Anaesthetics Flashcards
1
Q
Discuss what needs to be covered in the Hx in a pre-operative assessment?
A
- Age, gender
- Presenting complant and Hx of presenting complant - indication for surgery.
- Surgical/anaesthetic Hx:
- Previous anaesthetics, any complications, previous intubations, medications, drugs allergies, post-operative N/V
- FHx
- Abnormal anaesthetic reactions, malignant hyperthermia, pseudocholinesterase deficiency
- PMHx
- CNS: seizures, TIA/strokes, raised ICP, spinal disease, aneurysm
- CVS: angina/CAD, MI, CHF, HTN, valvular disease, dysrhythmias, peripheral vascular disease (PVD), conditions requiring endocarditis prophylaxis, exercise tolerance, CCS/NYHA class
- respiratory: smoking, asthma, COPD, recent upper respiratory tract infection, sleep apnea
- GI: GERD, liver disease, NPO status
- renal: insufficiency, dialysis, chronic kidney disease
- hematologic: anemia, coagulopathies, blood dyscrasias
- MSK: conditions associated with difficult intubations – arthritides (e.g. rheumatoid arthritis), cervical tumors, cervical infections/abscesses, trauma to cervical spine, previous cervical
spine surgery, Trisomy 21, scleroderma, conditions affecting neuromuscular junction (e.g. myasthenia gravis) - endocrine: diabetes, thyroid disorders, adrenal disorders
- other: morbid obesity, pregnancy, ethanol/other drug use
2
Q
Discuss what needs to be covered in the physical exam in a pre-operative assessment?
A
- weight, height, BP, pulse, respiratory rate
- focused physical exam of the CNS, CVS, and respiratory systems
- general assessment of nutrition, hydration, and mental status
- airway assessment
- done to determine intubation difficulty (no single test is specific or sensitive)
- cervical spine stability and neck movement – upper cervical spine extension, lower cervical spine flexion (“sniffing position”)
- Mallampati classification
- “3-2-1 rule”
- thyromental distance (distance of lower mandible in midline from the mentum to the thyroid notch); <3 finger breadths (<6 cm) is associated with difficult intubation
- mouth opening (<2 finger breadths is associated with difficult intubation)
- anterior jaw subluxation (<1 finger breadth is associated with difficult intubation)
- tongue size
- dentition, dental appliances/prosthetic caps, existing chipped/loose teeth – must inform patients of rare possibility of damage
- nasal passage patency (if planning nasotracheal intubation)
- assess difficulty of ventilation
- examination of anatomical sites relevant to lines and blocks
- bony landmarks and suitability of anatomy for regional anesthesia (if relevant)
- sites for IV, central venous pressure (CVP), and pulmonary artery (PA) catheters
3
Q
Describe the Mallampati classifcation of oral opening.
A
4
Q
What are the 6 As of general anaesthesia?
A
- Anaesthesia
- Anxiolysis
- Amnesia
- Areflexia (muscle relaxation not always required)
- Autonomic stability
- Analgesia
5
Q
What are the key things to look out for in evaluating a difficult airway?
HINT: LEMON
A
- Look - obesity, beard, dental/facial abnormalities, neck, facial/neck trauma
- Evaluate - 3-2-1 rule
- Mallampati score
- Obstruction - stridor, foreign body
- Neck mobility
6
Q
What are the routine investigations that need to be order pre-operatively?
A
- FBC
- Group and hold
- INR, aPTT
- UEC
- Fasting glucose
- ß-hCG
- ECG
- CXR
7
Q
What are the pre-operative medications to consider and medications to stop?
A
- pay particular attention to cardiac and respiratory medications, opioids and drugs with many side effects and interactions
- pre-operative medications to consider
- prophylaxis
- risk of GE reflux: sodium citrate 30 mL PO or ranitidine 150-300 mg PO or metoclopramide 10 mg PO 30 min to 1 h pre-operatively
- risk of infective endocarditis, GI/GU interventions: antibiotics
- risk of adrenal suppression: steroid coverage
- anxiety: consider benzodiazepines
- COPD, asthma: bronchodilators
- CAD risk factors: nitroglycerin and β-blockers
- prophylaxis
- pre-operative medications to stop
- oral hypoglycemics: stop on morning of surgery
- antidepressants: stop on morning of surgery
- ACE inhibitors and angiotension receptor blockers: stop on morning of surgery
- warfarin (consider bridging with heparin), anti-platelet agents (e.g. clopidogrel)
- discuss perioperative use of ASA, NSAIDs with surgeon
- in patients undergoing noncardiac surgery, starting or continuing low-dose aspirin in the perioperative period does not appear to protect against post-operative MI or death, but increases the risk of major bleeding
- Note: this does not apply to patients with bare metal stents or drug-eluting coronary stents
- pre-operative medication to adjust
- Insulin (consider insulin/dextrose infusion or holding dose), prednisone, bronchodilators
8
Q
Discuss what is the amount of fluid needed for maintanence? including K+ and Na+
A
- average healthy adult requires approximately 2500 mL water/d
- 200 mL/d GI losses
- 800 mL/d insensible losses (respiration, perspiration)
- 1500 mL/d urine (beware of renal failure)
- 4:2:1 rule to calculate maintenance requirements (applies to crystalloids only)
- 4 mL/kg/h first 10 kg
- 2 mL/kg/h second 10 kg
- 1 mL/kg/h for remaining weight >20 kg
- increased requirements with fever, sweating, GI losses (vomiting, diarrhea, NG suction), adrenal insufficiency, hyperventilation, and polyuric renal disease
- decreased requirements with anuria/oliguria, SIADH, highly humidified atmospheres, and CHF
- maintenance electrolytes
- Na+: 3 mEq/kg/d
- K+: 1 mEq/kg/d
- 50 kg patient maintenance requirements
- fluid = 40 + 20 + 30 = 90 mL/h = 2160 mL/d = 2.16 L/d
- Na+ = 150 mEq/d (therefore 150 mEq / 2.16 L/d ≈ 69 mEq/L)
- K+ = 50 mEq/d (therefore 50 mEq / 2.16 L/d ≈ 23 mEq/L)
- above patient’s requirements roughly met with 2/3 D5W, 1/3 NS
- 2/3 + 1/3 at 100 mL/h with 20 mEq KCl per liter
9
Q
Name these structures.
A
10
Q
What features predict difficulty in ventilating a patient?
HINT: BONES
A
- Beard
- Obesity (BMI >26)
- No teeth
- Elderly (age >55)
- Snoring Hx (sleep apnea
11
Q
Name these structures
A
12
Q
Name these structures
A
13
Q
Describe simple modes of ventilatory support.
A
14
Q
Categorise the main drugs used in anaesthesia and provide examples of each group.
A
- Anxiolytics
- Benzodiazepines
- Induction agents
- Propofol
- Thiopental
- Ketamine
- Benzodiazepines
- Analgesics
- Paracetamol
- NSAIDs
- Opioids:
- Codeine
- Morphine
- oxycodone
- Hydromorphone
- Fentanyl
- Neuromuscular blocking agents
- Depolarising muscle relaxants (non-competitive): Succinylcholine
- Non-depolarising muscle relaxants (competitive): Rocuronium
- Antibiotics
- Antiemetics
- Metoclopramide (not with bowel obstruction)
- Ondansetron
- Vasopressors
- Noradrenaline
- Vasopressin
- Local anaesthetics
- Lidocaine
- Chloroprocaine
15
Q
Describe the WHO analgesic ladder.
A
