UNCONSCIOUSNESS AND COMA

The central reticular formation, which extends from the brainstem to the thalamus, influences the state of arousal. It consists of clusters of inter-connected neurones throughout the brainstem, with projections to the spinal cord, the hypothalamus, the cerebellum and the cerebral cortex.

Coma is a state of unconsciousness from which the patient cannot be roused. A stuporous patient is sleepy but will respond to vigorous stimulation. The Glasgow Coma Scale (GCS; Table 17.6) is a simple grading system used to assess the level of consciousness. It is easy to perform and provides an objective assessment of the patient. Serial measurements are used to detect a deterioration which may indicate the need for further investigation or treat-ment. A very rapid assessment in an unstable patient is obtained using the AVPU score: Alert, responds to Voice, responds to Pain, Unresponsive. A

Table 17.6 Glasgow Coma Scale

Category

Score

Eye opening (E)

Spontaneous

4

To speech

3

To pain

2

None

1

Best verbal response (V)

Orientated

5

Confused

4

Inappropriate

3

Incomprehensible

2

None

1

Best motor response (M)

Obeying commands

6

Localizing - use limb to resist a painful stimulus

5

Limb withdrawing

4

Limb flexing

3

Limb extending

2

None

1

The scores in each categoiy are added up to give an overaỉỉ score, which may vaiy from 3 (in the deepỉy comatose patient) to 15

patient responding to pain only, broadly corresponds to a GCS of less than 8.

Coma must be differentiated from persistent vegetative State (PVS, a State of wakefulness in which sleep-wake cycles persist but without detectable awareness), brain death (p. 742) in which there is no possibility of recovery, and the locked-in syndrome (p. 747). Patients in coma may progress to a PVS.

Aetiology

Altered consciousness is produced by three types of processes:

■ Diffuse brain dysfunction due to severe metabolic, toxic or neurological disorders

■ Brainstem lesions which damage the reticular formation

■ Pressure effect on the brainstem such as a cortical or cerebellar lesion which compresses the brainstem, inhibiting the ascending reticular acti-vating system.

Table 17.7 Principal causes of coma

Diffuse brain dysfunction
Drug overdose, alcohol excess
CO poisoning, anaesthetic gases,
Hypo- or hyperglycaemia
Hypo- or hypercalcaemia – if severe
Hypo- or hypernatraemia – if severe
Hypoadrenalism
Severe uraemia
Hepatocellular failure
Metabolic acidosis
Respiratory failure with CO2 retention
Hypoxicμschaemic brain injury
Subarachnoid haemorrhage
Hypertensive encephalopathy
Encephalitis, cerebral malaria, septicaemia
Direct effect within the brainstem
Haemorrhageμnfarction
Tumour
Demyelination, e.g. multiple sclerosis
Wernicke–Korsakoff syndrome
Trauma
Pressure effect on brainstem
Tumour
Haemorrhageμnfarction
Abscess
Encephalitis

Assessment

In all patients presenting in coma a history should be obtained from any witnesses and relatives (e.g. speed of onset of coma, diabetes, drug or alcohol abuse, past medical history and medication).

Immediate assessment takes only seconds, but is essential:

■ Airway. Clear the airway of vomit, secretions and foreign bodies. A patient not protecting their airway may need intubating.

■ Breathing. Assess for cyanosis, respiratory rate (normal 12-20), use of accessory muscles of respiration (p. 506), chest auscultation, oxygen saturation by pulse oximetry. Consider intubation and ventilation.

■ Circulation. Assess pulse, blood pressure and capillary refill (p. 576).

■ Disability. Conscious level using the Glasgow coma score.

■ Exposure. Full examination of the patient, e.g. head injury, abdominal examination.

Further assessment A full general examination should be carried out. Clues to the cause of coma should be looked for, e.g. the smell of alcohol or ketones (in diabetic ketoacidosis) on the breath, needle-track marks in a drug abuser, or a Medic-Alert bracelet, as carried by some diabetic people and patients on steroid-replacement therapy.

The neurological examination must include:

■ Head and neck. Look for evidence of trauma, bruits and neck stiffness (indicating meningitis or subarachnoid haemorrhage).

■ Pupils. Record size and reaction to light:

■ A unilateral fixed dilated pupil indicates herniation of the temporal lobe (‘coning') through the tentorial hiatus and compression of the third cranial nerve (p. 731). This indicates the need for urgent neu-rosurgical intervention.

■ Bilateral fixed dilated pupils are a cardinal sign of brain death. They also occur in deep coma of any cause, but particularly coma caused by barbiturate intoxication or hypothermia.

■ Pinpoint pupils are seen with opiate overdose or with pontine lesions that interrupt the sympathetic pathways to the dilator muscle of the pupil.

■ Midpoint pupils that react to light are characteristic in coma of meta-bolic origin and coma caused by most CNS-depressant drugs.

■ Fundi. Look for papilloedema, which indicates raised intracranial pressure.

