Daniel A Haas’s research while affiliated with University of Toronto and other places

Alterations in arterial PaCO₂ can influence local anesthetic toxicity. The objective of this study was to evaluate the effect of stress-induced changes in PaCO₂ and PaO₂ on the seizure threshold of lidocaine and articaine. Lidocaine (2% with 1 : 100,000 epinephrine) or articaine (4% with 1 : 100,000 epinephrine) was administered intravenously under rest or stress conditions to 36 rats separated into 4 groups. Propranolol and prazosin were administered preoperatively to minimize cardiovascular effects of epinephrine. Mean arterial pressure (MAP), heart rate (HR), and arterial pH, PaCO₂, and PaO₂ were measured. Results showed no differences in MAP, HR, or pH. Stress significantly increased the latency period for the first tonic-clonic seizure induced by a toxic dose of both lidocaine and articaine (P < .05). Seizures were brought on more rapidly by articaine. No significant difference between toxic doses of lidocaine and articaine was noted. Stress raised the seizure threshold dose for both drugs and significantly (P < .01) increased arterial PaO₂ from 94.0 ± 1.90 mm Hg to 113.0 ± 2.20 mm Hg, and reduced PaCO₂ from 36.0 ± 0.77 mm Hg to 27.0 ± 0.98 mm Hg. In conclusion, reduction in PaCO₂ and/or increase in PaO₂ raised the seizure threshold of lidocaine and articaine. This study also confirmed that lidocaine and articaine have equipotent central nervous system toxicity.

Background: Local anesthetics (LA) are safe and effective; however, complications associated with their use occur. Paresthesia, defined as persistent anesthesia, numbness or tingling, or a painful neuropathy known as dysesthesia, represent potential complications. Objective: To determine the difference in the incidence of oral paresthesia among the five currently available LAs in the United States (US). Methods: Records of voluntarily reported oral paresthesia involving dental LAs over the period of November 1997 to September 2008 were obtained from the US Food and Drug Administration (FDA) Adverse Event Reporting System (AERS). Exclusions were made if it was known that the dental procedures involved surgery. Chi-Square analysis was used to compare expected frequencies, based on US LA sales data obtained from the research company Strategic Data Marketing, to observed reports of non-surgical oral paresthesia made to the AERS. Results: In all, 248 cases of paresthesia following non-surgical dental procedures were reported. Most (94.5%) of these cases involved mandibular nerve blockade. The lingual nerve was affected in 89.0% of cases, the inferior alveolar nerve in 7.3%, and both were affected simultaneously in 3.7% of cases. Reported cases involving the drugs prilocaine 4% and articaine 4% were 7.4-times and 3.6-times, respectively, greater than expected (2, p<0.0001) based on LA usage by US dentists. Conclusions: These data suggest that oral paresthesia is more common following the use of 4% LA formulations. These findings are consistent with a number of similar reports from other countries. Until further studies are available, dental practitioners should consider these results when assessing the risks and benefits of using higher concentration LAs for mandibular block anesthesia.

Several studies have suggested that the likelihood of paresthesia may depend on the local anesthetic used. The purpose of this study was to determine if the type of local anesthetic administered had any effect on reports of paresthesia in dentistry in the United States. The authors obtained reports of paresthesia involving dental local anesthetics during the period from November 1997 through August 2008 from the U.S. Food and Drug Administration Adverse Event Reporting System. They used chi(2) analysis to compare expected frequencies, on the basis of U.S. local anesthetic sales data, with observed reports of oral paresthesia. During the study period, 248 cases of paresthesia occurring after dental procedures were reported. Most cases (94.5 percent) involved mandibular nerve block. The lingual nerve was affected in 89.0 percent of cases. Reports involving 4 percent prilocaine and 4 percent articaine were 7.3 and 3.6 times, respectively, greater than expected (chi(2), P < .0001) on the basis of local anesthetic use by U.S. dentists. These data suggest that paresthesia occurs more commonly after use of 4 percent local anesthetic formulations. These findings are consistent with those reported in a number of studies from other countries. Until further research indicates otherwise, dentists should consider these results when assessing the risks and benefits of using 4 percent local anesthetics for mandibular block anesthesia.

