CN LANGE - Coma I Flashcards
Coma results from …?
Disturbance in the function of EITHER the brainstem reticular activating system above the mid pons OR of BOTH cerebral hemispheres.
Emergency management of the comatose patient - Immediately:
- Ensure adequacy of airway, ventilation, and circulation. 2. Draw blood for serum glucose, electrolytes, liver and renal function tests, PT, PTT, and CBC. 3. Start IV and administer 25g of dextrose, 100mg of thiamine, and 0.4-1.2mg of naloxone IV. 4. Treat seizures.
Emergency management of the comatose patient - Next:
- If signs of meningeal irritation are present, perform LP to rule out meningitis. Obtain a history if possible. 2. Perform detailed general physical and neurologic examination. 3. Order CT scan of head if history or findings suggest structural lesion or SAH.
Emergency management of the comatose patient - Later:
- ECG. 2. Correct hyper/hypothermia. 3. Correct severe acid-base and electrolyte abnormalities. 4. CXR. 5. Blood and urine tox studies. 6. EEG.
Adequacy of ventilation can be established by …?
- The absence of cyanosis. 2. A respiratory rate greater than 8/min. 3. The presence of breath sounds on auscultation of the chest. 4. The results of arterial blood gas studies.
Flumazenil ( GABA antagonist to reverse sedation) 1 to 10mg IV, may be useful when benzodiazepine OD contributes to coma. However, …?
It should NOT be used in patients with: 1. History of seizures. 2. Chronic benzodiazepine use. 3. Suspected co-ingestion of tri- or tetracyclic antidepressants. ( anatgonises the effect of benzo - reducing seizure threhold)
Suspect ingestion of TCAs if?
The ECG shows: 1. Sinus tachycardia at a rate of 130/min or more. 2. QTc interval greater than 0.5sec. 3. QRS duration greater than 0.1sec.
History - The most crucial aspect of history is …?
The TIME OVER WHICH COMA DEVELOPS.
History - A sudden onset of coma suggests:
Vascular origin –> Especially a brainstem stroke or SAH.
History - Rapid progression from hemispheric signs, such as hemiparesis, hemisensory deficit, or aphasia, to coma within MINUTES to HOURS is characteristic of …?
INTRACEREBRAL HEMORRHAGE.
History - A more protracted course leading to coma (days to a week or more) is seen with:
- Tumor. 2. Abscess. 3. Chronic subdural hematoma.
History - Coma preceded by a confusional state or agitated delirium, without lateralizing signs or symptoms, is probably due to …?
A metabolic derangement or infection (meningitis, encephalitis).
Metabolic coma - DDx - Respiratory acidosis:
- Sedative drug intoxication. 2. Pulmonary encephalopathy - causes coma when arterial ph falls under 7.20 and paCO2 goes over 80mmHg)
Metabolic coma - DDx - Respiratory alkalosis:
- Hepatic encephalopathy. 2. Salicylate intoxication - result of ingestion of chemicals metabolised to salicylate e.g. asprin OD - nausea/vomiting/dizziness - hyperventilation -Resp Alkalosis - develop metabolic acidosis later on 3. Sepsis.
Metabolic coma - DDx - Metabolic acidosis:
- DKA. 2. Uremic encephalopathy - acquired toxic syndrome characterised by delirium in end stage renal disease 3. Lactic acidosis - build up of lactate due to nausea and vomiting 4. Methanol intoxication. 5. Ethylene glycol intoxication. 6. Isoniazid intoxication ( OD of antiobiotic drug for TB) 7. Salicylate intoxication. 8. Sepsis (terminal).
Metabolic coma - DDx - Metabolic alkalosis:
Coma unusual.
General physical examination - Signs of trauma - Inspection of the head may reveal signs of basilar skull fracture, including:
- Raccoon eyes - Periorbital ecchymoses. 2. Battle sign. 3. Hemotympanum. 4.CSF rhinorrhea or otorrhea.
