Soft silicone foam dressing is more effective than polyurethane film dressing for preventing intraoperatively acquired pressure ulcers in spinal surgery patients: the Border Operating room Spinal Surgery (BOSS) trial in Japan.

Preventing intraoperatively acquired pressure ulcers (IAPUs) in patients undergoing spinal surgery in the prone position using a Relton-Hall frame is challenging. We investigated the efficacy of soft silicone foam dressings in preventing IAPUs. A prospective dual-center sham study was conducted among patients undergoing elective spinal surgery in a general hospital and a university hospital in Japan. The incidence of IAPUs that developed when soft silicone foam dressings and polyurethane film dressings were used was compared on two sides in the same patient. IAPUs developed on the chest in 11 of 100 patients (11%). Polyurethane film dressings were associated with a significantly higher rate of IAPUs than soft silicone foam dressings (11 versus 3, P = 0·027). A multivariate logistic regression analysis revealed that a diastolic blood pressure of <50 mmHg (P = 0·025, OR 3·74, 95% confidence interval [CI] 1·18-13·08) and the length of surgery (by 1 hour: P = 0·038, OR 1·61, 95% CI 1·03-2·64) were independently associated with the development of IAPUs. The use of soft silicone foam dressings reduced the risk of IAPUs (P = 0·019, OR 0·23, 95% CI 0·05-0·79) and was more effective than film dressings for preventing IAPUs in spinal surgery patients.

Feasibility of the head-mounted display for ultrasound-guided nerve blocks: a pilot simulator study.

The head-mounted display (HMD) has the potential to improve the quality of ultrasound-guided procedures. The aim of this non-clinical crossover designed study is to evaluate the feasibility of the HMD for ultrasound-guided nerve block. Eight experienced anesthesiologists performed ultrasound-guided peripheral nerve blocks on a training simulator with a standard approach and with an upside-down approach. Each approach was performed with a control conventional method and with an HMD. The ultrasound image and operating field were recorded by video camera. The procedure time and fractional percentage of time with the needle visible on the ultrasound image were determined. The needle insertion times were 10.4 ± 7.2 s with the control method and 6.8 ± 5.3 s with the HMD method for the standard approach (p = 0.03), and 18.1 ± 10.1 with the control method and 11.8 ± 9.5 s with the HMD method for the upside-down approach (p = 0.002). The fractional percentages of time with the needle visible on the ultrasound image were 34.1 ± 20.9 with the control method and 56.5 ± 13.6% with the HMD method for the standard approach (p < 0.001), and 20.1 ± 13.4 with the control method and 38.2 ± 21.2% with the HMD method for the upside-down approach (p = 0.001). In conclusion, this pilot study using a simulation model indicated that the use of an HMD shortened the procedure time and improved the needle visibility on ultrasound.

[Evaluation of Near-Eye Type We 21Ae Display for Ultrasound Guided Central Venogii,Gannulation].

BACKGROUND: Recently several types of head- mounted displays are available for use in the medical field. Because head-mounted display can provide the visualized information without moving direction of eye- sight, ultrasound guided central venous cannulation might be performed more quickly and safer. One of the head-mounted type displays, Near-Eye Display (NED; NED prototype product, JCV Kenwood, Japan) was tested in ultrasound guided central venous cannulation. METHODS: Eleven experienced anesthesiologists per- formed central venous cannulation on the training sim- ulator with NED and with control method (without NED). Ultrasound real time image and operating field were recorded by video camera and analyzed to iden- tify procedure time, success rate and incidence of unintentional posterior venous wall penetration. RESULTS: With NED, although time required for cen- tral venous cannulation was similar to the time with standard method (31.3 ± 8.7 sec with control and 30.2 ±7.9 sec with NED, P=0.61), unintentional posterior wall penetration tended to occur less frequently (21% with control and 9% with NED, P=0.17). DISCUSSIONS AND CONCLUSIONS: As NED can help practitioners to have both insertion field and ultra- sound image visible without moving eyesight, NED might be a promising assist device for the ultrasound guided central venous cannulation.

Etomidate and the Risk of Complications After Cardiac Surgery: A Retrospective Cohort Analysis.

