Unconsciousness

Causes of Unconsciousness

Any factor sufficiently adversely effecting the function of the brain or brain stem.

Metabolic

Hyper/hypoglycaemia Uraemia, eg. chronic renal failure

Hepatic failure Hypoadrenal disease (Addisons)

Hypopituitorism Electrolyte imbalance

Myxoedema Respiratory failure - cerebral hypoxia

Infective

CNS meningitis encephalitis abscess

Systemic septicaemia malaria, (falciparam)

Vascular

Reduced BP Cerebral thrombosis/embolism/haemorrhage

Neurological

SOL CVA Sterile meningitis

Psychiatric

Narcolepsy Catolepsy Catotonic stupor Other stupors

Syncope

Vasovagal Cardiac - Stoke Adams Subclavian steal

Toxins

C₂H₅OH Hypnotics, Benzodiazepines, barbiturates

Opiates Aspirin/paracetamol Carbon Monoxide

Trauma

Extra dural Sub dural Sub ar achnoid Sudden blow to head or jaw

Head Injury

Raised Intracranial pressure Space occupying lesion

Hydrocephalus Coning

Hypo/hyperthermia

Gradual onset Acute onset

Epilepsy

Grand Mal, aura - tonic - clonic - coma

Classify the following causes of unconsciousness using the subtitles already used. In addition state if the cause is cranial or extracranial

barbiturate overdose, carbon monoxide poisoning, hypoglycaemia, hyperglycaemia, cerebral hypoxia, encephalopathy, sub-arachnoid haemorrhage, renal failure, hepatic failure, CO₂ retention, hypo or hypercalcaemia, hypoadrenalism, hypopituitarism, hypothyroidism, hyponatraemia, metabolic acidosis, hypothermia, hyperthermia, closed head injury, open head injury, epilepsy, cerebral malaria, brain stem infarct or haemorrhage, SOL causing RICP, electric shock, Narcolepsy, Catolepsy, Catotonic stupor, depressed skull fracture, brain haemorrhage, stroke, brain neoplasm, electric shock, systemic haemorrhage

External factors outside the brain which may influence cerebral function

- Infection eg.

- Metabolic eg.

- Trauma eg.

- Perfusion eg.

- Nutrition eg.

- Psychiatric eg.

- Oxygenation eg.

- Environmental eg.

- Other path eg.

Internal factors in the brain which may influence cerebral function

neuronal and synaptic function, these may be influenced by;

- direct effects on brain stem

-

Consciousness

Conscious

* capable of responding to stimuli * awake/alert

* aware of the external environment * a clear state of awareness

* not unconscious or subconscious * a state of arousal

The complete awareness of self and environment with appropriate response to stimuli

Aroused state depends on the activity of the reticular formation

The reticular formation increases global cortical activity so is also referred to as the reticular activating system, (RAS)

Stimulation of the pons and midbrain produces widespread activity in the cortex

Stimulation of the medulla caused activation of specific parts of the thalamus and specific areas of the cortex.

Pons and midbrain generate consciousness

Medulla produces arousal form deep sleep

Once awake the cortex and the RAS continue to stimulate each other through feedback systems generating consciousness

The RAS is the physical basis of consciousness

The RAS sifts and selects information to pass on to the cortex

The level of consciousness seems to depends on the number of feedback circuits operating at a particular time, eg alertness, attentiveness, relaxation, inattention

Consciousness may be stimulated by amphetamines or cocaine and depressed by alcohol, hypnotics or anaesthetics

Anaesthesia - due to the large number of connecting synaptic connections and direct effects on axons

Damage or disease may produce a lack of consciousness called coma

Unconsciousness may be also be caused by interference with impulses from the reticular activating system or other failure of the cortical neurones to respond to incoming impulses.

Neurones require a constant supply of oxygen and glucose in order to function, even a few seconds oxygen deprivation may lead to a loss of consciousness.

Inactivation of the RAS produces a state of partial consciousness called sleep which follows a circadian rhythm

There are different levels of consciousness and different levels of sleep

Reticular formation

Throughout the brain stem - medulla, pons and midbrain is a group of widely scattered dense network of short axoned non - myelinated neurones (a continuation of the spinal cord) referred to as the reticular formation. The neurones of the RF receive and integrate input from the upper areas of the brain and from the spinal cord below. The neurones also send impulses to all levels of the CNS, and thus ideally suited to govern the activity of the CNS.

Spinal sensory nerves ----------- ascending reticular formation ----------------- upper areas of the brain

Sleep and Coma

Destruction or embarrassment of the Reticular Formation may lead to deep sleep, insensibility to sensory stimuli and immobility.

We wake because of the activation of the reticular formation by sensory impulses

Coma may be considered to be brain failure

The unconscious mind in psychiatry;

Unconsciousness

A state of complete or partial unawareness

Unconsciousness - not rousable

Sleep - rousable

Coma - prolonged unconsciousness

Causes of short term unconsciousness;

Causes of long term unconsciousness;

Levels of unconsciousness

Alert

Normal consciousness

Automatism

Aware of surroundings May be unable to remember actions later

Possible abnormal mood, may show defects of memory and judgement

Confusion

Loss of ability to speak and think in a logical coherent fashion

Responds to simple orders May be disorientated for time and space

Delirium/Acute confusion with adgitation

Characterised by restlessness and possible violence Not capable to rational thought

May be troublesome and not comply with simple orders

Stupor

Quite and uncommunicative Remains conscious but sits or lies with a glazed expression

Does not respond to orders Bladder and rectal incontinence occur

More serious than the previous wild stage

Semi-coma

A twilight stage Patients often pass fitfully into unconsciousness

May be aroused to the stuporosed state by vigorous stimulation

Coma

Patient deeply unconscious

Can not be roused and does not wake up with vigorous stimulation

Arrange the following in order or reduced consciousness,

consciousness, clouding of consciousness, sleep, stupor, confusion, delirium, coma, alert, loss of ability to abstract, semi-comatosed

Less common conditions

* locked in syndrome * chronic vegetative state

Assessment

* ABC * Depth of coma

* Med alert * Evidence of trauma

* Serum glucose * Temperature

* Skin, colour, texture, injection sites. * Breath

* Respirations * Head and neck

* Pupils * Fundi

* Occular movements * Motor response

* History/Witness

* CT/MRI * CSF

* Blood and urine, drugs screen, biochemistry, metabolic and endocrine, cultures

Effects of unconsciousness

Loss of sensory and responsive mechanisms Loss of normal self protective mechanisms

Complications of immobility Incontinence

Loss of reflexes, eg swallowing, cough, risk of aspiration pneumonia

Management

Lateral position

Removal of anything which could obstruct the airway Backward elevation of the mandible

Respiratory observation and support

Respiratory support

Loss of cough and gag reflex - intubate PRN Pulse oximetry/blood gases

Rate and volumes IPPV ?

Cardiovascular support

P and BP - ? shock Urine output CVP Cardiac monitor?

Basic care - skin, oral, eyes, fluids, nutrition, sphincters