The performance of 11 fingertip pulse oximeters during hypoxemia in healthy human participants with varied, quantified skin pigment.

BACKGROUND: Fingertip pulse oximeters are widely available, inexpensive, and commonly used to make clinical decisions in many settings. Device performance is largely unregulated and poorly characterised, especially in people with dark skin pigmentation. METHODS: Eleven popular fingertip pulse oximeters were evaluated using the US Food and Drug Administration (FDA) Guidance (2013) and International Organization for Standardization Standards (ISO, 2017) in 34 healthy humans with diverse skin pigmentation utilising a controlled desaturation study with arterial oxygen saturation (SaO 2) plateaus between 70% and 100%. Skin pigmentation was assessed subjectively using a perceived Fitzpatrick Scale (pFP) and objectively using the individual typology angle (ITA) via spectrophotometry at nine anatomical sites. FINDINGS: Five of 11 devices had a root mean square error (ARMS) > 3%, falling outside the acceptable FDA performance range. Nine devices demonstrated worse performance in participants in the darkest skin pigmentation category compared with those in the lightest category. A commonly used subjective skin colour scale frequently miscategorised participants as being darkly pigmented when compared to objective quantification of skin pigment by ITA. INTERPRETATION: Fingertip pulse oximeters have variable performance, frequently not meeting regulatory requirements for clinical use, and occasionally contradicting claims made by manufacturers. Most devices showed a trend toward worse performance in participants with darker skin pigment. Regulatory standards do not adequately account for the impact of skin pigmentation on device performance. We recommend that the pFP and other non-standardised subjective skin colour scales should no longer be used for defining diversity of skin pigmentation. Reliable methods for characterising skin pigmentation to improve diversity and equitable performance of pulse oximeters are needed. FUNDING: This study was conducted as part of the Open Oximetry Project funded by the Gordon and Betty Moore Foundation, Patrick J McGovern Foundation, and Robert Wood Johnson Foundation. The UCSF Hypoxia Research Laboratory receives funding from multiple industry sponsors to test the sponsors' devices for the purposes of product development and regulatory performance testing. Data in this paper do not include sponsor's study devices. All data were collected from devices procured by the Hypoxia Research Laboratory for the purposes of independent research. No company provided any direct funding for this study, participated in study design or analysis, or was involved in analysing data or writing the manuscript. None of the authors own stock or equity interests in any pulse oximeter companies. Dr Ellis Monk's time utilised for data analysis, reviewing and editing was funded by grant number: DP2MH132941.

Low Perfusion and Missed Diagnosis of Hypoxemia by Pulse Oximetry in Darkly Pigmented Skin: A Prospective Study.

BACKGROUND: Retrospective clinical trials of pulse oximeter accuracy report more frequent missed diagnoses of hypoxemia in hospitalized Black patients than White patients, differences that may contribute to racial disparities in health and health care. Retrospective studies have limitations including mistiming of blood samples and oximeter readings, inconsistent use of functional versus fractional saturation, and self-reported race used as a surrogate for skin color. Our objective was to prospectively measure the contributions of skin pigmentation, perfusion index (PI), sex, and age on pulse oximeter errors in a laboratory setting. METHODS: We enrolled 146 healthy subjects, including 25 with light skin (Fitzpatrick class I and II), 78 with medium (class III and IV), and 43 with dark (class V and VI) skin. We studied 2 pulse oximeters (Nellcor N-595 and Masimo Radical 7) in prevalent clinical use. We analyzed 9763 matched pulse oximeter readings (pulse oximeter measured functional saturation [Sp o2 ]) and arterial oxygen saturation (hemoximetry arterial functional oxygen saturation [Sa o2 ]) during stable hypoxemia (Sa o2 68%-100%). PI was measured as percent infrared light modulation by the pulse detected by the pulse oximeter probe, with low perfusion categorized as PI < 1%. The primary analysis was to assess the relationship between pulse oximeter bias (difference between Sa o2 and Sp o2 ) by skin pigment category in a multivariable mixed-effects model incorporating repeated-measures and different levels of Sa o2 and perfusion. RESULTS: Skin pigment, PI, and degree of hypoxemia significantly contributed to errors (bias) in both pulse oximeters. For PI values of 1.0% to 1.5%, 0.5% to 1.0%, and <0.5%, the P value of the relationship to mean bias or median absolute bias was <.00001. In lightly pigmented subjects, only PI was associated with positive bias, whereas in medium and dark subjects bias increased with both low perfusion and degree of hypoxemia. Sex and age was not related to pulse oximeter bias. The combined frequency of missed diagnosis of hypoxemia (pulse oximeter readings 92%-96% when arterial oxygen saturation was <88%) in low perfusion conditions was 1.1% for light, 8.2% for medium, and 21.1% for dark skin. CONCLUSIONS: Low peripheral perfusion combined with darker skin pigmentation leads to clinically significant high-reading pulse oximeter errors and missed diagnoses of hypoxemia. Darkly pigmented skin and low perfusion states are likely the cause of racial differences in pulse oximeter performance in retrospective studies.

