Continuous Glucose Monitoring Using the Dexcom G6 in Cardiac Surgery During the Postoperative Period.

OBJECTIVE: Cardiac surgery is associated with hyperglycemia, which in turn is associated with adverse postsurgical outcomes such as wound infections, acute renal failure, and mortality. This pilot study seeks to determine if Dexcom G6Pro continuous glucose monitor (Dexcom G6Pro CGM) is accurate during the postoperative cardiac surgery period when fluid shifts, systemic inflammatory response syndrome, and vasoactive medications are frequently encountered, compared to standard glucose monitoring techniques. METHODS: This study received institutional review board approval. In this prospective study, correlation between clinical and Dexcom glucose readings was evaluated. Clinical glucose (blood gas, metabolic panel, and point of care) data set included 1428 readings from 29 patients, while the Dexcom G6Pro CGM data included 45 645 data points following placement to upper arm. Additionally, average clinical measurements of day and overnight temperatures and hemodynamics were evaluated. Clinical and Dexcom data were restricted to being at least 1 hour after prior clinical reading Matching Dexcom G6Pro CGM data were required within 5 minutes of clinical measure. Data included only if taken at least 2 hours after Dexcom G6Pro CGM insertion (warm-up time) and analyzed only following intensive care unit (ICU) admission. Finally, a data set excluding the first 24 hours after ICU admission was created to explore stability of the device. Patients remained on Dexcom G6Pro CGM until discharge or 10 days postoperatively. RESULTS: The population was 71% male, 14% with known diabetes; 66% required intravenous insulin infusion. The Clarke error grid plot of all measures post-ICU admission showed 53.5% in zone A, 45.9% in zone B, and 0.6% (n = 5) in zones D or E. The restricted dataset that excluded the first 24 hours post-ICU admission showed 55.9% in zone A, 43.9% in zone B, and 0.2% in zone D. Mean absolute relative difference between clinical and Dexcom G6Pro CGM measures was 20.6% and 21.6% in the entire post-ICU admission data set, and the data set excluding the first 24 hours after ICU admission, respectively. In the subanalysis of the 12 patients who did not have more than a 5-minute tap in the operating room, a consensus error grid, demonstrated that after ICU admission, percentage in zone A was 53.9%, zone B 45.4%, and zone C 0.7%. Similar percentages were obtained removing the first 24 hours post-ICU admission. These numbers are very similar to the entire cohort. A consensus error grid created post-ICU admission demonstrated: (zone A) 54%, (zone B) 45%, (zone C) 0.9%, and the following for the dataset created excluding the first 24 hours: (zone A) 56%, (zone B) 44%, (zone C) 0.4%, which demonstrated very close agreement with the original Clarke error grid. No adverse events were reported. CONCLUSIONS: Almost 100% of Dexcom G6Pro CGM and clinical data matching points fell within areas considered as giving clinically correct decisions (zone A) and clinically uncritical decisions (zone B). However, the relatively high mean absolute relative difference precludes its use for both monitoring and treatment in the clinical context. As technology evolves, interstitial glucose monitoring may become an important tool to limit iatrogenic anemia and mitigate glycemic fluctuations.

Value of Routine Troponin Measurement in Open Abdominal Aortic Aneurysm Repair.

BACKGROUND: Cardiovascular complications are a major cause of morbidity and mortality in the postoperative period after major vascular surgery. Depending on the study population, up to 25% of patients have troponin elevation after noncardiac surgery, yet many do not meet the diagnosis of myocardial infarction (MI). Although outcomes of routine troponin elevation in patients undergoing mixed major vascular surgery have been evaluated, this has not been studied exclusively in elective, open abdominal aortic aneurysm repair (oAAA), especially regarding perioperative and overall mortality. METHODS: We conducted a single-center, retrospective review of routine troponin surveillance for consecutive, oAAA from 2014 to 2019. A total of 319 patients were identified and analyzed for management patterns and interventions. The cohort was stratified into groups for comparison based on those in whom troponin was routinely checked (RC) as part of a care strategy during the study period, not routinely checked (NRC), elevated troponin (ET) >0.001 ng/mL, and not elevated. The median follow-up was 21.5 ± 23.8 months. Groups were compared on demographic data, cardiac comorbidities, 30-day and 3-year outcomes for MI and death using two-sample t-tests, Wilcoxon rank sum tests, Pearson chi-square tests, and Fisher exact tests when appropriate. RESULTS: Troponin was measured in 83.7% (267/319) of patients who underwent elective oAAA repair. Routine troponin checks were obtained in 79.9% (255/319) of patients. ET was identified in 16.5% of those with RC (42/255) and 4.7% of those with NRC (3/64). Of patients with ET, 37.8% (17/45) had a cardiology consultation, 4.4% (2/45) had a percutaneous coronary intervention (PCI), and 4.4% (2/45) had another cardiac intervention. All 4 patients undergoing PCI or other cardiac intervention had received routine troponin checks. Patients with ET were older (71.2 vs. 68.6; P = 0.04), more likely to receive intraoperative blood products (P = 0.003), had longer operative times (P = 0.011), higher length of stay (9 vs. 7 days; P < 0.01), and higher 30-day MI rate (3 vs. 0; P = 0.04). They had neither longer aortic clamp times nor worse preoperative cardiac function, and the proximal clamp position during oAAA repair did not impact troponin detection. Additionally, 3-year overall mortality was increased in patients who had ET but there was not a significant difference in 3-year mortality between groups receiving routine troponin checks versus not. CONCLUSIONS: ET, identified after elective oAAA repair, was associated with a higher risk of 30-day MI and lower overall survival. However, it was not demonstrated that routine assessment of troponin levels postoperatively leads to decreased 3-year mortality in this setting.

