7 Perioperative Medicine Flashcards
A patient presents for a total thyroidectomy.
a) Name any five specific investigations that are indicated in the
preoperative assessment and explain why they are indicated.
1 ● Full blood count —
to rule out the adverse effects of antithyroid medications such as thrombocytopenia;
to measure baseline haemoglobin as total thyroidectomies can have significant blood loss.
2 ● Thyroid function tests —
the patient should be euthyroid prior to
elective surgery to avoid the risk of a
perioperative thyroid storm or
myxoedema coma.
3 ● Electrolytes and corrected calcium levels
— to obtain baseline levels
and rule out any calcium abnormalities.
4 ● Chest X-ray:
- to assess the size of the goitre;
- to identify tracheal deviation/compression;
- lateral thoracic inlet views to rule out retrosternal extension.
5 ● CT scan of the airway —
to delineate the extent of tracheal
narrowing/invasion.
● Nasendoscopy —
to record any pre-existing vocal cord dysfunction
and/or laryngeal displacement.
b) What factors in a euthyroid patient must the anaesthetist consider during the induction and maintenance phases of a total thyroidectomy?
.
Considerations during anaesthetic induction:
● Adequate preoxygenation and
check the ability to ventilate prior to
muscle relaxation.
● Consider spraying the vocal cords
with lidocaine prior to intubation to
reduce coughing on emergence.
● Avoid overinflating the tube cuff to minimise vocal
cord/tracheal damage.
● If there are any concerns regarding the airway in the preoperative assessment, consider the following options:
- inhalational induction with sevoflurane;
- awake fibreoptic intubation;
- tracheostomy under local anaesthetic performed by a surgeon;
- ventilation through a rigid bronchoscope
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Considerations during the maintenance phase:
● Intravenous/inhalational maintenance with the use of a remifentanil infusion reduces the need for muscle relaxation and allows intraoperative electrophysiological monitoring of the recurrent laryngeal nerve,
if required in complicated cases.
It also provides a bloodless surgical field.
● Positioning with the head extended and sandbag under the shoulders for optimal surgical access.
● Eyes should be adequately padded especially in patients with
exophthalmos.
● Avoid neck ties and maintain a head-up tilt to aid venous drainage.
Maintain good access to an intravenous drip in the hands via long
extensions.
Analgesia with local infiltration by the surgeon and simple analgesia
plus weak opioids.
● Multimodal antiemetics.
c) During extubation, what factors must be considered post-total
thyroidectomy?
RLN palsy - fibreoptic check for palys
tracheomalacia - may become evident afte extubation
deflate cuff and ensure leak - may be airway oedema
ensure airway suctioned / free blood secretions
want to avoid hypertensive response to laryngoscopy
consider deep or remi extubation
● Assess haemostasis before wound closure by performing a Valsalva
manoeuvre in a head-down position.
● If there are any concerns regarding the integrity of the recurrent laryngeal nerve, visualise the vocal cords with a laryngoscope or fibreoptic scope.
Fully reverse neuromuscular blockade.
● Deflate the endotracheal tube cuff and ensure there is a leak around the tube prior to extubation, especially in large/longstanding goitres.
● Extubate the patient when awake and sitting upright.
d) List any four important postoperative complications following this surgery and how you would manage them
● Laryngeal oedema —
may occur as a result of traumatic intubation or
with complex surgery. This is managed with corticosteroid therapy and humidified oxygen.
● Tracheomalacia —
may occur in patients with large goitres/tumours;
it requires immediate reintubation.
● Recurrent laryngeal nerve palsy — may occur due to ischaemia, traction, entrapment or transection of the nerve during surgery and may be unilateral or bilateral.
● Hypocalcaemia — temporary hypocalcaemia occurs in up to 20% of patients but permanent hypocalcaemia is rare. Calcium replacement (oral/intravenous) should be instituted immediately.
Thyroid storm — less commonly seen as all patients are rendered euthyroid prior to elective surgery. Management is supportive with active cooling, hydration, beta-blockers and antithyroid drugs.
Dantrolene has also been used successfully.
Q2 — Diabetes and anaesthesia
You are assessing a 63-year-old female for an elective laparotomy in the pre-anaesthetic assessment clinic. She has type I diabetes which is under control.
a) In a patient with diabetes mellitus, what clinical features may
indicate autonomic involvement?
● Cardiac autonomic neuropathy:
- resting tachycardia and reduced heart rate variation;
- orthostatic hypotension;
- delayed recognition of ischaemic chest pain.
● Gastrointestinal autonomic neuropathy:
- oesophageal dysfunction leading to heartburn and dysphagia;
- delayed gastric emptying leading to early satiety, anorexia, nausea and vomiting;
- small bowel dysfunction leading to alternating diarrhoea and
constipation;
- anal and rectal neuropathy;
- gallbladder atony and enlargement.
● Genitourinary autonomic neuropathy:
- neurogenic bladder;
- sexual dysfunction.
