Effects of obesity, pneumoperitoneum, and body position on mechanical power of intraoperative ventilation: an observational study.

Mechanical power can describe the complex interaction between the respiratory system and the ventilator and may predict lung injury or pulmonary complications, but the power associated with injury of healthy human lungs is unknown. Body habitus and surgical conditions may alter mechanical power but the effects have not been measured. In a secondary analysis of an observational study of obesity and lung mechanics during robotic laparoscopic surgery, we comprehensively quantified the static elastic, dynamic elastic, and resistive energies comprising mechanical power of ventilation. We stratified by body mass index (BMI) and examined power at four surgical stages: level after intubation, with pneumoperitoneum, in Trendelenburg, and level after releasing the pneumoperitoneum. Esophageal manometry was used to estimate transpulmonary pressures. Mechanical power of ventilation and its bioenergetic components increased over BMI categories. Respiratory system and lung power were nearly doubled in subjects with class 3 obesity compared with lean at all stages. Power dissipated into the respiratory system was increased with class 2 or 3 obesity compared with lean. Increased power of ventilation was associated with decreasing transpulmonary pressures. Body habitus is a prime determinant of increased intraoperative mechanical power. Obesity and surgical conditions increase the energies dissipated into the respiratory system during ventilation. The observed elevations in power may be related to tidal recruitment or atelectasis, and point to specific energetic features of mechanical ventilation of patients with obesity that may be controlled with individualized ventilator settings.NEW & NOTEWORTHY Mechanical power describes the complex interaction between a patient's lungs and the ventilator and may be useful in predicting lung injury. However, its behavior in obesity and during dynamic surgical conditions is not understood. We comprehensively quantified ventilation bioenergetics and effects of body habitus and common surgical conditions. These data show body habitus is a prime determinant of intraoperative mechanical power and provide quantitative context for future translation toward a useful perioperative prognostic measurement.

The neuroendocrine stress response compensates for suppression of insulin secretion by volatile anesthetic agents: An observational study.

Alterations in perioperative metabolic function, particularly hyperglycemia, are associated with increased post-operative complications, even in patients without preexisting metabolic abnormalities. Anesthetic medications and the neuroendocrine stress response to surgery may both contribute to altered energy metabolism through impaired glucose and insulin homeostasis but the discrete pathways involved are unclear. Prior human studies, though informative, have been limited by analytic sensitivity or technique, preventing resolution of underlying mechanisms. We hypothesized that general anesthesia with a volatile agent would suppress basal insulin secretion without altering hepatic insulin extraction, and that surgical stress would promote hyperglycemia through gluconeogenesis, lipid oxidation, and insulin resistance. In order to address these hypotheses, we conducted an observational study of subjects undergoing multi-level lumbar surgery with an inhaled anesthetic agent. We measured circulating glucose, insulin, c-peptide, and cortisol frequently throughout the perioperative period and analyzed the circulating metabolome in a subset of these samples. We found volatile anesthetic agents suppress basal insulin secretion and uncouple glucose-stimulated insulin secretion. Following surgical stimulus, this inhibition disappeared and there was gluconeogenesis with selective amino acid metabolism. No robust evidence of lipid metabolism or insulin resistance was observed. These results show that volatile anesthetic agents suppress basal insulin secretion, which results in reduced glucose metabolism. The neuroendocrine stress response to surgery ameliorates the inhibitory effect of the volatile agent on insulin secretion and glucose metabolism, promoting catabolic gluconeogenesis. A better understanding of the complex metabolic interaction between anesthetic medications and surgical stress is needed to inform design of clinical pathways aimed at improving perioperative metabolic function.

Body Habitus and Dynamic Surgical Conditions Independently Impair Pulmonary Mechanics during Robotic-assisted Laparoscopic Surgery.

