What dose of epinephrine contained in local anesthesia can be ...

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dose limits for epinephrine, particularly when the drug is administered to patients with underlying cardiovascular disease. Epinephrine was first added to the ...
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in reversing the 3 Hs are known, and HBOT has been recognized as the standard of care in the dental profession for many years. However, recent research and reports have questioned this assumption. Some even go so far as to suggest that HBOT may worsen the outcome.4-6 At major cancer treatment centres in the United States (e.g., MD Anderson and Sloan Kettering), large series of patients who have had dental extractions within the field of former cancericidal radiation dosages without the use of HBOT have not developed ORN. Currently, I am no longer recommending preoperative HBOT for this group of patients before extractions, implants or other minor oral surgery. In addition, all patients about to undergo head and neck radiation therapy should have a dental assessment, as this may go a long way toward preventing problems in the first place. If teeth require extraction, it would be best to do this before radiation or within a few weeks of starting radiotherapy. It is obviously important to ensure careful, clean surgical technique. Sharp bony edges must be smoothed, and primary soft tissue closure should be achieved where possible without overreduction of alveolar bone such that adjacent teeth or jaw structure are compromised. Should prophylactic antibiotics be used? It is probably prudent to use antibiotics in this group of patients, even though they would not be used before simple extractions in the normal population. Immediate preoperative chlorhexidine rinse may be beneficial, but there is no evidence to make this mandatory.

Cite this as: J Can Dent Assoc 2010;76:a36

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It is incumbent on all of us to stay current with the literature, especially in terms of new developments that question previous recommendations and accepted philosophies. This is not the first time standards of care have been questioned, then modified or completely rewritten. It is inherent in science and part of what adds to the complexity of and interest in our ever-changing profession. There is considerable value in repeating experiments to provide corroborating support to or question previously accepted theories and practices. a THE AUTHOR Dr. Archie Morrison is an associate professor in the department of oral and maxillofacial surgery, division of surgery, faculty of dentistry, Dalhousie University, Halifax, Nova Scotia. Email: [email protected]

References 1. Marx RE. A new concept in the treatment of osteoradionecrosis. J Oral Maxillofac Surg. 1983;41(6):351-7. 2. Marx RE, Johnson RP. Studies in the radiobiology of osteoradionecrosis and their clinical significance. Oral Surg Oral Med Oral Pathol. 1987;64(4):379-90. 3. Curi MM, Dib LL. Osteonecrosis of the jaws: a retrospective study of the background factors and treatment in 104 cases. J Oral Maxillofac Surg. 1997;55(6):540-4; discussion 545-6. 4. Annane D, Depondt J, Aubert P, Villart M, Gehanno P, Gajdos P, et al. Hyperbaric oxygen therapy for radionecrosis of the jaw: a randomized placebo-controlled, double-blind trial from the ORN96 study group. J Clin Oncol. 2004;22(24):4893-900. Epub 2004 Nov 1. 5. Maier A, Gaggl A, Klemen H, Santler G, Anegg U, Fell B, et al. Review of severe osteoradionecrosis treated by surgery alone or surgery with postoperative hyperbaric oxygenation. Br J Oral Maxillofac Surg. 2000;38(3):173-6. 6. D’Souza J, Goru J, Goru S, Brown J, Vaughan ED, Rogers SN. The influence of hyperbaric oxygen on the outcome of patients treated for osteoradionecrosis: 8 year study. Int J Oral Maxillofac Surg. 2007;36(9):783-7. Epub 2007 Jul 5.

