Acute Kidney Stress and Prevention of Acute Kidney Injury.

Critical care physicians continue to be challenged to recognize an environment that has the potential to result in acute kidney injury, with its associated short- and long-term consequences. The recent development of cell cycle arrest biomarkers that signal the potential development of acute kidney injury is part of an evolution in the molecular diagnosis and understanding of acute kidney injury. A preinjury phase that may lead to acute kidney injury has been described as "acute kidney stress." This concept has the potential to stimulate research and innovation that will lead to early implementation of measures to prevent or reverse acute kidney injury.

Validation of a Real-Time Minute-to-Minute Urine Output Monitor and the Feasibility of Its Clinical Use for Patients Undergoing Cardiac Surgery.

Acute kidney injury after cardiac surgery is associated with increased morbidity and mortality. Methods for measuring urine output in real time may better ensure renal perfusion perioperatively in contrast to the current standard of care where urine output is visually estimated after empiric epochs of time. In this study, we describe an accurate method for monitoring urine output continuously during cardiopulmonary bypass. This may provide a means for setting patient-specific targets for blood pressure and cardiopulmonary bypass flow as a potential strategy to reduce the risk for acute kidney injury.

Blood pressure excursions below the cerebral autoregulation threshold during cardiac surgery are associated with acute kidney injury.

OBJECTIVES: To determine whether mean arterial blood pressure excursions below the lower limit of cerebral blood flow autoregulation during cardiopulmonary bypass are associated with acute kidney injury after surgery. SETTING: Tertiary care medical center. PATIENTS: Four hundred ten patients undergoing cardiac surgery with cardiopulmonary bypass. DESIGN: Prospective observational study. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Autoregulation was monitored during cardiopulmonary bypass by calculating a continuous, moving Pearson's correlation coefficient between mean arterial blood pressure and processed near-infrared spectroscopy signals to generate the variable cerebral oximetry index. When mean arterial blood pressure is below the lower limit of autoregulation, cerebral oximetry index approaches 1, because cerebral blood flow is pressure passive. An identifiable lower limit of autoregulation was ascertained in 348 patients. Based on the RIFLE criteria (Risk, Injury, Failure, Loss of kidney function, End-stage renal disease), acute kidney injury developed within 7 days of surgery in 121 (34.8%) of these patients. Although the average mean arterial blood pressure during cardiopulmonary bypass did not differ, the mean arterial blood pressure at the limit of autoregulation and the duration and degree to which mean arterial blood pressure was below the autoregulation threshold (mm Hg × min/hr of cardiopulmonary bypass) were both higher in patients with acute kidney injury than in those without acute kidney injury. Excursions of mean arterial blood pressure below the lower limit of autoregulation (relative risk 1.02; 95% confidence interval 1.01 to 1.03; p < 0.0001) and diabetes (relative risk 1.78; 95% confidence interval 1.27 to 2.50; p = 0.001) were independently associated with for acute kidney injury. CONCLUSIONS: Excursions of mean arterial blood pressure below the limit of autoregulation and not absolute mean arterial blood pressure are independently associated with for acute kidney injury. Monitoring cerebral oximetry index may provide a novel method for precisely guiding mean arterial blood pressure targets during cardiopulmonary bypass.

State of the art: Proceedings of the American Association for Thoracic Surgery Enhanced Recovery After Cardiac Surgery Summit.

Despite the benefits established for multiple surgical specialties, enhanced recovery after surgery has been underused in cardiac surgery. A cardiac enhanced recovery after surgery summit was convened at the 102nd American Association for Thoracic Surgery annual meeting in May 2022 for experts to convey key enhanced recovery after surgery concepts, best practices, and applicable results for cardiac surgery. Topics included implementation of enhanced recovery after surgery, prehabilitation and nutrition, rigid sternal fixation, goal-directed therapy, and multimodal pain management.

Financial Impact of Acute Kidney Injury After Cardiac Operations in the United States.

