IntroductionIn the following lines we give some recommendations for the use of local anesthesia in patients undergoing surgical interventions with local anesthesia, emphasizing that the most important is the use of solutions that allow the administration of relatively high amounts of solution to be able to achieve readministrations throughout the surgery if it is extensive and long. They should also carry adrenaline as a vasoconstrictor to help better see the operating field and lengthen the effect of anesthesia.
Local anestheticsIn implantology, local anesthetic solutions are used to safely administer larger quantities, since sometimes all the implants in one arch have to be placed. It has the advantage that we do not need to achieve pulp anesthesia, the most difficult to achieve, and that anesthetizing bone and mucosa is fortunately much easier.
The most commonly used solutions are 2% lidocaine with 1:100,000 adrenaline (10 µg/ml) or 1:80,000 (12.5 µg/ml), 4% articaine with 1:100,000 adrenaline (10 µg /ml) and 0.5% bupivacaine with epinephrine 1:200,000 (5 µg/ml). This last solution with bupivacaine is not very effective in achieving pulpal anesthesia (1) (fortunately in Implantology this is not the most important thing) but it is a long-lasting anesthetic in soft tissues or bone. In Table 1 we have the maximum number of cartridges that can be administered for each of these solutions in an adult person who weighs 70 kg or more. Observe in Table 1 that local dental anesthesia cartridges can be 1.8 ml (the standard cartridge) and 1.7 ml as some articaine manufacturer has, thus Ultracain® cartridges are 1.7 ml ( Figure 1) and therefore allow more cartridges to be administered to give the same amount of anesthetic solution as 1.8 cartridges, such as those of Meganest®, also 4% articaine.
The bupivacaine solution allows for a high number of cartridges. It is very interesting to observe how the maximum recommended doses in medical practice are higher than those in dental practice. Thus, with bupivacaine solution, the maximum dental dose is 90 mg, but in hospital medical practice it is 150-225 mg (2, 3). The fundamental reason is that the professional practice of dentistry is mostly ambulatory, where it is more difficult to manage adverse reactions than in medical practice, especially in hospitals, considering this fact one of the keys to the great safety of dental practice (6 ).
A detail that may draw our attention refers to the differences between lidocaine and articaine. Articaine is distributed at 4%, twice the concentration of lidocaine, which is 2%. “In vitro” studies on the anesthetic characteristics of articaine and lidocaine show that they have very similar properties (7); also in its clinical efficacy when comparing 2% lidocaine and articaine anesthesia solutions (8). And also in experimental acute toxicity studies with animals there is little difference between both anesthetics (9, 10). However, having twice the concentration of articaine allows more powerful infiltrative anesthesia to be achieved to achieve pulpal anesthesia and somewhat longer lasting, and its great advantage is the peculiar pharmacokinetic characteristics with a half-life of only 25 minutes instead of 100 minutes. of lidocaine, or a clearance level of 5.8 liters instead of 0.9 liters for lidocaine (11, 12). These pharmacokinetic advantages of articaine are achieved because it has an ester side chain that is degraded by plasmatic pseudocholinesterases even before it reaches the liver (13), so that higher amounts of anesthetic can be administered in dentistry, 400 mg instead of Lidocaine 300 mg.
Some authors consider that the dental and medical doses of articaine should be the same, 500 mg (5), although this is not our opinion. With bupivacaine, the accepted criteria are more restrictive due to the risk of cardiotoxicity that this anesthetic can occasionally cause, generally with doses greater than 90-100 mg and after intravascular injection (14, 15).
