Anaesthesia Preparation Flashcards
(44 cards)
1
Q
What are the stages of general anaesthesia?
A
- Stage 1 → analgesia, induction to LoC
- Stage 2 → excitatory phase, from LoC to onset of automatic breathing
- Stage 3 → surgical anaesthesia, from onset of automatic breathing to resp paralysis
- Stage 4 → overdose, from stoppage of respiration to death where medullar pralysis occurs
Can compare to ‘alcohol intoxication’: dizzy and delightful → drunk and disorderly → dead drunk → dangerously deep
2
Q
Where do anaesthetists work, in a hospital?
A
- Theatres
- Labour ward
- Other procedural areas
- Interventional radiology
- Intensive Care Unitu (ICU)
- Post-anaesthesia care unit (PACU)
- Pain management: acute and chronic
Also: cardiac arrest team, research, sim, admin, education, management
3
Q
What are the 3 main types of anaesthesia?
A
- General
- Regional
- Local
4
Q
What are advantages of general anaesthesia?
A
- Applicable to all sites/types of surgery eg. cataracts, toe, nailbed, etc
- ‘Never fails to work’
5
Q
What are disadvantages of general anaesthesia?
A
- Polypharmacy
- Derangement of CVS and resp system → be aware of these problems and be ready to tackle
- Recovery
- Post-op N+V (PONV) → can delay discharge, and cause unsatisfaction, wound dihessence, electrolyte imbalance
- Awareness → shouldn’t happen!
6
Q
What is the mechanism of general anaesthesia?
A
- Not clear (!)
- Involves ascending reticular activating system, cerebral and olfactory cortex, hippocampus and limbic system
- Modification of pre-synaptic release of NTs +/- postsynaptic binding
- Reduced excitatory (glutamate) and increased inhibitory NTs (GABA)
- Effect site: at cell membrane (lipid solubility) as well as microtubules and other cytoplasmic structures
7
Q
What is the triad of general anaesthesia (Rees and Gray 1950)?
A
- Hypnosis (midazolam)
- Analgesia (WHO ladder, opiates, fentanyl, morphine)
- Muscle relaxation (suxamethonium, atracurium)
8
Q
What are types of regional anaesthesia?
A
-
Central neuro-axial block
- spinal, epidrual or combined spinal epidural
- Peripheral nerve blocks → block ulnar/axillary nerve
- Plexus block → femoral nerve / supraclavicular blocks
- Local infiltration → ring blocks (finger)
9
Q
What are the relative drug strengths of opioids compared to each other?
A
10
Q
What constitutes the process of anaesthesia?
A
- Preoperative assessment
-
Anaesthetic technique
- induction
- maintenance
- emergence
- Postoperative care
11
Q
What is the ASA classification?
A
- Class I → healthy pt
- Class II → mild systemic disease
- Class III → severe systemic disease, not incapacitating
- Class IV → severe systemic disease, threat to life
- Class V → moribund patient not expected to survive +/- operation
12
Q
What is the WHO safety checklist?
A
- Sign in
- Time out
- Sign out
13
Q
What are the cannula sizes and colours?
A
14
Q
What is important in pre-assessment?
A
- Surgical/Anaesthetic Hx
- Co-morbidities
- Exercising tolerance
- Smoking/ETOH
- Medications → allergies, reg meds
- Fasting time
- Ix → bloods, radiological
- Examination → general, airway
15
Q
What are general medical enquiries that should be made in pre-op assessment?
A
- CVS → IHD, angina, arrhythmias, HTN, functional ability
- Resp → asthma, COPD, recent cough/cold, smoker
- GI → reflux
- Renal → impaired fxn
- Liver → impaired fxn
- Metabolic → diabetes, recent steroids
- Paeds → immunisations, birth history
If the answer is yes to any of the above then find out more!
16
Q
What’s important about medications in pre-assessment?
A
- Tells you a lot about the patient
- Meds to continue (cardio, resp, anti-convulsants)
- Medications to stop
- Drug interactions
17
Q
What drugs need to be stopped before surgery?
