Preoperative Risk and the Association between Hypotension and Postoperative Acute Kidney Injury.

BACKGROUND: Despite the significant healthcare impact of acute kidney injury, little is known regarding prevention. Single-center data have implicated hypotension in developing postoperative acute kidney injury. The generalizability of this finding and the interaction between hypotension and baseline patient disease burden remain unknown. The authors sought to determine whether the association between intraoperative hypotension and acute kidney injury varies by preoperative risk. METHODS: Major noncardiac surgical procedures performed on adult patients across eight hospitals between 2008 and 2015 were reviewed. Derivation and validation cohorts were used, and cases were stratified into preoperative risk quartiles based upon comorbidities and surgical procedure. After preoperative risk stratification, associations between intraoperative hypotension and acute kidney injury were analyzed. Hypotension was defined as the lowest mean arterial pressure range achieved for more than 10 min; ranges were defined as absolute (mmHg) or relative (percentage of decrease from baseline). RESULTS: Among 138,021 cases reviewed, 12,431 (9.0%) developed postoperative acute kidney injury. Major risk factors included anemia, estimated glomerular filtration rate, surgery type, American Society of Anesthesiologists Physical Status, and expected anesthesia duration. Using such factors and others for risk stratification, patients with low baseline risk demonstrated no associations between intraoperative hypotension and acute kidney injury. Patients with medium risk demonstrated associations between severe-range intraoperative hypotension (mean arterial pressure less than 50 mmHg) and acute kidney injury (adjusted odds ratio, 2.62; 95% CI, 1.65 to 4.16 in validation cohort). In patients with the highest risk, mild hypotension ranges (mean arterial pressure 55 to 59 mmHg) were associated with acute kidney injury (adjusted odds ratio, 1.34; 95% CI, 1.16 to 1.56). Compared with absolute hypotension, relative hypotension demonstrated weak associations with acute kidney injury not replicable in the validation cohort. CONCLUSIONS: Adult patients undergoing noncardiac surgery demonstrate varying associations with distinct levels of hypotension when stratified by preoperative risk factors. Specific levels of absolute hypotension, but not relative hypotension, are an important independent risk factor for acute kidney injury.

Taxane modulation of anesthetic sensitivity in surgery for nonmetastatic breast cancer.

STUDY OBJECTIVE AND DESIGN: The mechanism of action of commonly used general anesthetics is largely unknown. One hypothesized mechanism is through modulation of microtubule stability. Taxanes, a subset of chemotherapeutic drugs known to alter microtubule stability and commonly used to treat breast cancer, offer a natural experiment to test our hypothesis that patients exposed to taxanes prior to surgery, as compared to after surgery, would have a partial resistance to general anesthetics. SETTING, PATIENTS, AND MEASUREMENTS: The anesthetic record of adult women with nonmetastatic breast cancer was used to obtain changes in heart rate and blood pressure surrounding incision, and the amount of inhaled anesthetic agent, induction, and rescue drugs administered. MAIN RESULTS: Change in blood pressure in response to incision was significantly higher in the neoadjuvant group (P = .03), whereas change in heart rate was not (P = .53). A greater amount of morphine was administered in the neoadjuvant group (26.3 vs 15.5 mg, P = .02), although not a higher concentration of inhaled anesthetics (P = .15). CONCLUSION: These results suggest that the alteration of microtubule stability is one of a number of mechanisms of inhaled anesthetics.

Anesthesia information management system implementation: a practical guide.

Anesthesia Information Management Systems (AIMS) display and archive perioperative physiological data and patient information. Although currently in limited use, the potential benefits of an AIMS with regard to enhancement of patient safety, clinical effectiveness and quality improvement, charge capture and professional fee billing, regulatory compliance, and anesthesia outcomes research are great. The processes and precautions appropriate for AIMS selection, installation, and implementation are complex, however, and have been learned at each site by trial and error. This collaborative effort summarizes essential considerations for successful AIMS implementation, including product evaluation, assessment of information technology needs, resource availability, leadership roles, and training.

Acute circulatory actions of intravenous amiodarone loading in cardiac surgical patients.

