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(683)
Abstracts
S21
B30 - Other
C. Disease Entities (Human)
(680) Ethnic differences in acute pain and analgesic side effects
C01 - Amputation Pain
B Hastie, M Stavropoulos, K Virtusio, R Frye, M Wallace, L Quintero, B Sack, R Fillingim; University of Florida, Gainesville, FL Ethnic differences in pain have been established in experimental settings as well as in clinical chronic pain populations; however, scant attention has been given to ethnic differences in post-operative pain and side effect profiles. 25 healthy individuals (68% female; mean age⫽22) representing three ethnic groups (African Americans/AA, 16%; Asians/AS 24%, non-Hispanic whites/W, 60%) were identified as candidates for surgical extraction of all four third molars. Day of surgery (DOS) mood and anxiety, pre and post-operative blood draws were obtained and third molar extraction performed. Participants recorded daily diaries of pain and side effects (SE) the DOS and at timed intervals for three days post-operatively. Level of surgery difficulty, duration, type and amount of pre- and peri-operative medication also were comparable across groups. Standardized-timed plasma concentrations of Fentanyl post-operatively revealed no differences across groups. No group differences emerged in post-operative analgesic use. Compared to whites, minorities consistently reported higher post-operative pain (POP) on DOS, Days 1 and 2 (p’s⬍.03). Both AA and AS reported heightened SE, with AS generally reporting significantly higher adverse cognitive and somatic SE (i.e. dizziness, confusion, dry mouth) while AA generally displayed more “positive” SE profile (i.e. euphoria, relaxed)(p’s ⬍.05) compared to W. Both AA and AS reported significant nausea that persisted all post-operative days. These pain and SE profile differences maintained across all 3 days post-operatively even after accounting for variations in body weight, timing and type of post-operative medications (p’s⬍.05). This is one of the first studies to report POP and SE profiles in a multi-ethnic acute pain sample. The fact that minorities reported significantly increased POP and SE suggest their experience from an acute surgical procedure and recovery may differ from whites. These findings may have important clinical implications for post-operative recovery and suggest the need for additional study of the underlying mechanisms.
(682) Incidence and severity of pain in the first year after amputation
(681) Evaluation of pharmacological effects in the rat using the Neurometer™
(683) Concordance between different subsets of the postamputation population is the rule: An analysis of psychophysical variables
A Ritter, K Parsons, E McGowan, C Abbadie; Merck Research Labs, Rahway, NJ The Neurometer is a sensory threshold testing device that has been used to diagnose sensory deficits in humans, but few studies describe its utility in detecting changes in sensory threshold after pharmacological intervention. These studies were done to assess its utility in that capacity in a pre-clinical species. Male Sprague-Dawley rats (200-250 g) were habituated to a tube-type restrainer before testing. A stimulating electrode was placed on the tail and a reference electrode placed on a depilated portion of the flank. The Neurometer outputs current at 2000, 250 and 5 Hz, which are purported to selectively activate A , A␦ , and C-fibers, respectively. For each frequency, current was incremented stepwise from zero until the rat flicked its tail or vocalized. For each frequency this was repeated 5 times, and the three most consistent values were averaged to calculate threshold. Rats were removed from the restrainer and dosed. 1 hour later, they were returned to the restrainer and re-tested. Morphine was tested at 0.3, 1 and 3 mpk (n⫽6 per group). Thresholds at 0.3 mpk were slightly elevated at all frequencies, but not statistically different from saline. 1 mpk produced elevations of 26%, 52%, and 64% above saline at the 2000 Hz, 250 Hz, and 5 Hz frequencies respectively. 3 mpk produced elevations of 74%, 159% and 81% above saline alone, and these values returned to baseline levels by 4 hours post-dose. Mexiletine at 30 and 60 mpk produced threshold elevations statistically different from vehicle only at the 250 and 5 Hz frequencies. Using the Neurometer we can detect the presence of analgesics that act by distinct mechanisms. Further experiments will be done to determine which classes of analgesics can be detected, and we will determine what doses are required to elevate thresholds, compared to therapeutic or sedative doses.
