Patient predictors of dexmedetomidine effectiveness for sedation in intensive care units

Patient-Specific Factors Associated with Dexmedetomidine Dose Requirements in Critically Ill Children

The objective of this study was to evaluate patient-specific factors associated with dexmedetomidine dose requirements during continuous infusion. A retrospective cross-sectional analysis of electronic health record-derived data spanning 10 years for patients admitted with a primary respiratory diagnosis at a quaternary children's hospital and who received a dexmedetomidine continuous infusion (n = 346 patients) was conducted. Penalized regression was used to select demographic, clinical, and medication characteristics associated with a median daily dexmedetomidine dose. Identified characteristics were included in multivariable linear regression models and sensitivity analyses. Critically ill children had a median hourly dexmedetomidine dose of 0.5 mcg/kg/h (range: 0.1–1.8), median daily dose of 6.7 mcg/kg/d (range: 0.9–38.4), and median infusion duration of 1.6 days (range: 0.25–5.0). Of 26 variables tested, 15 were selected in the final model with days of dexmedetomidine infusion (β: 1.9; 95% confidence interval [CI]: 1.6, 2.3), median daily morphine milligram equivalents dosing (mg/kg/d) (β: 0.3; 95% CI: 0.1, 0.5), median daily ketamine dosing (mg/kg/d) (β: 0.2; 95% CI: 0.1, 0.3), male sex (β: −1.1; 95% CI: −2.0, −0.2), and non-Black reported race (β: −1.2; 95% CI: −2.3, −0.08) significantly associated with median daily dexmedetomidine dose. Approximately 56% of dose variability was explained by the model. Readily obtainable information such as demographics, concomitant medications, and duration of infusion accounts for over half the variability in dexmedetomidine dosing. Identified factors, as well as additional environmental and genetic factors, warrant investigation in future studies to inform precision dosing strategies.

CYP2A6 and GABRA2 Gene Polymorphisms are Associated With Dexmedetomidine Drug Response

Background: Dexmedetomidine is a commonly used clinical sedative; however, the drug response varies among individuals. Thus, the purpose of this study was to explore the association between dexmedetomidine response and gene polymorphisms related to drug-metabolizing enzymes and drug response (CYP2A6, UGT2B10, UGT1A4, ADRA2A, ADRA2B, ADRA2C, GABRA1, GABRB2, and GLRA1).

Methods: This study was a prospective cohort study. A total of 194 female patients aged 18–60 years, American Society of Anesthesiologists (ASA) score I-II, who underwent laparoscopy at the Third Xiangya Hospital of Central South University, were included. The sedative effect was assessed every 2 min using the Ramsay score, and the patient’s heart rate decrease within 20 min was recorded. Peripheral blood was collected from each participant to identify genetic variants in the candidate genes of metabolic and drug effects using the Sequenom MassARRAY^® platform. Furthermore, additional peripheral blood samples were collected from the first 99 participants at multiple time points after dexmedetomidine infusion to perform dexmedetomidine pharmacokinetic analysis by Phoenix^® WinNonlin 7.0 software.

Results: Carriers of the minor allele (C) of CYP2A6 rs28399433 had lower metabolic enzyme efficiency and higher plasma concentrations of dexmedetomidine. In addition, the participants were divided into dexmedetomidine sensitive or dexmedetomidine tolerant groups based on whether they had a Ramsay score of at least four within 20 min, and CYP2A6 rs28399433 was identified to have a significant influence on the dexmedetomidine sedation sensitivity by logistic regression with Plink software [p = 0.003, OR (95% CI): 0.27 (0.11–0.65)]. C allele carriers were more sensitive to the sedative effects of dexmedetomidine than A allele carriers. GABRA2 rs279847 polymorphism was significantly associated with the degree of the heart rate decrease. In particular, individuals with the GG genotype had a 4-fold higher risk of heart rate abnormality than carriers of the T allele (OR = 4.32, 95% CI: 1.96–9.50, p = 0.00027).

Conclusion:CYP2A6 rs28399433 polymorphism affects the metabolic rate of dexmedetomidine and is associated with susceptibility to the sedative effects of dexmedetomidine; GABRA2 rs279847 polymorphism is significantly associated with the degree of the heart rate decrease.

