Echocardiographic evaluation of the effects of dexmedetomidine on cardiac function during total intravenous anaesthesia

Randomized single-blinded study comparing sedation effectiveness and hemodynamic stability of remifentanil vs dexmedetomidine infusion for electrophysiology procedures in patients of National Heart Institute cathlab

BACKGROUND

While studies comparing the effectiveness of remifentanil and dexmedetomidine are prevalent in other nations, using remifentanil alone is uncommon in Malaysia. This research aims to evaluate the effectiveness of sedation with remifentanil or dexmedetomidine infusion in monitored anesthesia care for electrophysiology procedures.

METHODS

This study is a single-center, single-blinded, prospective randomized clinical study. One hundred twenty patients were randomized into two groups (remifentanil vs dexmedetomidine). Demographic characteristics and clinical outcomes, including level of sedation, vital signs, and patient satisfaction were monitored and recorded.

RESULTS

Group R showed a higher mean observer's assessment of alertness/sedation score (3.9 ± 0.7 vs 3.6 ± 0.8; p = 0.008), mean arterial pressure (92.0 ± 12.0 vs 83.0 ± 13.0 mmHg; p < 0.001), heart rate (82.0 ± 20.0 vs 73.0 ± 18.0 beats/min; p = 0.006), systolic blood pressure (139.0 ± 16.0 vs 123.0 ± 17.0 mmHg; p < 0.001) and diastolic blood pressure (75.0 ± 13.0 vs 69.0 ± 14.0 mmHg; p = 0.009) than Group D. Oxygen saturation (99.0 ± 1.0%; p = 0.220) and respiration rate (16.0 ± 3.0 breaths/min; p = 0.361) for both groups were the same. Adverse events, including hypotension, bradycardia, and respiratory depression were observed in both groups. Both groups gave positive responses ranging from fair to good for patient satisfaction.

CONCLUSION

Dexmedetomidine is a better choice of anesthesia as it was associated with a higher level of sedation, more stable hemodynamics, lower incidence of adverse events, and better patient satisfaction.

The effects of dexmedetomidine on intraoperative neurophysiologic monitoring modalities during corrective scoliosis surgery in pediatric patients: A systematic review

BACKGROUND

During scoliosis surgery, motor evoked potentials (MEP), and somatosensory evoked potentials (SSEP) have been reported to be affected by the use of higher doses of anesthetic agents. Dexmedetomidine, a sympatholytic agent, an alpha-2 receptor agonist, has been used as an adjunctive agent to lower anesthetic dose. However, there is conflicting evidence regarding the effects of dexmedetomidine on the intraoperative neurophysiological monitoring of MEP and SSEP during surgery, particularly among pediatric patients.

OBJECTIVES

This systematic review aimed to determine whether, during spinal fusion surgery in pediatric patients with scoliosis, dexmedetomidine alters MEP amplitude or SSEP latency and amplitude and, if so, whether different doses of dexmedetomidine display different effects (PROSPERO registration number CRD42022300562).

METHODS

We searched PubMed, Scopus, and Cochrane Library on January 1, 2022 and included randomized controlled trials, observational cohort and case-control studies and case series investigating dexmedetomidine in the population of interest and comparing against a standardized anesthesia regimen without dexmedetomidine or comparing multiple doses of dexmedetomidine. Animal and in vitro studies and conference abstracts were excluded.

RESULTS

We found substantial heterogeneity in the risk of bias (per Cochrane-preferred tools) of the included articles (n = 5); results are summarized without meta-analysis. Articles with the lowest risk of bias indicated that dexmedetomidine was associated with MEP loss and that higher doses of dexmedetomidine increased risk. In contrast, articles reporting no association between dexmedetomidine and MEP loss suffered from higher risk of bias, including suspected or confirmed problems with confounding, outcome measurement, participant selection, results reporting, and lack of statistical transparency and power.

CONCLUSION

Given the limitations of the studies available in the literature, it would be advisable to conduct rigorous randomized controlled trials with larger sample sizes to assess the effects of dexmedetomidine use of in scoliosis surgery in pediatric patients.

