Characterizing the Heart Rate Effects From Administration of Sugammadex to Reverse Neuromuscular Blockade: An Observational Study in Patients.

BACKGROUND: Reversal of neuromuscular blockade (NMB) with sugammadex can cause marked bradycardia and asystole. Administration of sugammadex typically occurs in a dynamic period when anesthetic adjuvants and gas concentrations are being titrated to achieve emergence. This evaluation examined the heart rate (HR) responses to sugammadex to reverse moderate to deep NMB during a steady-state period and sought mechanisms for HR changes. METHODS: Patients with normal sinus rhythm, who were undergoing elective surgery that included rocuronium for NMB, were evaluated. After surgery, while at steady-state surgical depth anesthesia with sevoflurane and mechanical ventilation, patients received either placebo or 2 or 4 mg/kg of sugammadex to reverse moderate to deep NMB. Study personnel involved in data analysis were blinded to treatment. Continuous electrocardiogram (ECG) was recorded from the 5 minutes before and 5 minutes after sugammadex/placebo administration. R-R intervals were converted to HR and averaged in 1-minute increments. The maximum prolongation of an R-R interval after sugammadex was converted to an instantaneous HR. RESULTS: A total of 63 patients were evaluated: 8 received placebo, and 38 and 17 received 2 and 4 mg/kg sugammadex. Age, body mass index, and patient factors were similar in groups. Placebo did not elicit HR changes, whereas sugammadex caused maximum instantaneous HR slowing (calculated from the longest R-R interval), ranging from 2 to 19 beats/min. There were 7 patients with maximum HR slowing >10 beats/min. The average HR change and 95% confidence interval (CI) during the 5 minutes after 2 mg/kg sugammadex were 3.1 (CI, 2.3-4.1) beats/min, and this was not different from the 4 mg/kg sugammadex group (4.1 beats/min [CI, 2.5-5.6]). HR variability derived from the standard deviation of consecutive R-R intervals increased after sugammadex. CONCLUSIONS: Sugammadex to reverse moderate and deep NMB resulted in a fast onset and variable magnitude of HR slowing in patients. A difference in HR slowing as a function of dose did not achieve statistical significance. The observational nature of the investigation prevented a full understanding of the mechanism(s) of the HR slowing.

Titration of sevoflurane anesthesia to optimize the time to regain airway reflexes in patients undergoing elective surgery: A randomized clinical trial comparing desflurane and sevoflurane anesthesia.

BACKGROUND: Desflurane has adverse environmental effects, but has clinical advantages to speed emergence and return of protective airway reflexes compared with sevoflurane. We hypothesized that weaning of the inspired sevoflurane during the final 15 minutes of surgery would eliminate differences in airway reflex recovery between these agents. METHODS: After obtaining IRB approval and informed consent, 40 patients undergoing elective surgery (≥1-hour) randomly received desflurane or sevoflurane. Patients swallowed 20 mL of water without drooling or coughing, and then received sedation and PONV pre-medication. Anesthesia was induced using propofol and fentanyl and maintained with desflurane or sevoflurane through a laryngeal mask airway maintaining a bispectral index of 45-50 and 50-60 during the final 15 minutes before surgery end. Cardiorespiratory variables and age-adjusted minimal alveolar concentration were recorded. The duration between anesthetic discontinuation and first appropriate response to command was measured; the laryngeal mask airway was removed. Two minutes after responding to command, patients were positioned semi-upright and attempted to swallow water. If successful swallowing was not achieved, the test was repeated every 4 minutes after each failure until successful swallowing was achieved. RESULTS: Average anesthetic concentration and bispectral index was similar in patients receiving desflurane vs sevoflurane. Response times after discontinuation of anesthetics were similar. There were no differences in the recovery of swallowing ability between desflurane and sevoflurane groups. CONCLUSION: Weaning of sevoflurane during the final 15 minutes of surgery eliminates clinical advantages of the more rapid return of airway reflexes with desflurane.

Predisposing and Precipitating Factors Associated With Postoperative Delirium in Patients Undergoing Cardiac Surgery at a Veterans Affairs Medical Center: A Pilot Retrospective Analysis.

