Order of Adding Agents to Peri-articular Injection Mixture
The provided evidence does not contain specific guidelines or research addressing the sequence of adding agents to periarticular injection mixtures for total knee arthroplasty. The available literature focuses on which agents to include and their efficacy, but does not establish a standardized order of mixing.
What the Evidence Does Support
The composition of periarticular injections typically includes:
- Local anesthetics (ropivacaine or bupivacaine) as the base ingredient 1, 2
- NSAIDs (ketorolac) for anti-inflammatory effects 1, 2
- Epinephrine for vasoconstriction and prolonged duration (though one study suggests it may be omitted without loss of efficacy) 2, 3
- Corticosteroids in some protocols 1
Practical Mixing Approach Based on Pharmacologic Principles
While no guideline specifies mixing order, standard pharmaceutical practice for multi-drug injections suggests:
- Start with the largest volume component (local anesthetic solution - typically 150-300 mL of diluted ropivacaine or bupivacaine) 2, 4
- Add water-soluble drugs next (ketorolac, dexamethasone if used)
- Add epinephrine last (if included) to minimize oxidation and ensure even distribution
Critical Caveats
- No standardized protocol exists - injection techniques and compositions vary greatly among surgeons with little standardization 1, 5
- The 2008 guideline specifically states that intra-articular local anesthetic and/or morphine are NOT recommended due to inconsistent efficacy 6, though more recent research (post-2008) shows promising results with high-volume periarticular infiltration techniques 2, 4
- Timing of administration matters more than mixing order - the evidence supports infiltration at the end of surgery with potential postoperative boluses 2
The absence of evidence-based mixing protocols means this decision should be based on institutional pharmacy guidelines and drug compatibility data rather than clinical outcome studies.