Comparison of esketamine versus dexmedetomidine for attenuation of cardiovascular stress response to double-lumen tracheal tube intubation: a randomized controlled trial

Introduction

The insertion of a double-lumen tracheal tube may cause a transient but more intense sympathetic response. We examined the effects of esketamine vs. dexmedetomidine as an adjuvant to anesthesia induction to blunt double lumen tracheal (DLT) intubation induced cardiovascular stress response.

Methods

In a randomized, double-blind trial, 78 adult patients scheduled for elective thoracotomy under general anesthesia requiring DLT intubation were enrolled. The patients were randomly divided into three groups: each group received one of the following drugs prior to induction of anesthesia: dexmedetomidine 0.8 µg/kg (Group A), esketamine 0.5 mg/kg (Group B), or normal saline (group C). The primary outcome was the incidence of a DLT intubation-related cardiovascular stress response, defined as an increase in mean arterial pressure or heart rate of >30% above the baseline values. The secondary outcomes were changes in hemodynamic and cardiac function.

Results

The incidence of the response to cardiovascular stress was 23.1%, 30.8%, and 65.4% in groups A, B, and C, respectively. There was a significant decrease in intubation response in groups A and B in comparison with group C (P < 0.01); however, there was no significant difference between group A and group B (P > 0.05). Following the drug infusion and the induction of anesthesia, there was a significant decrease in HR and cardiac output in group A compared with group B. In contrast, no significant differences were observed in the left ventricular ejection fraction or in stroke volume between the three groups during induction of anesthesia.

Discussion

Esketamine 0.5 mg/kg and dexmedetomidine 0.8 µg/kg attenuate cardiovascular stress responses related to DLT intubation. As adjuvants to etomidate induction, they do not impair cardiac function (ChiCTR1900028030).

Effect of Dexmedetomidine on Cardiac Output among Parturient with Severe Preeclampsia after Cesarean Section

This study was to investigate the hemodynamic effect of dexmedetomidine among parturient with severe preeclampsia after cesarean section. Parturient with severe preeclampsia were randomly allocated to receive dexmedetomidine (0.2-0.7 μg/kg/h) or equivalent volumes of 0.9% saline as control after cesarean section, respectively. A total of 36 parturient with severe preeclampsia were enrolled, including 18 in the dexmedetomidine (DEX) group and 18 in the saline group. Compared with the saline group, among those in the DEX group, CO was reduced by 1.30 L/min (95% CI: -2.36 to 0.25; $P=0.019$ ). Additionally, HR (-13.79 bpm, 95% CI: -22.02 to -5.58; $P=0.002$ ), SBP (-16.11 mmHg, 95% CI: -30.56 to -1.66; $P=0.030$ ), DBP (-10.48 mmHg, 95% CI: -18.27 to -2.69; $P=0.002$ ), and MAP (-12.36 mmHg, 95% CI: -22.05 to -2.66; $P=0.014$ ) were reduced in the DEX group compared with the saline group. In contrast, there were no changes observed in SV and ICON between groups. In conclusion, dexmedetomidine reduces cardiac output by inhibiting the acceleration of heart rate without sacrificing myocardial contractility and stroke volume.

Neuroprotective effects of intraoperative dexmedetomidine versus saline infusion combined with goal-directed haemodynamic therapy for patients undergoing cranial surgery: A randomised controlled trial

BACKGROUND

By inhibiting neuroinflammation dexmedetomidine may be neuroprotective in patients undergoing cranial surgery, but it reduces cardiac output and cerebral blood flow.

OBJECTIVE

To investigate whether intra-operative dexmedetomidine combined with goal-directed haemodynamic therapy (GDHT) has neuroprotective effects in cranial surgery.

DESIGN

A double-blind, single-institution, randomised controlled trial.

SETTING

A single university hospital, from April 2017 to April 2020.

PATIENTS

A total of 160 adults undergoing elective cranial surgery.

INTERVENTION

Infusion of dexmedetomidine (0.5 μg kg-1 h-1) or saline combined with GDHT to optimise stroke volume during surgery.

