GO TO CMA Home
GO TO Inside CMA
GO TO Advocacy and Communications
GO TO Member Services
GO TO Publications
GO TO Professional Development
GO TO Clinical Resources

GO TO What's New
GO TO Contact CMA
GO TO Web Site Search
GO TO Web Site Map



Canadian Journal of Rural Medicine
CJRM Winter 2001 / hiver 2001

Letters • Correspondance

CJRM 2001;6(1):54-6.

Intrathecal narcotics

To the editor:
I read with interest the article by Neil Leslie1 in the Fall issue of CJRM. Especially interesting are the comments under the "politics" heading, for politics seems to fly in the face of "evidence" (not to mention reasonableness).

A few years ago, Memorial University's CME Office hosted a provincial 2-day short course, "Anesthesia in Small Hospitals." GP anesthetists at the event presented statistics of several thousand anesthetics done in the cottage hospital system, with minimal morbidity and no mortality. The guest anesthetist at the conference, a professor of anesthesia at the university, dismissed the statistics outright as "insignificant" and advised that no anesthesia should be administered anywhere to anyone by any physician who wasn't a fully trained FRCP anesthetist. With attitudes so ingrained and long-standing as this, and those expressed in Dr. Leslie's article, one wonders if any true progress will be made in the provision of appropriate anesthesia services in rural Canada.

Paul Bonisteel, MD, CCFP, FCFP
New Harbour, Nfld.

Reference

  1. Leslie NG. Intrathecal narcotics for labour analgesia: the poor man's epidural. Can J Rural Med 2000;5(4):226-9.

To the editor:
Dr. Leslie's criticism1 of the Manitoba guidelines prohibiting the use of ITN (intrathecal narcotics) by anyone, other than those with anesthesia privileges, is appropriate enough. Those of us who do a lot of anesthesia sometimes fill in the long stretches by reading all of the horrific case reports in the literature: it leads to some rather fearful pronouncements about the use of anesthetic techniques and drugs outside our rarefied domain. That aside, reading Dr. Leslie's articles,1,2 as a GP anesthetist, left me with some concerns.

  1. The doses of intrathecal fentanyl and morphine that Dr. Leslie suggests are perhaps too high. A recent study3 showed that the ED95 value for fentanyl was 17.4 mcg and that doses of 25 mcg were associated with significantly more side effects, notably respiratory depression and pruritus. A dose of 15–20 mcg is perhaps more appropriate. Likewise, the recommended amount of intrathecal morphine seems to be getting smaller and smaller, the more it is studied. Most recently, it has been suggested that doses of 0.1 mg (100 mcg) are as effective as larger doses, but with far fewer side effects, at least in postsurgical pain control.4 Many physicians are now using 75–100 mcg of Epimorph when giving intrathecal morphine. It should perhaps also be emphasized just how small a dose this is. Even with the most dilute concentration of Epimorph (0.5 mg/mL), a tuberculin syringe is usually required for measuring.

  2. Postdural puncture headache is relatively uncommon, but it is a stretch to call this type of headache "mild." Spinals for cesarean section "went out of fashion" in the 60s and 70s, chiefly because of this very debilitating side effect. It is the use of the new needles that has made them more commonplace again. Having the capacity to do epidural autologous blood patch for these headaches when they occur is a nice, though perhaps not absolutely necessary, option.

  3. The future of intrapartum pain control may be less in epidurals and ITN than with patient-controlled analgesia (PCA). PCA fentanyl may offer equal safety and effectiveness to epidurals for the vast majority of patients. I recognize, however, that it is the prospect of avoiding the 2 am epidural that might motivate my enthusiasm for this modality. Nevertheless, we can hope to see more done to study this, especially in small-volume centres.

Gordon K. Jackson, MD, CCFP
39 Drummond St. W
Perth ON K7H 2J9
jackson@perth.igs.net

References

  1. Leslie NG. Intrathecal narcotics for labour analgesia: the poor man's epidural. Can J Rural Med 2000;5(4):226-9.
  2. Leslie NG. Intrathecal narcotic administration procedure. Can J Rural Med 2000;5(4):230-2.
  3. Herman NL, Choi KC, Affleck PJ, Calicott R, Brackin R, Singhal A, et al. Analgesia, pruritus, and ventilation exhibit a dose–response relationship in parturients receiving intrathecal fentanyl during labor. Anesth Analg 1999;89:378-83.
  4. Slappendel R, Weber EWG, Dirksen R, Gielen MJM, van Limbeek J. Optimization of the dose of intrathecal morphine in total hip surgery: a dose-finding study. Anesth Analg 1999;88:822-6.

Dr. Neil Leslie replies:
As referenced in my original article,1 the use of intrathecal narcotics (ITN) for labour analgesia has been shown to be safe and efficacious when done by family doctors not trained in anesthesia. The potential complications of ITN administration are well documented and were not more likely to be found in studies involving doctors with no anesthesia training than in those involving doctors with anesthesia training. Pronouncements prohibiting the technique for non-anesthetists are not supported by the literature. "Horrific case reports" pertaining to use of this technique by non-anesthetists did not appear in the literature when I researched this topic.

Anyone who uses this technique should be well versed in the management of its potential complications, but the literature supports my view that family doctors can safely perform this procedure without anesthetic training.

Dosing:

With regard to the dosing issue, I am grateful for Dr. Jackson's references.2,3 The trend for ITN dosage in labour analgesia and postoperative pain control has indeed been steadily downward.