OBJECTIVE: To compare incidence of atrial arrhythmia, duration of care, and major complications after cardiac surgery between patients who received etomidate and those who received other induction agents. DESIGN: Retrospective cohort study utilizing propensity score matching. SETTING: A single academic, tertiary care hospital. PARTICIPANTS: Eight thousand nine hundred seventy-eight patients undergoing coronary artery bypass grafting (CABG), valve, or combined valve/CABG surgery requiring cardiopulmonary bypass between January 2005 and December 2010. INTERVENTIONS: Patients were divided into those who received etomidate at anesthetic induction and those who received another induction agent. Patients given etomidate were propensity-score matched to patients given other induction agents in a 2:1 ratio. MEASUREMENTS AND MAIN RESULTS: Of 8,978 patients who underwent CABG, valve, or combined valve/surgery, 6,313 received etomidate and 2,665 received other induction agents. Among these, the authors successfully matched 4,094 etomidate patients with 2,524 non-etomidate patients. The authors did not find a significant association between receiving etomidate and odds of experiencing postoperative atrial arrhythmia (odds ratio [98.3% confidence interval] of 1.07 [0.92, 1.23], p = 0.29). Etomidate was not associated significantly with either intensive care unit or hospital stay. Etomidate was associated significantly with use of packed red blood cells (odds ratio [99.6% confidence interval] of 1.32 [1.02, 1.70], p = 0.002), but not with use of fresh frozen plasma, platelets, or cryoprecipitate. None of the other complications differed significantly between the groups. CONCLUSIONS: Etomidate was not associated with increased incidence of postoperative atrial arrhythmia or increased intensive care unit or hospital stay.

Microclimate is an independent risk factor for the development of intraoperatively acquired pressure ulcers in the park-bench position: A prospective observational study.

Preventing pressure ulcers is important in patients undergoing procedures in the park-bench position. We hypothesized that the microclimate around the skin is a significant risk factor for developing pressure ulcers. This research continuously assessed factors of the microclimate in terms of skin temperature and perspiration as well as the interface pressure in order to determine whether the microclimate is an independent risk factor for the development of park-bench position-related pressure ulcers (PBP-PUs). A prospective observational study was conducted among patients undergoing elective surgery in the park-bench position at a general hospital in the metropolitan area of Japan between April and November 2014. Factors of the microclimate, including skin temperature and perspiration, in addition to the interface pressure were continuously measured throughout surgery. Twenty-nine patients were analyzed (mean age 44.4 ± 13.2 years, male 44.8%). Of these 29 patients, seven (24.1%) developed Category I PBP-PUs. The change in skin temperature from baseline to the end of surgery (2.7 ± 0.3 °C vs. 1.9 ± 0.8 °C) and the average peak pressure (119.1 ± 36.8 mmHg vs. 94.5 ± 23.1 mmHg) were significantly higher in the patients with PBP-PUs than in those without PBP-PUs. There were no significant differences in the amount of perspiration between the two groups. A hierarchical logistic regression analysis showed that the change in skin temperature was significantly related to the development of PBP-PUs (unit = 0.1 °C: odds ratio 1.44, 95% confidential interval 1.09-2.33) when adjusted for the average peak pressure and length of surgery. Our results suggest that a change in skin temperature toward a higher value is an independent risk factor for the development of PBP-PUs. Proper intraoperative management of skin temperature may therefore be a promising candidate as a preventive method against PBP-PU development.

The Effect of Hypothyroidism on a Composite of Mortality, Cardiovascular and Wound Complications After Noncardiac Surgery: A Retrospective Cohort Analysis.