MAIN OUTCOME MEASURES

The proportion who developed postoperative neurological complications was compared. Postoperative disability was assessed using the Barthel Index at time points between admission and discharge, and also the 30-day modified Rankin Scale (mRS). Postoperative delirium was assessed. The concentration of a peri-operative serum neuroinflammatory mediator, high-mobility group box 1 protein (HMGB1), was compared.

RESULTS

Fewer patients in the dexmedetomidine group developed new postoperative neurological complications (26.3% vs. 43.8%; P = 0.031), but the number of patients developing severe neurological complications was comparable between the two groups (11.3% vs. 20.0%; P = 0.191). In the dexmedetomidine group the Barthel Index reduction [0 (-10 to 0)] was less than that in the control group [-5 (-15 to 0)]; P = 0.023, and there was a more favourable 30-day mRS (P = 0.013) with more patients without postoperative delirium (84.6% vs. 64.2%; P = 0.012). Furthermore, dexmedetomidine induced a significant reduction in peri-operative serum HMGB1 level from the baseline (222.5 ± 408.3 pg ml-1) to the first postoperative day (152.2 ± 280.0 pg ml-1) P = 0.0033. There was no significant change in the control group. The dexmedetomidine group had a lower cardiac index than did the control group (3.0 ± 0.8 vs. 3.4 ± 1.8 l min-1 m-2; P = 0.0482) without lactate accumulation.

CONCLUSIONS

Dexmedetomidine infusion combined with GDHT may mitigate neuroinflammation without undesirable haemodynamic effects during cranial surgery and therefore be neuroprotective.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT02878707.

Review of the Physiology and Anesthetic Considerations for Pleuroscopy/Medical Thoracoscopy

Pleuroscopy or medical thoracoscopy is the second most common utilized procedure after bronchoscopy in the promising field of interventional pulmonology. Its main application is for the diagnosis and management of benign or malignant pleural effusions. Entry into the hemithorax is associated with pain and patient discomfort, whereas concurrently, notable pathophysiologic alterations occur. Therefore, frequently procedural sedation and analgesia is needed, not only to alleviate the patient's emotional stress and discomfort by mitigating the anxiety and minimizing the pain but also for yielding better procedural conditions for the operator. The scope of this review is to present the physiologic derangements occurring in pleuroscopy and compare the various anesthetic techniques and sedative agents that are currently being used in this context.

Monitored Anesthesia Care with Dexmedetomidine Supplemented by Midazolam/Fentanyl versus Midazolam/Fentanyl Alone in Patients Undergoing Pleuroscopy: Effect on Oxygenation and Respiratory Function

Although pleuroscopy is considered a safe and well tolerated procedure with a low complication rate, it requires the administration of procedural sedation and analgesia. The purpose of this study was to assess the effects of dexmedetomidine administration on oxygenation and respiratory function in patients undergoing diagnostic or therapeutic pleuroscopy. Through a prospective, single center, cohort study, we studied 55 patients receiving either a dexmedetomidine intravenous infusion supplemented by midazolam/fentanyl (Group DEX + MZ/F) or a conventional sedation protocol with midazolam/fentanyl (Group MZ/F). Our primary outcome was the changes in lung gas exchange (PaO₂/FiO₂ ratio) obtained at baseline and at predetermined end points, while changes in respiratory mechanics (FEV1, FVC and the ratio FEV1/FVC) and PaCO₂ levels, drug consumption, time to recover from sedation and adverse events were our secondary endpoints (NCT03597828). We found a lower postoperative decrease in FEV1 volumes in Group DEX + MZ/F compared to Group MZ/F (p = 0.039), while FVC, FEV1/FVC and gas exchange values did not differ between groups. We also found a significant reduction in midazolam (p < 0.001) and fentanyl consumption (p < 0.001), along with a more rapid recovery of alertness postprocedure in Group DEX + MZ/F compared to Group MZ/F (p = 0.003), while pain scores during the postoperative period, favored the Group DEX + MZ/F (p = 0.020). In conclusion, the use of intravenous dexmedetomidine during pleuroscopy is associated with a smaller decrease in FEV1, reduction of the consumption of supplementary sedatives and analgesics and quicker awakening of patients postoperatively, when compared to midazolam/fentanyl. Therefore, dexmedetomidine administration may provide clinically significant benefits in terms of lung mechanics and faster recovery of patients undergoing pleuroscopy.

