Critical Care Medicine

Critical care medicine specializes in caring for the most seriously ill patients. These patients are best treated in an intensive care unit (ICU) staffed by experienced personnel. Some hospitals maintain separate units for special populations (eg, cardiac, trauma, surgical, neurologic, pediatric, or neonatal patients). ICUs have a high nurse:patient ratio to provide the necessary high intensity of service, including treatment and monitoring of physiologic parameters.

Cardiac arrest is the cessation of cardiac mechanical activity resulting in the absence of circulating blood flow. Cardiac arrest stops blood from flowing to vital organs, depriving them of oxygen, and, if left untreated, results in death. Sudden cardiac arrest is the unexpected cessation of circulation within a short period of symptom onset (sometimes without warning). Sudden cardiac arrest occurs outside the hospital in more than 350,000 people/year in the US, with a 90% mortality.

Bag-valve-mask (BVM) ventilation is the standard method for rapidly providing rescue ventilation to patients with apnea or severe ventilatory failure.

Cricothyrotomy, whether traditional surgical cricothyrotomy or percutaneous cricothyrotomy using a guidewire, uses an incision through the skin and cricothyroid membrane through which an artificial airway is inserted into the trachea. Cricothyrotomy is typically done emergently, when endotracheal intubation is contraindicated or unachievable by other methods of tube insertion, and non-definitive methods of airway management and ventilation (ie, extraglottic devices such as a laryngeal mask airway) fail to adequately ventilate and oxygenate the patient.

Ultrasound-guided cannulation of the femoral artery uses real-time (dynamic) ultrasound to guide arterial puncture and a guidewire (Seldinger technique) to thread a catheter through the femoral artery and into the distal aorta.

Intraosseous cannulation is the placing of a sturdy needle through cortical bone and into the medullary cavity—to emergently infuse fluids and blood products into critically ill patients.

Respiratory arrest and cardiac arrest are distinct, but inevitably if untreated, one leads to the other. (See also Respiratory Failure, Dyspnea, and Hypoxia.)

Acute respiratory failure is a life-threatening impairment of oxygenation, carbon dioxide elimination, or both. Respiratory failure may occur because of impaired gas exchange, decreased ventilation, or both. Common manifestations include dyspnea, use of accessory muscles of respiration, tachypnea, tachycardia, diaphoresis, cyanosis, altered consciousness, and, without treatment, eventually obtundation, respiratory arrest, and death. Diagnosis is clinical, supplemented by measurements of arterial blood gases (ABGs) and chest x-ray. Treatment is usually in an intensive care unit and involves correction of the underlying cause, supplemental oxygen, and ventilatory assistance if needed.

Sepsis is a clinical syndrome of life-threatening organ dysfunction caused by a dysregulated response to infection. In septic shock, there is critical reduction in tissue perfusion; acute failure of multiple organs, including the lungs, kidneys, and liver, can occur. Common causes in immunocompetent patients include many different species of gram-positive and gram-negative bacteria. Immunocompromised patients may have uncommon bacterial or fungal species as a cause. Signs include fever, hypotension, oliguria, and confusion. Diagnosis is primarily clinical combined with culture results showing infection; early recognition and treatment is critical. Treatment is aggressive fluid resuscitation, antibiotics, surgical excision of infected or necrotic tissue and drainage of pus, and supportive care.

Shock is a state of organ hypoperfusion with resultant cellular dysfunction and death. Mechanisms may involve decreased circulating volume, decreased cardiac output, and vasodilation, sometimes with shunting of blood to bypass capillary exchange beds. Symptoms include altered mental status, tachycardia, hypotension, and oliguria. Diagnosis is clinical, including blood pressure measurement and sometimes measurement of markers of tissue hypoperfusion (eg, blood lactate, base deficit). Treatment is with fluid resuscitation, including blood products if necessary, correction of the underlying disorder, and sometimes vasopressors.