The impact of hindsight bias on the diagnosis of perioperative events by anesthesia providers: A multicenter randomized crossover study.

STUDY OBJECTIVE: Hindsight bias is the tendency to overestimate the predictability of an event after it has already occurred. We aimed to evaluate whether hindsight bias influences the retrospective interpretation of clinical scenarios in the field of anesthesiology, which relies on clinicians making rapid decisions in the setting of perioperative adverse events. DESIGN: Two clinical scenarios were developed (intraoperative hypotension and intraoperative hypoxia) with 3 potential diagnoses for each. Participants completed a crossover study reviewing one case without being informed of the supposed ultimate diagnosis (i.e., no 'anchor' diagnosis), referred to as their foresight case, and the other as a hindsight case wherein they were informed in the leading sentence of the scenario that 1 of the 3 conditions provided was the ultimate diagnosis (i.e., the diagnosis the participant might 'anchor' to if given this information at the start). Participants were randomly assigned to (1) which scenario (hypotension or hypoxia) was presented as the initial foresight case and (2) which of the 3 potential diagnoses for the second case (the hindsight case, which defaulted to whichever case the participant was not assigned for the first case) was presented as the ultimate diagnosis in the leading sentence in a 2 (scenario order) x 3 (hindsight case anchor) between-subjects factorial design (6 possible randomization assignments). SETTING: Two academic medical centers. PARTICIPANTS: Faculty, fellow, and resident anesthesiologists and certified nurse anesthetists (CRNAs). INTERVENTIONS: None. MEASUREMENTS: After reading each clinical scenario, participants were asked to rate the probability (%) of each of three potential diagnoses to have caused the hypotension or hypoxia. Compositional data analysis (CoDA) was used to compare whether diagnosis probabilities differ between the hindsight and the foresight case. MAIN RESULTS: 113 participants completed the study. 59 participants (52%) were resident anesthesiologists. Participants randomized to the hypotension scenario as a hindsight case were 2.82 times more likely to assign higher probability to the pulmonary embolus diagnosis if provided as an anchor (95% CI, 1.35-5.90; P = 0.006) and twice as likely to assign higher probability to the myocardial infarction diagnosis if provided as an anchor (95% CI, 1.12-3.58; P = 0.020). Participants randomized to the hypoxia scenario as a hindsight case were 1.78 times more likely to assign higher probability to the mainstem bronchus intubation diagnosis if provided in the anchor statement (95% CI, 1.00-3.14; P = 0.048) and 3.72 times more likely to assign higher probability to the pulmonary edema diagnosis if provided as an anchor (95% CI, 1.88-7.35; P < 0.001). CONCLUSIONS: Hindsight bias influences the clinical diagnosis probabilities assigned by anesthesia providers. Clinicians should be educated on hindsight bias in perioperative medicine and be cognizant of the effect of hindsight bias when interpreting clinical outcomes.

Can Comprehensive Imaging Analysis with Analytic Morphomics and Geriatric Assessment Predict Serious Complications in Patients Undergoing Pancreatic Surgery?

We aimed to determine whether comprehensive imaging analysis with analytic morphomics (AM) enhances or replaces geriatric assessment (GA) in risk-stratifying pancreatic surgery patients. One hundred thirty-four pancreatic surgery patients were identified from a prospective cohort. Sixty-three patients in the cohort had preoperative CT scans in addition to comprehensive geriatric assessments. CT scans were processed using AM. Associations with National Surgical Quality Improvement Program (NSQIP) serious complications were evaluated using univariate analysis and robust elastic net modeling to obtain AUROC curves by adding AM and GA measures to our previously defined clinical base risk model (age, body mass index, American Society of Anesthesiologists classification, and Charlson comorbidity index). NSQIP serious complications were associated with low psoas Hounsfield units (HUs) (p = 0.002), low-density (0 to 30 HU) psoas area (p = 0.01), visceral fat HU (p ≤ 0.001), visceral fat area (p = 0.009), subcutaneous fat HU (p = 0.023), and total body area (p = 0.012) on univariate analysis. Elastic net models incorporating the base model with geriatric assessment and psoas HU (AUC = 0.751), and AM alone (AUC = 0.739) have greater predictive value than the base model alone (AUC = 0.601). The model utilizing AM and GA in combination had the highest predictive value (AUC = 0.841). When combined, AM and GA improve prediction of NSQIP serious complications compared to either technique alone. The additive nature of these two modalities suggests they likely capture unique aspects of a patient's fitness for surgery.

