ICU Delirium

Introduction

As the survival of critically ill patients improves, the development of delirium in the ICU has become a growing public health issue. Delirium is defined as a rapid change in consciousness (hours to days) characterized by reduced environmental awareness, decreased attention and altered cognition. These clinical features can manifest themselves as memory deficits, disorientation, hallucinations, fluctuating levels of alertness and motor abnormalities.

According to Ely et al., as much as 83% of ICU patients on mechanical ventilation develop delirium. This figure is significant as ICU delirium is associated with negative patient and healthcare outcomes. These outcomes include increased time on mechanical ventilation, longer ICU and hospital length of stay, higher health care costs, increased cognitive dysfunction and increased risk of death.

Delirium Subtypes

Delirium can be divided into 3 subtypes: hyperactive, hypoactive and mixed. The table below matches each subtype with common clinical manifestations.

Subtype	Clinical Manifestations
Hyperactive	Agitation, restlessness, emotional lability, hallucinations
Hypoactive	Lethargy, decreased responsiveness, slowed motor skills
Mixed	Fluctuation between hyper- and hypo- active symptoms

Source: Meagher D. Motor subtypes of delirium: past, present and future. Int Rev Psychiatry. 2009 Feb;21(1):59-73

In critically ill patients, mixed delirium is the most common subtype (54.9%). Hypoactive delirium is second (43.5%), followed by a small percentage (1.6%) of patients who display purely hyperactive symptoms. ICU patients aged 65 and older are particularly susceptible to hypoactive delirium.

Causes and Risk Factors

Delirium develops as a result of multiple causes and risk factors. Old age, dementia [McNicoll 2003], depression, smoking and alcohol use [all others-->[Brummel 2013] are among the personal factors that increase patient risk. Another 20+ risk factors related to the patient's medical condition have been identified by the literature. Below is a common mnemonic used to help clinicians identify potential causes related to illness and treatment:

• D-Drugs
• E- Eyes, ears, and other sensory deficits
• L- Low O2 states
• I- Infection
• R- Retention (of urine or stool)
• I- Ictal state
• U- Underhydraton/undernutrition
• M- Metabolic causes

Adapted from: Saint Louis University Geriatrics Evaluation Mnemonics Screening Tools (SLU GEMS). Developed or compiled by: Faculty from Saint Louis University Geriatrics Division and St. Louis Veterans Affairs GRECC.

Additional risk factors common to the hospital setting include absence of daylight, lack of visitors, sleep deprivation, immobility, sedatives and hospital lines/catheters.

Pathophysiology

The pathophysiology of delirium is not well understood. Theories related to its development and progression cite anatomical changes in the brain and neurotransmitter imbalances (ex. abnormal levels of serotonin, decreased acetylcholine, excess dopamine) as possible physiologic mechanisms.

Diagnosis

Given the unknown pathophysiology, there is no imaging or laboratory tests that can diagnose delirium. As such, delirium is a diagnosis of exclusion that requires careful clinical testing and observation.

Assessment and Monitoring

Guidelines for treating Pain, Agitation and Delirium (PAD) recommend two tests for the assessment of delirium in adult ICU patients:

(1) The Intensive Care Delirium Screening Checklist (ICDSC)

(2) The Confusion Assessment Method for the ICU (CAM-ICU)

The following video provides a step by step demonstration of the CAM-ICU.

https://www.youtube.com/watch?v=yEwBzKTbJEk

Prevention and Treatment

In 2010, Vasilevskis et al [cite] proposed the ABCDE model to screen and prevent delirium among ICU patients. The mnemonic consists of the following concepts:

• A-Assess, prevent and manage pain: behavioral pain scale [1], critical-care pain observation tool (CPOT*) [valid in delirious ICU patients; facial expressions, body movements, muscle tension, compliance with the ventilator for mechanically ventilated patients or vocalization for nonintubated patients- http://www.icudelirium.org/docs/cpot-description-and-directives-020616.pdf]
• B-Both Spontaneous Awakening Trials (SAT) [daily sedative and narcotic interruptions as long as pain is controlled] and Spontaneous Breathing Trials (SBT): The ABC or Wake Up and Breath study [Girard, 2008; ABC study] found that daily SAT and SBT paired together improved patient outcomes (i.e. decreased time on the ventilator, reduced time spent in the ICU and hospital, and improved one-year survival)
• C-Choice of analgesia and sedation: avoid benzodiazepines [barnes 2016]; association between commonly prescribed sedative medications (ex. benzodiazepines---lorazepam is an independent factor for transition to delirium; less of a risk for other sedatives such as morphine, fentanyl, propofol [anes 2006; SICU/TICU benzos 2008]) and delirium; comfort first>>>then goal directed delivery of sedatives
• D-Delirium: assess, prevent and manage (see the assessment and monitoring section for details)

>"Repeated reorientation of patients >Provisions of cognitively stimulating activities for the patients multiple times a day >A nonpharmacological sleep protocol--minimize sleep deprivation [brummel] >Early mobilization activities >Timely removal of catheters and physical restraints >Use of eye glasses and magnifying lenses, hearing aids and earwax disimpaction >Early correction of dehydration >Use of a scheduled pain management protocol >Minimization of unnecessary noise/stimuli"

• E-Early mobility and exercise:

>" safe and feasible in critically ill patients" >"Early mobility decreases days of delirium [lancet 2009, Aust 2009], days on mechanical ventilation [lancet 2009, Aust, 2009], and ICU and hospital length of stay [morris 2008]. Functional outcomes are also improved with early mobility." [lancet, aust 2009] >"only intervention resulting in a decrease in days of delirium."

In addition to ABCDE model, Brummel et al [cite] advocate identifying and correcting individualized causal factors of delirium (ex. minimizing noise and unnecessary interruptions of sleep for a sleep deprived patient with ICU delirium).

Implications for Physical Therapy Practice

Physical therapists have an integral role in preventing and managing ICU delirium. Perhaps the most important measure is engaging patients in early mobilization, in conjunction with nurses, occupational therapists and physicians. Early mobilization in the ICU decreases the number of days on mechanical ventilation, decreased ICU and hospital length of stay and is the only intervention to date that has been shown to decrease the number of days of delirium. Frequent patient orientation, use of vision and hearing aids and family training/education are additional interventions that can be integrated into evaluation and treatment sessions. The CAM-ICU is a quick and easy tool for assessing and monitoring course of delirium across therapy sessions.

Differential Diagnosis

The multifactorial nature of delirium can make it easy to mistake for other brain conditions. The following conditions should also be considered as sources of altered consciousness and cognitive impairment for patients with suspected ICU delirium:

• Infectious (encephalitis, meningitis, UTI, pneumonia)
• Withdrawal (alcohol, barbiturates, benzodiazepines)
• Acute metabolic disorder (electrolyte imbalance, hepatic or renal failure)
• Trauma (head injury, postoperative)
• CNS pathology (stroke, hemorrhage, tumour, seizure disorder, Parkinson’s)
• Hypoxia (anemia, cardiac failure, pulmonary embolus)
• Deficiencies (vitamin B 12 , folic acid, thiamine)
• Endocrinopathies (thyroid, glucose, parathyroid, adrenal)
• Acute vascular (shock, vasculitis, hypertensive encephalopathy)
• Toxins, substance use, medication (alcohol, anesthetics, anticholinergics, narcotics)
• Heavy metals (arsenic, lead, mercury)

Further Reading

• ICU Delirium and Cognitive Impairment Study Group. For Medical Professionals-- ABCDEF's of prevention and safety. http://www.icudelirium.org/medicalprofessionals.html