Quantifying pulse oximeter accuracy during hypoxemia and severe anemia using an in vitro circulation system.

Anemia and hypoxemia are common clinical conditions that are difficult to study and may impact pulse oximeter performance. Utilizing an in vitro circulation system, we studied performance of three pulse oximeters during hypoxemia and severe anemia. Three oximeters including one benchtop, one handheld, and one fingertip device were selected to reflect a range of cost and device types. Human blood was diluted to generate four hematocrit levels (40%, 30%, 20%, and 10%). Oxygen and nitrogen were bubbled through the blood to generate a range of oxygen saturations (O2Hb) and the blood was cycled through the in vitro circulation system. Pulse oximeter saturations (SpO2) were paired with simultaneously-measured O2Hb readings from a reference CO-oximeter. Data for each hematocrit level and each device were least-squares fit to a 2nd-order equation with quality of each curve fit evaluated using standard error of the estimate. Bias and average root mean square error were calculated after correcting for the calibration difference between human and in vitro circulation system calibration. The benchtop oximeter maintained good accuracy at all but the most extreme level of anemia. The handheld device was not as accurate as the benchtop, and inaccuracies increased at lower hematocrit levels. The fingertip device was the least accurate of the three oximeters. Pulse oximeter performance is impacted by severe anemia in vitro. The use of in vitro calibration systems may play an important role in augmenting in vivo performance studies evaluating pulse oximeter performance in challenging conditions.

Reducing Volatile Anesthetic Waste Using a Commercial Electronic Health Record Clinical Decision Support Tool to Lower Fresh Gas Flows.

BACKGROUND: Volatile anesthetic consumption can be reduced by minimizing excessive fresh gas flows (FGFs). Currently, it is unknown whether decision support tools embedded within commercial electronic health record systems can be successfully adopted to achieve long-term reductions in FGF rates. The authors describe the implementation of an electronic health record-based clinical decision support tool aimed at reducing FGF and evaluate the effectiveness of this intervention in achieving sustained reductions in FGF rates and volatile anesthetic consumption. METHODS: On August 29, 2018, we implemented a decision support tool within the Epic Anesthesia Information Management System (AIMS) to alert providers of high FGF (>0.7 L/min for desflurane and >1 L/min for sevoflurane) during maintenance of anesthesia. July 22, 2015, to July 10, 2018, served as our baseline period before the intervention. The intervention period spanned from August 29, 2018, to December 31, 2019. Our primary outcomes were mean FGF (L/min) and volatile agent consumption (mL/MAC-h). Because a simple comparison of 2 time periods may result in false conclusions due to underlying trends independent of the intervention, we performed segmented regression of the interrupted time series to assess the change in level at the start of the intervention and the differences in slopes before and after the intervention. The analysis was also adjusted for potential confounding variables. Data included 44,899 cases using sevoflurane preintervention with 26,911 cases postintervention, and 17,472 cases using desflurane with 1185 cases postintervention. RESULTS: Segmented regression of the interrupted times series demonstrated a decrease in mean FGF by 0.6 L/min (95% CI, 0.6-0.6 L/min; P < .0001) for sevoflurane and 0.2 L/min (95% CI, 0.2-0.3 L/min; P < .0001) for desflurane immediately after implementation of the intervention. For sevoflurane, mL/MAC-h decreased by 3.8 mL/MAC-h (95% CI, 3.6-4.1 mL/MAC-h; P < .0001) after implementation of the intervention and decreased by 4.1 mL/MAC-h (95% CI, 2.6-5.6 mL/MAC-h; P < .0001) for desflurane. Slopes for both FGF and mL/MAC-h in the postintervention period were statistically less negative than the preintervention slopes (P < .0001 for sevoflurane and P < .01 for desflurane). CONCLUSIONS: A commercial AIMS-based decision support tool can be adopted to change provider FGF management patterns and reduce volatile anesthetic consumption in a sustainable fashion.