Using Analytic Morphomics to Understand Short-Term Convalescence after Radical Cystectomy.

Background: Data from the general surgery literature suggests that patient morphometric data obtained from preoperative imaging may help predict a patient's risk around surgery. Objectives: In this context, we evaluated for associations between psoas muscle area and short-term convalescence following radical cystectomy. Methods: After identifying patients who underwent radical cystectomy at our institution (2008 to 2013), we calculated their psoas muscle area from staging computed tomography scans using established analytic morphomic techniques. We then determined early recovery among patients with high and low psoas muscle area using the validated Convalescence and Recovery Evaluation (CARE) questionnaire-a 27-item survey, divided into four domains (activity, cognitive, gastrointestinal, and pain recovery). Finally, we assessed the relationship between psoas muscle area and changes in CARE scores with nested linear regression models. Results: Among the 86 men and among 31 women in our cohort, the median total psoas muscle area was 2,544 mm2 and 1,511 mm2, respectively (P <  0.001 for the comparison). While there was no association between psoas muscle area and recovery in men, women with higher (versus lower) total psoas muscle area had smaller decreases in their pain scores postoperatively and a quicker return to their baseline level (P = 0.05). Activity scores also approached baseline levels faster among women with higher psoas muscle area, although this finding did not reach statistical significance. Conclusions: Psoas muscle area is potentially an important preoperative predictor of recovery for women undergoingradical cystectomy. More broadly speaking, analytic morphomics may represent a novel approach to better understand perioperative risk.

Risk factors associated with lymphedema after lymph node dissection in melanoma patients.

BACKGROUND: Secondary lymphedema is a frequent complication after lymphadenectomy in melanoma patients, although few studies in melanoma adequately characterize risk factors for lymphedema, and of these, sample size is limited. This study aims to identify risk factors associated with the lymphedema after axillary lymph node dissection (ALND) and inguinal lymph node dissection (ILND) in a more robust cohort of melanoma patients. METHODS: We identified 269 ALND or ILND melanoma patients treated between 2008 and 2014. Demographic, clinical, and postoperative data were collected by review of the electronic medical record. Univariate and multivariate analysis were used to determine independent predictors of lymphedema. RESULTS: Fifty-six (20.8%) of the patients developed lymphedema after lymph node dissection with a median staging group of 3. ILND (odds ratio [OR] = 4.506, P < .001, 95% confidence interval [CI]: 2.289 to 8.869) and peripheral vascular disease (PVD; OR = 3.849, P = .020, 95% CI: 1.237 to 11.975) were significant predictors of lymphedema in multivariate analysis. Obese body mass index approached significance (OR = 1.802, P = .069, 95% CI: .955 to 3.399). CONCLUSIONS: PVD and ILND were the 2 factors associated with the highest risk of lymphedema in melanoma surgery with PVD increasing risk 2-fold in ILND patients and 3-fold in ALND patients. These findings may improve surgeon-patient communication of care goals and surgical risk assessment.

One-year postoperative resource utilization in sarcopenic patients.

BACKGROUND: It is well established that sarcopenic patients are at higher risk of postoperative complications and short-term health care utilization. Less well understood is how these patients fare over the long term after surviving the immediate postoperative period. We explored costs over the first postoperative year among sarcopenic patients. METHODS: We identified 1279 patients in the Michigan Surgical Quality Collaborative database who underwent inpatient elective surgery at a single institution from 2006-2011. Sarcopenia, defined by gender-stratified tertiles of lean psoas area, was determined from preoperative computed tomography scans using validated analytic morphomics. Data were analyzed to assess sarcopenia's relationship to costs, readmissions, discharge location, intensive care unit admissions, hospital length of stay, and mortality. Multivariate models were adjusted for patient demographics and surgical risk factors. RESULTS: Sarcopenia was independently associated with increased adjusted costs at 30, 90, and 180 but not 365 d. The difference in adjusted postsurgical costs between sarcopenic and nonsarcopenic patients was $16,455 at 30 d and $14,093 at 1 y. Sarcopenic patients were more likely to be discharged somewhere other than home (P < 0.001). Sarcopenia was not an independent predictor of increased readmission rates in the postsurgical year. CONCLUSIONS: The effects of sarcopenia on health care costs are concentrated in the immediate postoperative period. It may be appropriate to allocate additional resources to sarcopenic patients in the perioperative setting to reduce the incidence of negative postoperative outcomes.