OBJECTIVE: Patients treated at Veterans Affairs (VA) medical centers are in poorer health, experience more medical and psychiatric conditions, and make greater use of medical resources than do patients in the general population. In the present pilot study, the authors examined their recent experience at a VA medical center to determine the incidence and risk factors associated with the development of postoperative delirium in VA patients after cardiac surgery and hypothesized that the risk factors for postoperative delirium after cardiac surgery are different between VA and non-VA patients. DESIGN: Retrospective cohort study. SETTING: Clement J. Zablocki Veterans Affairs Medical Center. PARTICIPANTS: The study comprised 250 consecutive patients undergoing cardiac surgery from July 2014 to March 2016. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Demographics, coexisting diseases, and medications were obtained from the VA electronic medical record. The European System for Cardiac Operative Evaluation II mortality risk index was calculated for each patient. The type and duration of the procedure and the duration of bypass were recorded. Intraoperative crystalloid, colloid, cell saver, and blood product volumes were compiled. Progress notes and International Classification of Diseases, Tenth Revision, Clinical Modification codes were searched for documentation of postoperative delirium. Thirty-eight patients (15.2%) developed postoperative delirium. Stepwise logistic regression analysis demonstrated that the European System for Cardiac Operative Evaluation II mortality risk index (odds ratio [OR] 1.036, 95% confidence interval [CI] [1.003-1.070]; p = 0.0344), congestive heart failure (OR 2.223 [95% CI 1.046-4.722]; p = 0.0377), pre-existing cognitive impairment (OR 5.147 [95% CI 1.994-13.28]; p = 0.0007), and the presence of a neuropsychiatric disorder (OR 2.015 [95% CI 1.004-4.043]; p = 0.0487) were predisposing factors associated with higher odds of postoperative delirium. The duration of surgery; transfusion of blood products (including packed red blood cells, fresh frozen plasma, and platelets); the durations of mechanical ventilation and conscious sedation (using either propofol or dexmedetomidine); and the length of intensive care unit stay were precipitating factors associated with higher odds of postoperative delirium. CONCLUSIONS: The results demonstrate that congestive heart failure, pre-existing cognitive impairment, and the presence of a neuropsychiatric disorder are predisposing risk factors for postoperative delirium after cardiac surgery in VA patients, whereas the duration of surgery, transfusion of blood products, durations of mechanical ventilation and conscious sedation, and length of intensive care unit stay are precipitating factors for postoperative delirium. These findings in VA patients generally are similar to those observed in the civilian population despite the differences between these cohorts.

Moderate, Short-Term, Local Hyperglycemia Attenuates Forearm Endothelium-Dependent Vasodilation After Transient Ischemia-Reperfusion in Human Volunteers.

OBJECTIVE: Acute hyperglycemia causes endothelial dysfunction in diabetic patients, abolishes ischemic pre- and postconditioning, and is an independent predictor of adverse outcome after myocardial infarction in nondiabetic patients. Its effects on endothelial-dependent vasodilation are controversial in healthy subjects. The authors studied the effect of moderate short-term local hyperglycemia on forearm endothelium-dependent vasodilation in healthy volunteers. DESIGN: Randomized, crossover, blinded, 2-visit, pilot design. SETTING: Veterans Affairs Medical Center. PARTICIPANTS: Five male and 3 female healthy adult volunteers (23±4 years; height 171±13 cm; weight 66±9 kg; [mean±standard error of the mean]). INTERVENTIONS: At each visit, volunteers received an infusion through a brachial artery catheter of either 0.9% saline or dextrose in the experimental, non-dominant arm, to establish mild forearm hyperglycemia. Hemodynamics and forearm blood flow (FBF; plethysmography) were measured at baseline, during brachial artery infusions of acetylcholine in consecutive increments (5, 10, and 15 µg/min), before ischemia (20 min, blood pressure cuff at 200 mmHg), and after 15 minutes of reperfusion. Blood glucose and insulin concentrations were determined from venous samples. The effect of duration of intra-arterial dextrose on FBF was examined. MEASUREMENTS AND MAIN RESULTS: Dextrose increased steady-state blood glucose concentration in the experimental but not the control arm (dominant arm). Dextrose increased FBF compared with saline (4.5±0.5 v 2.6±0.4 mL/min/100 g of tissue, respectively). Acetylcholine caused similar increases in FBF in the absence and presence of dextrose (+239±90% v+203±75%, respectively, during 15 µg/min). The duration of dextrose did not affect this acetylcholine-induced vasodilation. Acetylcholine-stimulated increases in FBF were attenuated in dextrose-treated versus saline after reperfusion (+180±18% v+257±53%, respectively, during 10 µg/min). Interventions in the experimental arm did not affect FBF in the control arm. CONCLUSION: These results indicated that moderate, short-term, local hyperglycemia induced by intra-arterial administration of dextrose attenuated forearm endothelial-dependent vasodilation after ischemia-reperfusion injury in healthy volunteers.

Ventilation monitoring during moderate sedation in GI patients.