BACKGROUND: We tested the hypothesis that hypothyroidism, as defined by thyroid-stimulating hormone (TSH) concentration, is associated with a severity-weighted composite of mortality and major cardiovascular and infectious complications after noncardiac surgery. METHODS: In this retrospective cohort study, we evaluated adults at the Cleveland Clinic Main Campus between 2005 and 2012, who had had available TSH concentrations within the 6 months before noncardiac surgery. Patients were categorized as (1) hypothyroid (patients who had diagnosis of hypothyroidism any time prior to surgery and increased TSH value (> 5.5 mIU/L) within 6 months prior to surgery); (2) treated (hypothyroid diagnosis and normal TSH concentrations [0.4-5.5 mIU/L]); and (3) euthyroid (no hypothyroid diagnosis and normal TSH concentrations). We conducted pairwise comparisons among the 3 groups using inverse propensity score weighting to control for observed confounding variables. Average relative effect generalized estimating equation model was used for the primary outcome composite of in-hospital cardiovascular morbidity, surgical wound complication or infection, and mortality. Logistic regression and Cox proportional hazards regression were used for secondary outcomes of intraoperative vasopressor use and duration of hospitalization, respectively. RESULTS: We identified 800 hypothyroid patients (median TSH: 8.6 mIU/L [Q1, Q3: 6.5, 13.0]), 1805 treated patients (2.0 mIU/L [1.1, 3.2]), and 5612 euthyroid patients (1.7 mIU/L [1.1, 2.6]). There were no significant differences among the hypothyroid, treated, and euthyroid patients on the primary composite outcome (all P values ≥0.30). Hypothyroid patients were slightly more likely to receive vasopressor during surgery than either treated (odds ratio, 1.17; 99.2% confidence interval [CI], 1.01-1.36) or euthyroid (odds ratio, 1.12; 99.2% CI, 1.02-1.24) patients. Furthermore, hypothyroid patients were slightly but significantly less likely to be discharged at any given postoperative time than treated patients (hazard ratio, 0.92; 99.2% CI, 0.86-0.99). CONCLUSIONS: Hypothyroidism was not associated with worse postoperative mortality, wound, or cardiovascular outcomes in noncardiac patients. Thus, postponing surgery to initiate thyroid replacement therapy in patients with hypothyroidism seems unnecessary.

[Comparison of Tracheal Intubation Performance between Macintosh Direct Laryngoscope and McGRATH® MAC Video Laryngoscope among Anesthesia Trainees].

BACKGROUND: From April 2013, Macintosh direct laryngoscopes (DL) were replaced by McGRATH® MAC video laryngoscopes (VL), and VL were distributed in all of our operating rooms and used as routine first choice devices. Purpose of this study was to compare the success rate of the first attempt tracheal intubation by the trainees with VL and DL. Incidence of tracheal intubation related injuries were also assessed. MATERIALS AND METHODS: We reviewed anesthesia chart database in which tracheal intubations were provided by anesthesia trainees with experience of less than 3 months. Patient demographics, Mallampati classification and tracheal intubation profiles including type of the tracheal tube and devices were recorded. RESULTS AND DISCUSSION: The first attempt success rate was 78.6% with DL and 92.8% with VL (P < 0.001). More than 2 repeated trial incidence was 5.2% with DL and 1.3% with VL (P < 0.001). Incidence of mucosal injury was lower with DL than VL. CONCLUSIONS: VL notably improved the first success rate of tracheal intubation compared with DL among trainees.

Anesthetic induction with etomidate, rather than propofol, is associated with increased 30-day mortality and cardiovascular morbidity after noncardiac surgery.

BACKGROUND: Because etomidate impairs adrenal function and blunts the cortisol release associated with surgical stimulus, we hypothesized that patients induced with etomidate suffer greater mortality and morbidity than comparable patients induced with propofol. METHODS: We evaluated the electronic records of 31,148 ASA physical status III and IV patients who had noncardiac surgery at the Cleveland Clinic. Among these, anesthesia was induced with etomidate and maintained with volatile anesthetics in 2616 patients whereas 28,532 were given propofol for induction and maintained with volatile anesthetics. Two thousand one hundred forty-four patients given etomidate were propensity matched with 5233 patients given propofol and the groups compared on 30-day postoperative mortality, length of hospital stay, cardiovascular and infectious morbidities, vasopressor requirement, and intraoperative hemodynamics. RESULTS: Patients given etomidate had 2.5 (98% confidence interval [CI], 1.9-3.4) times the odds of dying than those given propofol. Etomidate patients also had significantly greater odds of having cardiovascular morbidity (odds ratio [OR] [98% CI]: 1.5 [1.2-2.0]), and significantly longer hospital stay (hazard ratio [95% CI]: 0.82 [0.78-0.87]). However, infectious morbidity (OR [98% CI]: 1.0 [0.8-1.2]) and intraoperative vasopressor use (OR [95% CI] 0.92: [0.82-1.0]) did not differ between the agents. CONCLUSION: Etomidate was associated with a substantially increased risk for 30-day mortality, cardiovascular morbidity, and prolonged hospital stay. Our conclusions, especially on 30-day mortality, are robust to a strong unmeasured binary confounding variable. Although our study showed only an association between etomidate use and worse patients' outcomes but not causal relationship, clinicians should use etomidate judiciously, considering that improved hemodynamic stability at induction may be accompanied by substantially worse longer-term outcomes.