Quality of life in liver transplant candidates: frailty is a better indicator than severity of liver disease.

BACKGROUND: In an effort to understand the diminished quality of life (QoL) exhibited by patients with end-stage liver disease (ESLD), we studied the association of frailty and severity of liver disease with quality of life in this patient population. METHODS: In a prospective, single-center cohort study (N=487), we assessed frailty and QoL in patients with ESLD referred for liver transplant. Frailty was measured on a scale from 0 to 5 by grip strength, gait speed, exhaustion, shrinkage, and physical activity, with scores of 3 or higher characterized as frail. Physical, mental, and combined overall quality of life scores ranging from 0 to 100 were assessed using Short Form 36. Pearson correlation and multiple linear regression were used to identify variables associated with QoL. RESULTS: Quality of life was notably low in the study cohort (mean: physical, 42.9±24.1; mental, 58.3±23.2). In multivariate analysis adjusted for demographic and clinical characteristics, frailty was significantly negative associated with physical (slope, -22.55, 95% confidence interval, -26.39 to -18.71; P<0.001) and mental QoL (slope, -17.59, 95% confidence interval, -21.47 to -13.71; P<0.001). Model for ESLD (MELD) was not associated with QoL. CONCLUSION: In ESLD patient referred for liver transplant, diminished QoL appears to be significantly negatively associated with frailty and not with severity of liver disease as measured MELD. With further study, if frailty is shown to be a remediable condition, targeted programs may help decrease frailty and improve quality of life in ESLD patients.

Electron attachment to Fe(CO)n (n = 0-5).

The rate constants of thermal electron attachment at 300 and 400 K to Fe(CO)(n) (n = 0-5) have been measured using a flowing afterglow Langmuir probe apparatus. The stable species Fe(CO)(5) was studied using the traditional method of monitoring electron depletion as a function of reaction time, and the remaining short-lived species were studied using the variable electron and neutral density attachment mass spectrometry (VENDAMS) technique. Attachment to Fe(CO)(5) is purely dissociative and about 20% efficient with a rate constant of (7.9 ± 1.4) × 10(-8) cm(3) s(-1) at 300 K and (8.8 ± 2) × 10(-8) cm(3) s(-1) at 400 K. The attachment rate constants decrease significantly as each CO ligand is removed, with Fe(CO)(n) (n = 4 to 1) attaching with efficiencies on the order of 10%, 1%, 0.1%, and 0.01% respectively. Under the conditions here, attachment to Fe(CO)(4) and Fe(CO)(3) are likely entirely dissociative, whereas attachment to Fe(CO)(2) and Fe(CO) are almost entirely associative. A statistical kinetic modeling approach is used to explain the strong dependence of the attachment rate constant on the number of ligands present in the neutral species through a combination of increasing autodetachment rates and decreasing exothermicities to dissociative attachment. The VENDAMS data also define the 300 K mutual neutralization rate constant of Fe(CO)(4)(-) + Ar(+) to be (5.0 ± 0.8) × 10(-8) cm(3) s(-1) with an upper limit to branching fraction of 0.5 to yield Fe(CO)(4), indicating that significant fragmentation to smaller Fe(CO)(n) occurs.

Electron attachment to 14 halogenated alkenes and alkanes, 300-600 K.

