Anesth Analg 2005;100:296-297
© 2005 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000145314.57012.2A
LETTERS TO THE EDITOR
Reversal of an Unintentional Spinal Anesthetic by Cerebrospinal Lavage
Baljit Singh, MD,
Chhavi Papneja, DA, DNB, and
Vishnu Datt, DA, DNB
Department of Anaesthesiology and Intensive Care, G. B. Pant Hospital, New Delhi, India, dr_baljit@yahoo.com
To the Editor:
The report by Tsui et al. (1) was very interesting, but it raises more questions than it attempts to answer. It is difficult to understand why the authors used 5 mL instead of 3 mL of 2% lidocaine with epinephrine, which is the universally accepted test dose and the criteria for this is well known (2). The authors have neither mentioned the baricity of the drug nor the position of the patient immediately after administering the block. Both are important in a situation where the epidural is complicated by subarachnoid block. It is also not known whether the needle was turned in the epidural space to direct the bevel cephalad before inserting the catheter. Hardy et al. (3) have demonstrated that it is impossible to puncture the intact post mortem dura with a Portex catheter. The opening in the dura, therefore, was possibly caused by the needle tip, and turning the needle in epidural space may have contributed by prying open the dural fibers.
Tsui et al. (1) have opined that the catheter may have been in the sacral position. This cannot be denied if the needle tip were facing caudally, but it would not be logical to believe that the catheter would turn around caudally when the bevel is facing cephalad.
It has recently been shown that the subdural space is not a virtual space like the interpleural space. The dura-arachnoid interface is filled with neurothelial cells and some amorphous substance. This interface can be torn apart by the mechanical force of air or fluid injection, thereby creating the so-called subdural space (4). While investigating cases of failed epidural, Collier (5) demonstrated that the catheter in some of the cases was lodged in the subdural space and the contrast medium produced a localized, sausage-shaped shadow in the posterior subdural space. This shows that the drug remains localized possibly due to distension of the arachnoid mater, the weaker of the two membranes forming the dura-arachnoid interface.
In our opinion, the catheter was initially lodged in the subdural space and failure of epidural was due to localized pooling of the drug. However, as the bolus dose was followed by continuous infusion under pressure, breach occurred in the distended arachnoid mater and the drug was gradually discharged into the subarachnoid space leading to total spinal. It is well recognized that the fall in blood pressure in case of subdural block is gradual. The "stable blood pressure" of 80–90/30–40 mm Hg favors the gradual fall managed by infusion of fluids. It would have been appropriate, however, to know the preoperative baseline value, total volume infused and the expected loss in the intraoperative period.
It is well documented that the incidence of neurologic complications is higher in anesthetized patients where the spinal cord may be injured without evoking any complaint of paresthesia from the patient (6). It is quite convenient to insert a needle in the patient’s back who neither moves nor complains, but we fully agree with Horlocker and Caplan (7) that a catastrophic result, although not frequent, hardly justifies this convenience.
It surprises us to note that even after knowing that the dura and arachnoid have been breached leading to total spinal, the authors persisted with morphine patient-controlled epidural analgesia for postoperative pain relief when the patient complained of pain on waking up after the lavage. We admire the authors’ strong faith in epidural analgesia, but, in this case, it was nothing short of inviting the accident to happen again. They may have been confident of dealing with it, just in case, but we feel the wiser option is to stay out of trouble than to come out of it.
References
- Tsui BCH, Malherbe S, Koller J, Aronyk K. Reversal of an unintentional spinal anesthetic by cerebrospinal lavage. Anesth Analg 2004; 98: 434–6.[Abstract/Free Full Text]
- Moore DC, Batra MS. The components of an effective test dose prior to epidural block. Anesthesiology 1981; 55: 693–6.[Web of Science][Medline]
- Hardy PAJ. Can epidural catheters penetrate dura mater: an anatomical study. Anaesthesia 1986; 41: 1146–7.[Web of Science][Medline]
- Reina MA, Casasola ODL, Lopez A, et al. The origin of the spinal subdural space: ultrastructure findings. Anesth Analg 2002; 94: 991–5.[Abstract/Free Full Text]
- Collier CB. Accidental subdural injection during attempted lumbar epidural block may present as a failed or inadequate block: radiographic evidence. Reg Anesth Pain Med 2004; 29: 45–51.[Web of Science][Medline]
- Bromage PR, Benumof JL. Paraplegia following intracord injection during attempted epidural anesthesia under general anesthesia. Reg Anesth Pain Med 1998; 23: 104–7.[Web of Science][Medline]
- Horlocker TT, Caplan RA. Should regional block be performed in anesthetized patients? ASA News 2001; 65: 5–6.
Response
Ban C. H. Tsui, MD, FRCP(C), and
Stephen Malherbe, MB, ChB, Med FCA(SA)
Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, Alberta, Canada, btsui@ualberta.ca
In Response:
We appreciate the interest shown by Drs. Singh and Chhavi in our case report and thank them for pointing out the ambiguity in the report.