● Hypoglycaemia unawareness.
● Anaemia due to reduced sympathetic stimulation of erythropoietin
production.
b) What are the other microvascular and macrovascular
complications of diabetes mellitus?
Microvascular complications (due to tissue exposure to chronic
hyperglycaemia):
● Nephropathy —
commonest cause of renal failure in the developed world.
● Retinopathy —
increased risk of retinal detachment, vitreous
haemorrhage and macular oedema.
● Neuropathy —
most common is a mixed sensory and motor
polyneuropathy.
● Autonomic neuropathy.
● Focal neuropathies —
carpal tunnel syndrome, third cranial nerve
palsies, diabetic amyotrophy.
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Macrovascular complications:
● Hypertension.
● Coronary artery disease.
● Cerebrovascular disease.
● Peripheral arterial disease.
c) List any five classes of oral hypoglycaemic agents that are
available with an example.
Describe the mechanism of action for each
● Sulphonylureas —
gliclazide.
stimulate insulin release from the pancreas and decrease insulin resistance in peripheral tissues (muscle and fat).
● Biguanides —
metformin.
Decrease hepatic glucose output and increase insulin
sensitivity at hepatic and peripheral tissues.
● Thiazolidinediones —
improve peripheral uptake and utilisation of glucose in muscle and fat and also decrease liver glucose production.
● DPP-4 inhibitors —
stimulate insulin secretion, inhibit glucagon
secretion and preserve beta-cell mass in the pancreas.
● Incretin agonists —
bind to glucagon-like peptide-1 (GLP-1) receptors, stimulate glucose-dependent insulin secretion, suppress glucagon secretion, slow gastric emptying and reduce food intake.
● Meglitinides — stimulate the release of insulin from the pancreatic beta cells.
● Alpha-glucosidase inhibitors — inhibit alpha-glucosidase, which converts complex carbohydrates into monosaccharides, thus, slowing and limiting the absorption of glucose.
Q3 — Enhanced recovery programme
A 74-year-old patient is scheduled for a primary total hip replacement.
a) What are the advantages of an enhanced recovery programme (ERP) for this type of surgery?
b) What preoperative measures can be included in the ERP for this patient?
c) List the intraoperative measures that can be included as part of the ERP in this case.
c) List any five classes of oral hypoglycaemic agents that are
available with an example.
Describe the mechanism of action for each
● Sulphonylureas —
gliclazide.
stimulate insulin release from the pancreas and decrease insulin resistance in peripheral tissues (muscle and fat).
● Biguanides —
metformin.
Decrease hepatic glucose output and increase insulin
sensitivity at hepatic and peripheral tissues.
● Thiazolidinediones —
improve peripheral uptake and utilisation of glucose in muscle and fat and also decrease liver glucose production.
● DPP-4 inhibitors —
stimulate insulin secretion, inhibit glucagon
secretion and preserve beta-cell mass in the pancreas.
● Incretin agonists —
bind to glucagon-like peptide-1 (GLP-1) receptors, stimulate glucose-dependent insulin secretion, suppress glucagon secretion, slow gastric emptying and reduce food intake.
● Meglitinides — stimulate the release of insulin from the pancreatic
beta cells.
● Alpha-glucosidase inhibitors — inhibit alpha-glucosidase, which converts complex carbohydrates into monosaccharides, thus, slowing and limiting the absorption of glucose.
Q3 — Enhanced recovery programme
A 74-year-old patient is scheduled for a primary total hip replacement.
a) What are the advantages of an enhanced recovery programme (ERP) for this type of surgery?
● Early mobilisation (operative day if possible).
● Reduced postoperative complications, especially cardiopulmonary.
● Earlier discharge.
● Theatre efficiency.
● Standardised care.
● Increased patient satisfaction
b) What preoperative measures can be included in the ERP for this patient?
● Patient education and engagement.
● Optimisation of comorbidities.
● Admission on the morning of surgery.
● Minimising fasting times and maintaining nutrition.
● Premedication to reduce the stress response, opioid requirements and improve analgesia.
A combination of NSAIDs, gabapentin,
paracetamol, clonidine and dexamethasone can be used.
c) List the intraoperative measures that can be
included as part of the ERP in this case.
● Judicious fluid management.
● Intraoperative use of tranexamic acid.
● Prevention of PONV, e.g. avoidance of nitrous oxide, use of TIVA, multimodal antiemetics.
● Regional anaesthesia — central neuraxial blocks without long-acting opioids.
● Local anaesthetic infiltration by surgeons
with or without a nerve block.
● If using a general anaesthetic technique,
the use of short-acting agents to quicken recovery times.
● Maintenance of normothermia.
● Surgical technique —
minimise operative time, avoidance of drains.
● Avoidance of urinary catheters.
d) What postoperative measures can be included as part of the
ERP for this patient?
● Multimodal analgesia/oral opioids (avoid PCA).
● Encourage early oral intake (energy drinks).
● Planned early mobilisation and physiotherapy.