Sedation in locations outside the operating room (OR) is common. Guidelines for safe patient monitoring have been updated by the American Society of Anesthesiology to include monitoring of ventilation and/or carbon dioxide (CO2). Although technologies exist to monitor these variables, the quality and/or availability of these measurements in non-OR settings is not optimal. This quality improvement project assessed the value of impedance technology for monitoring minute ventilation (MV) compared to standard end-tidal monitoring of CO2 (ETCO2). Patients undergoing GI exams with moderate sedation provided by anesthesia providers were monitored for MV with a respiratory volume monitor (ExSpiron 1Xi, Respiratory Motion, Waltham, MA) and ETCO2 via nasal cannula (NC). Calibration and baseline data were collected prior to sedation. Continuous MV and ETCO2 data were collected and averaged, providing minute values after sedation medications throughout the procedure. Stable periods of reduced MV were averaged and used in comparison to ETCO2. Data from 20 patients were evaluated. After sedation, the expected decrease in MV after sedation was observed in 18 of 20 patients (average -47.82 %), while an increase in ETCO2 was observed in just 10 of 20 patients (average -5.17 mm Hg). The correlation coefficient between changes in MV and ETCO2 in response to sedation administration was positive and not significant, r = 0.223. Ventilation monitoring may provide an element of safety for earlier and more reliable detection of reduced ventilation compared to a surrogate for hypoventilation, ETCO2, in patients undergoing sedation for GI procedures outside of the OR.

Short-Term Angiotensin Subtype 1 Receptor Blockade Does Not Alter the Circulatory Responses to Sympathetic Nervous System Modulation in Healthy Volunteers Before and During Sevoflurane Anesthesia: Results of a Pilot Study.

OBJECTIVE: The mechanism of perioperative hypotension in patients taking an angiotensin-receptor blocker up to the time of surgery remains unclear. This study tested the hypothesis that short-term angiotensin-receptor blocker treatment attenuated the sympathetic and vascular responses to autonomic stimuli in volunteers undergoing anesthesia. DESIGN: Randomized, crossover, blinded, pilot design. SETTING: Zablocki Veterans Affairs Medical Center, Milwaukee, WI. PARTICIPANTS: The study comprised 8 male and 6 female healthy, young volunteers (age 23±1.2 years [mean±standard error of the mean]). INTERVENTIONS: Volunteers were studied after receiving oral placebo or 50 mg of losartan (angiotensin-receptor blocker) for 3 days before each test day. The effectiveness of angiotensin-receptor blocker treatment was confirmed using the mean arterial blood pressure response to intravenous angiotensin II (1-µg bolus). Eight volunteers underwent direct mean arterial pressure and forearm bloodflow measurements during conscious baseline, a cold pressor test, induction of anesthesia, tracheal intubation, maintenance of anesthesia with 1 minimum alveolar concentration of sevoflurane, and airway irritation with 12% desflurane. Six volunteers experienced mean arterial pressure responses to 0.1 mg of phenylephrine at baseline and during 1 minimum alveolar concentration of sevoflurane. MEASUREMENTS AND MAIN RESULTS: Comparisons were made over time and across groups. Angiotensin-receptor blocker treatment significantly reduced-mean arterial pressure and forearm vascular resistance (forearm blood flow/mean arterial pressure) over time and blocked the mean arterial pressure response to angiotensin-II challenge. The changes in mean arterial pressure and forearm vascular resistance in response to all stressors did not differ between treatments. Mean arterial pressure increases from phenylephrine were preserved. CONCLUSIONS: In healthy, young volunteers, sympathetically-mediated responses from the short-term use of an angiotensin-receptor blocker were not altered and most likely did not contribute to perioperative hypotension during the intraoperative period.

The effectiveness of oxygen delivery and reliability of carbon dioxide waveforms: a crossover comparison of 4 nasal cannulae.

