Pro-Con Debate: Role of Methadone in Enhanced Recovery After Surgery Protocols-Superior Analgesic or Harmful Drug?

Enhanced recovery after surgery (ERAS) protocols are standardized and designed to provide superior analgesia, reduce opioid consumption, improve patient recovery, and reduce hospital length of stay. Yet, moderate-to-severe postsurgical pain continues to afflict over 40% of patients and remains a major priority for anesthesia research. Methadone administration in the perioperative setting may reduce postoperative pain scores and have opioid-sparing effects, which may be beneficial for enhanced recovery. Methadone possesses a multimodal profile consisting of µ-opioid agonism, N-methyl-d-aspartate (NMDA) receptor antagonism, and reuptake inhibition of serotonin and norepinephrine. Furthermore, it may attenuate the development of chronic postsurgical pain. However, caution is advised with perioperative use of methadone in specific high-risk patient populations and surgical settings. Methadone's wide pharmacokinetic variability, opioid-related adverse effects, and potential negative impact on cost-effectiveness may also limit its use in the perioperative setting. In this PRO-CON commentary article, the authors debate whether methadone should be incorporated in ERAS protocols to provide superior analgesia with no increased risks.

Mobile health supported multi-domain recovery trajectories after major arthroplasty or spine surgery: a pilot feasibility and usability study.

BACKGROUND: Recovery after surgery intersects physical, psychological, and social domains. In this study we aim to assess the feasibility and usability of a mobile health application called PositiveTrends to track recovery in these domains amongst participants undergoing hip, knee arthroplasty or spine surgery. Our secondary aim was to generate procedure-specific, recovery trajectories within the pain and medication, psycho-social and patient-reported outcomes domain. METHODS: Prospective, observational study in participants greater than eighteen years of age. Data was collected prior to and up to one hundred and eighty days after completion of surgery within the three domains using PositiveTrends. Feasibility was assessed using participant response rates from the PositiveTrends app. Usability was assessed quantitatively using the System Usability Scale. Heat maps and effect plots were used to visualize multi-domain recovery trajectories. Generalized linear mixed effects models were used to estimate the change in the outcomes over time. RESULTS: Forty-two participants were enrolled over a four-month recruitment period. Proportion of app responses was highest for participants who underwent spine surgery (median = 78, range = 36-100), followed by those who underwent knee arthroplasty (median = 72, range = 12-100), and hip arthroplasty (median = 62, range = 12-98). System Usability Scale mean score was 82 ± 16 at 180 days postoperatively. Function improved by 8 and 6.4 points per month after hip and knee arthroplasty, respectively. In spine participants, the Oswestry Disability Index decreased by 1.4 points per month. Mood improved in all three cohorts, however stress levels remained elevated in spine participants. Pain decreased by 0.16 (95% Confidence Interval: 0.13-0.20, p < 0.001), 0.25 (95% CI: 0.21-0.28, p < 0.001) and 0.14 (95% CI: 0.12-0.15, p < 0.001) points per month in hip, knee, and spine cohorts respectively. There was a 10.9-to-40.3-fold increase in the probability of using no medication for each month postoperatively. CONCLUSIONS: In this study, we demonstrate the feasibility and usability of PositiveTrends, which can map and track multi-domain recovery trajectories after major arthroplasty or spine surgery.

Carbon Dioxide, Blood Pressure, and Perioperative Stroke: A Retrospective Case-Control Study.

