Equal Ratio Ventilation Reduces Blood Loss During Posterior Lumbar Interbody Fusion Surgery.

STUDY DESIGN: A prospective randomized double-blinded study. OBJECTIVE: The aim of this study was to compare the effect of two different ventilator modes (inspiratory to expiratory ratio [I:E ratio] of 1:1 and 1:2) on intraoperative surgical bleeding in patients undergoing posterior lumbar interbody fusion (PLIF) surgery. SUMMARY OF BACKGROUND DATA: During PLIF surgery, a considerable amount of blood loss is anticipated. In the prone position, engorgement of the vertebral vein increases surgical bleeding. We hypothesized that equal ratio ventilation (ERV) with I:E ratio of 1:1 would lower peak inspiratory pressure (PIP) in the prone position and consequentially decrease surgical bleeding. METHODS: Twenty-eight patients were randomly assigned to receive either ERV (ERV group, n = 14) or conventional ventilation with I:E ratio of 1:2 (control group, n = 14). Hemodynamic and respiratory parameters were measured at 5 minutes after anesthesia induction, at 5 minutes after the prone position, at the time of skin closure, and at 5 minutes after turning to the supine position. RESULTS: The amount of intraoperative surgical bleeding in the ERV group was significantly less than that in the control group (975.7 ±â€Š349.9 mL vs. 1757.1 ±â€Š1172.7 mL, P = 0.030). Among other hemodynamic and respiratory parameters, PIP and plateau inspiratory pressure (Pplat) were significantly lower and dynamic lung compliance (Cdyn) was significantly higher in the ERV group than those of the control group throughout the study period, respectively (all P < 0.05). CONCLUSION: Compared to conventional ratio ventilation, ERV provided lower PIP and reduced intraoperative surgical blood loss in patients undergoing PLIF surgery.Level of Evidence: 2.

Gabapentin prevents synaptogenesis between sensory and spinal cord neurons induced by thrombospondin-4 acting on pre-synaptic Cav α2 δ1 subunits and involving T-type Ca2+ channels.

BACKGROUND AND PURPOSE: Nerve injury induces concurrent up-regulation of the voltage-gated calcium channel subunit Cav α2 δ1 and the extracellular matrix protein thrombospondin-4 (TSP4) in dorsal root ganglia and dorsal spinal cord, leading to the development of a neuropathic pain state. Interactions of these proteins promote aberrant excitatory synaptogenesis that contributes to neuropathic pain state development through unknown mechanisms. We investigated the contributions of Cav α2 δ1 subunits and TSP4 to synaptogenesis, and the pathways involved in vitro, and whether treatment with gabapentin could block this process and pain development in vivo. EXPERIMENTAL APPROACH: A co-culture system of sensory and spinal cord neurons was used to study the contribution from each protein to synaptogenesis and the pathway(s) involved. Anti-synaptogenic actions of gabapentin were studied in TSP4-injected mice. KEY RESULTS: Only presynaptic, but not postsynaptic, Cav α2 δ1 subunits interacted with TSP4 to initiate excitatory synaptogenesis through a pathway modulated by T-type calcium channels. Cav α2 δ1 /TSP4 interactions were not required for maintenance of already formed synapses. In vivo, early, but not delayed, treatment with low-dose gabapentin blocked this pathway and the development of the pain state. CONCLUSIONS AND IMPLICATIONS: Cav α2 δ1 /TSP4 interactions were critical for the initiation, but not for the maintenance, of abnormal synapse formation between sensory and spinal cord neurons. This process was blocked by early, but was not reversed by delayed, treatment with gabapentin. Early intervention with gabapentin may prevent the development of injury-induced chronic pain, resulting from Cav α2 δ1 /TSP4-initiated abnormal synapse formation. LINKED ARTICLES: This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.

The Antinociceptive Properties of the Corydalis yanhusuo Extract.

