The Journal of critical illness最新文献

Transcutaneous cardiac pacing is a temporary method of pacing that may be indicated in patients with severe symptomatic or hemodynamically unstable bradyarrhythmias. It is particularly helpful in patients with reversible or transient conditions, such as digoxin toxicity and atrioventricular block in the setting of inferior wall myocardial infarction, or when transvenous pacing is not immediately available or carries a high risk of complications. Most patients with minimal hemodynamic compromise require a current of 40 to 80 mA; pacing thresholds tend to be higher in patients who have emphysema or pericardial effusion and in those who receive positive pressure ventilation. On electrocardiography, successful capture usually is characterized by a widened QRS complex, followed by a distinct ST segment and broad T wave. The hemodynamic response to pacing also must be confirmed by assessing the patient's arterial pulse. Proper skin preparation and electrode positioning ensure successful capture in most situations. Adequate sedation and analgesia are essential in ensuring patient comfort.

Although sputum culture and Gram's staining have been the traditional methods for determining the cause of lower respiratory tract infections, oropharyngeal contamination and improper sputum collection can limit their usefulness. Nevertheless, these noninvasive techniques remain a rapid means of gathering diagnostic clues. Alternative approaches include acid-fast sputum stains, direct immunofluorescence examination, enzyme immunoassays, DNA probes, and serologic testing. However, for critically ill patients, invasive procedures (such as bronchoscopy and thoracentesis) can provide more definitive diagnoses to guide selection of antimicrobial therapy.

Critically ill patients frequently require dialysis. Options include intermittent hemodialysis, peritoneal dialysis, and various forms of continuous extracorporeal therapy. Intermittent hemodialysis is useful for hemodynamically stable patients who can tolerate rapid solute and fluid removal. Peritoneal dialysis, which is underused in the ICU, offers two distinct advantages: It does not require vascular access and systemic anticoagulation is not necessary. Continuous extracorporeal therapies are better tolerated by hemodynamically unstable patients, since these techniques can remove large amounts of fluid over an extended period. Base your choice of therapy on the patient's condition and needs, the options available at your institution, and the experience of you and your staff.

Many critically ill patients require nutritional support to avoid protein-calorie malnutrition. Enteral administration is preferred because it is less expensive than parenteral nutrition and is associated with fewer complications. Nasogastric insertion is the route most often used; however, oral insertion is required for intubated patients. Administration of a promotility agent increases the chances that the feeding tube will migrate transpylorically; it also improves gastric emptying. To lower the risk of aspiration, check the level of gastric residuum before initiating, or increasing the level of, nutritional support. Diarrhea is not an indication for stopping enteral nutrition.

Elderly patients are susceptible to acute renal failure largely because of functional impairment of the kidneys secondary to diseases such as arteriosclerosis, hypertension, and heart failure. Successful prevention of renal failure in the elderly hinges on understanding the age-associated changes in renal anatomy and physiology. To prevent renal failure, rehydrate elderly patients who suffer significant fluid loss to avoid volume depletion. In addition, maintain adequate blood pressure in these patients, consider glomerular filtration rate when determining the dosage of nephrotoxic antibiotics, and administer saline preparation before injecting radiocontrast dyes.

In patients with shock and evidence of hypoperfusion, target therapy at increasing oxygen delivery and decreasing oxygen consumption. To augment delivery, increase arterial oxygenation (with mechanical ventilation and high levels of inspired oxygen), hemoglobin level to at least 10 g/dL (with transfusions of red blood cells), and cardiac output (with hydration and inotropic support). Avoid vasopressors because they increase afterload and thereby decrease cardiac output and oxygen delivery. To reduce oxygen consumption, consider antipyretics (to lower metabolic demand) and mechanical ventilation plus sedatives or paralytics (to decrease the work of breathing). Continue therapy until oxygen consumption is no longer coupled to delivery.

Pericardiocentesis is primarily indicated for the management of emergent cardiac tamponade. Insert the needle into the left xiphocostal angle perpendicular to the skin and 3 to 4 mm below the left costal margin (the preferred approach); advance it 5 to 10 mm (or more if necessary) until it reaches the pericardial fluid. A "giving" sensation indicates penetration of the parietal pericardium; a "ticking" one, needle contact with the heart. The needle's position may be confirmed with two-dimensional echocardiography or fluoroscopy. Use the Seldinger technique to insert a catheter for fluid drainage. Monitor the patient continuously for recurrent tamponade, which may result from catheter blockage or fluid reaccumulation.

Consider intensive care for any patient with an intracerebral hemorrhage (ICH) and coma, cardiac ischemia, rhythm disturbances, severe respiratory distress, labile hypertension, or progressive neurologic deficits. Begin treatment with diuretics and prophylaxis of deep venous thrombosis; some patients may also require fluid restriction, hyperventilation, antiepileptic drugs, intracerebral drainage, or surgical evacuation. Common causes of ICH include hypertension; vascular malformations; hemorrhagic infarction; and administration of sympathomimetics, anticoagulants, or fibrinolytics. To predict outcome, consider both the clinical features and radiologic findings at presentation.

Use the following organized approach to determine whether a patient can be weaned from tracheostomy. Consider airway decannulation only if the original upper airway obstruction has resolved, if mechanical ventilation is no longer needed, and if airway secretions are controlled. Regard the presence of a vigorous cough and the absence of aspiration as additional portents of success. Most critically ill patients benefit from a well-planned, progressive weaning protocol. The tracheostomy button is an ideal weaning device; it maintains the stoma tract and allows the patient to breathe and clear secretions through the upper airway. Monitor the patient for up to 48 hours to ensure tolerance to decannulation.

Myocardial infarction (MI), myocardial ischemia, ventricular dysrhythmias, and sudden cardiac death (SCD) occur most frequently in the morning, especially in the first few hours after awakening. Among individual patients, however, this pattern may vary widely. Peaks in heart rate, blood pressure, and platelet aggregability and a trough in fibrinolytic activity are thought to influence the morning onset of events. beta-Blockers may blunt the peak occurrence of MI, SCD, and ischemia. Some calcium channel blockers may modify the pattern of ischemia. Alternate-day therapy with 325 mg of aspirin has been shown to blunt the morning onset of MI. The efficacy of thrombolytics may be affected by daily fluctuations in fibrinolytic activity.