Effect of intravenous sodium amytal on cutaneous limb temperatures and sympathetic skin responses in normal subjects and pain patients with and without Complex Regional Pain Syndromes (type I and II). I (original) (raw)
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Pain, 1997
This study examined the effects of intravenous administration of sodium amytal (SA), a medium action barbiturate, on cutaneous limb temperatures and sympathetic skin responses (SSR) to electrical stimulation. Eight normal volunteers and 13 patients with musculoskeletal pain, somatoform pain disorders or nerve/root injury (with findings strictly limited to the distribution of the involved nerve) were compared to 15 patients with Complex Regional Pain Syndromes (one of whom had documented nerve injury). The Complex Regional Pain Syndromes (CRPS) patients were characterized by the presence of severe diffuse limb pain and extraterritorial sensory, sudomotor and vasomotor abnormalities (i.e., not confined to the site of injury or the distribution of the injured nerve). The CRPS patients were different from the normal controls and the non-CRPS patients in their tendency to warm significantly many of their limbs (not just the symptomatic ones). SSR were reduced or lost in a few limbs only in all three groups, irrespective of the increase or decrease of limb temperature and the side of symptoms. We argue that the enhanced thermogenic effect of SA in CRPS patients is due to generalized central changes of thermoregulatory control specifically in this group.
Experimental Neurology, 2013
Complex regional pain syndrome (CRPS) is characterised by autonomic, sensory, and motor disturbances. The underlying mechanisms of the autonomic changes in CPRS are unknown. However, it has been postulated that sympathetic inhibition in the acute phase with locally reduced levels of noradrenaline is followed by an up-regulation of alpha-adrenoceptors in chronic CRPS leading to denervation supersensitivity to catecholamines. This exploratory study examined the effect of cutaneous sympathetic activation and inhibition on cutaneous noradrenaline release, vascular reactivity, and pain in CRPS patients and in healthy volunteers. Seven patients and nine controls completed whole-body cooling (sympathetic activation) and heating (sympathetic inhibition) induced by a whole-body thermal suit with simultaneous measurement of the skin temperature, skin blood flow, and release of dermal noradrenaline. CRPS pain and the perceived skin temperature were measured every 5 min during thermal exposure, while noradrenaline was determined from cutaneous microdialysate collected every 20 min throughout the study period. Cooling induced peripheral sympathetic activation in patients and controls with significant increases in dermal noradrenaline, vasoconstriction, and reduction in skin temperature. The main findings were that the noradrenaline response did not differ between patients and controls or between the CRPS hand and the contralateral unaffected hand, suggesting that the evoked noradrenaline release from the cutaneous sympathetic postganglionic fibres is preserved in chronic CRPS patients.
Cutaneous norepinephrine application in complex regional pain syndrome
European Journal of Pain, 1997
Patients with complex regional pain syndrome (CRPS) (n = 20) were examined in order to evaluate cutaneous reactions to norepinephrine (NE) on both the affected and the unaffected limb in comparison to healthy controls. Sixteen female and four male patients suffering from very acute and therefore untreated CRPS with a mean duration of 5.5 weeks were included in this study. Two groups of healthy volunteers served as control groups: the first group (n = 18) according to the same study protocol as CRPS patients, and the second group (n = 10) after warming up one limb. Norepinephrine was iontophoresized (0.2 mA, 120 s) and vasoconstriction was recorded by laser-doppler flowmetry. Pain sensations were simultaneously rated on a visual analogue scale (VAS). Five patients underwent a second trial with higher intracutaneous NE concentrations in order to study possible dose-dependent effects of NE on pain sensation. After acclimatization, skin temperature was recorded by infra-red thermography. The NE-induced reduction of skin blood flow was significantly higher in the affected limb in the patient group (33.0 YS 11.2%, ~~~0.005). None of the patients reported pain or hyperalgesia. The skin temperature of CRPS patients was significantly higher in the affected limb (34.7 vs 32.5"C, pcO.001). The first control group did not show any difference between left and right sides concerning NE-induced vasoconstriction or skin temperature. The second control group had an increased unilateral skin temperature after warming up (35.0 vs 34.3"C, p<O.O06) and demonstrated a significantly increased vasoconstriction on the warmer side (52.0 vs 20.2%, ~~0.03) corresponding to findings in patients with acute CRPS. The present study proves that there are signs of decreased sympathetic activity in the affected limb in very acute CRPS. However, no indication was found for increased sensitivity of vascular cc-receptors in the very acute stages of CRPS, and there was also no indication for a significant direct contribution of the sympathetic nervous system to pain in very acute CRPS.