Evaluation of right ventricular function during liver transplantation with transesophageal echocardiography.

BACKGROUND: The pathophysiology of advanced liver cirrhosis may induce alterations in the circulatory system that may be challenging for the anesthesiologist to manage intraoperatively, and perioperative cardiovascular events are associated with worse outcomes in cirrhotic patients undergoing liver transplantation. It remains controversial whether right ventricular function is impaired during this procedure. Studies using transesophageal echocardiography for quantitative analysis of the right ventricle remain scarce in this setting, yielding conflicting results. The aim of this study was to perform a quantitative assessment of right ventricular function with two parameters derived from transesophageal echocardiography during liver transplantation. METHODS: Nineteen adult patients of both genders undergoing liver transplantation were evaluated in this observational study. The exclusion criteria were age under 18 or above 65 years old, fulminant hepatic failure, hepatopulmonary syndrome, portopulmonary hypertension, cardiopulmonary disease, and contraindications to the transesophageal echocardiogram. Right ventricular function was assessed at five stages during liver transplantation: baseline, hepatectomy, anhepatic, postreperfusion, and closure by measuring tricuspid annular plane systolic excursion and right ventricular fractional area change obtained with transesophageal echocardiography. RESULTS: Right ventricular function was found to be normal throughout the procedure. The tricuspid annular plane systolic excursion showed a trend toward a decrease in the anhepatic phase compared to baseline (2.0 ± 0.9 cm vs. 2.4 ± 0.7 cm; P = 0.24) but with full recovery after reperfusion. Right ventricular fractional area change remained nearly constant during all stages studied (minimum: 50% ± 10 at baseline and anhepatic phase; maximum: 56% ± 12 at postreperfusion; P = 0.24). CONCLUSIONS: Right ventricular function was preserved during liver transplantation at the time points evaluated by two quantitative parameters derived from transesophageal echocardiogram.

Frequency, Method, Intensity, and Health Sequelae of Sexual Choking Among U.S. Undergraduate and Graduate Students.

Although sexual choking is now prevalent, little is known about how people engage in choking in terms of frequency, intensity, method, or potential health sequelae. In a campus-representative survey of undergraduate and graduate students, we aimed to: (1) describe the prevalence of ever having choked/been choked as part of sex; (2) examine the characteristics of choking one's sexual partners (e.g., age at first experience, number of partners, frequency, intensity, method); (3) examine the characteristics of having been choked during sex; and (4) assess immediate responses of having been choked including the extent to which frequency and method (e.g., hand, ligature, limb) of having been choked predicts the range of responses endorsed by participants. A total of 4254 randomly sampled students (2668 undergraduate, 1576 graduate) completed a confidential online survey during Spring 2021. The mean age of first choking/being choked was about 19, with more undergraduates than graduate students reporting first choking/being choked in adolescence. Women and transgender/gender non-binary participants were significantly more likely to have been choked than men. Participants more often reported the use of hands compared to limbs or ligature. Common responses to being choked were pleasurable sensations/euphoria (81.7%), a head rush (43.8%), feeling like they could not breathe (43.0%), difficulty swallowing (38.9%), unable to speak (37.6%), and watery eyes (37.2%). About 15% had noticed neck bruising and 3% had lost consciousness from being choked. Greater frequency and intensity of being choked was associated with reports of more physical responses as was use of limb (arm, leg) or ligature.

Pulse Oximeter Performance, Racial Inequity, and the Work Ahead.

