William T. Denman

Pediatric Evaluation of the Bispectral Index (bis) Monitor and Correlation of Bis with End-tidal Sevoflurane Concentration in Infants and Children

The bispectral index (BIS) has been developed in adults and correlates well with clinical hypnotic effects of anesthetics. We investigated whether BIS reflects clinical markers of hypnosis and demonstrates agent dose-responsiveness in infants and children. In an observational arm of this study, BIS values in children undergoing general anesthesia were observed and compared with similar data collected previously in a study of adults. In a second arm of the study, a range of steady-state end-tidal concentrations of sevoflurane was administered and corresponding BIS documented. Data were examined for differences between infants (0–2 yr) and children (2–12 yr). No difference was seen in BIS values in children before induction, during maintenance, and on emergence compared with adult values. There was no difference in BIS between infants and children at similar clinical levels of anesthesia. In children and infants, BIS was inversely proportional to the end-tidal concentration of sevoflurane. The sevoflurane concentration for a BIS = 50 (95% confidence interval) was significantly different: 1.55% (1.40–1.70) for infants versus 1.25% (1.12–1.37) for children. Although validation with specific behavioral end points was not possible, BIS correlated with clinical indicators of anesthesia in children as it did in adults: as depth of anesthesia increased, BIS diminished. BIS correlated with sevoflurane concentration in infants and children. The concentration-response difference between infants and children was consistent with data showing that minimum alveolar concentration is higher in children less than 1 yr of age. Implications: The use of bispectral index (BIS) during general anesthesia improves the titration of anesthetics in adults. The data from this study suggest that the same equipment and method of electroencephalogram analysis may be applied to infants and children.

Safety and efficacy of intranasal ketamine for the treatment of breakthrough pain in patients with chronic pain: A randomized, double-blind, placebo-controlled, crossover study

&NA; Few placebo‐controlled trials have investigated the treatment of breakthrough pain (BTP) in patients with chronic pain. We evaluated the efficacy and safety of intranasal ketamine for BTP in a randomized, double‐blind, placebo‐controlled, crossover trial. Twenty patients with chronic pain and at least two spontaneous BTP episodes daily self‐administered up to five doses of intranasal ketamine or placebo at the onset of a spontaneous BTP episode (pain intensity ≥5 on a 0–10 scale). Two BTP episodes at least 48 h apart were treated with either ketamine or placebo. Patients reported significantly lower BTP intensity following intranasal ketamine than after placebo (P<0.0001), with pain relief within 10 min of dosing and lasting for up to 60 min. No patient in the ketamine group required his/her usual rescue medication to treat the BTP episode, while seven out of 20 (35%) patients in placebo group did (P=0.0135). Intranasal ketamine was well tolerated with no serious adverse events. After ketamine administration, four patients reported a transient change in taste, one patient reported rhinorrhea, one patient reported nasal passage irritation, and two patients experienced transient elevation in blood pressure. A side effect questionnaire administered 60 min and 24 h after drug or placebo administration elicited no reports of auditory or visual hallucinations. These data suggest that intranasal administration of ketamine provides rapid, safe and effective relief for BTP.

Radiologic Localization of the Laryngeal Mask Airway in Children

In the absence of data on the anatomic localization of the cuff of the laryngeal mask airway (LMA) in children, radiologic images were obtained from 50 infants and children (aged 1 month to 15 yr) undergoing diagnostic radiologic procedures during halothane and N2O:O2 anesthesia. In 46 patients, the cuff of the LMA was in the pharynx and covered the laryngeal opening. The upper (proximal) section was adjacent to the base of the tongue at the level of C1 or C2 vertebrae pushing the tongue forward and its lower (distal) end was in the inferior recesses of the hypopharynx at the levels of C4 to T1 vertebrae. The cuff of LMA at this position between the base of the tongue above the epiglottis and below the laryngeal opening, covered the laryngeal aperture, forming a low pressure seal at the entrance of the larynx. In 37 of these 46 patients, a posterior deflection of the epiglottis was noted (< 45 degrees), and in only 9, the epiglottis was in the anatomic position. In four patients, the cuff of the LMA was located in the oropharynx. No correlation was found between the size of the LMA and the position of the epiglottis with respect to end-tidal CO2, respiratory rate, or the leak pressures. The size of the LMA, its anatomic location, and the position of the epiglottis had no significant effect on the respiratory parameters of spontaneously breathing children.