A nomogram to predict postoperative pulmonary complications after cardiothoracic surgery.

OBJECTIVE: The objective was to develop a novel scoring system that would be predictive of postoperative pulmonary complications in critically ill patients after cardiac and major vascular surgery. METHODS: A total of 17,433 postoperative patients after coronary artery bypass graft, valve, or thoracic aorta repair surgery admitted to the cardiovascular intensive care units at Cleveland Clinic Main Campus from 2009 to 2015. The primary outcome was the composite of postoperative pulmonary complications, including pneumonia, prolonged postoperative mechanical ventilation (>48 hours), or reintubation occurring during the hospital stay. Elastic net logistic regression was used on the training subset to build a prediction model that included perioperative predictors. Five-fold cross-validation was used to select an appropriate subset of the predictors. The predictive efficacy was assessed with calibration and discrimination statistics. Post hoc, of 13,353 adult patients, we tested the clinical usefulness of our risk prediction model on 12,956 patients who underwent surgery from 2015 to 2019. RESULTS: Postoperative pulmonary complications were observed in 1669 patients (9.6%). A prediction model that included baseline and demographic risk factors along with perioperative predictors had a C-statistic of 0.87 (95% confidence interval, 0.86-0.88), with a corrected Brier score of 0.06. Our prediction model maintains satisfactory discrimination (C-statistics of 0.87) and calibration (Brier score of 0.07) abilities when evaluated on an independent dataset of 12,843 recent adult patients who underwent cardiovascular surgery. CONCLUSIONS: A novel prediction nomogram accurately predicted postoperative pulmonary complications after major cardiac and vascular surgery. Intensivists may use these predictors to allow for proactive and preventative interventions in this patient population.

Intravenous acetaminophen analgesia after cardiac surgery: A randomized, blinded, controlled superiority trial.

BACKGROUND: Pain after cardiac surgery traditionally has been controlled by intravenous opioids and nonsteroidal antiinflammatory drugs. An intravenous analgesic with fewer adverse effects is needed. Therefore, we tested the primary hypothesis that intravenous acetaminophen is more effective than placebo for pain management, which was defined a priori as superior on either pain intensity score and/or opioid consumption and not worse on either. METHODS: In this single-center, double-blind trial, 147 patients having cardiac surgery via median sternotomy were randomized to receive either 1 g of intravenous acetaminophen (73 patients) every 6 hours for 24 hours or comparable placebo (74 patients) starting in the operating room after sternal closure. Cumulative opioid consumption (in morphine equivalents) and pain intensity scores (on a 0-10 Numeric Rating Scale) were measured at 4, 6, 8, 12, 16, 20, and 24 hours after surgery. We estimated ratio of mean opioid consumption by using multivariable linear regression (noninferiority delta = 1.15) and pain score difference by using repeated measures regression (noninferiority delta = 1). RESULTS: Acetaminophen was superior to placebo on mean pain intensity scores and noninferior on opioid consumption, with estimated difference in mean pain (95% confidence interval) of -0.90 (-1.39, -0.42), P < .001 (superior), and estimated ratio of means in opioid consumption (90% confidence interval) of 0.89 (0.73-1.10), P = .28 (noninferior; not superior). CONCLUSIONS: Intravenous acetaminophen reduced pain after cardiac surgery, but not opioid consumption. Intravenous acetaminophen can be an effective analgesic adjunct in patients recovering from median sternotomy.