We agree that the test dose of 5 mL 2% lidocaine was excessive and that this was certainly more than the universally accepted test dose of 3 mL. The attending anesthesiologist had planned to use the same concentration of lidocaine for loading the epidural and had therefore decided to administer a 5-mL test dose instead of the usual 3 mL. This is a larger volume than normally administered as a test dose in our institution, and we agree that 3 mL is a more suitable volume for this purpose.
In a recent response to a Letter to the Editor by Dr. Schricker (1), we had addressed that a typographical error was made in the case report regarding the postoperative pain management. This patient’s epidural-intrathecal catheter was removed after the cerebrospinal lavage. The article should have read, "Subsequent postoperative pain was managed with IV morphine patient-controlled analgesia," rather than "Subsequent postoperative pain was managed with morphine patient-controlled epidural analgesia." To clarify, the patient’s postoperative pain was controlled with IV PCA morphine (bolus 1.2 mg, lock-out 8 min, concentration 2 mg/mL). We thank Drs. Schricker, Singh, and Chhavi for their attentiveness to detail and apologize for any confusion this error may have caused the readers.
Although we failed to mention the position of the patient or the baricity of the drug after administering the block, we did mention that the epidural was inserted after induction of anesthesia, implying that the patient was in the lateral position. We used isobaric local anesthetic. However, since hyperbaric solutions are not commonly used in epidural solutions, we did not believe it was necessary to address the baricity of the local anesthetic.
We disagree that an epidural needle tip facing cephalad in the epidural space cannot result in a catheter turning caudally. In our institution, we often use radiographs to verify the catheter location after epidural placement and have found that numerous catheters "turn" in a caudate direction. Other published studies (2,3) of lumbar epidural catheters inserted through needle bevels oriented cephalad or caudad suggest that the path and ultimate location of the catheter tip in the epidural space are unpredictable. In fact, Van Gessel et al. (4) demonstrated that a catheter could behave in a similar unpredictable way if inserted in the subarachnoid space, despite the bevel of the needle facing cephalad.
We agree that a possible explanation could be that the catheter was initially lodged in the subdural space. This was addressed in our discussion as, "subarachnoid placement, as a result of migration of the tip of the epidural catheter during initial insertion or during the course of epidural analgesia." This is, however, extremely difficult to detect using traditional methods but can be identified through diagnostic imaging or electrical stimulation (5). Nevertheless, we wish to reemphasize that the objective of this case report was to focus on the possible benefit of cerebrospinal lavage to reverse a total spinal anesthetic and not to speculate on the possible mechanisms of the total spinal.
Finally, we would like to point out that it is common and standard practice to place epidurals in anesthetized pediatric patients. We strongly disagree with the unfounded statements, "It is well documented that the incidence of neurologic complications are higher in anesthetized patients where the spinal cord may be injured without evoking any complaint of paresthesia from the patient..." We do not dispute the obvious fact that paresthesia cannot be elicited when performing neuroaxial blocks in anesthetized patients. However, there is absolutely no clear evidence that the risk of performing epidurals in anesthetized patients is higher than in awake patients, particularly in the pediatric population. Singh and Chhavi’s main argument was based on a case report written by Bromage et al. (6) that has been subsequently strongly disputed by a group of world-renowned pediatric anesthesiologists (7). While we believe that regional anesthesia is safest when performed in awake cooperative patients and we would, as a rule, always prefer to perform these blocks in this manner, it is our opinion, along with most pediatric anesthesiologists, that this is hardly an option or safe practice in uncooperative pediatric patients (7,8).
References
- Schricker T, Tsui BCH. Postoperative intrathecal morphine for analgesia after major orthopedic surgery [letter]? Anesth Analg 2004; 99: 306.[Free Full Text]
- Richardson MG, Wissler RN. The effects of needle bevel orientation during epidural catheter insertion in laboring parturients. Anesth Analg 1999; 88: 352–6.[Abstract/Free Full Text]
- Blanco D, Llamazares J, Rincon R, et al. Thoracic epidural anesthesia via the lumbar approach in infants and children. Anesthesiology 1996; 84: 1312–6.[Web of Science][Medline]
- Van Gessel EF, Forster A, Gamulin Z. Continuous spinal anesthesia: where do spinal catheters go? Anesth Analg 1993; 76: 1004–7.[Abstract/Free Full Text]
- Tsui BC, Gupta S, Emery D, Finucane B. Detection of subdural placement of epidural catheter using nerve stimulation. Can J Anaesth 2000; 47: 471–3.[Web of Science][Medline]
- Bromage PR, Benumof JL. Paraplegia following intracord injection during attempted epidural anesthesia under general anesthesia. Reg Anesth Pain Med 1998; 23: 104–7.
- Krane EJ, Dalens BJ, Murat I, Murrell D. The safety of epidurals placed during general anesthesia. Reg Anesth Pain Med 1998; 23: 433–438.[Web of Science][Medline]
- Suresh S. Thoracic epidural catheter placement in children: are we there yet? Reg Anesth Pain Med 2004; 29: 83–5.[Medline]
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