BACKGROUND: The duration, severity, and cause of hypotension after intravenous amiodarone has not been well characterized in anesthetized cardiac surgical patients. Because amiodarone is tolerated in patients with advanced cardiac disease, we hypothesized that left ventricular systolic performance is preserved despite hypotension during amiodarone loading. METHODS: In a prospective double-blind trial, 30 patients undergoing coronary artery bypass graft (CABG) surgery were randomly assigned to receive intravenous amiodarone (n = 15) or placebo (n = 15). Cardiac output (CO), mixed venous oxygen saturation (SVO), arterial blood pressure (systolic blood pressure [SBP], diastolic blood pressure [DBP], mean arterial pressure [MAP]), pulmonary artery pressure, and central venous pressure (CVP) were recorded. Transesophageal echocardiographic left ventricular end-diastolic area (EDA), end-systolic area (ESA), fractional area change (FAC), and end-systolic wall stress (ESWS) were measured every 5 minutes. RESULTS: Mean arterial pressure, SBP, and DBP decreased over time after drug administration in both groups (p < 0.05). At 6 minutes, amiodarone decreased the MAP by 14 mm Hg (p = 0.004) and placebo decreased the MAP by 4 mm Hg. The change in MAP, SBP, and DBP between groups was statistically different for the first 15 minutes after drug administration. Hypotension requiring intervention occurred in 3 of 15 after amiodarone and 0 of 15 after placebo (p = 0.22). The mean heart rate was 11.5 beats per minute less after amiodarone (p < 0.02), but pulmonary artery pressure, CVP, SVO, and FAC were not different between groups. CONCLUSIONS: Intravenous amiodarone decreased heart rate and caused a significant, but transient decrease in arterial pressure in the first 15 minutes after administration. Left ventricular performance was maintained suggesting that selective arterial vasodilation was the primary cause of drug-induced hypotension.

Hypothermia and the approximate entropy of the electroencephalogram.

BACKGROUND: The electroencephalogram is commonly used to monitor the brain during hypothermic cardiopulmonary bypass and circulatory arrest. No quantitative relationship between the electroencephalogram and temperature has been elucidated, even though the qualitative changes are well known. This study was undertaken to define a dose-response relationship for hypothermia and the approximate entropy of the electroencephalogram. METHODS: The electroencephalogram was recorded during cooling and rewarming in 14 patients undergoing hypothermic cardiopulmonary bypass and circulatory arrest. Data were digitized at 128 Hz, and approximate entropy was calculated from 8-s intervals. The dose-response relationship was derived using sigmoidal curve-fitting techniques, and statistical analysis was performed using analysis of variance techniques. RESULTS: The approximate entropy of the electroencephalogram changed in a sigmoidal fashion during cooling and rewarming. The midpoint of the curve averaged 24.7 degrees C during cooling and 28 degrees C (not significant) during rewarming. The temperature corresponding to 5% entropy (T 0.05 ) was 18.7 degrees C. The temperature corresponding to 95% entropy (T 0.95 ) was 31.3 degrees C during cooling and 38.2 degrees C during rewarming ( P < 0.02). CONCLUSIONS: Approximate entropy is a suitable analysis technique to quantify the electroencephalographic changes that occur with cooling and rewarming. It demonstrates a delay in recovery that is of the same magnitude as that seen with conventional interpretation of the analog electroencephalogram and extends these observations over a greater range of temperatures.

Near-infrared spectroscopy cerebral oxygen saturation thresholds for hypoxia-ischemia in piglets.

Detection of cerebral hypoxia-ischemia remains problematic in neonates. Near-infrared spectroscopy, a noninvasive bedside technology has potential, although thresholds for cerebral hypoxia-ischemia have not been defined. This study determined hypoxic-ischemic thresholds for cerebral oxygen saturation (SCO2) in terms of EEG, brain ATP, and lactate concentrations, and compared these values with CBF and sagittal sinus oxygen saturation (SVO2). Sixty anesthetized piglets were equipped with near-infrared spectroscopy, EEG, laser-Doppler flowmetry, and a sagittal sinus catheter. After baseline, SCO2 levels of less than 20%, 20% to 29%, 30% to 39%, 40% to 49%, 50% to 59%, 60% to 79%, or 80% or greater were recorded for 30 minutes of normoxic normocapnia, hypercapnic hyperoxia, or bilateral carotid occlusion with or without arterial hypoxia. Brain ATP and lactate concentrations were measured biochemically. Logistic and linear regression determined the SCO2, CBF, and SVO2 thresholds for abnormal EEG, ATP, and lactate findings. Baseline SCO2 was 68 + 5%. The SCO2 thresholds for increased lactate, minor and major EEG change, and decreased ATP were 44 +/- 1%, 42 +/- 5%, 37 +/- 1%, and 33 +/- 1%. The SCO2 correlated linearly with SVO2 (r = 0.98) and CBF (r = 0.89), with corresponding SVO2 thresholds of 23%, 20%, 13%, and 8%, and CBF thresholds (% baseline) of 56%, 52%, 42%, and 36%. Thus, cerebral hypoxia-ischemia near-infrared spectroscopy thresholds for functional impairment are SCO2 33% to 44%, a range that is well below baseline SCO2 of 68%, suggesting a buffer between normal and dysfunction that also exists for CBF and SVO2.