Sharp versus blunt needle: a comparative study of penetration of internal structures and bleeding in dogs

Complications associated with interventional pain procedures have raised questions regarding the relative safety of sharp vs. blunt needles. It has been speculated that the incidence of hemorrhage, intraneural and/or intravascular injections may be reduced by the use of blunt needles. In this study we compared penetration and bleeding associated with sharp vs. blunt needle punctures.

Attempts were made to insert blunt and sharp needles (18-, 20-, 22-, and 25-gauge) directly or percutaneously into kidney, liver, renal artery, intestine or spinal nerve/nerve root of anesthetized dogs. Penetration and bleeding were ascertained by direct vision through a surgical wound.

All attempts to directly puncture the kidney and liver with sharp needles were successful. All but one attempt to puncture a spinal nerve/nerve root with 20-, 22-, and 25-gauge sharp needles were successful but half or less attempts to puncture the intestines were successful. All attempts to puncture the renal artery with sharp needles were successful. Blunt needles never punctured the renal artery, spinal nerve/nerve root and intestines and rarely penetrated the kidney (22- and 25-gauge one time each). All attempts to puncture the liver with blunt needles were successful. Bleeding scores for kidney punctures were generally higher for larger sharp needles than for smaller ones. Bleeding scores for blunt needle punctures of the liver were generally smaller than for sharp needle puncture.

Blunt needles are less likely than sharp ones to enter vital structures and/or produce hemorrhage. Thus, blunt needles may be preferable to sharp ones for performing interventional pain procedures.