Abstract SNACC-46

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A Protocol for Reducing the Risk of Remifentanil-Associated Apnea in Spontaneously Breathing Patients

Mueller R, Papworth D, Todd M
University of Iowa College of Medicine, Iowa City, IA, USA

Background:
In a closed claims analysis of monitored anesthesia care (MAC), > 40% of claims were for death or permanent brain damage. Of these, 21% were due to respiratory depression.1 Remifentanil, although short-acting, may cause sudden apnea.2,3 The incidence of apnea or hypoxia due to remifentanil use in MAC is 3-10%.4-7 At our institution, a hypoxic cardiac arrest due to remifentanil occurred; a retrospective review of the records of all patients receiving the drug during MAC or flexible fiberoptic-aided intubations revealed an incidence of apnea of 3.6% (6/168) over a year. We then developed a protocol for the safer use of remifentanil in MAC.

Methods:
These factors contributed to apnea with remifentanil:
1. A solution of concentrated drug (50 µg/ml); a bolus of small volume could cause apnea.
2. A distal injection port in the IV so that remifentanil accumulated unrecognized in the iv tubing.
3. Excessively high dosage unadjusted for ASA status & age
4. Misuse as a sedative (not analgesic.)
5. Synergy with other respiratory depressants.
6. Failure to recognize hypoventilation early.

Key points of the protocol we mandated:

1. Use of a dilute remifentanil (4 µg/ml) solution.
2. Maximum dose of 0.05 µg/kg/min with other respiratory depressants.
3. Infusion pumps were default programmed with an upper limit of 0.1 µg /kg/min and an alert at 0.05 µg /kg/min.
4. An intravenous line (IV) without a bolus port, dedicated to the remifentanil strongly recommended.
5. If only one IV, use a carrier infusion and small IV dead-space distal to remifentanil infusion site permitting an inadvertent bolus of maximum 4 µg.
6. Turn off when painful stimuli ends.
7. Naloxone available.
8. Supplemental oxygen if fire risk is absent.
9. Nasal capnography (and pulse oximetry).
10. Stop remifentanil immediately for respiratory rate at or below 8.


Outcome and conclusion:

Since implementation of this protocol 6 months ago, there has been 1 instance of apnea (1/53 or 1.9 %) during remifentanil use during MAC in a 93 year old patient. A 4 µg /ml concentration was used with the highest dose of 0.05 µg/kg/min. The dose-for-age of the patient likely contributed to the apnea. Our audit continues.

With our protocol, there may be a reduced incidence of apnea or hypoxia with remifentanil. The most important aspect is the use of a dilute drug concentration, infused proximal to the patient with a carrier. This eliminates our previous latent vulnerability that facilitated unrecognized boluses of concentrated drug.

In summary, we describe key features of a protocol for the safer use of remifentanil as an analgesic during MAC or a cough suppressant during bronchoscopy.


References:

1. Bhananker SM et al Anesthesiology 2006; 104:228

2. LaPierre CD et al Anesth Analg 2011; 113:490

3. Krejcie TC et al Anesth Analg 2011; 113:441

4. Berkenstadt H, et al J Neurosurg Anesth 2001; 13:246

5. Moerman AT et al Eur J Anaesth 2003; 20:461

6. Mandel JE et al Anesth Analg 2008;106:434

7. Ryu JH et al Br J Anaesth 2012; 108:503


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