Continuous Lumbar Plexus Block Provides Improved Analgesia With Fewer Side Effects Compared With Systemic Opioids After Hip Arthroplasty: A Randomized Controlled Trial

Background and Objectives: A single injection lumbar plexus block for acute pain management after hip surgery is usually limited to the immediate postoperative period. We conducted a randomized controlled trial to determine the effect of a continuous lumbar plexus block on perioperative opioid requirements and pain intensity. Methods: Adult patients undergoing elective hip arthroplasty under general anesthesia were randomized to continuous lumbar plexus block combined with patient-controlled analgesia (PCA) or PCA only for postoperative pain. Patients allocated to the lumbar plexus block had the catheter placed before surgery. Patients were followed for 36 hours. Perioperative opioid requirement was the primary outcome; secondary outcomes included assessment of pain intensity, patient and surgeon satisfaction with the analgesic technique, and occurrence of nausea and vomiting. Results: Seventeen patients were randomized to each treatment group. Compared with patients in the PCA group, patients in the continuous lumbar plexus block group required less morphine (12 mg) (95% CI, −12.9 to −3.9), had on average less pain (−2.1 units on a 0 to 10 scale) (95% CI, −3.8 to −1.1), were more satisfied with their analgesic technique, and experienced less nausea and vomiting. One patient in the continuous lumbar plexus block developed a delayed paresis and 1 patient in the PCA group developed respiratory depression. Conclusions: Continuous lumbar plexus block combined with PCA is superior to PCA alone for postoperative pain management following hip replacement. It reduces opioid requirements, opioid related side effects, and enhances patient satisfaction. However, additional research is required to determine its safety in light of the neurologic injury observed.

A comparison of the intubation conditions between mivacurium and rocuronium during balanced anesthesia.

Background Comparisons of the intubation conditions with mivacurium and rocuronium from previous reports are confounded by the use of varied induction regimens. The authors compared intubation conditions of mivacurium, rocuronium, and a placebo at 90 s and their recovery profiles during anesthesia with nitrous oxide, oxygen, and propofol. Methods After induction with midazolam, fentanyl, and propofol in a randomized blinded study, 100 patients received one of the following treatments: 0.25 mg/kg mivacurium in divided doses (0.15 mg/kg followed by 0.1 mg/kg 30 s later); 0.45, 0.6, 0.9, or 1.2 mg/kg rocuronium; or placebo. Evoked thumb adduction was measured throughout. Intubation was attempted 90 s after the initial dose of mivacurium and other treatment doses by a “blinded” physician. Intubating conditions were graded as excellent, good, poor, or not possible. Spontaneous recovery was studied until a 25% initial twitch height was reached. Mean arterial blood pressure and heart rate changes between groups were determined before induction through 6 min after administration of the study drugs. Results There were no important changes or intergroup differences in mean arterial blood pressure and heart rate. Intubation conditions were good or excellent for both mivacurium and rocuronium at the 0.9 mg/kg dose (93%) and at the 1.2 mg/kg dose (100%). Rocuronium at the 0.6 mg/kg dose was excellent in 27% of patients, whereas rocuronium at the 0.45 mg/kg dose had the least number of excellent conditions and the most poor or not possible assessments. Patients given placebo could not be intubated. Times to maximum blockade for 0.9 and 1.2 mg/kg rocuronium were the shortest. The times to 25% recovery for 0.6 mg/kg rocuronium (mean +/‐ SD = 27 +/‐ 8.6 min), 0.9 mg/kg (43.1 +/‐ 10.8), and 1.2 mg/kg (62.3 +/‐ 17.4 min) were significantly longer than were those for mivacurium (17.4 +/‐ 6.2 min). Conclusions Mivacurium in a 0.25 mg/kg divided dose and rocuronium at 0.9 mg/kg and 1.2 mg/kg provide good or excellent intubation conditions at 90 s in most patients. Rocuronium was faster in onset at the higher doses (0.9 and 1.2 mg/kg) but had more prolonged recovery times to 25% single twitch height.

Pulsed laser treatment in children and the use of anesthesia

BACKGROUND The rationale for choosing certain anesthetic options in children when they are being treated with pulsed lasers is unclear. OBJECTIVE Our purpose was to assess the safety and side effects of general anesthesia in the treatment of vascular lesions and to compare this to treatment outcome in the office setting. METHODS We carried out a retrospective chart review of 179 patients, with an age range of 5 weeks to 18 years, who received laser treatment and underwent different anesthetic modalities. The age of the patient and the size, location, and severity of the vascular lesion were also noted. RESULTS The factors determining the type of anesthesia to use included (1) the age of the patient, (2) the number of treatments, and (3) the size and location of the lesion. Our data showed minimal risk and sequelae of general anesthesia in the treatment of vascular lesions in children. CONCLUSION Proper selection of anesthesia is a key factor in dealing with children. Office surgery can be performed safely when small lesions are treated. The use of general anesthesia in the treatment of port-wine stains in children does not appear to be accompanied by increased risk.