D Ehde, M Jensen, R Williams, D Smith; University of Washington, Seattle, WA Although chronic pain is known to be a serious problem among many persons with acquired amputation, little is known about the incidence and severity of pain in the first year following amputation. This study sought to describe the incidence and severity of phantom limb pain (PLP), residual limb pain (RLP), back pain, and other types of pain in a cohort of prospectively followed adults with newly acquired amputation. Consecutive cases (N ⫽ 130) of new amputations were recruited from a Level I trauma hospital and a VA hospital. Measures of pain locations, pain intensity (Numeric Rating Scale-11), and pain severity (Chronic Pain Grade, Brief Pain Inventory) as well as demographic and medical variables were collected via structured telephone interviews at 1, 3, 6, and 12 months post amputation. The sample was 80% male, 89% Caucasian, and had a mean age of 52.0 years. The incidence of PLP at 1, 3, 6, and 12 months post amputation was 73%, 76%, 74%, and 72%, respectively. RLP was reported by 17%, 16%, 11%, and 17% at 1, 3, 6, and 12 months. Back pain was prevalent and remained fairly constant within the first year (40%, 41%, 40%, and 33%). Between 40% and 52% of the sample reported pain in other locations (eg, shoulders, nonamputated limb) across the first year. Although rates of pain were constant over time, overall pain severity decreased over time. However, over 25% of the sample reported severe pain at 12 months. The findings suggest that PLP and back pain are very prevalent and stable in the first year after an amputation. The findings highlight the significance of various pain problems following amputation and suggest the need for the development and testing of interventions that will prevent and/or decrease pain and its impact in persons with acquired amputations.
G Arnold, O Wille, R Harden, C Gagnon; Rehabilitation Institute of Chicago, Chicago, IL Post-amputation pain (PAP) is clinically relevant, sometimes dramatic and often difficult to treat. There are many hypotheses as to pathophysiology, with the discussion evolving from a lightly regarded psychogenic phenomenon to complex mechanisms involving both the central and peripheral nervous system. Furthermore, much has been speculated about the various subsets regarding pathophysiology, even though little is certain. Our data shows that when subsets are analyzed many psychophysical variables show no difference. Psychophysical similarity and concordance between empirical subsets is the apparent rule. Side to side thermal Quantitative Sensory Testing of 36 unilateral amputees shows little variation within subsets as to temperature perception or thermal pain thresholds, specifically when grouping patients into traumatic versus non-traumatic pathology, sex, or race. Quantitative infrared telethermography showed significant side to side differences (p ⬍.05), but did not differ between the above empiric subsets or by time since amputation. The data set is small and cannot dispel definitively certain hypothesis regarding the nature of subsets of PAP. However our data supports the hypothesis that in subsets defined by sex, race, and traumatic versus non-traumatic pathology that there is no distinction in temperature perception, thermal pain threshold, or telethermographic side to side differences. This data has hypothetical relevance, e.g. dysvascular amputees have no greater relative coolness of residual limbs than post traumatic amputees, suggesting that the side to side coolness seen is possibly due to sympathetic asymmetry rather than underlying hypoperfusion. Larger samples are needed to see if these hypotheses are supported.
S21
B30 - Other
C. Disease Entities (Human)
(680) Ethnic differences in acute pain and analgesic side effects
C01 - Amputation Pain
B Hastie, M Stavropoulos, K Virtusio, R Frye, M Wallace, L Quintero, B Sack, R Fillingim; University of Florida, Gainesville, FL Ethnic differences in pain have been established in experimental settings as well as in clinical chronic pain populations; however, scant attention has been given to ethnic differences in post-operative pain and side effect profiles. 25 healthy individuals (68% female; mean age⫽22) representing three ethnic groups (African Americans/AA, 16%; Asians/AS 24%, non-Hispanic whites/W, 60%) were identified as candidates for surgical extraction of all four third molars. Day of surgery (DOS) mood and anxiety, pre and post-operative blood draws were obtained and third molar extraction performed. Participants recorded daily diaries of pain and side effects (SE) the DOS and at timed intervals for three days post-operatively. Level of surgery difficulty, duration, type and amount of pre- and peri-operative medication also were comparable across groups. Standardized-timed plasma concentrations of Fentanyl post-operatively revealed no differences across groups. No group differences emerged in post-operative analgesic use. Compared to whites, minorities consistently reported higher post-operative pain (POP) on DOS, Days 1 and 2 (p’s⬍.03). Both AA and AS reported heightened SE, with AS generally reporting significantly higher adverse cognitive and somatic SE (i.e. dizziness, confusion, dry mouth) while AA generally displayed more “positive” SE profile (i.e. euphoria, relaxed)(p’s ⬍.05) compared to W. Both AA and AS reported significant nausea that persisted all post-operative days. These pain and SE profile differences maintained across all 3 days post-operatively even after accounting for variations in body weight, timing and type of post-operative medications (p’s⬍.05). This is one of the first studies to report POP and SE profiles in a multi-ethnic acute pain sample. The fact that minorities reported significantly increased POP and SE suggest their experience from an acute surgical procedure and recovery may differ from whites. These findings may have important clinical implications for post-operative recovery and suggest the need for additional study of the underlying mechanisms.
