University of Texas Southwestern Medical Center

Ambulatory Anesthesia

Rosero EB, Joshi GP. Nationwide use and outcomes of ambulatory surgery in morbidly obese patients in the United States. J Clin Anesth. 2014; 26(3):191-198. PMID: 24806076.

This study compared the overall characteristics and perioperative outcomes of morbidly obese and non-obese patients undergoing ambulatory surgery. The study was initiated by the authors based on the following clinical and epidemiological observations: 1) the prevalence of morbid obesity (body mass index [BMI] ≥40/m2) is rapidly increasing in the United States; 2) morbid obesity is associated with increased risk of comorbidities, and, therefore, ambulatory surgery in the morbidly obese patients remains controversial; and 3) literature regarding the safety of ambulatory surgery in morbidly obese patients is sparse. The data was derived from The National Survey of Ambulatory Surgery from the National Center for Health Statistics. A propensity score analysis of matched groups was used to compare postoperative outcomes between morbidly obese and non-obese patients. The study found that out of 31,377,481 adult patients undergoing ambulatory surgical procedures, 98,106 (0.32%) were performed on patients with a diagnosis of morbid obesity. Morbidly obese patients were younger but they had significantly higher comorbidity scores. However, the rate of postoperative adverse outcomes and the incidence of delayed discharge from surgical facilities were not higher among the morbidly obese patients. Of note, morbidly obese patients were more likely to have the procedures performed in hospital settings, suggesting that conservative patient selection criteria were applied to morbidly obese patients offered surgery in ambulatory surgery settings. In summary our study suggests that after appropriate patient and facility selection, morbid obesity is not an independent risk factor for perioperative complications in ambulatory surgery.

Cardiac Anesthesia

Steiner ME, Ness PM, Assmann SF, Triulzi DJ, Sloan SR, Delaney M, Granger S, Bennett-Guerrero E, Blajchman MA, Scavo V, Carson JL, Levy JH, Whitman G, D'Andrea P, Pulkrabek S, Ortel TL, Bornikova L, Raife T, Puca KE, Kaufman RM, Nuttall GA, Young PP, Youssef S, Engelman R, Greilich PE, Miles R, Josephson CD, Bracey A, Cooke R, McCullough J, Hunsaker R, Uhl L, McFarland JG, Park Y, Cushing MM, Klodell CT, Karanam R, Roberts PR, Dyke C, Hod EA, Stowell CP. Effects of red-cell storage duration on patients undergoing cardiac surgery. N Engl J Med. 2015;372(15):1419-1429. PMID: 25853746

Cardiac surgical patients are a group at high risk for requiring blood transfusion. Some observational studies have reported that transfusion of units of red blood cells that have been stored for longer periods of time (2-3 weeks) is associated with increased incidence of serious postoperative adverse events when compared with transfusion of red-cell units that have been stored for less time. UT Southwestern University Hospital was one of the participating sites in the RECESS trial, which was a multi-site randomized trial that enrolled from 2010 to 2014. In the RECESS trial subjects older than 12 y undergoing complex surgery (n=1098) were randomized to receive leukocyte-reduced red cells stored for < 10 days versus > 21 days for all intraoperative and postoperative transfusions. Duration of red-cell storage was not associated with significant differences in the change in Multiple Organ Dysfunction Score (MODS).

Quality of care related to blood transfusion in cardiac surgery is a research focus of the cardiothoracic anesthesia division at UT Southwestern.

General Anesthesia

Matchett G, Wood P. General anesthesia suppresses normal heart rate variability in humans. Chaos: An Interdisciplinary Journal of Nonlinear Science. 2014; 24 http://scitation.aip.org/content/aip/journal/chaos/24/2/10.1063/1.4882395

The normal human heart exhibits robust beat-to-beat heart rate variability (HRV). Loss of this variability is associated with cardiac pathology, including congestive heart failure (CHF). The effect of general anesthesia on HRV is unknown. This was a prospective observational study of 100 human subjects undergoing elective major surgery under general anesthesia. HRV data was recorded using continuous electrocardiogram (ECG) before, during, and after anesthesia, and HRV was assessed using R-R intervals on the ECG. Detrended fluctuation analysis (DFA), multifractal, and multiscale entropy analyses were performed were each performed four different times over the course of 24 h: before anesthesia, during anesthesia, early recovery, and late recovery. Qualitatively, the reduction in HRV under anesthesia appears similar to the reduction in HRV observed in CHF. Following the conclusion of general anesthesia, most study subjects regained their baseline HRV, although this did not occur immediately. Future studies are needed to explore the association between reduced HRV as well as pattern of postoperative recovery of HRV and postoperative cardiac events.

Obstetric Anesthesia

Craig M, Grant E, Tao W, McIntire D, Leveno K. A randomized control trial of bupivacaine and fentanyl versus fentanyl-only for epidural analgesia during the second stage of labor. Anesthesiology 2015; 122(1):172-177 PMID: 25254902

In this randomized controlled trial, 310 nulliparous women who received epidural analgesia for labor were recruited to determine if administration of epidural fentanyl-only given at the onset of the second stage of labor actually shortened the second stage of labor in comparison to administration of epidural bupivacaine plus fentanyl. It has been hypothesized that epidural analgesia prolongs the second stage of labor because of the dense motor blockade induced by local anesthetics. However, this study found that irrespective of whether bupivacaine was utilized in the epidural infusion versus fentanyl used alone in the epidural infusion, duration of the second stage of labor, degree of motor blockade, mode of delivery, quality of analgesia, and maternal and neonatal outcomes did not differ between the two intervention groups. However, in the fentanyl-only epidural infusion group, there was a fivefold increase in opioid exposure to the fetus. The neurobehavioral effects of this increased fentanyl exposure on the fetus was not assessed in this study beyond the immediate postnatal period.

http://anesthesiology.pubs.asahq.org/article.aspx?articleid=2043047

Pediatric Anesthesia

Szmuk P, Steiner J, Olomu P, Dela Cruz J, Sessler D. Oxygen reserve index – a new, noninvasive method of oxygen reserve measurement. Proceedings of the American Society of Anesthesiologists, October 14th, 2014, New Orleans, LA.

The study was performed at Children’s Medical Center in Dallas, Texas. It is the first report on a new noninvasive monitoring parameter Oxygen Reserve Index (ORI). The authors demonstrated that ORI can provide advanced warning of potential hypoxia and may help clinicians optimize oxygenation before and during prolonged intubation of pediatric patients. The study was among 12 selected from more than 1,000 submitted abstracts as one of the Best Abstracts at the 2014 American Society of Anesthesiologists’ (ASA) Annual Meeting.