Does adrenaline in local anesthetics increase or decrease bleeding at the surgical site?

This question was submitted by a general dentist: Does adrenaline in local anesthetics increase or decrease bleeding at the surgical site?

Dr. Mark Donaldson, in collaboration with Dr. Suham Alexander, Oasis Discussions Clinical Editor, provided this initial response. 

Dr. Mark Donaldson is Director of Pharmaceutical Services at the Kalispell Regional Medical Center, Clinical Professor in the Department of Pharmacy at the University of Montana, and Clinical Associate Professor in the School of Dentistry at the Oregon Health and Sciences University

Local Anesthetic Composition

Most local anesthetic cartridges contain the following ingredients:

• Local anesthetic drug
• Vasoconstrictor
• Preservative, if contains vasoconstrictor
• Sodium chloride
• Distilled water

Adrenaline or Epinephrine

Epinephrine is a potent vasoconstrictor used in dentistry.  In local anesthetics, it acts on α and β-adrenergic receptors with a more predominant effect on the latter. It is available at concentrations of 1:50,000, 1:100:000, 1:200,000. 

Vasoconstrictors have several mechanisms of action:

• ↓ Blood flow to the site of administration
• ↓ Absorption of anesthetic into bloodstream
• ↓ Risk of toxicity (lower levels in bloodstream)
• ↑ Duration and profoundness of anesthesia
• ↑ Hemostasis (useful in minimizing or preventing bleeding during surgical procedures)

In direct answer to the question, then, adrenaline (epinephrine) in local anesthetic decreases bleeding at the surgical site. However, one additional point needs to be stressed in regards to frequent re-dosing of local anesthetic agents. While the hemostatic effect of adrenaline is primarily due to its interaction with β-adrenergic receptors, frequent re-dosing of local anesthetic agents can lead to a more predominant α-adrenergic receptor effect. When this happens the opposite may occur, and decreased hemostasis may be seen.

This phenomenon is primarily experienced during long dental procedures where re-dosing of local anesthetic agents is required in order to keep the patient comfortable for a longer period of time. The oral healthcare professional may notice that the patient begins to require more frequently administered local anesthetic as the prolonged procedure progresses. In such cases, practitioners must be aware of the maximum recommended doses of the local anesthetic being used since the natural inclination is to give more drug, more frequently in order to keep the patient comfortable. In fact as more medication is administered the α-adrenergic receptor effect becomes even more pronounced leading to ↑ blood flow to the site of administration and ↑ absorption of anesthetic into bloodstream (so the local anesthetic does not stay in the area as long). This can result in ↑ risk of local anesthetic toxicity (increased levels in bloodstream) and a ↓ in the duration and profoundness of anesthesia. In such cases, ↓ hemostasis may be seen.

Reference

Malamed, SF. Handbook of Local Anesthesia. 2004. Mosby Elsevier. St. Louis, Missouri, USA.