Peripheral neural mechanisms of cutaneous hyperalgesia following mild injury by heat
The Journal of …, 1982
Pain thresholds in humans were determined for heat stimulations of the skin before and after a mild injury induced by a single conditioning stimulus (CS) of 50°C and 100 set duration. The same stimuli were delivered to the receptive fields of C fiber and A fiber mechanoheat-sensitive nociceptors (CMH and AMH nociceptors, respectively) and of low threshold warm and cold receptors in the anesthetized monkey and to the receptive fields of CMH nociceptors recorded percutaneously from the peroneal nerve of awake humans. Pain thresholds in normal skin were matched only by the response thresholds of CMH and not AMH nociceptors. Immediately following heat injury, some pain thresholds and CMH response thresholds were elevated, but by 5 to 10 min after the CS, pain and CMH thresholds were lowered to 2 to 6°C below normal (hyperalgesia and nociceptor sensitization). No other type of cutaneous receptor studied exhibited changes in threshold similar to those observed for pain and for CMH nociceptors. The magnitude of hyperalgesia in humans and the magnitude of sensitization of CMH nociceptors in monkeys following heat injury were greater for hairy than for glabrous skin. The time course of the development of hyperalgesia was not altered by ischemia or conduction block in A fibers. The results support the conclusion that altered activity in CMH nociceptors is a major peripheral determinant of cutaneous hyperalgesia following a mild heat injury to the skin.
Heat, but not mechanical hyperalgesia, following adrenergic injections in normal human skin
2001
The development of adrenergic sensitivity in nociceptors has been suggested as a mechanism of neuropathic pain. We sought to determine if nociceptors in the skin of normal subjects exhibit adrenergic sensitivity. We investigated the effects of intradermal administration of norepinephrine, phenylephrine, and brimonidine on heat pain sensitivity. Norepinephrine and phenylephrine (in concentrations ranging from 0.1 to 10 mM by factors of 10), brimonidine (at 0.01±1 mM), and saline were injected (30 ml volume) in a random, double-blind manner to different sites on the volar surface of the forearm in ten subjects. Before and after the injections, heat testing was performed with a noncontact laser thermal stimulator. Heat pain threshold was measured by means of a`Marstock' technique in which subjects pressed a reaction time key when they perceived that a slowly increasing heat stimulus (18C/s ramp from a 368C base) was painful. In addition, the subjects used magnitude estimation techniques to rate the intensity of pain to a suprathreshold heat stimulus (478C, 2 s). Mechanical testing was done using 200-mm diameter probes attached to calibrated weights that provided forces over the range of 16±512 mN. The intradermal injections of norepinephrine, phenylephrine and brimonidine produced little evoked pain. However, a dose-dependant decrease in heat pain threshold, but not mechanical pain threshold, was observed. At the highest drug dose injected, all three adrenergic compounds produced a signi®cant decrease in heat pain threshold compared to the saline injection. A signi®cant increase in response to the suprathreshold heat stimulus was also found. One possible explanation for this apparent heat hyperalgesia is that the decrease in perfusion due to the localized vasoconstriction may alter the heat response. However, in control studies we found that the non-adrenergic vasoconstrictors, angiotensin II and vasopressin did not produce heat hyperalgesia at doses that produced comparable decreases in blood¯ow. In addition, occlusion of blood¯ow with a blood pressure cuff did not lead to heat hyperalgesia. Thus, the heat hyperalgesia observed with the adrenergic agonists is not due to a decrease in perfusion associated with the injection. These results indicate that a 1 -and a 2 -adrenoceptor-mediated mechanisms may play a role in sensitization of nociceptors to heat stimuli in normal skin.