BACKGROUND: Effective O2 delivery and accurate end-tidal CO2 (ETCO2) sampling are essential features of nasal cannulae (NCs) in patients with compromised respiratory status. We studied 4 NC designs: bifurcated nasal prongs (NPs) with O2 delivery and CO2 sensing in both NPs (Hudson), separate O2/CO2 NPs (Salter), and CO2 sensing in NPs with cloud O2 delivery outside the NPs via multi vents (Oridion) and dual vents (Medline). We hypothesized that design differences between NCs would influence O2 delivery and ETCO2 detection. METHODS: Forty-five healthy volunteers, 18 to 35 years, participated in an unrestricted, randomized block design, each subject serving as their own control in a 4-period crossover study design of 4 NCs during one session. Monitoring included electrocardiogram, posterior pharynx O2 sampling from a Hauge Airway (Sharn Anesthesia Products, Tampa, FL), and NC ETCO2. In 11 volunteers, radial artery blood was sampled from a catheter for partial pressures of O2 and carbon dioxide (PaO2 and PaCO2) determination. Per randomization, each NC was positioned, and data were collected over 2 minutes (ETCO2, pharyngeal O2, PaO2, and PaCO2) during room air and during O2 fresh gas flows (FGFs) of 2, 4, and 6 Lpm. Statistical analyses were performed with SAS Analytics Pro, Version 9.3, and JMP Statistical Software, Version 11 (SAS Institute Inc., Cary, NC), significance at P < 0.05. RESULTS: Blood gas analyses indicated PaCO2 during steady state at each experimental time period remained unchanged from physiologic baseline. PaO2 did not differ between NC devices at baseline or 2 Lpm O2. The PaO2 at 4 Lpm from the separate NPs and bifurcated NCs was significantly higher than the multi-vented NC. Pharyngeal O2 with the NC with separate NPs was significantly higher than multivented and dual-vented cloud delivery NCs at 2, 4, and 6 Lpm FGF. Pharyngeal O2 with the NC with bifurcated NPs was significantly higher than the multi-vented NC at 2 Lpm, and higher than cloud delivery NCs at 4 and 6 Lpm FGF. ETCO2 was significantly lower with the NC with bifurcated NPs compared to the other 3 NCs, consistent with errant CO2 tracings at higher FGF. CONCLUSIONS: NCs provide supplemental inspired O2 concentrations for patients with impaired pulmonary function. Accurate measures of ETCO2 are helpful in assessing respiratory rate and determining whether CO2 retention is occurring from hypoventilation. These findings suggest the NC with separate NPs was the most effective in delivering O2 and the most consistent at providing reliable CO2 waveforms at higher FGFs.

Competency-based education in anesthesiology: history and challenges.

The Accreditation Council for Graduate Medical Education is transitioning to a competency-based system with milestones to measure progress and define success of residents. The confines of the time-based residency will be relaxed. Curriculum must be redesigned and assessments will need to be precise and in-depth. Core anesthesiology faculty will be identified and will be the "trained observers" of the residents' progress. There will be logistic challenges requiring creative management by program directors. There may be residents who achieve "expert" status earlier than the required 36 months of clinical anesthesia education, whereas others may struggle to achieve acceptable status and will require additional education time. Faculty must accept both extremes without judgment. Innovative new educational opportunities will need to be created for fast learners. Finally, it will be important that residents embrace this change. This will require programs to clearly define the specific aims and measurement endpoints for advancement and success.

How an Audit-and-Feedback-Based Educational Program Contributed to a Reduction in Environmentally Harmful Waste Anesthetic Gases Among Anesthesiology Residents.

Background Waste anesthetic gases (WAGs) contribute to greenhouse gas emissions. US anesthesiology resident education on how to reduce WAG-associated emissions is lacking, so we developed an electronic audit-and-feedback-based program to teach residents to reduce fresh gas flow (FGF) and WAG-associated emissions. Objective To assess the program's effectiveness, we measured individual and combined mean FGF of residents during their first, second, and last weeks of the 4-week rotation; then, we calculated the extrapolated annual emissions based on the combined resident mean FGFs. Resident attitudes toward the program were surveyed. Methods During 4-week rotations at a teaching hospital, anesthesia records were scanned to extract resident-assigned cases, FGF, and volatile anesthetic choice during the 2020-2021 academic year. Forty residents across 3 training years received weekly FGF data and extrapolated WAG-associated emissions data via email. Their own FGF data was compared to the low-flow standard FGF of ≤1 liter per minute (LPM) and to the FGF data of their peer residents on rotation with them. An online survey was sent to residents at the end of the project period. Results Between their first and last weeks on rotation, residents decreased their mean FGF by 22% (1.83 vs 1.42 LPM; STD 0.58 vs 0.44; 95% CI 1.67-2.02 vs 1.29-1.56; P<.0001). Ten of 18 (56%) residents who responded to the survey reported their individual case-based results were most motivating toward practice change. Conclusions An audit-and-feedback-based model for anesthesiology resident education, designed to promote climate-conscious practices with administration of volatile anesthetics, was effective.

A Case Report of Acute Onset and Rapid Resolution of Atrioventricular Block After Sugammadex: Is the Autonomic System Involved?

