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Lignocaine test dose to detect intravenous injection
A M Michels1, G Lyons, P M Hopkins
1Anaesthetic Department, St James's University Hospital, Leeds, West Yorkshire.
Anaesthesia
|March 1, 1995
Summary
A test dose of 1 mg.kg-1 lignocaine effectively detects accidental intravascular catheter placement in 95% of patients, significantly improving safety over lower doses. This crucial test prevents life-threatening injections during epidural anesthesia.
Area of Science:
- Anesthesiology
- Pharmacology
- Obstetrics
Background:
- Accidental intravascular injection of local anesthetics like bupivacaine or etidocaine during epidural procedures has led to maternal fatalities.
- Effective test doses are critical for identifying misplaced intravenous catheters and preventing inadvertent systemic administration of anesthetic agents.
Purpose of the Study:
- To determine the optimal dose of lignocaine for a test dose to detect intravascular catheter placement.
- To compare the efficacy of lignocaine 0.5 mg.kg-1 versus 1 mg.kg-1 as an intravenous test dose.
Main Methods:
- A randomized study involving 60 healthy gynecological patients undergoing anesthesia.
- Patients received either normal saline, lignocaine 0.5 mg.kg-1, or lignocaine 1 mg.kg-1 intravenously as a test dose.
- Subjective symptoms reported by patients were monitored to assess test dose sensitivity.
Main Results:
- Only 50% of patients reported a positive test dose with lignocaine 0.5 mg.kg-1.
- A significantly higher percentage (95%) of patients experienced a positive test dose with lignocaine 1 mg.kg-1 (p < 0.01).
Conclusions:
- Lignocaine 1 mg.kg-1 demonstrates significantly higher sensitivity in detecting intravascular injections compared to 0.5 mg.kg-1.
- The 1 mg.kg-1 dose of lignocaine is recommended as a more reliable test dose to enhance patient safety during epidural anesthesia.