The ICU

Intravenous anesthetics have been used in modern anesthesia practice since the 20th century. Modern anesthesia began with inhaled anesthetics; however, intravenous agents were adopted because injected or infused doses could be more closely controlled with little wasted medication. Several groups of agents are currently available (e.g., barbiturates, benzodiazepines, and dissociatives), but the most widely used are fentanyl, midazolam, and propofol.

Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. The major cellular response involves neutrophils and macrophages to phagocytose and lyse the injurious organism or repair necrosed tissue after injury. Inflammation can be pathologic if it is prolonged or when normal processes create an excessive response (such as with atherosclerosis). There are multiple mediators of inflammation that overlap with innate immunity when they respond to injurious stimuli. Inflammation can become chronic, resulting in the formation of granulomas, tissue damage, and the loss of organ function.

Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain is a subjective experience. Acute pain lasts < 3 months and typically has a specific, identifiable cause. Chronic pain lasts > 3 months and may exist in the absence of tissue damage or after healing would have been expected to occur. Pain management involves a combination of addressing underlying causes and using a systematic approach tailored to the clinical scenario.

In the context of acute or chronic kidney failure, renal function may diminish to a point at which it is no longer able to adequately support life. When this happens, renal replacement therapy is indicated. Renal replacement therapy refers to dialysis and/or kidney transplantation. Dialysis is a procedure by which toxins and excess water are removed from the circulation. Hemodialysis and peritoneal dialysis (PD) are the two types of dialysis, and their primary difference is the location of the filtration process (external to the body in hemodialysis versus inside the body for PD).

Benzodiazepines work on the gamma-aminobutyric acid type A (GABAA) receptor to produce inhibitory effects on the CNS. Benzodiazepines do not mimic GABA, the main inhibitory neurotransmitter in humans, but instead potentiate GABA activity. The drug class of benzodiazepines has anxiolytic, muscle-relaxant, hypnotic, sedative, and anticonvulsant properties. These agents are not generally recommended for long-term use, as patients can develop physiological and psychological dependence. Side effects may include cognitive impairment, somnolence, and respiratory depression.

Brain death is a legal and clinical term describing the irreversible cessation of all cerebral and brainstem functions, including the ability of the brain stem to regulate vegetative and respiratory activities. Brain death can be due to a variety of etiologies causing catastrophic injuries to the brain, including brain ischemia due to cardiopulmonary arrest, drugs, sepsis, and trauma. The diagnosis is made at the bedside based on the clinical context and performance of a neurological exam. Additional ancillary studies may be needed to support the diagnosis and diagnostic criteria may vary among states and countries. A diagnosis of brain death must be established prior to consideration of organ donation.

Organ dysfunction resulting from a dysregulated systemic host response to infection separates sepsis from uncomplicated infection. The etiology is mainly bacterial and pneumonia is the most common known source. Patients commonly present with fever, tachycardia, tachypnea, hypotension, and/or altered mentation. Septic shock is diagnosed during treatment when vasopressors are necessary to control hypotension. Sepsis and septic shock are medical emergencies and antibiotics are given within an hour of diagnosis.