4: Peri-Operative Medicine

Question 1

what are causes of hypothermia in surgery

Answer 1

• higher ASA
• major surgery
• low body weight
• large amount of cold IV infusions/blood transfusion
• exposure to cold theatre environment
• muscle relaxanats prevent shivering
• spinal/epidural anaesthesia

Question 2

how does spinal/epidural anaesthesia cause hypothermia

Answer 2

prevents peripheral vasoconstriction via reduced sympathetic tone
- increased heat loss at the peripheries

Question 3

ASA I

Answer 3

healthy
non smoker
non drinker
BMI <30kg/m

Question 4

ASA II

Answer 4

• mild systemic disease e.g. smoke, social alcohol consumption
• pregnant
• obese BMI 30-40
• well-controlled DM, HTN, mild lung disease

Question 5

ASA III

Answer 5

• poorly controlled DM, HTN, COPD
• morbidly obese >40
• alcohol dependence or abuse

Question 6

ASA IV

Answer 6

• severe systemic disease e.g. ongoing cardiac ischaemia
• recent MI
• sepsis
• end-stage renal disease

Question 7

ASA V

Answer 7

patient who are unlikely to survive without surgical intervention
- e.g. major trauma or significant bleeding

Question 8

ASA VI

Answer 8

declared brain-dead patient whose organs are being removed for donation

Question 9

what are pre-op guidannces for starvation of
- solids
- clear liquids

Answer 9

• solids: 6 hours
• clear liquids: 2 hours

Question 10

what are the advantages of spinal anaesthetics

Answer 10

• conscious during procedure e.g. during birth
• can use in COPD patients as no interference with airways or ventilation

Question 11

compare and contrast spinal vs epidural

Answer 11

spinal
- delivers drug to subarachnoid space into CSF and acts on spinal cord directly
- profound block of all motor and sensory function below level of injection
- shorter procedures
- onset of analgesia ~5 mins
- can be given at cervical, thoracic or lumbar site

epidural:
- delivers drugs outside the dura and has main effects on nerve roots leaving dura
- blocks a band of nerve roots with normal function around site of injection
- can be given as catheter
- onset of analgesia ~25-30 mins
- below L2

Question 12

what is the function of glycopyrronium

Answer 12

decreases secretions in the airways

Question 13

what is thiopental and what is its side effect

Answer 13

induction agent
laryngospasm

Question 14

what is malignant hyperthermia/hyperpyrexia

Answer 14

• hereditary condition that causes an adverse reaction to anaesthetic
• mainly precipitated by halothane or suxamethonium (volatiles)

Question 15

what are the symptoms/complications of malignant hyperthermia

Answer 15

• severe muscle rigidity/spasms
• tachycardia
• low O2, high CO2
• arrhythmias
• metabolic acidosis

Question 16

how is malignant hyperpyrexia corrected

Answer 16

dantrolene!
- skeletal muscle relaxant
- active cooling
- ITU care

Question 17

in what setting is administration of local anaesthetic not suitable

Answer 17

acidic e.g. abscesses as they are basic solutions

Question 18

what are the symptoms of local anaesthetic toxicity and how is it treated

Answer 18

• peri-oral tingling
• paraesthesia
• progress to drowsiness, seziures, coma
  ✅ lipid emulsion

Question 19

describe the features of crystalloid IV fluids

Answer 19

• contains electrolytes
• metabolic substrates
• small molecules able to diffuse through cap wall
• suitable if cells are dehydrated
• e.g. Hartmann’s (most similar to plasma without glucose) or NaCl

Question 20

describe the features of colloid IV fluids

Answer 20

• large molecules that don’t readily pass through cap walls
• remain in intravascular space (blood)

Question 21

how long before surgery should oral contraceptives be stopped and why

Answer 21

4 weeks before elective due to risk of VTE

Question 22

what is the gold standard of detecting oesophageal intubation

Answer 22

capnography
- if tube is in the oesophagus then there will be no end-tidal carbon dioxide as there is no ventilation

Question 23

what is pseudocholinesterase deficiency

Answer 23

• increase duration of action of muscle relaxants e.g. suxamethonium
• resp arrest inevitable unless pt mechanically ventilated

Question 24

what are contraindication of neuraxial blocks

Answer 24

1. infection at site of injection
2. uncorrected hypovolaemia as it cases vasodilation
3. increased intracranial pressure

Question 25

what are risk of neuraxial blocks

Answer 25

• postudural puncture headache due to hypotension
• epidural haematoma
• cauda equina syndrome
• total spinal anaesthesia