1730

Technique of Injection

The technique of injection is critical to safety, and whatever block procedure is used, five basic safety rules must be systematically followed:

1. An aspiration test is done before any injection. In the case of unexpected reflux of biologic fluid, especially blood, the procedure must be stopped and the needle withdrawn.
2. Cardiac monitoring is done after injection of a test dose (0.5 to 1 mL) containing 0.5 to 1 µg/kg of epinephrine (when not contraindicated) for 30 to 60 seconds. Inadvertent intravascular injection is suspected in the case of early (within 15 seconds) elevation of the ST segment and T-wave amplitude changes,^{[123] [124]} consistently followed by an increase in blood pressure^{[124] [125] [126] [127]} and inconsistently by tachycardia that is often preceded by bradycardia. Any of these symptoms requires immediate cessation of the technique. For patients who are not eligible for administration of epinephrine, isoproterenol (0.05 to 0.1 µg/kg) has been successfully used as an alternative for the test dose.^{[128] [129]}
3. The injection rate should not be faster than 10 mL/min, which is 60 to 120 seconds, depending on the volume.^[130]
4. The injection should be stopped immediately if any unusual resistance is felt. This prevents the potential danger of an intraneural injection.
5. Repeated aspiration tests during injection (every 5 mL) and before reinjection are always indicated when injecting through a catheter. This helps verify that the tip of the needle or catheter has not moved and pierced a vessel.