Anesthesia Progress Blog - Part 132

Dental Anesthesia Management

Methemoglobinemia is an uncommon but potentially serious adverse reaction to many local anesthetics and other substances. Careful review of medical and dental histories can often uncover patients who are sensitive to agents with the potential of causing methemoglobinemia. This case report is a review of the literature and demonstrates the management of methe-moglobinemia-susceptible patients.

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Dental Anesthesia Management DISCUSSION

Methemoglobinemia occurs when iron atoms in hemoglobin molecules are oxidized from their normal ferrous (Fe++) to a nonfunctional ferric (Fe+++) state, resulting in reduced oxygen delivery to the tissue level. Methe-moglobin (MetHb) is normally present in human blood at levels less than 1-2%. In normal patients, its rapid reduction back to hemoglobin is catalyzed primarily by the enzyme nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase (b5R), also called NADH-di-aphorase. Methemoglobinemia occurs when levels exceed l-2% and may be divided into inherited and acquired types. Hereditary methemoglobinemia may rarely result in long-standing congenital cyanosis with or without various developmental disturbances due to hemoglobin M. Inherited methemoglobinemia can also uncommonly present as a heterozygous or more severe homozygous autosomal deficiency of NADH reductase due to various mutations in chromosome 22. One study estimated the incidence of NADH reductase deficiency in Eskimos and Native Americans to be 15/ 20,ООО. By far, the most common causes of methemoglobinemia are acquired indirect dose-dependent toxic effects from metabolites of various drugs (see Tables 1, 2, and 3). Although patients with inherited MetHb conditions are also much more susceptible to acquired methemoglobinemia, any patient may develop this acute condition especially when given toxic doses of causative drugs. Scott et al observed cyanosis and increases in MetHb levels in all 19 healthy subjects who were given at least 900 mg of prilocaine. Estimated incidence of methemoglobinemia after topical anesthesia for bronchoscopy is 1/7000.

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Local Anesthesia Techniques in Children Receiving Nitrous Oxide-Oxygen Sedation. DISCUSSION

This clinical trial demonstrates no difference in pain control effectiveness between infiltration/intrapapillary injections and inferior alveolar block/long buccal infiltration for children undergoing mandibular pulpotomy and stainless steel crown placement.

These results fail to confirm suggested differences in 1 previous study. Pain control was effective overall for 91% of children. This result is qualitatively similar to the 88% success rate reported in the previous observational study of pediatric dentists and to the 87% rate reported for general dentists.

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The mean age of children in both groups was 78 months (SD =12 months). Thirty girls were randomized into the block group and 25 girls to the infiltration group. There was no difference in the average age or proportion of girls in each group (both P > .05). Eight children (15.4%) in the block group had previous symptoms from the tooth being treated, and again 8 children (16.7%) from the infiltration group had previous symptoms (P = .9). Roughly half of all pulpotomies were on the first primary molar only, one quarter of all pulpotomies were on the second molar only, and the remaining involved both molars. There was a good distribution of all 3 combinations of teeth treated in both groups (P = .3). The average time interval from the injection to start of the tooth preparation was 14 minutes (SD = 5 minutes) in the block group and 15 minutes (SD = 4 minutes) in the infiltration group (P = .3).

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All children were given 40% nitrous oxide via a nasal mask. After 3 minutes, the site of the injection was dried with a cotton tip applicator, and topical anesthetic (Hur-ricaine, 20% benzocaine gel) was applied for 60 seconds. The dental hygienist then opened an envelope giving the anesthetic assignment, and local anesthetic was administered. The same dental hygienist gave all the injections. Local anesthetic was administered without the dentist present. Children were randomly assigned to either the infiltration or block group using a computer algorithm (Microsoft Excel RAND function).

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Local Anesthesia Techniques in Children Receiving Nitrous Oxide-Oxygen Sedation


Healthy children who needed a pulpotomy treatment in a lower primary molar and had no contraindication for local anesthetic were eligible for the study. On the day of treatment, after the initial consultation, parents of el­igible children requiring pulpotomy were approached by office staff and informed of the study; written informed consent of the parent and assent of the child were then obtained. There were few refusals. A total of 106 children aged 5-8 years were initially enrolled. A total of 55 girls with average age of 76 months (SD = 11 months) and 46 boys with an average age of 79 months (SD = 13 months) completed the study. One child was withdrawn after consenting but before participation. Four study forms were misplaced after data collection, and those children were excluded. The study was approved by the Institutional Review Board of the University of Washington.

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Local Anesthesia Techniques in Children Receiving Nitrous Oxide-Oxygen Sedation. METHODS

The aim of this study was to test the hypothesis that dental pain control using infiltration/intrapapillary injection was less effective than inferior alveolar block/long buccal infiltration anesthesia in children. A total of 101 healthy children, aged 5-8 years, who had no contraindication for local anesthetic and who needed a pulpot-omy treatment and stainless steel crown placement in a lower primary molar were studied. A 2-group randomized blinded controlled design was employed comparing the 2 local anesthesia techniques using 2% lidocaine, 1:100,000 epinephrine. All children were given 40% nitrous oxide. Children self-reported pain using the Color Analogue Scale. The study was conducted in a private pediatric dental practice in Mount Vernon, Wash. Overall pain levels reported by the children were low, and there were no differences between conditions at any point in the procedure. Pain reports for clamp placement were block/long buccal 2.8 and infiltration/intrapapillary 1.9 (P = .1). Pain reports for drilling were block/long buccal 2.0 and infiltration/intrapapillary 1.8 (P = .7). Nine percent of children required supplementary local anesthetic: 4 of 52 (7.7%) in the block/long buccal group and 5 of 49 (10.2%) in the infiltration/intrapapillary group (P = .07). The hypothesis that block/long buccal would be more effective than infiltration/intrapapillary was not supported. There was no difference in pain control effectiveness between infiltration/intrapapillary injection and inferior alveolar block/long buccal infiltration using 2% lidocaine with 1:100,000 epinephrine when mandibular primary molars received pulpotomy treatment and stainless steel crowns.

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About this blog

Blog invites submissions of review articles, reports on clinical techniques, case reports, conference summaries, and articles of opinion pertinent to the control of pain and anxiety in dentistry.