Cognitive properties of sedation agents: comparison of the effects of nitrous oxide and midazolam on memory and mood

OBJECTIVES

To compare the effects of nitrous oxide and midazolam on cognition and mood.

DESIGN

A three-way, counterbalanced, cross-over study, using patients receiving conscious sedation for routine dental treatment.

METHODS

On each of three separate visits, patients performed a computerised test battery to determine baseline cognitive performance. Then, following administration of either midazolam, nitrous oxide, or no drug, patients re-performed the test battery. Finally, patients completed visual analogue scales assessing their subjective mood state.

RESULTS

Relative to baseline performance, midazolam administration produced significantly slower reaction times compared with nitrous oxide and no-drug conditions. Furthermore, patients receiving midazolam were impaired in accuracy relative to the other conditions on many of the cognitive tasks, particularly those assessing the recall of information. Patient performance in nitrous oxide and control conditions did not significantly differ. These results could not be explained by differences in mood between the conditions, as subjective mood ratings during midazolam or nitrous oxide administration were very similar.

CONCLUSIONS

It is important for clinicians to be aware that peri-operative recall of information is reduced in patients who have undergone midazolam sedation. This is an advantage for patients who are anxious, and do not wish to be aware of the operative treatment being performed. However, as the cognitive impairment is enduring, an adult escort and written post-operative instructions should be mandatory for midazolam sedation patients. In contrast, the use of nitrous oxide sedation does not significantly impair higher cognitive tasks and thus patients receiving nitrous oxide sedation can resume normal activities in the post-operative period.

An investigation into the need for supplementary steroids in organ transplant patients undergoing gingival surgery. A double-blind, split-mouth, cross-over study

Organ transplant patients are frequently medicated with triple immunosuppressive therapy that includes both cyclosporin and the corticosteroid, prednisolone. Many of these patients experience gingival overgrowth that necessitates surgical intervention. Chronic dosing with corticosteroids can lead to suppression of the hypothalamic-pituitary axis, and subsequent adrenocortical suppression. To circumvent possible suppression, supplementary steroids are administered to such patients prior to so-called "stressful events". We have examined the need for supplementary steroids in 20 organ transplant patients undergoing gingival surgery under local anaesthesia to correct their drug-induced gingival overgrowth. All patients were operated upon in the first half of the morning. Prior to gingival surgery, resting blood pressure (BP) and serum ACTH concentrations were determined. Immediately before surgery patients received either intravenous hydrocortisone 100 mg or placebo in random, double-blind order. Each patient required 2 gingivectomies and thus acted as their own placebo control. BP was measured at various time points throughout surgery and upto 2 h postoperatively. On completion of surgery, a further blood sample was taken to determine ACTH concentration. There was no significant difference (p>0.05) between placebo and hydrocortisone treatments for BP and ACTH measurements. No patient experienced any symptoms that were suggestive of adrenocortical suppression. One patient did experience postural hypotension prior to gingival surgery, but this is attributed to his antidepressant medication. We can conclude from this study that immunosuppressed organ transplant patients taking the maintenance dose of prednisolone (5-10 mg/day) do not require corticosteroid cover prior to gingival surgery under local anaesthesia. We would however, advocate monitoring of their blood pressure throughout the procedure.

The emergency drugs box--time for action?

Many GDPs are confused about which emergency drugs they should stock. There is a lack of uniform advice on this topic. Most recommended lists of emergency drugs contain superfluous medications which GDPs would never be expected to use. This paper rationalises the content of the emergency drugs box and provides clear, standardised guidance. A list of ten essential emergency drugs is presented, all of which can be administered by simple routes. Every GDP should be trained and competent to use these essential emergency drugs.

