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* From the Department of Anesthesia, Foothills Hospital, University of Calgary, Calgary; and
the Department of Anesthesiology and Pain Medicine, University of Alberta Hospitals, Edmonton, Alberta, Canada.
Address correspondence to: Dr. Ban C. H. Tsui, Department of Anesthesiology and Pain Medicine, University of Alberta Hospitals, 8-120 Clinical Sciences Building, Edmonton, Alberta T6G 2G3, Canada. Phone 780-407-8861; Fax: 780-407-3200; E-mail: btsui{at}ualberta.ca
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Abstract |
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Clinical features: A 70-yr-old male was scheduled for a right total hip arthroplasty. He agreed to a PCB for postoperative analgesia and a spinal anesthetic. The spinal anesthetic was performed after completion of the PCB. Free flow of clear fluid was demonstrated at the beginning and at the end of the presumed intrathecal injection. General anesthesia had to be induced because of failure of the spinal anesthetic. The patient awoke from his general anesthetic with a functional PCB and no evidence of residual neuraxial anesthesia. The possibility of epidural spread of local anesthetic from the PCB impairing the ability to perform spinal anesthesia is discussed and reviewed. We hypothesize that local anesthetic in the epidural space may have falsely reassured the anesthesiologist that the needle was properly placed.
Conclusion: We describe a case of failed spinal anesthesia following a PCB and discuss its implications.
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Introduction |
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The traditional end-point for confirmation of proper placement of a needle during the performance of a spinal anesthetic is free flow of clear fluid from the needle hub. In normal circumstances, when this endpoint is obtained it is unusual for spinal anesthesia to fail.2 However, assuming that the clear fluid that flows from a needle tip is CSF may lead to failure of spinal anesthesia.5 We report a case of failed spinal anesthesia following a psoas compartment block (PCB) and hypothesize that local anesthetic in the epidural space may have falsely reassured the anesthesiologist that the needle was properly placed.
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Case report |
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The PCB was performed first. Surface landmarks described by Capdevila et al. were used to guide needle placement.6 The skin was cleaned with 2% chlorhexidine and a sterile plastic drape was applied to the back. A 100-mm Stimuplex needle (Stimuplex; Braun, Melsungen, Germany) was attached to a Braun nerve stimulator (Stimuplex; Braun: 100 µsec pulse width, 2 Hz) and the output set to 2 mA. Both an assistant and the patient were asked to report the occurrence of any movement (or sensation) to the anesthesiologist immediately. The needle was advanced until bone was contacted, this was assumed to be the transverse process of L4–5. The needle was then moved caudally off the transverse process and advanced until a motor response was obtained. Approximately 2 cm beyond the bone the final end-point obtained was a quadriceps motor response at a minimal current of 0.25 mA. The patient felt no paresthesia. After a negative aspiration test, 20 mL of 0.75% bupivacaine with 1:200,000 epinephrine were injected in 1 to 5 mL aliquots. No blood or fluid of any nature was aspirated throughout the injection.
Immediately after the PCB was completed, a spinal anesthetic was performed. Tuffier’s line was used to estimate the needle entry point.7 A 25-gauge Whitacre spinal needle was advanced in the midline at the L3–4 interspace. No distinct loss of resistance was experienced. When the needle had been advanced about 70 mm the stylet was removed and clear fluid immediately flowed from the needle hub. A syringe with 12.5 mg 0.5 % isobaric bupivacaine, 5 µg sufentanil, and 200 µg morphine (total volume 2.5 mL) was attached to the Whitacre needle. Approximately 1 mL of clear fluid was easily aspirated from the needle via the syringe. Unexpected resistance was met when the injection was initiated. Therefore, aspiration was attempted again. Clear fluid was again easily aspirated from the needle. Subsequently, the drug mixture was injected slowly over approximately 30 sec. The patient did not complain of paresthesia or discomfort. The patient was then turned supine and prepared for surgery.
After approximately 25 min, it was clear that the spinal anesthetic had failed. The patient had a dense sensory block to pin prick and a motor block in the distribution of the right lumbar plexus only. There was a marked differential conduction block outside the territory of the right lumbar plexus on both sides extending from about T10–L5 (diminished sensation to pin prick but unaltered sensation to touch and pressure) with a patchy bilateral motor block. The block was felt to be insufficient for the surgery to proceed. The situation was discussed with the patient after which general anesthesia was induced with propofol 200 mg. Muscle relaxation was provided with rocuronium 50 mg. Anesthesia was maintained with desflurane end-tidal concentrations of 5 to 6% in air and oxygen. Cefazolin 1 g was given iv. The surgery proceeded uneventfully. Residual muscle paralysis was reversed at the end of the case with neostigmine (4 mg) and glycopyrrolate (0.4 mg) and the patient’s trachea was extubated when he was awake and following instructions.
The patient was reassessed in the recovery room about 3.5 hr after the initial blocks were performed. A dense right PCB was present but there was no evidence of conduction blockade anywhere else. He required 6 mg of iv morphine in the recovery room for postoperative pain control.
