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Transient Neurologic Symptoms After Spinal Anesthesia

Hampl, Karl F. MD; Schneider, Markus C. MD; Ummenhofer, Wolfgang MD; Drewe, Jurgen MD

Regional Anesthesia and Pain Management
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We recently reported several cases consistent with transient radicular irritation after spinal anesthesia with hyperbaric 5% lidocaine.The present prospective, blind, nonrandomized study was performed to determine the incidence of these transient neurologic symptoms and to identify factors that might be associated with their occurrence. We studied 270 patients scheduled for gynecologic or obstetric procedures under spinal anesthesia. For spinal anesthesia, either 5% lidocaine in 7.5% glucose or 0.5% bupivacaine in 8.5% glucose was used. Patients were evaluated on postoperative day 3 by a quality assurance nurse who was unaware of the drug given or details of the anesthetic technique. Transient neurologic symptoms were observed in 37% of patients receiving 5% lidocaine, whereas only one patient receiving 0.5% bupivacaine had transient hypesthesia of the lateral aspect of the right foot. These results suggest that symptoms were the result of a specific drug effect. However, because of the limitations of the study one cannot conclude that lidocaine per se was the cause.

(Anesth Analg 1995;81:1148-53)

Department of Anesthesia, University of Basel/Kantonsspital, Basel, Switzerland.

Section Editor: Denise J. Wedel.

Presented in part at the Annual Meeting of the American Society of Anesthesiologists, Washington, DC, October 8-14, 1993.

Accepted for publication May 31, 1995.

Address correspondence to Karl F. Hampl, MD, Department of Anesthesia, San Francisco General Hospital, Room 3C-38, 1001 Potrero, San Francisco, CA 94110.

We recently described four cases of apparent transient radicular irritation presenting as lower extremity dysesthesias in patients given 5% lidocaine in 7.5% dextrose for single-injection spinal anesthesia [1]. Subsequently, another seven cases were reported in which similar neurologic symptoms were associated with the use of 5% lidocaine [2,3]. To determine the incidence of such sequelae we performed a prospective, blind, clinical study.

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Methods

With institutional approval of the University Hospital of Basel and written, informed consent, we studied 270 patients scheduled for elective gynecologic or obstetric surgery under spinal anesthesia. Patients with a history of chronic or recurrent back pain or prior neurologic abnormality were excluded from the study.

The patients were informed about the purpose of the study by the attending anesthesiologist at the preoperative visit and by information contained on the written, informed consent form. The patients were informed that they would get a "routine spinal anesthetic" using a well established and appropriate local anesthetic (LA) for their procedure and that we would investigate the incidence of various side effects of spinal anesthesia. A list of possible symptoms was given to the patients, including headache, nausea, backache, hearing loss, or difficulty in urinating or defecating. To avoid patient bias, no information regarding the type of LA or its duration of action nor any details concerning the lidocaine controversy were given to the patients.

Three anesthesiologists who were aware of reports of transient neurologic symptoms associated with lidocaine were involved in the intraoperative management.

Patients were premedicated with midazolam, 7.5 mg orally, 1 h before surgery. After cannulation of a peripheral vein and starting routine monitoring, lactated Ringer's solution 15 mL/kg was infused. The patients were positioned in the left or right decubitus position (at the discretion of the attending anesthesiologist) and 1.5 mL of lidocaine 1% was injected for local anesthesia of the skin and the subcutaneous tissue using a 27-gauge needle. According to the policy in our department, a 22- or 25-gauge Quincke needle (Terumo Corp., Tokyo, Japan) was used for patients 60 yr of age or more, whereas for younger patients a 25-gauge Whitacre type needle (Polymedic, Bondy, France) or a 24-gauge Sprotte needle (Pajunk; Geisingen, Germany) was used according to the preference of the attending anesthesiologist. Subarachnoid puncture was performed at the L3-4 interspace using a midline approach. If the attending anesthesiologist judged this approach to be difficult, an alternative approach was used according to his preference. Once correct needle position was identified by free flow of cerebrospinal fluid, approximately 0.25 mL of cerebrospinal fluid was aspirated and the LA was then injected.

The choice of LA was not randomized but selected according to an expected duration of surgery: patients undergoing procedures with an expected duration of 60 min or less received 5% lidocaine in 7.5% glucose (approximately 1 mg/kg); the remaining patients received bupivacaine in 8.5% glucose (approximately 0.2 mg/kg). Details of the anesthetic procedure (level and approach of spinal injection, type of needle used), and problems related to the anesthetic technique (multiple attempts to puncture the subarachnoid space, bleeding through the needle, or paresthesias) were recorded. The extent of anesthesia was assessed by pinprick at intervals of 5 min for 20 min. Maximum height of block was noted.