Corydalis yanhusuo. W.T. extracts (YHS) are widely used for the treatment of pain and inflammation. There are a few studies that assessed the effects of YHS in pain assays; however, none of these studies has systematically compared its activities in the different pain animal modes namely: acute, inflammatory and chronic pain. Furthermore, little is known about the mechanism of YHS activity in these assays. The aim of this study was to systematically evaluate the antinociceptive properties of YHS by testing it in four standardized pain assays and to investigate its mechanism. YHS antinociceptive properties were analyzed in the tail flick, the formalin paw licking, the von Frey filament and the hot box assays after spinal nerve ligation, which monitors acute nociceptive, persistent inflammatory and chronic neuropathic pain, respectively. YHS pharmacological profile was determined by screening it against a battery of G-protein coupled receptors and its mechanism of action was studied using knock-out mice. Our study shows that YHS, at a non-sedative dose, increases the tail flick latency in the tail flick assay without resulting in development of tolerance. YHS also decreases paw licking time in the formalin assay. Further, YHS increases paw withdraw threshold and latency in the von Frey filament and the hot box assays, respectively. In vitro, YHS exhibits prominent dopamine receptor antagonistic properties. In dopamine D2 receptor knockout mice, its antinociceptive effects are attenuated in acute and neuropathic pain but not inflammatory pain assays. Our results therefore indicate that YHS effectively attenuates acute, inflammatory and neuropathic pain, without causing tolerance. The effects on acute and neuropathic pain, but not inflammatory pain, are at least partially mediated through dopamine D2 receptor antagonism. Since YHS is a dietary supplement commercially available in the United States, our data suggest that it might be a candidate for alternative pain treatment.

Erratum: Heart rate variability as a predictor of hypotension after spinal anesthesia in hypertensive patients.

[This corrects the article on p. 317 in vol. 65, PMID: 24228144.].

Anatomical analysis of medial branches of dorsal rami of cervical nerves for radiofrequency thermocoagulation.

BACKGROUND AND OBJECTIVES: Cervical medial branch blocks are used to treat patients with chronic neck pain. The aim of this study was to clarify the anatomical aspects of the cervical medial branches to improve the accuracy and safety of radiofrequency denervation. METHODS: Twenty cervical specimens were harvested from 20 adult cadavers. The anatomical parameters of the C4-C7 cervical medial branches were measured. The 3-dimensional computed tomography reconstruction images of the bone were also analyzed. RESULTS: Based on cadaveric analysis, most of the cervical dorsal rami gave off 1 medial branch; however, the cervical dorsal rami gave off 2 medial branches in 27%, 15%, 2%, and 0% at the vertebral level C4, C5, C6, and C7, respectively. The diameters of the medial branches varied from 1.0 to 1.2 mm, and the average distance from the notch of inferior articular process to the medial branches was about 2 mm. Most of the bifurcation sites were located at the medial side of the posterior tubercle of the transverse process. On the analysis of 3-dimensional computed tomography reconstruction images, cervical medial branches (C4 to C6) passed through the upper 49% to 53% of a line between the tips of 2 consecutive superior articular processes (anterior line). Also, cervical medial branches passed through the upper 28% to 35% of a line between the midpoints of 2 consecutive facet joints (midline). CONCLUSIONS: The present anatomical study may help improve accuracy and safety during radiofrequency denervation of the cervical medial branches.

Analytical and clinical performance of a new point of care LABGEOIB D-dimer test for diagnosis of venous thromboembolism.