BACKGROUND: Body habitus, pneumoperitoneum, and Trendelenburg positioning may each independently impair lung mechanics during robotic laparoscopic surgery. This study hypothesized that increasing body mass index is associated with more mechanical strain and alveolar collapse, and these impairments are exacerbated by pneumoperitoneum and Trendelenburg positioning. METHODS: This cross-sectional study measured respiratory flow, airway pressures, and esophageal pressures in 91 subjects with body mass index ranging from 18.3 to 60.6 kg/m2. Pulmonary mechanics were quantified at four stages: (1) supine and level after intubation, (2) with pneumoperitoneum, (3) in Trendelenburg docked with the surgical robot, and (4) level without pneumoperitoneum. Subjects were stratified into five body mass index categories (less than 25, 25 to 29.9, 30 to 34.9, 35 to 39.9, and 40 or higher), and respiratory mechanics were compared over surgical stages using generalized estimating equations. The optimal positive end-expiratory pressure settings needed to achieve positive end-expiratory transpulmonary pressures were calculated. RESULTS: At baseline, transpulmonary driving pressures increased in each body mass index category (1.9 ± 0.5 cm H2O; mean difference ± SD; P < 0.006), and subjects with a body mass index of 40 or higher had decreased mean end-expiratory transpulmonary pressures compared with those with body mass index of less than 25 (-7.5 ± 6.3 vs. -1.3 ± 3.4 cm H2O; P < 0.001). Pneumoperitoneum and Trendelenburg each further elevated transpulmonary driving pressures (2.8 ± 0.7 and 4.7 ± 1.0 cm H2O, respectively; P < 0.001) and depressed end-expiratory transpulmonary pressures (-3.4 ± 1.3 and -4.5 ± 1.5 cm H2O, respectively; P < 0.001) compared with baseline. Optimal positive end-expiratory pressure was greater than set positive end-expiratory pressure in 79% of subjects at baseline, 88% with pneumoperitoneum, 95% in Trendelenburg, and ranged from 0 to 36.6 cm H2O depending on body mass index and surgical stage. CONCLUSIONS: Increasing body mass index induces significant alterations in lung mechanics during robotic laparoscopic surgery, but there is a wide range in the degree of impairment. Positive end-expiratory pressure settings may need individualization based on body mass index and surgical conditions.

Differences in intraoperative hemodynamics between spinal and general anesthesia in infants undergoing pyloromyotomy.

BACKGROUND: Hypotension and bradycardia are known side effects of spinal anesthesia in pregnant women undergoing cesarean section and adults undergoing other surgical procedures. Whether children experience similar hemodynamic changes is unclear. AIMS: The purpose of this study is to evaluate hemodynamic effects of spinal anesthesia compared to general anesthesia in a cohort of healthy infants. METHODS: The University of Vermont Medical Center almost exclusively used spinal anesthesia for infant pyloromyotomy surgery between 2008 and 2013, while Columbia University Medical Center relied on general anesthesia. The primary outcome assessed was the percentage change in intraoperative heart rate and blood pressure (systolic [SBP] and mean [MAP] blood pressure) from baseline. Analysis was performed using t-tests for continuous variables, followed by linear regression to account for differences in demographic and clinical covariates. RESULTS: The study sample consisted of 51 infants with spinal anesthesia at the University of Vermont and 52 infants with general anesthesia at Columbia University. The decrease from baseline for mean intraoperative SBP was -8.2 ± 16.8% for spinal anesthesia and -24.2 ± 17.2% for general anesthesia (difference between means: 16.2% [95% confidence interval (CI), 9.5-22.9]), while the decrease from baseline for mean intraoperative MAP was -16.3 ± 19.9% for spinal anesthesia and -24.6 ± 19.3% for general anesthesia (difference between means: 8.4% [95% CI, 0.8-16]). Spinal anesthesia patients also had smaller drops in minimum intraoperative MAP and SBP. These blood pressure differences persisted even after adjusting for covariates. No differences in heart rate were seen between spinal and general anesthesia. DISCUSSION: Our findings show that spinal anesthesia performed in healthy infants undergoing pyloromyotomy results in reduced intraoperative blood pressure changes from baseline, significantly higher blood pressure readings, and no increased bradycardia compared to general anesthesia. Further research is needed to assess whether any clinical impact of these hemodynamic differences between spinal and general anesthesia exists.

A Web-Based Operating Room Management Educational Tool.

In 2010, our department instituted a nonclinical, administrative rotation in operating room management for anesthesiology residents. Subsequently, we mandated the rotation for all senior anesthesiology residents in 2013. In 2014, under the auspices of the American Society of Anesthesiologists, we developed a web-based module covering the basics of finance, accounting, and operating room management. A multiple-choice test was given to residents at the beginning and end of the rotation, and we compared the mean scores between residents who took the traditional course and residents who took the web-based module. We found no significant difference between the groups of residents, suggesting that the web-based module is as effective as traditional didactics.

Adverse Events and Resource Utilization After Spinal and General Anesthesia in Infants Undergoing Pyloromyotomy.