Mean arterial pressure (MAP) was recorded using an automated blood pressure device or, in selected patients scheduled for major abdominal surgery, an indwelling arterial catheter. Blood pressure was recorded every minute for 15 min after subarachnoid injection of LA or induction of general anesthesia, and every 3 min thereafter until the patient was transferred from the postanesthetic care unit to the ward. Minimal MAP during the perioperative period was noted and the maximum decrease in MAP from the preinduction value calculated. In order to assess complete recovery from neuraxial blockade, the patients were seen during the evening of the day of surgery by the anesthesiologist in charge of the anesthetic procedure.

All patients were evaluated on postoperative Day 3 by one of two quality assurance nurses. In order to ensure standardized data collection, a symptom checklist was used, which contained both related and unrelated questions Table 6. This was done either on the ward or by telephone if the patient had been discharged from the hospital. Transient neurologic symptoms were defined as pain and/or dysesthesia in the buttocks, thighs, or lower limbs occurring after recovery from the anesthetic. All patients who reported neurologic symptoms were referred to one of three blinded anesthesiologists. This anesthesiologist again evaluated the patient using a standardized checklist Table 7, performed a gross neurologic evaluation Table 7 (Appendix 2), and was responsible for the followup until symptoms resolved.

Table 6

Table 6

Table 7

Table 7

Both the quality assurance nurses and the anesthesiologists involved in the postoperative evaluation were unaware of the drugs given or the details of the anesthetic technique. Although the quality assurance nurses were instructed about the possibility of transient neurologic symptoms after spinal anesthesia, they were not aware of an association with lidocaine.

A chi squared test was used for statistical comparison of the incidences of transient neurologic symptoms and problems related to the anesthetic technique, the number of surgeries performed in the lithotomy position, and the approaches and types of needles used for subarachnoid puncture. Patient demographic data, dose of the LA, duration of surgery, and maximum decline of MAP were compared using analysis of variance. A P value of less than 0.05 was considered significant.

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Results

Demographic data did not differ significantly between treatment groups Table 1. Complete recovery from the anesthetic was documented in all patients by the evening of surgery. The incidences and duration of transient neurologic symptoms and pain (at the site of injection) are shown in Table 2. Transient neurologic symptoms occurred in 44 patients (37%) receiving 5% lidocaine. In 34 of these 44 patients (77%), symptoms persisted less than 3 days. To exclude other etiologies, the remaining 10 patients were evaluated by a neurologic consultant.

Table 1

Table 1

Table 2

Table 2

The distribution of symptoms in patients receiving 5% lidocaine is shown in Figure 1; in 98% of the cases, the symptoms were bilateral. None of the patients had sensory-motor deficits, bowel or bladder dysfunction, or abnormal muscle-tendon reflexes. Only one patient receiving 0.5% bupivacaine had transient neurologic symptoms--hypesthesia of the lateral aspect of the right foot.

Figure 1

Figure 1

The relevant aspects of the surgical and anesthetic procedures are provided in Table 3 and Table 4. Mean duration of surgery was significantly shorter in patients receiving lidocaine (16 min) than in those receiving bupivacaine (53 min). All patients receiving lidocaine underwent surgery in the lithotomy position, whereas only 62% of patients receiving bupivacaine were placed in this position. There were no significant differences between groups in the incidence of technical problems during subarachnoid puncture Table 3. There were no differences between groups in terms of the type of needles used or the level or approach for spinal puncture Table 4. Similarly, extension of block and maximal perioperative decline in MAP did not differ between groups Table 3. In patients receiving lidocaine, characteristics of the surgical and anesthetic procedures did not differ between patients with or without neurologic symptoms Table 5.

Table 3

Table 3

Table 4

Table 4

Table 5

Table 5

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Discussion

Lidocaine has been used for more than 40 yr for spinal anesthesia and has a remarkable safety record [4-6]. Although there has been several recent reports of severe neurologic sequelae after the use of 5% lidocaine for continuous spinal anesthesia [7-9], all were associated with the administration of a dose greater than that normally used for single-injection spinal anesthesia. The results of the present study suggest that the administration of a single subarachnoid injection of 5% lidocaine may be associated with less severe, but far more common, neurologic complications.

In the present study, we found a 37% incidence of transient neurologic symptoms after a subarachnoid injection of 5% lidocaine, whereas only one patient receiving 0.5% bupivacaine had transient numbness and hypesthesia along the lateral aspect of the right foot without dysesthesias or motor dysfunction Table 2. In this patient, symptoms occurred after surgery for vaginal hysterectomy lasting more than 200 min during which the patient's legs were held in lithotomy position by ankle straps. The consultant neurologist thought that this complication likely resulted from patient positioning.