Administering sugammadex to reverse neuromuscular blockade can cause marked bradycardia and rarely asystole. In this case, a rapid onset, biphasic heart rate response; slowing then speeding, after administering sugammadex was noted while at steady state, 1.3% end-tidal sevoflurane. On review of the electrocardiogram (ECG), the heart rate slowing coincided with the onset of a second-degree, Mobitz type I block that lasted 45 seconds. No other events, drugs, or stimuli coincided with the event. The acute onset and transient nature of the atrioventricular block without evidence of ischemia implies a brief parasympathetic effect on the atrioventricular node after sugammadex administration.

New Opioid Persistence in Veterans Following Major and Minor Surgery.

INTRODUCTION: Opioids are often a mainstay of managing postsurgical pain. Persistent use of opioids for more than 90 days after surgery is problematic, and the incidence of this adverse outcome has been reported in the civilian population ranging from 0.4% to 7%. Veterans compose a special population exposed to trauma and stressful situations and consequently face increased risk for habit-forming behavior and drug overdose. This evaluation determined the prevalence of opioid persistence after surgery and its relationship to patient characteristics in a military veteran population. METHODS: A retrospective chart review was completed on 1,257 veterans who were opioid naive and had undergone a surgical procedure between January 2017 and May 2018. Patient characteristics, health conditions, and discharge opioid medications were recorded, and the incidence of persistent opioid use beyond 90 days was determined. RESULTS: The incidence of opioid persistence following major (3.3%) and minor (3.4%) procedures was similar. The incidence in patients younger than 45 years (3.3%), between 45 and 64 years (4.3%), and 65 years and older (2.2%) was also determined to be similar. Univariate patient factors associated with an increased risk for persistent opioid use include cancer (odds ratio [OR], 2.13; 95% CI, 1.11-4.09), mental health disorders (OR, 2.32; 95% CI, 1.17-4.60), and substance use disorders (OR, 2.09; 95% CI, 1.09-4.00). CONCLUSIONS: Among a cohort of over 1,200 opioid-naïve veterans undergoing surgery at a VA Medical Center, just over 3% went on to develop persistent opioid use beyond 3 months following their procedure. Persistent use was not found to be related to the type of procedure (major or minor) or patient age. Significant patient-level risk factors for opioid persistence were cancer and a history of mental health and substance use disorders.

Clinical Features of COVID-19 Infection in Patients Treated at a Large Veterans Affairs Medical Center.

INTRODUCTION: During recent months, reports describing the characteristics of COVID-19 patients in China, Italy, and the United States have been published. Military veterans represent another unique population affected by COVID-19. This report summarizes the demographics and baseline clinical comorbidities in veterans testing positive for COVID-19 in Milwaukee, Wisconsin. METHODS: Patient evaluations were conducted at the Zablocki VA Medical Center, Milwaukee, Wisconsin between March 11, 2020 and June 1, 2020. Patient demographics, baseline comorbidities, home medications, presenting symptoms, and outcomes were obtained via electronic medical record. RESULTS: Ninety-five patients (88 men, 7 women) tested positive for COVID-19 and were evaluated. Fourteen required mechanical ventilation; 50 and 31 patients were treated in the hospital without ventilation or were discharged to home isolation, respectively. Discharged patients were younger than patients hospitalized. Most patients with COVID-19 were African American (63.2%). Patients whose disease progressed to mechanical ventilation had, on admission, more dyspnea, higher heart and respiratory rates, and lower oxygen saturation than other patients. COVID-19 patients who required mechanical ventilation had a longer length of stay and higher mortality than other groups and were more likely to have a history of hypertension and hyperlipidemia than patients who were discharged to home quarantine (85.7% and 78.6% vs 48.4% and 45.2%, respectively; P < 0.05 for each). CONCLUSION: COVID-19-positive veterans are predominantly African American men with hypertension and hyperlipidemia receiving beta blockers or ACEi/ARB. COVID-19-positive veterans who presented with dyspnea, tachypnea, tachycardia, and hypoxemia were more likely to require endotracheal intubation and mechanical ventilation, had longer hospital length-of-stay, and experienced greater mortality than comparison groups.

The effect of obesity on neuraxial technique difficulty in pregnant patients: a prospective, observational study.

