=0.591、0.407）。DP组需追加丙泊酚例数明显少于P组（χ²=67.520，P<0.001）。镇静过程中，P组及DP组镇静起效时间、苏醒时间、苏醒至离院时间明显短于H组（F=634.100、243.800、42.930，P<0.001、<0.001、<0.001）。 结论小剂量右美托咪定联合丙泊酚静脉镇静用于小儿门诊MRI检查，具有起效快、不良反应少、安全性高、苏醒快等优点，可在小儿门诊镇静推广应用。     

Efficacy of dexmedetomidine for controlling delirium in intensive care unit patients

BACKGROUND: We have examined the effect of dexmedetomidine, a selective alpha2-adrenoreceptor agonist, for controlling delirium in patients in the intensive care unit. METHODS: Intravenous infusion of dexmedetomidine (0.05-0.40 microg kg(-1) hr(-1)) was started at the onset of delirium, and its effect on sedation levels, circulation and respiration was examined in 111 patients. RESULTS: Nine patients were excluded from the study because of insufficient sedation and development of bradycardia requiring additional sedatives and discontinuance of dexmedetomidine infusion, respectively. The mean Ramsay score was 1.5 before starting dexmedetomidine (baseline), which was significantly increased to 3.2 4 hours after starting dexmedetomidine infusion (n=102). Heart rate and systolic arterial blood pressure significantly decreased 6 hours after starting dexmedetomidine compared with baseline. There were no differences in respiratory rate during infusion of dexmedetomidine. In 30 patients with hypoxemia (Pa(O2)/ Fi(O2) (P/F) ratio<300), respiratory rate, tidal volume, arterial blood gas data and P/F ratio were not affected by dexmedetomidine. CONCLUSIONS: Dexmedetomidine is effective for controlling delirium and provides sufficient sedation without respiratory adverse effects in patients in the intensive care unit. It is also effectively and safely used in patients with respiratory failure.     

Electroencephalograph variables, drug concentrations and sedation scores in children emerging from propofol infusion anaesthesia

BACKGROUND: Inadequate sedation or oversedation are common problems in Paediatric Intensive Care because of wide variations in drug response and the lack of objective tests for sedative depth. We undertook a pilot study to try to identify correlates of propofol drug concentration, electroencephalographic (EEG) variables and observed behaviour during a stepwise reduction in propofol infusion after paediatric cardiac surgery. METHODS: This was a prospective pilot study with 10 children (5 months to 8 years) emerging from propofol anaesthesia following cardiac surgery with cardiopulmonary bypass (CPB). Patients underwent a stepped wake-up from propofol anaesthesia during which the propofol infusion rate was decreased from 4 mg.kg(-1).h(-1) in 1 mg.kg(-1).h(-1) steps at 30 min intervals. EEG variables, propofol blood concentrations and clinical sedation scores (COMFORT scale) were recorded during the stepped wakeup. Analgesia was maintained with a standardized continuous infusion of fentanyl. RESULTS: : Mean (SD) whole blood propofol concentrations at arousal varied considerably [973 ng.ml(-1) (SD 523 ng.ml(-1))]. The summed ratio (SR) of high frequency to low frequency bands correlated with both propofol infusion rate (R2 value=0.47) and propofol blood concentrations (R2 value=0.64). The mean SR in deeply sedated patients was significantly different from that in the 5 min prior to wakening (6.84 vs 1.55, P=0.00002). There was no relationship between COMFORT scores and SR. CONCLUSIONS: In this group of patients receiving opioid analgesia and relatively high doses of propofol, sedation scores were unhelpful in predicting arousal. The SR correlated with propofol blood concentrations and clinical arousal and may have potential as a predictive tool for arousal in children.     

Dexmedetomidine decreases the convulsive potency of bupivacaine and levobupivacaine in rats: involvement of alpha2-adrenoceptor for controlling convulsions

Dexmedetomidine, a highly selective alpha(2)-adrenoceptor agonist, is used in combination with local anesthetics for sedation and analgesia. We tested the hypothesis that dexmedetomidine used for sedation alters the convulsive potency of racemic bupivacaine and levobupivacaine in awake, spontaneously breathing rats. In the first experiments, male Sprague-Dawley rats were randomly divided into six groups: bupivacaine with no dexmedetomidine (bupivacaine control; BC), bupivacaine with small-dose dexmedetomidine (BS), bupivacaine with large-dose dexmedetomidine (BL), levobupivacaine with no dexmedetomidine (levobupivacaine control; LC), levobupivacaine with small-dose dexmedetomidine (LS), and levobupivacaine with large-dose dexmedetomidine (LL) (n = 10 for each group). Continuous infusion of dexmedetomidine (Groups BC and LC, 0 microg x kg(-1) x h(-1); Groups BS and LS, 3.6 microg x kg(-1) x h(-1); and Groups BL and LL, 10.8 microg x kg(-1) x h(-1)) was started after bolus injection (Groups BC and LC, 0 microg/kg; Groups BS and LS, 0.5 microg/kg; and Groups BL and LL, 1.5 microg/kg). Fifteen minutes after the start of the dexmedetomidine infusion, continuous infusion of bupivacaine (Groups BC, BS, and BL) or levobupivacaine (Groups LC, LS, and LL) at 1 mg x kg(-1) x min(-1) was started and continued until tonic/clonic convulsions occurred. Dexmedetomidine achieved significantly different sedation levels both in Groups BC, BS, and BL and in Groups LC, LS, and LL (P < 0.05). Convulsive doses of bupivacaine and levobupivacaine were significantly larger in Groups BL and LL than in Groups BC and LC, respectively (P < 0.01 for both). Concentrations of bupivacaine and levobupivacaine in plasma and in brain at the onset of convulsions were also larger in Groups BL and LL than in Groups BC and LC (P < 0.01 for both). In the second experiment, yohimbine (1 mg/kg) administered 10 min before and 5 min after the start of dexmedetomidine infusion completely reversed the sedative effect of dexmedetomidine (bolus 1.5 microg/kg, followed by 10.8 microg x kg(-1) x h(-1)). Convulsive doses and plasma and brain concentrations of bupivacaine and levobupivacaine at the onset of convulsions in rats receiving yohimbine and dexmedetomidine were significantly smaller than in those receiving only dexmedetomidine (P < 0.05 for all) and were similar to those without dexmedetomidine or yohimbine. We conclude that dexmedetomidine used for sedation decreases the convulsive potency of both bupivacaine and levobupivacaine in rats. Alpha(2)-adrenoceptor agonism may be involved in this anticonvulsant potency.     

