Anaesthetics - Peri-Operative Care Flashcards
How common is post-op nausea/vomiting (PONV)?
25% surgical pts
-delayed discharge & recovery
What is the pathophysiology underlying PONV?
Input to vomiting centre from
- higher cortical centres (memory/fear)
- stomach/SI (direct surgical effects)
- chemoreceptor trigger zone (anaesthetic drugs/opioids)
What are the risk factors for PONV?
Pt = F>M, obesity, non-smoker, prev hx of PONV Procedure = abdo, gynae, ENT Anaesthetic = long duration, GA, inhalation agents Post-op = pain, opioid analgesia, dehydration, hypotension
What are the common treatments for PONV?
Cyclizine (50mg/8h IV/IM/PO)
Prochlorperazine (12.5mg/6h IM)
Ondansetron (4mg/8h IV/PO)
When is Dexamethasone added to manage PONV?
At any stage if nausea not controlled
-often added w/ Cyclizine
What is Cyclizine?
Anti-histamine useful in middle ear surgery/motion sickness
When is Cyclizine contraindicated?
Heart failure
BPH
Hepatic/renal disease
What is Prochlorperazine?
Dopamine antagonist stabilizing the CTZ & having prokinetic effects
-also Metoclopramide/Domperidone
When is Metoclopramide ineffective?
PONV
When is Prochlorperazine contraindicated?
Parkinson’s
What is Ondansetron?
5-HT3 antagonist that blocks vagal afferents from gut/CTZ
- most effective agent
- can be given prophylactically
When is use of Ondansetron cautioned?
Hepatic impairment
QT prolongation
Pregnancy/breast feeding
What is Dexamethasone?
Glucocorticoid w/ unknown MoA augmenting other medications
-used early on
How long should supplementary O2 be given for post-op?
At least 72hrs
Why should supplementary O2 be given post-op?
Dose-dependant depression on sensitivity of central chemoreceptors to stimulatory effect on CO2
What are the methods of O2 delivery used post-op?
Nasal cannulae
Simple (Hudson) facemask
Venturi masks
How much O2 do nasal cannulae deliver?
2-4 L/min + plus room air
How much O2 do simple (Hudson) facemasks deliver?
5-10 L/min
How much O2 do venture masks deliver?
Blue = 24% inspired O2, 2-4 L/min White = 28% inspired O2, 4-6 L/min Yellow = 35% inspired, 8-10 L/min Red = 40% inspired, 10-12 L/min Green = 60% inspired, 12-15 L/min
What are the limitations of pulse oximetry?
Cannot distinguish b/w CO & O
-inaccurate after smoke inhalation, CO poisoning, smokers
Does not reflect O2 carrying capacity
Hypovolaemia makes getting a reading difficult
Venous pulsations can produce a venous reading
Nail polish affects SpO2
How should Warfarin be managed pre- & post-op?
Stop 10 days before surgery
-if INR <1.5 surgery can go ahead
Generally substituted w/ LMWH
-withheld evening before surgery
How should Clopidogrel be managed pre-op?
Stop 7 days before surgery
How should COCP be managed pre- & post-op?
Stop 4wks before major ops
-switching to POP acceptable
Restart at first menses
->2 wks after mobilisation
What are the stages of wound healing?
haemostasis
inflammation
regeneration
remodelling
What is the cause of a hypertrophic scar?
Excessive amounts of collagen within a scar
What is the cause of a keloid scar?
Excessive amounts of collagen within a scar. Typically a keloid scar will pass beyond the boundaries of the original injury. They do not contain nodules and may occur following even trivial injury.
shiny dark scar bigger than the wound injury
What are the early causes of post-op pyrexia (0-5 days)?
Blood transfusion Cellulitis Urinary tract infection physiological systemic inflammatory reaction Pulmonary atelectasis
Day 1-2: ‘Wind’ - Pneumonia, aspiration, pulmonary embolism
Day 3-5: ‘Water’ - Urinary tract infection (especially if the patient was catheterised)
Day 5-7: ‘Wound’ - Infection at the surgical site or abscess formation
What are the late causes of post-operative pyrexia? >5 days
VTE
pneumonia
wound infection
anastomotic leak
Day 5+: ‘Walking’ - Deep vein thrombosis or pulmonary embolism
Any time: Drugs, transfusion reactions, sepsis, line contamination
What is the management of post-operative ileus?
NBM + NG tube insertion
What drug should patients taking prednisolone be prescribed before surgery?
Hydrocortisone
When is thromboprophylaxis given post-surgery?
6 hours post surgery