It has long been known that many pulse oximeters function less accurately in patients with darker skin. Reasons for this observation are incompletely characterized and potentially enabled by limitations in existing regulatory oversight. Based on decades of experience and unpublished data, we believe it is feasible to fully characterize, in the public domain, the factors that contribute to missing clinically important hypoxemia in patients with darkly pigmented skin. Here we propose 5 priority areas of inquiry for the research community and actionable changes to current regulations that will help improve oximeter accuracy. We propose that leading regulatory agencies should immediately modify standards for measuring accuracy and precision of oximeter performance, analyzing and reporting performance outliers, diversifying study subject pools, thoughtfully defining skin pigmentation, reporting data transparently, and accounting for performance during low-perfusion states. These changes will help reduce bias in pulse oximeter performance and improve access to safe oximeters.

Perioperative Normal Saline Administration and Delayed Graft Function in Patients Undergoing Kidney Transplantation: A Retrospective Cohort Study.

BACKGROUND: Perioperative normal saline administration remains common practice during kidney transplantation. The authors hypothesized that the proportion of balanced crystalloids versus normal saline administered during the perioperative period would be associated with the likelihood of delayed graft function. METHODS: The authors linked outcome data from a national transplant registry with institutional anesthesia records from 2005 to 2015. The cohort included adult living and deceased donor transplants, and recipients with or without need for dialysis before transplant. The primary exposure was the percent normal saline of the total amount of crystalloids administered perioperatively, categorized into a low (less than or equal to 30%), intermediate (greater than 30% but less than 80%), and high normal saline group (greater than or equal to 80%). The primary outcome was the incidence of delayed graft function, defined as the need for dialysis within 1 week of transplant. The authors adjusted for the following potential confounders and covariates: transplant year, total crystalloid volume, surgical duration, vasopressor infusions, and erythrocyte transfusions; recipient sex, age, body mass index, race, number of human leukocyte antigen mismatches, and dialysis vintage; and donor type, age, and sex. RESULTS: The authors analyzed 2,515 records. The incidence of delayed graft function in the low, intermediate, and high normal saline group was 15.8% (61/385), 17.5% (113/646), and 21% (311/1,484), respectively. The adjusted odds ratio (95% CI) for delayed graft function was 1.24 (0.85 to 1.81) for the intermediate and 1.55 (1.09 to 2.19) for the high normal saline group compared with the low normal saline group. For deceased donor transplants, delayed graft function in the low, intermediate, and high normal saline group was 24% (54/225 [reference]), 28.6% (99/346; adjusted odds ratio, 1.28 [0.85 to 1.93]), and 30.8% (277/901; adjusted odds ratio, 1.52 [1.05 to 2.21]); and for living donor transplants, 4.4% (7/160 [reference]), 4.7% (14/300; adjusted odds ratio, 1.15 [0.42 to 3.10]), and 5.8% (34/583; adjusted odds ratio, 1.66 [0.65 to 4.25]), respectively. CONCLUSIONS: High percent normal saline administration is associated with delayed graft function in kidney transplant recipients.

Anesthesia for Maternal-Fetal Interventions: A Survey of Fetal Therapy Centers in the North American Fetal Therapy Network.

INTRODUCTION: A wide range of fetal interventions are performed across fetal therapy centers (FTCs). We hypothesized that there is significant variability in anesthesia staffing and anesthetic techniques. METHODS: We conducted an online survey of anesthesiology directors at every FTC within the North American Fetal Therapy Network (NAFTNet). The survey included details of fetal interventions performed in 2018, anesthesia staffing models, anesthetic techniques, fetal monitoring, and postoperative management. RESULTS: There was a 92% response rate. Most FTCs are located within an adult hospital and employ a small team of anesthesiologists. There is heterogeneity when evaluating anesthesiology fellowship training and staffing, indicating there is a multidisciplinary specialty team-based approach even within anesthesiology. Minimally invasive fetal interventions were the most commonly performed. The majority of FTCs also performed ex utero intrapartum treatment (EXIT) and open mid-gestation procedures under general anesthesia (GA). Compared to FTCs only performing minimally invasive procedures, FTCs performing open fetal procedures were more likely to have a pediatric surgeon as director and performed more minimally invasive procedures. CONCLUSIONS: There is considerable variability in anesthesia staffing, caseload, and anesthetic techniques among FTCs in NAFTNet. Most FTCs used maternal sedation for minimally invasive procedures and GA for EXIT and open fetal surgeries.

