Medical Considerations for Safe Anesthesia Administration

Selecting the safest and most effective anesthetic agents and dosages depends on thorough and accurate health history and health status analysis.^1–4 Local anesthetic agents produce multiple body system reactions; therefore, thorough review and documentation of medical and dental conditions, along with previous adverse reactions or experiences, are key.

Pre-administration vital signs are important to establish the patient’s baseline levels because anesthetic agents and circumstances surrounding administration can alter blood pressure and pulse.^1–5 Obtaining the patient’s current weight allows the dental hygienist to establish individualized safe dosage known as the patient’s maximum recommended dose.

Thorough patient evaluation also includes follow-up questioning regarding past and current medical conditions, determining the patient’s American Society of Anesthesiologists’ Physical Status classification, and recording current over-the-counter or prescribed medications and dosages and any previous adverse reactions to anesthesia.^1–3

Additionally, working collaboratively with the patient’s primary physician and/or healthcare specialists may be required to ensure safe anesthesia administration. Once these vital patient data are collected, the next step is to evaluate the information for potential contraindications to anesthetic agents. Some medical conditions and medications pose higher risks for the administration of either the local anesthetic itself or the vasoconstrictor. Therefore, the local anesthetic agent and/or the vasoconstrictor may need to be adjusted or avoided accordingly.

Cardiovascular Disease

Cardiovascular disease (CVD) is a broad term that refers to any condition that affects the heart and/or blood vessels.⁸ Because patients with CVD are more susceptible to the stressors of dental care and to vasoconstrictors themselves, experts recommend administering minimal amounts of epinephrine.^2–4,6 The “cardiac dose” of epinephrine is one-fifth the amount of a healthy patient dose which is 0.04 mg or 2.2 cartridges of 1:100,000 ratio, and 4.4 cartridges of 1:200,000 ratio.

Lidocaine 2% 1:50,000 epinephrine ratio does not improve effectiveness or duration of anesthesia and, with the increased risk, is not recommended for patients with CVD.^2–4,6 When hemostasis and duration are required, the 1:100,000 ratio of epinephrine may be preferred. The safety of a 1:100,000 vasoconstrictor ratio was demonstrated in a randomized controlled study. Laragnoit et al⁷ found when safe doses of lidocaine 2% 1:100,000 were administered to patients with CVD, it did not increase pulse or blood pressure compared to patients who received lidocaine 2% plain.

Vasoconstrictors should be completely avoided in patients with blood pressure above 180/110 mm/Hg; those who have had a heart attack, stroke, or coronary artery bypass surgery in the past 6 months; and patients with severe or uncontrolled CVD. In these instances, a consultation with the patient’s medical provider is recommended.^2–4,6

Diabetes

Diabetes mellitus affects patients of all ages and can lead to vascular complications.⁴ Thirty million Americans have diabetes, with type 2 being the most prevalent.⁴ While the amount of anesthetic and vasoconstrictors used in a routine dental procedure does not significantly raise blood sugar levels, diabetes can lead to several other complications, such as renal problems, which can affect the primary excretion pathway of local anesthetic drugs.²

Other conditions associated with type 2 diabetes include obesity, hypertension, dyslipidemia (lipid imbalance), and CVD, any of which, if present, must be considered when choosing the local anesthetic and amount administered.^3,4 When administering vasoconstrictors to patients who present with one or more comorbidity, additional caution is advised.^2-4,6 In patients with well-controlled diabetes (A1C between 6.5 and 7% or lower), there are no significant considerations in choice of local anesthetic. When diabetes in uncontrolled, epinephrine should be used with caution (A1C over 7%).^2–4

Thyroid Disease

Hyperthyroidism occurs when there is excessive thyroid gland activity, resulting in the production of too much thyroid hormone.⁸ The excess of thyroid hormone causes the patient to be sensitive to vasoconstrictors. When hyperthyroidism is treated and controlled, vasoconstrictors should be minimized to the 0.04 mg dose for epinephrine and the 0.2 mg dose of levonordephrine.^2–4,6,9 If the hyperthyroidism is not controlled, then the potential for thyrotoxicosis (thyroid storm) exists if vasoconstrictors are administered; in that case, they should be avoided, especially epinephrine.^2–4,6,9

Allergies

Local anesthetics are grouped into two categories: esters and amides. A notable difference between these local anesthetics is the way the body metabolizes, or breaks down the drug.