BACKGROUND: Practitioners often presuppose that obesity will increase neuraxial technique difficulty in pregnant patients, but few investigators have systematically examined this population for risk factors associated with difficult epidural or spinal needle placement. We designed this study to prospectively identify factors that predict neuraxial technique difficulty in pregnant patients. METHODS: Using a prospective, observational format, pregnant patients were examined for multiple potential risk factors for neuraxial technique difficulty, including current body mass index, ability to palpate spinous processes, maximum back flexion, scoliosis, and experience of the practitioner. Neuraxial technique difficulty was then assessed using two measures: 1) the number of needle passes needed to reach the desired space, and 2) the placement time from skin infiltration to either spinal injection or epidural catheter threading. Predictors of total needle passes were determined by fitting the data to a generalized linear model with negative binomial error. Predictors of neuraxial anesthetic time were determined by fitting a linear model to the log of neuraxial anesthetic placement time. A survival model was used to account for bias introduced when attending physicians intervened in resident physician procedures. RESULTS: Neuraxial procedures in 427 pregnant patients were studied. For both the number of needle passes and the neuraxial anesthetic placement time, the significant predictors of difficulty were the practitioner's ability to palpate the patient's bony landmarks and the patient's ability to flex her back. Obesity, as measured by body mass index, was not an independent predictor of either end point. Obesity did, however, strongly predict both the ability to palpate landmarks and flex the back. CONCLUSIONS: Despite concerns that obesity may cause difficulty with neuraxial technique, some obese patients have surprisingly easy neuraxial block placements. When approaching any neuraxial anesthetic in a pregnant patient, and especially in the obese parturient, back flexion and landmark palpation predict neuraxial technique difficulty.

Anesthesia Preoperative Clinic Evaluation of Obstructive Sleep Apnea Using Nasal Fiberoptic Videoendoscopy: A Pilot Study Comparison with Polysomnography.

BACKGROUND: Nasal fiberoptic videoendoscopy is an established technique to assess upper airway pathology in conscious and sedated patients. OBJECTIVES: The authors conducted a prospective proof-of-concept pilot study to evaluate whether airway narrowing detected using nasal fiberoptic videoendoscopy in the anesthesia preoperative clinic was capable of defining the severity of obstructive sleep apnea (OSA) in patients scheduled for elective surgery. METHODS: After application of topical local anesthesia (4% lidocaine with phenylephrine), sixteen patients (ASA physical status 2 or 3) underwent nasal fiberoptic videoendoscopy in sitting position. The magnitudes of retropalatal and retrolingual luminal narrowing were assessed as predictors of OSA. Patients also underwent polysomnography and completed STOP-Bang questionnaires. The endoscopist's clinical impression of OSA severity based on the history and airway examination was quantified. RESULTS: Retropalatal luminal narrowing and STOP-Bang score ≥ 4 predicted OSA severity as either "none or mild" or "moderate to severe" in 13 (81%) and 9 (56%) of 16 patients who underwent polysomnography, respectively. OSA severity was significantly (Spearman's rank correlation coefficient) associated with retropalatal airway narrowing (P = 0.0048), STOP-BANG score (P = 0.0072), and body mass index (P = 0.0091), whereas clinical impression and retrolingual pharyngeal narrowing were not (P=0.093 and P = 0.11, respectively). CONCLUSIONS: The current results suggest that nasal fiberoptic videoendoscopy quantification of retropalatal airway narrowing may be a useful tool for assessing the severity of OSA in the anesthesia preoperative clinic. The current findings document a proof-of-concept feasibility of nasal fiberoptic videoendoscopy as a screening tool for OSA in conscious patients during preoperative evaluation that may justify further prospective clinical trials of this technique.

Choice of volatile anesthetic for the morbidly obese patient: sevoflurane or desflurane.

STUDY OBJECTIVE: Morbid obesity is associated with significant comorbidities. Desflurane has a low fat-blood solubility coefficient and may be better suited in this population to achieve a rapid emergence; however, sevoflurane has favorable cardiorespiratory properties that might also prove advantageous in the morbidly obese (MO) patient. This study used careful drug titration to determine if emergence differences between sevoflurane and desflurane could be minimized in MO patients. DESIGN: A randomized, prospective blinded study to determine the emergence profiles of desflurane and sevoflurane in MO patients when anesthetic drug titration is used. SETTING: Operating room of the VA Medical Center, Milwaukee, Wis. PATIENTS: Forty American Society of Anesthesiologists II and III, MO patients (body mass index > or = 35 kg/m2), who were scheduled for elective surgery predicted to last for more than 2 hours, were studied. INTERVENTIONS: Patients were induced with fentanyl, midazolam, and propofol and maintained with desflurane or sevoflurane, mixed in air and oxygen. Intraoperative bispectral index (BIS) was targeted to 45 to 50 and to 60 in the last 15 minutes of surgery. MEASUREMENTS: Intraoperative anesthetic concentration, BIS, and hemodynamics were recorded. During emergence, time to follow command and extubation were noted, with assessments of cognitive function via the Mini-Mental Status Test and psychomotor performance via the Digit Symbol Substitution Test. A blinded observer recorded key recovery events. MAIN RESULTS: Demographic data (age, 61 [36-83] years; body mass index, 38 [35-47] kg/m2), surgical procedures, length of anesthesia (approximately 3.5 hours), adjuvant drugs, and intraoperative BIS, heart rate, and mean arterial pressure were not significantly different. Hemodynamics, time to follow commands and to extubation, and results of Digit Symbol Substitution Test and Mini-Mental Status Test did not differ between anesthetic groups during recovery. CONCLUSIONS: There were no differences in emergence and recovery profiles in MO patients receiving desflurane or sevoflurane when anesthetic concentration was carefully titrated.

