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Paracetamol

In this article we will discuss paracetamol roles in perioperative analgesia.

Paracetamol

There is very little downside to prescribing oral paracetamol preoperatively. It is a cheap and effective opioid-sparing agent which is well tolerated.

Uses:

Analgesic and antipyretic.

Preparations:

  • PO tablet or liquid formulations of varying strengths
  • IV Clear colourless 10mg/ml solution
  • PR suppository

Actions:

  • Analgesia
  • Anit-pyretic
  • Anti-inflammatory

The exact mechanism of action is unclear but it acts on multiple receptors including COX1/2 (cyclooxygenase), 5HT3 (serotonin) and CB1 (cannabinoid) receptors.

Benefits:

  • Analgesic and anaesthetic sparing effect
  • Decreased postoperative nausea and vomiting
  • Improved intestinal motility
  • Enhanced recovery

Proven benefit in bowel surgery in terms of return of normal function and lower postoperative pain scores.

Dose:

15 mg/kg every 6 hours.

The plasma level achieved at recommended levels is relatively low. Although, toxicity is rare patients should be monitored for clinical signs and symptoms.

Onset:

  • PO: 45 minutes to peak plasma level with peak analgesic time 1-2 hours after.
  • IV: 20 minutes to peak plasma level with peak analgesic time 1-2 hours after.

Kinetics:

  • Bioavailablity 63-89% (Oral), 100% (Intravenous)
  • Elimination half-life ~ 2hours
  • Plasma protein binding ~ 70-80%
  • Metabolized by the liver
  • Excreted in the urine

Rectal administration has unpredictable bioavailability and low patient acceptability. This route can be considered if alternatives are not feasible.

Caution:

  • Liver Failure
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Introduction to Using Total Intravenous Anaesthesia (TIVA)

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