Correlation between bispectral index, observational sedation scale, and lower esophageal sphincter pressure in volunteers using dexmedetomidine or propofol.

BACKGROUND: Many anesthetics reduce lower esophageal sphincter pressure (LESP) and consequently the gastro-esophageal pressure gradient (GEPG); thus they may promote gastro-esophageal reflux and contribute to aspiration pneumonia. Our goals were to evaluate the association between LESP and 2 measures of sedation: bispectral index (BIS) and the responsiveness component of the Observer's Assessment of Alertness score (OAA/S). MATERIAL/METHODS: Eleven healthy volunteers were each sedated on 2 separate days. Subjects were given sedative infusions of increasing target plasma concentrations of dexmedetomidine or propofol. LESP and GEPG were recorded after starting each infusion phase. Generalized estimating equation modeling was used to assess the relationship between LESP and, respectively, BIS and OAA/S. The existence of a drug-dependent association was evaluated within these models by testing an interaction term. Wald tests were used to evaluate the relationships within the models. RESULTS: We found a significant relationship between LESP and BIS (P=0.0043) after adjusting for the main effect of sedative type--a deepening of sedation as measured by a decrease in BIS of 10% was associated with a decrease [Bonferroni-adjusted 95% CI] in LESP of -1.34 [-2.39, -0.29] mmHg. After adjusting for the main effect of sedative drug, LESP significantly declined with declining OAA/S (P=0.001); a unit decrease of OAA/S was associated with a decrease [Bonferroni-adjusted 95% CI] in LESP of -2.01 [-3.20, -0.81] mmHg. CONCLUSIONS: Deeper sedation, as measured by either BIS or OAA/S, significantly reduces LESP.

Airway scope for tracheal intubation in the lateral position.

BACKGROUND: Tracheal intubation in the lateral position is difficult because the laryngeal view is compromised during direct laryngoscopy. The Airway Scope facilitates intubation even when laryngeal views are poor with direct laryngoscopy, as they often are in the lateral position. We thus compared the efficacy of the Airway Scope in supine patients with those in the left- and right-lateral positions. METHODS: Anesthetized adults were randomly assigned to supine, left-lateral, or right-lateral position (n = 43 for each group). Laryngeal views were obtained in the designated position with a Macintosh laryngoscope, and patients' tracheas were subsequently intubated with the Airway Scope. Specifically, we tested the hypothesis that the time required for intubation in the left- and right-lateral positions is not increased by >10 seconds compared with tracheal intubation in the supine position. RESULTS: Overall intubation success was 100% in the 2 lateral positions, and 98% in the supine position. Intubation times were similar in the left-lateral (24 [5] seconds, mean [SD]), right-lateral (24 [6] seconds), and supine (22 [7] seconds) positions. The numbers of required intubation attempts were similar in the 2 lateral positions and in the supine and left-lateral positions. However, more intubation attempts were required in the supine position than in the right-lateral position (P = 0.004). The incidences of airway complications were similar in each position; no hypoxia, dental injury, or esophageal intubation was observed. Modified Cormack-Lehane and the percentage of glottic opening scores obtained with the Macintosh laryngoscope did not differ between the 2 lateral positions, but the modified Cormack-Lehane and percentage of glottic opening scores were superior in the supine position (all P < 0.001) compared with either of the lateral positions. CONCLUSIONS: Despite worse laryngoscopic views in either lateral position than when patients were supine, intubation with the Airway Scope offered high success rates. Furthermore, intubation time using the Airway Scope in either lateral position was not longer by >10 seconds than in the supine position. The Airway Scope thus seems to be a useful tool when tracheal intubation is required in a laterally positioned patient.

Learning curves for bag-and-mask ventilation and orotracheal intubation: an application of the cumulative sum method.

