Post Operative Nausea and Vomitting (PONV)

Primary risk factors

Patient-specific

Female Gender

Nonsmoker

History of PONV

History of motion sickness

Anxiety

Anesthetic Related

Use of volatile anesthetics

Use of nitrous oxide

Use of etomidate/ketamine

Intra/postoperative use of opioids

High dose neostigmine (increased peristalsis)

PPV with ventilation >20 mmHg (open lower esophageal sphincter)

Surgery related

Duration of surgery

Types of surgery

• Laparoscopy, laparotomy, ear, eye mandibles, plastic, neurologic, abdominal, GYN and T&A surgeries

Anesthetic Considerations

Premedication

Zantac 150 mg PO

• H₂ blocker - blocks Histamine = decreased acid production in the stomach, reduced hydrogen release from parietal cells
• Other drugs are cimetidine, famotidine

Reglan 10 mg PO

• 0.1 mg/kg for children
• Increases motility/LES tone and may have a central antiemetic effect by blocking dopaminergic receptors in the brain) - peaks 40-120 min post-administration

Reglan 10 mg IM

• 0.1mg/kg for children
• Should be given 45 min before surgery

Reglan 10-20 mg IV

• 0.15-0.2 mg/kg in children over 3-5 min at least 30-45 min before surgery

Alka-Seltzer Gold 2 tabs with 30 mL of water

• 0.4 mL, where the goal is to increase stomach PH to >2.5 before intubation
  • Decreases the severity of aspiration pneumonia

Consider a Scopolamine patch before surgery

• 2-4 hr onset, dry mouth, drowsiness, contact dermatitis, visual disturbances
• Good hand washing after application and removal

Elevate the head during intubation

Consider cricoid pressure and perform RSI

Insert NG tube post-intubation to manage GI secretions   

Chemoreceptor locations

Cerebellum: H1, M1

Chemoreceptor trigger zone: 5HT3, D2, M1, NK1

Solitary tract nucleus: 5HT3, D2, M1, H1

Stomach/small intestine: 5HT3  

5HT3: Ondansetron, Granisetron, Dolasetron, Palonosetron, Alosetron

D2: Prochlorperazine (Compazine), Promethazine (Phenergan), Droperidol, Metoclopramide

NK1: Aprepitant

M1: Scopolamine

H1: Diphenhydramine, Promethazine, Meclizine (Antivert)  

Vomiting Center

Receptors and Associated Drugs

Serotonin/ 5HT receptor

• Approximately 80 percent of the human body's total serotonin is located in the Enterochromaffin cells in the gut where it is used to regulate intestinal movements
• Serotonin activates vagal afferents via the 5-HT3 receptor, which signals to the brain, generating nausea
• Zofran is an antagonist of the 5-HT3 receptor

Dopamine D2 receptor

• Part of the Chemoreceptor trigger zone (CTZ) in the medulla, which communicates with the vomiting center
• Antagonists are Reglan, Phenergan, Compazine, Vistaril, Droperidol

Histamine H1 receptor

• Benadryl

Muscarinic M1 (acetylcholine)

• Scopolamine

THC (tetrahydrocannabinol)

• Dronabinol (from cannabis may alleviate nausea)

Spinal Accessory – Aprepitant

• Emend is an antiemetic chemical compound known as a Substance P antagonist
• Mediates its effect by blocking Neurokinin 1 receptor, preventing nausea and vomiting

Gastric Proton-Pump Inhibitors (PPIs)

Omeprazole (Prilosec)

• Inhibition of gastric acid secretion, longer action than H2-receptor antagonists
• Can give 40 mg IV post-induction, as effective as ranitidine in raising gastric pH >2.5

Lanzoprazole (Prevacid) and Rabeprazole (Aciphex)

• 20 mg and 30 mg, respectively, not as effective as Ranitidine 150 mg po

Pantoprazole (Protonix)

• 40 mg IV comparable with ranitidine 50 mg IV in increasing pH and reducing gastric fluid volume

Histamine H2 receptor

Cimetidine

• 300 mg IV helps reduce the risk of pulmonary aspiration

Famotidine

• 20 mg IV given 15-30 min before surgery increases gastric pH

Ranitidine

• 50-100 mg IV decreases the risk associated with pulmonary aspiration