BACKGROUND: The relationship between intraoperative physiology and postoperative stroke is incompletely understood. Preliminary data suggest that either hypo- or hypercapnia coupled with reduced cerebrovascular inflow (e.g., due to hypotension) can lead to ischemia. This study tested the hypothesis that the combination of intraoperative hypotension and either hypo- or hypercarbia is associated with postoperative ischemic stroke. METHODS: We conducted a retrospective, case-control study via the Multicenter Perioperative Outcomes Group. Noncardiac, nonintracranial, and nonmajor vascular surgical cases (18 yr or older) were extracted from five major academic centers between January 2004 and December 2015. Ischemic stroke cases were identified via manual chart review and matched to controls (1:4). Time and reduction below key mean arterial blood pressure thresholds (less than 55 mmHg, less than 60 mmHg, less than 65 mmHg) and outside of specific end-tidal carbon dioxide thresholds (30 mmHg or less, 35 mmHg or less, 45 mmHg or greater) were calculated based on total area under the curve. The association between stroke and total area under the curve values was then tested while adjusting for relevant confounders. RESULTS: In total, 1,244,881 cases were analyzed. Among the cases that screened positive for stroke (n = 1,702), 126 were confirmed and successfully matched with 500 corresponding controls. Total area under the curve was significantly associated with stroke for all thresholds tested, with the strongest combination observed with mean arterial pressure less than 55 mmHg (adjusted odds ratio per 10 mmHg-min, 1.17 [95% CI, 1.10 to 1.23], P < 0.0001) and end-tidal carbon dioxide 45 mmHg or greater (adjusted odds ratio per 10 mmHg-min, 1.11 [95% CI, 1.10 to 1.11], P < 0.0001). There was no interaction effect observed between blood pressure and carbon dioxide. CONCLUSIONS: Intraoperative hypotension and carbon dioxide dysregulation may each independently increase postoperative stroke risk.

Anesthesiologist Age and Sex Influence Patient Perceptions of Physician Competence.

BACKGROUND: Uncovering patients' biases toward characteristics of anesthesiologists may inform ways to improve the patient-anesthesiologist relationship. The authors previously demonstrated that patients prefer anesthesiologists displaying confident body language, but did not detect a sex bias. The effect of anesthesiologists' age on patient perceptions has not been studied. In this follow-up study, it was hypothesized that patients would prefer older-appearing anesthesiologists over younger-appearing anesthesiologists and male over female anesthesiologists. METHODS: Three hundred adult, English-speaking patients were recruited in the Preanesthesia Evaluation and Testing Center. Patients were randomized (150 per group) to view a set of four videos in random order. Each 90-s video featured an older female, older male, younger female, or younger male anesthesiologist reciting the same script describing general anesthesia. Patients ranked each anesthesiologist on confidence, intelligence, and likelihood of choosing the anesthesiologist to care for their family member. Patients also chose the one anesthesiologist who seemed most like a leader. RESULTS: Three hundred patients watched the videos and completed the questionnaire. Among patients younger than age 65 yr, the older anesthesiologists had greater odds of being ranked more confident (odds ratio, 1.92; 95% CI, 1.41 to 2.64; P < 0.001) and more intelligent (odds ratio, 2.24; 95% CI, 1.62 to 3.11; P < 0.001), and had greater odds of being considered a leader (odds ratio, 2.62; 95% CI, 1.72 to 4.00; P < 0.001) when compared with younger anesthesiologists. The preference for older anesthesiologists was not observed in patients age 65 and older. Female anesthesiologists had greater odds of being ranked more confident (odds ratio, 1.46; 95% CI, 1.13 to 1.87; P = 0.003) and more likely to be chosen to care for one's family member (odds ratio, 1.80; 95% CI, 1.40 to 2.31; P < 0.001) compared with male anesthesiologists. The ranking preference for female anesthesiologists on these two measures was observed among white patients and not among nonwhite patients. CONCLUSIONS: Patients preferred older anesthesiologists on the measures of confidence, intelligence, and leadership. Patients also preferred female anesthesiologists on the measures of confidence and likelihood of choosing the anesthesiologist to care for one's family member.

Anesthetic management during transsphenoidal pituitary surgery.

PURPOSE OF REVIEW: Pituitary adenoma resections comprise a large proportion of intracranial tumor surgeries. This patient population is medically and physiologically complex and requires careful perioperative planning and management on the part of the anesthesiologist. This review will summarize anesthetic considerations for pre, intra, and postoperative management of patients undergoing transsphenoidal pituitary surgery. RECENT FINDINGS: An endoscopic approach is favored for patients undergoing transsphenoidal pituitary surgery. Hemodynamic monitoring is important to maintain cerebral perfusion and avoid risk of bleeding; however, 'controlled' hypotension may have adverse effects. Multimodal analgesia is effective for the management of postoperative pain and may reduce the risk of postoperative complications, including respiratory depression and postoperative nausea and vomiting. SUMMARY: Transsphenoidal pituitary surgery is a preferred approach for the surgical management of nonfunctioning pituitary macroadenomas with symptoms of mass effect and functioning adenomas that cannot be otherwise managed medically. Understanding tumor pathologies and systemic effects are essential for preoperative planning and providing safe anesthetic care during the perioperative period.