BACKGROUND: Acute kidney injury (AKI) after major cardiac operations is a potentially avoidable complication associated with increased morbidity, death, and costly long-term treatment. The financial impact of AKI at the population level has not been well defined. We sought to determine the incremental index hospital cost associated with the development of AKI. METHODS: All patients undergoing coronary artery bypass grafting (CABG) or valve replacement operations, or both (clinical classification software codes 43 and 44), between 2008 and 2011 were identified from the Nationwide Inpatient Sample. AKI was identified using International Classification of Diseases, 9th Revision, Clinical Modification diagnosis codes (584.xx); patients with chronic renal failure were excluded. Mean total index hospitalization costs were compared between patients with and without AKI. RESULTS: At the population level, 1,078,036 individuals underwent major cardiac procedures from 2008 to 2011, with AKI developing in 105,648 (9.8%). Specifically, AKI developed in 8.0% of CABG, 11.4% of valve replacement, and 17.0% of CABG plus valve replacement patients (p < 0.001). Death was more common among patients with AKI vs those without (13.9% vs 1.3%, p < 0.001). Mean total index hospitalization cost was $77,178 for patients with AKI vs $38,820 for those without (p < 0.001). At the national level, the overall incremental annual index hospitalization cost associated with AKI was $1.01 billion. CONCLUSIONS: AKI developed in 1 in every 10 patients nationwide after a cardiac operation. Achieving a 10% reduction in AKI in this population would likely result in an annual savings of approximately $100,000,000 in index-hospital costs alone. Support for research on mechanisms to detect impending damage and prevent AKI may lead to reduced patient morbidity and death and to substantial health care cost savings.

Lactate concentration gradient from right atrium to pulmonary artery.

INTRODUCTION: We compared simultaneous measurements of blood lactate concentration ([Lac]) in the right atrium (RA) and in the pulmonary artery (PA). Our aim was to determine if the mixing of right atrial with coronary venous blood, having substantially lower [Lac], results in detectable decreases in [Lac] from the RA to the PA. METHODS: A prospective, sequential, observational study was conducted in a medical-surgical intensive care unit. We enrolled 45 critically ill adult individuals of either sex requiring pulmonary artery catheters (PACs) to guide fluid therapy. Immediately following the insertion of the PAC, one paired set of blood samples per patient was drawn in random order from the PAC's proximal and distal ports for measurement of hemoglobin concentration, O2 saturation (SO2) and [Lac]. We defined Delta[Lac] as ([Lac]ra - [Lac]pa), DeltaSO2 as (SraO2 - SpaO2) and the change in O2 consumption (DeltaVO2) as the difference in systemic VO2 calculated using Fick's equation with either SraO2 or SpaO2 in place of mixed venous SO2. Data were compared by paired Student's t-test, Spearman's correlation analysis and by the method of Bland and Altman. RESULTS: We found SraO2 > SpaO2 (74.2 +/- 9.1 versus 69.0 +/- 10.4%; p < 0.001) and [Lac]ra > [Lac]pa (3.9 +/- 3.0 versus 3.7 +/- 3.0 mmol x l-1; p < 0.001). Delta[Lac] correlated with DeltaVO2 (r2 = 0.34; p < 0.001). CONCLUSION: We found decreases in [Lac] from the RA to PA in this sample of critically ill individuals. We conclude that parallel decreases in SO2 and [Lac] from the RA to PA support the hypothesis that these gradients are produced by mixing RA with coronary venous blood of lower SO2 and [Lac]. The present study is a preliminary observation of this phenomenon and further work is needed to define the physiological and clinical significance of Delta[Lac].

Lack of equivalence between central and mixed venous oxygen saturation.

STUDY OBJECTIVE: We compared paired samples of central venous O(2) saturation (Scvo(2)) and mixed venous O(2) saturation (Svo(2)) to test the hypothesis that Scvo(2) is equivalent to Svo(2). We also compared O(2) consumption (Vo(2)) computed with Scvo(2) (Vo(2)cv) to that computed with Svo(2) (Vo(2)v). DESIGN: Prospective, sequential, observational study. SETTING: Combined medical-surgical ICU. PATIENTS: Fifty-three individuals > 18 years of age of either sex who required a pulmonary artery catheter (PAC) to guide fluid therapy. Subjects were identified as postsurgical (32 patients) or medical (21 patients) according to their ICU admission diagnosis. INTERVENTIONS: A PAC was inserted through the internal jugular or subclavian veins. Care was taken to place the PAC proximal port approximately 3 cm above the tricuspid valve. Blood samples were drawn from the proximal and distal ports in random order. An arterial blood sample also was drawn. MEASUREMENTS: Cardiac output in triplicate, systemic pressure, and central pressure. We analyzed blood samples for hemoglobin concentration and O(2) saturation (So(2)). Data were compared by correlation analysis and by the method of Bland and Altman. RESULTS: Svo(2) was consistently lower than Scvo(2) (p < 0.0001), with a mean (+/-SD) bias of -5.2 +/- 5.1%. Similar differences in Scvo(2) and Svo(2) were present within each subgroup (p < 0.001). A lower Svo(2) resulted in Vo(2)v values that were higher than the Vo(2)cv values for all patients in the study (mean Vo(2)v, 236.7 +/- 103.4 mL/min; mean Vo(2)cv, 191.1 +/- 84.0 mL/min; p < 0.001) as well as for patients within each subgroup (p < 0.001). CONCLUSIONS: Measurements of Scvo(2) and Svo(2) were not equivalent in this sample of critically ill patients. Moreover, substituting Scvo(2) for Svo(2) in the calculation of Vo(2) produced unacceptably large errors. The decrease in So(2) between Scvo(2) to Svo(2) may result from the mixing of atrial and coronary sinus blood. As such, this difference may be a marker of myocardial O(2) consumption.

