Pharmacokinetic and Pharmacodynamic Characteristics of??Medications Used for Moderate Sedation

Dexmedetomidine: a review of its use for sedation in mechanically ventilated patients in an intensive care setting and for procedural sedation

Dexmedetomidine (Precedex®), a pharmacologically active dextroisomer of medetomidine, is a selective α(2)-adrenergic receptor agonist. It is indicated in the US for the sedation of mechanically ventilated adult patients in an intensive care setting and in non-intubated adult patients prior to and/or during surgical and other procedures. This article reviews the pharmacological properties, therapeutic efficacy and tolerability of dexmedetomidine in randomized, double-blind, placebo-controlled, multicentre studies in these indications. Post-surgical patients in an intensive care setting receiving dexmedetomidine required less rescue sedation with intravenous propofol or intravenous midazolam to achieve and/or maintain optimal sedation during the assisted ventilation period than placebo recipients, according to two randomized, double-blind, multinational studies. Moreover, significantly more dexmedetomidine than placebo recipients acquired and/or maintained optimal sedation without rescue sedation. Sedation with dexmedetomidine was also effective in terms of the total dose of morphine administered, with dexmedetomidine recipients requiring less morphine than placebo recipients; with regard to patient management, dexmedetomidine recipients were calmer and easier to arouse and manage than placebo recipients. Intravenous dexmedetomidine was effective as a primary sedative in two randomized, double-blind, placebo-controlled, multicentre studies in adult patients undergoing awake fibre-optic intubation or a variety of diagnostic or surgical procedures requiring monitored anaesthesia care. In one study, significantly fewer dexmedetomidine than placebo recipients required rescue sedation with intravenous midazolam to achieve and/or maintain optimal sedation; conversely, in another study, rescue sedation with intravenous midazolam was not required by significantly more dexmedetomidine than placebo recipients. Primary sedation with intravenous dexmedetomidine was also effective in terms of the secondary efficacy endpoints, including the mean total dose of midazolam and fentanyl administered and the percentage of patients requiring further sedation (in addition to dexmedetomidine or placebo and midazolam), with, for the most part, significant between-group differences observed in favour of dexmedetomidine over placebo. In general, no significant differences were observed between the dexmedetomidine and placebo treatment groups in the anaesthesiologists' assessment of ease of intubation, haemodynamic stability, patient cooperation and/or respiratory stability. Intravenous dexmedetomidine is generally well tolerated when utilized in mechanically ventilated patients in an intensive care setting and for procedural sedation in non-intubated patients. Dexmedetomidine is associated with a lower rate of postoperative delirium than midazolam or propofol; it is not associated with respiratory depression. While dexmedetomidine is associated with hypotension and bradycardia, both usually resolve without intervention. Thus, intravenous dexmedetomidine provides a further option as a short-term (<24 hours) primary sedative in mechanically ventilated adult patients in an intensive care setting and in non-intubated adult patients prior to and/or during surgical and other procedures.

Perspectives on the role of fospropofol in the monitored anesthesia care setting

Monitored anesthesia care (MAC) is a safe, effective, and appropriate form of anesthesia for many minor surgical procedures. The proliferation of outpatient procedures has heightened interest in MAC sedation agents. Among the most commonly used MAC sedation agents today are benzodiazepines, including midazolam, and propofol. Recently approved in the United States is fospropofol, a prodrug of propofol which hydrolyzes in the body by alkaline phosphatase to liberate propofol. Propofol liberated from fospropofol has unique pharmacological properties, but recently retracted pharmacokinetic (PK) and pharmacodynamic (PD) evaluations make it difficult to formulate clear conclusions with respect to fospropofol's PK/PD properties. In safety and efficacy clinical studies, fospropofol demonstrated dose-dependent sedation with good rates of success at doses of 6.5 mg/kg along with good levels of patient and physician acceptance. Fospropofol has been associated with less pain at injection site than propofol. The most commonly reported side effects with fospropofol are paresthesia and pruritus. Fospropofol is a promising new sedation agent that appears to be well suited for MAC sedation, but further studies are needed to better understand its PK/PD properties as well its appropriate clinical role in outpatient procedures.

Review of propofol and auxiliary medications used for sedation

The sedative-hypnotic propofol (2,6-diisopropylphenol) is being increasingly used for sedation during painful diagnostic and therapeutic procedures in adults and children. The purpose of this article is to present a general overview of the use of propofol for endoscopic sedation. Advantages and disadvantages of using propofol for sedation, as well as its pharmacokinetics, preparation for use, dosing for endoscopic sedation, auxiliary sedative and analgesic medication options, methods of administering, adverse effects with interventions, recovery, and patient-physician satisfaction are discussed. Finally, next steps necessary to optimize future use of propofol are suggested.