Pediatric Distraction on Induction of Anesthesia With Virtual Reality and Perioperative Anxiolysis: A Randomized Controlled Trial.

BACKGROUND: Perioperative pediatric anxiety is common and can have a negative psychological impact on children undergoing surgery and anesthesia. Studies have shown an incidence of anxiety at induction of up to 50%. Audiovisual distraction, including virtual reality (VR), is a noninvasive, nonpharmacological modality that may reduce perioperative anxiety. The goal of this study was to determine whether immersive audiovisual distraction with a VR headset during induction of general anesthesia (GA) in pediatric patients reduced preoperative anxiety. METHODS: In this randomized-controlled, parallel-group study, 71 children 5-12 years of age scheduled for elective surgery with GA were randomly allocated to a VR group or a non-VR (No VR) control group. VR group patients underwent audiovisual distraction with a VR headset during induction in the operating room, whereas the control group received no audiovisual distraction. The primary outcome was the Modified Yale Preoperative Anxiety Scale (mYPAS), which was measured at 3 time points to assess patient anxiety: in the preoperative holding area before randomization, on entering the operating room, and during induction of GA. The primary outcome was analyzed using univariate analysis and a linear mixed-effects model. Secondary outcomes included postinduction parental anxiety measured by the State-Trait Anxiety Inventory, pediatric induction compliance, and parental satisfaction. RESULTS: Average patient age was 8.0 ± 2.3 years (mean ± standard deviation [SD]), and 51.4% of patients were female. Baseline variables were not substantially different between the VR group (33 patients) and the No VR group (37 patients). No patients received preoperative anxiolytic medication. Baseline mYPAS scores were not different between the groups, with scores of 28.3 (23.3-28.3) (median [interquartile range {IQR}]) in both. The change in mYPAS scores from baseline to time of induction was significantly lower in the VR group versus control group (0.0 [0.0-5.0] vs 13.3 [5.0-26.7]; P < .0001). In the mixed-effects model, the VR group had an estimated 6.0-point lower mYPAS score (95% confidence interval [CI], 0.7-11.3; P = .03) at room entry than the No VR group, and 14.5-point lower score (95% CI, 9.3-19.8; P < .0001) at induction versus control. Randomization to VR did not alter parental anxiety (0 [-2 to 2]), pediatric induction compliance (0 [0-0]), or parental satisfaction (-3 [-8 to 2]) (difference in medians [95% CI]). CONCLUSIONS: This study demonstrates a reduction in pediatric preoperative anxiety with the use of VR. Preoperative VR may be an effective noninvasive modality for anxiolysis during induction of anesthesia in children.

New Method of Destroying Waste Anesthetic Gases Using Gas-Phase Photochemistry.

BACKGROUND: The inhalation anesthetics are potent greenhouse gases. To reduce the global environmental impact of the health care sector, technologies are sought to limit the release of waste anesthetic gas into the atmosphere. METHODS: Using a photochemical exhaust gas destruction system, removal efficiencies for nitrous oxide, desflurane, and sevoflurane were measured at various inlet concentrations (25% and 50%; 1.5%, 3.0%, and 6.0%; and 0.5%, 1.0%, and 2.0%, respectively) with flow rates ranging from 0.25 to 2.0 L/min. To evaluate the economic competitiveness of the anesthetic waste gas destruction system, its price per ton of carbon dioxide equivalent was calculated and compared to other greenhouse gas abatement technologies and current market prices. RESULTS: All inhaled anesthetics evaluated demonstrate enhanced removal efficiencies with decreasing flow rates (P < .0001). Depending on the anesthetic and its concentration, the photochemical exhaust gas destruction system exhibits a constant first-order removal rate, k. However, there was not a simple relation between the removal rate k and the species concentration. The costs for removing a ton of carbon dioxide equivalents are <$0.005 for desflurane, <$0.114 for sevoflurane, and <$49 for nitrous oxide. CONCLUSIONS: Based on this prototype study, destroying sevoflurane and desflurane with this photochemical anesthetic waste gas destruction system design is efficient and cost-effective. This is likely also true for other halogenated inhalational anesthetics such as isoflurane. Due to differing chemistry of nitrous oxide, modifications of this prototype photochemical reactor system are necessary to improve its removal efficiency for this gas.