Standard- versus High-Dose Dexmedetomidine for Sedation in the Intensive Care Unit

Background: Dexmedetomidine is a commonly used sedative in the intensive care unit (ICU), however the use of higher, off label dosing has yet to be elucidated. A dose limitation protocol was implemented at our institution allowing for comparison of dexmedetomidine doses. Objective: The purpose of this study is to evaluate time spent within goal Richmond Agitation Sedation Scale (RASS) range with standard-dosing of dexmedetomidine ≤1 mcg/kg/hour (SD group) compared to high-dose >1 mcg/kg/hour (HD group). Secondary outcomes included days requiring mechanical ventilation, concomitant sedation, and incidence of hypotension or bradycardia. Methods: This retrospective chart review of adult ICU patients at a single academic medical center included patients who required at least 24 hours of mechanical ventilation and received dexmedetomidine monotherapy for at least 4 hours. Patients were excluded for intubations at an outside hospital, continuous neuromuscular blocking infusions, or Glasgow Coma Score ≤4. Results: A total of 144 patients met inclusion criteria (n = 121 SD group and n = 23 HD group). The SD group spent a greater time within goal RASS range compared to the HD group (84.5% [IQR 47-100] vs 45.5% [IQR 30.1-85.4], P = .013). The SD group also had shorter durations of both dexmedetomidine infusion and mechanical ventilation, and required less concomitant sedation. There was no difference in hypotension or bradycardia. Conclusion: This study further adds to the literature that administration of high-dose dexmedetomidine does not appear to confer additional benefit over standard doses for ICU patients requiring mechanical ventilation. Application of this data may support lower institutional maximum doses.

Protein Binding and Population Pharmacokinetics of Dexmedetomidine after Prolonged Infusions in Adult Critically Ill Patients

PURPOSE

Dexmedetomidine (DEX) is a highly selective α₂-adrenoceptor agonist with high protein binding of 94%. Critical illness may affect protein binding and the pharmacokinetic (PK) parameters of many drugs, including DEX. In critically ill patients receiving prolonged infusions of DEX, there is little information documenting the relationship between key pathophysiologic factors and DEX protein binding or PK parameters. The purpose of this study was to characterize the protein binding and PK profile of prolonged DEX infusion in critically ill patients.

METHODS

Critically ill, adult intensive care unit patients at a university hospital in Hong Kong were studied. The association between the pathophysiologic changes of critical illness and protein binding was evaluated using a generalized estimating equation. A population pharmacokinetic model to establish the PK profile of DEX was developed, and key pathophysiologic covariate effects of severity of illness, organ dysfunction measures, and altered protein binding on DEX PK parameters in this critically ill population were evaluated.

FINDINGS

A total of 22 critically ill patients and 1 healthy control were included. Mean protein binding of DEX in the critically ill patients was 90.4% (95% CI, 89.1-91.7), which was 4% lower than that in the healthy control. The PK data were adequately described by a 2-compartment model. The estimated population mean (relative standard error [RSE]) values of systemic clearance (CL), volume of distribution of the central compartment (V2), intercompartmental clearance (Q), and V_d in the peripheral compartment (V3) were 38.6 (11.7) L/h, 32.1 (46.1) L, 114.5 (58.3) L/h and 95.1 (30.6) L, respectively. The corresponding estimated interindividual variability expressed as CV% (RSE) was 52.4 (23.8) for CL, 172.9 (19.3) for V2, 123.7 (33.7) for Q, and 106 (39.9) for V3. No significant explanatory pathophysiologic covariates were identified.

IMPLICATIONS

Although a marginally significant reduction of protein binding in critically ill patients was demonstrated, the magnitude of the difference was unlikely to be of clinical significance. Higher alanine aminotransferase concentration was associated with decreased protein binding. No significant pathophysiologic covariates were associated with the observed PK parameters. The high interindividual variability of PK parameters supports the current practice of dose titration to ensure the desired clinical effects of DEX infusion in the intensive care unit setting.

The effect of alpha-2A adrenergic receptor (ADRA2A) genetic polymorphisms on the depth of sedation of dexmedetomidine: a genetic observational pilot study

Background

The genetic polymorphisms of the alpha-2A adrenergic receptor (ADRA2A), which plays a significant role in sedation, anxiety relief, and antinociception, particularly in dexmedetomidine, may differ in the degree of sedation. This study aimed to investigate the effect of the genetic polymorphisms of ADRA2A (rs11195418, rs1800544, rs2484516, rs1800545, rs553668, rs3750625) on the sedative effects of dexmedetomidine.

Methods

A total of 131 patients aged 50 years or more from May 2018 to August 2019 were included in this study. The ADRA2A gene variants were evaluated using the TaqMan Assay. Dexmedetomidine diluted in normal saline to a concentration of 4 μg.mL^-1 was infused at a dose of 2 μg.kg^-1 to achieve procedural sedation (modified Ramsay sedation scale 4 [mRSS 4]).