(682) Incidence and severity of pain in the first year after amputation
(681) Evaluation of pharmacological effects in the rat using the Neurometer™
(683) Concordance between different subsets of the postamputation population is the rule: An analysis of psychophysical variables
A Ritter, K Parsons, E McGowan, C Abbadie; Merck Research Labs, Rahway, NJ The Neurometer is a sensory threshold testing device that has been used to diagnose sensory deficits in humans, but few studies describe its utility in detecting changes in sensory threshold after pharmacological intervention. These studies were done to assess its utility in that capacity in a pre-clinical species. Male Sprague-Dawley rats (200-250 g) were habituated to a tube-type restrainer before testing. A stimulating electrode was placed on the tail and a reference electrode placed on a depilated portion of the flank. The Neurometer outputs current at 2000, 250 and 5 Hz, which are purported to selectively activate A , A␦ , and C-fibers, respectively. For each frequency, current was incremented stepwise from zero until the rat flicked its tail or vocalized. For each frequency this was repeated 5 times, and the three most consistent values were averaged to calculate threshold. Rats were removed from the restrainer and dosed. 1 hour later, they were returned to the restrainer and re-tested. Morphine was tested at 0.3, 1 and 3 mpk (n⫽6 per group). Thresholds at 0.3 mpk were slightly elevated at all frequencies, but not statistically different from saline. 1 mpk produced elevations of 26%, 52%, and 64% above saline at the 2000 Hz, 250 Hz, and 5 Hz frequencies respectively. 3 mpk produced elevations of 74%, 159% and 81% above saline alone, and these values returned to baseline levels by 4 hours post-dose. Mexiletine at 30 and 60 mpk produced threshold elevations statistically different from vehicle only at the 250 and 5 Hz frequencies. Using the Neurometer we can detect the presence of analgesics that act by distinct mechanisms. Further experiments will be done to determine which classes of analgesics can be detected, and we will determine what doses are required to elevate thresholds, compared to therapeutic or sedative doses.
D Ehde, M Jensen, R Williams, D Smith; University of Washington, Seattle, WA Although chronic pain is known to be a serious problem among many persons with acquired amputation, little is known about the incidence and severity of pain in the first year following amputation. This study sought to describe the incidence and severity of phantom limb pain (PLP), residual limb pain (RLP), back pain, and other types of pain in a cohort of prospectively followed adults with newly acquired amputation. Consecutive cases (N ⫽ 130) of new amputations were recruited from a Level I trauma hospital and a VA hospital. Measures of pain locations, pain intensity (Numeric Rating Scale-11), and pain severity (Chronic Pain Grade, Brief Pain Inventory) as well as demographic and medical variables were collected via structured telephone interviews at 1, 3, 6, and 12 months post amputation. The sample was 80% male, 89% Caucasian, and had a mean age of 52.0 years. The incidence of PLP at 1, 3, 6, and 12 months post amputation was 73%, 76%, 74%, and 72%, respectively. RLP was reported by 17%, 16%, 11%, and 17% at 1, 3, 6, and 12 months. Back pain was prevalent and remained fairly constant within the first year (40%, 41%, 40%, and 33%). Between 40% and 52% of the sample reported pain in other locations (eg, shoulders, nonamputated limb) across the first year. Although rates of pain were constant over time, overall pain severity decreased over time. However, over 25% of the sample reported severe pain at 12 months. The findings suggest that PLP and back pain are very prevalent and stable in the first year after an amputation. The findings highlight the significance of various pain problems following amputation and suggest the need for the development and testing of interventions that will prevent and/or decrease pain and its impact in persons with acquired amputations.
G Arnold, O Wille, R Harden, C Gagnon; Rehabilitation Institute of Chicago, Chicago, IL Post-amputation pain (PAP) is clinically relevant, sometimes dramatic and often difficult to treat. There are many hypotheses as to pathophysiology, with the discussion evolving from a lightly regarded psychogenic phenomenon to complex mechanisms involving both the central and peripheral nervous system. Furthermore, much has been speculated about the various subsets regarding pathophysiology, even though little is certain. Our data shows that when subsets are analyzed many psychophysical variables show no difference. Psychophysical similarity and concordance between empirical subsets is the apparent rule. Side to side thermal Quantitative Sensory Testing of 36 unilateral amputees shows little variation within subsets as to temperature perception or thermal pain thresholds, specifically when grouping patients into traumatic versus non-traumatic pathology, sex, or race. Quantitative infrared telethermography showed significant side to side differences (p ⬍.05), but did not differ between the above empiric subsets or by time since amputation. The data set is small and cannot dispel definitively certain hypothesis regarding the nature of subsets of PAP. However our data supports the hypothesis that in subsets defined by sex, race, and traumatic versus non-traumatic pathology that there is no distinction in temperature perception, thermal pain threshold, or telethermographic side to side differences. This data has hypothetical relevance, e.g. dysvascular amputees have no greater relative coolness of residual limbs than post traumatic amputees, suggesting that the side to side coolness seen is possibly due to sympathetic asymmetry rather than underlying hypoperfusion. Larger samples are needed to see if these hypotheses are supported.