Critical care- anaesthetics

1. General Health: exercise tolerance, cardiac risk
2. Systems review, PMHx, Medications
3. Previous anaesthetics, complications and family with complications
4. EtOH and smoking
5. Other recreational reugs (HIV and HepC)
6. Dentition (loose teeth, bridgework and crowns), obesity and mental status
7. Allergies and drug sensitivities
8. Gastric reflux and hiatus hernia symptoms
9. Hx of thromboembolic disease
10. Fasting status

Malignant hyperthermia.
It increases skeletal muscle oxidative metabolism in response to volatile gas anaesthetics and suxamethonium.
It overwhelms the body's capacity to supply oxygen, remove carbon dioxide, and regulate body temperature, eventually leading to circulatory collapse and death. Also rhabdomyolysis.

Minimum fast for clear liquids: 2hr
Breast milk: 4hr
Light meal, infant formula and other milk: 6hr

- Preferrably use and ETT (not LMA)
- If severe reflux (can't lie flat), give antacid prophylaxis, but might risk a difficult intubation

Beta-blockers, Ca2+ channel blockers and nitrates should be continued

Should be continued but some prefer to omit ACEi or ATII receptor blockers

Omit on morning of surgery

Continue but at 1/2 dose on morning of surgery

Continue

IV- rapid, pleasant. IV access whilst awake
Inhalational- no IV access req'd whilst awake. Easier to control and reverse (e.g. in airway obstruction). Slower, confusion, agitation.
(IM- ketamine)

Sevoflurane, desflurane (although not solely as it can induce a sympathetic response)
N2O if <2hrs and simple procedure

Advantages: Can use less volatile gas (important in someone frail or with e.g. heart failure)

Disadvantages: Increased PONV, inactivates the cobalamin form of vitamin B12 by oxidation, esp. in elderly (peripheral neuropathy), if there is a gap bubble, causes it to expand (bowel, pneumothorax, middle ear), Increases ICP

Look for chest rising and falling
Auscultate both sides for breath sounds
Mask fogging
Monitoring devices

Tounge, foreign body

Jaw thrust
Naso/oropharyngeal airway
Laryngeal mask
ETT

Approximately the length of the jaw

Naso is better tolerated and doesn't interfere with loose teeth or dentures, but it may cause bleeding

When the patient is spontaneously breathing, if cannot place an ETT and can't ventillate

ETT is the only definitive airway. Use if pt has reflux, sepsis, in emergency surgery (not fasted), when there is poor access to patient, if there is obstruction

M: 7.5
F: 7.0

Flexion of the lower cervical spine and extension of the upper cervical spine

1-4, based on how much of the uvula can be seen when looking into the patient's mouth.

Laryngoscope, gum elastic bougie (or stylet in paeds)

Watch chest rise and fall
Auscultate axillae
Look for fogging in the tube
Normal airway pressure cycle
Capnography
Fibre optic scope

It may go down one bronchus (R)

Hyperextension of the neck often occludes the airway (so neutral position is often more successful)

Non-fasted
Delayed emptying (pyloric obstruction, metabolic (DM), decreased gastric motillity)
Known reflux
Recent trauma
Increased intragastric pressure (intestinal obstruction, pregnancy)
Perioperative opioids
Topically anaesthetised airway

Indicated when there is a risk of aspiration
Involves preoxygenation, IV induction agent and suxamethonium with cricoid pressure

Cartillage is held between the thumb and middle finger and pressure is exerted with the index finger posteriorly

IV induction agent (thiopentone) and suxamethonium

Manual inline stabilisation.
One person hold head and crouches to one side. Collar may be flipped open. Cricoid pressure may be omitted if necessary but now it seems that there is no difference between 1 or 2 hands

Induction sedative agent
GABAa agonist at the gamma subunit (increases frequency of channel opening)
May be confused after cessation of prolonged infusion

Induction
GAGAa agonist at he beta subunit (increases channel opening time)
May get myoclonic movements, pain on injection, propofol infusion syndrome (cardiac failure, rhabdomyolysis, metabolic acidosis and renal failure and is often fatal)

Induction.
Barbituate. Positive allosteric modulator at GABAa and glycene receptors, increased chloride channel opening time
Pain

Increase heart rate
Muscarinic acetylcholine antagonist (vagal blockade at AV and SA node).
Decreased secretions and lowers oesophageal sphincter tone. Relaxes bronchial smooth muscle. (precent muscarinic side effects with neostigmine)

Acetylcholine
Nicotinic receptors

Sux is a cholinergic agonist. Not metabolised by acetylcholinesterase so depolarisation of endplate continues for longer inactivating the voltage-gated ion channel- impulses temporarilly cannot pass to motor endplate

Prevents depolarisation but combining reversibly with one or both alpha-subunits, preventing access to ACh to open the ion channel

Post op muscle pains
Increased intraocular pressure
Increases K+ 0.5
Bradycardias
Malignant hyperthermia

Neostigmine
Anticholinesterase inhibitor

A catheter inserted into a large vein.
Potential sites include: internal jugular, subclavian, femoral, external jugular, basillic/cephallic

Monitor CVP
Certain drugs (adrenaline, noradrenaline, dopamine, TPN)
Failed peripheral access
Sitting neurosurgery (to remove air that has been sucked into venous sinuses)

Infection
Damage to surrounding tissue
Pneumothorax (IJ)
Arrhythmias (if too far down IJ)
Arterial catheterisation
Haemorrhage

Combining different classes of analgesia

CVS: tachycardia, HT, Increased myocardial O2 consumption, venous stasis
Resp: weakened cough, decreased lung volumes, atelectasis, sputum retention
GI: decreased motillity, delayed gastric emptying
GU: urinary retention
Endocrine: stress response hormones released
Psychological

Self administration of IV opioids with a push buttin but cannot exceed that maximum toxic conc.
Potentially less opioid used and a sense of control.
Less work for the nurses
Doesn't necessarilly increase patient satisfaction, and sometimes afraid to use because of addiction.

Decreased respiratory drive
Pinpoint pupils
Sedation

Manage with naloxone

History of PONV
Perioperative opiate use
History of motion sickness
Female
Non-smoker

Dopamine antagonist

Dystonia

Serotonin receptor antagonist.

Hypotension, headache, flushing

Dopamine antagonist

Vasodilation, dypotension, dystonia

Steroid

Interacts with (?)cholinesterases to increase weakness in myasthenia gravis

Block conduction of nerve via sodium channel

Decreases vascular reabsorption
Increases duration of action by making more drug available
Decreases haemorrhage

Lignocaine: fast onset, medium acting
Bupivacaine: medium onset, long duration
Ropivacaine: medium onset, long acting

Severe: death, respiratory arrest, arrhythmias, CV collpse
Moderate: altered LOC, convulsions
Mild: perioral tingling, metallic taste, tinnitus, visual disturbance, slurred speech