Daniel A. Haas

Neuropeptide y administration acutely increases hypothalamic corticotropin-releasing factor immunoreactivity: Lack of effect in other rat brain regions

The effect of acute central administration of Neuropeptide Y (NPY) to adult male rats on the brain content of corticotropin-releasing factor immunoreactivity (CRF-ir) was investigated. The brain regions studied included frontal cortex, hippocampus, medulla-pons, midbrain-thalamus, cerebellum, neurointermediate lobe of pituitary, median eminence and the remaining hypothalamus. CRF-ir was determined in each of these regions using a radioimmunoassay specific for rat CRF. CRF-ir was found to be significantly increased in the major site of CRF localization in the brain, the hypothalamus, in NPY-treated rats as compared to vehicle-treated controls either 15 minutes (p less than 0.025) or 45 minutes (p less than 0.005) post-injection. This increase was localized to the median eminence (p less than 0.05 after 15 minutes, p less than 0.01 after 45 minutes). No statistically significant differences were noted in any of the other brain regions assessed. Plasma adrenocorticotropin levels were also found to increase following NPY treatment, an effect which became significant after 45 minutes (p less than 0.05). These data show that NPY can alter the content of hypothalamic CRF and may play a role in its regulation.

Single or repeated mild stress increases synthesis and release of hypothalamic corticotropin-releasing factor

The effect of a specific mild stress on the levels of corticotropin-releasing factor immunoreactivity (CRF-ir) in the hypothalamus of adult male rats was determined using a radioimmunoassay specific for rat CRF. A single 5 min restraint significantly increased CRF-ir in the median eminence 24 h later compared to appropriate controls (P less than 0.025), with no change detected earlier. Plasma ACTH, an indirect index of CRF release, was significantly elevated within 15 min (P less than 0.025). Repetition of a mild stress daily for 9 days (P less than 0.01), or a single episode of handling (P less than 0.05), both resulted in significantly increased CRF-ir in the whole hypothalamus 24 h later. Blockade of axonal transport by intracisternal colchicine decreased CRF-ir in the median eminence 24 h later (P less than 0.005). Inhibition of protein synthesis by anisomycin during a single 5 minute restraint resulted in significantly decreased CRF-ir in the median eminence 24 h later compared to vehicle-injected stressed rats (P less than 0.005) or to anisomycin-injected unstressed controls (P less than 0.025). These data show that mild stress increased net hypothalamic CRF content as a result of the balance between augmented synthesis and augmented release.

Radiographic localization of mandibular anesthesia landmarks.

The objective of this study was to assess whether bony landmarks used for the standard inferior alveolar nerve block can be used to accurately determine the position of the mandibular foramen and whether panoramic radiographs are appropriate for this purpose. A total of 11 landmarks from 79 panoramic radiographs and 70 corresponding cases of oblique (45-degree) cephalometric radiographs were examined. Ten measurements of the distance from each landmark to the mandibular foramen, as well as 6 ratios from these distances, were calculated from all radiographs. The results showed that the position of the mandibular foramen was highly individualistic and not consistently related to traditional clinical landmarks. Panoramic radiographs were as good as oblique cephalometric radiographs for the locating of the mandibular foramen. No age or gender correlations were found. It was concluded that the mandibular foramen can be localized in panoramic radiographs but that its relation to bony landmarks is highly variable.

Gonadal regulation of corticotropin-releasing factor immunoreactivity in hypothalamus

The effect of gonadectomy and subsequent gonadal steroid administration on hypothalamic corticotropin-releasing factor immunoreactivity (CRF-ir) in male and female rats was determined using a radioimmunoassay specific for rat CRF. When compared to appropriate controls, gonadectomy resulted in significantly decreased CRF-ir in both males and females (p less than 0.025). Short-term replacement with testosterone or estradiol did not significantly alter hypothalamic CRF-ir. Acute IC administration of gonadotropin-releasing hormone to male rats significantly decreased CRF-ir in the median eminence 15 minutes later. Chronic administration of estradiol for 3 weeks significantly reduced CRF-ir in ovariectomized rats (p less than 0.005). This decrease was shown not to correlate to the marked increase in anterior pituitary weight (r2 = 0.063, not significant). Chronic administration of estradiol to hypophysectomized female rats significantly decreased hypothalamic CRF-ir (p less than 0.01), an effect localized to the median eminence (p less than 0.005). These data imply that the gonadectomy-induced reduction in hypothalamic CRF-ir was not directly mediated by the loss of gonadal steroids. Chronic estradiol treatment decreased hypothalamic CRF-ir, by a non-pituitary mechanism. These data show significant effects of the gonadal axis in the regulation of CRF in the hypothalamus in both sexes.

