IMPORTANCE Cardiac stress testing is often performed prior to noncardiac surgery, although trends in use of preoperative stress testing and the effect of testing on cardiovascular outcomes are currently unknown.OBJECTIVE To describe temporal trends and outcomes of preoperative cardiac stress testing from 2004 to 2017. DESIGN, SETTING, AND PARTICIPANTSCross-sectional study of patients undergoing elective total hip or total knee arthroplasty from 2004 to 2017. Trend analysis was conducted using Joinpoint and generalized estimating equation regression. The study searched IBM MarketScan Research Databases inpatient and outpatient health care claims for private insurers including supplemental Medicare coverage and included patients with a claim indicating an elective total hip or total knee arthroplasty from January 1, 2004, December 31, 2017.EXPOSURES Elective total hip or knee arthroplasty. MAIN OUTCOMES AND MEASURESTrend in yearly frequency of preoperative cardiac stress testing. RESULTSThe study cohort consisted of 801 396 elective total hip (27.9%; n = 246 168 of 801 396) and total knee (72.1%; 555 228 of 801 396) arthroplasty procedures, with a median age of 62 years (interquartile range, 57-70 years) and 58.1% women (n = 465 545 of 801 396). The overall rate of stress testing during the study period was 10.4% (n = 83 307 of 801 396). The rate of stress tests increased 0.65% (95% CI, 0.09-1.21; P = .03) annually from quarter (Q) 1 of 2004 until Q2 of 2006. A joinpoint was identified at Q3 of 2006 (95% CI, 2005 Q4 to 2007 Q4) when preoperative stress test use decreased by −0.71% (95% CI, −0.79% to 0.63%; P < .001) annually. A second joinpoint was identified at the Q4 of 2013 (95% CI, 2011 Q3 to 2015 Q3), when the decline in stress testing rates slowed to −0.40% (95% CI, −0.57% to −0.24%; P < .001) annually. The overall rate of myocardial infarction and cardiac arrest was 0.24% (n = 1677 of 686 067). Rates of myocardial infraction and cardiac arrest were not different in patients with at least 1 Revised Cardiac Risk Index condition who received a preoperative stress test and those who did not (0.60%; n = 221 of 36 554 vs 0.57%; n = 694 of 122 466; P = .51). CONCLUSIONS AND RELEVANCEThe frequency of preoperative stress testing declined annually from 2006 through 2017. Among patients with at least 1 Revised Cardiac Risk Index condition, no difference was observed in cardiovascular outcomes between patients who did and did not undergo preoperative testing.

Most animals, including reptiles, lower body temperature (T b ) under hypoxic conditions. Numerous physiological and behavioural traits significant to the regulation of T b are altered by hypoxia in ways that suggest an orchestrated adjustment of T b at a new and lower regulated level. We examined this matter in bearded dragons, Pogona vitticeps, a species of reptile that naturally exhibits open mouth gaping at high temperatures, presumably in order to promote evaporation and thus prevent or avoid further increases in T b . The threshold for the onset of gaping (assessed as the temperature at which lizards spent 50% of their time gaping) was reduced from 36.9°C in normoxia to 35.5°C at 10% and 34.3°C at 6% O 2 . The overall magnitude or degree of gaping, measured qualitatively, was more pronounced at lower temperatures in hypoxia. Females consistently had lower gaping threshold temperatures than did males, and this difference was retained throughout exposure to hypoxia. In addition to gaping, evaporative water loss from the cloaca may also play a significant role in temperature regulation, since the ambient temperature at which cloacal discharge occurred was also reduced significantly in hypoxia. The results reported herein strongly support the view that hypoxia reduces temperature set-point in lizards and that such changes are coordinated by specific behavioural thermoeffectors that modulate evaporative water loss and thus facilitate a high potential for controlling or modifying T b .

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BACKGROUND: Functional capacity assessment plays a core role in the preoperative evaluation. The Duke Activity Status Index (DASI) and the 6-minute walk test (6MWT) are 2 methods that have demonstrated the ability to evaluate functional capacity and predict perioperative outcomes. Smartphones offer a novel method to facilitate functional capacity assessment as they can easily administer a survey and accelerometers can track patient activity during a 6MWT. We developed a smartphone application to administer a 6MWT and DASI survey and performed a pilot study to evaluate the accuracy of a smartphone-based functional capacity tool in our Anesthesia and Perioperative Medicine Clinic. METHODS: Using the Apple ResearchKit software platform, we developed an application that administers a DASI survey and 6MWT on an iOS smartphone. The DASI was presented to the patient 1 question on the screen at a time and the application calculated the DASI score and estimated peak oxygen uptake (Vo 2). The 6MWT used the CMPedometer class from Apple’s core motion facility to retrieve accelerometer data collected from the device’s motion coprocessor to estimate steps walked. Smartphone estimated steps were compared to a research-grade pedometer using the intraclass correlation coefficient (ICC). Distance walked was directly measured during the 6MWT and we performed a multivariable linear regression with biometric variables to create a distance estimation algorithm to estimate distance walked from the number of steps recorded by the application. RESULTS: Seventy-eight patients were enrolled in the study and completed the protocol. Steps measured by the smartphone application as compared to the pedometer demonstrated moderate agreement with an ICC (95% CI) of 0.87 (0.79–0.92; P = .0001). The variables in the distance estimation algorithm included (β coefficient [slope], 95% CI) steps walked (0.43, 0.29–0.57; P < .001), stride length (0.38, 0.22–0.53; P < .001), age in years (−1.90, −3.06 to −0.75; P = .002), and body mass index (−2.59, −5.13 to −0.06; P = .045). The overall model fit was R 2 = 0.72, which indicates a moderate level of goodness of fit and explains 72% of the variation of distance walked during a 6MWT. CONCLUSIONS: Our pilot study demonstrated that a smartphone-based functional capacity assessment is feasible using the DASI and 6MWT. The DASI was easily completed by patients and the application clearly presented the results of the DASI to providers. Our application measured steps walked during a 6MWT moderately well in a preoperative patient population; however, future studies are needed to improve the smartphone application’s step-counting accuracy and distance estimation algorithm.