BACKGROUND: In this study, the authors determined the success and failure rates for interns learning bag-and-mask ventilation and orotracheal intubation. Their goal was to determine the amount of experience needed to perform these procedures correctly. METHODS: The authors recorded 695 bag-and-mask ventilations and 679 orotracheal intubations performed by 15 inexperienced interns during their 3 month-long anesthesia rotations. Learning curves for each procedure for each intern were constructed with both the standard and risk-adjusted cumulative sum methods. The average number of procedures required to attain a failure rate of 20% was estimated for each technique. RESULTS: Fourteen of 15 interns attained acceptable failure rates at bag-and-mask ventilation after 27 +/- 13 procedures, with a median (95% confidence interval) of 25 (15-32) procedures to cross the decision limit when considering all 15 interns. Nine of 15 interns attained acceptable failure rates at orotracheal intubation after 26 +/- 8 procedures, with a median of 29 (22-not estimable) procedures to cross the limit when considering all interns. The proportion of interns who attained acceptable failure rates for mask ventilation was greater than for tracheal intubation (93% vs. 60%, P = 0.025). Overall, our interns achieved a bag-and-mask ventilation failure rate of 20% or better after a median of 25 procedures; approximately 80% of interns achieved the goal after 35 procedures or less. CONCLUSIONS: Participating interns developed mask ventilation skills faster than orotracheal intubation skills, and there was more variability in the rate at which intubation skills developed. A median of 29 procedures was required to achieve an 80% orotracheal intubation success rate.

Effects of dexmedetomidine and propofol on lower esophageal sphincter and gastroesophageal pressure gradient in healthy volunteers.

BACKGROUND: Many anesthetics reduce lower esophageal sphincter pressure (LESP). Reduced pressure and consequent reduction in the gastroesophageal pressure gradient (GEPG) thus promotes gastroesophageal reflux and may contribute to aspiration pneumonia and associated morbidity. Therefore, the authors compared LESP and GEPG during dexmedetomidine and propofol sedation. METHODS: Using a randomized, double-blind, crossover design, 11 healthy volunteers were sedated on 2 separate days. Baseline LESP and GEPG were recorded each day. Subsequently, on each day volunteers received three 40-min-long sedative infusions of increasing doses of 0.6, 1.2, and 2.4 ng/ml dexmedetomidine or 1, 2, and 4 microg/ml propofol. LESP and GEPG were recorded during inhalation and expiration at 20 and 40 min after starting each infusion phase, and these measurements were averaged. Results are presented as mean (95% confidence interval). RESULTS: Two subjects did not return for the dexmedetomidine study day, and the dexmedetomidine results were unusable in another; propofol results in these volunteers were nonetheless retained for analysis. There were no significant differences in LESP and GEPG as a function of drug. However, there was a small but significant 7.4 (-1.6 to -13.2) mmHg (approximately 25%) dose-dependent decrease in LESP over the range of targeted low to high blood levels of each drug. CONCLUSIONS: Both dexmedetomidine and propofol have similar effects on LESP and GEPG. Although both of the drugs cause some decrease in LESP at high concentrations, it is unlikely that this effect would promote gastroesophageal reflux during sedation.

The effect of aminophylline on loss of consciousness, bispectral index, propofol requirement, and minimum alveolar concentration of desflurane in volunteers.