Effect of Different Loading Doses of Dexmedetomidine on Controlled Hypotension and the Incidence of Bradycardia During Rhinoplasty: A Clinical Trial

Controlled hypotension, with a mean arterial pressure (MAP) of 60 mmHg - 70 mmHg, provides a bloodless and visible surgical field during rhinoplasty. It has been shown that dexmedetomidine, an α2-adrenoreceptor agonist, is a suitable choice in this regard. One of the disadvantages of this drug is the possibility of severe bradycardia during infusion. Therefore, we compared lower intravenous (IV) loading doses to determine whether the hypotensive effect of the drug was preserved and the bradycardia incidence decreased. In this randomized, double-blinded clinical trial, 81 patients aged 18 to 50 years with the American Society of Anesthesiologists physical status (ASA-PS) class I and II, scheduled for rhinoplasty randomly received 1.0, 0.9, and 0.8 µg/kg (named as groups 1.0, 0.9, and 0.8, respectively) of IV dexmedetomidine before the induction of anesthesia followed by infusion (0.3 - 0.7 µg/kg/h) during operation. The patients' heart rate (HR), MAP, the requirements for nitroglycerin (NTG) and extra fentanyl, as well as the incidence of bradycardia, were recorded. Bleeding and visibility of the surgical field were scored by the surgeon using a 6-point visual scale. MAPs, HRs, and consumption of NTG and extra fentanyl were similar in the studied groups. The surgical field was more visible and bloodless in group 1.0 compared to group 0.8 (P < 0.001); the differences were not significant between groups 1.0 and 0.9 (P = 0.605). The incidence (P = 0.027) and the severity of bradycardia (P = 0.017) were higher in the groups with higher loading doses. We concluded that dexmedetomidine is an acceptable agent to provide controlled hypotension. A loading dose of 0.9 µg/kg, but not 0.8 µg/kg, provides similar surgical field conditions as the dose of 1 µg/kg. Furthermore, despite the decrease in the incidence of bradycardia, the hypotensive effect of the drug is preserved.

Effects of Propofol, Dexmedetomidine, or Ketofol on Respiratory and Hemodynamic Profiles in Cardiac Patients Undergoing Transesophageal Echocardiography: A Prospective Randomized Study

OBJECTIVES

The authors aimed to evaluate sedation characteristics, as well as cardiorespiratory effects, of propofol, dexmedetomidine, and ketofol used for conscious sedation during transesophageal echocardiography (TEE).

DESIGN

Prospective double-blind randomized study.

SETTINGS

Tanta University hospitals.

PARTICIPANTS

Seventy-five participants with left-to-right shunt requiring diagnostic TEE interventions. Patients were randomized into three groups-P, Dex, and K-to receive propofol, dexmedetomidine, or ketofol, respectively.

MEASUREMENTS AND MAIN RESULTS

Time to reach targeted sedation level, duration of the procedure, recovery time, hemodynamic parameters, incidence of oxygen desaturation <90%, as well as the cardiologist's satisfaction were recorded. The time onset and offset of sedation, duration of TEE procedure, and the need for rescue propofol were significantly less in the P and K groups compared with group Dex (p value 0.000*, 0.003*, 0.000*, and 0.000* and effect size 0.39, 0.15, 0.21, and 0.34, respectively). Mean arterial pressure, heart rate, and cardiac output significantly decreased in groups P and Dex compared with either baseline or group K. Hypoxic events were more manifest in group P; whereas group K had better cardiologist's satisfaction than the other two groups.

CONCLUSIONS

In the TEE settings, the three agents were capable of attaining the targeted sedation levels , with propofol and ketofol having a faster onset and recovery times compared with dexmedetomidine. Even though dexmedetomidine and ketofol provided a more stable respiratory profile than propofol, ketofol was favorable in providing fewer hemodynamic alterations with better satisfaction scores than both propofol and dexmedetomidine.