LABGEO(IB) D-dimer Test is a newly developed POC D-dimer assay and the first commercially available POC immunoassay instrument that exploits the disk rotation method for extraction of plasma. Citrate plasma was obtained from 201 apparently healthy subjects and 91 patients suspected for VTE, and their D-dimer level was measured by the LABGEO(IB) D-Dimer Test (LABGEO D-dimer) and HemosIL D-dimer test as a comparative method. To examine the effect of blood cells and anticoagulant, paired blood samples anticoagulated by heparin and citrate were obtained from various postoperative patients. The overall diagnostic performance of LABGEO(IB) D-dimer and HemosIL was comparable with similar area under ROC curve (p=0.79). The cut-off levels recommended by manufacturers (LABGEO D-dimer: 0.45 µg/ml fibrinogen equivalent unit (FEU), HemosIL: 0.23 µg/ml D-dimer unit (DDU)) and those yielding highest diagnostic efficiency (LABGEO D-dimer: 1.41 µg/ml FEU; HemosIL: 0.85 µg/ml DDU), were chosen for the evaluation. For LABGEO D-dimer negative predictive value (NPV), positive predictive value (PPV), sensitivity, specificity, and negative likelihood ratio (LR-neg) were 93-100%, 67-89%, 93-100%, 53-89% and 0.00-0.08. For HemosIL D-dimer, NPV, PPV, sensitivity, specificity and LR-neg were 90 - 100%, 76-95%, 89-100%, 70-96% and 0.00-0.12, all comparable to results for LABGEO D-dimer. LABGEO D-dimer test demonstrated acceptable performance when used for the VTE diagnostic work-up.

Cervical ganglion block attenuates the progression of pulmonary hypertension via nitric oxide and arginase pathways.

It has been recognized that the sympathetic nervous system is activated in pulmonary arterial hypertension (PAH), and abnormal sympathetic hyperactivity leads to worsening of PAH via endothelial dysfunction. The purpose of this study was to examine whether sympathetic ganglion block (SGB) can treat PAH by increasing the availability of nitric oxide (NO). PAH was induced in rats by 50 mg/kg of subcutaneous monocrotaline. After 2 weeks, daily injections of ropivacaine into the left superior cervical ganglion were repeated for 14 days (monocrotaline-SGB group). Monocrotaline group received sham SGB with saline, whereas control group received saline instead of monocrotaline. PAH was evident in monocrotaline group, with right ventricular systolic pressures (47±4 mm Hg) that were higher than those of controls (17±2 mm Hg), whereas SGB significantly attenuated monocrotaline-induced PAH (35±4 mm Hg). The right/left ventricular mass ratios exhibited similar changes to those seen with right ventricular pressures. Heart rate variability showed significantly higher sympathetic activity in the monocrotaline group. Microscopy revealed a higher proportion of muscular arteries with thicker medial walls in the monocrotaline group, which was attenuated by SGB. Monocrotaline induced arginase hyperactivity, which was in turn decreased by SGB-induced endothelial NO synthase activation. SGB restored monocrotaline-induced hypoactivity of superoxide dismutase. In conclusion, SGB could suppress PAH and the remodeling of pulmonary arteries via inactivation of arginase and reciprocal elevation of NO bioavailability, thus attenuating disproportionate hyperactivation of the sympathetic nervous system.

Heart rate variability as a predictor of hypotension after spinal anesthesia in hypertensive patients.

BACKGROUND: Hypotension is a common phenomenon after spinal anesthesia in hypertensive patients. We investigated whether heart rate variability could predict the occurrence of hypotension after spinal anesthesia in hypertensive patients. METHODS: Forty-one patients undergoing spinal anesthesia were included. Heart rate variability was measured at five different time points such as before fluid loading (baseline), after fluid loading as well as 5 min, 15 min and 30 min after spinal anesthesia. Fluid loading was performed using 5 ml/kg of a crystalloid solution. Baseline total power and low to high frequency ratio (LF/HF) in predicting hypotension after spinal anesthesia were analyzed by calculating the area under the receiver operating characteristic curves (AUC). RESULTS: Moderate hypotension, defined as a decrease of mean arterial pressure to below 20-30% of the baseline, occurred in 13 patients and severe hypotension, defined as a decrease of mean arterial pressure greater than 30% below the baseline, occurred in 7 patients. LF/HF ratiosand total powers did not significantly change after spinal anesthesia. AUCs of LF/HF ratio for predicting moderate hypotension was 0.685 (P = 0.074), severe hypotension was 0.579 (P = 0.560) and moderate or severe hypotension was 0.652 (P = 0.101), respectively. AUCs of total power for predicting moderate hypotension was 0.571 (P = 0.490), severe hypotension was 0.672 (P = 0.351) and moderate or severe hypotension was 0.509 (P = 0.924), respectively. CONCLUSIONS: Heart rate variability is not a reliable predictor of hypotension after spinal block in hypertensive patients whose sympathetic activity is already depressed.

