1. Depth of coma. Assess using GCS.
2. Ocular and motor responses. Assess the following to help determine whether etiology is structural or medical. Asymmetry points to a structural lesion.
a. Pupillary size. Normal or asymmetric?
b. Pupillary reflex. Fixed or reactive?
c. Extraocular movements. Normal, asymmetric, or absent?
d. Motor response to pain. Decorticate, decerebrate, or flaccid?
3. Respiratory pattern. Identification of abnormal patterns of respiration can help differentiate a structural from a medical cause of coma (see Figure I-1, p. 33).
a. Cheyne-Stokes respiration. Implies dysfunction of structures deep in both cerebral hemispheres or diencephalon; usually seen in metabolic encephalopathy.
b. Central neurogenic hyperventilation. May occur with lesions of midbrain and pons.
c. Cluster breathing. May result from primary or secondary brainstem lesions.
d. Ataxic breathing. May result from primary disruption of medullary respiratory centers.
5. Neurologic findings. Perform a thorough neurologic exam.
6. Smell of patient's breath. May reveal alcohol intoxication or diabetic ketoacidosis.
7. Signs of trauma. Boggy scalp swelling, Battle sign, raccoon eyes, retinal hemorrhages, hemotympanum, bruises, hematomas.
B. Laboratory Data
2. Serum electrolytes. Identify electrolyte abnormalities that could cause seizures (Na+ and Ca2+), as well as acidosis (bicarbonate) or uremia (BUN and creatinine).
3. Liver function tests. Reveal presence of hepatic failure.
4. Serum ammonia. Elevated level is associated with common inborn errors of metabolism or liver failure.
5. Serum or urine drug screening. Although limited, can identify potential toxins.
6. Anticonvulsant drug levels. Obtain in patients with known seizure disorders.
7. CBC, differential, blood and urine cultures. Obtain in febrile patients or whenever sepsis or CNS infection is likely. CBC is also helpful in evaluation of patients who have sickle cell disease or who may have hemolytic uremic syndrome.
8. Cerebrospinal fluid evaluation (cell count, chemistry, and culture). Obtain whenever CNS infection or sepsis is suspected. To avoid the risk of cerebral herniation, consider obtaining CT scan of the head before performing lumbar puncture in patients with suspected structural CNS lesions or increased intracranial pressure. 9. ABGs. Helps tailor degree of hyperventilation. Radiographic and Other Studies
1. CT scan of head. Obtain emergently whenever increased intracranial pressure or presence of a structural lesion is suspected. Obtain in all comatose patients with coma of unclear etiology.
2. Skeletal survey. Obtain in children younger than 3 years of age who may have suffered inflicted injuries or child abuse.
3. ECG. May be helpful in management of certain ingested substances or toxins.
V. Plan. Management is similar to that of a patient with altered mental status, discussed in Chapter 6. See Figure I-1 on p. 33, which depicts a systematic approach to patient care.
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