Safety of dexmedetomidine in the cardiac intensive care unit

AIMS

Dexmedetomidine is one of the sedative agents recommended by the Society of Critical Care Medicine as a preferred option over benzodiazepines in critically ill, mechanically ventilated patients. Little data exists describing sedation in the cardiac intensive care unit (CICU). The purpose of this study was to determine the prevalence of adverse events in CICU patients treated with dexmedetomidine.

METHODS AND RESULTS

This was a retrospective cohort analysis of patients >18 years old admitted to the University of Michigan CICU from June 2014 to October 2019 who received dexmedetomidine therapy. The primary outcome was the composite of adverse events including bradycardia, hypotension, increasing vasopressor/inotrope requirements, and asystole. Secondary outcomes included individual components of the primary outcome. Patients that experienced adverse events were compared to those that did not experience adverse events to identify risk factors for adverse events. A total of 197 patients were included. There were 116 adverse events in 106 patients. Hypotension was the most common adverse event, making up 60.3% of adverse events reported. Increased vasopressor requirement and bradycardia both occurred in 22 patients (18.9%). Asystole occurred in two patients. B-type natriuretic peptide (BNP) levels were significantly higher in those experiencing an adverse event (848 pg/mL vs. 431 pg/mL; P = 0.03).

CONCLUSIONS

Patients admitted to the CICU experienced a high rate of adverse events with dexmedetomidine use. Those experiencing adverse events were more likely to have a higher BNP. Future studies should explore the safety of alternative sedative agents to ascertain safe pharmacological options for patients admitted to the CICU.

Comparison of sedation between dexmedetomidine and propofol during transesophageal echocardiography: A randomized controlled trial

Background:

This study aimed to compare sedation characteristics of dexmedetomidine (Dex) and propofol during transesophageal echocardiography (TEE) in cardiac patients.

Methods:

This clinical trial was conducted on 65 cardiac patients, who underwent TEE in a referral heart hospital. The patients were randomly divided into two groups: Dex (n = 34) and propofol (n = 31). The depth of sedation in the patients was assessed at 5-min intervals until the end of the TEE examination. The patient, physicians’ satisfaction was recorded. Furthermore, blood pressure, heart and respiratory rates, peripheral oxygen saturation, and the bispectral index (BIS) of the patients were measured. The occurrence of apnea, hypotension or bradycardia was documented.

Results:

Demographic variables were similar in both groups. Time from the beginning of sedation to the start of TEE was significantly longer in the Dex group (P = 0.01). Duration of the TEE examination was not different between the two groups. Interestingly, the recovery time was shorter in the Dex group than in the propofol group. There were no significant differences regarding patient and physician satisfaction with sedation quality. Hemodynamic profile was mainly similar in both groups. There was a significantly lower BIS level in the Dex group. There was no significant difference in the incidence of apnea or hypotension between the groups.

Conclusions:

Time from the beginning of sedation with Dex was longer than that with propofol. However, Dex was able to provide satisfactory sedation levels, hemodynamic stability, short recovery time, and acceptable patient and practitioner satisfaction during TEE in our cardiac patients.

Positive Pressure Ventilation in Cardiogenic Shock: Review of the Evidence and Practical Advice for Patients With Mechanical Circulatory Support

Cardiogenic shock (CS) is often complicated by respiratory failure, and more than 80% of patients with CS require respiratory support. Elevated filling pressures from left-ventricular (LV) dysfunction lead to alveolar pulmonary edema, which impairs both oxygenation and ventilation. The implementation of positive pressure ventilation (PPV) improves gas exchange and can improve cardiovascular hemodynamics by reducing preload and afterload of the LV, reducing mitral regurgitation and decreasing myocardial oxygen demand, all of which can help augment cardiac output and improve tissue perfusion. In right ventricular (RV) failure, however, PPV can potentially decrease preload and increase afterload, which can potentially lead to hemodynamic deterioration. Thus, a working understanding of cardiopulmonary interactions during PPV in LV and RV dominant CS states is required to safely treat this complex and high-acuity group of patients with respiratory failure. Herein, we provide a review of the published literature with a comprehensive discussion of the available evidence on the use of PPV in CS. Furthermore, we provide a practical framework for the selection of ventilator settings in patients with and without mechanical circulatory support, induction, and sedation methods, and an algorithm for liberation from PPV in patients with CS.