Ventilator Mode Does Not Influence Blood Loss or Transfusion Requirements During Major Spine Surgery: A Retrospective Study.

BACKGROUND: Blood loss during adult spinal deformity surgery is multifactorial. Anesthetic-related factors, such as mode of mechanical ventilation, may contribute to intraoperative blood loss. The aim of this study was to determine the influence of ventilator mode and ventilator parameters on intraoperative blood loss and transfusion requirements in patients undergoing prone position spine surgery. METHODS: This single-center retrospective study examined electronic medical records of patients ≥18 years of age who underwent elective prone position spine surgery between May 2015 and June 2016. Associations between ventilator mode and ventilator parameters with intraoperative estimated blood loss (EBL), packed red blood cells (PRBCs), fresh-frozen plasma (FFP), cryoprecipitate and platelet transfusions, and subfascial drain output were examined using multiple linear regression models controlling for age, sex, American Society of Anesthesiologist (ASA) physical status score, body mass index (BMI), preoperative blood coagulation parameters and laboratory values, operative levels, cage constructs, osteotomies, transforaminal lumbar interbody fusions, laminectomies, reoperation, spine surgery invasiveness index, and operative time. In a secondary analysis, EBL, blood product transfusions, and postoperative drain output were compared between pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV) propensity score-matched cohorts. RESULTS: Nine hundred forty-six records were reviewed, and 822 were included in the analysis. After adjusting for confounding, no statistically significant associations were observed between mode of ventilation and intraoperative EBL (estimate, -2; 95% confidence interval [CI], -248 to 245; P = .99) or blood product transfusions (PRBC: estimate, -9; 95% CI, -154 to 135; P = .90; FFP: estimate, -3; 95% CI, -59 to 54; P = .93; cryoprecipitate: estimate, -14; 95% CI, -70 to 43; P = .63; platelets: -7; 95% CI, -39 to 24; P = .64). After propensity score matching (n = 27 per group), no significant differences were observed in EBL (mean difference, 525 mL; 95% CI, -15 to 1065; P = .056) or blood transfusions (PRBC: mean difference, 208 mL; 95% CI, -23 to 439; P = .077; FFP (mean difference, 34 mL; 95% CI, -17 to 84; P = .19); cryoprecipitate (mean difference, 55 mL; 95% CI, -24 to 133; P = .17); or platelets (mean difference, 26 mL; 95% CI, -12 to 64; P = .18) between PCV and VCV groups. CONCLUSIONS: In prone position spine surgery, neither mode of mechanical ventilation nor airway pressure is associated with intraoperative blood loss or need for allogeneic transfusion. Use of modern ventilation strategies using lung protective techniques may mitigate differences in blood loss previously observed between PCV and VCV modes.

Anesthesiology Resident Night Float Duty Alters Sleep Patterns: An Observational Study.