Herman and colleagues' study,2 cited by Dr. Jackson, establishes efficacy at an ED95 for intrathecal fentanyl at 17.4 mcg. This was done by establishing a dose–response curve using doses of 5, 7.5, 10, 15, 20 and 25 mcg of fentanyl in 6 study groups. There was a dose-related increase in pruritus, and the end tidal carbon dioxide (ETCO2) went up in a statistically significant way from baseline values. The increase in ETCO2, while statistically significant, was small (i.e., approx. 4 mm Hg) and did not have clinical significance. The dose relation to pruritus and changes in ETCO2 were not linear in the study. The increase of ETCO2 from baseline was very similar at the 15-mcg dose to that at the 25-mcg dose, and the difference between these 2 doses was probably not statistically or clinically significant, although the differences in these 2 groups was not compared directly. Interestingly, the 20-mcg group had the highest incidence of puritis and the largest change in ETCO2. None of the patients in the study required treatment for respiratory depression, nor were any of them somnolent.

Palmer and coworkers,4 cited in my article, did a dose–response curve for intrathecal fentanyl as well, but they also looked at duration of action versus dose. They concluded that below 20–25 mcg the duration of action suffered significantly, but above 25 mcg there was an increase in side effects and that 25 mcg was the optimal dose to use in assuring efficacy and duration but in limiting untoward side effects. Edwards and colleagues5,6 used ITN fentanyl at 25 mcg with 0.25 mg of morphine without clinically significant respiratory depression, but less may have been as effective. Future studies will undoubtedly add to our understanding.

It would be difficult to extrapolate values for intrathecal morphine used in postoperative pain control (hip surgery) to relief of labour pain because the former is somatic pain and relatively steady, whereas labour has a large visceral pain component and has a relapsing and remitting nature. Moreover, patients in the former group are mostly elderly, and those in the latter group are decidedly younger.

In the studies cited in my original article, morphine was most commonly used at 0.25 mg. I did not come across any articles on a dose–response curve for ITN morphine. Some centres routinely gave naltrexone postpartum, or sometimes a half-hour after the ITN, to prevent respiratory depression. Others did not. In the studies limiting the morphine to 0.25 mg, clinically significant respiratory depression was not reported, with or without prophylactic naltrexone. Other studies or anecdotes reporting respiratory depression invariably used significantly higher doses, from 1.0 to 5.0 mg of ITN morphine.

Postspinal headache:

Although spinal anesthesia for cesarean sections "went out of fashion" in the 60s and 70s because of postspinal headache, it is again the standard because, with the use of the new pencil-tip 26-gauge (or smaller) needles, there is now a low incidence of postspinal headache. Most studies report an incidence of approximately 1%. When postspinal headache does occur following puncture with these new needles, it is not as severe as that seen with inadvertent dural puncture with a large-gauge needle (as used in epidural analgesia).

Most of the studies cited in my article managed these headaches with conservative measures, supine position for 24 hours, hydration and analgesia. An autologous blood patch is another method of managing the headache, but in my experience, this has not been required for the very few postspinal headaches I've seen with this technique.

Patient-controlled analgesia:

PCA (patient-controlled analgesia) is another option for managing pain associated with labour. Whether it offers equal safety or efficacy could only be known if it was studied in direct contrast to ITN or epidural analgesia. PCA fentanyl may, in fact, have its benefit in the fact that the anesthetist doesn't have to get out of bed at 2 am. However, I would hope that we choose our analgesic options on the basis of what is safe and effective for the patient in labour.

Certainly, ITN has been shown to be as safe and effective as epidural analgesia and does not require MDs trained in anesthesia to perform it. If the family doc without anesthesia skills can do this technique, then we can get good analgesia for women in labour and still see that the anesthetist gets a good night's sleep. ITN may also afford women effective labour analgesia in communities where there is not 24/7 anesthetic coverage.

Finally, Dr. Jackson suggests that we can hope for future studies of ITN use in small-volume centres. This is an excellent point. Further study would point out the advantages and pitfalls of ITN for these centres and would give a basis of evidence to help us defend or deny the technique. Studies done in Canadian rural practices are sadly lacking. A network of centres would give us the power in numbers to do a valid study on this technique. Perhaps we should advertise on the RuralMed network or at the SRPC meeting in Hockley Valley in April to see if we can get the necessary group set up.

Neil Leslie, MD, FCFP
Box 590
Revelstoke BC V0E 2S0
nleslie@revelstoke.net

References

  1. Leslie NG. Intrathecal narcotics for labour analgesia: the poor man's epidural. Can J Rural Med 2000;5(4):226-9.
  2. Herman NL, Choi KC, Affleck PJ, Calicott R, Brackin R, Singhal A, et al. Analgesia, pruritus, and ventilation exhibit a dose-response relationship in parturients receiving intrathecal fentanyl during labor. Anesth Analg 1999;89:378-83.
  3. Slappendel R, Weber EWG, Dirksen R, Gielen MJM, van Limbeek J. Optimization of the dose of intrathecal morphine in total hip surgery: a dose-finding study. Anesth Analg 1999;88:822-6.
  4. Palmer CM, Cook RC, Hays R, Van Maren G, Alues D. The dose–response relation of intrathecal fentanyl for labour analgesia. Anesthesiology 1998;88(2):355-61.
  5. Edwards RD, Hansel NK, Pruessner HT, Barton B. Intrathecal morphine as analgesia for labour pain. J Am Board Fam Pract 1988;1(4):245-50.
  6. Edwards RD, Hansel NK, Pruessner HT, Barton B. Intrathecal morphine sulfate for labour pain. Tex Med 1985;81(11):46-8.

© 2001 Society of Rural Physicians of Canada