Endexpiratory lung volume measurement correlates with the ventilation/perfusion mismatch in lung injured pigs.

BACKGROUND: In acute respiratory respiratory distress syndrome (ARDS) a sustained mismatch of alveolar ventilation and perfusion (VA/Q) impairs the pulmonary gas exchange. Measurement of endexpiratory lung volume (EELV) by multiple breath-nitrogen washout/washin is a non-invasive, bedside technology to assess pulmonary function in mechanically ventilated patients. The present study examines the association between EELV changes and VA/Q distribution and the possibility to predict VA/Q normalization by means of EELV in a porcine model. METHODS: After approval of the state and institutional animal care committee 12 anesthetized pigs were randomized to ARDS either by bronchoalveolar lavage (n = 6) or oleic acid injection (n = 6). EELV, VA/Q ratios by multiple inert gas elimination and ventilation distribution by electrical impedance tomography were assessed at healthy state and at five different positive endexpiratory pressure (PEEP) steps in ARDS (0, 20, 15, 10, 5 cmH2O; each maintained for 30 min). RESULTS: VA/Q, EELV and tidal volume distribution all displayed the PEEP-induced recruitment in ARDS. We found a close correlation between VA/Q < 0.1 (representing shunt and low VA/Q units) and changes in EELV (spearman correlation coefficient -0.79). Logistic regression reveals the potential to predict VA/Q normalization (VA/Q < 0.1 less than 5%) from changes in EELV with an area under the curve of 0.89 with a 95%-CI of 0.81-0.96 in the receiver operating characteristic. Different lung injury models and recruitment characteristics did not influence these findings. CONCLUSION: In a porcine ARDS model EELV measurement depicts PEEP-induced lung recruitment and is strongly associated with normalization of the VA/Q distribution in a model-independent fashion. Determination of EELV could be an intriguing addition in the context of lung protection strategies.

Cyclic PaO2 oscillations assessed in the renal microcirculation: correlation with tidal volume in a porcine model of lung lavage.

BACKGROUND: Oscillations of the arterial partial pressure of oxygen induced by varying shunt fractions occur during cyclic alveolar recruitment within the injured lung. Recently, these were proposed as a pathomechanism that may be relevant for remote organ injury following acute respiratory distress syndrome. This study examines the transmission of oxygen oscillations to the renal tissue and their tidal volume dependency. METHODS: Lung injury was induced by repetitive bronchoalveolar lavage in eight anaesthetized pigs. Cyclic alveolar recruitment was provoked by high tidal volume ventilation. Oscillations of the arterial partial pressure of oxygen were measured in real-time in the macrocirculation by multi-frequency phase fluorimetry and in the renal microcirculation by combined white-light spectrometry and laser-Doppler flowmetry during tidal volume down-titration. RESULTS: Significant respiratory-dependent oxygen oscillations were detected in the macrocirculation and transmitted to the renal microcirculation in a substantial extent. The amplitudes of these oscillations significantly correlate to the applied tidal volume and are minimized during down-titration. CONCLUSIONS: In a porcine model oscillations of the arterial partial pressure of oxygen are induced by cyclic alveolar recruitment and transmitted to the renal microcirculation in a tidal volume-dependent fashion. They might play a role in organ crosstalk and remote organ damage following lung injury.

Inhalation therapy with the synthetic TIP-like peptide AP318 attenuates pulmonary inflammation in a porcine sepsis model.