BACKGROUND: Residency programs utilize night float systems to adhere to duty hour restrictions; however, the influence of night float on resident sleep has not been described. The study aim was to determine the influence of night float on resident sleep patterns and quality of sleep. We hypothesized that total sleep time decreases during night float, increases as residents acclimate to night shift work, and returns to baseline during recovery. METHODS: This was a single-center observational study of 30 anesthesia residents scheduled to complete six consecutive night float shifts. Electroencephalography sleep patterns were recorded during baseline (three nights), night float (six nights), and recovery (three nights) using the ZMachine Insight monitor (General Sleep Corporation, USA). Total sleep time; light, deep, and rapid eye movement sleep; sleep efficiency; latency to persistent sleep; and wake after sleep onset were observed. RESULTS: Mean total sleep time ± SD was 5.9 ± 1.9 h (3.0 ± 1.2.1 h light; 1.4 ± 0.6 h deep; 1.6 ± 0.7 h rapid eye movement) at baseline. During night float, mean total sleep time was 4.5 ± 1.8 h (1.4-h decrease, 95% CI: 0.9 to 1.9, Cohen's d = -1.1, P < 0.001) with decreases in light (2.2 ± 1.1 h, 0.7-h decrease, 95% CI: 0.4 to 1.1, d = -1.0, P < 0.001), deep (1.1 ± 0.7 h, 0.3-h decrease, 95% CI: 0.1 to 0.4, d = -0.5, P = 0.005), and rapid eye movement sleep (1.2 ± 0.6 h, 0.4-h decrease, 95% CI: 0.3 to 0.6, d = -0.9, P < 0.001). Mean total sleep time during recovery was 5.4 ± 2.2 h, which did not differ significantly from baseline; however, deep (1.0 ± 0.6 h, 0.4-h decrease, 95% CI: 0.2 to 0.6, d = -0.6, P = 0.001 *, P = 0.001) and rapid eye movement sleep (1.2 ± 0.8 h, 0.4-h decrease, 95% CI: 0.2 to 0.6, d = -0.9, P < 0.001 P < 0.001) were significantly decreased. CONCLUSIONS: Electroencephalography monitoring demonstrates that sleep quantity is decreased during six consecutive night float shifts. A 3-day period of recovery is insufficient for restorative sleep (rapid eye movement and deep sleep) levels to return to baseline.

Influence of Sex and Body Language on Patient Perceptions of Anesthesiologists.

BACKGROUND: Patient perception of physician competence is important. The role of body language and physician sex on patient perceptions has not been investigated. The authors hypothesized that patients perceive anesthesiologists displaying confident body language as more competent and that patients would prefer male anesthesiologists. METHODS: Two hundred adult patients presenting to the Preanesthesia Evaluation and Testing Center at the University of Virginia Health System were recruited to participate using consecutive sampling. Patients viewed four 90-s videos in random order. Each video featured a male or female actor displaying confident, high-power poses or unconfident, low-power poses. Each actor recited the same script describing general anesthesia. Patients were randomized (100 per group) to view one of two sets of videos to account for any actor preferences. Participants ranked each actor anesthesiologist on perceived confidence, intelligence, and likelihood of choosing that anesthesiologist to care for their family member. Participants also chose the one actor anesthesiologist who seemed most like a leader. RESULTS: Two hundred patients watched the videos and completed the questionnaire. Actor anesthesiologists displaying confident, high-power body language had greater odds of being ranked as more confident (odds ratio, 2.27; 95% CI, 1.76 to 2.92; P < 0.0001), more intelligent (odds ratio, 1.69; 95% CI, 1.13 to 2.18; P < 0.0001), more likely chosen to care for one's family member (odds ratio, 2.34; 95% CI, 1.82 to 3.02; P < 0.0001), and more likely to be considered a leader (odds ratio, 2.60; 95% CI, 1.86 to 3.65; P < 0.0001). Actor anesthesiologist sex was not associated with ranking for any response measures. CONCLUSIONS: Patients perceive anesthesiologists displaying confident body language as more confident, more intelligent, more like a leader, and are more likely to choose that anesthesiologist to care for their family member. Differences in patient perceptions based on sex of the anesthesiologist were not detected.

Rotational thromboelastometry-guided transfusion during lumbar pedicle subtraction osteotomy for adult spinal deformity: preliminary findings from a matched cohort study.