Thermal electron attachment to 14 alkenes and alkanes with bromine, fluorine, and iodine substituents has been studied over the temperature range 300-600 K using a flowing-afterglow Langmuir-probe apparatus. Rate coefficients and anion products are reported, most for the first time. Among these were 3 isomers of C(3)F(5)Br and the 2 isomers of C(3)F(7)I. Four dibromide compounds were studied, all of which yield Br(2)(-) product in addition to Br(-) product. The results are analyzed using a statistical kinetic modeling approach, which is able to reproduce both attachment rate coefficients and product branching ratios within experimental uncertainty. The kinetic modeling indicates that factor of 2 differences in attachment rate coefficients to the isomeric species can be explained by subtle variations in the potential surfaces.

Electron attachment to C7F14, thermal detachment from C7F14(-), the electron affinity of C7F14, and neutralization of C7F14(-) by Ar+.

Rate coefficients and branching fractions have been measured for electron attachment to perfluoromethylcyclohexane, C(7)F(14), along with thermal detachment rate coefficients for C(7)F(14)(-), from 300 to 630 K, using a flowing-afterglow Langmuir-probe apparatus. The attachment rate coefficient at room temperature is 4.5 ± 1.2 × 10(-8) cm(3) s(-1) and increases with temperature at a rate described by an activation energy of 50 ± 25 meV. Thermal electron detachment is negligible at room temperature, but measurable at 600 K and above, reaching 2300 ± 1300 s(-1) at 630 K. Analysis of the attachment-detachment equilibrium yields EA(C(7)F(14)) = 1.02 ± 0.06 eV, in agreement with the literature value while more than halving the uncertainty. Implications of the measurement for the electron affinity of SF(6) are discussed. The dominant product of electron attachment is the parent anion, but C(6)F(11)(-) and C(7)F(13)(-) are also observed at very low levels (<0.1%) at room temperature and increase in importance as the temperature is increased, reaching ~10% each at 630 K. In the course of this work we have also measured rate coefficients for the neutralization of C(7)F(14)(-) by Ar(+) at 300, 400, and 500 K: 4.8, 3.5, and 3.1 × 10(-8) cm(3) s(-1), respectively, with uncertainties of ±5 × 10(-9) cm(3) s(-1).

Dissociative electron attachment to C2F5 radicals.

Dissociative electron attachment to the reactive C(2)F(5) molecular radical has been investigated with two complimentary experimental methods; a single collision beam experiment and a new flowing afterglow Langmuir probe technique. The beam results show that F(-) is formed close to zero electron energy in dissociative electron attachment to C(2)F(5). The afterglow measurements also show that F(-) is formed in collisions between electrons and C(2)F(5) molecules with rate constants of 3.7 × 10(-9) cm(3) s(-1) to 4.7 × 10(-9) cm(3) s(-1) at temperatures of 300-600 K. The rate constant increases slowly with increasing temperature, but the rise observed is smaller than the experimental uncertainty of 35%.

Pressure and temperature dependence of dissociative and non-dissociative electron attachment to CF3: experiments and kinetic modeling.

The kinetics of electron attachment to CF(3) as a function of temperature (300-600 K) and pressure (0.75-2.5 Torr) were studied by variable electron and neutral density attachment mass spectrometry exploiting dissociative electron attachment to CF(3)Br as a radical source. Attachment occurs through competing dissociative (CF(3) + e(-) → CF(2) + F(-)) and non-dissociative channels (CF(3) + e(-) → CF(3)(-)). The rate constant of the dissociative channel increases strongly with temperature, while that of the non-dissociative channel decreases. The rate constant of the non-dissociative channel increases strongly with pressure, while that of the dissociative channel shows little dependence. The total rate constant of electron attachment increases with temperature and with pressure. The system is analyzed by kinetic modeling in terms of statistical theory in order to understand its properties and to extrapolate to conditions beyond those accessible in the experiment.

Temperature dependences of rate coefficients for electron catalyzed mutual neutralization.