Another interesting aspect is the concentration of adrenaline. The standard is 1:100,000 (10 µg/ml). Articaine has this concentration, but lidocaine solutions in Spain can have this concentration or a slightly higher one, 1:80,000 (12.5 µg/ml). In the United States, the 1:100,000 concentration is the standard and clinical studies have shown that there are practically no differences in solutions with either concentration. However, there are differences in the indications in patients with medical problems. Thus, patients with:
1. Non-selective ß1 and ß2 beta blockers (5, 16, 17) (Propranolol-Sumial®, Timolol-Timoftol®, Nadolol-Solgol®, Carteolol-Arteolol®, Labetalol-Trandate®, Oxprenolol-Trasicor®, Sotalol-Sotapor®) , due to the risk of hypertensive crises and reduced heart rate (bradycardia). There is no problem with cardioselective ß1 beta blockers (Atenolol-Tenormin®, Metoprolol-Blokium® and Seleken®). The maximum dose of adrenaline in these cases is 27 µg, equivalent to 1.5 cartridges of 1:100,000 adrenaline.
2. Antiparkinsonian drugs of the ICOMT type (18) (Tolcapone-Tasmar®, Entacapone-Comtan®), since they produce an inhibition of Catechol-O-Methyl-Transferase (ICOMT), an enzyme that inactivates levodopa and also catecholamines (adrenaline, norepinephrine and levonordefrin), producing an increase in the plasmatic levels of catecholamines of the SALTs of local anesthesia and a risk of arrhythmias. The maximum dose of adrenaline in these cases is 27 µg, equivalent to 1.5 cartridges of 1:100,000 adrenaline.
3. Cardiovascular patients in ASA 3. Patients with severe systemic disease limiting activity but not disabling (no symptoms with ordinary exercise) (5, 16, 19-21):—Uncontrolled hypertension with blood pressure > 95-115 and/or 160-200.—Heart failure with respiratory distress (dyspnea) with exercise but not at rest.—Heart transplant.—Patients older than 6 months since:•Acute myocardial infarction.•Stroke.•Coronary artery bypass grafting.
The maximum dose of adrenaline in these cases is 40 µg, equivalent to 2.2 cartridges of 1:100,000 adrenaline.
4. Amphetamines and psychostimulant derivatives (18) to treat attention disorders and hyperactivity, generally in children and adolescents (Amphetamine, Methamphetamine, Dextroamphetamine, Methylphenidrate-Medikinet®, Atomoxetine-Strattera®), due to the risk of myocardial infarctions and strokes . The maximum dose of adrenaline in these cases is 40 µg, equivalent to 2.2 cartridges of 1:100,000 adrenaline.
5. Digoxin (18) (cardiotonic used in heart failure and antiarrhythmic), because in the presence of exogenous catecholamines from dental SALTs (adrenaline, norepinephrine, levonordefrin) the risk of producing cardiac arrhythmias increases. The maximum dose of adrenaline in these cases is 40 µg, equivalent to 2.2 cartridges of 1:100,000 adrenaline.
6. Tricyclic and tetracyclic antidepressants (5, 16, 17) (Amitriptyline, Nortriptyline, Maprotiline, Imipramine, Trimipramine, Clomipramine, Doxepin), due to the risk of arrhythmias and hypertensive crises. Monoamine oxidase inhibitor (MAOI) antidepressants and modern serotonin reuptake inhibitors (Fluoxetine, Paroxetine, Fluvoxamine, Citalopram, Escitalopram, Sertaline) are not contraindicated. The maximum dose of adrenaline in these cases is 50 µg, equivalent to 2.7 cartridges of 1:100,000 adrenaline.
7. Old antihypertensives (guanethidine, reserpine, Rauwolfia derivatives) (17), which are currently practically not used, due to the risk of arrhythmias and, to a lesser extent, hypertensive crises. The maximum dose of adrenaline in these cases is 50 µg, equivalent to 2.7 cartridges of 1:100,000 adrenaline.
8. General anesthesia with Halothane and Thiopental (17), due to risk of arrhythmias. Fortunately, usually when general anesthesia is used, local anesthesia is not used, so this situation is unlikely to happen. The maximum dose of adrenaline in these cases is 100 µg, equivalent to 5.5 cartridges of 1:100,000 adrenaline.