BACKGROUND: Adenosine is a soporific neuromodulator; aminophylline, which is clinically used as a bronchodilator, antagonizes the action of adenosine in the central nervous system. Thus, we tested the hypothesis that aminophylline delays loss of consciousness (LOC) and speeds recovery of consciousness (ROC) with propofol anesthesia, and that aminophylline increases the minimum alveolar concentration (MAC) of desflurane. METHODS: In this double-blind crossover study, volunteers were randomized to either aminophylline or saline on different days. Aminophylline 6 mg/kg was given IV, followed by 1.5 mg x kg(-1) x h(-1) throughout the study day. After 1 h of aminophylline or saline administration, propofol 200 mg was given at a rate of 20 mg/min. The bispectral index was continuously monitored, as were times to LOC and ROC. After recovery from propofol, general anesthesia was induced with sevoflurane and subsequently maintained with desflurane. The Dixon "up-and-down" method was used to determine MAC in each volunteer after repeated tetanic electrical stimulation. RESULTS: Eight volunteers completed both study days. Time to LOC was prolonged by aminophylline compared with saline (mean +/- SD) (7.7 +/- 2.03 min vs 5.1 +/- 0.75 s, respectively, P = 0.011). The total propofol dose at LOC was larger with aminophylline (2.2 +/- 0.9 vs 1.4 +/- 0.4 mg/kg, P = 0.01), and the time to ROC was shorter (6.18 +/- 3.96 vs 12.2 +/- 4.73 min, P = 0.035). The minimum bispectral index was greater with aminophylline (51 +/- 15 vs 38 +/- 9, P = 0.034). There was no difference in MAC. CONCLUSION: Aminophylline decreases the sedative effects of propofol but does not affect MAC of desflurane as determined by tetanic electrical stimulation.

Early postoperative subcutaneous tissue oxygen predicts surgical site infection.

BACKGROUND: Subcutaneous oxygen partial pressure is one of several determinants of surgical site infections (SSIs). However, tissue partial pressure is difficult to measure and requires invasive techniques. We tested the hypothesis that early postoperative tissue oxygen saturation (Sto(2)) measured with near-infrared spectroscopy predicts SSI. METHODS: We evaluated Sto(2) in 116 patients undergoing elective colon resection. Saturation was measured near the surgical incision, at the upper arm, and at the thenar muscle with an InSpectra™ tissue spectrometer model 650 (Hutchinson Technology Inc., Hutchinson, MN) 75 minutes after the end of surgery and on the first postoperative day. An investigator blinded to Sto(2) assessed patients daily for wound infection. Receiver operating characteristic curves were used to analyze the performance of Sto(2) measurements as a predictor of SSI. RESULTS: In 23 patients (≈ 20%), SSI was diagnosed 9 ± 5 days (mean ± SD) after surgery. Patients who did and did not develop an SSI had similar age (48 ± 14 vs 48 ± 15 years, respectively; P = 0.97) and gender (female:male, 15:8 vs 46:47, respectively), but patients who developed SSI weighed more (body mass index 32 ± 7 vs 27 ± 6 kg/m(2); P < 0.01). Sto(2) at the upper arm was lower in patients who developed SSI than in those who did not develop SSI (52 ± 22 vs 66 ± 21; P = 0.033), and these measurements had a sensitivity of 71% and specificity of 60% for predicting SSI, using Sto(2) of 66% as the cutoff point. CONCLUSION: Sto(2) measured at the upper arm only 75 minutes after colorectal surgery predicted development of postoperative SSI, although the infections were typically diagnosed more than a week later. Although further testing is required, Sto(2) measurements may be able to predict SSI and thus allow earlier preventive measures to be implemented.

Impeding factors of early rehabilitation postoperatively after rheumatoid toe arthroplasty: a single-center retrospective cohort study.

INTRODUCTION: Previous studies explored the benefits related to early ambulation postoperatively, but few focused on patients with rheumatoid arthritis (RA). We retrospectively evaluated the incidence and predictors of the inability to begin walking on the first postoperative day (POD) after toe arthroplasty for rheumatoid arthritis. METHODS: RA patients who underwent toe arthroplasty at one hospital were retrospectively reviewed. A total of 300 patients were included and divided into two groups: possible group (n = 191), who were able to walk on the first POD, and impossible group (n = 109), who were unable to walk on the first POD. Data were analyzed using odds ratios (OR) with 95% confidence intervals (CI) between various patient factors and the impossible group with logistic regression analysis. RESULTS: The incidence of postoperative nausea and vomiting before rehabilitation was significantly associated with the infeasibility of walking rehabilitation on the first POD [OR = 2.43, 95% CI 1.22-4.14, P = 0.003]. The number of rescue analgesics administered before rehabilitation and the supplementation of peripheral nerve block was also associated with the infeasibility of walking rehabilitation on the first POD [OR = 1.29, 95% CI 1.04-1.59, P = 0.003; OR = 0.41, 95% CI 0.20-0.79, P = 0.010, respectively]. CONCLUSION: The incidence of postoperative nausea and vomiting and inadequate postoperative pain management hindered early rehabilitation. Adding peripheral nerve block to general anesthesia had an advantage for postoperative rehabilitation after toe arthroplasty for rheumatoid arthritis.

