Lidocaine (Xylocaine) is the most widely used anesthetic. Rapid onset of action with limited duration, approximately 30 minutes; maximum dose: 300 mg (30 mL of 1% lidocaine)

Bupivacaine (Marcaine) has a slow onset of action with prolonged duration of effect, for up to 8 hours; maximum dose: 175 mg (70 mL of 0.25% bupivacaine)

A combination of lidocaine and bupivacaine allows the rapid onset of action with a prolonged duration of effect.

Less soluble

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  Methylprednisolone acetate (Depo-Medrol)

  
  
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  Triamcinolone acetonide (Kenalog)

  
  
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  Triamcinolone hexacetonide (Aristospan)

More soluble

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  Betamethasone sodium phosphate (Celestone)

  
  
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  Dexamethasone sodium phosphate (Decadron)

  
  
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  Prednisolone sodium phosphate (Hydeltrasol)

Dosage

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  Dosage requirements vary and should be individualized on the basis of the condition being treated and the response of the patient ( Table 62.1 ).

  
  
  
  

  TABLE 62.1

  
  

  SUGGESTED DOSES FOR CORTICOSTEROID PREPARATIONS

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Corticosteroid Agent	Large Joint	Medium Joint	Small Joint	Soft Tissue
  Methylprednisolone acetate (Depo-Medrol)	20–80 mg	10–40 mg	4–10 mg	4–30 mg
  Betamethasone sodium phosphate (Celestone)	1.0 mg	0.5–1.0 mg	0.25–0.5 mg	0.5–1.0 mg

   
  
  
  
  
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  In chronic cases, injections may be repeated at intervals ranging from 1 week to ≥5 weeks depending on the degree of relief obtained from the initial injection.

  
  
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  No clear safety guidelines exist regarding the frequency and maximum number of injections. Judicious use of injections is recommended.

Membrane-stabilizing agents cause a reversible conduction block along nerve fibers.

Smaller nerve fibers are more sensitive, allowing inhibition of pain signals while sparing pressure and proprioceptive fibers.

Maximum plasma concentrations of local anesthetic are achieved within 10–25 minutes.

Avoid preparations containing epinephrine for intra-articular or soft tissue injections; epinephrine causes vasoconstriction, which prolongs the anesthetic effect when used in the skin.

Interfere with inflammatory cell-to-cell adhesion and migration through the vascular endothelium.

Inhibit the synthesis of cyclooxygenase-2 (COX-2) and various proinflammatory cytokines.

Stimulate gluconeogenesis and catabolic activity in muscle, skin, lymphoid, adipose, and connective tissue

Solubility determines duration of action and extent of systemic effects.

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  Insoluble: Average duration of action is longer for less soluble agents; primarily display local effects

  
  
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  Soluble: Diffuse more readily from the injected region and may exert greater systemic effects; may be more useful in extra-articular or soft tissue injections

Average duration of action is 1–3 weeks and is longer for less soluble agents.

Anaphylaxis: Occurs from acute mast cell degranulation and is characterized by laryngeal edema, bronchospasm, and hypotension; the cause of local toxicity is allergic reaction to para-aminobenzoic acid (PABA). PABA is a metabolic product of the degradation of the ester class of local anesthetics, such as procaine (Novocain), and to a lesser extent, amide class anesthetics such as lidocaine; it is also a metabolic by-product of methylparaben, a preservative in multidose vials of lidocaine.

Toxicity: Usually the result of inadvertent intravenous injection; primary target organ is central nervous system resulting in altered speech, muscle twitching, and seizures. Cardiovascular toxicity (e.g., ventricular arrhythmias) may also occur. Aspirate before injection to avoid inadvertent intravenous injection. Compared with other local anesthetics, bupivacaine is markedly cardiotoxic.

Chondrotoxicity: Emerging evidence suggests that both lidocaine and bupivacaine may have negative effects on articular cartilage health and chondrocyte viability.

Postinjection flare: Most common side effect; related to steroid crystal synovitis; self-limiting; typically lasts for <12 hours; analgesic therapy and ice packs offer effective relief.

Facial flushing: Subjective sensation of warmth in the face and upper trunk

Poor diabetic control: May increase hepatic glucose production and antagonize insulin effects; close monitoring is suggested following a corticosteroid injection

Subcutaneous fat atrophy and skin depigmentation: May occur after a single injection; avoid repeated subcutaneous or superficial injections. Subcutaneous fat atrophy is particularly problematic in the plantar surface of the foot. Skin depigmentation occurs more commonly in dark-skinned individuals.

Tendon rupture: Dose-dependent decrease in tenocyte proliferation and reduced collagen production by tenocytes. Care should be taken to avoid direct intratendinous injection, which can result in this complication.

Steroid – induced arthropathy and cartilage damage: Destruction of articular cartilage and a decrease in cartilage matrix production has been shown in animal studies. Although not reported in humans, a theoretical risk remains.

Infection: Incidence of joint sepsis varies from 1 in 3,000 to 1 in 50,000 for corticosteroid injections. Informed consent should be obtained before any invasive procedure. Use of good sterile technique minimizes this risk.

Anaphylaxis: May occur even after previous uneventful injections

Hypothalamic – pituitary – adrenal axis suppression: Suppression is mild and transient. Avoid simultaneously injecting multiple large joints. Prolonged suppression has been reported.

Syncope: Patients who feel lightheaded or overly apprehensive should lie down. Protect the airway in the event of loss of consciousness. Reassure the patient.