■ Eye movements. Conịugate lateral deviation of the eyes indicates ipsilat-eral cerebral haemorrhage or infarction (the eyes look away from the paralysed limbs), or a contralateral pontine lesion (towards the paralysed limbs). Passive head rotation normally causes conjugate ocular deviation in the direction opposite to the induced head movement (doll's head reflex). This reflex is lost in very deep coma and is absent in brainstem lesions.

■ Motor responses. Asymmetry of spontaneous limb movements, tone and reflexes indicates a unilateral cerebral hemisphere or brainstem lesion. The plantar responses are often both extensor in coma of any cause.

Investigations

In many cases the cause of coma will be evident from the history and exami-nation, and appropriate investigations should then be carried out. However, if the cause is still unclear, further investigations will be necessary.

Blood and urine tests

■ Serum and urine for drug analysis, e.g. salicylates

■ Serum for urea and electrolytes, liver biochemistry and calcium

■ Blood glucose by immediate Stix testing and then formal laboratory testing

■ Arterial blood gases

■ Thyroid function tests and serum cortisol

■ Blood cultures.

Radiology CT of the head may indicate an otherwise unsuspected mass lesion or intracranial haemorrhage.

CSF examination If a mass lesion is excluded on CT, lumbar puncture (p. 737) is performed if subarachnoid haemorrhage or meningoencephalitis is suspected.

Management

The immediate management consists of treatment of the cause, careful nursing, meticulous attention to the airway and frequent observation to detect any change in vital function. Naloxone (400 μg i.v, p. 602) is given if opiate poisoning (pinpoint pupils, hypoventilation, drug addict) is suspected. Fluma-zenil (p. 600) is given if coma is a complication of benzodiazepines. Give thiamine 100 mg i.v. to alcohol dependents or malnourished patients.

Prognosis

The outlook depends upon the cause of coma. A cause must be established before decisions are made about withdrawing supportive care.

Brain death

Brain death means the irreversible loss of the capacity for consciousness, combined with the irreversible loss of the capacity to breathe. Two independ-ent senior medical opinions are required for the diagnosis to be made. The three main criteria for diagnosis are as follows:

■ Irremediable structural brain damage. A disorder that can cause brain-stem death, e.g. intracranial haemorrhage, must have been diagnosed with certainty. Patients with hypothermia, significant electrolyte imbal-ance or drug overdose are excluded, but may be reassessed when these are corrected

■ Absent motor responses to any stimulus. Spinal reflexes may be present

■ Absent brainstem function, demonstrated by:

■ Pupils fixed and unresponsive to light

■ Absent corneal, gag and cough reflexes

■ Absent doll's head reflex (p. 741)

■ Absent caloric responses: ice-cold water run into the external auditory meatus causes nystagmus when brainstem function is normal

■ Lack of spontaneous respiration.

In suitable cases, and provided the patient was carrying a donor card and/or the consent of relatives has been obtained, the organs of those in whom brainstem death has been established may be used for transplantation.

Ebook Essentials of Kumar and Clark's Clinical Medicine, 5e

1. Ethics and communication

Ethics and communication

2. Infectious diseases

Infectious diseases

3. Gastroenterology and nutrition

Gastroenterology and nutrition

4. Liver, biliary tract and pancreatic disease

Liver, biliary tract and pancreatic disease
LIVER BIOCHEMISTRY AND LIVER FUNCTION TESTS
SYMPTOMS AND SIGNS OF LIVER DISEASE
JAUNDICE
HEPATITIS
NON - ALCOHOLIC FATTY LIVER DISEASE (NAFLD)
CIRRHOSIS
COMPLICATIONS AND EFFECTS OF CIRRHOSIS
LIVER TRANSPLANTATION
TYPES OF CHRONIC LIVER DISEASE AND CIRRHOSIS
PRIMARY SCLEROSING CHOLANGITIS
BUDD - CHIARI SYNDROME
LIVER ABSCESS
LIVER DISEASE IN PREGNANCY
LIVER TUMOURS
GALLSTONES
THE PANCREAS
CARCINOMA OF THE PANCREAS
NEUROENDOCRINE TUMOURS OF THE PANCREAS

5. Haematological disease

Haematological disease
ANAEMIA
Assessment and treatment of suspected neutropenic sepsis
HAEMOLYTIC ANAEMIA
INHERITED HAEMOLYTIC ANAEMIAS
ACQUIRED HAEMOLYTIC ANAEMIA
MYELOPROLIFERATIVE DISORDERS
THE SPLEEN
BLOOD TRANSFUSION
THE WHITE CELL
HAEMOSTASIS AND THROMBOSIS
THROMBOSIS
THERAPEUTICS

6. Malignant disease

Malignant disease
MYELOABLATIVE THERAPY AND HAEMOPOIETIC STEM CELL TRANSPLANTATION
THE LYMPHOMAS
THE PARAPROTEINAEMIAS
PALLIATIVE MEDICINE AND SYMPTOM CONTROL