Accuracy of postoperative end-tidal Pco2 measurements with mainstream and sidestream capnography in non-obese patients and in obese patients with and without obstructive sleep apnea.

BACKGROUND: Obtaining accurate end-tidal carbon dioxide pressure measurements via nasal cannula poses difficulties in postanesthesia patients who are mouth breathers, including those who are obese and those with obstructive sleep apnea (OSA); a nasal cannula with an oral guide may improve measurement accuracy in these patients. The authors evaluated the accuracy of a mainstream capnometer with an oral guide nasal cannula and a sidestream capnometer with a nasal cannula that did or did not incorporate an oral guide in spontaneously breathing non-obese patients and obese patients with and without OSA during recovery from general anesthesia. METHODS: The study enrolled 20 non-obese patients (body mass index less than 30 kg/m) without OSA, 20 obese patients (body mass index greater than 35 kg/m) without OSA, and 20 obese patients with OSA. End-tidal carbon dioxide pressure was measured by using three capnometer/cannula combinations (oxygen at 4 l/min): (1) a mainstream capnometer with oral guide nasal cannula, (2) a sidestream capnometer with a nasal cannula that included an oral guide, and (3) a sidestream capnometer with a standard nasal cannula. Arterial carbon dioxide partial pressure was determined simultaneously. The major outcome was the arterial-to-end-tidal partial pressure difference with each combination. RESULTS: In non-obese patients, arterial-to-end-tidal pressure difference was 3.0 +/- 2.6 (mean +/- SD) mmHg with the mainstream capnometer, 4.9 +/- 2.3 mmHg with the sidestream capnometer and oral guide cannula, and 7.1 +/- 3.5 mmHg with the sidestream capnometer and a standard cannula (P < 0.05). In obese non-OSA patients, it was 3.9 +/- 2.6 mmHg, 6.4 +/- 3.1 mmHg, and 8.1 +/- 5.0 mmHg, respectively (P < 0.05). In obese OSA patients, it was 4.0 +/- 3.1 mmHg, 6.3 +/- 3.2 mmHg, and 8.3 +/- 4.6 mmHg, respectively (P < 0.05). CONCLUSIONS: Mainstream capnometry performed best, and an oral guide improved the performance of sidestream capnometry. Accuracy in non-obese and obese patients, with and without OSA, was similar.

Suppression of shivering during hypothermia using a novel drug combination in healthy volunteers.

BACKGROUND: Hypothermia may be beneficial in stroke victims; however, it provokes vigorous shivering. Buspirone and dexmedetomidine each linearly reduce the shivering threshold with minimal sedation and no respiratory depression. This study tested the hypotheses that the combination of buspirone and dexmedetomidine would (1) synergistically reduce the shivering threshold, (2) synergistically reduce the gain and maximum intensity of shivering, and (3) produce sufficient inhibition to permit cooling to 34 degrees C without excessive hypotension or sedation. METHODS: Eight healthy men were randomly assigned on 4 days to (1) no drug, (2) buspirone (60 mg orally), (3) dexmedetomidine (intravenous infusion to target plasma concentration of 0.6 ng/ml), or (4) combination of buspirone and dexmedetomidine at same doses. Lactated Ringer's solution (approximately 3 degrees C) was infused intravenously to decrease tympanic membrane temperature by 1.5 degrees C/h. Shivering threshold was defined as an increase in oxygen consumption greater than 20%. Sedation was evaluated using the Observer's Assessment of Sedation/Alertness scale. RESULTS: Mean arterial pressure and heart rate were slightly lower on dexmedetomidine and combination days. Likewise, the level of sedation was statistically different on these 2 days but clinically unimportant. Buspirone reduced the shivering threshold from 36.6 degrees C +/- 0.4 degrees C to 35.9 degrees C +/- 0.4 degrees C, dexmedetomidine reduced it to 34.7 degrees C +/- 0.5 degrees C, and the combination to 34.1 +/- 0.4 degrees C. The interaction effect of 0.04 degrees C was not significant. The gain of shivering and maximum shivering intensity were similar on each day. CONCLUSIONS: The combination of buspirone and dexmedetomidine additively reduced the shivering threshold. Thus, supplementing dexmedetomidine with buspirone blocks shivering and causes only minimal sedation.