The flowing afterglow technique of variable electron and neutral density attachment mass spectrometry (VENDAMS) has recently yielded evidence for a novel plasma charge loss process, electron catalyzed mutual neutralization (ECMN), i.e., A(+) + B(-) + e(-) → A + B + e(-). Here, rate constants for ECMN of two polyatomic species (POCl(3)(-) and POCl(2)(-)) and one diatomic species (Br(2)(-)) each with two monatomic cations (Ar(+)and Kr(+)) are measured using VENDAMS over the temperature range 300 K-500 K. All rate constants show a steep negative temperature dependence, consistent with that expected for a three body process involving two ions and an electron. No variation in rate constants as a function of the cation type is observed outside of uncertainty; however, rate constants of the polyatomic anions (~1 × 10(-18) cm(6) s(-1) at 300 K) are measurably higher than that for Br(2)(-) [(5.5 ± 2) × 10(-19) cm(6) s(-1) at 300 K].

Reactions of Ions with Ionic Liquid Vapors by Selected-Ion Flow Tube Mass Spectrometry.

Room-temperature ionic liquids exert vanishingly small vapor pressures under ambient conditions. Under reduced pressure, certain ionic liquids have demonstrated volatility, and they are thought to vaporize as intact cation-anion ion pairs. However, ion pair vapors are difficult to detect because their concentration is extremely low under these conditions. In this Letter, we report the products of reacting ions such as NO(+), NH4(+), NO3(-), and O2(-) with vaporized aprotic ionic liquids in their intact ion pair form. Ion pair fragmentation to the cation or anion as well as ion exchange and ion addition processes are observed by selected-ion flow tube mass spectrometry. Free energies of the reactions involving 1-ethyl-3-methylimidazolium bis-trifluoromethylsulfonylimide determined by ab initio quantum mechanical calculations indicate that ion exchange or ion addition are energetically more favorable than charge-transfer processes, whereas charge-transfer processes can be important in reactions involving 1-butyl-3-methylimidazolium dicyanamide.

Electron attachment to propargyl chloride, 305-540 K.

Electron attachment to propargyl chloride (HC≡C-CH(2)Cl) was studied in a flowing-afterglow Langmuir-probe apparatus from 305 to 540 K. The sole ion product in this temperature range is Cl(-). Electron attachment is very inefficient, requiring correction for a competing process of electron recombination with molecular cations produced in reaction between Ar(+) and propargyl chloride and subsequent ion-molecule reactions. The electron attachment rate coefficient was measured to be 1.6×10(-10)cm(3) s(-1) at 305 K and increased to 1.1×10(-9)cm(3) s(-1) at 540 K.

Electron attachment to sulfur oxyhalides: SOF2, SOCl2, SO2F2, SO2Cl2, and SO2FCl attachment rate coefficients, 300-900 K.

Electron attachment to SOF(2), SOCl(2), SO(2)F(2), SO(2)FCl, and SO(2)Cl(2) was studied with two flowing-afterglow Langmuir-probe apparatuses over the temperature range 300-900 K. Attachment rate coefficients at 300 K are k(a) = 2.6+/-0.8x10(-10)(SOF(2)), 1.8+/-0.5x10(-8)(SOCl(2)), 4.8+/-0.7x10(-10)(SO(2)F(2)), 2.4+/-0.7x10(-9)(SO(2)Cl(2)), and 2.0+/-0.6x10(-7) cm(3) s(-1)(SO(2)FCl). Arrhenius plots of the data imply activation energies of 56+/-22 meV(SOF(2)), 92+/-40(SO(2)F(2)), 44+/-22 meV(SOCl(2)), and 29+/-15 meV(SO(2)Cl(2)). The rate coefficients for SO(2)FCl decrease slightly with temperature, commensurate with the decrease in the capture rate coefficient. Electron attachment to SOF(2) and SO(2)F(2) is nondissociative, while reaction with SOCl(2), SO(2)FCl, and SO(2)Cl(2) is dissociative. Dissociative attachment is dominated by channels arising from S-Cl bond cleavage but also includes a minor channel forming a dihalide product ion. Branching fraction data are reported for the dissociative attachment channels.

Experimental and modeling study of thermal rate coefficients and cross sections for electron attachment to C(60).

