Article Text

Is propofol a safe and effective sedative for relocating hip prostheses?
  1. N Mathieu,
  2. L Jones,
  3. A Harris,
  4. A Hudson,
  5. C McLauchlan,
  6. P Riou,
  7. G Lloyd
  1. Emergency Department, Royal Devon and Exeter Hospital, Exeter, UK
  1. Dr G Lloyd, Emergency Department, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter EX2 5DW, UK; gavin.lloyd{at}rdeft.nhs.uk

Abstract

Objective: To explore the safety and efficacy of propofol as a sedative for the relocation of hip prostheses in the emergency department.

Methods: A prospective observational study was performed in 100 patients aged 37–93 years who received sedation with propofol in the emergency department for hip prosthetic relocation. All patients received intravenous titrated morphine prior to radiography, followed by a 1 mg/kg bolus of propofol after adequate preoxygenation. At 60 s, joint relocation was attempted by an independent physician. Data for each patient were recorded, with particular attention given to adverse outcomes.

Results: Two patients were excluded because of protocol violation. The use of propofol achieved hip relocation in 94 of the remaining 98 patients (96%). The four unsuccessful cases required general anaesthesia with muscle relaxation. Eight patients experienced a fall in oxygen saturation, four responding to airway repositioning and four requiring brief supplemental ventilation. Four patients became hypotensive and required titrated intravenous boluses of a vasopressor (metaraminol) to restore normal blood pressure. 42 patients required additional doses of propofol, 36 for inadequate sedation and 6 for prolonged reduction attempts.

Conclusions: Significant adverse effects of propofol in this case series were uncommon (12/98 patients) and readily countered. This case series suggests that propofol is a safe and effective sedative for relocating hip prostheses.

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Patients who are brought to an emergency department (ED) with a dislocated prosthetic hip are likely to be anxious and in pain. Furthermore, they require a painful procedure to relocate their hip and may wait a mean of 7–11 h for relocation under theatre-based general anaesthesia in the UK.1 2 In contrast, early relocation in the ED promptly relieves the discomfort and periprosthetic tissue distortion. It is our assumption that it is in the patient’s interest to attempt relocation in a safe and timely manner.

Propofol (2,6 di-isopropylphenol) is an ultrashort-acting non-opioid sedative-hypnotic agent and is commonly used for procedural sedation in emergency medicine in Australasia and North America.3 Its published use in UK emergency practice is limited.4

Currently, procedural sedation in UK emergency medicine employs an opiate/benzodiazepine combination.5 Problems associated with this practice include occasional prolonged sedation due to the long half-life of midazolam. In addition, there is the need for ongoing monitoring and observation, or else consideration of reversal agents. A previous study from Poole, UK by Frymann et al reported a relocation rate of 62% when using morphine/midazolam combinations for dislocated hip prostheses.2

We propose that propofol allows an improved success rate in hip relocation, obviating the need for a rescue general anaesthetic. Our key objective in this study was to explore the safety and efficacy of propofol for the relocation of hip prostheses in an ED setting.

METHODS

This prospective observational study was carried out in the ED of the Royal Devon and Exeter Hospital between November 2005 and October 2007. Consecutive adult patients with an isolated unilateral prosthetic hip dislocation were included. All received intravenous titrated morphine prior to radiography according to their verbal pain score. This was not part of the protocol. The fasting status of the patient was considered in each case; the guidelines of the American College of Anaesthesiologists on fasting requirements for elective surgery (adopted by the Royal College of Anaesthetists) were used as a guide and not a rule.6 7 All procedures followed the departmental protocol (see online Appendix 1). A full airway assessment was performed before sedation. Patients were continuously monitored with pulse oximetry, respiratory rate (with a transthoracic impedence trace) and ECG as well as non-invasive blood pressure measurements every 5 min.

Each sedation was performed by an emergency physician (middle grade and above) who had previously completed an in-house consultant-delivered training package. This included a paper-based tutorial and a 1-hour session with simulated scenarios, with particular attention being given to management of adverse outcomes (hypoxia and hypotension) and inadequate sedation. Propofol sedation was only performed between 08.00 and 23.00 h when a duty ED consultant was available for supervision.