Results

A total of 131 patients were evaluated. The genetic polymorphisms (rs11195418) of the ADRA2A receptor gene demonstrated no variation in our participants. The ADRA2A receptor gene polymorphisms (rs1800544, rs2484516, rs1800545, rs553668, and rs3750625) exhibited no differences in total dexmedetomidine doses (p > 0.217), bispectral index at mRSS 4 (p > 0.620), and time to obtain mRSS 4 (p > 0.349).

Conclusion

This study suggested that the genetic polymorphisms of ADRA2A did not affect the sedative efficacy of dexmedetomidine.

Dexmedetomidine as add-on sedation to reduce continuous infusion sedative use in mechanically ventilated patients

PURPOSE

To characterize the impact of add-on dexmedetomidine therapy on baseline continuous infusion sedative use.

METHODS

A retrospective, single-center, chart review-based study was conducted to assess outcomes of and potential predictors of response to add-on dexmedetomidine therapy in mechanically ventilated intensive care unit (ICU) patients who were already receiving continuous infusions of sedatives. Patients were defined as complete, partial, or nonresponders to add-on dexmedetomidine therapy if initial sedative infusion rates were reduced by 100%, by 50% to 99%, and by less than 50%, respectively, at 6 and 24 hours after initiation of dexmedetomidine.

RESULTS

Among the 100 patients included in the study sample, there were 54 complete responders, 21 partial responders, and 25 nonresponders to dexmedetomidine add-on therapy at 6 hours after dexmedetomidine initiation; at 24 hours, there were 65 complete and 12 partial responders and 23 nonresponders. Of the variables tested (ie, baseline characteristics, opioid and antipsychotic use, hemodynamic parameters), none differentiated between complete or partial responders and nonresponders. Ventilator time, ICU length of stay (LOS), and hospital LOS after add-on dexmedetomidine therapy initiation were shorter among both partial responders and complete responders vs nonresponders (median, 1.1 days vs 4.1 days [P = 0.01], 7.0 days vs 14.1 days [P = 0.20], and 11.0 vs 17.0 days [P = 0.58], respectively), with only ventilator time being significantly different.

CONCLUSION

Add-on dexmedetomidine therapy can obviate or reduce the need for alternate sedation in as many as 75% of mechanically ventilated ICU patients. However, the addition of dexmedetomidine does not allow the reduction of alternate sedation in a substantial minority of patients, and failure to respond to dexmedetomidine can be identified as early at 6 hours after add-on therapy initiation. In the absence of clear predictors of response to dexmedetomidine, these data suggest empiric trials of dexmedetomidine can be considered but should be time-limited.

Effects of Dexmedetomidine on the Pharmacokinetics of Parecoxib and Its Metabolite Valdecoxib in Beagles by UPLC-MS/MS

A sensitive and reliable ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous determination of parecoxib and its metabolite valdecoxib in beagles. The effects of dexmedetomidine on the pharmacokinetics of parecoxib and valdecoxib in beagles were studied. The plasma was precipitated by acetonitrile, and the two analytes were separated on an Acquity UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm); the mobile phase was acetonitrile and 0.1% formic acid with gradient mode, and the flow rate was 0.4 mL/min. In the negative ion mode, the two analytes and internal standard (IS) were monitored by multiple reaction monitoring (MRM), and the mass transition pairs were as follows: m/z 369.1 → 119.1 for parecoxib, m/z 313.0 → 118.0 for valdecoxib, and m/z 380.0 → 316.0 for celecoxib (IS). Six beagles were designed as a double cycle self-control experiment. In the first cycle, after intramuscular injection of parecoxib 1.33 mg/kg, 1.0 mL blood samples were collected at different times (group A). In the second cycle, the same six beagles were intravenously injected with 2 μg/kg dexmedetomidine for 7 days after one week of washing period. On day 7, after intravenous injection of 2 μg/kg dexmedetomidine for 0.5 hours, 6 beagle dogs were intramuscularly injected with 1.33 mg/kg parecoxib, and blood samples were collected at different time points (group A). The concentration of parecoxib and valdecoxib was detected by UPLC-MS/MS, and the main pharmacokinetic parameters were calculated by DAS 2.0 software. Under the experimental conditions, the method has a good linear relationship for both analytes. The interday and intraday precision was less than 8.07%; the accuracy values were from -1.20% to 2.76%. C_max of parecoxib in group A and group B was 2148.59 ± 406.13 ng/mL and 2100.49 ± 356.94 ng/mL, t_1/2 was 0.85 ± 0.36 h and 0.85 ± 0.36 h, and AUC_(0‐t) was 2429.96 ± 323.22 ng·h/mL and 2506.38 ± 544.83 ng·h/mL, respectively. C_max of valdecoxib in group A and group B was 2059.15 ± 281.86 ng/mL and 2837.39 ± 276.78 ng/mL, t_1/2 was 2.44 ± 1.55 h and 2.91 ± 1.27 h, and AUC_(0‐t) was 4971.61 ± 696.56 ng·h/mL and 6770.65 ± 453.25 ng·h/mL, respectively. There was no significant change in the pharmacokinetics of parecoxib in groups A and B. C_max and AUC_{(0 − ∞)} of valdecoxib in group A were 37.79% and 36.19% higher than those in group B, respectively, and t_1/2 was increased from 2.44 h to 2.91 h. V_z/F and CL_z/F were correspondingly reduced, respectively. The developed UPLC-MS/MS method for simultaneous determination of parecoxib and valdecoxib in beagle plasma was specific, accurate, rapid, and suitable for the pharmacokinetics and drug-drug interactions of parecoxib and valdecoxib. Dexmedetomidine can inhibit the metabolism of valdecoxib in beagles and increase the exposure of valdecoxib, but it does not affect the pharmacokinetics of parecoxib.