BACKGROUND AND OBJECTIVES: Interest in spinal anesthesia (SA) is increasing because of concern about the long-term effects of intravenous (IV) and inhaled anesthetics in young children. This study compared SA versus general anesthesia (GA) in infants undergoing pyloromyotomy. METHODS: Between 2000 to 2013, the University of Vermont Medical Center almost exclusively used SA for infant pyloromyotomy surgery, whereas Columbia University Medical Center relied on GA. Outcomes included adverse events (AEs) within 48 hours of surgery, operating room (OR) time, and postoperative length of stay (LOS). Regression was used to evaluate the association between anesthesia technique and outcomes, accounting for demographic and clinical covariates. RESULTS: We studied 218 infants with SA at the University of Vermont Medical Center and 206 infants with GA at Columbia University Medical Center. In the SA group, 96.3% of infants had adequate initial analgesic levels, but 35.8% required supplemental IV or inhaled anesthetic agents. Compared with GA, the risk of AEs in SA (adjusted odds ratio, 0.60; 95% confidence interval [CI], 0.27-1.36) did not significantly differ, but SA was associated with shorter OR times (17.5 minutes faster; 95% CI, 13.5-21.4 minutes) and shorter postoperative LOS (GA is 1.19 times longer; 95% CI, 1.01-1.40). CONCLUSIONS: Infants undergoing pyloromyotomy with SA had shorter OR times and postoperative LOS, no significant differences in AE rates, and decreased exposure to IV and inhaled anesthetics, although SA infants often still required supplemental anesthetics. Whether these differences result in any long-term benefit is unclear; further studies are needed to determine the risk of rare AEs, such as aspiration.

Cognitive outcome after spinal anesthesia and surgery during infancy.

BACKGROUND: Observational studies on pediatric anesthesia neurotoxicity have been unable to distinguish long-term effects of general anesthesia (GA) from factors associated with the need for surgery. A recent study on elementary school children who had received a single GA during the first year of life demonstrated an association in otherwise healthy children between the duration of anesthesia and diminished test scores and also revealed a subgroup of children with "very poor academic achievement" (VPAA), scoring below the fifth percentile on standardized testing. Analysis of postoperative cognitive function in a similar cohort of children anesthetized with an alternative to GA may help to begin to separate the effects of anesthesia from other confounders. METHODS: We used a novel methodology to construct a combined medical and educational database to search for these effects in a similar cohort of children receiving spinal anesthesia (SA) for the same procedures. We compared former patients with a control population of students matched by grade, gender, year of testing, and socioeconomic status. RESULTS: Vermont Department of Education records were analyzed for 265 students who had a single exposure to SA during infancy for circumcision, pyloromyotomy, or inguinal hernia repair. Exposure to SA and surgery had no significant effect on the odds of children having VPAA. (mathematics: P = 0.18; odds ratio 1.50, confidence interval (CI), 0.83-2.68; reading: P = 0.55; odds ratio = 1.19, CI, 0.67-2.1). There was no relationship between duration of exposure to SA and surgery and performance on mathematics (P = 0.73) or reading (P = 0.57) standardized testing. There was a small but statistically significant decrease in reading and math scores in the exposed group (mathematics: P = 0.03; reading: P = 0.02). CONCLUSIONS: We found no link between duration of surgery with infant SA and scores on academic achievement testing in elementary school. We also found no relationship between infant SA and surgery with VPAA on elementary school testing, although the CIs were wide.

Clonidine as an adjunct to intravenous regional anesthesia: A randomized, double-blind, placebo-controlled dose ranging study.

BACKGROUND: The addition of clonidine to lidocaine intravenous regional anesthesia (IVRA) has been previously reported to improve postoperative analgesia in patients undergoing upper extremity surgery. Our objective was to perform a dose ranging study in order to determine the optimal dose of clonidine used with lidocaine in IVRA. DESIGN #ENTITYSTARTX00026; SETTING: We performed a double-blinded randomized placebo-controlled study with 60 patients scheduled for elective endoscopic carpal tunnel release under IVRA with 50 ml lidocaine 0.5%. University-affiliated outpatient surgery center. Data collected in operating rooms, recovery room, and by telephone after discharge from surgery center. MATERIALS #ENTITYSTARTX00026; METHODS: Sixty adult ASA I or II patients undergoing outpatient endoscopic carpal tunnel release under intravenous regional anesthesia.Patients were randomized into five study groups receiving different doses of clonidine in addition to 50 ml 0.5% lidocaine in their IVRA. Group A received 0 mcg/kg, group B 0.25 mcg/kg, group C 0.5 mcg/kg, group D 1.0 mcg/kg and group E 1.5 mcg/kg of clonidine.Intraoperative fentanyl, recovery room pain scores, time to first postsurgical analgesic, total number of acetaminophen/codeine tablets consumed postsurgery, incidence of sedation, hypotension and bradycardia. RESULTS #ENTITYSTARTX00026; CONCLUSIONS: There was no benefit from any dose of clonidine compared to placebo. There were no clonidine-related side effects seen within the dose range studied. In short duration minor hand surgery, the addition of clonidine to lidocaine-based intravenous regional anesthesia provides no measurable benefit.