The efficacy of dexmedetomidine versus morphine for postoperative analgesia after major inpatient surgery

Thirty-four patients scheduled for elective inpatient surgery were randomized equally to receive either dexmedetomidine (initial loading dose of 1- microg/kg over 10 min followed by 0.4 microg. kg(-1). h(-1) for 4 h) or morphine sulfate (0.08 mg/kg) 30 min before the end of surgery. We determined heart rate (HR), mean arterial blood pressure (MAP), respiratory rate (RR), sedation and analgesia (visual analog scale), and use of additional morphine in the postanesthesia care unit (PACU) and up to 24 h after surgery. Groups were similar for patient demographics, ASA physical status, surgical procedure, baseline hemodynamics, and intraoperative use of drugs and fluids. Dexmedetomidine-treated patients had slower HR in the PACU (by an average of 16 bpm), whereas MAP, RR, and level of sedation were similar between groups. During Phase I recovery, dexmedetomidine-treated patients required significantly less morphine to achieve equivalent analgesia (PACU dexmedetomidine group, 4.5 +/- 6.8 mg; morphine group, 9.2 +/- 5.2 mg). Sixty minutes into recovery only 6 of 17 dexmedetomidine patients required morphine in contrast to 15 of 17 in the morphine group. The administration of dexmedetomidine before the completion of major inpatient surgical procedures significantly reduced, by 66%, the early postoperative need for morphine and was associated with a slower HR in the PACU. IMPLICATIONS: The use of dexmedetomidine for postoperative analgesia resulted in significantly less additional pain medication (morphine) and slower heart rates than a control group receiving only morphine. These outcomes may prove advantageous for patients who might be placed at higher risk by tachycardia or large doses of morphine.     

Remifentanil sedation compared with propofol during regional anaesthesia

BACKGROUND: The short onset and offset of remifentanil may allow for accurate dosing of sedative effect with few side-effects and rapid recovery. In this study remifentanil is compared with propofol for sedation during successful regional anaesthetic blocks. METHODS: After informed consent was given, 125 patients undergoing surgery under spinal or brachial plexus anaesthesia were randomized to receive, either propofol: bolus 500 microg/kg plus initial infusion 50 microgkg/min or remifentanil: bolus 0.5 microg/kg plus initial infusion 0.1 microgkg/min. Study drug infusion rate was titrated throughout the procedure according to level of sedation and side-effects. Pain, discomfort, sedation level and side-effects were recorded at regular intervals until discharge from the post operative care unit (PACU). RESULTS: Two patients in the remifentanil group versus ten in the propofol group were treated for discomfort or pain during surgery (P<0.02). Due to a significantly higher rate of respiratory depression (46% vs. 19% with propofol, P<0.01) the mean remifentanil infusion rate was decreased to 0.078 +/- 0.028 microgkg/min, whereas it was kept stable with propofol. Propofol patients had significantly higher (P<0.05) sedation levels and experienced more frequent amnesia of the procedure. Eleven propofol patients experienced pain at injection site, versus two remifentanil patients (P<0.02). Nausea and vomiting were more frequent in the remifentanil patients during infusion (27% vs. 2% in the propofol group, P<0.001) but similar postoperatively. Time to discharge from PACU was similar in the two groups. CONCLUSION: Propofol results in less respiratory depression and nausea when sedation is needed during a case with a successful regional block. Remifentanil may be considered as an alternative if pain during the procedure is a major concern or if amnesia is contraindicated.     

脑电双频指数引导下右美托咪啶和咪达唑仑用于下肢手术镇静的比较

目的 比较和评估右美托咪啶(dexmedetomidine,DEX)和咪达唑仑用于骨科下肢手术中镇静的效果和安全性.方法 骨科下肢手术患者52例,均接受腰硬联合麻醉,按镇静方法 完全随机分为两组:D组27例,以DEX0.5μg·kg-1·h-1静脉恒速输注(负荷量0.5 μg/kg);M组25例,以咪达唑仑50 μg·...