In these patients, adrenaline is not contraindicated, but both its quantity is limited, as we have already seen in each case, and its maximum concentration is 1:100,000 (10 µg/ml), with which concentrations greater than 1: 80,000 (12.5 µg/ml) or even greater than 1:50,000 (20 µg/ml) would be contraindicated. In these cases, a good alternative is the 4% articaine solution with adrenaline 1:200,000 (5 µg/ml), which allows us to administer double the number of cartridges in these patients. Of course, 0.5% bupivacaine with 1:200,000 adrenaline (5 µg/ml) can also be used.
Table 2 shows the durations of anesthesia in the soft tissues and after surgery the time it takes for the first pain to appear (note that it appears before the paresthesias in the soft tissues disappear). It is important to be clear that anesthesia in Implantology is fundamentally for soft tissue and bone.
Finally, when an entire arch is going to be placed with implants and the intervention is going to be long, it is advisable to anesthetize in parts, in such a way that the area where the surgery begins is anesthetized first and as work is finished on that area. area and a new one is started, local anesthesia is administered in that new area. The advantage of this method is that if we administer all the anesthesia at the beginning and the intervention is prolonged, when we reach the end, that area will not be anesthetized and we may run the risk of overdosing the local anesthetic solution.
SedationIn dentistry, sedation is indicated when some of these circumstances occur (21, 25, 26):1. Very anxious patients.
2. Difficult and/or lengthy dental procedures.
3. Patients whose health is classified as ASA 3 in whom stress aggravates their medical situation. ASA is the physical status classification of the American Society of Anesthesiology and they are patients with severe systemic disease that limits their activity but does not incapacitate them (they do not have symptoms with ordinary exercise).
4. Patients with easy retching and nausea making dental treatment difficult.
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In Implantology we can find all these circumstances, but I want to draw attention to point number two, of long or difficult cases, since on many occasions when we have to put several implants it is easy for it to be prolonged in time 2- 3 hours or more. Table 3 shows the drugs and routes most used in dentistry to achieve sedation and their success in highly anxious patients (21).
In Implantology, when we have long interventions, and even if the patients are not anxious, we need something more than local anesthesia. The options we have in Table 3 are often complicated for us. General anesthesia and intravenous sedation techniques require special equipment and the participation of an anesthetist due to the risk they entail. Intramuscular and intranasal techniques also require an anesthetist to monitor the patient's progress. All the techniques discussed so far carry risks and for this reason a professional anesthetist is necessary.
The best options for a dentist are the technique with nitrous oxide inhalation with oxygen, which has a high success rate in very anxious patients, 80%, and is very safe; This technique does not require an anesthetist and can be used by a dentist, although it requires a course for its correct use and special equipment (21, 27). The use of the oral route is also very useful, although its results are more modest than other techniques, they have the advantage that they do not require an anesthetist or special equipment and that they are very safe methods in a professional who knows well the drugs used. .
Orally, the best medicine we can use is Triazolam (26, 28) (Halcion®) in 0.125 mg tablets. It is a benzodiazepine, which begins its action after 15 minutes and the effect is maximum at 60 minutes, its action lasting from this moment about 2 hours, producing a rapid recovery of the patient and the residual sedative effect rarely lasting 6 hours. The dose used is 2 tablets in adults (0.25 mg) and in people over 65 years of age a single tablet (0.125 mg) is recommended. An advantage of this drug is the little depression it produces in the respiratory and cardiovascular systems compared to other sedatives, which makes it safe. An additional advantage of Triazolam is that it frequently produces anterograde amnesia, so that the patient does not remember what happened during the intervention, which is especially interesting in difficult surgeries in which discomfort can occur despite local anesthesia.
An alternative, when benzodiazepines cannot be used, which are the first choice, is Hydroxyzine (29, 30) (Atarax®), an antihistamine, in 25 mg tablets. In adults, 50-100 mg are administered 60 minutes before the intervention and the effect lasts about 4 hours, but it usually leaves a residual sedative effect that can sometimes last up to 24 hours. One advantage of Hydroxyzine is the low respiratory depression it produces and therefore its safety.
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