Esters are metabolized in the blood by the enzyme cholinesterase.^1,2 Once esters are metabolized, a metabolite, called para-amino benzoic acid (PABA), is left.^1,2 Due to PABA, ester local anesthetics are more likely to cause allergic reactions. If a patient has experienced an allergic reaction to one ester type local anesthetic, all esters should be avoided.¹

Amides are predominantly metabolized in the liver and they rarely cause allergic reactions.^1,2,6 An allergic reaction to one amide type of anesthetic does not always yield a reaction to all amide local anesthetics, yet should be noted in the patient’s chart and considered.

Although local anesthetic allergies are rare, they do exist. In a case of a true local anesthetic allergy, there are alternate avenues to proceed with dental treatment. If the allergy is specifically to ester type anesthetics, alternate options include the use of amide local anesthetics, histamine blockers, general anesthesia, or other methods such as hypnosis or acupuncture.⁶

Many patients may claim to be allergic to epinephrine, which is not physiologically possible.¹⁶ Epinephrine, also known as adrenaline, is naturally made and produced by the body. Epinephrine is a hormone as well as a neurotransmitter.

Adverse effects are commonly mistaken as allergic reactions. Patients have concerns when they have experienced an adverse reaction to a local anesthetic. These experiences lead patients to assume they are allergic to anesthetics; therefore, follow-up questions exploring the reaction is necessary to rule in or out an allergic vs an adverse reaction.

Bisulfites

Local anesthetics contain preservatives to extend their shelf life and prevent oxidation.¹ Bisulfite preservatives found in foods, such as lettuce in salad bars, fruit, and wine, are the same bisulfite preservatives found in local anesthetics.^1,2 Sulfites, such as sodium bisulfite and sodium metabisulfite, are preservatives found in local anesthetics that contain vasoconstrictors.⁶ If a local anesthetic does not contain a vasoconstrictor, no preservative will be present. Therefore, if a patient has disclosed an allergy to sulfites, a local anesthetic with no vasoconstrictor such as 3% mepivacaine HCI, should be used. Patients will disclose allergy to sulfa drugs, yet no connection between sulfa allergies and sulfite allergies exist.^1,2,6

Topical Anesthetics

Topical anesthetics are used prior to local anesthetic injections or to provide mucosal tissue or sulcus anesthesia for patient comfort. Similar to local anesthetics, topical anesthetics are also categorized into amides and ester groups. Currently, there are no injectable/submucosal ester anesthetic agents available because of the risk of allergic reaction that ester anesthetics present; however, benzocaine and tetracaine are the most common ester-type topical anesthetics.^1,2,6

Ester topicals should be avoided if there are underlying allergies as there is a documented 30% rate of allergic reactions with ester topicals.³ Amide topicals can be used as a substitute. Amide topicals do not contain bisulfites, and they are not associated with PABA; therefore, they are a safe alternative. The only amide topical anesthetic available is lidocaine which may contain parabens and could produce an allergic reaction among patients with this allergy.³ Thus, it is vital to ask specific questions related to what patients are allergic to and what their allergic response was to determine if there is an allergy potential to the local anesthetic agent.

Liver Disease

The liver is an essential organ that rids the body of toxic substances and aids in food digestion as well transformation of blood clotting factors and metabolism of bilirubin. Liver dysfunction can be genetic, viral, or the result of substance use disorder.⁴ Some of the common signs and symptoms of liver disease include jaundice, abdominal pain and swelling, swelling of the legs and ankles, itchy skin, dark urine, chronic fatigue, loss of appetite, nausea and vomiting, and bruising easily.¹⁰

The liver is directly responsible for one of two routes of biotransformation of local anesthetics. The metabolic transformation is referred to as the hepatic p450 isoenzyme system.^1,2,6 The liver is indirectly responsible for the second route of metabolism of local anesthetics which takes place in the blood stream through the enzyme cholinesterase, which is produced mainly in the liver. While all local anesthetics should be limited in patients with poor liver function, articaine’s biotransformation is unique in that only 5% to 10% is metabolized through the liver’s enzymes. As such, articaine is the better choice.^1,26

Amide anesthetics’ (lidocaine, mepivacaine, bupivacaine) rate of biotransformation depends on the liver function, therefore, lowest effective doses should be administered to patients with liver disease as minimum doses could be capable of producing an overdose if liver function is significantly compromised.^1,6

Kidney Disease

The main function of the kidneys is to filter the blood. Patients may be at a greater risk for kidney dysfunction or disease if they have a comorbidity or an additional health condition(s), such as diabetes or high blood pressure. Additionally, kidney problems, such as injury, cysts, stones, or chronic infections, may contribute to a decrease in kidney function.¹¹

