Original Contributions Comparison of Lower Extremity Cutaneous Temperature Changes in Patients Receiving Lumbar Sympathetic Ganglion Blocks versus Epidural Anesthesia Steven M. Frank, MD,* Hossam K. El-Rahmany, MD,† Kha M. Tran, MD,‡ Brian Vu, MD,‡ Srinivasa N. Raja, MD§
*Associate Professor †Research Fellow ‡Resident §Professor Address correspondence to Dr. Steven M. Frank, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins Medical Institutions, Carnegie 280, 600 N. Wolfe St., Baltimore, MD 21287, USA. Email:
[email protected] Supported in part by NIH NS26363 (S.N.R.), Bethesda, MD, and by an educational grant from the Egyptian Cultural and Educational Bureau, Washington, D.C. (H.K.E.). Received for publication January 27, 2000; revised manuscript accepted for publication September 7, 2000.
Study Objective: To investigate if paravertebral lumbar sympathetic ganglion block and lumbar epidural anesthesia result in comparable cutaneous temperature changes in the lower extremity. Design: Nonrandomized comparison study. Setting: Operating rooms and pain clinic procedure rooms in a tertiary care hospital. Patients and Interventions: 18 patients undergoing lumbar sympathetic ganglion blocks for the diagnosis and/or treatment of chronic pain, and 13 patients undergoing lumbar epidural anesthesia for radical prostatectomy. Measurements: Cutaneous temperatures were measured over the great toe, calf, and thigh in all patients. Mean maximum temperature (Tmax), rate of change of skin temperature (from 5% to 95% of maximum temperature change), and mean time to 1°C increase, and 50% and 95% of maximum temperature change for each group were compared. Temperature changes for the epidural and lumbar sympathetic block patients were compared. Main Results: Epidural and lumbar sympathetic block resulted in similar Tmax (34.1 ⫾ 0.2 and 33.8 ⫾ 0.9°C, respectively, mean ⫾ SEM; p ⫽ 0.18) and rate of temperature change (0.64 ⫾ 0.09 and 0.49 ⫾ 0.07°C/min; p ⫽ 0.2) in the great toe. The onset of cutaneous temperature change after lumbar sympathetic block was slower than after epidural anesthesia (1°C increase: 17 and 11 min, respectively, 50% of Tmax: 25 and 17 min, respectively, and 95% of Tmax: 40 and 31 min, respectively; p ⬍ 0.05 for each). Conclusions: The similar rate and magnitude of cutaneous temperature change in the distal lower extremity suggests the degree of sympathetic blockade is similar with lumbar sympathetic blockade and epidural anesthesia. Either technique should provide adequate sympathectomy for treating sympathetically maintained pain once the diagnosis has been confirmed using selective sympathetic blockade. © 2000 by Elsevier Science Inc. Keywords: Epidural, Lumbar sympathetic block; pain; skin temperature.
Journal of Clinical Anesthesia 12:525–530, 2000 © 2000 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
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Original Contributions
Introduction Sympathetic blocks are performed for the diagnosis and treatment of a number of pain states including complex regional pain syndrome (CRPS), frost bite, peripheral vascular disease, and acute shingles.1 Sympathetic blockade of an extremity can be achieved by paravertebral block of the sympathetic chain or by neuraxial blocks, e.g., epidural or spinal block. Although it is generally accepted that profound sympatholysis can be achieved with neuraxial blockade,2 it is unclear whether the same degree of sympatholysis can be achieved with lumbar sympathetic blockade. Compared with differential spinal or epidural blocks, paravertebral sympathetic ganglion block is the preferred technique for diagnostic block, i.e., to determine the presence or absence of sympathetically mediated pain (SMP), because false-positive tests secondary to blockade of somatic afferent fibers are minimized.3 However, neuraxial techniques are often preferred for the treatment of SMP states because less technical skill and training is required and continuous catheter techniques can be used for prolonged sympathetic blockade. Using cutaneous temperature changes as an index of sympatholysis, we tested the hypothesis that paravertebral lumbar sympathetic and epidural blocks result in similar degrees of sympathetic blockade. Patients receiving these two treatment modalities were evaluated to assess the onset and time course of cutaneous temperature changes, as well as the maximum temperature change in the lower extremity.
Materials and Methods Patient Population With approval from the Johns Hopkins Hospital Committee on Clinical Investigation and written informed consent, we enrolled 28 patients at the Johns Hopkins Hospital into the study. Two groups of patients were compared: Group 1 (n ⫽ 18) patients were suspected to have SMP who were treated with lumbar sympathetic block, and Group 2 (n ⫽ 13) patients were undergoing radical prostatectomy for prostatic cancer receiving epidural anesthesia. Three patients were allowed to participate twice in the protocol (all from Group 1). All patients were ASA physical status I or II, and no patients had significant cardiac or pulmonary disease. No patient had a history of thyroid disorder or recent febrile illness.
Regional Block Techniques Epidural blocks were performed at the L2 to L3 interspace using the loss-of-resistance technique with midline approach as follows. With patients in the sitting position on the operative table, the back was prepped and draped using sterile technique. Local anesthesia was given using 1% lidocaine. A 3.5-inch, 18-gauge Touhy needle was advanced into the epidural space using the loss-of-resistance method. A catheter was passed, and after negative 526
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aspiration for blood and cerebrospinal fluid (CSF), 3 mL of 2% lidocaine with 1:200,000 epinephrine was injected as a test dose to rule out intravascular or intrathecal positioning. Two to three minutes after the test dose, bupivacaine hydrochloride (0.5%, 15–18 mL) was then injected. Patients underwent sensory testing by pinprick and somatic blockade was confirmed as loss of sensation. Patients were covered with one layer of surgical drapes and one cotton blanket over the upper extremities. Lumbar sympathetic block was performed under fluoroscopic guidance using a single needle technique as follows. Patients were placed in a prone position on the operative table, the back was prepped and draped using sterile technique. The third lumbar vertebra was identified. A skin wheal was made with 1% lidocaine 6 to 7 cm lateral to the midline at the level of the L3 spinous process. A 5 or 7 inch, 22-gauge needle was advanced to the anterolateral edge of L3. Confirmation of the needle position was done using posteroanterior and lateral fluoroscopic views. After negative aspiration for blood and CSF, 3 mL of 2% lidocaine with 1:200,000 epinephrine was injected as a test dose to rule out intravascular or intrathecal positioning of the needle. Two to three minutes after the test dose, bupivacaine hydrochloride (0.25%, 15 mL) was then injected. All patients underwent sensory testing by light touch and pinprick, to confirm the absence of an inadvertent somatic blockade. The patients were covered with one layer of cotton blanket below the level of the shoulders during the procedure. Patients in both groups were sedated during the procedure with intravenous (IV) midazolam in 0.5-mg increments up to 5 mg, and IV fentanyl in 25-mcg increments up to 150 mcg, as needed to maintain sedation.
Temperature Monitoring Ambient temperature in both groups was controlled to minimize the differences between groups with a target temperature of approximately 21°C. Ambient temperature was measured at a site remote from the heat-generating monitoring equipment and reported as the average temperature for the entire period of the study. Change in cutaneous temperature was measured as an index of the efficacy of sympathetic blockade. Core temperature was measured at the tympanic membrane by a flexible cotton covered thermocouple probe. The tympanic probe was advanced until the patients felt the thermocouple touch the tympanic membrane, and then taped in place. Skin temperatures were measured on the great toe, midcalf, and midthigh for 60 minutes after the block. All temperatures were measured by thermocouples (Mona-therm™, Mallinckrodt Inc., St. Louis, MO). Tympanic and skin temperatures at all sites were measured at 1-minute intervals and recorded by a multichannel body temperature monitoring and data acquisition system (Iso-thermex™, Columbus Instruments, Columbus, OH) with a direct interface to a laptop computer.
Lumbar sympathetic blockade vs. epidural anesthesia: Frank et al.
Table 1 Patient demographics
Characteristics Number Age (yrs) Gender Males (n) Females (n) Height (cm) Weight (kg) Ambient temperature (°C) Preblock skin temperature (°C) great toe calf thigh Pre-block core temperature (°C) Post-block core temperature (°C)
Lumbar epidural
Lumbar sympathetic
p-value
13 61 ⫾ 2
18 46 ⫾ 2
⬍0.0001
13 0 180 ⫾ 8 80 ⫾ 3 21.5 ⫾ 0.4
7 11 175 ⫾ 9 74 ⫾ 6 21.8 ⫾ 0.5
0.0004
24.7 ⫾ 0.8 33.2 ⫾ 0.4 33.7 ⫾ 0.3 36.6 ⫾ 0.1 35.7 ⫾ 0.1
23.6 ⫾ 0.6 30.3 ⫾ 0.4 31.8 ⫾ 0.3 36.6 ⫾ 0.1 36.4 ⫾ 0.1
0.3 ⬍0.0001 0.0002 0.8 0.0004
0.21 0.06 0.45
Note: Data are means ⫾ SEM.
Statistical Methods The chi-square and unpaired Student t-tests were used to compare the two groups for dichotomous and continuous measurements, respectively. Analysis of variance (ANOVA) for repeated measures was used to compare differences between and within the two groups for variables measured over time. All analyses were performed with either SuperANOVA™ (Abacus, Berkeley, CA) or JMP™ (SAS Institute INC, Cary, NC) computer programs. All data are given as means ⫾ standard error of the means and p ⬍ 0.05 was used to define significance.
Results The demographic data are given in Table 1. Age and gender were different in the two groups since all epidural patients were elderly males due to the nature of their disease (prostatic cancer). The mean preblock skin-surface temperatures over the calf and thigh were lower in the patients with CRPS. Preblock skin temperature over the great toe did not differ between groups (p ⫽ 0.2). The two groups had similar preblock core temperatures (p ⫽ 0.8). The typical sensory block level in the epidural group was at the T4–T6 dermatomal level. There were no failed blocks in either group of patients.
The onset of cutaneous temperature changes after lumbar sympathetic block was slower than that following epidural block. The lumbar sympathetic block group took longer to develop a 1°C increase in great toe temperature (p ⫽ 0.04), a 50% of maximum great toe temperature change (p ⫽ 0.02), and a 95% of maximum great toe temperature change (p ⫽ 0.04; Table 2).
Thigh Skin Temperature Changes Pre-block thigh skin temperature was significantly greater in the epidural group compared to lumbar sympathetic block group (p ⫽ 0.0004) (Table 1). One hour after the block, thigh temperature was similar between groups (33.5 ⫾ 0.4°C and 33.6 ⫾ 0.5°C in the epidural and lumbar sympathetic block groups, respectively; p ⫽ 0.7) (Figure 2).
Great Toe Temperature Changes Great toe temperature increased over the first postblock hour in both groups. One hour after the block, toe temperature was similar (not significantly different) between groups (34.1 ⫾ 0.2°C and 33.8 ⫾ 0.9°C in the epidural and lumbar sympathetic block groups respectively; p ⫽ 0.18) (Figure 1 and Table 2). After the onset of temperature change, the maximum rate of change in the great toe was similar between the epidural (0.64 ⫾ 0.09°C/min) and lumbar sympathetic block (0.49 ⫾ 0.07°C/min) groups (p ⫽ 0.2; Table 2).
Figure 1. Great toe skin temperature changes following epidural versus lumbar sympathetic blocks. *p ⬍ 0.05 vs. lumbar sympathetic block J. Clin. Anesth., vol. 12, November 2000
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and lumbar sympathetic block groups, respectively (p ⫽ 0.02) (Fig. 2).
Core Temperature Changes Pre-block core temperature measured at the tympanic membrane was similar in both groups (p ⫽ 0.8). Core temperature was lower in the epidural group (35.7 ⫾ 0.1°C) than in the lumbar sympathetic block group (36.4 ⫾ 0.1°C) 1 hour after the block (p ⫽ 0.0004) (Figure 2). To detect the possibility of a type II error with regard to showing no difference in distal extremity temperature changes, a power calculation was performed. Power was 0.83, indicating that type II error was unlikely.
Discussion
Figure 2. Thigh and calf skin temperature and core temperature changes following epidural versus lumbar sympathetic blocks. *p ⬍ 0.05 vs. lumbar sympathetic block
Calf Skin Temperature Changes Pre-block calf skin temperature was significantly greater in the epidural group compared to lumbar sympathetic block (p ⫽ 0.0001) (Table 1). One hour after the block, calf temperature remained significantly greater in epidural group, (34.1 ⫾ 0.4°C and 32.6 ⫾ 0.5°C in epidural 528
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In the clinical setting that was studied, both lumbar sympathetic and epidural blocks resulted in increased skin temperature in the thigh, calf, and the great toe, with the greatest rate of increase in temperature occurring in the great toe in both groups. The comparable maximum great toe temperature in both groups suggests the degree of sympathetic blockade was equivalent in both groups. The slower onset time for cutaneous temperature change with lumbar sympathetic block may be due in part to lower concentration of local anesthetic used. Alternatively, or in addition, there may be a slower onset of cutaneous temperature change in patients with CRPS due to alterations in vasomotor tone associated with this condition. Eighty percent of CRPS cases have temperature differences such that the affected side might be cooler or warmer than the contralateral side.4 Irazuzta et al.5 found a lower baseline toe skin blood flow by laser Doppler flowmetry in affected limbs of patients with CRPS compared to unaffected limbs. The decreased skin blood flow and decreased skin temperature may not reflect increased sympathetic tone, but rather an increase in adrenoceptor sensitivity in the affected extremity.6 These abnormalities in cutaneous blood flow regulation may have influenced both the rate and the maximum skin temperature change in our study. Nonetheless, posttreatment cutaneous temperatures in the distal extremity were similar in both groups, suggesting equivalent sympathectomy was achieved in both groups. When results from the current study are considered along with those from previous studies, it appears that sympatholysis is achieved to a similar degree with all three of the commonly used techniques: 1) spinal, 2) epidural, and 3) lumbar sympathetic ganglionic block. Using the cold pressor test as a sympathetic stimulus, spinal and epidural anesthesia to a T3 to T4 level result in similar attenuation of the vasopressor response.7 In patients given epidural anesthesia, sympathetic block is nearly complete8 and generally precedes the sensory block for cold stimulus, to pain, and to light touch.9 Given these findings, it is apparent that sympathetic blockade is easily and quickly achieved regardless of the regional anesthetic or analgesic technique. Because the postganglionic sympathetic nerves
Lumbar sympathetic blockade vs. epidural anesthesia: Frank et al.
Table 2 Cutaneous temperature changes in the great toe
Characteristics Time to 1°C increase in temperature (min) Maximum post-block temperature (°C) Rate of change in temperature (°C/min) Time to 50% of maximal temperature (min) Time to 95% of maximal temperature (min)
Lumbar epidural
Lumbar sympathetic
p-value
11.4 ⫾ 1.9 34.1 ⫾ 0.2 0.64 ⫾ 0.09 16.7 ⫾ 2.5 30.8 ⫾ 3.1
16.8 ⫾ 1.7 33.8 ⫾ 0.9 0.49 ⫾ 0.07 24.8 ⫾ 2.2 39.7 ⫾ 2.7
0.04 0.18 0.2 0.02 0.04
Note: Data are means ⫾ SEM.
are thin, unmyelinated fibers, they are easily and more rapidly blocked compared to sensory and motor fibers.10 In the present study, core temperature decreased in both groups, with a small decrease in the lumbar sympathetic block group and a greater decrease in the epidural group. Hypothermia is common after epidural block and is thought to result from both redistribution of heat from central to peripheral regions of the body,11,12 and from radiation heat loss from the skin-surface to the environment, secondary to sympathetically induced vasodilatation.13,14 Because the sympathetic block was unilateral and at a low dermatomal level in the lumbar sympathetic block group, the decrease in core temperature was less than in the epidural group. There are several limitations in the current study that must be considered to allow appropriate interpretation of the results and appropriate conclusions. The first is the difference in bupivacaine dose and concentration between groups, as previously discussed. Despite the lower concentration of bupivacaine in the lumbar sympathetic block group, the rate of change and the maximum change in cutaneous temperature was similar to the epidural group. It is possible that we underestimated the magnitude of sympathectomy with lumbar sympathetic blockade based on this concentration difference. The second limitation is the difference in age and underlying pathology between both groups. Several important changes occur with aging that make control of body temperature and cutaneous blood flow less effective than in older people. This consideration may explain the lower core temperature in the epidural group, but a more likely explanation is the proportionally larger area of the body surface that is vasodilated in the epidural group, resulting in cutaneous heat loss and a lower core temperature. The lower baseline cutaneous temperature in the lumbar sympathetic block group is clearly evident and most likely related to the pathophysiological changes characteristic of CRPS, which include an increased density and sensitivity of alpha-adrenoceptors resulting in increased vasomotor tone.15,16 Cutaneous temperature, however, in the most distal portion of the extremity was similar in both treatment groups both at the start and end of the study, suggesting that sympathetic tone was similarly affected in the two groups. Sympathetic function can be assessed by several different methods. These include cutaneous blood flow mea-
surements, cutaneous temperature changes, regional blood catecholamine sampling, sweat testing, and microneurography. Temperature change was used in the current study since the method is simple, inexpensive, and relatively well correlated with regional blood flow changes.17 It is possible that other methods may be more sensitive measures of sympathetic function, and that relying on temperature changes alone may represent a limitation in the current study. We conclude that lumbar epidural and lumbar sympathetic ganglion blocks result in similar maximum temperatures and rate of cutaneous temperature change in the distal lower extremity, suggesting that both techniques result in similar degrees of sympathetic blockade. The lower baseline skin-surface temperatures over portions of the lower extremity in the CRPS group is likely related to their underlying pathophysiological abnormality. Cutaneous temperature measurement in the distal portion of the extremity can be used as a clinical measure of sympathetic blockade. Using this method, our results suggest a relatively complete sympathetic blockade following lumbar sympathetic ganglionic blocks.
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