Effect of a low-dose dexmedetomidine infusion on intraoperative hemodynamics, anesthetic requirements and recovery profile in patients undergoing lumbar spine surgery

Background and Aims

Dexmedetomidine has been used as an anesthetic adjuvant; however, hypotension is a concern especially in prone patients. The aim of the study was to evaluate the effect of a low-dose dexmedetomidine infusion on intraoperative hemodynamics, blood loss, anesthetic requirements, and recovery profile in patients undergoing lumbar spine surgery in the prone position.

Material and Methods

The study was conducted in a randomized double-blinded manner in 60 patients scheduled for one- or two-level lumbar laminectomy. After administration of general anesthesia, patients were placed in prone position and allocated to either of two groups of 30 patients each. Patients in Group A received dexmedetomidine infusion at the rate of 0.3 μg kg^-1 hr^-1, whereas, group B patients received a saline infusion. The depth of anesthesia was guided by Bispectral index (BIS) monitoring, maintaining BIS between 40 and 60.

Results

The demographic profile and duration of surgery in both groups were similar. Mean heart rate was statistically similar in both the groups. Mean blood pressure was lower in group A, though the difference was significant only for the initial 30 min. The mean end-tidal sevoflurane requirement in group A was significantly less than that in group B (P = 0.003). Patients in group A had better recovery profile with mean emergence, extubation, and recovery times of 8.08 ± 3.48 min, 9.37 ± 3.64 min, and 11.65 ± 4.03 min, respectively, as compared with 11.27 ± 3.05 min, 12.24 ± 2.39 min, and 14.90 ± 2.63 min, respectively, in group B (P < 0.001). Mean intraoperative blood loss in group A of 263.47 ± 58.66 mL was significantly lower than 347.67 ± 72.90 ml in group B (P = 0.0001).

Conclusion

Group A patients had stable hemodynamic parameters, reduced intraoperative blood loss, less anesthetic requirement, and could be extubated earlier as compared with group B patients.

Clinical Pharmacokinetics and Pharmacodynamics of Dexmedetomidine

Dexmedetomidine is an α₂-adrenoceptor agonist with sedative, anxiolytic, sympatholytic, and analgesic-sparing effects, and minimal depression of respiratory function. It is potent and highly selective for α₂-receptors with an α₂:α₁ ratio of 1620:1. Hemodynamic effects, which include transient hypertension, bradycardia, and hypotension, result from the drug’s peripheral vasoconstrictive and sympatholytic properties. Dexmedetomidine exerts its hypnotic action through activation of central pre- and postsynaptic α₂-receptors in the locus coeruleus, thereby inducting a state of unconsciousness similar to natural sleep, with the unique aspect that patients remain easily rousable and cooperative. Dexmedetomidine is rapidly distributed and is mainly hepatically metabolized into inactive metabolites by glucuronidation and hydroxylation. A high inter-individual variability in dexmedetomidine pharmacokinetics has been described, especially in the intensive care unit population. In recent years, multiple pharmacokinetic non-compartmental analyses as well as population pharmacokinetic studies have been performed. Body size, hepatic impairment, and presumably plasma albumin and cardiac output have a significant impact on dexmedetomidine pharmacokinetics. Results regarding other covariates remain inconclusive and warrant further research. Although initially approved for intravenous use for up to 24 h in the adult intensive care unit population only, applications of dexmedetomidine in clinical practice have been widened over the past few years. Procedural sedation with dexmedetomidine was additionally approved by the US Food and Drug Administration in 2003 and dexmedetomidine has appeared useful in multiple off-label applications such as pediatric sedation, intranasal or buccal administration, and use as an adjuvant to local analgesia techniques.

Editor’s Choice- Sedation in the coronary intensive care unit: An adapted algorithm for critically ill cardiovascular patient

In the current era, cardiovascular intensive care units care for more complex patients who are far sicker than historical post-myocardial infarction patients, and sedation has become a common intervention in these units. Current sedation best practices derive mainly from non-cardiac units which limits their generalization to the critically ill cardiac patient. Thus, a great variability in sedation protocols, especially the selection of sedative agents, is commonly seen in daily practice across cardiac units. We present an updated review on sedation in cardiovascular critical care medicine with emphasis on the hemodynamic impact. The goal of this review is to generate a general sedation algorithm specific for the cardiac patient.