A comparison of dexmedetomidine versus midazolam for sedation, pain and hemodynamic control, during colonoscopy under conscious sedation

OBJECTIVE

The intent of our study was to compare the effects of dexmedetomidine versus midazolam on perioperative hemodynamics, sedation, pain, satisfaction and recovery scores during colonoscopy.

MATERIAL AND METHODS

A total of 60 ASA I-II patients, between 20 and 80 years of age were included in the study. Patients were randomly assigned to two groups. Midazolam 0.05 mg kg(-1) and fentanyl citrate 1 microg kg(-1) were administered intravenously to cases in Group I (n = 30). An initial loading dose of 1 microg kg(-1) dexmedetomidine was administered intravenously in 10 min to cases in Group II (n = 30) before the procedure and as a continuous infusion dose of 0.5 microg kg(-1) h(-1) just before the procedure started. Also 1 microg kg(-1) fentanyl citrate was administered intravenously immediately before the procedure. Peripheral oxygen saturation (S(pO2)), mean arterial pressure (MAP), heart rate (HR), Ramsay Sedation Scale (RSS), Numeric Rating Scale (NRS) scores and colonoscopist satisfaction scores of the cases were recorded.

RESULTS

Although statistically significant values were not detected between the two groups with regard to mean arterial pressure, in Group I heart rates were higher and S(pO2) scores were lower in a statistically significant manner. When the groups were compared with regard to RSS, the RSS scores of Group I at the 10th and 15th minutes were significantly lower than Group II. There was no statistically significant difference between the two groups when compared with regard to NRS scores. Satisfaction scores were significantly lower in Group II.

CONCLUSION

Dexmedetomidine provides more efficient hemodynamic stability, higher Ramsay sedation scale scores, higher satisfaction scores and lower NRS scores in colonoscopies. According to our results we believe that dexmedetomidine can be used safely as a sedoanalgesic agent in colonoscopies.

Breakdown in cortical effective connectivity during midazolam-induced loss of consciousness

By employing transcranial magnetic stimulation (TMS) in combination with high-density electroencephalography (EEG), we recently reported that cortical effective connectivity is disrupted during early non-rapid eye movement (NREM) sleep. This is a time when subjects, if awakened, may report little or no conscious content. We hypothesized that a similar breakdown of cortical effective connectivity may underlie loss of consciousness (LOC) induced by pharmacologic agents. Here, we tested this hypothesis by comparing EEG responses to TMS during wakefulness and LOC induced by the benzodiazepine midazolam. Unlike spontaneous sleep states, a subject's level of vigilance can be monitored repeatedly during pharmacological LOC. We found that, unlike during wakefulness, wherein TMS triggered responses in multiple cortical areas lasting for >300 ms, during midazolam-induced LOC, TMS-evoked activity was local and of shorter duration. Furthermore, a measure of the propagation of evoked cortical currents (significant current scattering, SCS) could reliably discriminate between consciousness and LOC. These results resemble those observed in early NREM sleep and suggest that a breakdown of cortical effective connectivity may be a common feature of conditions characterized by LOC. Moreover, these results suggest that it might be possible to use TMS-EEG to assess consciousness during anesthesia and in pathological conditions, such as coma, vegetative state, and minimally conscious state.

Fospropofol: a new sedative-hypnotic agent for monitored anesthesia care

OBJECTIVE

To summarize the published clinical data on fospropofol, critically review the safety and efficacy information, and provide pertinent information for formulary review.

DATA SOURCES

Data were collected from searches of MEDLINE (1966-June 30, 2009), EMBASE (1974-June 30, 2009), bibliographies of manuscripts, and www.fda.gov. Key search terms included fospropofol, Lusedra, Aquavan, sedative-hypnotic, and monitored anesthesia care.

STUDY SELECTION AND DATA EXTRACTION

All Phase 1, Phase 2, and Phase 3 clinical trials studying the safety and efficacy of fospropofol were reviewed.

DATA SYNTHESIS

Fospropofol is a water-soluble prodrug of propofol, a potent sedative-hypnotic agent. Propofol is highly lipophilic and is formulated in lipid-containing solvents, which have known disadvantages, including pain on injection, narrow therapeutic window with the potential to cause deep sedation, high lipid intake during long-term sedation, and risk of infection resulting from bacterial contamination. Due to its water solubility, fospropofol eliminates some of the known lipid emulsion-associated disadvantages of propofol and provides a more predictable peak onset of activity and more gradual recovery to a full state of consciousness. The pharmacokinetic and pharmacodynamic profiles of fospropofol make it an attractive agent for sedation for procedures of short duration. Unfortunately, the number of patients studied has been relatively small and the amount of safety data is limited. Of concern are reports of hypoxemia and hypotension; these reports are limited in number, but the episodes are serious and may require acute intervention. Although fospropofol holds promise for procedural sedation, due to limited safety data, the Food and Drug Administration has limited approval of fospropofol to monitored anesthesia care in patients undergoing diagnostic or therapeutic procedures.