Video-assisted thoracic surgical treatment of initial spontaneous pneumothorax in young patients.

BACKGROUND: The treatment of primary spontaneous pneumothorax in young adults has been controversial. Conventional treatment consisting of chest tube thoracostomy may be associated with morbidity at the time of tube insertion, prolonged hospitalization, and interval operation in many patients. As spontaneous pneumothorax in young adults is usually associated with apical blebs, we hypothesized that video-assisted thoracic surgical (VATS) resection of the blebs at the time of the first pneumothorax may be an effective treatment associated with low morbidity and short hospital stays. METHODS: From July 1992 to February 2001, 156 young adults were treated for spontaneous pneumothorax. Within 12 hours of presentation to the emergency department patients underwent semielective VATS with bleb resection and pleuradesis. During follow-up patients were observed for recurrent pneumothorax. RESULTS: There were 69 men (44%) and 87 women (56%). The median age was 19 years old (range 14 to 38 years old). Patients were predominantly tall and thin. Patients were mildly symptomatic at the time of presentation. Apical blebs were seen in all patients and the presence of blebs was confirmed in the pathologic specimen. In 23 patients bleeding was associated with bleb rupture. There were no postoperative air leaks. The mean hospital stay was 2.4 +/- 0.5 days. Follow-up ranged from 2 to 96 months (median 62 months). There were no recurrences on the index side. CONCLUSIONS: VATS resection of apical blebs is associated with low morbidity and short hospitalization and provides an attractive alternative to the conventional treatment of initial tube thoracostomy and possible interval repeat thoracostomy or operation. VATS may be an effective first line treatment for spontaneous pneumothorax in young adults. Due to the pathophysiology of this disease, patients should be closely followed for the occurrence of pneumothorax on the contralateral side.

Epidemiology of acute kidney injury.

Different definitions for acute kidney injury (AKI) once posed an important impediment to research. The RIFLE consensus classification was the first universally accepted definition for AKI, and has facilitated a much better understanding of the epidemiology of this condition. The RIFLE classification was adapted by a broad platform of world societies, the Acute Kidney Injury Network group, as the preferred AKI diagnostic and staging system. RIFLE defines three increasing severity stages of AKI. One- to two-thirds of intensive care unit (ICU) patients develop AKI according to these criteria which is associated with worse outcomes such as increased length of ICU stay, costs, and mortality. Over the last decade the incidence of AKI has increased, probably as a consequence that baseline characteristics of ICU patients have changed. Another factor that may explain this is that more patients are treated in clinical settings that are associated with high risk for development of AKI. In addition, there may be genetically predetermined risk profiles for development of AKI such homozygotes for the low activity form of the COMT gene. Mortality of AKI patients has decreased over the last few decades, especially when underlying severity of illness is considered. An important consequence of this is the increasing number of surviving AKI patients who develop chronic kidney disease and end-stage kidney disease. In the specific setting of cardiac surgery, AKI occurs in 19-45% of patients. Renal replacement therapy is necessary in approximately 2% of this cohort. AKI that occurs within a 7-day period after cardiac surgery is related to perioperative risk factors, such as preexisting chronic kidney disease, acute ischemia, aorta cross-clamping, or use of cardiopulmonary bypass. AKI that occurs after the first week is mostly a consequence of sepsis or heart failure.

Cardiorenal syndromes: an executive summary from the consensus conference of the Acute Dialysis Quality Initiative (ADQI).

The cardiorenal syndrome (CRS) is a disorder of the heart and kidneys whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction of the other. The general definition has been expanded into five subtypes reflecting the primacy of organ dysfunction and the time-frame of the syndrome: CRS type 1 = acute worsening of heart function leading to kidney injury and/or dysfunction; CRS type 2 = chronic abnormalities in heart function leading to kidney injury or dysfunction; CRS type 3 = acute worsening of kidney function leading to heart injury and/or dysfunction; CRS type 4 = chronic kidney disease leading to heart injury, disease and/or dysfunction, and CRS type 5 = systemic conditions leading to simultaneous injury and/or dysfunction of heart and kidney. Different pathophysiological mechanisms are involved in the combined dysfunction of heart and kidney in these five types of the syndrome.