Superiority of compensatory reserve measurement compared with the Shock index for early and accurate detection of reduced central blood volume status.

BACKGROUND: Shock index (SI) equals the ratio of heart rate (HR) to systolic blood pressure (SBP) with clinical evidence that it is more sensitive for trauma patient status assessment and prediction of outcome compared with either HR or SBP alone. We used lower body negative pressure (LBNP) as a human model of central hypovolemia and compensatory reserve measurement (CRM) validated for accurate tracking of reduced central blood volume to test the hypotheses that SI: (1) presents a late signal of central blood volume status; (2) displays poor sensitivity and specificity for predicting the onset of hemodynamic decompensation; and (3) cannot identify individuals at greatest risk for the onset of circulatory shock. METHODS: We measured HR, SBP, and CRM in 172 human subjects (19-55 years) during progressive LBNP designed to determine tolerance to central hypovolemia as a model of hemorrhage. Subjects were subsequently divided into those with high tolerance (HT) (n = 118) and low tolerance (LT) (n = 54) based on completion of 60 mm Hg LBNP. The time course relationship between SI and CRM was determined and receiver operating characteristic (ROC) area under the curve (AUC) was calculated for sensitivity and specificity of CRM and SI to predict hemodynamic decompensation using clinically defined thresholds of 40% for CRM and 0.9 for SI. RESULTS: The time and level of LBNP required to reach a SI = 0.9 (~60 mm Hg LBNP) was significantly greater ( p < 0.001) compared with CRM that reached 40% at ~40 mm Hg LBNP. Shock index did not differ between HT and LT subjects at 45 mm Hg LBNP levels. ROC AUC for CRM was 0.95 (95% CI = 0.94-0.97) compared with 0.91 (0.89-0.94) for SI ( p = 0.0002). CONCLUSION: Despite high sensitivity and specificity, SI delays time to detect reductions in central blood volume with failure to distinguish individuals with varying tolerances to central hypovolemia. LEVEL OF EVIDENCE: Diagnostic Test or Criteria; Level III.

Anemia in Older Adults.

Anemia is associated with increased morbidity and mortality in older adults. Diagnostic cutoff values for defining anemia vary with age, sex, and possibly race. Anemia is often asymptomatic and discovered incidentally on laboratory testing. Patients may present with symptoms related to associated conditions, such as blood loss, or related to decreased oxygen-carrying capacity, such as weakness, fatigue, and shortness of breath. Causes of anemia in older adults include nutritional deficiency, chronic kidney disease, chronic inflammation, and occult blood loss from gastrointestinal malignancy, although in many patients the etiology is unknown. The evaluation includes a detailed history and physical examination, assessment of risk factors for underlying conditions, and assessment of mean corpuscular volume. A serum ferritin level should be obtained for patients with normocytic or microcytic anemia. A low serum ferritin level in a patient with normocytic or microcytic anemia is associated with iron deficiency anemia. In older patients with suspected iron deficiency anemia, endoscopy is warranted to evaluate for gastrointestinal malignancy. Patients with an elevated serum ferritin level or macrocytic anemia should be evaluated for underlying conditions, including vitamin B12 or folate deficiency, myelodysplastic syndrome, and malignancy. Treatment is directed at the underlying cause. Symptomatic patients with serum hemoglobin levels of 8 g per dL or less may require blood transfusion. Patients with suspected iron deficiency anemia should be given a trial of oral iron replacement. Lower-dose formulations may be as effective and have a lower risk of adverse effects. Normalization of hemoglobin typically occurs by eight weeks after treatment in most patients. Parenteral iron infusion is reserved for patients who have not responded to or cannot tolerate oral iron therapy.

Management of hypertriglyceridemia.

Hypertriglyceridemia is associated with an increased risk of cardiovascular events and acute pancreatitis. Along with lowering low-density lipoprotein cholesterol levels and raising high-density lipoprotein cholesterol levels, lowering triglyceride levels in high-risk patients (e.g., those with cardiovascular disease or diabetes) has been associated with decreased cardiovascular morbidity and mortality. Although the management of mixed dyslipidemia is controversial, treatment should focus primarily on lowering low-density lipoprotein cholesterol levels. Secondary goals should include lowering non-high-density lipoprotein cholesterol levels (calculated by subtracting high-density lipoprotein cholesterol from total cholesterol). If serum triglyceride levels are high, lowering these levels can be effective at reaching non-high-density lipoprotein cholesterol goals. Initially, patients with hypertriglyceridemia should be counseled about therapeutic lifestyle changes (e.g., healthy diet, regular exercise, tobacco-use cessation). Patients also should be screened for metabolic syndrome and other acquired or secondary causes. Patients with borderline-high serum triglyceride levels (i.e., 150 to 199 mg per dL [1.70 to 2.25 mmol per L]) and high serum triglyceride levels (i.e., 200 to 499 mg per dL [2.26 to 5.64 mmol per L]) require an overall cardiac risk assessment. Treatment of very high triglyceride levels (i.e., 500 mg per dL [5.65 mmol per L] or higher) is aimed at reducing the risk of acute pancreatitis. Statins, fibrates, niacin, and fish oil (alone or in various combinations) are effective when pharmacotherapy is indicated.