The Association Between Vena Cava Implantation Technique and Acute Kidney Injury After Liver Transplantation.

BACKGROUND: Acute kidney injury (AKI) after liver transplantation is associated with increased morbidity and mortality. It remains controversial whether the choice of vena cava reconstruction technique impacts AKI. METHODS: This is a single-center retrospective cohort of 897 liver transplants performed between June 2009 and September 2018 using either the vena cava preserving piggyback technique or caval replacement technique without veno-venous bypass or shunts. The association between vena cava reconstruction technique and stage of postoperative AKI was assessed using multivariable ordinal logistic regression. Causal mediation analysis was used to evaluate warm ischemia time as a potential mediator of this association. RESULTS: The incidence of AKI (AKI stage ≥2) within 48 h after transplant was lower in the piggyback group (40.3%) compared to the caval replacement group (51.8%, P < 0.001). Piggyback technique was associated with a reduced risk of developing a higher stage of postoperative AKI (odds ratio, 0.49; 95% confidence interval, 0.37-0.65, P < 0.001). Warm ischemia time was shorter in the piggyback group and identified as potential mediator of this effect. There was no difference in renal function (estimated glomerular filtration rate and the number of patients alive without dialysis) 1 y after transplant. CONCLUSIONS: Piggyback technique, compared with caval replacement, was associated with a reduced incidence of AKI after liver transplantation. There was no difference in long-term renal outcomes between the 2 groups.

A Comparison of Spinal Anesthesia Versus Monitored Anesthesia Care With Local Anesthesia in Minimally Invasive Fetal Surgery.

BACKGROUND: Minimally invasive fetal surgery is commonly performed to treat twin-to-twin transfusion syndrome with selective fetoscopic laser photocoagulation and twin-reversed arterial perfusion sequence using radiofrequency ablation. Although an increasing number of centers worldwide are performing these procedures, anesthetic management varies. Both neuraxial anesthesia and monitored anesthesia care with local anesthesia are used at different institutions. We sought to determine the efficacy and outcomes of these 2 anesthetic techniques for fetal procedures at our institution. METHODS: All patients undergoing minimally invasive fetal surgery for twin-to-twin transfusion syndrome or twin-reversed arterial perfusion sequence over a 6-year time period (2011-2016) were reviewed. Patients receiving monitored anesthesia care with local anesthesia were compared with those receiving spinal anesthesia in both selective fetoscopic laser photocoagulation and radiofrequency ablation fetal procedures. The primary outcome examined between the monitored anesthesia care and spinal anesthesia groups was the difference in conversion to general anesthesia using a noninferiority design with a noninferiority margin of 5%. Secondary outcome measures included use of vasopressors, procedure times, intraoperative fluids administered, maternal complications, and unexpected fetal demise within 24 hours of surgery. RESULTS: The difference in failure rate between monitored anesthesia care and spinal was -0.5% (95% CI, -4.8% to 3.7%). Patients receiving monitored anesthesia care plus local anesthesia were significantly less likely to need vasopressors, had a shorter presurgical operating room time, and received less fluid (P < .001). Operative time did not differ significantly. CONCLUSIONS: Monitored anesthesia care plus local anesthesia is a reliable and safe anesthetic choice for minimally invasive fetal surgery. Furthermore, it decreases maternal hemodynamic instability and reduces preincision operating room time.

The reliability of motor evoked potentials to predict dorsiflexion injuries during lumbosacral deformity surgery: importance of multiple myotomal monitoring.