Recovery time after oral and maxillofacial ambulatory surgery with dexmedetomidine: an observational study

OBJECTIVES

To evaluate the relationship between pharmacokinetic descriptors of dexmedetomidine (predicted area under the curve during the procedure, predicted plasma level at the end of the procedure, and duration of procedure) and sedation depth (proportion of time with bispectral index < 85 during the procedure) with recovery time after ambulatory procedures.

MATERIALS AND METHODS

Clinical observational study of patients undergoing oral and maxillofacial ambulatory surgery with dexmedetomidine as sole sedative agent. Patients received a loading dose of dexmedetomidine (0.25-1 μg kg^-1) followed by a maintenance infusion (0.2-1.4 μg kg^-1 h^-1) to keep a bispectral index < 85 until 5 min before the end of the procedure, and were transferred to a post-anesthesia care unit until criteria for discharge were met.

RESULTS

Data from 75 patients was analyzed. Sedation depth was directly associated with recovery time (Pearson correlation coefficient [r] = 0.26; p = 0.024). Around 7% of the variation in recovery time was explained by the proportion of time with bispectral index < 85. No association with procedure duration (r = 0.01; p = 0.9), predicted area under the curve (r = 0.1; p = 0.4), or predicted plasma level of dexmedetomidine at the end of the procedure (r = 0.12; p = 0.3) with recovery time was observed.

CONCLUSIONS

Sedation depth with dexmedetomidine could play a role in increasing recovery time after oral and maxillofacial ambulatory surgery. In our study, the pharmacokinetic descriptors of dexmedetomidine did not seem to influence recovery time.

CLINICAL RELEVANCE

Sedation depth with dexmedetomidine could play a role in increasing recovery time after ambulatory procedures.

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.

A Pilot Study Implementing a Protocol Using Dexmedetomidine as a Safe Alternative to Traditional Sedation to Decrease Ventilator Days for Patients Difficult to Extubate

BACKGROUND

Traditional sedation for mechanically ventilated patients causes delirium, which increases the patients' length of stay while hospitalized. When extubation is attempted, these medications must be discontinued because of the side effect of respiratory depression, leaving patients anxious and agitated, delaying extubation and prolonging the need for mechanical ventilation. Dexmedetomidine is a safe alternative sedative that does not cause delirium or respiratory depression. During the weaning process, dexmedetomidine can be continued, allowing the patient to remain calm and successfully extubated.

OBJECTIVES

The aim of this study is to decrease the length of stay for mechanically ventilated patients by implementing a dexmedetomidine protocol for difficult-to-extubate patients during the weaning process.

METHODS

A preintervention/postintervention design pilot study was done comparing the patient mean of length of stay on mechanical ventilation. A Mann-Whitney U test was used because of the small sample size.

RESULTS

Over the 3-month implementation period, 15 patients received dexmedetomidine. None of the patients experienced adverse reactions while on dexmedetomidine. There was a trend of decreasing mechanical ventilation length of stay but no significant difference was noted between the preimplementation and postimplementation groups.

CONCLUSION

Dexmedetomidine was a safe alternative to traditional sedation for difficult-to-extubate patients when a bolus dose was not given.