Comparison of meperidine and nefopam for prevention of shivering during spinal anesthesia.

BACKGROUND: Shivering is a frequent event during spinal anesthesia and meperidine is a well-known effective drug for prevention and treatment of shivering. Nefopam is a non-opiate analgesic and also known to have an anti-shivering effect. We compared nefopam with meperidine for efficacy of prevention of shivering during spinal anesthesia. METHODS: Sixty five patients, American Society of Anesthesiologists physical status I or II, aged 20-65 years, scheduled for elective orthopedic surgery under spinal anesthesia were investigated. Patients were randomly divided into two groups, meperidine (Group M, n = 33) and nefopam (Group N, n = 32) groups. Group M and N received meperidine 0.4 mg/kg or nefopam 0.15 mg/kg, respectively, in 100 ml of isotonic saline intravenously. All drugs were infused for 15 minutes by a blinded investigator before spinal anesthesia. Blood pressures, heart rates, body temperatures and side effects were checked before and at 15, 30, and 60 minutes after spinal anesthesia. RESULTS: The incidences and scores of shivering were similar between the two groups. The mean arterial pressures in Group N were maintained higher than in Group M at 15, 30, and 60 minutes after spinal anesthesia. The injection pain was checked in Group N only and its incidence was 15.6%. CONCLUSIONS: We conclude that nefopam can be a good substitute for meperidine for prevention of shivering during spinal anesthesia with more stable hemodynamics, if injection pain is effectively controlled.

Hemodynamic effect of full flexion of the hips and knees in the supine position: a comparison with straight leg raising.

BACKGROUND: Straight raising of the legs in the supine position or Trendelenburg positioning has been used to treat hypotension or shock, but the advantages of these positions are not clear and under debate. We performed a crossover study to evaluate the circulatory effect of full flexion of the hips and knees in the supine position (exaggerated lithotomy), and compare it with straight leg raising. METHODS: This study was a prospective randomized crossover study from the tertiary care unit at our university hospital. Twenty-two patients scheduled for off-pump coronary artery bypass surgery were enrolled. Induction and maintenance of anesthesia were standardized. Exaggerated lithotomy position or straight leg raising were randomly selected in the supine position. Hemodynamic variables were measured in the following sequence: 10 min after induction, 1, 5, and 10 min following the designated position, and 1 and 5 min after returning to the supine position. Ten min later, the other position was applied to measure the same hemodynamic variables. RESULTS: During the exaggerated lithotomy position, cerebral and coronary perfusion pressure increased significantly (P < 0.01) without a change in cardiac output. During straight leg raising, cardiac output increased at 5 min (P < 0.05) and cerebral and coronary perfusion pressures did not increase except for cerebral perfusion pressure at 1 min. However, the difference between the two groups at each time point in terms of cerebral perfusion pressure was clinically insignificant. CONCLUSIONS: Full flexion of the hips and knees in the supine position did not increase cardiac output but may be more beneficial than straight leg raising in terms of coronary perfusion pressure.

Sedation under JCI standard.