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What dose of epinephrine contained in local anesthesia can be safely administered to a patient with underlying cardiac disease during a dental procedure? Background pinephrine is commonly used in health care and has multiple applications. Two frequent and often life-saving uses are the management of anaphylaxis and cardiac arrest. The word has a Greek origin and literally means “on” (epi) the “kidney” (nephros) referring to the anatomic location (the adrenal gland) where the drug is produced. Confusion still exists regarding the

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dose limits for epinephrine, particularly when the drug is administered to patients with underlying cardiovascular disease. Epinephrine was first added to the local anesthetic ester, procaine, over 100 years ago. Like the no-longer-used procaine, all currently available dental local anesthetics in North America cause some degree of vasodilation. This vasodilatory effect poses several problems for the clinician:

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bleeding is noted at the site of injection; absorption of the anesthetic into the blood stream is rapid, shortening the duration of effect; and the rapid absorption results in higher, potentially dangerous, plasma levels. To overcome these disadvantages, a vasoconstrictor is added to most local anesthetics, with epinephrine being the most common. The Effects of Epinephrine The physiologic effects of epinephrine are numerous, as it is responsible for the “fight or flight” response seen in all animals including humans. The variation in response depends in part on the number and predominant type of adrenergic receptors present in the target organ and on the physiologic reflex response that attempts to minimize the effects of sympathetic stimulation. As an adjunct to anesthetic, the effect this drug has on heart rate, stroke volume, cardiac output, heart rhythm, myocardial oxygen demand and peripheral vascular resistance must be appreciated. Epinephrine’s effect on blood pressure depends on the dose and route of administration. Small doses or doses administered subcutaneously may result in little or no change in blood pressure. This is often due to the combination of a slight elevation in systolic pressure and a lowering of diastolic pressure, resulting in little change in mean arterial pressure. Larger doses, particularly when given intravascularly, can cause a rapid elevation in blood pressure due primarily to peripheral vasoconstriction. Epinephrine increases heart rate and the force of ventricular contraction, which ultimately increases cardiac output. The elevation in cardiac workload increases myocardial oxygen consumption. This is a concern in an individual suffering from cardiac disease, particularly given that the beneficial coronary vasodilatory effect of epinephrine is diminished or absent in the presence of coronary vessel atherosclerosis. A further risk to the cardiac patient is the ability of epinephrine to irritate cardiac pacemaker cells and cause dysrhythmias. Thus, the injudicious use of epinephrine can be harmful to a patient with cardiac disease. Assessing the Patient A history is crucial in determining which cardiac patients are at particular risk during a dental procedure. Patients with unstable coronary syndrome (unstable angina, recent myocardial infarction [MI]), decompensated heart failure, significant dysrhythmia or severe valvular disease seem to

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be at particular risk from the effects of epinephrine. For these patients, elective dental treatment should be postponed until their cardiac status has been medically or surgically optimized. Traditionally, a 6-month wait following an MI was recommended before proceeding with noncardiac elective surgery to minimize the risk of perioperative re-infarction and death. This recommendation was adopted by dentistry even though the myocardial demands and stress of dental procedures are thought to be considerably less than those associated with the orthopedic, abdominal and thoracic procedures for which the guidelines were developed. More recently, a 4- to 6-week wait following an MI has been suggested as adequate when risk factors, such as smoking, hypertension and dyslipidemia, are controlled and recent stress testing has not indicated residual myocardium at risk.1 For patients determined to be medically capable of undergoing general dentistry, pain control is essential, particularly in those with cardiac disease. Pain and other stressors can result in a dramatic endogenous release of epinephrine and norepinephrine, which can affect the diseased heart deleteriously. Although the importance of good local anesthesia technique cannot be overemphasized, the addition of epinephrine to local anesthetics improves both the depth and duration of anesthesia. Thus, the use of some exogenous epinephrine is beneficial in this group of patients, but what is a safe dose in this at risk population? One of the most frequently quoted suggestions is that of Malamed 2 who recommended a maximum dose of 40 μg epinephrine per dental appointment in this patient population. Unfortunately, no current recommendation regarding the maximum amount of epinephrine that can be safely administered to a cardiac patient undergoing dentistry is based on sound scientific evidence. Given the population and the risk of an untoward event, ethical considerations likely preclude a study to obtain such evidence. Nevertheless, research has demonstrated that the administration of local anesthesia containing epinephrine does affect the heart. For patients requiring emergent dental care who suffer unstable cardiac disease (recent MI, unstable angina, certain dysrhythmias, significant valvular disease, decompensated heart failure), epinephrine should be minimized and used with caution. These patients are best managed by people specifically trained in their assessment, monitoring and management.

