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Three Part Question

In [patients undergoing procedural sedation] does the use of [supplemental oxygen] reduce the [incidence of hypoxaemia without masking respiratory depression]?

Clinical Scenario

A 55 year old man has presented to the emergency department with a dislocated shoulder. As you prepare to sedate him the nurse puts on 5LO2 via a face mask. You know that the advantage of supplemental oxygen is that it permits a longer period of normal oxygenation in the event of apnoea or respiratory depression. However oxygen may also negate pulse oximetry as an early warning device and respiratory depression. You wonder if supplemental oxygen can limit the incidence or severity of hypoxia without masking the presence of underlying respiratory depression.

Search Strategy

OVID interface on the world wide web. 1966 – July 2000.
Exp sedation OR exp procedural sedation OR conscious sedation$ ti.ab.sh.rw] AND [oxygen$ t.ab.rw.sh] LIMIT to human and english language

Search Outcome

Altogether 1924 papers were found of which 2 were directly relevant to the three part question, a further 3 were indirectly relevant.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Deitch et al. 2007 USA	80 emergency department patients over the age of 2 undergoing procedural sedation with midazolam and fentanyl.	Blinded RCT	Hypoxia (defined as sats below 90%)	6 patients in the supplemental O2 group and 5 in the room air group experienced sats below 90%. (p=0.97)	Small study size, small number of patients with hypoxia. 12 patients under 18 but only 2 younger than 12, although they were included the study was not able to comment on the paediatric population.
			Respiratory Depression (1 or more criteria; sats <90%, ECTO2>50mmHg, absolute change in ETCO2 >10mmHg from baseline or loss of ETCO2 trace.	20 patients in the supplemental oxygen group and 19 patients in the room air group met the criteria for resp depression
			Physician recognition of hypoxia, as defined by a clinical observer.	Physicians recognised hypoxia in 8 out of the 11 patients who desaturated but in 0 of the patients who met the ETCO2 criteria alone.
Deitch et al. 2008 USA	110 emergency department patients over the age of 18 undergoing procedural sedation with propofol. Blinded to either receive supplemental oxygen at 3L/min or compressed air.	Double blind RCT	Hypoxia defined as sats <93%	10 patients in the supplemental oxygen group and 15 patients in the compressed air group (p=0.30)	Small study size, small numbers of patients with hypoxia.
			Respiratory Depression (1 or more criteria; sats <90%, ECTO2>50mmHg, absolute change in ETCO2 >10mmHg from baseline or loss of ETCO2 trace.	20 patients in the supplemental oxygen and 7 patients in the compressed air group met ETCO2 criteria for respiratory depression.
			Physician recognition of hypoxia as defined by a clinical observer	Physicians identified respiratory depression in 23 of the 25 patients who became hypoxic compared with only 1 of the 27 patients who met ETCO2 criteria for respiratory depression.
Miner et al 2002 USA	74 adult patients undergoing procedural sedation in the emergency department.	Prospective observation study	Hypoxia defined as sats <90%	5 of 47 patients (10.6%) receiving supplemental oxygen experienced hypoxia compared with 6 of 27 patients (22%) breathing in room air	The study was designed to look at the use of end tidal CO2 not the incidence of hypoxia within the patient population given supplemental oxygen or those on room air.
Miner et al 2003 USA	108 adult patients undergoing procedural sedation	Prospective observational study	Hypoxia, defined as sats<90%	Hypoxia was observed in 13 of 87 patients (14.9%) receiving supplemental oxygen compared with only 1 of 21 patients (4.8%) breathing room air	The study was designed look at the use of bispectral electroenchalography in procedural sedation within the emergency department not to compare the incidence of hypoxia for the patient populations receiving supplemental oxygen and those on room air.
Miner et al. 2003 USA	103 adult emergency department patients undergoing procedural sedation for fracture reduction or dislocation. The patients were randomised to receive either propofol or methohexital.	Randomised control trial	Hypoxia, defined as sats<90%	Hypoxia was noted in 5 of 59 patients (8.5%) receiving supplemental oxygen and 6 of 44 patients (13.6%) breathing room air.	Although the study was a randomised control trial the randomisation was to see if there was a difference between propofol and methohexital, whether the patients received supplemental oxygen or not was not controlled.

Comment(s)

There have been very few studies that directly address whether supplemental oxygen can limit the incidence or severity of hypoxia without masking the presence of underlying respiratory depression. The only two relevant papers did not find that supplemental oxygen results in a statistically significant reduction in the incidence of hypoxia. Both these papers also report that physicians were much better at recognising hypoxia (i.e. noticing a desaturation from observing pulse oximetry) than they were in recognising respiratory depression that occurred with normal pulse oximetry. As so few patients were recognised to have respiratory depression (only 1 throughout both studies), the authors were unable to comment on the affect of supplemental oxygen had on this pick up rate. The studies completed by Miner and colleagues were not designed to specifically look at the effects of supplemental oxygen but are included here as they published their results on the incidence of hypoxia in patients with and without it, it is however difficult to draw conclusions from these papers as confounding variables were not controlled.

Clinical Bottom Line

There is some suggestion that supplemental oxygen makes no difference to the incidence of hypoxia in patients undergoing procedural sedation. However as there are only two studies designed to answer this question, both of small numbers, until further evidence is presented it is best to use local departmental guidance. Of interest was the almost universal failure to recognise respiratory depression that was picked up by end tidal CO2 monitoring, perhaps a more relevant question is whether end tidal CO2 monitoring should become routine practice in procedural sedation within the emergency department.

References

1. Deitch et al. The utility of supplemental oxygen during emergency department procedural sedation and analgesia with midazolam and fentanyl: a randomized, controlled trial. . Annals of Emergency Medicine. 2007 Jan;49(1):31-6.
2. Deitch et al The utility of supplemental oxygen during emergency department procedural sedation with propofol: A randomized controlled trial. Annals of Emergency Medicine July 2008. Vol 52. No 1. 1-8
3. Miner et al. End Tidal carbon dioxide monitoring during procedural sedation Acad Emerg Med 2002;9:275-280
4. Miner et al. Bispectal electroencephalographic analysis of patients undergoing procedural sedation in the emergency department. Acad Emerg Med 2003;10:638-643
5. Miner et al. Randomized clinical trial of propofol versus methohexital for procedural sedation during fracture and dislocation reduction in the emergency department. Acad Emerg Med 2003;10:931-937