STUDY DESIGN: Case-control analysis of transcranial motor evoked potential (MEP) responses and clinical outcome. OBJECTIVE: To determine the sensitivity and specificity of MEPs to predict isolated nerve root injury causing dorsiflexion weakness in selected patients having complex lumbar spine surgery. SUMMARY OF BACKGROUND DATA: The surgical correction of distal lumbar spine deformity involves significant risk for damage to neural structures that control muscles of ankle and toe dorsiflexion. Procedures often include vertebral translation, interbody fusion, and posterior-based osteotomies. The benefit of using MEP monitoring to predict dorsiflexion weakness has not been well-established. The purpose of this paper is to describe the relationship between neural complications from lumbar surgery and intraoperative MEP changes. METHODS: Included were 542 neurologically intact patients who underwent posterior spinal fusion for the correction of distal lumbar deformity. Two myotomes, including tibialis anterior (TA) and extensor hallucis longus (EHL), were monitored. MEP and free-running electromyography data were assessed in each patient. Cases of new dorsiflexion weakness noted postoperatively were identified. Data in case and control patients were compared. There was no direct funding for this work. The Department of Anesthesiology and Perioperative Care provides salary support for authors one and six. Authors two and three report employment in the field of intraoperative neurophysiological monitoring as a study-specific conflict of interest. RESULTS: Twenty-five patients (cases) developed dorsiflexion weakness. MEP amplitude decreased in the injured myotomes by an average of 65 ± 21% (TA) and 60±26% (EHL), which was significantly greater than the contralateral uninjured side or for control subjects. (p < .01) Receiver operator characteristic (ROC) curves showed high sensitivity, specificity, and predictive value for changes in MEP amplitude using either the TA or EHL. Analysis of MEP changes to either TA or EHL yielded a superior ROC curve. Net reclassification improvement analysis showed assessing MEP changes to both TA and EHL improved the predictability of injury. CONCLUSIONS: The use of MEP amplitude change is highly sensitive and specific to predict a new postoperative dorsiflexion injury. Monitoring two myotomes (both TA and EHL) is superior to relying on MEP changes from a single myotome. Electromyography activity was less accurate but compliments MEP use. Additional studies are needed to define optimal intraoperative MEP warning thresholds.

Increased Cytokines at High Altitude: Lack of Effect of Ibuprofen on Acute Mountain Sickness, Physiological Variables, or Cytokine Levels.

Lundeberg, Jenny, John R. Feiner, Andrew Schober, Jeffrey W. Sall, Helge Eilers, and Philip E. Bickler. Increased cytokines at high altitude: lack of effect of ibuprofen on acute mountain sickness, physiological variables or cytokine levels. High Alt Med Biol. 19:249-258, 2018. INTRODUCTION: There is no consensus on the role of inflammation in high-altitude acclimatization. AIMS: To determine the effects of a nonsteroidal anti-inflammatory drug (ibuprofen 400 mg every 8 hours) on blood cytokines, acclimatization, acute mountain sickness (AMS, Lake Louise Score), and noninvasive oxygenation in brain and muscle in healthy volunteers. MATERIALS AND METHODS: In this double-blind study, 20 volunteers were randomized to receive ibuprofen or placebo at sea level and for 48 hours at 3800 m altitude. Arterial, brain, and leg muscle saturation with near infrared spectroscopy, pulse oximetry, and heart rate were measured. Blood samples were collected for cytokine levels and cytokine gene expression. RESULTS: All of the placebo subjects and 8 of 11 ibuprofen subjects developed AMS at altitude (p = 0.22, comparing placebo and ibuprofen). On arrival at altitude, the oxygen saturation as measured by pulse oximetry (SpO2) was 84.5% ± 5.4% (mean ± standard deviation). Increase in blood interleukin-1ß (IL-1ß), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels occurred comparably in the placebo and ibuprofen groups (all not significant, univariate test by Wilcoxon rank sum). Increased IL-6 was associated with higher AMS scores (p = 0.002 by Spearman rank correlation). However, we found no difference or association in AMS score and blood or tissue oxygenation between the ibuprofen and placebo groups. CONCLUSIONS: We found that ibuprofen, at the package-recommended adult dose, did not have a significant effect on altitude-related increases in cytokines, AMS scores, blood, or tissue oxygenation in a population of healthy subjects with a high incidence of AMS.

Central venous pressure monitoring in living donor kidney recipients does not affect immediate graft function: A propensity score analysis.