The correlation between bispectral index and observational sedation scale in volunteers sedated with dexmedetomidine and propofol.

BACKGROUND: Bispectral index (BIS) is a widely used quantitative parameter for evaluating anesthesia and sedation levels. Dexmedetomidine is a novel sedative, providing sedation while patients remain cooperative and can be easily aroused; as a consequence, BIS used with dexmedetomidine may poorly characterize sedation. Thus, we tested the hypothesis that BIS values are lower with dexmedetomidine than with propofol at comparable Observer's Assessment of Alertness and Sedation (OAA/S) scores. METHODS: This was a randomized, 2-day, crossover study. On the first study day, healthy volunteers were randomly allocated to either propofol or dexmedetomidine sedation. Drugs were administered using computer-controlled infusions targeting an effect-site concentration of 1, 2, and 4 microg/mL for propofol or a plasma concentration of 0.6, 1.2, and 2.4 ng/mL for dexmedetomidine. The relationship between BIS and OAA/S score was obtained 20 and 40 min after changing each drug concentration. BIS values at each OAA/S score were compared between drugs. The cutoff values of BIS for OAA/S score of < or =2 were obtained by analysis of receiver operating characteristic curves. RESULTS: Nine volunteers were included in our analysis. Heart rates decreased significantly with dexmedetomidine sedation. ETco(2) was significantly increased with high doses of propofol but did not increase with high doses of dexmedetomidine. BIS values at OAA/S scores of 1, 2, 3, 4, and 5 during propofol sedation were 95.5 (90-97), 78 (71-84.5), 67 (64-70), 57 (51.5-60), and 34 (30-37), respectively. BIS values at OAA/S scores of 1, 2, 3, 4, and 5 during dexmedetomidine sedation were 95 (79-98), 62 (53.5-68.5), 45.5 (45.3-52), 39.5 (34.3-41.8), and 24.5 (22.5-30.5), respectively. BIS values were significantly less with dexmedetomidine than propofol at OAA/S responsiveness scores of 2, 3, and 4. The calculated cutoff BIS values for OAA/S scores of < or =2 were 67 (sensitivity of 86%, specificity of 97%, and area under the curve of 0.98) for propofol and 46 (sensitivity of 84%, specificity of 91%, and area under the curve of 0.96) for dexmedetomidine. CONCLUSION: The combination of both BIS and sedative scales could provide different and complementary data to the clinician evaluating the patient's response to sedation than would either tool alone, especially when dexmedetomidine is used.

[Emergent operation for a patient of duodenal bleeding accompanied with fulminant myocarditis].

A 53-year-old woman developed general fatigue following an upper airway infection, which abruptly progressed to cardiogenic shock showing systolic blood pressure of 60 mmHg. An echocardiography revealed an ejection fraction of 0.11, diffuse severe hypokinesis and left ventricular thrombosis. Fulminant myocarditis was suspected, and intensive care including mechanical ventilation, intraaortic balloon pumping (IABP), catecholamine support and anticoagulation therapy was initiated immediately. Although the cardiac function gradually recovered, she developed a duodenal bleeding on the third therapeutic day. Factors such as low output syndrome, heparinization, steroid pulse therapy and platelet dysfunction due to IABP can enhance the hemorrhagic tendency. Since it was difficult to control bleeding by the endoscopy, blood transfusion was performed, and the operation was planned on the 13rd day when the cardiac function seemed to have recovered enough. The patient was anesthetized with ketamine, propofol and fentanyl. To maintain stable circulation, circulatory parameters such as blood pressure, central venous pressure, and cardiac output were monitored. After a preoperative consultation with the surgeon, the surgical technique had been preoperatively decided to reduce the surgical stress, and then partial duodenosectomy and gastro-jejunum anastomosis was performed. She was discharged on the 38th post operative day without complications. In cases of hemorrhagic disease accompanied by an acute phase of fulminant myocarditis, consultation among surgeons, cardiologists and anesthegiologists should be mandatory to determine the timing of the operation and to decide the degree of surgical invasion.