Europa medicophysica, 2007
Transcutaneous electrical nerve stimulation (TENS) is used worldwide for pain relief, but its mechanisms of action are not completely understood. High frequency transcutaneous peripheral nerve stimulation (HF-TPNS) is a term describing a type of TENS where a peripheral nerve is stimulated transcutaneously. The aim of the investigation was to verify the hypothesis that HF-TPNS increases the heat pain threshold in the skin territory of the stimulated nerve, during and after stimulation. Eighteen volunteers (8 men, 10 women) participated in 2 sessions conducted on different days. In each session their heat pain thresholds were measured in basal conditions and after 5, 10, 15, 25, 40, 70 min. In one session, HF-TPNS was delivered for 10 min immediately after basal evaluation (HF-TPNS session). In the other session the heat pain thresholds only were measured (control session). The superficial radial nerve was stimulated at the wrist (frequency of 100 Hz, pulse duration of 0.1 ms). The he...
2020
Background. TENS (transcutaneous electrical nerve stimulation) is probably the most diffused physical therapy used for antalgic purposes. Although it continues to be used by trial and error, correct targeting of paresthesias evoked by the electrical stimulation on the painful area is diffusely considered very important for pain relief. Aim. To investigate if TENS antalgic effect is higher in the cutaneous area of the stimulated nerve when confronted to neighbouring areas. Methods. 10 volunteers (4 males, 6 females) underwent three different sessions: in two, heat pain thresholds (HPTs) were measured on the dorsal hand skin before, during and after electrical stimulation (100 Hz, 0.1 msec) of superficial radial nerve; in the third session HPTs, were measured without any stimulation. Results. Radial nerve stimulation induced an increase of HPT significantly higher in its cutaneous territory when confronted to the neighbouring ulnar nerve territory, and antalgic effect persisted beyond...
BioMed Research International, 2013
Background. TENS (transcutaneous electrical nerve stimulation) is probably the most diffused physical therapy used for antalgic purposes. Although it continues to be used by trial and error, correct targeting of paresthesias evoked by the electrical stimulation on the painful area is diffusely considered very important for pain relief.Aim. To investigate if TENS antalgic effect is higher in the cutaneous area of the stimulated nerve when confronted to neighbouring areas.Methods. 10 volunteers (4 males, 6 females) underwent three different sessions: in two, heat pain thresholds (HPTs) were measured on the dorsal hand skin before, during and after electrical stimulation (100 Hz, 0.1 msec) of superficial radial nerve; in the third session HPTs, were measured without any stimulation.Results. Radial nerve stimulation induced an increase of HPT significantly higher in its cutaneous territory when confronted to the neighbouring ulnar nerve territory, and antalgic effect persisted beyond th...
Skin Temperature Changes following Sciatic Nerve Injury in Rats
Journal of Neurotrauma, 2012
In the clinical setting, skin temperature is both easily evaluated and useful in assessments of sympathetic dysfunction. The present study purposed to observe the serial skin temperature changes of both hindlimbs following several types of sciatic nerve injury (complete transection and ligation model [CTL], crush injury model [CRI], and chronic constriction injury model [CCI]) in Sprague-Dawley rats and, further, to delineate the possible mechanisms through various evaluation methods. The temperature differences between the intact and injured areas (DT) on the plantar surface and toes varied among the CTL, CRI, and CCI injury models during the acute stage (7 days post-injury). During the subacute to chronic stages (7-28 days post-injury), DT on the plantar area and toes of the CCI model were higher than those of the CTL and CRI models. The sciatic functional index was gradually restored in the CRI and CCI models, but was unchanged in the CTL model. The CTL model showed constant hypoesthesia; the CRI model, contrastingly, was restored to normal, and the CCI model showed gradual hyperesthesia until 28 days post-injury. The latency and amplitude of the compound muscle action potential (CMAP) in the involved plantar muscle was not found in the CTL group 4 weeks post-injury, but showed gradual restoration in the CRI and CCI models. Regression analysis revealed that the DT in the plantar area and toes were affected only by the CMAP amplitude in the involved plantar muscle; therefore, it can be said that the skin temperature on the injured area after sciatic nerve injury was influenced by the functional status of the involved muscle. Measurement of skin temperature can differentiate mild peripheral nerve injury from moderate-to-severe injuries, although its clinical significance might be limited.