A medical emergency can occur in any dental office, and managing it successfully requires preparation. The dentist should develop a basic action plan that is understood by all staff members. The goal is to manage the patient's care until he or she recovers fully or until help arrives. The most important aspect of almost all medical emergencies in dentistry is to prevent or correct insufficient oxygenation of the brain or heart. The dentist or a staff member needs to position (P) the patient appropriately. He or she then needs to assess and, if needed, manage the airway (A), breathing (B) and circulation (C). The dentist and staff members then can consider 'D,' which stands for definitive treatment, differential diagnosis, drugs or defibrillation. A team approach should be used, with each staff member trained in basic life support and understanding the role expected of him or her ahead of time. Clear and effective communication is essential during any emergency. All staff members should understand the basic action plan so that they can put it into effect should any emergency arise in the dental office. Preparing staff members is integral to the successful management of a medical emergency in the dental office.

Local anesthetics are believed to be the most frequently used drugs in clinical dentistry, and although they are generally regarded as safe, some adverse reactions can be expected and do occur. The purpose of this study was to obtain, by means of a mail survey, information on the types and amounts of local anesthetics used by Ontario dentists during 2007. A survey requesting data on the annual use of injectable local anesthetics was mailed to all 8,058 dentists licensed by the Royal College of Dental Surgeons of Ontario in 2007. The effective response rate to the single mailing was 17.3% (1,395 respondents). By extrapolation, the estimated use of local anesthetics by all Ontario dentists during 2007 was determined to be about 13 million cartridges, which represents an average of 1,613 cartridges per dentist per year. Lidocaine with epinephrine 1:100,000 was the most commonly used formulation with 37.31% of total anesthetic use, followed by articaine with 1:200,000 epinephrine (27.04%) and articaine with 1:100,000 epinephrine (17.16%). Overall, local anesthetics combined with a vasoconstrictor accounted for more than 90% of total anesthetic use. A minority of survey respondents (15.68%) indicated that their pattern of anesthetic use had changed significantly in the past few years. Patterns of use were similar for early and late survey respondents. These data provide a current account of the use of local anesthetics by Ontario dentists.

Paresthesia is an adverse event that may be associated with the administration of local anesthetics in dentistry. The purpose of this retrospective study was to analyze cases of paresthesia associated with local anesthetic injection that were voluntarily reported to Ontario"s Professional Liability Program (PLP) from 1999 to 2008 inclusive, to see if the findings were consistent with those from 1973 to 1998 from this same source. All cases of nonsurgical paresthesia reported from 1999 to 2008 were reviewed; cases involving surgical procedures were excluded. Variables examined included patient age and gender, type and volume of local anesthetic, anatomic site of nerve injury, affected side and pain on injection or any other symptoms. During the study period, 182 PLP reports of paresthesia following nonsurgical procedures were made; all but 2 were associated with mandibular block injection. There was no significant gender predilection, but the lingual nerve was affected more than twice as frequently as the inferior alveolar nerve. During 2006-2008 alone, 64 cases of nonsurgical paresthesia were reported to PLP, a reported incidence of 1 in 609,000 injections. For the 2 local anesthetic drugs available in dental cartridges as 4% solutions, i.e., articaine and prilocaine, the frequencies of reporting of paresthesia were significantly greater than expected (chi2, exact binomial distribution; p < 0.01) based on their level of use by Ontario dentists. These data suggest that local anesthetic neurotoxicity may be at least partly involved in the development of postinjection paresthesia.