The practice of anesthesia and sedation continues to expand beyond the operating room and now includes the gastroenterology suite, magnetic resonance imaging suites, and the cardiac catheterization laboratory. Non-anesthesiologists frequently administer sedation, in part because of a lack of available anesthesiologists and economic aspect, which emphasizes the safety of sedation. The Joint Commission International (JCI) set a standard responding to this issue indicating that qualified individuals who have drug and monitoring knowledge as well as airway management skills can only administer sedating agents. In Korea, the Ministry of Health and Welfare developed new sedation standards for hospital evaluation, which is similar to the JCI standards. This review intends to help with the understanding of the JCI sedation standard and compare it to the Korean sedation standard.

Participation of K(ATP) Channels in the Antinociceptive Effect of Pregabalin in Rat Formalin Test.

BACKGROUND: Pregabalin is an anticonvulsant and analgesic agent that interacts selectively with the voltage-sensitive-Ca(2+)-channel alpha-2-delta subunit. The aim of this study was to evaluate whether the analgesic action of intrathecal (IT) pregabalin is associated with K(ATP) channels in the rat formalin test. METHODS: IT PE-10 catheters were implanted in male Sprague-Dawley rats (250-300 g) under inhalation anesthesia using enflurane. Nociceptive behavior was defined as the number of hind paw flinches during 60 min after formalin injection. Ten min before formalin injection, IT drug treatments were divided into 3 groups: normal saline (NS) 20 µl (CON group); pregabalin 0.3, 1, 3 and 10 µg in NS 10 µl (PGB group); glibenclamide 100 µg in DMSO 5 µl with pregabalin 0.3, 1, 3 and 10 µg in NS 5 µl (GBC group). All the drugs were flushed with NS 10 µl. Immunohistochemistry for the K(ATP) channel was done with a different set of rats divided into naïve, NS and PGB groups. RESULTS: IT pregabalin dose-dependently decreased the flinching number only in phase 2 of formalin test. The log dose response curve of the GBC group shifted to the right with respect to that of the PGB group. Immunohistochemistry for the K(ATP) channel expression on the spinal cord dorsal horn showed no difference among the groups 1 hr after the formalin test. CONCLUSIONS: The antinociceptive effect of pregabalin in the rat formalin test was associated with the activation of the K(ATP) channel. However, pregabalin did not induce K(ATP) channel expression in the spinal cord dorsal horn.

The effect of beta1-adrenergic receptor gene polymorphism on prolongation of corrected QT interval during endotracheal intubation under sevoflurane anesthesia.

BACKGROUND: The hemodynamic responses to endotracheal intubation are associated with sympathoadrenal activity. Polymorphisms in the beta1-adrenergic receptor (ß(1)AR) gene can alter the pathophysiology of specific diseases. The aim of this study is to investigate whether the Ser49Gly and Arg389Gly polymorphism of the ß(1)AR gene have different cardiovascular responses during endotracheal intubation under sevoflurane anesthesia. METHODS: Ninety-one healthy patients undergoing general anesthesia were enrolled. Patients underwent slow inhalation induction of anesthesia using sevoflurane in 100% oxygen. Vecuronium 0.15 mg/kg was given for muscle relaxation. Endotracheal intubation was performed by an anesthesiologist. The mean arterial pressure (MAP), heart rate (HR), and the corrected QT (QTc) interval were measured before induction, before laryngoscopy, and immediately after tracheal intubation. Genomic DNA was isolated from the patients' peripheral blood and then evaluated for the ß(1)AR-49 and ß(1)AR-389 genes using an allele-specific polymerase chain reaction method. RESULTS: No differences were found in the baseline values of MAP, HR, and the QTc interval among ß(1)AR-49 and ß(1)AR-389, respectively. In the case of ß(1)AR-49, the QTc interval change immediately after tracheal intubation was significantly greater in Ser/Ser genotypes than in Ser/Gly genotypes. No differences were observed immediately after tracheal intubation in MAP and HR for ß(1)AR-49 and ß(1)AR-389. CONCLUSIONS: We found an association between the Ser49 homozygote gene of ß(1)AR-49 polymorphism and increased QTc prolongation during endotracheal intubation with sevoflurane anesthesia. Thus, ß(1)AR-49 polymorphism may be useful in predicting the risk of arrhythmia during endotracheal intubation in patients with long QT syndrome.

