Anaesthetics Flashcards
What are some of the pre-operative checks needed before surgery?
- Consent
- Operative fitness: cardiorespiratory comorbidities
- Regular medications
- History of MI, asthma, HTN, jaundice and complications of anaesthesia: DVT, anaphylaxis
- Ease of intubation: neck arthritis, dentures, loose teeth
- DVT prophylaxis
- Site: correct and marked
What are the nil by mouth protocols?
By the time of surgery it should have been:
1. More than 2 hours for fluids
2. More than 6 hours for solids
What are the different ASA scores?
ASA 1: normal, healthy patient
ASA 2: patient with mild systemic disease
ASA 3: patient with severe systemic disease
ASA 4: patient with severe systemic disease that is a constant threat to life
ASA 5: Moribund (at point of death) patient that is not expected to survive without the operation
ASA 6: declared brain-dead patient whose organs are being removed for donor purposes
What is an example of ASA 1?
Healthy, non-smoker, no or minimal alcohol use
What are examples of ASA 2?
- Current smoker
- Social alcohol drinker
- Pregnancy
- Obesity (BMI 30 - 40)
- Well-controlled Diabetes Mellitus/Hypertension
- Mild lung disease
What are examples of ASA 3?
One or more moderate to severe diseases:
1. Poorly controlled Diabetes Mellitus/Hypertension
2. COPD
3. Morbid obesity (BMI > 40)
4. Active hepatitis
5. Alcohol dependence or abuse
6. Implanted pacemaker
7. Moderate reduction of ejection fraction
8. End-Stage Renal Disease undergoing regularly scheduled dialysis
9. History (>3 months) of Myocardial infarction or cerebrovascular accidents
What are examples of ASA 4?
- Recent (< 3 months) of Myocardial infarction cerebrovascular accidents
- Ongoing cardiac ischaemia or severe valve dysfunction
- Severe reduction of ejection fraction
- Sepsis, DIC, ARDS or end-stage renal disease not undergoing regularly scheduled dialysis
What are examples of ASA 5?
- Ruptured abdominal/thoracic aneurysm
- Massive trauma
- Intra-cranial bleed with mass effect
- Ischaemic bowel in the face of significant cardiac pathology or multiple organ/system dysfunction
What are the principles of anaesthesia?
- Aims: hypnosis, analgesia, muscle relaxation
- Induction: e.g. IV propofol
- Muscle Relaxation
a. Depolarising: suxamethonium
b. Non-depolarising: vecuronium, atracurium - Airway Control: ET tube, LMA
- Maintenance
a. Usually volatile agent added to N2O/O2 mix e.g. halothane, enflurane - End of anaesthesia:
a. Change inspired gas to 100% O2
b. Reverse paralysis: neostigmine and atropine (prevent muscarinic side effects)
What are some of the complications of anaesthesia?
- Propofol induction: cardiorespiratory depression
- Intubation: oropharyngeal injury, oesophageal intubation
- Loss of pain sensation: urinary retention, pressure necrosis, nerve palsies
- Loss of muscle power: no cough could lead to atelectasis and pneumonia
- Malignant hyperpyrexia
- Anaphylaxis: from antibiotics, colloid (rare)
What is malignant hyperpyrexia?
Also known as malignant hyperthemia:
1. Seen following administration of anaesthetic agents, causes excessive calcium release
2. Characterised by hyperpyrexia and muscle rigidity
3. Autosomal dominant pattern
4. Casuative agents: halothane, suxamethonium
5. Investigations: CK, contracture tests
6. Management: Dantrolene, prevents calcium release from the sarcoplasmic reticulum
Why is analgesia necessary in anaesthetics?
Pain leads to:
1. Autonomic activation → arteriolar constriction → reduces wound perfusion → impaired wound healing
2. Reduced mobilisation → increased risk of VTE and reduced function
3. Reduced respiratory excursion and reduced cough → increases risk of atelectasis and pneumonia
What is the general guidance of analgesia in anaesthetics?
Give regular doses at fixed intervals
Consider best route: oral when possible
PCA (patient controlled analgesia) should be considered: morphine, fentanyl
Follow stepwise approach
Liaise with Acute Pain Service
What is the best pre-operative analgesia?
Epidural anaesthesia: e.g. bupivacaine
What is the stepwise approach to post-operative analgesia?
- Non-opioid ± adjuvants:
a. Paracetamol
b. NSAIDs: Ibuprofen: 400mg/6h PO max, Diclofenac: 50mg PO / 75mg IM - Weak opioid + non-opioid ± adjuvants
a. Codeine
b. Dihydrocodeine/ Tramadol - Strong opioid + non-opioid ± adjuvants
a. Morphine: 5-10mg/2h max
b. Oxycodone
c. Fentanyl