Transdermal oxygen does not improve sternal wound oxygenation in patients recovering from cardiac surgery.

BACKGROUND: Sternal wound dehiscence and infection complicate 1% of cardiac surgeries. Tissue oxygen tension (PsqO(2)) is the primary determinant of surgical wound infection risk and is often critically low in surgical incisions. We tested the hypothesis that local transdermal delivery of oxygen improves oxygenation in sternotomy wounds after cardiac surgery. Our secondary hypothesis was that supplemental inspired oxygen improves sternal wound PsqO(2). METHODS: After undergoing cardiopulmonary bypass, 30 patients randomly received (1) 2 EpiFlo oxygen generators (Ogenix, Inc., Beachwood, OH) that provided oxygen at 6 mL/h into an occlusive wound dressing or (2) identical-appearing inactive generators. PsqO(2) and temperature were measured in the wound approximately 5 mm below the skin surface. PsqO(2) and arterial oxygen (Pao(2)) were measured 1 h after intensive care unit admission (Fio(2) = 60%) and on the first and second postoperative mornings at Fio(2) of both 30% and 50% in random order. RESULTS: Data from four patients were excluded for technical reasons. Patient characteristics were similar in each group, as were type of surgery and perioperative management. Increasing Fio(2) from 30% to 50% improved Pao(2) from 99 [84-116] to 149 [128-174] mm Hg (P < 0.001, mean [95% CI]) and sternal wound PsqO(2) from 23 [16-33] to 27 [19-38] mm Hg (P < 0.001). In contrast, local oxygen delivery did not improve tissue oxygenation: 24 [14-41] vs 25 [16-41] mm Hg (P = 0.88). CONCLUSIONS: Additional inspired oxygen improved Pao(2) and sternal wound PsqO(2) after bypass and may, consequently, reduce infection risk. However, oxygen insufflated locally into an occlusive dressing did not improve wound PsqO(2) and, therefore, does not appear to be useful clinically in cardiac surgery patients to reduce sternal wound infections.

An evaluation of a full-access underbody forced-air warming system during near-normothermic, on-pump cardiac surgery.

BACKGROUND: A new underbody forced-air warming system is available for use during cardiac surgery. We tested the hypothesis combining underbody forced-air warming with standard thermal management would maintain intraoperative core temperature and reduce core temperature after-drop (largest decrease in core temperature in the 60 min after bypass) in patients undergoing near-normothermic cardiopulmonary bypass (CPB). METHODS: Patients undergoing routine, nonemergent cardiac surgery were randomly assigned to routine thermal management (fluid warming and passive insulation, n = 30) or routine management supplemented by an active underbody forced-air system (n = 30; Arizant Healthcare Model 635, Eden Prairie, MN). Core body temperature was measured by bladder catheter at 15-min intervals during the perioperative period. Comparisons were made between groups for temperature before, during, and after CPB. RESULTS: Data from four patients were excluded for cause, leaving 29 patients in the routine management group and 27 patients in the forced-air group. Initial temperatures were similar, but temperatures in the forced-air group were higher than in the routine group at the start of CPB (36.3 degrees C +/- 0.6 degrees C vs 35.7 degrees C +/- 0.7 degrees C, P = 0.002). There were no differences between groups in the lowest temperatures during CPB (forced air, 35.5 degrees C +/- 1.5 degrees C vs routine, 35.3 degrees C +/- 1.3 degrees C, P = 0.67); the end of CPB (36.7 degrees C +/- 0.4 degrees C vs 36.6 degrees C +/- 0.4 degrees C, P > 0.99); or the temperature at departure from the operating room (36.5 degrees C +/- 0.4 degrees C vs 36.2 degrees C +/- 0.5 degrees C, P = 0.36). After-drop was 0.03 degrees C +/- 0.54 degrees C in patients randomized to underbody forced-air warming and 0.21 degrees C +/- 0.51 degrees C in those assigned to routine management (P = 0.20). CONCLUSIONS: Adding an underbody forced-air warming system to the near-normothermic thermal management protocol significantly increased pre-bypass temperature; however, it had no further clinically important effect on core temperature.

Perioperative thermoregulation and temperature monitoring.