Controlled Hypotension During Rhinoplasty: A Comparison of Dexmedetomidine with Magnesium Sulfate

Objective

The current study aimed at comparing the efficacy of dexmedetomidine and magnesium sulfate to control blood pressure (BP) during rhinoplasty and the resultant effects on the quality of surgical field in terms of bleeding and visibility.

Methods

The current randomized, prospective, double-blind study was conducted on 60 patients aged 18 to 50 years classified as ASA (American Society of Anesthesiologists) physical status I who were candidates for rhinoplasty. Patients were randomly divided into 2 groups: (1) group Dex, received 1 µg/kg dexmedetomidine in 10 minutes before induction of anesthesia, followed by 0.4 - 0.6 µg/kg/hour during the maintenance of anesthesia, and (2) group Mg, received 40 mg/kg in 10 minutes before anesthesia induction followed by 10 - 15 mg/kg/hour during anesthesia maintenance. In both groups, the goal was to achieve a mean arterial pressure (MAP) of 60 - 70 mmHg. Hemodynamic variables, anesthetic, opioid, muscle relaxant requirements, and surgical field condition were recorded. Sedation score, time to reach modified Aldrete score ≥ 9, and adverse effects including nausea and vomiting (N&V) and shivering were recorded.

Results

Controlled hypotension was achieved in both groups. There was no significant difference in MAP between the groups, but heart rate (HR) was significantly lower in the Dex group (P < 0.001), compared with that of the Mg group. Bleeding score was lower (P < 0.001) and surgeon's satisfaction score was higher (P < 0.001) in the Dex group. More patients required fentanyl (P < 0.001) or nitroglycerin (P < 0.001) and the mean fentanyl (P = 0.005) or nitroglycerin (P < 0.001) required doses were higher in the Mg group. Patients in the Dex group required more frequent administration of cisatracurium (P = 0.004). Five patients in the Dex group versus no patients in the Mg group received atropine (P = 0.023). Ramsay sedation score and time to reach modified Aldrete score ≥ 9 were significantly higher in the Dex group (P < 0.001 and P < 0.001, respectively). The incidence rate of N&V and shivering were similar in both groups.

Conclusion

Dexmedetomidine was more effective than magnesium to achieve controlled hypotension, and provide a favorable surgical field condition. However, dexmedetomidine also heightened the risk of induced bradycardia and prolonged sedation. These are 2 important points to consider when applying this drug as a hypotensive agent during operation.

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.

Risk Factors for Dexmedetomidine-Associated Hemodynamic Instability in Noncardiac Intensive Care Unit Patients

BACKGROUND

The reported incidence of hypotension and bradycardia in patients receiving dexmedetomidine for sedation commonly exceeds 50%. In this study, we describe the incidence of, patient- and treatment-specific risk factors for, and clinical significance of dexmedetomidine-associated hemodynamic instability.

METHODS

This retrospective cohort study was conducted in critically ill adults receiving dexmedetomidine for sedation at Mayo Clinic Hospital in Rochester, MN, during a 1-year period. The primary end point was hemodynamic instability: a composite of hypotension and/or bradycardia, defined as systolic blood pressure <80 mm Hg, diastolic blood pressure <50 mm Hg, or heart rate <50 beats per minute during dexmedetomidine therapy. Cox proportional hazards models were constructed to determine hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk factors of hemodynamic instability.

RESULTS

Hemodynamic instability occurred in 197 of the analyzed 300 patients receiving dexmedetomidine, resulting in a cumulative incidence of 71% at 24 hours via Kaplan-Meier estimation. In addition to dexmedetomidine, univariate analysis identified age, vasopressor use, low baseline arterial blood pressure, and concomitant sedatives as associated with increased risk of hemodynamic instability. Multivariable analysis demonstrated associations between age (HR, 1.23 per 10 years, 95% CI, 1.10-1.38) and low baseline blood pressure (HR, 2.42 at dexmedetomidine initiation, 95% CI, 1.68-3.49) and risk of hemodynamic instability. Variables such as concomitantly administered cardiac medications or sedative therapies and dexmedetomidine infusion rates >0.7 μg/kg/h were not found to be predictors of hemodynamic instability among the analyzed sample.

