Critical Care Medicine: Principles of Critical Care — Comprehensive Support

Comprehensive Support of the Critically Ill Patient

Modern intensive care is delivered by an interdisciplinary team — nurses, physicians, pharmacists, respiratory therapists, physical and occupational therapists, advanced practice providers, case managers, and social workers — and the best team dynamics rest on explicit recognition of each member’s role, shared communication models, and an environment of psychological safety. The usual goals of care are to restore health and return the patient home while minimizing hospital time, medical complications, and the long-term effects of critical illness. When disease is overwhelming or irreversible, goals shift toward comfort and dignity at the end of life.

Because critically ill patients are at risk for a predictable set of hospital-acquired conditions — health care–associated infections, skin and soft tissue pressure injury, malnutrition, gastrointestinal bleeding, delirium, and weakness — protocolized care is the backbone of ICU safety. Protocols should be evidence-based and reviewed periodically for accuracy. The complexity of critical illness also favors a methodical, organ system–based approach to daily rounds, reviewing the main disease process, the affected organs and systems, and the related interventions.

Sedation and Analgesia: Treat Pain First

Most ICU patients require both analgesia and sedation, and the contemporary approach is analgesia first. Pain should be assessed with an objective scale at least every 4 hours, and preemptive analgesia should be provided before painful procedures such as arterial line or thoracostomy tube insertion. Opiates remain the mainstay of therapy, but multimodal strategies — combining nonpharmacologic techniques and non-opiate drugs — improve pain control and reduce total opiate exposure (Table 1). Nonpharmacologic options include music therapy, massage, relaxation techniques, local cold therapy for procedures, and family involvement; pharmacologic adjuncts include acetaminophen, low-dose ketamine in postsurgical patients, and gabapentin, carbamazepine, or pregabalin for neuropathic pain, with an opiate or NSAID given preprocedurally.

Once pain is controlled, sedation addresses the remaining needs — anxiolysis, relief of subjective dyspnea, suppression of autonomic hyperactivity that could precipitate myocardial ischemia, and reduction of total oxygen consumption. Like analgesia, sedation must be monitored and titrated with an objective scale such as the Richmond Agitation-Sedation Scale (RASS). Guidelines favor light sedation, often achievable with intermittent opiate dosing alone; when continuous sedation is required, propofol or dexmedetomidine is preferred over benzodiazepines, which are associated with increased delirium. Nurse-driven sedation protocols and daily interruption of sedation are standard elements of care, and a bispectral index monitor can assess depth of sedation when clinical scales cannot be used, such as during neuromuscular blockade.

Daily protocolized interruption of sedation and analgesia shortens the duration of mechanical ventilation and ICU stay and reduces the incidence of delirium, although a 90-day mortality benefit has not been shown; protocolized light sedation achieves similar patient outcomes. Because sedatives and opiates accumulate in hepatic or renal dysfunction, prolonged infusions deserve particular vigilance. Neuromuscular blocking agents (e.g., cisatracurium) are reserved for severe ventilator dyssynchrony despite optimal sedation — typically in severe ARDS — and because they paralyze without altering consciousness, sedative-induced amnesia is mandatory whenever they are used; prolonged courses risk a postparalytic myopathy.

Delirium

Delirium is an acute change in cognitive function developing over hours to days and fluctuating during the day: inattention, disorganized thinking, executive dysfunction, altered level of consciousness (from lethargy to hypervigilance), perceptual disturbances (hallucinations or delusions), altered psychomotor activity, sleep-wake disruption, and labile mood. It is extremely common in the ICU and is associated with longer stays, greater morbidity and mortality, and post–intensive care cognitive impairment. Risk factors include benzodiazepine exposure, blood transfusion, pre-existing dementia, older age, previous coma, surgery or trauma before ICU admission, and high severity of illness. Patients should be monitored with a validated tool such as the Confusion Assessment Method–ICU (CAM-ICU) or the Intensive Care Delirium Screening Checklist.

