I was intrigued to see Hung et al’s [1] paper on preventing fentanyl-induced cough, having read Ambesh et al.’s [2] report on the same topic last month. At the risk of appalling the rest of the specialty, I have to admit I had not even realised that fentanyl caused cough, and I find the incidence quoted (18-65%) astonishing; I doubt it reflects most anaesthetists’ experience.

My own practice (and I do not suppose it is unique) in most routine adult cases is to give 100 µg of fentanyl with 30 mg of propofol (containing 0.1% lidocaine) and then pre-oxygenate. When it becomes apparent that this is having an effect (typically after 30 s) I proceed with induction; I do not recall any patient ever coughing at this time. This technique was prompted by Anderson and Robb’s paper [3], which showed that using propofol as its own co-induction agent seemed to be as effective as using midazolam. I adopted this technique in response to complaints from nursing staff, that my day-surgery cases were excessively sleepy post-operatively, an outcome I ascribed to the midazolam, and which was duly resolved by changing to this technique.

The rationale of this technique is to reduce the total dose of propofol required, in order to minimise the resulting haemodynamic disturbance. However, it may also be that propofol fortuitously reduces fentanyl-induced coughing, a possibility suggested by Chin et al.’s prospective, randomised study [4]. This study suggested that ephedrine or lidocaine was efficacious in reducing fentanyl-induced coughing, but failed to show statistical significance with propofol. It is scientifically plausible that propofol would reduce fentanyl-induced coughing. Therefore, perhaps the combination of propofol and lidocaine is even better.

I remain perplexed that researchers see this as a problem, and wondered whether it was simply that they were using a higher dose of fentanyl compared to mine, but several of the papers these groups cite [5-8] used no more than 2 µg.kg^-1 and still report similar incidences.

A straw poll of a few colleagues found most of them were in agreement with me, and state that this is a theoretical problem only, with an exception perhaps being in children. It is interesting that the only two serious cases reported [9-10] were both paediatric cases, both of whom incidentally had doses of no more than 2 µg.kg^-1, both of whom had significant co-morbidity and both of whom could easily have had other reasons for their complications; i.e. there is no proven case in the literature of this phenomenon causing a serious outcome in adults.

In summary, in adults, standard doses of fentanyl do not cause a problem in the real world and I believe that devoting much more research effort to solving this 'problem' stands to achieve little.

D H Elcock
Royal Shrewsbury Hospital
Shropshire, UK
E-mail: david.elcock@sath.nhs.uk

No external funding or conflicts of interest declared

References

1. Hung KC, Chen CW, Lin VCH, Weng HC, Hsieh SW. The effect of pre-emptive use of minimal dose fentanyl on fentanyl-induced coughing. Anaesthesia 2010; 65: 4-7.
2. Ambesh SP, Singh N, Gupta D, Singh PK, Singh U. A huffing manoeuvre, immediately before induction of anaesthesia, prevents fentanyl-induced coughing: a prospective, randomized and controlled study. British Journal of Anaesthesia 2010; 104: 40-3.
3. Anderson L, Robb H. A comparison of midazolam co-induction with propofol pre-dosing  for induction of anaesthesia. Anaesthesia 2002; 53: 1117-20.
4. Chin SL,Wei ZS, Wei HC, Chen JL, Huei MY, Martin SM. Intravenous lidocaine and ephedrine, but not propofol, suppress fentanyl-induced cough. Canadian Journal of Anesthesia 2004; 51: 654-9.
5. Phua WT, The BT, Jong W, Lee TL, Tweed WA. Tussive effect of a fentanyl bolus. Canadian Journal of Anesthesia 1991; 38: 330-4.
6. Yeh CC,Wu CT, Huh BK, et al. Pre-medication with intravenous low-dose ketamine suppresses fentanyl-induced cough. Journal of Clinical Anesthesia 2007; 19: 53-6.
7. Lin JA,Yeh CC, Lee MS, Wu CT, Lin SL, Wong CS. Prolonged injection time and light smoking decrease the incidence of fentanyl-induced cough. Anesthesia & Analgesia 2005; 101: 670-4.
8. Horng HC, Wong CS, Hsiao KN, et al. Pre-medication with intravenous clonidine suppresses fentanyl-induced cough. Acta Anaesthesiologica Scandinavica 2007; 51: 862-5.
9. Tweed WA, Dakin D. Explosive coughing after bolus fentanyl injection. Anesthesia & Analgesia 2001; 92: 1442-3.
10. Ambesh SP, Singh N, Srivastava K. Fentanyl-induced coughing caused life-threatening airway obstruction in a patient with arteriovenous malformation of tongue and hypopharynx. Internet Journal of Anesthesiology 2009; 20: 1.

I am glad to read this letter because I strongly agree with Dr Elcock. When I read this article for the first time in January this year, I had exactly the same views as Dr Elcock, but I chose not to express myself as I thought that these views were because of my relative lack of experience as a ST5. I regretted that I did not know about this side about a drug that I administer every day to almost every patient. Thus, I examined a few references for the original article. It surprises me that there is a lot of discussion about this 'problem' in the literature which I have almost never witnessed. This whole discussion now definitely makes me a bit vigilant about this unwanted side effect of fentanyl.

Priti Gandre (ST5), Barts and The London School of Anaesthesia 

We were appreciative that Dr. Elcock shared his experience in daily clinical practice. Dr. Elcock concluded that the standard doses of fentanyl (100 ug) did not cause the cough responses with his technique in adult patients. In our institute, fentanyl 100-200 µg is often chose as the dose for tracheal intubation in order to minimize hemodynamic disturbance. Pentobarbital or propofol may be used as the induction agents according to the anaesthetist’s choice. The ideal dose of fentanyl during anesthetic induction varies according to the patient’s clinical conditions, the induction technique and surgery. As the dosage of fentanyl and induction agents administered may vary between anaesthetists, the technique used by Dr. Elcock may be limited.

When a severe cough is provoked by fentanyl in clinical practice, we believe that anaesthesia may be induced immediately by most anaesthetists. Therefore, the serious complications provoked by fentanyl-induced cough in adult patients may be rare in clinical practice. However, the unexpected cough response during anaesthetic induction may be an unpleasant experience for patients. For example, the cough response may increase the intensity of pain in patients with abdominal pain or distention during anaesthetic induction. Theoretically, the cough response is also undesirable in patients with increased intracranial pressure, abdominal pressure and intraorbital pressure.

We agreead partially with the opinion of Dr. Elcock that the fentanyl-induced cough is not a problem in most patients when a lower dose of fentanyl is administered. However, as a cough response may be provoked by fentanyl (100-200 µg) in our daily clinical practice, the problem can not be ignored.

Kuo-Chuan Hung. MD, Shao-Wei Hsieh. MD

I-DA Hospital

Kaohsiugh, Taiwan

E-mail: billwintw@yahoo.com.tw