From the Guidelines
For increased confusion and sedation, a comprehensive diagnostic approach is necessary, and laboratory tests should be guided by the patient's individual medical, neuropsychiatric, and risk profile, as recommended by the Alzheimer's Association clinical practice guideline 1. When evaluating a patient with increased confusion and sedation, it is essential to consider a broad range of potential underlying causes. The following laboratory tests are recommended to rule out common underlying issues:
- Complete Blood Count (CBC): to check for infection or anemia
- Comprehensive Metabolic Panel (CMP): assesses electrolytes, kidney and liver function
- Thyroid Stimulating Hormone (TSH): screens for thyroid dysfunction
- Blood glucose: to rule out hypo- or hyperglycemia
- Urinalysis and urine culture: to check for urinary tract infection
- Blood cultures: if systemic infection is suspected
- Toxicology screen: including alcohol level and specific medication levels if relevant
- Ammonia level: especially if liver disease is suspected
- Vitamin B12 and folate levels: deficiencies can cause cognitive changes These tests cover the most common metabolic, infectious, toxic, and endocrine causes of altered mental status. The CBC and CMP provide a broad overview of the patient's health status, while targeted tests like TSH and toxicology screen for specific issues. Urinary tract infections are a common cause of confusion in older adults, hence the inclusion of urinalysis. Blood glucose is crucial as both high and low levels can cause altered mental status. If initial results are inconclusive, further testing or neuroimaging may be necessary, as suggested by the American Heart Association/American Stroke Association stroke council 1. Always correlate lab results with the patient's clinical presentation and medical history for accurate interpretation.
From the FDA Drug Label
Essential Laboratory Tests Some patients on lorazepam have developed leukopenia, and some have had elevations of LDH. As with other benzodiazepines, periodic blood counts and liver-function tests are recommended for patients on long-term therapy
The laboratory tests indicated to rule out underlying causes of increased confusion and sedation are:
- Periodic blood counts
- Liver-function tests 2
From the Research
Laboratory Tests to Rule Out Underlying Causes
To determine the underlying causes of increased confusion and sedation, several laboratory tests can be indicated. These tests can help identify potential medical conditions that may be contributing to the patient's symptoms.
- Arterial blood gas (ABG) analysis can be used to assess respiratory function and detect any abnormalities in oxygenation or ventilation 3
- Complete blood count (CBC) and blood chemistry tests can help identify any underlying infections, electrolyte imbalances, or other conditions that may be contributing to confusion and sedation
- Neuroimaging studies, such as computed tomography (CT) or magnetic resonance imaging (MRI), can be used to rule out any structural abnormalities in the brain that may be causing increased intracranial pressure (ICP) 4
- Pulse oximetry monitoring can be used to assess oxygen saturation, but it may not be adequate to detect respiratory acidosis in patients receiving supplemental oxygen 3
Additional Tests
Depending on the patient's medical history and physical examination, additional tests may be indicated to rule out other potential underlying causes of increased confusion and sedation. These may include:
- Electrolyte panels to assess for any imbalances that may be contributing to confusion or sedation
- Liver function tests to assess for any hepatic dysfunction that may be contributing to encephalopathy
- Toxicology screens to assess for any substance-related causes of confusion or sedation
- Thyroid function tests to assess for any thyroid dysfunction that may be contributing to confusion or sedation
Considerations
It is essential to consider the patient's overall medical condition and potential risk factors for impaired respiratory function when selecting laboratory tests to rule out underlying causes of increased confusion and sedation. For example, patients with a history of respiratory disease or those who are receiving procedural sedation and analgesia in the cardiac catheterization laboratory may be at higher risk for impaired respiratory function 5.