Ultrasonic doppler flowmeter-guided occipital nerve block.

BACKGROUND: Greater occipital nerve block is used in the treatment of headaches and neuralgia in the occipital area. We evaluated the efficacy of ultrasonic doppler flowmeter-guided occipital nerve block in patients experiencing headache in the occipital region in a randomized, prospective, placebo-controlled study. METHODS: Twenty-six patients, aged 18 to 70, with headache in the occipital region, were included in the study. Patients received a greater occipital nerve block performed either under ultrasonic doppler flowmeter guidance using 1% lidocaine or the traditional method. Sensory examination findings in the occipital region were evaluated. RESULTS: The complete block rate of greater occipital nerve blockade in the doppler group was significantly higher than in the control group respectively (76.9% vs. 30.8%, P < 0.05). Only one patient in the control group had a complication (minimal bleeding). CONCLUSIONS: Ultrasonic doppler flowmeter-guided occipital nerve block may be a useful method for patients suffering headache in the occipital region.

Ejaculatory failure after unilateral neurolytic celiac plexus block.

Abdominal pain associated with chronic pancreatitis is often difficult to control with analgesics and can be severely debilitating with significant impairment of quality of life. In these patients, neurolytic celiac plexus block (NCPB) is an effective treatment option with a low complication rate. However, there is a risk of ejaculatory failure after NCPB, which may be a problem in patients with a long life expectancy. We report a case of ejaculatory failure after unilateral NCPB in a patient with chronic pancreatitis.

Stress-induced cardiomyopathy following cephalosporin-induced anaphylactic shock during general anesthesia.

PURPOSE: Anaphylaxis may be caused by various agents during general anesthesia. Sympathetic discharge may occur during anaphylaxis, which can trigger transient cardiomyopathy. We describe a case of stress-induced cardiomyopathy that occurred in association with an anaphylactic reaction during general anesthesia. CLINICAL FEATURES: A 32-year-old female undergoing laparoscopic enucleation of an ovarian cyst developed a severe anaphylactic reaction after cephalosporin infusion during general anesthesia. Her vital signs responded favourably to immediate resuscitative maneuvers, but cardiovascular collapse reappeared with transient ventricular tachycardia shortly after her transfer to the intensive care unit. ST-segment elevation appeared in electrocardiographic leads V(2)-V(6) and echocardiography showed diffuse regional wall motion abnormalities in the midventricular level. Increased MB fractions of creatine kinase and troponin T levels indicated myocardial necrosis, but cardiac catheterization demonstrated normal coronary arteries. Management was supportive and she was discharged 2 days after the onset of anaphylactic symptoms, without sequelae. A diagnosis of stress-induced cardiomyopathy of a midventricular type following anaphylaxis was made on the basis of the clinical features and the findings of cardiac evaluations. CONCLUSIONS: Transient, reversible left-ventricular dysfunction is a recently recognized phenomenon that may occur in the setting of anaphylactic reactions during the perioperative period.

Effect of various anesthetic induction agents on blood magnesium and calcium concentration.

