Blood reflux during local anesthesia - laboratory evaluation

Abstract

The objective of this study was to verify the efficacy of some factors associated to blood reflux into the anesthetic cartridge when accomplishing the aspiration test, before anesthetic injection, in order to avoid an adverse deposition of anesthetic solution in the patient’s bloodstream. Three variables influence in the occurrence of positive aspiration: anesthesia needle size, syringe type, and anesthetic cartridge type. The method employed had the purpose to determine the presence or absence of blood reflux within the anesthetic cartridge when local anesthetic was injected through a test system comprising a latex hose (serum delivery) with human blood connected to a closed system developed for blood pressure measurement and for simulating endovenous pressure conditions. The results demonstrated an overall total of 235 positive aspirations (73.4%) and 85 negative results for blood reflux (26.6%), suggesting we may find false-negative results even with the needle placed within the blood vessel. By using the Duncan’s test (p < 0.05), it was concluded that the long 27-G needle had a significantly higher rate of positive aspirations (57.9%) as compared with the short 30-G needle (42.1%). The syringe with auto-aspiration system achieved a higher rate (65.1%) of blood reflux into the anesthetic cartridge as compared with the nonaspiration one (34.9%), being more effective in performing aspiration, and consequently preventing complications from intravascular local anesthetic injections.