The objective of this study was to determine the effect of time on the clinical efficacy of topical anesthetic in reducing pain from needle insertion alone as well as injection of anesthetic. This was a randomized, double-blind, placebo-controlled, split-mouth, clinical trial which enrolled 90 subjects, equally divided into 3 groups based upon time (2, 5, or 10 minutes) of topical anesthetic (5% lidocaine) application. Each group was further subdivided into 2: needle insertion only in the palate or needle insertion with deposition of anesthetic (0.5 mL 3% mepivacaine plain). Each subject received drug on one side and placebo on the other. Subjects recorded pain on a 100-mm visual analog scale (VAS). The results showed that for needle insertion only, 5% lidocaine reduced pain as determined by a significant difference in mean VAS after 2 minutes (20.1 mm, P < .002), 5 minutes (15.7 mm, P < .022), and 10 minutes (13.7 mm, P < .04), as analyzed by paired t tests. For needle insertion plus injection of local anesthetic, a significant difference in mean VAS was noted only after 10 minutes (14.9 mm, P < .031), yet pain scores for both topical anesthetic and placebo were elevated at this time point resulting in no reduction in actual pain. Time of application did not result in a significant difference in effect for either needle insertion only or needle insertion plus injection of local anesthetic, as analyzed by 1-way analysis of variance (ANOVA). In conclusion, topical anesthetic reduces pain of needle insertion if left on palatal mucosa for 2, 5, or 10 minutes, but has no clinical pain relief for anesthetic injection.

Because empathic patient interactions by dentists are associated with improved patient outcomes, self-reported declines in empathy during dental student training are a concern. This study examined differences in empathy in 178 dental students at the University of Toronto and the University of Western Ontario from years one through four using an anonymous self-report web-based survey in a cross-sectional design. To localize the effects of training on empathy, an instrument that separately evaluated emotive (Emo) and cognitive (Cog) types of empathy in both personal (Per) and professional (Pro) contexts was developed, using items modified from previously validated scales and resulting in an empathy scale with four thirteen-item subscales (Per-Emo, Per-Cog, Pro-Emo, Pro-Cog). The response rate was 36.5 percent, and all subscales showed good reliability and validity. A 2x2x4 mixed design ANOVA tested differences in mean scores among the four subscales across the four years of training. Following a significant three-way interaction, subanalyses demonstrated no significant effects in the Per-context, but a significant year by empathy-type interaction in the Pro-context. Post hoc analyses of Pro measures indicated year three emotive empathy scores were significantly lower than earlier years, whereas years three and four cognitive empathy scores were significantly higher. This isolated decrease in Pro-Emo empathy with an increase in Pro-Cog empathy is consistent with the development of "professional empathy," described elsewhere as detached concern.

Objective: The demonstration of empathy in dentist-patient interactions significantly affects treatment outcomes, however studies have shown that empathy declines as dental students progress through training. In our previous work with dental students, evidence of decreasing emotive empathy (Emo) combined increasing cognitive empathy (Cog), localized to the professional context, was interpreted as being consistent with the formation of detached concern as a model of professional empathy. If detached concern is a sensible description of professional empathy in dentists, the pattern of lower emotive empathy and higher cognitive empathy in the professional (Pro) context relative to the personal (Per) context should continue into dental practice. This hypothesis was tested. Methods: Two cohorts of Ontario dentists (5-6 yrs in practice and 10-11 yrs in practice) were recruited for an anonymous web-based self-report survey of empathy and data were analyzed using a three-way mixed design ANOVA. Results: Of 606 dentists, 123 completed the full survey (response rate of 20.2%). Overall there was no difference in mean empathy scores between the two cohorts (F1,121=1.47, ns). With regard to the primary hypothesis, the pattern of data was opposite to that expected. Emotive empathy was higher than cognitive in both Per and Pro contexts (a main effect of empathy type: F1,121=414.42, p<.001), and the two way interaction of type by context demonstrated that this difference was actually larger in the Pro context than Per context (F1,121=195.07, p<.001). Conclusions: The observed pattern of higher Emo and lower Cog empathy in the professional context suggests detached concern may be an unsuitable description of professional empathy because emotive responding seems to be a strong feature of clinical empathy in the experienced clinicians. Therefore, further work is required to understand the (apparently temporary) decline in emotive empathy among dental students.

The risk for complications while providing moderate and deep sedation is greatest when caring for patients already medically compromised. It is reassuring that significant untoward events can generally be prevented by careful preoperative assessment, along with attentive intraoperative monitoring and support. Nevertheless, we must be prepared to manage untoward events should they arise. This continuing education article will review critical aspects of patient management of respiratory and cardiovascular complications.