BACKGROUND: Decrease in blood magnesium and calcium concentration is associated with an increase in the incidence of arrhythmia, especially during the induction period. Therefore, it is important to evaluate the effects of propofol, pentothal sodium, and sevoflurane on calcium and magnesium concentration. METHODS: Thirty-six premedicated, ASA grade I patients were selected and randomly allocated into 3 groups. Six percent sevoflurane inhalation (sevo group), propofol 1.5 mg/kg (propofol group), and 5 mg/kg of pentothal sodium (pento group) were administered for anesthetic induction and anesthetic maintenance was done with end-tidal sevoflurane concentration at 3.5%. Blood sampling was performed during the pre-induction period (pre-induction), just before tracheal intubation (pre-intubation), and 2 min after intubation (post-intubation). pH corrected ionized magnesium and calcium were calculated and analyzed simultaneously. RESULTS: Both total calcium and magnesium concentrations decreased significantly in all groups during the pre-intubation and post-intubation periods compared with the pre-induction period. Ionized calcium only decreased significantly during pre-intubation and post-intubation in the pento group, and did not change throughout the study period in the sevo and propofol groups. Ionized magnesium did not change throughout the study period in any of the groups. pH corrected ionized calcium decreased significantly only at post-intubation in the pento group. CONCLUSIONS: All anesthetic induction agents administered in this study can be used safely in terms of magnesium-associated arrhythmia. However, ionized calcium concentration decreased in the pento group, but all values were within normal limits. This finding indicated that it is safe to use propofol, pentothal sodium, and sevoflurane for anesthetic induction.

Antiallodynic effect of pregabalin in rat models of sympathetically maintained and sympathetic independent neuropathic pain.

Pregabalin binds to the voltage-dependent calcium channel alpha2delta subunit and modulates the release of neurotransmitters, resulting in analgesic effects on neuropathic pain. Neuropathic pain has both sympathetically maintained pain (SMP) and sympathetic independent pain (SIP) components. We studied the antiallodynic effects of pregabalin on tactile allodynia (TA) and cold allodynia (CA) in SMP-and SIP-dominant neuropathic pain models. Allodynia was induced by ligation of the L5 and L6 spinal nerves (SMP model) or by transection of the tibial and sural nerves (SIP model) in rats. For intrathecal drug administration, a PE-10 catheter was implanted through the atlantooccipital membrane to the lumbar enlargement. Pregabalin was administered either intraperitoneally (IP) or intrathecally (IT) and dosed up incrementally until an antiallodynic effect without sedation or motor impairment was apparent. TA was assessed using von Frey filaments, and CA was assessed using acetone drops. IP-administered pregabalin dose-dependently attenuated TA in both models and CA in the SMP model, but not CA in the SIP model. IT-administered pregabalin dose-dependently attenuated both TA and CA in both models. However, the dose response curve of IT-administered pregabalin in SMP was shifted to left from that of SIP and the ED50 of IT-administered pregabalin for CA in SMP was about 900 times less than that in SIP. These findings suggest that pregabalin exerts its antiallodynic effect mainly by acting at the spinal cord, and that IT-administered pregabalin has more potent antiallodynic effects in SMP. The alpha2delta subunit might be less involved in the CA in SIP.

Does the tibial and sural nerve transection model represent sympathetically independent pain?

Neuropathic pain can be divided into sympathetically maintained pain (SMP) and sympathetically independent pain (SIP). Rats with tibial and sural nerve transection (TST) produce neuropathic pain behaviors, including spontaneous pain, tactile allodynia, and cold allodynia. The present study was undertaken to examine whether rats with TST would represent SMP- or SIP-dominant neuropathic pain by lumbar surgical sympathectomy. The TST model was generated by transecting the tibial and sural nerves, leaving the common peroneal nerve intact. Animals were divided into the sympathectomy group and the sham group. For the sympathectomy group, the sympathetic chain was removed bilaterally from L2 to L6 one week after nerve transection. The success of the sympathectomy was verified by measuring skin temperature on the hind paw and by infra red thermography. Tactile allodynia was assessed using von Frey filaments, and cold allodynia was assessed using acetone drops. A majority of the rats exhibited withdrawal behaviors in response to tactile and cold stimulations after nerve stimulation. Neither tactile allodynia nor cold allodynia improved after successful sympathectomy, and there were no differences in the threshold of tactile and cold allodynia between the sympathectomy and sham groups. Tactile allodynia and cold allodynia in the neuropathic pain model of TST are not dependent on the sympathetic nervous system, and this model can be used to investigate SIP syndromes.