The patient was transferred to the general surgical ward. He experienced no nausea or pruritus. He used 24 mg of morphine over the ensuing 48 hr via an iv patient-controlled analgesia device (Lifecare® 4100 PCA Plus Infusor; Abbott Laboratories, North Chicago, IL, USA). The iv patient-controlled analgesia machine was discontinued on the second postoperative day and he was started on oral analgesia (oxycodone SR 10 mg po bid). He experienced no headache postoperatively. He was ambulating the day after surgery and discharged home on the fifth postoperative day. Follow-up three months later did not reveal any sequelae from his anesthetic or surgery.
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Discussion |
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The traditional end-point for needle placement when performing spinal anesthesia is return of clear fluid into and from the needle hub. It is assumed that the fluid returning is CSF. In some instances failure of anesthesia has occurred despite the return of clear fluid from the spinal needle.5 The explanation that has been offered is that the fluid was not CSF but other fluid in the epidural space or sc tissue.
The incidence of epidural spread with unilateral and/or bilateral anesthesia after posterior lumbar plexus block varies from 1.8 to 16%.9 However, the extent and contributing factors of epidural spread after lumbar plexus block are variable and undefined.10 Since the paravertebral space is contiguous with the epidural space, it is possible for local anesthetic to spread centrally from the paravertebral space to the epidural space depending on the position and direction of the injecting needle.9–12 In the case described, the central spread of local anesthetic after the performance of the PCB may explain the events experienced by the patient (Figure
). We speculate that the clear fluid obtained with removal of the stylet was likely local anesthetic, not CSF. This speculation is supported by the fact the patient experienced an initial, bilateral, markedly segmental and restricted, differential conduction block that dissipated before the patient awoke from general anesthesia. Other explanations regarding the identity and origin of the solution are possible (i.e., from the sc tissue or a subarachnoid cyst),8 however, they seem extremely unlikely. Thus, this case reminds anesthesiologists to be aware of this rare but potentially easily misdiagnosed end-point from the effect of performing two regional blocks in proximity.
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In this unusual set of circumstances, aspiration mislead the practitioner. The combination of a lack of a distinct loss of resistance with needle advancement and unusual resistance to injection following aspiration of fluid should prompt anesthesiologists to consider the possibility that the needle is improperly placed.
The presence or absence of CSF may be reliably confirmed by using a bedside assessment of glucose or protein content of aspirated fluid.20 The absence of a positive test for glucose or protein suggests the fluid is not CSF.20 Alternatively, a modification of the Tsui test may be used to facilitate correct spinal needle placement by providing objective information, in addition to the return of CSF via the needle.21 In previous studies, a different dose-response relationship has been shown in electrical stimulation for the epidural and the intrathecal space.22–24 When it is not clear that returning fluid is CSF, confirmation of placement may be obtained by passing an electrical current through an insulated spinal needle.19,25 The obvious limitation of this technique is the need for an insulated needle. Finally, as suggested by this case report, unexpected resistance upon the initiation of injection should prompt the anesthesiologist to consider that the needle may be misplaced.
This case supports, potentially, previous reports of epidural spread from PCB. In addition, it reminds anesthesiologists to keep this clinical scenario in mind as the extent and causes of epidural spread resulting in bilateral symmetrical or unilateral anesthesia after lumbar plexus block are still undefined. Finally, the importance of weighing the risks and benefits of performing two regional blocks in one area and the importance of considering changing patient conditions due to previous procedures performed on the patient are highlighted in this case.
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Acknowledgments |
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Footnotes |
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Accepted for publication April 26, 2004. Revision accepted September 10, 2004.
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2 Levy JH, Islas JA, Ghia JN, Turnbull C. A retrospective study of the incidence and causes of failed spinal anesthetics in a university hospital. Anesth Analg 1985; 64: 705–10.
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6 Capdevila X, Macaire P, Dadure C, et al. Continuous psoas compartment block for postoperative analgesia after total hip arthroplasty: new landmarks, technical guidelines, and clinical evaluation. Anesth Analg 2002; 94: 1606–13.
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20 el-Behesy BA, James D, Koh KF, Hirsch N, Yentis SM. Distinguishing cerebrospinal fluid from saline used to identify the extradural space. Br J Anaesth 1996; 77: 784–5.
21 Tsui BC, Wagner A, Finucane B. The threshold current in the intrathecal space to elicit motor response is lower and does not overlap that in the epidural space: a porcine model. Can J Anesth 2004; 51: 690–5.
22 Tsui BC, Gupta S, Finucane B. Detection of subarachnoid and intravascular epidural catheter placement. Can J Anesth 1999; 46: 675–8.
23 Tsui BC, Gupta S, Emery D, Finucane B. Detection of subdural placement of epidural catheter using nerve stimulation. Can J Anesth 2000; 47: 471–3.
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25 Tsui BC, Gupta S, Finucane B. Loss of resistance to saline -- does the dripping bother you? (Letter). Can J Anesth 1999; 46: 615–6.[Medline]
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