One explanation for the high incidence of neurologic symptoms being previously unrecognized may be the transient nature of this complication. In fact, we became aware of this problem only after instituting a departmental quality assurance program that includes patient followup by specialized nurses. Of note, in 1985, Flaatten and Raeder [10] reported a similar incidence of symptoms in patients undergoing vasectomy under spinal anesthesia: 15 of 51 patients (29.4%) complained of backache radiating to a lower extremity; in 48 of the 51 cases, 5% lidocaine was administered and, in the remaining three patients, tetracaine was used. Unfortunately, the authors do not indicate whether any of the 15 patients with radiating pain had received tetracaine.

In the present study, neurologic symptoms occurred only in patients who had received 5% lidocaine, except for one patient (described above) given bupivacaine. That this phenomenon was a specific effect is suggested by the similar incidence among groups in reported pain at the site of injection Table 2. The incidences of technical problems, bleeding, and paresthesia were similar in both anesthetic groups Table 3, suggesting that direct trauma to the spinal nerves cannot explain the difference in the incidence of symptoms. Furthermore, nerves of the cauda equina are free-lying and thus rarely damaged by needles. Although nerve roots may be damaged in the intervertebral foramens where they are relatively fixed [11], such injury would occur as a result of lateral placement of the needle and would not be expected to cause bilateral symptoms.

Spinal cord ischemia seems an unlikely etiology, since reductions in MAP were unremarkable and did not differ among groups Table 3. Duration of surgery or patient positioning also do not appear to explain the difference in incidence of neurologic symptoms because complications are more likely to occur with longer procedures, and similar complaints were not observed in bupivacaine-treated patients operated in lithotomy position. The equivalence of block extension in all groups suggests that anesthetic distribution was not an important factor Table 3. Other causes of neural injury, such as infection or subarachnoid or epidural hemorrhage, are extremely unlikely given the rarity of these serious complications, the absence of associated symptoms in the present study, and the benign clinical course.

Although our patients developed symptoms suggestive of radicular origin, the complete absence of sensory-motor deficits or muscle-tendon reflex abnormalities precludes the conclusion that symptoms are due to acute radicular irritation. Acute low back pain or pain radiating to the buttocks or legs may also be the consequence of acute or chronic disease affecting a motion segment of the lumbosacral spine (referred pain) [12]. Injections of 11% saline into the intervertebral disks or the facet joints of the lumbosacral spine have been shown to produce not only local pain but, in some cases, pain radiating to the extremities similar to nerve root irritation. Yet, injections into other structures of the motion segment tended to produce only localized back pain [13]. However, referred pain as a result of a facet syndrome or other conditions affecting the motion segments tend to be chronic or to recur [14]. As patients with a history of backache were excluded from our study, chronic diseases of the lumbovertebral spine or systemic disorders causing radicular type symptoms seem unlikely to be etiologies or to have contributed to these symptoms [12,15].

Our study has several limitations. First, the study was not randomized and the anesthetic technique, surgical procedure, and intraoperative management varied. Therefore, methodologic bias cannot be ruled out. Second, the anesthesiologist in charge of the anesthetic procedure was not blinded. However, both the patient and the investigator were unaware of the details of the anesthetic procedure or the LA administered. Thus, although this is not a doubleblind study in the usual sense, an investigator's bias is unlikely to have affected our results. Third, we used only a single formulation of lidocaine, a 5% solution containing glucose, and administered a relatively uniform dose. Fourth, based on relative potency, lidocaine was administered at a higher dose than bupivacaine, and the glucose content and the tonicity of the LA solutions differed [16]. Therefore, although we found a difference in the incidence of transient neurologic symptoms with the solutions of lidocaine and bupivacaine administered in the present study, the role of the anesthetic concentration and dose, the tonicity of the solution, the presence of glucose, and, finally, the anesthetic drug per se, remain to be defined. Available data from animal studies suggest that local anesthetic neurotoxicity is, at least in part, concentration-dependent [17-21] and that the neurotoxic potential of lidocaine might exceed that of bupivacaine [17,18,22]. In contrast, experimental data suggest that 7.5% glucose does not contribute to neurotoxicity of 5% lidocaine [18,23]. Randomized studies are warranted to further define the etiology of transient neurologic symptoms and the factors that affect its occurrence.

The authors thank Dr. Kenneth Drasner for many helpful discussions and Joan Etlinger for excellent editorial advice.

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