Neuropeptide Y-induced effects on hypothalamic corticotropin-releasing factor content and release are dependent on noradrenergic/adrenergic neurotransmission

Neuropeptide Y (NPY) administration increases both hypothalamic corticotropin-releasing factor-like immunoreactivity (CRF-ir) and plasma adrenocorticotropin (ACTH). The dependence of these effects on noradrenaline and adrenaline was investigated by selectively depleting these neurotransmitters with 6-hydroxydopamine (6-OHDA) prior to administration of NPY. This combined treatment decreased hypothalamic CRF-ir (P less than 0.025), an effect isolated to the median eminence (P less than 0.025), whereas plasma ACTH increased greatly compared to 6-OHDA treatment alone (P less than 0.0005). In order to further investigate the potential mechanism of this NPY effect, the alpha 2-adrenergic agonist clonidine was administered to normal rats. This treatment increased plasma ACTH (P less than 0.005) and decreased hypothalamic CRF-ir (P less than 0.025), an effect localized to the median eminence (P less than 0.01). The results from both of these treatments are consistent with increased release of hypothalamic CRF. These data imply that the NPY-induced effects are dependent on normal noradrenergic/adrenergic neurotransmission. Depletion of these neurotransmitters allowed NPY to profoundly stimulate CRF release with no evidence for alteration in synthesis, a result common to alpha 2 stimulation.

Mortality incidence in outpatient anesthesia for dentistry in Ontario

Studies determining anesthesia mortality rates in dentistry have been published, yet a similar investigation has never been conducted in Canada. Therefore the objective of this study was to determine the incidence of mortality when general anesthesia or deep sedation was administered by qualified dentists in the province of Ontario. Mortality data were obtained from the years 1973 to 1995 inclusive. The number of general anesthetics and deep sedations administered annually by qualified in dental offices was calculated by surveying all oral and maxillofacial surgeons and dental anesthetists in Ontario in 1990 and 1995. The results provided an estimate of 2,830,000 cases from 1973 to 1995 inclusive. Over this time period there were four deaths associated with cases in which either an oral and maxillofacial surgeon or dental anesthetist administered the general anesthetic or deep sedation, yielding a mortality rate of 1.4 per 1,000,000. This mortality incidence is similar to rates already published for outpatient dentistry.

Management of Medical Emergencies in the Dental Office: Conditions in Each Country, the Extent of Treatment by the Dentist

Dentists must be prepared to manage medical emergencies which may arise in practice. In Japan, a study was conducted between 1980 and 1984 by the Committee for the Prevention of Systematic Complications During Dental Treatment of the Japan Dental Society of Anesthesiology, under the auspices of the Japanese Dental Society.1 The results from this study showed that anywhere from 19% to 44% of dentists had a patient with a medical emergency in any one year. Most of these complications, approximately 90%, were mild, but 8% were considered to be serious. It was found that 35% of the patients were known to have some underlying disease. Cardiovascular disease was found in 33% of those patients. Medical emergencies were most likely to occur during and after local anesthesia, primarily during tooth extraction and endodontics. Over 60% of the emergencies were syncope, with hyperventilation the next most frequent at 7%. In the United States and Canada, studies have also shown that syncope is the most common medical emergency seen by dentists.2,3 Syncope represented approximately 50% of all emergencies reported in one particular study, with the next most common event, mild allergy, represented only 8% of all emergencies. In addition to syncope, other emergencies reported to have occurred include allergic reactions, angina pectoris/myocardial infarction, cardiac arrest, postural hypotension, seizures, bronchospasm and diabetic emergencies. The extent of treatment by the dentist requires preparation, prevention and then management, as necessary. Prevention is accomplished by conducting a thorough medical history with appropriate alterations to dental treatment as required. The most important aspect of nearly all medical emergencies in the dental office is to prevent, or correct, insufficient oxygenation of the brain and heart. Therefore, the management of all medical emergencies should include ensuring that oxygenated blood is being delivered to these critical organs. This is consistent with basic cardiopulmonary resuscitation, with which the dentist must be competent. This provides the skills to manage most medical emergencies, which begin with the assessment, and if necessary the treatment of airway, breathing and circulation (the ABCs of CPR). Usually, only after these ABCs are addressed should the dentist consider the use of emergency drugs. Drugs that should be promptly available to the dentist can be divided into two categories.4 The first category represents those which may be considered essential. These drugs are summarized in Table 1. The second category contains drugs which are also very helpful and should be considered as part of the emergency kit. These supplementary drugs are summarized in Table 2. The precise composition of the drug kit can vary as the presence of the drugs in this latter group may depend on the nature of the dental practice. Table 1 Essential Emergency Drugs Table 2 Additional Emergency Drugs

Management of complications during moderate and deep sedation: respiratory and cardiovascular considerations.

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.

Effect of Time on Clinical Efficacy of Topical Anesthesia

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.

Paresthesias in Dentistry

Alterations to normal oral sensory function can occur following restorative and surgical dental procedures. Paresthesia is defined as an abnormal sensation, such as burning, pricking, tickling, or tingling. Paresthesias are one of the more general groupings of nerve disorders known as neuropathies. This article reviews the extent of this oral complication as it relates to dental and surgical procedures, with specific emphasis on paresthesias associated with local anesthesia administration. This review establishes a working definition for paresthesia as it relates to surgical trauma and local anesthesia administration, describes the potential causes for paresthesia in dentistry, assesses the incidence of paresthesias associated with surgery and local anesthesia administration, addresses the strengths and weaknesses in research findings, and presents recommendations for the use of local anesthetics in clinical practice.