Acute kidney injury: epidemiology and diagnostic criteria

PURPOSE OF REVIEW: To review recent advances in the definitions and diagnostic criteria for acute renal failure and acute kidney injury. To explore how these changes impact the epidemiology and clinical implications for patients in the intensive care unit. RECENT FINDINGS: Recently published consensus criteria for the definition of acute renal failure/acute kidney injury have led to significant changes in how we think about this disorder. Studies from around the world, both in and out of the intensive care unit, have shown a dramatic incidence of acute kidney injury and high associated mortality. This review considers these new findings and their historical context, and attempts to shed new light on this old problem. SUMMARY: Small changes in kidney function in hospitalized patients are important and impact on outcome. RIFLE criteria provide a uniform definition of acute kidney injury and are increasingly used in literature.     

Prevention of acute renal failure

Acute renal failure (ARF) comprises a family of syndromes that is characterized by an abrupt and sustained decrease in the glomerular filtration rate. In the ICU, ARF is most often due to sepsis and other systemic inflammatory states. ARF is common among the critically ill and injured and significantly adds to morbidity and mortality of these patients. Despite many advances in medical technology, the mortality and morbidity of ARF in the ICU continue to remain high and have not improved significantly over the past 2 decades. Primary strategies to prevent ARF still include adequate hydration, maintenance of mean arterial pressure, and minimizing nephrotoxin exposure. Diuretics and dopamine have been shown to be ineffective in the prevention of ARF or improving outcomes once ARF occurs. Increasing insight into mechanisms leading to ARF and the importance of facilitating renal recovery has prompted investigators to evaluate the role of newer therapeutic agents in the prevention of ARF.     

Participation in 150 min/wk of moderate or higher intensity physical activity yields greater weight loss after gastric bypass surgery.

BACKGROUND: The American College of Sports Medicine's position stand on weight loss and prevention of weight regain in adults has suggested that overweight adults should participate in a minimum of 150 min/wk of moderate intensity physical activity (PA). This study compared the 3-, 6-, and 12-month postoperative weight loss between gastric bypass surgery (GBS) patients who met or exceeded the recommended 150 min/wk of moderate or higher PA and those not meeting the recommendation. METHODS: The self-administered short version of the International Physical Activity Questionnaire was used to assess moderate or higher intensity PA participation at 3 (n = 178), 6 (n = 128), and 12 months (n = 209) after GBS. The patients' height and body weight were obtained to determine the kilograms of weight lost, percentage of excess weight loss, body mass index change, and total weight loss percentage. The weight loss differences were analyzed using analysis of covariance at each point, with age and preoperative body mass index as covariates. RESULTS: Patients reporting 150 min/wk of moderate or higher PA had significantly (P <.05) greater weight lost, percentage of excess weight loss, change in body mass index, and total weight loss percentage at 6 and 12 months postoperatively. The percentage of excess weight loss was 56.0% +/- 11.5% versus 50.5% +/- 11.6% and 67.4% +/- 14.3% versus 61.7% +/- 17.0% for the group meeting and not meeting the PA requirement at 6 and 12 months after GBS, respectively. No significant difference existed at 3 months after GBS. CONCLUSION: Participation in a minimum of 150 min/wk of moderate or higher intensity PA was associated with greater postoperative weight loss at 6 and 12 months postoperatively. Patients should be encouraged to meet or exceed this recommendation until prospective, randomized studies have definitively established a link between PA and greater postoperative weight loss and maintenance.     

Does diabetes affect weight loss after gastric bypass?

BACKGROUND: Weight loss in diabetics improves glycemic control. We investigated whether diabetes mellitus (DM) adversely affects postgastric bypass weight loss. METHODS: Our database was queried for the demographics and outcomes of patients with and without DM who had undergone gastric bypass surgery. DM was subdivided by severity: diet-controlled, oral hypoglycemic agents, and insulin. RESULTS: Of the 3193 patients, 655 (20%) had DM. The DM group was older (45.8 +/- 10.4 yr versus 39.1 +/- 9.9 yr, P <.0001), with more co-morbidities: hypertension (70.5% versus 44.2%, P <.0001), sleep apnea (36.7% versus 26.1%, P <.0001), and venous stasis (5.6% versus 2.6%, P <.0001). More men had DM (25.6% versus 19.3%, P = .0006). The age-adjusted, preoperative weight, and body mass index were equal. A direct relationship was found between DM severity and age, weight, and co-morbidities. At 1 year, the DM group had a lower percentage of excess weight loss (60.8% +/- 16.6% versus 67.6% +/- 16.7%, P <.0001) and greater body mass index (34.2 +/- 7.1 kg/m(2) versus 32.3 +/- 7.2 kg/m(2), P <.0001). The percentage of excess weight loss was 67.6% for those without DM, 63.5% for those with diet-controlled DM, 60.5% for those with DM controlled by oral hypoglycemic agents, and 57.5% for those requiring insulin. DM resolved in 89.8% of those with diet-controlled DM, 82.7% of those taking oral hypoglycemic medication, and 53.3% of those requiring insulin. Hypertension resolution was greatest in patients without DM (74.4% versus 63.5%, P <.0001). CONCLUSION: The results of our study have shown that those with DM typically have more co-morbidities, despite having no difference in preoperative weight compared with those without DM. Despite the lower weight loss, those with DM had significant resolution of their DM and hypertension and should not be deterred from undergoing gastric bypass surgery.     

An evaluation of pharmacological strategies for the prevention and treatment of acute renal failure

Acute renal failure (ARF) occurs frequently in hospitalised patients, and is associated with significant morbidity and mortality. The most common and generalised forms of acute renal failure are pre-renal conditions and intra-renal acute tubular necrosis (ATN). Pre-renal ARF in its pure state should be entirely reversible by restoring renal perfusion, but in some cases ATN has already occurred. ATN remains a more vexing problem, and is seen most often with hypotension, perioperative or systemic inflammatory stresses, radiocontrast administration, and exposure to nephrotoxins. Among the available pharmacological options for prevention or treatment of ATN, there is a remarkable lack of definitive evidence supporting specific therapy in any setting. Although loop diuretics, mannitol, and dopamine are frequently used for prevention and/or treatment of ATN, clinical studies have failed to prove value. Other drugs with theoretical value, specifically atrial natriuretic peptide analogues, adenosine blockers, and calcium antagonists, have been insufficiently studied to recommend use. Other pharmacological options may arise in the future. Ensuring adequate intravascular fluid volume remains the only approach to managing ATN which can be considered relatively effective and safe. Given the abundant theoretical basis for the prevention and treatment of ATN with drugs, well conducted clinical studies with relevant outcome measures are clearly warranted.