OBJECTIVESignificant blood loss and coagulopathy are often encountered during adult spinal deformity (ASD) surgery, and the optimal intraoperative transfusion algorithm is debatable. Rotational thromboelastometry (ROTEM), a functional viscoelastometric method for real-time hemostasis testing, may allow early identification of coagulopathy and improve transfusion practices. The objective of this study was to investigate the effect of ROTEM-guided blood product management on perioperative blood loss and transfusion requirements in ASD patients undergoing correction with pedicle subtraction osteotomy (PSO).METHODSThe authors retrospectively reviewed patients with ASD who underwent single-level lumbar PSO at the University of Virginia Health System. All patients who received ROTEM-guided blood product transfusion between 2015 and 2017 were matched in a 1:1 ratio to a historical cohort treated using conventional laboratory testing (control group). Co-primary outcomes were intraoperative estimated blood loss (EBL) and total blood product transfusion volume. Secondary outcomes were perioperative transfusion requirements and postoperative subfascial drain output.RESULTSThe matched groups (ROTEM and control) comprised 17 patients each. Comparison of matched group baseline characteristics demonstrated differences in female sex and total intraoperative dose of intravenous tranexamic acid (TXA). Although EBL was comparable between ROTEM versus control (3200.00 ± 2106.24 ml vs 3874.12 ± 2224.22 ml, p = 0.36), there was a small to medium effect size (Cohen's d = 0.31) on EBL reduction with ROTEM. The ROTEM group had less total blood product transfusion volume (1624.18 ± 1774.79 ml vs 2810.88 ± 1847.46 ml, p = 0.02), and the effect size was medium to large (Cohen's d = 0.66). This difference was no longer significant after adjusting for TXA (ß = -0.18, 95% confidence interval [CI] -1995.78 to 671.64, p = 0.32). More cryoprecipitate and less fresh frozen plasma (FFP) were transfused in the ROTEM group patients (cryoprecipitate units: 1.24 ± 1.20 vs 0.53 ± 1.01, p = 0.03; FFP volume: 119.76 ± 230.82 ml vs 673.06 ± 627.08 ml, p < 0.01), and this remained significant after adjusting for TXA (cryoprecipitate units: ß = 0.39, 95% CI 0.05 to 1.73, p = 0.04; FFP volume: ß = -0.41, 95% CI -772.55 to -76.30, p = 0.02). Drain output was lower in the ROTEM group and remained significant after adjusting for TXA.CONCLUSIONSFor ASD patients treated using lumbar PSO, more cryoprecipitate and less FFP were transfused in the ROTEM group compared to the control group. These preliminary findings suggest ROTEM-guided therapy may allow early identification of hypofibrinogenemia, and aggressive management of this may reduce blood loss and total blood product transfusion volume. Additional prospective studies of larger cohorts are warranted to identify the appropriate subset of ASD patients who may benefit from intraoperative ROTEM analysis.

Generative retrieval results in positive academic emotions and long-term retention of cardiovascular anatomy using transthoracic echocardiography.

With increasing medical knowledge, procedural, and diagnostic skills to learn, it is vital for educators to make the limited amount of teaching time available to students effective and efficient. Generative retrieval is an effective and efficient learning tool, improving long-term retention through the practice of retrieval from memory. Forty medical students were randomized to learn normal cardiovascular anatomy using transthoracic echocardiography video clips in a generative retrieval (GR) or standard practice (SP) group. GR participants were required to verbally identify each unlabeled cardiovascular structure after viewing the video. After answering, participants viewed the correctly labeled video. SP participants viewed the same video clips labeled with the correct cardiovascular structure for the same amount of total time without verbally generating an answer. All participants were tested for intermediate (1-wk), late (1-mo), and long-term (6- to 9-mo) retention of cardiovascular anatomy. Additionally, a three-question survey was incorporated to assess perceptions of the learning method. There was no difference in pretest scores. The GR group demonstrated a trend toward improvement in recall at 1 wk [GR = 74.3 (SD 12.3); SP = 65.4 (SD 16.7); P = 0.10] and 1 mo [GR = 69.9 (SD15.6); SP = 64.3 (SD 15.4); P = 0.33]. At the 6- to 9-mo time point, there was a statistically significant difference in scores [GR = 74.3 (SD 9.9); SP = 65.0 (SD 14.1); P = 0.042]. At nearly every time point, learners had a statistically significantly higher perception of effectiveness, enjoyment, and satisfaction with GR. In addition to improved recall, GR is associated with increased perceptions of effectiveness, enjoyment, and satisfaction, which may lead to increased engagement, time spent studying, and improved retention.

Incidence and Risk Factors for Chronic Postoperative Opioid Use After Major Spine Surgery: A Cross-Sectional Study With Longitudinal Outcome.