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For patients with “stable” cardiac disease, it is still prudent to administer a minimal amount of epinephrine while always avoiding intravascular injections. Although pain control is of paramount importance, the potentially deleterious effect of epinephrine can be minimized by limiting the amount to 40 μg. There is no evidence to support exceeding this dose for such patients. This amount is contained in 2 cartridges of 1:100 000 or 4 cartridges of 1:200 000 (there is little benefit from using the 1:100 000 concentration of epinephrine for routine dentistry). 3 Although the half life of epinephrine is short, exceeding 40 μg epinephrine per appointment cannot be recommended unless the patient’s cardiac status is monitored continuously during the procedure. a

Cite this as: J Can Dent Assoc 2010;76:a37

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THE AUTHOR Dr. Ben Davis is associate professor in the department of oral and maxillofacial sciences and head of the division of oral and maxillofacial surgery, Dalhousie University, Halifax, Nova Scotia. Email: [email protected]

References 1. Fleisher LA, Beckman JA, Brown KA, Calkins H, Chaikof EL, Fleishmann KE, et al. 2009 ACCF/AHA focused update on perioperative beta blockade incorporated into the ACC/AHA 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery: a report of the American college of cardiology foundation/American heart association task force on practice guidelines. Circulation. 2009;120(21):e169-276. Epub 2009 Nov 2. 2. Pharmacology of vasoconstrictors. In: Malamed SF, editor. Handbook of local anesthesia. 5th ed. St. Louis: Elsevier Mosby; 2004. p. 41-54. 3. Becker DE, Reed KL. Essentials of local anesthetic pharmacology. Anesth Prog. 2006;53(3):98-108.

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How are odontogenic infections best managed? Background ental infections, including gingivitis, periodontitis, dental caries and odontogenic infections, result in numerous dental visits each year in Canada. They can range in severity from a mild buccal space infection to a severe life-threatening multi-space infection. All dentists should be comfortable with prompt diagnosis and management of these types of infections. This review of odontogenic infections describes causative organisms, management including appropriate antibiotic selection and the indications for referral to a specialist. Most odontogenic infections are caused by more than 1 species of the bacteria normally found within the oral cavity. Roughly 50% of odontogenic infections are caused by anaerobic bacteria alone, 44% by a combination of aerobic and

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anaerobic bacteria and only 6% by aerobic bacteria alone.1 The most common species of bacteria isolated in odontogenic infections are the anaerobic gram-positive cocci Streptococcus milleri group and Peptostreptococcus.2 Anaerobic gramnegative rods, such as Bacteroides (Prevotella) also play an important role. Anaerobic gram-negative cocci and anaerobic gram-positive rods have little effect.2 Odontogenic infections progress through 3 stages: inoculation, cellulitis and abscess (Table 1).3 Bacteria gain entrance to the surrounding facial spaces by direct extension from the periapical region of the involved tooth. The pattern of spread is predictable depending on the relationship between the point of attachment of the adjacent muscle and the tooth apex.4

Table 1 Characteristics of the 3 stages of infection Characteristic

Inoculation

Cellulitis

Abscess

Duration (days)

0–3

2–5

4–10

Discomfort Palpation Pus

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Mild

Severe, diffuse

Mild, localized

Soft, doughy

Firm, indurated

Fluctuant, tender

None

None

Present

Skin

Normal

Red

Red periphery

Severity

Minimal

Greater

Less

Bacterial species

Aerobic

Mixed

Anaerobic

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