Periorbital ecchymoses
battle sign
haemotympanum
CSF rhinorrhea
Cerebrospinal fluid (CSF) rhinorrhea is a condition where the protective fluid that surrounds the brain finds its way into the nose and sinuses, often appearing as a very watery runny nose. Most cases of CSF rhinorrhea occur after major accidents where the bones of the face and skull experience significant trauma
CSF rhinorrhea must be distinguished from other causes of rhinorrhea, such as allergic rhinitis:
- Glucose concentration does NOT reliably distinguish CSF from nasal mucus. 2. Beta-2 transferrin is UNIQUE to CSF, and its presence documents a CSF source of rhinorrhea.
Hypothermia occurs in coma caused by:
- Ethanol or sedative drug intoxication. 2. Hypoglycemia. 3. Wernicke encephalopathy. 4. Hepatic encephalopathy. 5. Myxedema.
Coma with hyperthermia is seen in:
- Heat stroke. 2. Status epilepticus. 3. Malignant hyperthermia related to inhalational anesthetics. 4. Anticholinergic drug intoxication. 5. Pontine hemorrhage. 6. Certain hypothalamic lesions.
General exam - Signs of meningeal irritation:
- Can be invaluable in the prompt diagnosis of meningitis or SAH. 2. BUT these signs are lost in deep coma, so their absence does NOT exclude these conditions.
General exam - Optic fundi - May reveal:
Papilledema or retinal hemorrhages compatible with chronic or acute HTN, or an elevation in intracranial pressure.
General exam - Optic fundi - What finding in an adult strongly suggest SAH?
Subhyaloid (superficial retinal) hemorrhages.
Neurologic exam:
The key to ETIOLOGIC DIAGNOSIS in the comatose patient.
Neurologic exam - What should be evaluated in detail?
- Pupillary size + reactivity. 2. Reflex eye movements (oculocephalic, oculovestibular reflexes). 3. Motor response to pain.
Pupils - Normal:
Typically 3-4mm in diameter (larger in children, smaller in elderly).
Normally reactive pupils in a comatose patient are characteristic of a …?
METABOLIC cause.
Thalamic pupils:
Slightly smaller (2mm) reactive pupils –> Early stages of thalamic compression from mass lesions, perhaps because of interruption of the DESCENDING SNS PATHWAYS.
Fixed, dilated pupils:
>7mm + fixed (unreactive to light) usually result from compression of the CN III (and associated SNS, pupillodilator fibers) anywhere along its course, from the midbrain to the orbit, but may also be seen in anticholinergic or SNS drug intoxication.
The MCC of a fixed dilated pupil in a comatose patient is …?
Transtentorial herniation of the medial temporal lobe from a supratentorial mass.
Fixed, midsized pupils:
- Pupils fixed at approx. 5mm in diameter are the result of brainstem damage at the MIDBRAIN level, which interrupts BOTH sympathetic pupillodilator, and parasympathetic, pupilloconstrictor nerve fibers.
Pinpoint pupils:
1-1.5mm in a comatose patient usually indicate opioid OD or, less commonly, a focal structural lesion in the pons.
Pinpoint pupils - How to distinguish opioid OD from focal structural lesion in the pons?
- Administration of naloxone. 2. Associated defects in horizontal eye movements that usually accompany pontine lesions.
Pinpoint pupils may appear unreactive to light except when …?
Viewed with a magnifying glass.
Pinpoint pupils can also be caused by …?
- Organophosphate poisoning. 2. Miotic eye drops. 3. Neurosyphilis (Argyll Robertson pupils).
Asymmetric pupils - Anisocoria:
Difference of 1mm or less in diameter is a normal finding that occurs in 20% of the population. –> Pupils constrict to a similar extent in response to light + extraocular movements are unimpaired.
Asymmetric pupils - A pupil that constricts less rapidly or to a lesser extent than its contralateral fellow usually implies …?
A structural lesion affecting the midbrain, oculomotor nerve, or eye.
Neurologic signs in coma with downward transtentorial herniation - In the early diencephalic phase:
- The pupils are small (approx. 2mm in diameter) + reactive. 2. Reflex eye movements are intact. 3. The motor response to pain is purposeful or semipurposeful (localizing) and often asymmetric.
Neurologic signs in coma with downward transtentorial herniation - In the late diencephalic phase:
Similar findings as in the early diencephalic phase, EXCEPT –> Painful stimulation results in decorticate (flexor) posturing, which may also be asymmetric.