Prevalence of emergency events in British dental practice and emergency management skills of British dentists

Medical emergencies in dental practice are generally perceived as being rare but when an emergency does occur it can be life-threatening. The ability of the dentist to initiate primary management is the key to minimising morbidity and mortality. Accurate data on the prevalence of emergency events, required so that dentists can adequately prepare to deal with emergency situations, is sparse and obsolete. This study aimed to determine the current prevalence of medical emergencies and the perceived emergency management skills of dentists. A questionnaire, distributed to 887 dentists working in general dental practice across five counties of Northern England, produced a response rate of 34%. The most frequently reported emergency was vasovagal syncope (1.9 cases, per dentist per year), followed by hypoglycaemia (0.17), angina (0.17), epileptic fit (0.13), choking (0.09), asthma (0.06), hypertensive crisis (0.023) and anaphylaxis (0.013). Myocardial infarction and cardiac arrest were extremely rare with an incidence of 0.003 and 0.002 cases per dentist per year, respectively. The total prevalence of all emergency events (excluding syncope) was 0.7 cases per dentist per year. Only 20.8% of dentists felt competent to diagnose the cause of a collapse in the dental surgery. However the majority believed that they would be able to undertake initial treatment of most common emergencies. Despite this more than 50% felt unable to manage a myocardial infarction or anaphylaxis, and 49.7% did not know how to insert an oral airway or undertake an intravenous injection. Future postgraduate training in emergency care for dentists needs to be more accurately targeted to the known prevalence of emergencies and deficiencies in dentists' emergency skills.

In vitro synthesis and characterization of a cartilaginous meniscus grown from isolated temporomandibular chondroprogenitor cells

Internal derangement of the temporomandibularjoint can lead to perforation of the intra-articular meniscus and osteoarthritic degeneration. Current methods of repairing damaged menisci are limited by lack of biological compatibility of graft materials. This project aimed to synthesise and characterise a primate cartilaginous meniscus in vitro from harvested mandibular chondroprogenitor cells. Isolated cells from the mandibular cartilage of 12 young adult marmosets, aged 9-12 months, were grown in monolayer culture. After 21 days confluent colonies were resuspended and dispersed into a unpolymerised solution of type I collagen and fibrinogen. The resultant cell suspension was infiltrated into a resorbable type I collagen sponge carrier and allowed to polymerise. Aliquots of the cell-infiltrated sponge were maintained in organ culture for a further 14 days. Cultures were characterised using histochemical and immunocytochemical localisation of collagen and proteoglycan species. Two-thirds of cells in confluent 21-day monolayers expressed cartilage-specific type II collagen and chondroitin-4-sulphate. After 35 days organ cultures had formed a viable, organised, three-dimensional tissue mass consisting of mature chondrocytic cells interspersed in a dense cartilaginous matrix. The cartilaginous tissue generated in vitro may have potential application in the repair or replacement of damaged menisci in vivo.

Investigation of nitrous oxide pollution arising from inhalational sedation for the extraction of teeth in child patients

OBJECTIVES

(i) TO test whether the exposure of dental staff to nitrous oxide during inhalational sedation with nitrous oxide/oxygen for extractions in children complies with specified occupational exposure standards, and (ii) to assess the atmospheric nitrous oxide concentration at one site close to the breathing zone of the operator/sedationist and to determine which patient- and sedation-related factors affect the level of nitrous oxide pollution.

DESIGN

Prospective study.

SETTING

Dental hospital sedation department, Newcastle Dental Hospital, UK.

SAMPLE AND METHODS

20 inhalational sedation clinics each of 2 hours duration were evaluated, during which a total of 60 children aged 4-15 years had extractions carried out. Nitrous oxide was administered via a nose mask from a Quantiflex MDM inhalational sedation machine and active scavenging was used throughout. Exposure of dental staff was measured using personal dosimetry. Atmospheric nitrous oxide pollution at one fixed point, close to the breathing zone of the operator/sedationist, was assessed using infra-red gas analyser.

RESULTS

Mean exposure of the operator/sedationist to nitrous oxide during a single treatment clinic was 211 ppm, for the close support nurse 77 ppm and for the second nurse 67 ppm. Expressed as an 8 hour time-weighted average, the mean exposures were 39 ppm for the operator/sedationist, 17 ppm for the close support nurse and 15 ppm for the second nurse. The atmospheric nitrous oxide concentration varied during the clinics, with a maximum concentration of 538 ppm an a minimum that exceeded 100 ppm. There was a 71 minute delay following discharge of the last patient before atmospheric levels fell to zero. During sessions the degree of atmospheric pollution was inversely related to patient age (rc = -0.61, P < 0.05). There was a positive correlation between atmospheric pollution at the single point and the maximum percentage of nitrous oxide administered to each patient (rc = 0.57, P < 0.05).