All patients received a 1 mg/kg bolus of propofol after 3 min of preoxygenation with a fraction of inspired oxygen (Fio2) as close to 1 as possible. This was provided via a bag valve mask attached to high-flow oxygen and was continued until each patient was able to demonstrate adequate ventilatory effort after relocation. Hip relocation was attempted at 60 s by an independent physician using recognised techniques. The doctor performing the manipulation was either an emergency physician or a member of the duty orthopaedic team. Additional 0.5 mg/kg boluses of propofol were administered if the patient was inadequately sedated or if a more prolonged sedation attempt was needed. A maximum dose of 2 mg/kg was administered. All procedures were recorded initially on a dedicated data collection form and, from January 2006, on the department’s newly created electronic sedation database. Specific complications were sought: airway compromise, vomiting, desaturation (<92%), need for bag valve mask ventilation and hypotension (<90 systolic BP).

RESULTS

One hundred patients were recruited, two of whom were excluded due to protocol violation. The mean age of the patients was 73 years (range 37–93). There were equal numbers of male and female patients. Of the remaining 98 patients, 8 experienced a fall in oxygen saturation; 4 responded to repositioning of the airway and 4 required brief supplemental ventilation. Four patients became hypotensive and required titrated intravenous boluses of a vasopressor (metaraminol) to restore normal blood pressure. All recovered uneventfully. Forty-two patients required additional doses of propofol; 36 were not adequately sedated and 6 needed a more prolonged reduction attempt.

Of the 98 patients, 94 (96%) had a successful reduction. The four unsuccessful cases required general anaesthesia with muscle relaxation as inpatients. One of the unsuccessful attempts was unknowingly performed on a “constrained component” prosthesis which is irreducible unless an “open” procedure is performed.

The two protocol violations took the form of changes to the initial bolus dose used (0.5 mg/kg and 0.75 mg/kg). Both cases needed additional boluses of propofol to achieve the required level of sedation; both had uneventful successful outcomes.

DISCUSSION

This case series suggests that propofol is a safe and effective sedative for relocating hip prostheses. We acknowledge that most of our patients were anaesthetised rather than sedated according to the UK definition.8 Indeed, apnoea was an expected side effect, hence the emphasis we gave to airway assessment and proficient preoxygenation. Significant side effects were encountered in 12 patients, each readily countered by the trained ED staff.

While the efficacy of propofol appears superior to morphine/midazolam combinations (96% vs 62% reported in the Poole study), we acknowledge that this is likely to be due to a higher sedation target end point used in the latter. Deeper levels of sedation are clearly achievable with midazolam, although the drug lacks the ultrashort duration typically afforded by propofol.

One-third of our patients were inadequately sedated following an initial bolus of 1 mg/kg. We are at present unable to identify these patients beforehand, and remain comfortable with the need for supplemental boluses rather than risk increasing the frequency of adverse outcomes with a higher initial bolus.

Limitations of the study

We considered a randomised controlled trial comparing sedative strategies, calculating a priori 134 patients in each arm in order to detect a 20% difference with a power of 80% and α of 0.05. This was felt to be impractical in an ED of our size, requiring a 5-year recruitment period by our estimation.

Our study is further limited by adjustments to the protocol over time. In our efforts to enhance the safety of the procedure, particularly given the age, co-morbidities and frequent antihypertensive medication use of this patient population, we have more recently advocated preloading selected patients with 500 ml saline. We also recognised that some patients became apnoeic before 60 s and subsequently advocated attempted reduction as soon as the transthoracic impedence trace suggested apnoea. We were guilty of not making these changes in protocol evolution explicit to our staff. As a result, the number of patients receiving saline preloading is unclear from our records, as are those who had a reduction attempt less than 60 s after the propofol bolus. We recognise these as weaknesses of this prospective study.

CONCLUSION

This case series suggests that propofol is a safe and effective sedative for relocating hip prostheses. With the use of a protocol, a designated education programme and ongoing clinical vigilance, we found few significant adverse effects, all readily countered. Furthermore, propofol compares favourably with the current UK standard of benzodiazepine/opiate combinations (96% vs 62%) since it allows ultrashort deep sedation/anaesthesia. Its excellent efficacy allows early reduction in patient discomfort and obviates the need for a prolonged wait for general anaesthesia in theatre.

REFERENCES

Supplementary materials

Footnotes

  • Appendix 1 is published online only at http://emj.bmj.com/content/vol26/issue1

  • Competing interests: None.

  • Ethics approval: Formal ethical review by an NHS research ethics committee was waivered by the regional ethics committee.

  • Contributions from authors: All authors either delivered or supervised the procedures. LJ and GL provided the in-house training; NM and GL wrote the paper; GL initiated the case series and acts as guarantor.

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