Effectiveness and safety of dentist-led conscious sedation using fentanyl with midazolam in dentistry: a five-year retrospective service evaluation

Fentanyl and midazolam have a synergistic effect, where the combination of drugs results in an enhanced clinical sedative effect, greater anxiety relief and better intraoperative conditions, compared to when either drug is used on its own.6 This combination of drug regimen has been widely used to sedate patients undergoing various medical and surgical procedures, most commonly for gastroendoscopy, intubation in anaesthesiology/emergency medicine, spinal surgery and oral surgery.

This concomitant technique is recommended by the IACSD guidance for patients when midazolam alone does not produce adequate anxiolysis. The administration of fentanyl does not negate the use of sufficient local anaesthesia. It may, however, facilitate better cooperation with unpleasant sensations, such as pressure during extractions, and improve compliance with accepting local anaesthetic, as well as providing some post-operative pain relief.

This service evaluation revealed that 94.5% of patients who had failed sedation with benzodiazepine proceeded to have dental treatment completed successfully using fentanyl and midazolam sedation. The result of a 25.4% reduction in midazolam dose required following fentanyl administration is in agreement with Moore7 and Lobb8 studies, which demonstrated a statistically significant reduction in the amount of midazolam needed (36% and 29%, respectively) to titrate to a suitable endpoint for dental treatment using the fentanyl-first approach.7

There is evidence that opioid-first administration yields a substantial reduction in the amount of additional sedative needed to achieve similar degrees of moderate sedation, which was observed in this evaluation.7,9 The fentanyl-first approach is reported to reduce the clearance and prolong the duration of action of midazolam, likely as a result of competitive inhibition of CYP3A (cytochrome P4503A) activity.10 This could increase clinical treatment time but may require longer post-operative monitoring by an escort. Compared to single-drug techniques, there is increased unpredictability and a reduced margin of safety, potentially increasing the risk of adverse events.4 Although the risks of apnoea, chest wall rigidity and vocal cord closure11,12 associated with rapid administration of high doses of fentanyl is low in the dental setting due to the small doses used, the risk of respiratory depression associated with concomitant use of fentanyl with central nervous system depressants, such as benzodiazepines, is higher.13,14 The incidence of respiratory depression in this evaluation (8.2%) was slightly higher than Saiso's study,15 which reported six incidents of desaturation (5.6%); however, in the latter, patients received supplemental oxygen at 3 L/min immediately after establishment of intravenous access throughout the procedure, which could mask the incidence of respiratory depression. Furthermore, desaturation requiring intervention was defined as oxygen saturation of below 95%, which is higher than the standard 90% level in our service. Figures from studies focused on medical procedures using fentanyl and midazolam sedation show mortality rates of 1:2000 for upper gastrointestinal endoscopy and 1:1500 for colonoscopy,16 but the small data set in our evaluation limits any evaluation of the safety profile of combining fentanyl with midazolam for sedation in dentistry.

The incidence of vomiting with this technique is about 30% according to Craig and Boyle,17 hence fasting before sedation and antiemetics may be considered, though this was not seen in our service evaluation. If a decision is made to prescribe fentanyl with benzodiazepine, the lowest effective dose should be used, the duration of treatment should be as short as possible, and the patient's vital signs should be monitored closely throughout and after sedation.

There is also the risk of administrating the wrong drug during multi-drug sedation. To mitigate this, midazolam and fentanyl should be kept in separate trays away from each other with the syringes clearly labelled. Fentanyl is usually drawn up in a 1 ml syringe due to the small quantity required and midazolam in a 5 ml syringe (one way of distinguishing between the two drugs). The vial of the drug should also be crosschecked with a second person before drawing up to ensure the drugs are drawn up as intended and in-date. There was no reported complication of over-sedation or wrong drug administration in this evaluation.

The retrospective data collection relied on the record-keeping diligence of clinicians and missing/improbable data could not be followed-up. Most of the missing documentation in the excluded sample were of Ellis grade and midazolam dose without fentanyl - the reason being that previous unsuccessful midazolam-only sedation was carried out elsewhere and our service had no access to that information. Patients' self-reported outcome measures, such as patient satisfaction, anxiety and pain, were not investigated as part of this retrospective evaluation, hence it was not possible to compare patient perspectives of this technique compared to the midazolam-only technique. Patients were not considered the statistical unit of analysis, so the possible clustering effect for repeated sedation episodes of the same patients was not considered.

As the majority of patients in the sample were of ASA I and II (91.7%), the patient demographic within the evaluation could be representative of the primary dental care patient population in general. Older and medically complex patients (ASA III and above) should be approached with caution in a specialist centre and this group is rarely considered for multi-drug sedation within our service.

Regulation

Fentanyl-midazolam conscious sedation is considered an advanced technique. The IACSD guidance states that this opioid-midazolam combination is 'suitable for the operator-sedationist working in a primary care setting on condition that the dentist and second appropriate person have successfully completed recognised training programmes, have an appropriate level of experience, and that only ASA grade I and II adults (over 16 years of age) are treated'.4 In Wales, the Service standards for conscious sedation in a dental care setting18 advises that multi-drug techniques including the use of fentanyl should take place only within an acute or dental teaching hospital setting.

Recent NHS commissioning guide released in January 2023 states that primary care dental sedation services commissioned by the NHS only, are now advised to refer patients to a secondary care setting for advanced sedation techniques.19

Dentists, sedationists and nurses involved in the administration of this technique require additional theory and a minimum of 20 supervised cases to demonstrate competency for independent safe practice. This would be an extended competency developed by sedation practitioners who are trained and experienced in carrying out single-drug sedation using midazolam (documented experience of at least 100 cases over last two years).20

Similar to basic sedation techniques, team members involved in fentanyl and midazolam sedation must be trained in intermediate life support. Due to the mutual potentiation between opioids and benzodiazepines, the sedation team must be fully equipped to manage deep sedation and associated risks (respiratory depression/apnoea, airway obstruction, vomiting and prolonged recovery). Airway assessment is crucial to pre-empt ease of managing airway complications during sedation and availability of personnel with 'deployable' airway competencies (including basic airway manoeuvres, the use of airway adjuncts and the ability to administer positive pressure ventilation) is mandatory according to the IACSD and Resuscitation Council UK. Capnography may be useful in multi-drug sedation due to the increased risk of hypoxaemia and apnoea. Detection of early deterioration is especially important to help monitor respiratory status in patients with complex medical needs. When fentanyl is used, the reversal agent naloxone must be readily accessible, but for this multi-drug sedation technique, flumazenil should be used in the first instance to reverse the cardiorespiratory depressant effect of midazolam.

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