Changing Patterns of Hospital Length of Stay After Orthognathic Surgery

PURPOSE The purpose of this study was to estimate the hospital length of stay (LOS) and identify factors associated with LOS in orthognathic surgery patients. MATERIALS AND METHODS Using a retrospective cohort study design, we enrolled a sample composed of patients who underwent orthognathic surgery at Massachusetts General Hospital between January 1994 and July 2006. The primary predictor variables were fixation type (rigid/nonrigid), anesthesia technique (hypotensive/normotensive), and perioperative steroid use (yes/no). The outcome variable was LOS. Descriptive statistics were computed for all variables. Bivariate analyses were used to identify factors associated with duration of LOS with P values less than .15. Multiple regression modeling was used to assess the relationship between the primary predictor variables and LOS. The level of statistical significance was set at P less than .05. RESULTS The study sample was comprised of 627 subjects (58.5% female) with a mean age of 26.1 +/- 10.2 years. The overall mean LOS was 1.7 +/- 1.2 days. During the study period, LOS decreased from 2.3 to 1.3 days (P < .001). In the adjusted multiple regression model, rigid fixation, procedure type, and length of operation were statistically significantly associated with LOS (P < .05). CONCLUSION The results of this study indicate that individual variables associated with duration of LOS are complexity of the orthognathic procedure and type of fixation used. In the multiple logistic regression model, LOS decreases significantly when rigid fixation, hypotensive anesthesia, and perioperative steroids are used in combination.

Successful use of bivalirudin for cardiopulmonary bypass in a patient with heparin-induced thrombocytopenia.

PATIENTS WITH HEPARIN-induced thrombocytopenia (HIT) presenting for cardiac surgery requiring cardiopulmonary bypass (CPB) present a unique clinical challenge. Re-exposure to heparin carries significant risks such as increased bleeding or life-threatening thrombosis.1-4 An alternative method of anticoagulation is essential when considering surgery in this group of patients. The options available for anticoagulation are multiple, and each has limitations depending on the drug and/or the patient’s comorbid conditions. These include but are not limited to sole or combination therapy with ancrod, danaproid (not available in the United States), lepirudin, argatroban, platelet IIb/IIIa inhibitors, prostacyclin, heparin, or low-molecular-weight heparin. A new alternative, bivalirudin (Angiomax, The Medicines Company, Cambridge, MA), is a thrombin-specific anticoagulant approved for use in percutaneous coronary angioplasty. Bivalirudin has a half-life of approximately 25 minutes and a rapid plasma clearance ( 3.4 mL/min) via a combination of renal and proteolytic mechanisms.5,6 The authors present a case of a patient with severe aortic insufficiency, renal insufficiency, cirrhosis, and HIT who required aortic valve replacement and underwent successful CPB with bivalirudin anticoagulation.

Comparison of oscillation with three other methods for measuring nasal airways resistance

In this study we have compared the sensitivity and reproducibility of nasal airways resistance measurements made using an oscillometer, with those made by passive anterior, active anterior and active posterior rhinomanometry. Nasal airways resistance values were compared in 12 patients with rhinitis and 15 normal subjects, of whom ten had additional measurements after a vasoconstrictor spray, oxymetazoline. The coefficients of variation of 6-8 technically satisfactory measurements were 9-19%. The decongestant effect of oxymetazoline was detected by all methods, with no decrease in reproducibility. Post vasoconstrictor nasal airways resistance fell by 28% (passive anterior), 35% (active anterior), 36% (active posterior) and 58% (oscillometry). In conclusion, the oscillation method for deriving nasal airways resistance is a useful, new, simple and noninvasive way of assessing nasal airways patency. Results compare favourably with other, more established techniques.

The PediSedate® device, a novel approach to pediatric sedation that provides distraction and inhaled nitrous oxide: clinical evaluation in a large case series

Background:  Pediatric sedation is of paramount importance but can be challenging. Fear and anticipatory anxiety before invasive procedures often lead to uncooperativeness. A novel device (PediSedate®) provides sedation through a combination of inhaled nitrous oxide and distraction (video game). We evaluated the acceptability and safety of the PediSedate® device in children.