The differential diagnosis of ICU delirium is broad — sepsis, sedatives and analgesics, drug withdrawal, metabolic and electrolyte derangements, intracranial pathology, seizures, hypoxia, shock, and vitamin deficiencies — so treatment begins with identifying and correcting the underlying cause. Large randomized studies have failed to demonstrate any medication effective for preventing or treating delirium; antipsychotics remain controversial, and benzodiazepines should not be used unless treating alcohol withdrawal or seizures. Prevention is multicomponent and nonpharmacologic: early mobilization, preservation of nocturnal sleep, adequate pain management, reorientation of the patient, removal of vascular and urethral catheters, provision of visual and hearing aids, minimization of nonessential medications, adequate nutrition and hydration, and family engagement — the elements organized in the ABCDEF bundle (Table 2).

Nutritional Support

Malnutrition increases morbidity and mortality in critical illness, so every ICU patient should receive a nutritional evaluation. Enteral nutrition should start within 24 to 48 hours of admission — early enteral feeding is associated with lower mortality and fewer infections — and the enteral route is preferred unless a contraindication is present (e.g., bowel perforation or active hemorrhage). Patients receiving vasopressors, neuromuscular blockers, hypothermia, or extracorporeal life support should be fed enterally as soon as they can tolerate it. Critically ill patients unable to maintain volitional intake should be fed as soon as possible via a gastric tube, large-bore tube, small-bore tube, or postpyloric tube; postpyloric feeding is recommended when a high risk for aspiration exists, but delays in placing a postpyloric tube should not delay the initiation of enteral nutrition.

Two practices deserve caution once enteral feeding is under way: routine measurement of gastric residuals is no longer recommended, and the timing of supplemental parenteral nutrition matters — it should be considered only after 7 to 10 days of meeting less than 60% of energy and protein requirements by the enteral route alone. Parenteral nutrition carries its own complications (hyperglycemia, fatty liver, cholestasis, and sepsis), and delaying supplemental parenteral nutrition until about day 8 of the ICU stay improves recovery and reduces ICU-related complications. Conversely, parenteral nutrition should be started as soon as possible for severely malnourished patients, those at high risk for malnutrition, and those in whom enteral nutrition is not possible. Glycemic control accompanies nutritional support: guidelines favor targeting glucose of 180 mg/dL or less rather than aggressive normalization, which increases hypoglycemia and mortality.

Early Mobilization

Weakness in critical illness is multifactorial — immobility, the disease itself, medications, and medical interventions all contribute. Immobility alone can cause muscular weakness, joint stiffness, pressure ulcers, osteoporosis, gastrointestinal dysmotility, and dysautonomia, and even a few days of bed rest can have prolonged effects: long-term follow-up of critical illness survivors demonstrates persistent weakness at 1 and 5 years. Mobilization strategies that combine interruption of sedation with physical and occupational therapy in the earliest days of critical illness are associated with shorter ICU and hospital stays, fewer days of mechanical ventilation, and improvements in functional status and quality of life; very early physical and occupational therapy in ventilated patients also reduces delirium and improves functional independence at hospital discharge. ICU-acquired weakness — neuropathies and myopathies that typically emerge after about a week in the ICU — is the syndrome these efforts aim to prevent.

ICU Care Bundles

A care bundle is a small series of interventions that have been shown to improve patient outcomes when used together, and bundles help clinicians monitor patients and guide appropriate interventions. Three bundles widely applied in critical care address ventilator-associated pneumonia, central line–associated bloodstream infection, and sepsis (Table 3). The infection-prevention elements are reinforced by ICU infection-control data: strict adherence to hand hygiene, full-barrier precautions at insertion, chlorhexidine skin preparation, avoidance of the femoral site, and timely catheter removal measurably reduces device-related infections — and the longer any invasive device remains in place, the greater the infection risk.

High-Value Care in the ICU

Critical care accounts for a large share of U.S. health care spending, yet survival and quality-of-life outcomes are not clearly better than in other high-income countries — an argument for high-value care, defined as care that balances clinical benefit against cost and harm to improve patient outcomes. The ICU is a high-leverage setting: resources are expensive, and the culture favors aggressive resource use. Through the American Board of Internal Medicine Foundation’s Choosing Wisely campaign, internal medicine and critical care societies promote cost-effective strategies that improve patient care and avoid waste and harm. The 2021 Society of Critical Care Medicine recommendations target five overused practices: (1) retaining catheters and drains without a clear indication; (2) delaying discontinuation of mechanical ventilation; (3) continuing antibiotic therapy without need; (4) delaying mobilization of critically ill patients; and (5) providing care without ensuring that it aligns with patient preferences. The earlier 2014 list also recommended against daily routine laboratory testing.