A
CHOW
- Clopidogrel → stopped 7d prior, bleeding risk, aspirin + other antiplatelets can often be continued
- Hypoglycaemics
- Oral contraceptive pill (OCP) or HRT → stopped 4wks prior due to DVT risk, advise pts to use alternative contraception
- Warfarin → stopped 5d prior to surgery due to bleeding risk + commenced on therapeutic dose of LMWH ; INR needs to be <1.5 for surgery
18
Q
Before surgery, which drugs need to be altered?
A
- Subcut insulin → switched to IV variable rate insulin infusion
-
Long-term steroids → must be continued, due to risk of Addisonian crisis if stopped, if pt cannot take orally, switch to IV
- simple conversion rate is 5mg PO prednisolone = 20mg IV hydrocortisone
19
Q
What drugs should be started before surgery?
A
- LMWH
- TED stockings
- Antibiotic prophylaxis (ortho, vasc, GI surg)
20
Q
What specific anaesthetic Qs need to be asked?
A
- Previous GA/LAs
- Airway issues
- FHx → malignant hyperthermia, suxamethonium apnoea
- Fasting duration
21
Q
What are the durations for preoperative fasting periods?
A
- Food & Dairy (incl tea/coffee) - 6hrs
- Clear fluids - 2hrs
- Breast milk - 4hrs
Pulmonary aspiration of gastric contents, even 30-40mL, is associated with significant morbidity and mortality. Fasting aims to reduce volume of gastric contents, and hence risk of aspiration.
22
Q
Which pre-operative investigations need to be completed?
A
- Bloods → FBC, U+Es, LFTs, clotting, G+S/X match
- Radio → ECG, CXR
- Other → pregnancy, sickle cell, urine, MRSA swabs
23
Q
What is the difference between G&S vs cross-match?
A
- G&S → determines pt’s blood group (ABO and RhD) and screens the blood for atypical antibodies; process takes 40 mins + no blood is issued, recommended if blood loss not anticipated, but blood may be required should there be greater loss than expected
- Cross-match → involves physically mixing pt’s blood with donor’s blood, in order to see if any immune rxn takes place; if it doesn’t, the donor blood issued and can be transfused in to the patient, otherwise alternative blood is trialled; also takes 40 mins (in addition to 40mins required to G&S blood, which must be done first) and should be done if blood loss is anticipated
24
Q
How do you do an airway assessment?
A
-
General:
- level of consciousness + co-operation
- BMI
- prev grade of intubation
-
Mouth
- mallampati score
- mouth opening - inter-incisor distance (>3cm good)
- jaw protrusion
-
Face
- beard
- craniofacial deformity
-
Teeth
- edentulous
- teeth prominence and condition
- dentures/caps/crowns/loose teeth
-
Neck
- neck length
- range of motion
- thryo-mental distance (>6cm good)
- soft tissue
25
Airway assessment: What is "**LEMON**"?
* **L - look**
* **E - evaluate** 3-3-2 rule
* inter - incisor distance 3 fingers
* hyoid - mental distance 3 fingers
* thyroid - mouth distance 2 fingers
* **M - mallampti**
* **O - obstruction**
* epiglottis/trauma
* **N - neck mobility**
26
What is the **perioperative** care of patients with **T1DM**?
* Should be first on morning list and may need admitting night before
* On night before, **reduce** subcut basal insulin dose by 1/3rd
* Omit **morning** **insulin** + commence **IV variable rate insulin infusion** pump (sliding scale) - syringe driver 49.5mL NaCl 0.9% + 50U Actrapid
* Whilst NBM, prescribe 5% dextrose - given 125mL/hr, ask nurse to check BM every 2hrs
* Continue until pt is able to eat + drink
* Once able to eat/drink → **overlap** IV variable rate insulin infusion stopping and their normal SC insulin regimens starting. To do this, give their SC rapid acting insulin 20mins before a meal and stop their IV infusion 30-60 mins after they've eaten
27
What is the **perioperative** care of patients with **T2DM**?