CONCLUSIONS

Fospropofol is a viable addition to the class of sedative-hypnotic agents due to the minimization of unwanted adverse effects of propofol and maintenance of a favorable pharmacokinetic profile facilitating sedation, anxiolysis, and rapid recovery. However, there are limited safety data to justify its use without the presence of dedicated anesthesia personnel.

The risk and safety of anesthesia at remote locations: the US closed claims analysis

PURPOSE OF REVIEW

A growing number of procedures are performed outside the operating room. In spite of their relatively noninvasive nature, serious adverse outcomes can occur. We analyzed claims from 1990 and later in the American Society of Anesthesiologists Closed Claims database to assess patterns of injury and liability associated with claims from anesthesia in remote locations (n = 87) compared with claims from operating room procedures (n = 3287).

RECENT FINDINGS

Compared with operating room claims, remote location claims involved older and sicker patients (P < 0.01), with 50% of remote location claims involving monitored anesthesia care. The proportion of claims for death was increased in remote location claims [54 vs. 29% (operating room claims), P < 0.001]. Respiratory damaging events were more common in remote location claims (44 vs. 20%, P < 0.001), with inadequate oxygenation/ventilation the most common specific event (21 vs. 3% in operating room claims, P < 0.001). Remote location claims were more often judged as being preventable by better monitoring (32 vs. 8% for operating room claims, P < 0.001).

CONCLUSION

Data from the American Society of Anesthesiologists, Closed Claims database suggest that anesthesia at remote locations poses a significant risk for the patient, particularly related to oversedation and inadequate oxygenation/ventilation during monitored anesthesia care. Similar anesthesia and monitoring standards and guidelines should be used in all anesthesia care areas.

Advances in interventional pulmonology

PURPOSE OF REVIEW

Interventional pulmonology is a rapidly expanding field offering less invasive therapeutic procedures for significant pulmonary problems. Many of the therapies may be new for the anesthesiologist. Although less invasive than surgery, some of these procedures will carry significant risks and complications. The team approach by anesthesiologist and pulmonologist is key to the success of these procedures.

RECENT FINDINGS

Many modalities for central airway obstruction have emerged, including the expanding application of airway stenting procedures. Diagnostic bronchoscopy with ultrasound guidance promises great advances in lung cancer staging. New bronchoscopic treatments of asthma and emphysema are actively under investigation. Advances in anesthetic agents and techniques for interventional pulmonology procedures have also occurred.

SUMMARY

This review is intended to familiarize the anesthesiologist with current and rising therapeutic modalities for pulmonary disease. Knowledge of interventional pulmonology facilitates planning and preparation for well tolerated and effective procedures.

Predictors of hemodynamic compromise with propofol during defibrillator implantation: a single center experience

BACKGROUND

Intra-operative hypotension has been reported in cardiac resynchronization therapy defibrillator (CRT-D) clinical trials but this phenomenon is not well characterized. The purpose of this study was to understand the frequency and determinants of intra-operative hypotension in patients undergoing defibrillator implantations.

METHODS

We retrospectively reviewed clinical data of all CRT-D implantations over a 21-month period. We compared a randomly selected contemporaneous group undergoing implantable cardiac defibrillator (ICD) implantations as a reference group. Procedure protocol involved intra-arterial blood pressure monitoring throughout the case. Lidocaine (1%) was routinely used along with propofol for sedation in all patients. Procedure time was defined as the time from initial administration of lidocaine for arterial line access, to completion of defibrillator pocket closure. Cumulative dose of propofol was calculated in each patient. Hypotension was defined as a fall in the systolic blood pressure of >or=30% from baseline or a systolic blood pressure of <or=80 mm Hg for >3 min. CRT-D and ICD patients were divided into hypotensive and non-hypotensive subsets.

