People requiring intensive care include those after major surgery, with severe head trauma, life-threatening acute illness, respiratory insufficiency, coma, haemodynamic insufficiency, severe fluid imblance or with the failure of one or more of the major organ systems (life-critical systems or others).
It is generally the most expensive, high technology and resource intensive area of medical care. It is offered only to those whose condition is retrievable and who have a good chance of surviving with intensive care aid, the issue is whether treatment will "prolong life or prolong suffering". People are not admitted to ICU to die.
Intensive care usually takes a system by system approach to treatment, rather than the SOAP (subjective, objective, analysis, plan) approach of high dependency care. The nine key systems[1] are each considered on an obervation-intervention-impression basis to produce a daily plan. As well as the key systems ICU treatment also raises other issues including psychological health, pressure points, mobilisation and physiotherapy, and secondary infections.
Common equipment in an intensive care unit (ICU) includes ventilators to assist breathing through an endotracheal tube or a tracheotomy opening; dialysis equipment for renal problems; equipment for the constant monitoring of bodily functions; a web of intravenous lines, feeding tubes, nasogastric tubes, suction pumps, drains and catheters; and a wide array of drugs to treat the main condition(s), induce sedation, reduce pain, and prevent secondary infections.
[1] The key IC systems are (alphabetically) -- central nervous system, cardiovascular system, endocrine system, gastro-intestinal tract (and nutritional condition), haematology, microbiology (including sepsis status), renal (and metabolic), respiratory system, peripheries (and skin)