7. Rheumatology

Rheumatology
COMMON INVESTIGATIONS IN MUSCULOSKELETAL DISEASE
COMMON REGIONAL MUSCULOSKELETAL PROBLEMS
BACK PAIN
OSTEOARTHRITIS
INFLAMMATORY ARTHRITIS
THE SERONEGATIVE SPONDYLOARTHROPATHIES
Clinical features, Investigations
INFECTION OF JOINTS AND BONES
AUTOIMMUNE RHEUMATIC DISEASES
SYSTEMIC INFLAMMATORY VASCULITIS
DISEASES OF BONE
THERAPEUTICS

8. Water, electrolytes and acid–base balance

WATER AND ELECTROLYTE REQUIREMENTS
BODY FLUID COMPARTMENTS
REGULATION OF BODY FLUID HOMEOSTASIS
PLASMA OSMOLALITY AND DISORDERS OF SODIUM REGULATION
DISORDERS OF POTASSIUM REGULATION
DISORDERS OF MAGNESIUM REGULATION
DISORDERS OF ACID - BASE BALANCE
THERAPEUTICS

9. Renal disease

Renal disease
INVESTIGATION OF RENAL DISEASE
GLOMERULAR DISEASES
NEPHROTIC SYNDROME
URINARY TRACT INFECTION
TUBULOINTERSTITIAL NEPHRITIS
HYPERTENSION AND THE KIDNEY
RENAL CALCULI AND NEPHROCALCINOSIS
URINARY TRACT OBSTRUCTION
ACUTE RENAL FAILURE/ACUTE KIDNEY INJURY
CHRONIC KIDNEY DISEASE
RENAL REPLACEMENT THERAPY
CYSTIC RENAL DISEASE
TUMOURS OF THE KIDNEY AND GENITOURINARY TRACT
DISEASES OF THE PROSTATE GLAND
TESTICULAR TUMOUR
URINARY INCONTINENCE

10. Cardiovascular disease

COMMON PRESENTING SYMPTOMS OF HEART DISEASE
INVESTIGATIONS IN CARDIAC DISEASE
CARDIAC ARRHYTHMIAS
HEART FAILURE
ISCHAEMIC HEART DISEASE
RHEUMATIC FEVER
VALVULAR HEART DISEASE
PULMONARY HEART DISEASE
MYOCARDIAL DISEASE
CARDIOMYOPATHY
PERICARDIAL DISEASE
SYSTEMIC HYPERTENSION
ARTERIAL AND VENOUS DISEASE
ELECTRICAL CARDIOVERSION
DRUGS FOR ARRHYTHMIAS
DRUGS FOR HEART FAILURE
DRUGS AFFECTING THE RENIN - ANGIOTENSIN SYSTEM
NITRATES, CALCIUM - CHANNEL BLOCKERS AND POTASSIUM - CHANNEL ACTIVATORS

11. Respiratory disease


Respiratory disease
TUBERCULOSISnd
DIFFUSE DISEASES OF THE LUNG PARENCHYMA
OCCUPATIONAL LUNG DISEASE
CARCINOMA OF THE LUNG
DISEASES OF THE CHEST WALL AND PLEURA
DISORDERS OF THE DIAPHRAGM

12. Intensive care medicine

Intensive care medicine

13. Drug therapy, poisoning, and alcohol misuse

Drug therapy, poisoning, and alcohol misuse

14. Endocrine disease

Endocrine disease
PITUITARY HYPERSECRETION SYNDROMES
THE THYROID AXIS
MALE REPRODUCTION AND SEX
FEMALE REPRODUCTION AND SEX
THE GLUCOCORTICOID AXIS
THE THIRST AXIS
DISORDERS OF CALCIUM METABOLISM
DISORDERS OF PHOSPHATE CONCENTRATION
ENDOCRINOLOGY OF BLOOD PRESSURE CONTROL
DISORDERS OF TEMPERATURE REGULATION
THERAPEUTICS

15. Diabetes mellitus and other disorders of metabolism

DIABETES MELLITUS
DIABETIC METABOLIC EMERGENCIES
COMPLICATIONS OF DIABETES
SPECIAL SITUATIONS
HYPOGLYCAEMIA IN THE NON - DIABETIC
DISORDERS OF LIPID METABOLISM
THE PORPHYRIAS

16. The special senses

THE EAR
THE NOSE AND NASAL CAVITY
THE THROAT
THE EYE

17. Neurology

COMMON NEUROLOGICAL SYMPTOMS
COORDINATION OF MOVEMENT
THE CRANIAL NERVES
COMMON INVESTIGATIONS IN NEUROLOGICAL DISEASE
UNCONSCIOUSNESS AND COMA
STROKE AND CEREBROVASCULAR DISEASE
EPILEPSY AND LOSS OF CONSCIOUSNESS
NERVOUS SYSTEM INFECTION AND INFLAMMATION
HYDROCEPHALUS
HEADACHE, MIGRAINE AND FACIAL PAIN
SPINAL CORD DISEASE
DEGENERATIVE NEURONAL DISEASES
DISEASES OF THE PERIPHERAL NERVES
MUSCLE DISEASES
MYOTONIAS
DELIRIUM
THERAPEUTICS

18. Dermatology

Dermatology

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