BACKGROUND: Chronic opioid use is a significant public health concern. Surgery is a risk factor for developing chronic opioid use. Patients undergoing major spine surgery frequently are prescribed opioids preoperatively and may be at risk for chronic opioid use postoperatively. The aim of this study was to investigate the incidence of and perioperative risk factors associated with chronic opioid use after major spine surgery. METHODS: The records of patients who underwent elective major spine surgery at the University of Virginia between March 2011 and February 2016 were retrospectively reviewed. The primary outcome was chronic opioid use through 12 months postoperatively. Demographic data, medical comorbidities, preoperative pain scores, and medication use including daily morphine-equivalent (ME) dose, intraoperative use of lidocaine and ketamine, estimated blood loss, postoperative pain scores and medication use, and postoperative opioid use were collected. Logistic regression models were used to examine factors associated with chronic opioid use. RESULTS: Of 1477 patient records reviewed, 412 patients (27.9%) were opioid naive and 1065 patients (72.3%) used opioids before surgery. Opioid data were available for 1325 patients, while 152 patients were lost to 12-month follow-up and were excluded. Of 958 preoperative opioid users, 498 (52.0%) remained chronic users through 12 months. There was a decrease in opioid dosage (mg ME) from preoperative to 12 months postoperatively with a mean difference of -14.7 mg ME (standard deviation, 1.57; 95% confidence interval [CI], -17.8 to -11.7). Among 367 previously opioid-naive patients, 67 (18.3%) became chronic opioid users. Factors associated with chronic opioid use were examined using logistic regression models. Preoperative opioid users were nearly 4 times more likely to be chronic opioid users through 12 months than were opioid-naive patients (odds ratio, 3.95; 95% CI, 2.51-6.33; P < .001). Mean postoperative pain score (0-10) was associated with increased odds of chronic opioid use (odds ratio for a 1 unit increase in pain score 1.25, 95% CI, 1.13-1.38; P < .001). Use of intravenous ketamine or lidocaine was not associated with chronic opioid use through 12 months. CONCLUSIONS: Greater than 70% of patients presenting for major spine surgery used opioids preoperatively. Preoperative opioid use and higher postoperative pain scores were associated with chronic opioid use through 12 months. Use of ketamine and lidocaine did not decrease the risk for chronic opioid use. Surveillance of patients for these factors may identify those at highest risk for chronic opioid use and target them for intervention and reduction strategies.

Post-Craniotomy Pain Management: Beyond Opioids.

Craniotomy pain may be severe and is often undertreated. Pain management following craniotomy is a balancing act of achieving adequate analgesia but avoiding sedation, respiratory depression, hypercapnia, nausea and vomiting, and hypertension. Opioids are a first-line analgesic therapy; however, concern that opioid-related adverse effects (sedation, respiratory depression) may interfere with neurologic assessment and increase intracranial pressure has limited use of these drugs for intracranial surgery. Non-opioid analgesics avoid these effects and may be useful as part of a multimodal regimen for post-craniotomy pain. Regional scalp blocks, paracetamol, and non-steroidal anti-inflammatory drugs are beneficial in the early post-operative period. Recent studies suggest a role for novel analgesics: dexmedetomidine, gabapentinoids, and ketamine, though additional studies are necessary.

Variability in Intraoperative Opioid and Nonopioid Utilization During Intracranial Surgery: A Multicenter, Retrospective Cohort Study.