BACKGROUND: The lectin-like domain of TNF-α can be mimicked by synthetic TIP peptides and represents an innovative pharmacologic option to treat edematous respiratory failure. TIP inhalation was shown to reduce pulmonary edema and improve gas exchange. In addition to its edema resolution effect, TIP peptides may exert some anti-inflammatory properties. The present study therefore investigates the influence of the inhaled TIP peptide AP318 on intrapulmonary inflammatory response in a porcine model of systemic sepsis. METHODS: In a randomized-blinded setting lung injury was induced in 18 pigs by lipopolysaccharide-infusion and a second hit with a short period of ventilator-induced lung stress, followed by a six-hour observation period. The animals received either two inhalations with the peptide (AP318, 2×1 mg kg(-1)) or vehicle. Post-mortem pulmonary expression of inflammatory and mechanotransduction markers were determined by real-time polymerase chain reaction (IL-1ß, IL-6, TNF-α, COX-2, iNOS, amphiregulin, and tenascin-c). Furthermore, regional histopathological lung injury, edema formation and systemic inflammation were quantified. RESULTS: Despite similar systemic response to lipopolysaccharide infusion in both groups, pulmonary inflammation (IL-6, TNF-α, COX-2, tenascin-c) was significantly mitigated by AP318. Furthermore, a Western blot analysis shows a significantly lower of COX-2 protein level. The present sepsis model caused minor lung edema formation and moderate gas exchange impairment. Six hours after onset pathologic scoring showed no improvement, while gas exchange parameters and pulmonary edema formation were similar in the two groups. CONCLUSION: In summary, AP318 significantly attenuated intrapulmonary inflammatory response even without the presence or resolution of severe pulmonary edema in a porcine model of systemic sepsis-associated lung injury. These findings suggest an anti-inflammatory mechanism of the lectin-like domain beyond mere edema reabsorption in endotoxemic lung injury in vivo.

Low tidal volume pressure support versus controlled ventilation in early experimental sepsis in pigs.

BACKGROUND: In moderate acute respiratory distress syndrome (ARDS) several studies support the usage of assisted spontaneous breathing modes. Only limited data, however, focus on the application in systemic sepsis and developing lung injury. The present study examines the effects of immediate initiation of pressure support ventilation (PSV) in a model of sepsis-induced ARDS. METHODS: 18 anesthetized pigs received a two-staged continuous lipopolysaccharide infusion to induce lung injury. The animals were randomly assigned to PSV or volume controlled (VCV) lung protective ventilation (tidal volume each 6 ml kg-1, n = 2x9) over six hours. Gas exchange parameters, hemodynamics, systemic inflammation, and ventilation distribution by multiple inert gas elimination and electrical impedance tomography were assessed. The post mortem analysis included histopathological scoring, wet to dry ratio, and alveolar protein content. RESULTS: Within six hours both groups developed a mild to moderate ARDS with comparable systemic inflammatory response and without signs of improving gas exchange parameters during PSV. The PSV group showed signs of more homogenous ventilation distribution by electrical impedance tomography, but only slightly less hyperinflated lung compartments by multiple inert gas elimination. Post mortem and histopathological assessment yielded no significant intergroup differences. CONCLUSIONS: In a porcine model of sepsis-induced mild ARDS immediate PSV was not superior to VCV. This contrasts with several experimental studies from non-septic mild to moderate ARDS. The present study therefore assumes that not only severity, but also etiology of lung injury considerably influences the response to early initiation of PSV.

TIP peptide inhalation in experimental acute lung injury: effect of repetitive dosage and different synthetic variants.

BACKGROUND: Inhalation of TIP peptides that mimic the lectin-like domain of TNF-α is a novel approach to attenuate pulmonary oedema on the threshold to clinical application. A placebo-controlled porcine model of acute respiratory distress syndrome (ARDS) demonstrated a reduced thermodilution-derived extravascular lung water index (EVLWI) and improved gas exchange through TIP peptide inhalation within three hours. Based on these findings, the present study compares a single versus a repetitive inhalation of a TIP peptide (TIP-A) and two alternate peptide versions (TIP-A, TIP-B). METHODS: Following animal care committee approval ARDS was induced by bronchoalveolar lavage followed by injurious ventilation in 21 anaesthetized pigs. A randomised-blinded three-group setting compared the single-dosed peptide variants TIP-A and TIP-B as well as single versus repetitive inhalation of TIP-A (n = 7 per group). Over two three-hour intervals parameters of gas exchange, transpulmonary thermodilution, calculated alveolar fluid clearance, and ventilation/perfusion-distribution were assessed. Post-mortem measurements included pulmonary wet/dry ratio and haemorrhage/congestion scoring. RESULTS: The repetitive TIP-A inhalation led to a significantly lower wet/dry ratio than a single dose and a small but significantly lower EVLWI. However, EVLWI changes over time and the derived alveolar fluid clearance did not differ significantly. The comparison of TIP-A and B showed no relevant differences. