So, what is the answer that is clear to you now?
Actually let's ask: What was the question that you were searching for an answer for?
The original question was whether or not the concentration or dose of lidocaine had an effect in the incidence of TNS. That was the question, this is the answer that Mil alluded to originally.
Prospective study on incidence and functional impact of transient neurologic symptoms associated with 1% versus 5% hyperbaric lidocaine in short urologic procedures.
Tong D, Wong J, Chung F, Friedlander M, Bremang J, Mezei G, Streiner D.
Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto, Ontario, Canada.
BACKGROUND: The objectives of this study were to compare the incidence, onset, duration and pain scores of transient neurologic symptoms (TNS) with 1% versus 5% hyperbaric lidocaine in spinal anesthesia for short urological procedures in a large prospective study. This study would also evaluate patient satisfaction, and impact of TNS on functional recovery to assess the clinical significance of TNS. METHODS: This was a multicenter, double-blind, randomized controlled trial. Four hundred fifty-three patients undergoing short transurethral procedures were randomized to receive 1% or 5% hyperbaric lidocaine. Eighty milligrams of 1% or 5% hyperbaric lidocaine was administered. During the first 3 days after surgery, the presence of TNS, its intensity and duration, and patient functional level were recorded. An intention-to-treat analysis was used. RESULTS: There was no difference in the incidence of TNS (21% vs. 18%) between 1% versus 5% lidocaine. Patients with TNS had significantly higher pain scores (5.3 +/- 3 vs. 2.3 +/- 3) than patients without TNS during the first 24 h. This difference in pain scores persisted until 72 h postoperatively. There was a significant difference in the daily activities functional scores (2.2 +/- 1 vs. 1.4 +/- 0.8) of TNS non-TNS patients during the first 24 h postoperatively. CONCLUSIONS:
There was no difference in the incidence of TNS between the 1% versus 5% spinal lidocaine groups. Pain scores were higher in patients with TNS than those who did not have TNS. During the first 48 h postop, a small proportion of patients who had TNS experienced functional impairment of walking, sitting, and sleeping.
Anesth Analg. 2005 Jun;100(6):1811-6.
Transient neurologic symptoms after spinal anesthesia with lidocaine versus other local anesthetics: a systematic review of randomized, controlled trials.
Zaric D, Christiansen C, Pace NL, Punjasawadwong Y.
Department of Anesthesiology, Frederiksberg Hospital, Ndr. Fasanvej 57, 2000 Frederiksberg, Denmark.
[email protected]
Lidocaine has been used for spinal anesthesia since 1948, seemingly without causing concern. However, during the last 10 years, a number of reports have appeared implicating lidocaine as a possible cause of neurologic complications after spinal anesthesia. Follow-up of patients who received uncomplicated spinal anesthesia revealed that some of them developed pain in the lower extremities--transient neurologic symptoms (TNS). In this study, we sought to compare the frequency of 1) TNS and 2) neurologic complications after spinal anesthesia with lidocaine with that after other local anesthetics. Published trials were identified by computerized searches of The Cochrane Library, MEDLINE, LILAC, and EMBASE and by checking the reference lists of trials and review articles. The search identified 14 trials reporting 1347 patients, 117 of whom developed TNS. None of these patients showed signs of neurologic complications. The relative risk for developing TNS after spinal anesthesia with lidocaine was higher than with other local anesthetics (bupivacaine, prilocaine, procaine, and mepivacaine), i.e., 4.35 (95% confidence interval, 1.98-9.54). There was no evidence that this painful condition was associated with any neurologic pathology; in all patients, the symptoms disappeared spontaneously by the 10th postoperative day.
Discussion
The main question addressed by this systematic review was whether lidocaine causes TNS more often than other local anesthetics. The answer is yes. TNS can be caused by all other investigated local anesthetics, but the frequency associated with bupivacaine, prilocaine, and procaine is lower than that with lidocaine. Approximately one of seven patients who received spinal anesthesia with lidocaine developed TNS; the RR was also approximately seven times more for lidocaine compared with bupivacaine, prilocaine, and procaine. Intrathecal mepivacaine seems to have the same tendency to cause TNS as lidocaine. However, more studies are needed to evaluate whether this is a correct assumption.
Pain in the lower back is a very common complication after spinal anesthesia (26) with any local anesthetic. Its etiology is unknown, but no connection to neurologic pathology has been suggested in the literature. Lower back pain is different from pain experienced in the buttocks and lower extremities after recovery from spinal anesthesia, which has been denoted as TNS and also shows no evidence for localized nerve damage.
Studies with different concentrations and doses of lidocaine have shown that the incidence of TNS was not dose dependent (27,28). All forms of lidocaine have been associated with TNS: hyperbaric and isobaric (27), as well as that diluted with cerebrospinal fluid (28). The cause of this painful condition is unknown, and none of the speculations on its origin has been substantiated.
27. Hampl KF, Schneider MC, Pargger H, et al. A similar incidence of transient neurologic symptoms after spinal anesthesia with 2% and 5% lidocaine. Anesth Analg 1996;83:10514. Ovid Full Text Bibliographic Links
Abstract
Recent reports suggest that transient neurologic symptoms are common after spinal anesthesia with 5% lidocaine.To determine whether reducing the anesthetic concentration might decrease the incidence of symptoms, 50 ASA class I or II patients undergoing brief gynecologic procedures under spinal anesthesia were randomly allocated to receive 1 mg/kg of either 5% or 2% lidocaine in 7.5% glucose. Patients were evaluated on the first postoperative day by an anesthesiologist who was unaware of the solution administered or the details of the anesthetic procedure.
Symptoms suggestive of transient radicular irritation were observed in 8 patients (32%) receiving 5% lidocaine, and in 10 patients (40%) receiving 2% lidocaine (NS). These results confirm our previous findings that transient neurologic symptoms may occur in up to one third of the patients receiving 5% lidocaine, and indicate that a modest reduction in lidocaine concentration does not reduce risk.