The effects of thiopental and generic and nongeneric propofol on respiratory resistance during anesthetic induction in patients with reactive airways.

STUDY OBJECTIVE: To demonstrate a favorable effect of propofol on respiratory system resistance during anesthetic induction, and to determine if generic propofol causes adverse effects on respiratory resistance. DESIGN: Randomized pilot study. SETTING: Anesthetic induction for elective surgery. PATIENTS: 27 consenting ASA physical status II and III patients with reactive airways (positive smoking history or chronic obstructive pulmonary disease), but not receiving bronchodilator therapy. INTERVENTIONS: Patients were randomized equally to one of three anesthetic induction (and maintenance) drugs: sodium thiopental, 5 mg/kg (25 microg/kg/min), generic or nongeneric propofol, 1.25 mg/kg (50 microg/kg/min). They received preinduction midazolam and fentanyl (2 mg and 150 microg) and intravenous lidocaine (0.5 mg/kg). After anesthetic induction, tracheal intubation was established, and predetermined settings for mechanical ventilation were initiated. MEASUREMENTS: Immediately after intubation, a sensor was placed on the 8-mm endotracheal tube to detect baseline airway pressure and flow. During maintenance, repeat measurements of pressure and flow were obtained at 2.5-minute intervals for 10 minutes. Respiratory system resistance was derived off-line using the isovolumetric technique. MAIN RESULTS: Patients were similar across groups. The respiratory resistance measured after anesthetic induction did not differ among groups. During the maintenance infusion of thiopental or propofol, respiratory resistance increased gradually across all groups. There was no difference in the response of respiratory resistance either at induction or during the 10-minute maintenance between the generic and the nongeneric propofol groups. CONCLUSIONS: In contrast to earlier reports, this pilot study was unable to document a difference in the respiratory resistance in patients induced with thiopental or propofol. In addition, we were unable to demonstrate any different respiratory responses between generic propofol, containing sodium metabisulfite preservative, and nongeneric propofol.

Hemodynamic responses to angiotensin-(1-7) in women in their third trimester of pregnancy.

BACKGROUND: To understand the role of Angiotensin-(1-7) (Ang-(1-7)) in vasculature of pregnant women, we compared cardiac output (CO), total peripheral resistance (TPR) and forearm blood flow (FBF) responses to Ang-(1-7) infusion between normotensive pregnant women in their third trimester and healthy age matched non-pregnant women. The responses of skin microcirculation to Ang-(1-7) were tested in preeclamptic, normotensive pregnant and non-pregnant women. Responses to Angiotensin II (Ang II) were also determined. METHODS: Non-invasive methods for systemic (bioimpedance and VascuMAP), FBF (venous occlusion strain gauge plethysmography), and skin (laser Doppler) hemodynamics assessments were used. RESULTS: Compared to non-pregnant women, systemic infusion of Ang-(1-7) (2000 pmol/min) resulted in a greater increase in CO (9.4 ± 6.4 versus -3.3 ± 2.1%, n = 9-10) in normotensive pregnant women. Brachial local infusion of Ang-(1-7) had no effect on FBF in either group. In non-pregnant and normotensive pregnant women, local Ang II induced a dose-dependent decrease in FBF and increase in forearm resistance at 50 and 100 pmol/min (p < 0.05 versus corresponding baseline, n = 7-10). Following iontophoretic application of 5 mmol/l dose of Ang-(1-7), the change in skin flow was higher in normotensive pregnant versus preeclamptic women (182.5 ± 93 versus 15.76 ± 19.46%, n = 14-15). Skin flow was lower in normotensive pregnant versus preeclamptic women (-46.5 ± 48.7 versus 108.7 ± 49.1%, n = 14-15) following Ang II infusion at 1.0 pmol/min. CONCLUSION: In the third trimester of pregnancy, Ang-(1-7) induces alterations in CO and differentially regulates micro- and macro-circulations, depending on the dose. Dysregulation in skin vasculature may contribute to the development of vascular dysfunction and hypertension in preeclampsia.

