Physiological stress increases renal injury in eNOS-knockout mice.

African Americans have a fourfold greater likelihood of developing end-stage renal disease (ESRD) compared with Caucasians. It has been proposed that the increased prevalence may be explained by non-traditional factors such as environmental stress and psychosocial factors. In this study, we used infrequent running to exhaustion as a physiological stressor to mimic real life experiences, such walking up stairs when an elevator is malfunctioning or running to catch a bus, to study its effect on renal injury in a hypertensive mouse model (endothelial nitric oxide synthase-deficient mice; eNOS(-/-)). This model has previously been shown to have renal injury comparable to that observed in African Americans. The effect of physiological stress on renal injury was examined in the setting of low (0.12%), control (0.45%) and high (8%) dietary salt. Following bouts of physiological stress, eNOS(-/-) mice had significantly greater interstitial inflammation compared with unstressed eNOS(-/-) mice (two-way analysis of variance (2-ANOVA), Holm-Sidak; P<0.01). Interestingly, eNOS(-/-) mice on a high-salt diet had greater interstitial inflammation compared with similarly stressed eNOS(-/-) mice on a low- or control-salt diet (2-ANOVA, Holm-Sidak; P<0.03). These effects of stress were independent of systolic blood pressure (141±7, 143±4, and 158±8 vs. 141±4, 138±5, 150±4 mm Hg; end of study vs. baseline, respectively). There was no significant effect of stress or dietary salt on renal injury in control wild-type mice (eNOS(+)/(+)). These data demonstrate that physiological stress exacerbates the renal injury associated with hypertension and that high-salt compounds this effect of stress. These results provide support for the idea that psychosocial and environmental factors contribute to the increased prevalence of ESRD in hypertensive African Americans.

Anesthesia for the patient with tracheal stenosis.

Tracheal stenosis may occur secondary to trauma, tumors, infection, inflammatory diseases, or iatrogenic causes. Understanding these lesions requires a basic understanding of the physics of airflow. All of these patients must be carefully evaluated and require a series of tests, including pulmonary function tests and radiographic studies. Treatment of tracheal lesions is a multidisciplinary issue and requires the close participation of interventional pulmonologists, anesthesiologists, and surgeons.

The effect of salt on renal damage in eNOS-deficient mice.

African Americans have an increased incidence of end-stage renal disease and are characterized as having reduced bioavailability of nitric oxide and salt-sensitivity. We propose that endothelial nitric oxide synthase (eNOS) knockout mice (eNOS(-/-)) are a suitable model of hypertension-associated renal injury as seen in African Americans. Therefore, the purpose of this study was to determine whether older eNOS(-/-) mice have hypertension-associated renal injury and if dietary salt modulates this injury. Six-month-old eNOS(-/-) mice were placed on 0.12%, 0.45% or 8% NaCl diet for 8 weeks and blood pressure measured weekly; kidneys were collected for pathology evaluation and scoring at the end of the 8-week period. Mice deficient of eNOS were hypertensive at baseline compared with control mice in all three groups (128+/-3 vs. 112+/-3, P<0.05). Blood pressure was significantly elevated from baseline in eNOS(-/-) on 0.45 and 8% salt diets (P<0.02). The composite renal pathology scores for eNOS(-/-) mice were significantly greater than wild-type mice, indicating high salt intake exacerbates the injury (P<0.001 vs. normal salt diet). eNOS(-/-) mice may be used as a model of salt-induced and hypertension-associated renal injury as seen in African Americans.

Perioperative beta-blocker and statin therapy.

PURPOSE OF REVIEW: Perioperative beta-blockade and statin therapy have been advocated to reduce cardiac risk of noncardiac surgery. This review evaluates recent articles published on the cardioprotective effects of perioperative therapy with these medications. RECENT FINDINGS: Initial studies evaluating beta-blocker therapy during the perioperative period suggested that beta-blockers may be beneficial in reducing cardiac deaths and myocardial infarctions. Later studies and recent meta-analyses, however, are less favorable and suggest that beta-blockers may be associated with increased incidence of bradycardia and hypotension. One randomized trial and several cohort studies have found a significant reduction in cardiovascular complications with perioperative statin therapy. Additionally, statin withdrawal is associated with increased postoperative cardiac risk. SUMMARY: Based upon the available evidence and guidelines, patients currently taking beta-blockers should continue these agents. Patients undergoing vascular surgery who are at high cardiac risk should also take beta-blockers. The question remains regarding the best protocol to initiate perioperative beta-blockade. Statins should be continued in patients already taking these agents prior to surgery. The optimal duration and time of initiation of statin therapy remains unclear.