* Management depends if controlled
* If **diet** controlled, **no action** required peri-operatively
* Ih pts controlled by oral hypoglycaemics, **metformin** to be stopped on **morning** of surgery, whilst **others** should be stopped **24hrs before** operation
* These pts will be put on IV variable rate insulin infusion along with 5% dextrose as described for T1DM
28
What are the **induction** **agents**?
* Propofol
* Thiopentone
* Ketamine
* Etomidate
29
Which **opiates** are used?
* Morphine
* Fentanyl
* Alfentanil
* Remifentanil
30
Which **muscle relaxants** are used?
* Suxamethonium (polarising agent)
* Rocuronium (non-depolarising)
* Atracurium (non-depolarising)
31
Which **anti-emetics** are used?
* Ondansetron
* Cyclizine
* Dexamethasone
32
Which **hypnotic** is used?
Midazolam
33
Emergency drug: What does **Ephidrene** do?
* **Beta 1 agonist**
* Increases BP
* Increases HR
34
Emergency drugs: What does **Atropine** / Glycopyyrolate (green) do?
Increases HR
35
**Regional anaesthesia** is ideal for many operations, in particular those on the **limbs** and **lower abdomen**. For those who do not wish to be fully awake for surgery, **sedation** can also be used. For many other operations, regional analgesia can complement GA and provide lasting and effective post-operative pain relief.
What are '**Desert island blocks**'?
No single anaesthetist can be proficient in all blocks. ‘Desert island blocks’ are those that ideally all anaesthetists should know how to perform, do not require high-tech equipment, and cover as much of the body as possible, including:
* **interscalene** brachial plexus block → shoulder + elbow
* **axillary** brachial plexus block → every other part of arm
* **labat sciatic** nerve block → almost all leg
* **femoral** nerve block → rest of leg
* **spinal** anaesthesia → for abdomen
36
Which (regional) blocks are used for which part of the body?
37
What are commonly used **local anaesthetics**?
38
What are commonly used **adjuncts** to regional anaesthesia?
39
Local anaesthetics: What are **features** of **lidocaine**?
* An **amide**
* Local anaesthetic + less commonly used antiarrhythmic
* **Hepatic** **metabolism**, protein bound, **renally** excreted
* Toxicity → due to **IV** or **XS** administration, inc risk of **liver** **dysfunction** or low protein states, can be treated w/ **IV 20% lipid emulsion**
* **Drug interactions** → beta-blockers, ciprofloxacin, phenytoin
* _Features of toxicity_ → initial **CNS over-activity**, then **depression** as lidocaine initially blocks inhibitory pathways then blocks both inhibitory and activating pathways, also cardiac arrhythmias
* Increased doses may be used when combined w/ adrenaline to limit systemic absorption
40
Local anaesthetics: What are **features** of **cocaine**?
* Clinical use concentrations 4 and 10%
* Applied **topically** to nasal mucosa
* **Rapid** onset + additional advantage of marked vasoconstriction
* **Lipophillic** + readily crosses BBB
* Systemic effects → cardiac **arrhythmias**, **tachycardia**
* Some use in ENT surgery, but otherwise _rare_ in mainstream surgery
41
Local anaesthetics: What are **features** of **Bupivacaine**?
* Binds to intracellular portion of sodium channels + blocks sodium influx into nerve cells, prevents depolarisation
* Much **longer duration** of action than lignocaine
* Used for **topical wound infiltration** at the conclusion of surgical procedures with long duration analgesic effect
* It's **cardiotoxic** + contraindicated in regional blockage in case tourniquet fails
* Levobupivicaine is less cardiotoxic and causes less vasodilatation
42
All local anaesthetic agents dissociate in tissues + this contributes to their therapeutic effect. The dissociation constant shifts in tissues that are acidic eg. where an abscess is present and this reduces the efficacy.
What are **doses** of **local anaesthetics**?
43
**Summary of basic anaesthetic drugs**
44
What are some commonly used **intravenous** **anesthetics**?
* **Propofol** standard drug for induction of anaesthesia
* **Etomidate** used in cases of haemodynamic instability
* **Ketamine** for emergency medicine - strong dissociative, sympathomimetic and analgesic effects
* **Barbituates** useful in pts w/ high ICP and/or head trauma