Perioperative considerations for patients with morbid obesity.

The anesthetic management of the MO patient requires an important focus on a number of issues beginning with a careful preoperative evaluation and synthesizing pre-existing disease processes with the anesthetic management plan. The common misperception that all MO patients are "full stomach" has been challenged and may be a nonissue. New approaches to pre-oxygenation to lessen the likelihood of desaturation during apnea may be a valuable tool if difficulty is encountered in tracheal intubation. In addition, promising results have been demonstrated with the use of the ILMA for ventilation and for blindly establishing tracheal tube placement. Proper patient positioning is essential to aid in successful intubation when a laryngoscope is employed. Intraoperative anesthetic management can be guided with a processed electroencephalogram monitor to help improve emergence and to enhance wakefulness in the PACU. Careful consideration must be given to postoperative analgesic needs by minimizing the use of opioids and employing nonopioid analgesics including NSAIDs, alpha2-adrenergic agonists, and low doses of ketamine.

Sympathetic and hemodynamic effects of moderate and deep sedation with propofol in humans.

BACKGROUND: The objective of this study was to determine the mechanisms involved in the hypotension associated with sedative doses of propofol in humans. METHODS: Ten healthy volunteers (aged 21-37 yr) participated on two occasions and in random order received placebo or propofol infusions. Standard monitoring and radial artery blood pressure were combined with measurement of forearm blood flow (plethysmography) and derivation of forearm vascular resistance, recording of peroneal nerve sympathetic activity, and blood sampling for norepinephrine concentrations. A computer-controlled infusion pump delivered placebo or two concentrations of propofol, adjusted to achieve moderate and deep sedation based on the Observer Assessment of Alertness/Sedation score (responsiveness component) of 4 and 3. Level of sedation was quantitated using bispectral analysis of the electroencephalogram. Baroreflexes were assessed with a hypotensive challenge via administration of sodium nitroprusside. RESULTS: Baseline neurocirculatory and respiratory parameters did not differ between sessions. Progressive infusions to achieve moderate and deep sedation resulted in average Bispectral Index values of 70 and 54, respectively. Propofol significantly reduced sympathetic nerve activity at both levels of sedation and decreased norepinephrine and forearm vascular resistance at deep sedation. These effects resulted in significant decreases in mean blood pressure of 9% and 18% at moderate and deep sedation, respectively. Propofol also reduced reflex increases in sympathetic nerve activity. CONCLUSIONS: These data from healthy subjects indicate that sedation doses of propofol, which did not compromise respiratory function, had substantial inhibitory effects on sympathetic nerve activity and reflex responses to hypotension resulting in vasodilation and significant decreases in mean blood pressure.

Desflurane enhances reactivity during the use of the laryngeal mask airway.

BACKGROUND: Desflurane and sevoflurane have markedly different pungencies. The tested hypothesis was that patients breathing equivalent concentrations of desflurane or sevoflurane through a laryngeal mask airway (LMA) would have similar responses. METHODS: After institutional review board approval and informed consent were obtained, 60 patients were enrolled and given intravenous midazolam (14 microg/kg) and fentanyl (1 microg/kg) 5 min before induction of anesthesia. The LMA was inserted at loss of consciousness after 2 mg/kg propofol. When spontaneous breathing returned, a randomly assigned volatile anesthetic was started at an inspired concentration of either 1.8% sevoflurane or 6% desflurane at a fresh gas flow of 6 l/min in air:oxygen (50:50). After 5 min, a controlled movement of the LMA took place. Three minutes later, the inspiratory anesthetic concentration was changed to either 3.6% sevoflurane or 12% desflurane for 3 min. A blinded observer recorded movements and airway events during the start of anesthetic, LMA movement, deepening of the anesthetic, and emergence before LMA removal. RESULTS: There were no differences at anesthetic start and LMA movement. Desflurane titration to 12% increased heart rate, increased mean arterial blood pressure, and initiated frequent coughing (53% vs. 0% sevoflurane) and body movements (47% vs. 0% sevoflurane). During emergence, there was a twofold greater incidence of coughing and a fivefold increase in breath holding in the desflurane group. CONCLUSIONS: When airway responses to sevoflurane and desflurane were compared in elective surgical patients breathing through an LMA, there were significantly more adverse responses with desflurane at 12% concentrations and during emergence.