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Underdosing the Epidural Invalidates a Good Clinical Trial

Andreae, Michael M.D.

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To the Editor:—
The randomized clinical trial by Norris et al. 1 comparing the outcome of alternate combinations of intraoperative anesthesia and postoperative analgesia doesn't support previous evidence 2,3,4 and meta-anlysis 5 that documented lower mortality, morbidity, less pain, and better outcomes of combined or pure regional anesthesia techniques with postoperative local anesthetic infusions.
It might hence be widely quoted as the crown witness of regional inefficacy; in our opinion inappropriately so, because inadequate doses, regimen, and concentrations of local anesthetics were used. Indeed, the authors concede this inadequacy. Short of blocking the activation of the hippocampus-pituitary axis and the sympathetic stimulation associated with surgical trauma and insufficient to treat and respond to postoperative pain, we cannot expect an outcome benefit from the addition of a regional technique.
However, with adequate intraoperative concentrations of local anesthetics, we find a third percent of bupivicaine necessary to achieve surgical blockade, the authors might have encountered (and feared) challenging episodes of hypotension secondary to low systemic vascular resistance and attenuation of the thoracic cardiac accelerators during periods of decreased preload from blood loss, third spacing, and vasodilation. Intraoperative use of epidural anesthesia to achieve surgical blockade may therefor not convey the desired outcome benefits for this particular surgical procedure.
When used for postoperative pain control for aortic aneurysm repair however, epidurals will yield outcome benefits, 6 provided that (1) adequate concentrations are used (we recommend the equivalent of an eighth percent of bupivicaine or more), (2) the infusions rates areadjusted swiftly, with boluses where needed, to respond to interpatient variability and changing antinociceptive needs.
We suggest furthermore that a convincing study should document effective treatment, in this case regional anesthesia intraoperatively, either by achieving adequate surgical blockade before induction or afterwards by, for example, pupillometry. 7 In summary, while the work by Norris et al. 8 was flawless in many ways, 9 we feel it lacks validity due to shortcomings of the (regional anesthesia) protocol in several arms of the study.
Michael Andreae, M.D.
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1. Norris EJ, Beatie C, Perler B: Double-masked Randomized Trial Comparing Alernate Combinations of Intraperative Anesthesia and Postoperative Analgesia in Abdominal Aortic Surgery. A nesthesiology 2001; 95: 1054–67

2. Gottschalk A, Smith DS, Jobes DR: Preemptive Epidural Aalgesia and Recovery from Radical Prostatectomy. JAMA 1998; 279 (14): 1076–82

3. Yeager MP, Glass DD, Neff RK: Epidural Anesthesia and Analgesia in High-risk Surgical Patients. A nesthesiology 1987; 66 (6): 729–736

4. Wattwil M, Toren T, Hennerdal S, Garvill JE: Epidural Analgesia with Bupivicaine Reduces Postoperative Paralytic Ileus after Hysterectomy. Anesth Analg 2001 1989; 68: 353–8

5. Rodgers A, Walker N, Schug S: Reduction of Postoperative Mortality and Morbidity with Epidural or Spinal Anesthesia: Results from Overview of Randomised Trials. BMJ 2000; 321: 1–12

6. Beattie WS, Badner NH, Choi P: Epidural Analgesia reduces Postoperative Myocardial Infarction. Anesth Analg 2001; 93 (4): 853-8

7. Larson M, Sessler DI, Ozaki M, McGuire J, Schroeder M: Pupillary assessment of sensory block level during combined epidural/general anesthesia. A nesthesiology 1993Jul; 79 (1): 42–8

8. Norris EJ, Beatie C, Perler B: Double-masked Randomized Trial Comparing Alernate Combinations of Intraperative Anesthesia and Postoperative Analgesia in Abdominal Aortic Surgery. A nesthesiology 2001; 95: 1054–67

9. Todd M: Clinical Research Mauscripts in Anesthesiology. A nesthesiology 2001; 95: 1051–3

Cited By:

This article has been cited 1 time(s).

British Journal of Anaesthesia
Does epidural analgesia improve surgical outcome?
Ballantyne, JC
British Journal of Anaesthesia, 92(1): 4-6.
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