CONCLUSIONS

Hemodynamic instability commonly occurs in critically ill adults receiving dexmedetomidine, with more than two thirds of this cohort experiencing hypotension and/or bradycardia within 24 hours of initiation. Increasing age and low baseline arterial blood pressure were associated with the development of hemodynamic instability. These findings suggest that clinicians should be aware of the potential risk of hemodynamic instability when using dexmedetomidine in patients with advanced age or low baseline arterial blood pressure.

The Effects of Dexmedetomidine on Myocardial Function Assessed by Tissue Doppler Echocardiography During General Anesthesia in Patients With Diastolic Dysfunction: A CONSORT-Prospective, Randomized, Controlled Trial

Dexmedetomidine is a commonly used sedative and adjuvant agent to general anesthesia. The present was designed to evaluate the effects of dexmedetomidine on myocardial function by using tissue Doppler echocardiography during general anesthesia in patients with diastolic dysfunction.Forty patients undergoing orthostatic surgery with ejection fraction preserved diastolic dysfunction grade 2 or 3 were randomly allocated to the Control and Dex group (n = 20, each). In the Dex group, dexmedetomidine was given as an initial loading dose of 1.0 μg/kg over 10 minutes followed by a maintenance dose of 0.5 μg/kg/h. The ratio of peak early diastolic transmitral or transtricuspid inflow velocity to early diastolic mitral or tricuspid annular velocity (LV or RV E/e') and left or right ventricular myocardial performance index (LV or RV MPI) were measured at before and after the administration dexmedetomidine or saline.The Dex group showed significant decrease of heart rate (P = 0.038), and increase of mean blood pressure (P < 0.001), LV E/e' (P = 0.025), and LV MPI (P < 0.001) compared to those of the Control group on a linear mixed model analysis. Also, the Dex group showed significant increase of RV E/e' (P < 0.001) and RV MPI (P = 0.028) compared to those of the Control group.Intraoperative dexmedetomidine administration during general anesthesia was appeared to deteriorate biventricular function in patients with diastolic dysfunction. We suggest careful consideration and a need for reducing dosage when administrating dexmedetomidine in patients with diastolic dysfunction.

Effect of dexmedetomidine on hippocampal neuron development and BDNF-TrkB signal expression in neonatal rats

The study aimed to explore the effect of dexmedetomidine (DEX) on hippocampal neuron development process and on molecular expression of brain-derived neurotrophic factor (BDNF)-tyrosine receptor kinase B (TrkB) signaling pathway in neonatal rats. The hippocampal neuron cells were isolated from newborn neonatal rats and cultured in vitro. One control group and three treated groups with 1, 10, and 100 μmol/L DEX were used for the study. Cell activity and apoptosis were detected by the MTT and terminal deoxynucleotidyl transferase-mediated biotinylated uridine triphosphate (UTP) nick end labeling assays. The synaptophysin (SYN) and postsynaptic density 95 (PSD95) were detected by quantitative polymerase chain reaction. There was no difference in the viability of neuron cells among the different dose groups of DEX and the control group during days 2-10 (P>0.05). Compared to the control group, there was no significant difference (P>0.05) in the expressions of SYN and PSD95 in the groups treated with 1 and 10 μmol/L DEX, whereas significant difference in the expression was observed in the group treated with 100 μmol/L DEX (P<0.01). Compared with the control group, the expression of BDNF was significantly upregulated (P<0.05) in the group treated with 100 μmol/L DEX. There were no significant differences in TrkB expression among the four groups. The expression of p-N-methyl-D-aspartate receptor increased with an increase in the concentration of DEX; however, only the high dose revealed a significant upregulation compared with the control group. The neuroprotective effect of DEX may be achieved by upregulating the expression of BDNF and phosphorylation level of N-methyl-D-aspartate receptor.