BACKGROUND: Key goals during intracranial surgery are to facilitate rapid emergence and extubation for early neurologic evaluation. Longer-acting opioids are often avoided or administered at subtherapeutic doses due to their perceived risk of sedation and delayed emergence. However, inadequate analgesia and increased postoperative pain are common after intracranial surgery. In this multicenter study, we describe variability in opioid and nonopioid administration patterns in patients undergoing intracranial surgery. METHODS: This was a multicenter, retrospective observational cohort study using the Multicenter Perioperative Outcomes Group database. Opioid and nonopioid practice patterns in 31,217 cases undergoing intracranial surgery across 11 institutions in the United States are described. RESULTS: Across all 11 institutions, total median [interquartile range] oral morphine equivalents, normalized to weight and anesthesia duration was 0.17 (0.08 to 0.3) mg.kg.min-1. There was a 7-fold difference in oral morphine equivalents between the lowest (0.05 [0.02 to 0.13] mg.kg.min-1) and highest (0.36 [0.18 to 0.54] mg.kg.min-1) prescribing institutions. Patients undergoing supratentorial surgery had higher normalized oral morphine equivalents compared with those having infratentorial surgery [0.17 [0.08-0.31] vs. 0.15 [0.07-0.27] mg/kg/min-1; P<0.001); however, this difference is clinically small. Nonopioid analgesics were not administered in 20% to 96.8% of cases across institutions. CONCLUSION: This study found wide variability for both opioid and nonopioid utilization at an institutional level. Future work on practitioner-level opioid and nonopioid use and its impact on outcomes after intracranial surgery should be conducted.

The relationship between the area of peripherally-derived pressure volume loops and systemic vascular resistance.

Arterial and photoplethysmographic (PPG) waveforms have been utilized to non-invasively estimate stroke volume from the pulse contour. The ability of these pulse contour devices to accurately predict stroke volume is degraded when afterload changes significantly. There is a need for a non-invasive device capable of identifying when vascular tone has changed. Shelley et al. previously described a qualitative relationship between peripheral pressure volume (PV) loops (in which pressure waveforms from an intra-arterial catheter are combined with volume waveforms from the PPG waveform) and changes in vascular tone. The purpose of this study was to quantitatively compare changes in the area of peripheral PV loops with changes in systemic vascular resistance (SVR) in a patient population undergoing major surgery. Physiologic data from ten patients undergoing liver transplantation was extracted from a hemodynamic database. A peak detection algorithm was applied to both the arterial and PPG waveforms, which were manually aligned so that the troughs occurred at identical time points. PV loop area (PVA) for each heartbeat was calculated and median PVA was recorded for each minute. PVA for each patient was indexed to the average value for the first 5 min (because PPG amplitude has no standard and is not comparable between patients) and compared to indexed SVR at all points for which SVR was available. SVR and PVA were plotted as a function of time and outliers (3.1 %) removed. The Pearson correlation coefficient describing the relationship between PVAi and SVRi was 0.67 (1,728 min of data, p = 0.0020, sign test over 10 patients) and between MAP and SVR was 0.71. There was no meaningful correlation between ΔSVR and either ΔPVA or ΔMAP (based on minute-to-minute changes). Indexed values of PVA are correlated with indexed values of SVR and may serve as a useful monitor for changes in afterload but in their present form do not offer added value above the measurement of MAP. Incorporation of different (e.g. finger, forehead) and redundant (e.g. bilateral) sites may significantly improve the accuracy of this technique.

Anesthesia for transsphenoidal pituitary surgery.

PURPOSE OF REVIEW: Pituitary tumors are commonly encountered in clinical practice. Patients with functioning adenomas frequently present with symptoms of hormone excess, whereas those with nonfunctioning adenomas often present later and have symptoms resulting from mass effect of the tumor. This article examines recent advancements in the preoperative assessment and anesthetic management of patients undergoing transsphenoidal pituitary surgery. RECENT FINDINGS: Endoscopic guidance has improved tumor visualization while minimizing the risk of nasal and dental complications and septal perforation. Computer-assisted navigation and intraoperative MRI has further improved surgical outcomes. Airway management may be particularly challenging in patients with acromegaly or Cushing's disease. Both intravenous and volatile agents can be used for anesthetic maintenance. Although pituitary surgery can be intensely stimulating and associated with intraoperative hypertension, most patients require little postoperative analgesia. Postoperative diabetes insipidus is common after pituitary surgery and is typically self-limited. Some patients will require treatment with desmopressin and it is important to avoid 'overshoot' iatrogenic syndrome of inappropriate antidiuretic hormone SIADH and hyponatremia in these patients. CONCLUSION: Anesthetic management for pituitary surgery requires thorough preanesthetic assessment of hormonal function and intraoperative management to facilitate surgical exposure while providing hemodynamic stability and allowing for rapid emergence.