CONCLUSIONS

In this study, staff exposure to nitrous oxide complied with the national occupational exposure standard but there was still considerable atmospheric nitrous oxide pollution during inhalational sedation for paediatric exodontia.

The role of mandibular condylar cartilage in articular cartilage repair

The articular hyaline cartilage of synovial joints has a very limited capacity for repair after injury. In contrast, the mandibular condylar cartilage of the temporomandibular joint possesses as intrinsic potential for regeneration. This study aimed to test the hypothesis that cultured allografts of mandibular condylar cartilage could be used to promote biological repair of injured orthotopic joint surfaces. Using a primate animal model, cultures of mandibular condylar cartilage cells were grafted into surgically created defects in a recipient hyaline cartilage joint surface. Articular wound healing was assessed macroscopically and histologically over a postoperative period of 52 weeks. Mandibular condylar cartilage cells scheduled for allogenous transplantation were initially characterised in vitro. Expansion of primary colonies in organ culture provided the allogenic cellular material for in vivo grafting. Grafting of osteochondral articular wounds with 5-week cultures of mandibular cartilage cells led to wound regeneration with complete reconstitution of articular surface continuity by 52 weeks. There was novel synthesis of cartilage collagens and sulphated glycosaminoglycans within the repair tissue and no evidence of immunological rejection. Healing of grafted defects was thought to occur by a combination of donor cell proliferation and ingress of host mesenchymal cells. In contrast, grafted control wounds underwent largely fibrous repair with incomplete articular regeneration. In conclusion, transplanted allografts of cultured mandibular condylar cartilage appeared to have the ability, in this primate model, to promote cartilaginous repair and regeneration of orthotopic articular wounds.

The effect of epidermal growth factor mouthwash on cytotoxic-induced oral ulceration. A phase I clinical trial

A double-blind clinical trial was performed to study the effect of epidermal growth factor (EGF) mouthwash on the healing and recurrence of oral ulceration in 12 patients undergoing cancer chemotherapy. The oral distribution or cytotoxic-induced ulcers corresponded to the salivary gutters. There was no difference in the rate of healing of established ulcers between the experimental and placebo groups. However, there was a small delay in the onset and severity of recurrent ulceration. It was concluded that EGF mouthwash does not accelerate ulcer healing, but it may have the potential to protect the oral epithelium from cytotoxic damage.

Facial airgun wound

A case is presented of a patient who received an airgun wound to the soft tissues of the right orbit. Because the pellet ricocheted off the bony orbital rim, it did not penetrate the globe and vision was not impaired. The increasing incidence of airgun wounds in Great Britain is also discussed.

Fatal sequel to dental implant surgery

The rare complication of fatal venous air embolism arising as a direct result of dental implant surgery in the mandible is depicted. The deaths arose from the erroneous use of an air/water coolant mixture with internally irrigated implant drills. The pathogenesis and consequence of air embolism is discussed. Practitioners are warned about the dangers of using air-driven equipment during implant surgery.

Repair of articular defects with autologous mandibular condylar cartilage

Unlike hyaline cartilage, mandibular condylar cartilage can respond to injury by complete healing. We have used the reparative potential of mandibular cartilage to promote repair of defects in a hyaline cartilage joint surface. In 12 adult marmosets, articular fibrocartilage from the mandibular condyles was transplanted into full-thickness defects created in the femoral condyles. Additional defects acted as an ungrafted control group. The grafted defects showed good incorporation of the transplant with restoration of the articular surface within six months. Repair was by proliferation of the fibrocartilaginous graft and chondrogenesis of hyaline cartilage. The repopulating cells were distributed in a matrix of maturing collagen and sulphated glycosaminoglycans. Ungrafted control defects were only partly repaired with fibrous tissue, leaving articular deficiencies. We conclude that transplanted mandibular fibrocartilage can promote reconstitution of wounded hyaline cartilage joint surfaces in primates.