The Premedications
Summary
This is a summary on the premedications required for your patients.
Basics
The premedications, or the premeds, are a group of drugs we give our patients before their operation starts (before induction). We give these drugs to our patients for the following reason:
- To help with the sedation of the patient and to reduce the level of anxiety.
- To reduce the risk of aspiration and gastric acid protection.
- To decrease salivary secretions (Antisialagogue).
- To provide analgesia (this is known as pre-emptive analgesia).
- Prophylactic antibiotics.
Always remember that these medications need to be prescribed by you, as the doctor providing the anaesthesia. You do not need to prescribe every medication listed below. You need to individualize your patients and prescribe accordingly to what is needed. For instance, patients commonly receive prophylactic antibiotics, gastric acid protection, and anti-emetics.
Medications
Sedation
- Benzodiazepines
- Diazepam 5-10mg PO 1-2 hours before the operation.
- Lorazepam 1-4mg PO/IM 2 hours before the operation.
- Midazolam 1-5mg IVI/IMI 30 mins before the operation.
- Antihistamines
- Promethazine 25-75mg PO.
There are others available such as Droperidol, Trimeprazineand, and so on.
Reduce Aspiration Risk and Gastric Acid Protection
- H2 Blockers:
- These agents increase the gastric pH and also decrease the volume of the gastric content.
- Cimetidine 200-400mg PO/IMI/IVI
- Ranitidine 150-300mg PO or 50-100mg IVI
- Nonparticulate Antacids:
- These agents increase the gastric pH but they also decrease the gastric volume. This is because the base reacts to form water in the stomach.
- Prokinetics:
- A Dopamine antagonist increases the lower oesophageal sphincter tone and also increases gastric emptying.
- Metoclopramide 10mg PO/IVI/IMI 1 hour before the operation.
Antisialagogue
- Not commonly used unless required.
- Glycopyrrolate: 0.2-0.4mg IVI
Pre-emptive analgesia
- This should be given to all the patients before the operation.
- Paracetamol 1g PO (15mg/kg) or Diclofenac 75mg PO.
Prophylactic Antibiotics
- Usually given 30-60mins before the first skin incision occurs.
- There are many factors that influence the decision for prophylactic antibiotics and which antibiotic to use as well.
- A common drug prescribed is Cefazolin:
- For Surgical Prophylaxis:
- <60kg: 1g, within 60mins of the first incision.
- 60-120kg and BMI ≤35: 2g, as above.
- ≥ 120 or BMI >35: 3g, as above.
- For prophylaxis in pregnancy:
- <60kg: 1g, within 60mins of the first incision.
- 60-100kg: 2g, as above.
- >100kg: 3g, as above.
- For Surgical Prophylaxis:
Note
For example, you might see that before an operation the patients get prescribed Metoclopramide 10mg IV stat and Ranitidine 150mg IV stat usually around 30-60mins before the operation. A prophylactic antibiotic such as Cefazolin 1-2g IV stat is usually given 30mins before the operation.
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