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Correspondence  |   April 1999
Catheter Tip Position and Baricity of the Local Anesthetic Have an Impact on Maldistribution in Microcatheter CSA 
Author Notes
  • Department of Anesthesiology; Hopital Lapeyronie; Giraud; 34295 Montpellier Cedex 5; France
Article Information
Correspondence
Correspondence   |   April 1999
Catheter Tip Position and Baricity of the Local Anesthetic Have an Impact on Maldistribution in Microcatheter CSA 
Anesthesiology 4 1999, Vol.90, 1228-1229. doi:
Anesthesiology 4 1999, Vol.90, 1228-1229. doi:
In Reply:-Dr. Standl is right in highlighting the fact that several clinical studies have described techniques destined to decrease the incidence of caudally directed spinal catheters. However, it is important to note that these studies were performed when the role of the catheter's sacral direction in the occurrence of maldistribution was but an experimental hypothesis. [1,2] The point of our work was to objectively identify the clinical causes of maldistribution. Using 19-gauge, end-holed catheters, the study showed that the caudal orientation of the catheter tip is a factor of maldistribution rather than the caudal direction of the catheter. As such, the sacral flow of local anesthetics seems to be the most important factor of maldistribution; a cranially directed catheter can have a distally oriented catheter tip if a loop is created during catheter insertion, leading to a distal flow of local anesthetics.
Second, the role of injection speed, lower when local anesthetics are administered via microcatheters and experimentally evoked as being associated with the maldistribution of hyperbaric solutions, [1] has already been debated in the literature. [3-5] According to Wendell and Cianci [3] and Erian, [4] neither the catheter diameter nor the baricity of the injected solution was a factor of maldistribution. However, once again, these results were derived from experimental models. Using 19-gauge catheters, we demonstrated that maldistribution did not occur more often with either isobaric or hyperbaric bupivacaine. Nevertheless, the comparison has not been clinically studied using microcatheters. As such, I find it difficult to advise against the use of hyperbaric solutions via microcatheters before clinical evaluation. In one study, although retrospective, the required doses of hyperbaric lidocaine, 5%, administered via microcatheters were not greater than those using macrocatheters. [6] Finally, Horlocker et al. reported, also in a retrospective study, that the incidence of inadequate anesthesia was no greater when using microcatheters rather than macrocatheters. [7] As such, in light of these experimental [3,4] and clinical results, [6,7] we cannot conclude that microcatheters and hyperbaric solutions are factors of maldistribution. The only current, clinically demonstrated factor of maldistribution is the caudal orientation of the catheter tip. [8] 
It is important to note, however, as highlighted in our manuscript, that the danger of maldistribution does not lie in its occurrence but rather in its not being diagnosed, leading to the administration of high doses of potentially neurotoxic local anesthetics. The diagnosis and early management of maldistribution, as well as abandoning the administration of high doses of local anesthetics (lidocaine, 5%), should limit the occurrence of cauda equina syndrome after continuous spinal anesthesia.
Philippe Biboulet, M.D.
Department of Anesthesiology; Hopital Lapeyronie; Giraud; 34295 Montpellier Cedex 5; France
(Accepted for publication November 23, 1998.)
REFERENCES
Rigler ML, Drasner K: Distribution of catheter injected local anesthetic in a model of the subarachnoid space. Anesthesiology 1991; 75:684-92
Lambert DH, Hurley RJ: Cauda equina syndrome and continuous spinal anesthesia. Anesth Analg 1991; 72:817-9
Wendell, A, Cianci JP: I factors affecting distribution of catheter-injected local anesthetic (letter). Anesthesiology 1992; 77:211-2
Erian RF: II factors affecting distribution of catheter-injected local anesthetic (letter). Anesthesiology 1992; 77:212
Drasner K, Rigler ML: III factors affecting distribution of catheter-injected local anesthetic (letter). Anesthesiology 1992; 77:213
Bevacqua MD, Slucky AV, Cleary WF: Spinal catheter size and hyperbaric lidocaine dosing. Reg Anesth 1994; 19:136-41
Horlocker TT, McGregor DG, Matsushige DK, Chantigian RC, Schroeder DR, Besse JA, the Perioperative Outcomes Group: Neurologic complications of 603 consecutive continuous spinal anesthetics using macrocatheter and microcatheter techniques. Anesth Analg 1997; 84:1063-70
Biboulet Ph, Capdevila X, Aubas P, Rubenovitch J, Deschodt J, d'Athis F: Causes and prediction of maldistribution during continuous spinal anesthesia with isobaric or hyperbaric bupivacaine. Anesthesiology 1998; 88:1487-94