Thermal electron attachment to C(60) has been studied by relative rate measurements in a flowing afterglow Langmuir probe apparatus. The rate coefficients of the attachment k(1) are shown to be close to 10(-6) cm(3) s(-1) with a small negative temperature coefficient. These results supersede measurements from the 1990s which led to much smaller values of k(1) with a large positive temperature coefficient suggesting an activation barrier. Theoretical modeling of k(1) in terms of generalized Vogt-Wannier capture theory shows that k(1) now looks more consistent with measurements of absolute attachment cross sections sigma(at) than before. The comparison of capture theory and experimental rate or cross section data leads to empirical correction factors, accounting for "intramolecular vibrational relaxation" or "electron-phonon coupling," which reduce k(1) below the capture results and which, on a partial wave-selected level, decrease with increasing electron energy.

Electron attachment to chlorine azide at 298 and 400 K.

Electron attachment to chlorine azide (ClN(3)) was studied using a flowing-afterglow Langmuir-probe apparatus. Electron attachment rates were measured to be 3.5x10(-8) and 4.5x10(-8) cm(3) s(-1) at 298 and 400 K, respectively, with an estimated 35% absolute accuracy. Cl(-) was the sole ion product of the attachment reaction; weak ion signals were observed for other anions and attributed to impurities and secondary ion-molecule reactions. Assuming a relative uncertainty of +/-10% for these data, an activation energy for the attachment reaction may be given as 24+/-10 meV.

Electron attachment to halomethanes at high temperature: CH(2)Cl(2), CF(2)Cl(2), CH(3)Cl, and CF(3)Cl attachment rate constants up to 1100 K.

We have used a high-temperature flowing-afterglow Langmuir-probe apparatus to measure rate constants for electron attachment to halomethanes which attach electrons very inefficiently at room temperature, yielding Cl(-) ion product. We studied CH(2)Cl(2) (495-973 K), CF(2)Cl(2) (291-1105 K), and CF(3)Cl (524-1004 K) and include our recent measurement for CH(3)Cl (700-1100 K) in the discussion of the electron attachment results. The measured attachment rate constants show Arrhenius behavior in the temperature ranges examined, from which estimates of rate constants at 300 K may be made: CH(2)Cl(2) (1.8x10(-13) cm(3) s(-1)), CH(3)Cl (1.1x10(-17) cm(3) s(-1)), and CF(3)Cl (4.2x10(-14) cm(3) s(-1)), all of which are difficult to measure directly. In the case of CF(2)Cl(2), the room temperature rate constant was sufficiently large to be measured (1.6x10(-9) cm(3) s(-1)). The Arrhenius plots yield activation energies for the attachment reactions: 390+/-50 meV (CH(2)Cl(2)), 124+/-20 meV (CF(2)Cl(2)), 670+/-70 meV (CH(3)Cl), and 406+/-50 meV (CF(3)Cl). Comparisons are made with existing data where available. G3 calculations were carried out to obtain reaction energetics. They show that the parent anions of CH(2)Cl(2) CF(2)Cl(2), CH(3)Cl, and CF(3)Cl are stable, though CH(3)Cl(-) exists only as an electrostatically bound complex.

A new instrument for thermal electron attachment at high temperature: NF3 and CH3Cl attachment rate constants up to 1100 K.

A new high temperature flowing afterglow Langmuir probe (HT-FALP) apparatus is described. A movable Langmuir probe and a four-needle reactant gas inlet were fitted to an existing high temperature flowing afterglow apparatus. The instrument is suitable for study of electron attachment from 300-1200 K, the upper limit set to avoid softening of the quartz flow tube. We present results for two reactions over extended ranges: NF(3) (300-900 K) and CH(3)Cl (600-1100 K). Electron attachment rate constants for NF(3) had been measured earlier using our conventional FALP apparatus. Those measurements were repeated with the FALP and then extended to 900 K with the HT-FALP. CH(3)Cl attaches electrons too weakly to study with the low temperature FALP but reaches a value of approximately 10(-9) cm(3) s(-1) at 1100 K. F(-) is produced in NF(3) attachment at all temperatures and Cl(-) in CH(3)Cl attachment, as determined by a quadrupole mass spectrometer at the end of the flow tube. Future modifications to increase the plasma density should allow study of electron-ion recombination at high temperatures.