RESULTS

The incidence of hypotension in the CRT-D group (N = 100) was 56%, as compared to 40% in the ICD group (N = 97). The mean duration of procedure in the CRT-D group was 114 +/- 95 min in the hypotensive subset versus 69 +/- 31.9 min in the non-hypotensive subset (p = 0.0015). The mean NYHA class in the hypotensive subset of the CRT-D group was 2.85 +/- 1.2 vs 2.2 +/- 1.5 in the non-hypotensive subset (p = 0.0179). Cumulative dose of propofol in the hypotensive subset of the CRT-D group was 386 +/- 22 mg, while that in the non hypotensive subset was 238.3 +/- 17 mg (p < 0.0001). Creatinine clearance in the hypotensive subset of the CRT-D group was 63.8 +/- 12.8 ml/min, while that in the non-hypotensive subset was 78.7 +/- 23.5 ml/min (p = 0.003). Patients in the CRT-D group who developed hypotension had a lower left ventricular ejection fraction of 21.1 +/- 10.2% versus 29 +/- 14.8% in the non-hypotensive subset (p = 0.0035).

CONCLUSIONS

Hypotension is a common occurrence during defibrillator implantation under conscious sedation. Risk factors for significant hypotension include: higher NYHA class, lower left ventricular ejection fraction, lower creatinine clearance, higher doses of propofol and longer procedure times.

Fospropofol Disodium

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing inservices. A comprehensive target drug utilization evaluation (DUE) is also provided each month. With a subscription, the monographs are sent in print and are also available online. Monographs can be customized to meet the needs of a facility. Subscribers to The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X.). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The March 2009 monograph topics are plerixafor, degarelix, armodafinil, iloperidone, and lasofoxifene. The DUE is on degarelix.

Fospropofol disodium injection for the sedation of patients undergoing colonoscopy

Sedation plays a central role in making colonoscopy tolerable for patients and feasible for the endoscopist to perform. The array of agents used for endoscopic sedation continues to evolve. Fospropofol (FP), a prodrug of propofol with a slower pharmacokinetic profile, is currently under evaluation for use during endoscopic procedures. Preliminary data suggests that FP dosed at 6.5 mg/kg is well tolerated by most patients with perineal paresthesias being the most commonly experienced adverse effect. This article will examine the current literature on the use of FP for the sedation of patients undergoing colonoscopy, highlighting the pharmacokinetics, pharmacodynamics, risks, and common adverse events associated with the novel sedative/hypnotic.

Clinical trial: a dose-response study of fospropofol disodium for moderate sedation during colonoscopy

BACKGROUND

An effective agent is needed that provides rapid onset of sedation and quick recovery for patients undergoing colonoscopy.

AIM

To assess the efficacy and safety of fospropofol disodium in providing sedation in patients undergoing colonoscopy.

METHODS

A randomized, double-blind, multicentre trial evaluated 127 adult patients who received fospropofol (2, 5, 6.5 or 8 mg/kg) or midazolam 0.02 mg/kg following pre-treatment with fentanyl. Supplemental doses of study medication were allowed to reach a Modified Observer's Assessment of Alertness/Sedation scale score < or =4. Efficacy end points included sedation success, measures of clinical benefit, sedation, and recovery as well as patient- and doctor-rated satisfaction.

RESULTS

Fospropofol produced a significant dose-dependent increase in sedation success from 24% (2 mg/kg), 35% (5 mg/kg) and 69% (6.5 mg/kg) to 96% (8 mg/kg; P < 0.001). There were also dose-dependent trends for time to sedation, requirements for alternative sedative medication, supplemental doses of sedative and fentanyl, time to ready for discharge and doctor-rated satisfaction scores. Fospropofol was well tolerated, with most adverse events mild-to-moderate in severity.

CONCLUSION

The 6.5 mg/kg dose of fospropofol provides the ideal balance of efficacy and safety for patients undergoing colonoscopy and has been selected for phase 3 clinical development.

A comparison of dexmedetomidine and midazolam for sedation in third molar surgery

This randomised, double-blind study compared dexmedetomidine and midazolam for intravenous sedation during third molar surgery under local anaesthesia. Sixty patients received either dexmedetomidine (up to 1 microg x kg(-1)) or midazolam (up to 5 mg), which was infused until the Ramsay Sedation Score was four or the maximum dose limit was reached. Intra-operative vital signs, postoperative pain scores and analgesic consumption, amnesia, and satisfaction scores for patients and surgeons, were recorded. Sedation was achieved by median (IQR (range)) doses of 47 microg (39-52 (25-76)) or 0.88 microg x kg(-1) (0.75-1.0 (0.6-1.0)) dexmedetomidine, and 3.6 mg (3.3-4.4 (1.9-5.0)) or 0.07 mg x kg(-1) (0.055-0.085 (0.017-0.12)) midazolam. Heart rate and blood pressure during surgery were lower in dexmedetomidine group. There was no significant difference in satisfaction or pain scores. Midazolam was associated with greater amnesia. Dexmedetomidine produces comparable sedation to midazolam.