The dexmedetomidine concentration required after remifentanil anesthesia is three-fold higher than that after fentanyl anesthesia or that for general sedation in the ICU.

PURPOSE: The general dexmedetomidine (DEX) concentration required for sedation of intensive care unit patients is considered to be approximately 0.7 ng/mL. However, higher DEX concentrations are considered to be required for sedation and/or pain management after major surgery using remifentanil. We determined the DEX concentration required after major surgery by using a target-controlled infusion (TCI) system for DEX. METHODS: Fourteen patients undergoing surgery for abdominal aortic aneurysms (AAA) were randomly, double-blindly assigned to two groups and underwent fentanyl- or remifentanil-based anesthetic management. DEX TCI was started at the time of closing the peritoneum and continued for 12 hours after stopping propofol administration (M0); DEX TCI was adjusted according to the sedation score and complaints of pain. The doses and concentrations of all anesthetics and postoperative conditions were investigated. RESULTS: Throughout the observation period, the predicted plasma concentration of DEX in the fentanyl group was stable at approximately 0.7 ng/mL. In contrast, the predicted plasma concentration of DEX in the remifentanil group rapidly increased and stabilized at approximately 2 ng/mL. The actual DEX concentration at 540 minutes after M0 showed a similar trend (0.54±0.14 [fentanyl] versus 1.57±0.39 ng/mL [remifentanil]). In the remifentanil group, the dopamine dose required and the duration of intubation decreased, and urine output increased; however, no other outcomes improved. CONCLUSION: The DEX concentration required after AAA surgery with remifentanil was three-fold higher than that required after AAA surgery with fentanyl or the conventional DEX concentration for sedation. High DEX concentration after remifentanil affords some benefits in anesthetic management.

A high dose of dexmedetomidine using the BIS monitor™ for diagnostic and interventional cardiac catheterization in a toddler with congenital heart disease.

Dexmedetomidine (DEX) for sedation in diagnostic and interventional cardiac catheterization (DICC) has been reported to require other drugs or rescue drugs because of its insufficient sedative effect when used alone. We administered DEX and adjusted its dose according to the bispectral index (BIS) monitor™ for DICC in a toddler; consequently, a high dose of DEX had to be administered. The patient was a 1-year and 4-month-old boy who was scheduled to undergo DICC after intracardiac repair. We used DEX alone as the sedative because this was expected to avoid oxygen supply and mechanical ventilation and to produce a safe situation for procedures around the neck. DEX was administered at the dose of 1-15 µg/kg/h according to BIS monitor™; administration of cardiovascular drugs or oxygen supply or assist ventilation, except chin lift, were not needed. The maximum predicted plasma concentration (pCp) of DEX and mean pCp were calculated as 6.1 and 4.1 ng/mL, respectively. A high dose of DEX may be required for DICC sedation, as for MRI sedation, in many cases. Although further studies should be conducted to reveal the merits and demerits of DEX in cardiac catheterization, a high dose of DEX may be useful in some cases.

Dexmedetomidine can stabilize hemodynamics and spare anesthetics before cardiopulmonary bypass.

PURPOSE: We previously confirmed the effectiveness of dexmedetomidine (DEX) for stabilizing hemodynamics as well as sparing anesthetics during anesthetic induction in patients undergoing cardiac surgery (Kunisawa et al. in J Clin Anesth 21:194-199, 1). In this study, we investigated whether these effects of DEX continue until the start of cardiopulmonary bypass (CPB). METHODS: Twenty-two patients with mild to moderate cardiovascular disease were randomized into two groups [DF2 group: DEX dose of 0.7 µg/kg/h after initial dose and effect-site concentration (ESC) of fentanyl of 2 ng/ml; PF4 group: saline and ESC of fentanyl of 4 ng/ml]. Propofol was administered for anesthetic induction and maintenance. Hemodynamics, cardiovascular drugs, ESC of propofol, and cardiovascular responses to skin incision (SI) and sternotomy (St) were measured or calculated. RESULTS: Blood pressure (BP) at the pre-/post-SI periods was higher in the DEX group (137 ± 17/140 ± 16 mmHg) than in the placebo group (85 ± 9/109 ± 24 mmHg). Percent increases in cardiovascular response to SI or St were lower in the DEX group than in the placebo group (for example, 1.9 ± 2.2 vs. 27.4 ± 19.9% in systolic BP due to SI). ESCs of propofol at SI and St in the DEX group were lower than those in the placebo group. CONCLUSIONS: DEX combined with 2 ng/ml fentanyl before CPB can suppress the decrease in blood pressure at the pre- and post-SI periods, can blunt the cardiovascular responses to SI and St, and can spare the required ESC of propofol despite fentanyl concentration, which was half of that in the placebo group.