BACKGROUND: During kidney transplantation, intraoperative fluid management can affect post-transplant graft function. It is unclear whether or not central venous pressure (CVP) monitoring is required to guide fluid therapy during kidney transplantation. METHODS: We compared post-transplant graft function in recipients of living donor kidney transplants between August 2006 and March 2009 based on the use or absence of intraoperative CVP monitoring. Graft function, assessed using the creatinine reduction ratio on postoperative day 2 (CCR2), was evaluated by multivariable linear regression analysis and in a propensity-matched cohort. RESULTS: Two hundred and ninety patients were included in the analysis. Central venous pressure was monitored in 84 patients (29%). There was no difference in post-transplant graft function, as measured by CCR2, between patients with and without CVP monitoring in both unadjusted and multivariable-adjusted analyses. There were also no statistically significant differences in CCR2, delayed graft function, or 3-month renal function between those monitored with CVP and those without, in the propensity-matched cohort. CONCLUSIONS: In this single-center analysis, immediate post-transplant renal function was not associated with the use of intraoperative CVP monitoring.

Intraoperative Management of Liver Transplant Patients Without the Routine Use of Renal Replacement Therapy.

BACKGROUND: Renal failure is common among patients undergoing liver transplantation. Liver allocation based on the model for end-stage liver disease score has increased the number of recipients who require perioperative renal replacement therapy (RRT). Although RRT can be continued intraoperatively, the risks and benefits of intraoperative RRT are not well defined. The aim of this study is to report the intraoperative management of patients with pretransplant renal failure at a transplant center with extremely infrequent utilization of intraoperative RRT. MATERIALS AND METHODS: We performed a retrospective analysis of all adult patients undergoing orthotopic liver or simultaneous liver-kidney (SLK) transplantation between June 2009 and December 2015. Patients were divided into 2 groups based on their need for pretransplant RRT. RESULTS: A total of 785 patients underwent liver or SLK transplant during the study period. One hundred and seventy-four patients (22.2%) required preoperative dialysis. Only 2 patients required intraoperative RRT. There was no difference in the incidence of acidosis or hyperkalemia between patients who required preoperative dialysis and those who did not. CONCLUSIONS: We describe the successful management of patients undergoing liver or SLK transplantation almost entirely without the need for intraoperative RRT.

Changes in transcranial motor evoked potentials during hemorrhage are associated with increased serum propofol concentrations.

Transcranial motor evoked potentials (TcMEPs) monitor the integrity of the spinal cord during spine surgery. Propofol-based anesthesia is favored in order to enhance TcMEP quality. During intraoperative hemorrhage, TcMEP amplitudes may be reduced. The serum concentration of propofol may increase during hemorrhage. No study has determined whether changes in TcMEPs due to hemorrhage are related to changes in propofol blood levels. We monitored TcMEPs, mean arterial pressure (MAP), and cardiac output (CO) and hemoglobin in pigs (n = 6) undergoing controlled progressive hemorrhage during a standardized anesthetic with infusions of propofol, ketamine, and fentanyl. We recorded TcMEPs from the rectus femoris (RF) and tibialis anterior (TA) muscles bilaterally. A pulmonary artery catheter was placed to measure CO. Progressive hemorrhage of 10% blood volume increments was done until TcMEP amplitude decreased by >60% from baseline. Serum propofol levels were also measured following removal of each 10% blood volume increment. TcMEP responses were elicited every 3 min using constant stimulation parameters. We removed between 20 and 50% of total blood volume in order to achieve the >60% reduction in TcMEP amplitude. MAP and CO decreased significantly from baseline. At maximum hemorrhage, TcMEP amplitude decreased in the RF and TA by an average of 73 and 62% respectively from baseline (P < 0.01). Serum propofol levels varied greatly among animals at baseline (range 410-1720 ng/mL) and increased in each animal during hemorrhage. The mean propofol concentration rose from 1190 ± 530 to 2483 ± 968 ng/mL (P < 0.01). The increased propofol concentration correlated with decreased CO. Multivariate analysis using hierarchical linear models indicated that the decline of TcMEP amplitude was primarily associated with rising propofol concentrations, but was also independently affected by reduced CO. We believe that the decrease in blood volume and CO during hemorrhage increased the serum concentration of propofol by reducing the volume of distribution and/or rate of hepatic metabolism of the drug. Despite wide acceptance of propofol as the preferred anesthetic when using TcMEPs, intravenous anesthetics are vulnerable to altered pharmacokinetics during conditions of hemorrhage and could contribute to false-positive TcMEP changes.