Patients experiencing kidney failure may be on hemodialysis, which artificially filters the blood.¹¹ Local anesthetic agents are all filtered and excreted by the kidneys. Consequently, if a patient has kidney problems, he or she may not be able to filter and excrete the agents at a normal rate. Therefore, clinicians must administer anesthesia with caution.^1–4,6

Dental hygienists should consult with the medical teams of patients undergoing hemodialysis. Dental treatment should not be sceduled until 24 hours after a patient’s last dialysis appointment.¹²

Pregnancy

Pregnancy can present challenges for dental treatment. As with other health conditions, comorbidities, such as diabetes, gestational diabetes, high blood pressure, or other diseases that may accompany pregnancy, increase patients’ risks.^13,14

Pregnant women should receive routine dental hygiene care, and local anesthesia can be administered in any trimester with the consultation of their medical provider. Clinicians wanting to err on the side of caution may wait to administer lidocaine (considered the safest local anesthetic) in the second trimester. Articaine, bupivacaine, and mepivacaine are also permissible but should be administered in reduced amounts. Precaution should be used with administering prilocaine, as it is linked to methemoglobinemia.^1–4,6,14

Like pregnancy, it is safe to administer local anesthetic agents during lactation. A prudent recommendation is to minimize the use of local anesthetics to the smallest amount necessary.^1–4,6,14

Conclusion

Safe, effective, compassionate care is made possible through the administration of local anesthetic agents. Patient pre-administration assessment and follow-up questioning, along with a strong background knowledge of the medical conditions that impact local anesthesia delivery, enable the dental hygienist to make the safest selection of anesthetic agent type and dosage.

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References

1. Logothetis DD. Local Anesthesia for the Dental Hygienist. 3rd ed. St Louis: Elsevier; 2022.
2. Bassett K, DiMarco A, Noughton D. Local Anesthesia. 2nd ed. Upper Saddle River, New Jersey: Pearson; 2015.
3. Malamed S. Medical Emergencies in the Dental Office. 7th ed. St Louis: Elsevier; 2020.
4. Little JW, Fallace DA, Miller CS, Rhodus NL. Dental Management of the Medically Compromised Patient. 9th ed. St Louis: Elsevier; 2018.
5. Bowen DM, Pieren JA. Darby and Walsh Dental Hygiene: Theory and Practice. 5th ed. St Louis: Elsevier; 2020.
6. Malamed S. Handbook of Local Anesthesia. 7th ed. St Louis: Elsevier; 2020.
7. Laragnoit AB, Neves RS, Neves ILI, Vieira JE. Locoregional anesthesia for dental treatment in cardiac patients: A comparative study of 2% plain lidocaine and 2% lidocaine with epinephrine (1:100,000). Clinics. 2009;64:177–182.
8. Mayo Clinic. Hyperthyroidism. Available at: mayoclinic.org/diseases-conditions/hyperthyroidism/symptoms-causes/syc-20373659. Accessed August 22, 2023.
9. Aoun G. Thyroid dysfunction: risk and management in dentistry. Available at: orcid.org/0000-0001-5073-6882. Accessed August 22, 2023.
10. Haas DA. An update on local anesthetics in dentistry. J Can Dent Assoc. 2002;68:546-551.
11. Mayo Clinic. Liver Disease. Available at: mayoclinic.org/diseases-conditions/liver-problems/symptoms-causes/syc-20374502. Accessed August 22, 2023.
12. National Institute of Diabetes and Digestive and Kidney Diseases. Kidney Disease. Available at niddk.nih.gov/health-information/kidney-disease. Accessed August 22, 2023.
13. Sulejmanagic H, Sulejmanagic N, Prohic S, Secic S, Miselijic S. Dental treatment of patients with kidney diseases: review. Bosn J Basic Med Sci. 2005;5:52-56.
14. John Hopkins Medicine. Medical Conditions and Pregnancy. Available at: hopkinsmedicine.org/health/conditions-and-diseases/staying-healthy-during-pregnancy/medical-conditions-and-pregnancy. Accessed August 22, 2023.
15. Donaldson M, Goodchild JH. Pregnancy, breast-feeding and drugs used in dentistry. J Amer Dent Assoc. 2012;143(8):858-871.

From Dimensions in Dental Hygiene. September 2023; 1(8):28-31.