Post-OP Nausea and Vomiting Flashcards
How many get post-op N+V?
20-30% within the first 24-48h post surgery
Consequences of PONV
Anxiety for future surgical procedures
Increased recovery time
Increase hospital stay
Aspiration pneumonia
Metabolic alkalosis
Surgical complications
Patient risk factors
Female gender
Age
Previous PONV or motion sickness
Use of opioid analgesia
Non-smoker
Surgical risk factors
Intra-abdominal laparoscopic surgery
Intracranial or middle ear surgery
Squint surgery
Gynaecological surgery (ovarian especially)
Prolonged operative times
Poor pain control post-op
Anaesthetic risk factors
Opiate analgesia or spinal analgesia
Inhalational agents like isoflurane or nitrous oxide
Prolonged anaesthetic time
Intraoperative dehydration or bleeding
Overuse of bag and mask ventilation.
Two areas in nervous system playing parts in N+V
Vomiting centre
Chemoreceptor trigger zone
Where is the vomiting centre?
Within the lateral reticular formation of the medulla oblongata.
It controls and coordinates the movements involved in vomiting.
Where is the CTZ?
Located in the area postrema (inferoposterior aspect of the 4th ventricle)
It is located outside the BBB so can respond to stimuli in the circulation.
Explain the connection between vomiting centre and CTZ
Vomiting centre receives input from CTZ, GI, vestibular system and higher cortical structures like sight, smell and pain.
This leads to nausea and if the stimuli are sufficient it acts on the diaphragm, stomach and abdominal musculature to initiate vomiting.
Receptors in CTZ
Dopamine and 5HT3 receptors
Receptors of vestibular apparatus
Acetylcholine and histamine receptors
GI tract receptors
Dopamine receptors
Vomiting receptors
Histamine and 5HT3 receptors
Clinical assessment
Ensure they are safe and stable.
ABCDE if needed.
Aspiration might happen so might need to fit an NG tube.
Dx
Infection
GI causes (post-op ileus, bowel obstruction)
Hypercalcaemia, uraemia, DKA
Medication like antibiotics and opioids
CNS causes like raised ICP
Anxiety