Administration of dexmedetomidine alone during diagnostic cardiac catheterization in adults with congenital heart disease: two case reports.

We report the clinical management of 2 adults with mental retardation because of trisomy 21 who were sedated with high-dose dexmedetomidine (DEX) alone during diagnostic cardiac catheterization (DCC). The first patient was a 25-year-old man with aortic regurgitation and ventricular septal defect. DEX increased his Ramsay sedation score; however, a high dose and bolus injection of DEX were required to perform an invasive procedure. Cardiovascular drugs were not administered and heart rate was maintained in the low 40s. The maximum predicted plasma concentration (pCp) of DEX was 2.3 ng/mL. The second patient was a 26-year-old woman who had developed hypoxia 20 years after palliative surgery for tetralogy of Fallot. High-dose DEX was administered to keep the bispectral index value below 70 and maintain an immobile state; her maximum pCp of DEX was 4.3 ng/mL. Percutaneous oxygen saturation was kept above 83%, because of the suspicion that DEX may increase the ratio of pulmonary artery flow to systemic artery flow. In both cases, no respiratory system complications occurred despite inspiration of room air, indicating the usefulness of DEX for DCC. However, because of DEX may affect DCC data, it is necessary to pay careful attention to the use of DEX during DCC.

[Effect of the initial loading dose of dexmedetomidine on hemodynamics in pediatric patients undergoing cardiac surgery].

BACKGROUND: We studied the effect of the initial loading dose of dexmedetomidine on hemodynamics in pediatric patient undergoing cardiac surgery. METHODS: This study was on 10 children under ten who were scheduled for elective surgery for repair of the atrial and ventricular septal defect. The induction and maintenance of anesthesia were performed with total intravenous anesthesia (TIVA) using propofol and fentanyl. After closing the sternum, we administered dexmedetomidine as a loading dose of 1 microg x kg(-1) for 10 minutes followed by a maintenance infusion of 0.7 microg x kg(-) x hr(-1). During the study systolic blood pressure, diastolic blood pressure, heart rate, and central venous pressure were measured. RESULTS: There were no significant changes temporalily in heart rate and central venous pressure. Systolic and diastolic blood pressure increased temporalily. They reached the maximum 15 minutes after starting dexmedetomidine. And 30 minutes later they returned to the baseline level. CONCLUSIONS: Any clinical problems leading to a major increase in blood pressure were not encountered. But these results suggest that it is necessary to devise a method of administration of dexmedetomidine in consideration of the patient's condition and the drug effect in severe cases.

[Use of the pentax-AWS in a patient with Cormack 3a difficult airway].

Pentax-AWS (AWS) (Pentax, Japan) is a rigid video laryngoscope with built-in 2.4 inch color CCD monitor paired with a disposal blade. It is developed for management of both normal and difficult airways. We used AWS in a 68-year-old male patient with known (Cormack grade 3a) difficult airway. Patient was sedated with fentanyl and midazolam to the level of Ramsay score 3. Patient's oral cavity was sprayed with 8% lidocaine. ETT placed on side channel of the AWS was connected to respiratory circuit via Bodai suction safe connector. Oxygen 6 l x min(-1) was adminisitered to prevent both desaturation of patient and fogging of blade during intubation procedure. Excessive saliva in the oropharynx was effectively removed with 14 Fr suction catheter through ETT via Bodai suction safe connector". Visualization of the patient's vocal cords was achieved easily (with POGO score 70%). The AWS's suction channel was alternatively used for topical anesthesia route with 10 Fr suction tube, and 4% lidocaine was injected onto the vocal cords. Tracheal intubation was successful uneventfully, and the patient's airway was secured without any postoperative complication.