Traditionally, hypothermia has been thought of and used perioperatively as a presumptive strategy to reduce cerebral and myocardial tissue sensitivity to ischemia. Evidence, however, is mounting that maintenance of perioperative normothermia is associated with improved outcomes in patients undergoing all types of surgery, even cardiac surgery. Ambient environmental temperature is sensed by free nerve endings in the dermal and epidermal layers of the skin, which are the axonal extensions of thermosensitive neurons found in the dorsal root ganglia. Free nerve endings in the skin, by means of transient receptor ion channels that are specifically thermosensitive, also may directly sense environmental temperature. This information is transmitted to the preoptic/anterior hypothalamic region of the brainstem, which coordinates efferent responses to abnormal temperature deviation. People have evolved a highly integrated thermoregulatory system that maintains core body temperature in a relatively narrow temperature range. This system, though, is impaired by the stress of regional and general anesthesia, and the added exposure that occurs during the surgical procedure. When combined, these factors can lead to unwanted thermal disturbances. In a cold operating room environment, hypothermia is the usual perioperative consequence; however, hyperthermia is more dangerous and demands immediate diagnosis. Intraoperative hypothermia usually develops in three phases. The first is a rapid decrease in core temperature following anesthetic induction, which mostly results from redistribution of heat from the core thermal compartment to the outer shell of the body. This is followed by a slower, linear reduction in the core temperature that may last several hours. Finally, a core temperature plateau is reached, after which core temperature remains virtually unchanged for the remainder of the procedure. The plateau can be passive or result from re-emergence of thermoregulatory control in patients becoming sufficiently hypothermic. Mild hypothermia in the perioperative period has been associated with adverse outcomes, including impaired drug metabolism, prolonged recovery from anesthesia, cardiac morbidity, coagulopathy, wound infections, and postoperative shivering. Perioperative temperature monitoring devices vary by transducer type and site monitored. More important than the specific device is the site of temperature monitoring. Sites that are accessible during surgery and give an accurate reflection of core temperature include esophageal, nasopharynx, bladder, and rectal sites. Core temperature also may be estimated reasonably using axillary temperature probes except under extreme thermal conditions. Rather than taking a passive approach to thermal management, anesthesiologists need to be proactive in monitoring patients in cold operating rooms and use available technology to prevent gross disturbances in the core temperature. Various methods are available to achieve this. Prewarming patients reduces redistribution hypothermia and is an effective strategy for maintaining intraoperative normothermia. Additionally, forced-air warming and circulating water garments also have been shown to be effective. Heating intravenous fluids does not warm patients, but does prevent fluid-induced hypothermia in patients given large volumes of fluid. This article examined the evolutionary adaptations people possess to combat inadvertent hypothermia and hyperthermia. Because thermal disturbances are associated with severe consequences, the standard of care is to monitor temperature during general anesthesia and to maintain normothermia unless otherwise specifically indicated.

A new thermoregulation system for maintaining perioperative normothermia and attenuating myocardial injury in off-pump coronary artery bypass surgery.

BACKGROUND: Most patients undergoing coronary artery bypass surgery demonstrate perioperative mild-to-moderate hypothermia (<36 degrees C). Patients undergoing off-pump coronary artery bypass (OPCAB) grafting may become even more severely hypothermic for want of cardiopulmonary bypass rewarming. One consequence is increased circulating catecholamine levels that induce an elevated systemic vascular resistance (SVR), which causes a subsequent deterioration in cardiac output. MATERIALS AND METHODS: We assessed the ability of the Allon thermoregulatory (AT) system to maintain normothermia and its impact on hemodynamics and myocardial function in patients undergoing OPCAB surgery. In this study, the first 60 of 120 suitable patients were assigned to AT (n = 40) or routine thermal care (RTC) (n = 20). Core body temperature, cardiac index (CI), SVR, and cardiac-specific troponin I (cTnI) were analyzed perioperatively for patients in both groups. RESULTS: Core body temperature was significantly higher in the AT group (from 36.1 degrees C +/- 0.5 degrees C at induction of anesthesia to 37 degrees C +/- 0.5 degrees C during surgery) than in the RTC group (from 35.8 degrees C +/- 0.4 degrees C to 35.2 degrees C +/- 0.8 degrees C, respectively; P <.01). SVR was significantly lower, and CI was greater (at comparable time points), whereas cTnI levels in the AT group were lower than in the RTC group from the end of surgery until 24 hours postoperatively (7.4 +/- 17.7 g/L versus 31.9 +/- 47.4 g/L; P =.03). These findings indicate the possibility for less ischemic damage sustained intraoperatively in the AT group. CONCLUSIONS: Maintenance of perioperative normothermia (36.5 degrees C-37.5 degrees C) during OPCAB procedures can be efficiently achieved with the Allon thermoregulation system. The system was found to be superior to other routinely used methods of temperature maintenance. Benefits may include lowering afterload (as expressed by reduced SVR), an improved CI, and attenuation of myocardial injury (as assessed by cTnI levels).