Managing the Rising Costs and High Drug Expenditures in Critical Care Pharmacy Practice

Pharmaceutical costs for patients in the intensive care unit (ICU) constitute a large portion of hospital drug budgets. Unfortunately, prices for medications commonly used in the ICU are on the rise for a variety of reasons. In particular, the U.S. Food and Drug Administration's Unapproved Drugs Initiative, generic manufacturers cornering the marketplace, drug shortages, and regulatory device changes are major drivers of pharmaceutical price escalation affecting costs in the ICU. Furthermore, traditional high acquisition cost items still pose challenges to controlling costs. To offer strategies to mitigate the rising costs of pharmaceuticals in the ICU setting, we searched the PubMed/Medline and International Pharmaceutical Abstracts databases and other related sources to identify published cost-saving protocols concerning specific medications that are affected by rising prices or have traditional high acquisition costs. In the absence of specific protocols, we offer possible cost-saving initiatives based on published literature regarding specific agents or based on our own diverse set of experiences. Finally, we review suggested clinical and operational activities at an institutional level to address these rising drug costs in the ICU setting.

Sedation/drugs used in intensive care sedation

PURPOSE OF REVIEW

There is recognition that the use of sedative drugs in critically ill patients is potentially harmful, particularly in relation to ICU delirium and clinical outcomes. In that context, there is an increasing interest in maintaining light sedation, the use of non-gamma-aminobutyric acid agonist agents and antipsychotics.

RECENT FINDINGS

The sedative drugs currently available have limitations relating to duration of action, cost or variability in response. Recent reviews and meta-analyses comparing sedatives in ICU patients differ in their findings depending on whether trials in elective cardiac surgical patients are included. Dexmedetomidine does appear to reduce the number of ventilator days in the less sick critically ill patient. There is currently no evidence to support the routine use of antipsychotics in ICU patients to prevent or treat delirium, although they will reduce agitation and they appear to be well tolerated when used in the critically ill patient. Sedation protocols and early mobilization reduce the use of sedative drugs and improve some outcomes but are challenging to implement in practice.

SUMMARY

The bedside clinician needs to balance the need to sedate the patient and maintain life-saving support, while keeping their patient responsive, cooperative and pain free.

Comparison of three sedation regimens for drug-induced sleep endoscopy

PURPOSE

Drug-induced sleep endoscopy (DISE) allows for direct airway observation in patients with obstructive sleep apnea. This study compared the safety profiles and efficacies of three regimens for DISE.

METHODS

Sixty-six patients were randomly assigned to receive propofol alone (n = 22), a propofol-remifentanil combination (n = 22), or a dexmedetomidine-remifentanil combination (n = 22). Remifentanil was infused at a concentration of 1.5 ng·ml(-1) in the propofol-remifentanil and dexmedetomidine-remifentanil groups, whereas saline was infused in the propofol group. The propofol and propofol-remifentanil groups received propofol at a starting concentration of 1.0 μg·ml(-1), then 0.1 μg·ml(-1) increments at 5 min intervals. The dexmedetomidine-remifentanil group received 1.0 μg·kg(-1) loading dose of dexmedetomidine for 10 min and then 0.2 μg·kg(-1)·h(-1) increments at 5 min intervals.

RESULTS

The incidence of oxygen desaturation was significantly higher in the propofol-remifentanil group compared with that of the dexmedetomidine-remifentanil group (77 vs. 45%, respectively, P = 0.024). Even with a maximum dose of dexmedetomidine (1.4 μg·kg(-1)·h(-1)), 50% of the dexmedetomidine-remifentanil group did not reach sufficient sedation and required additional propofol. Cough reflex occurred in five patients of propofol group and in neither of the other groups (P = 0.004).

CONCLUSIONS

The propofol-remifentanil combination was associated with a higher incidence of desaturation. The dexmedetomidine-remifentanil combination was associated with inadequate sedation in one half of the patients, even though it produced less respiratory depression. Addition of remifentanil reduced the cough reflex.

Recent advances in multidisciplinary critical care

The intensive care unit is a work environment where superior dedication is crucial for optimizing patients' outcomes. As this demanding commitment is multidisciplinary in nature, it requires special qualities of health care workers and organizations. Thus research in the field covers a broad spectrum of activities necessary to deliver cutting-edge care. However, given the numerous research articles and education activities available, it is difficult for modern critical care clinicians to keep up with the latest progress and innovation in the field. This article broadly summarizes new developments in multidisciplinary intensive care. It provides elementary information about advanced insights in the field via brief descriptions of selected articles grouped by specific topics. Issues considered include care for heart patients, mechanical ventilation, delirium, nutrition, pressure ulcers, early mobility, infection prevention, transplantation and organ donation, care for caregivers, and family matters.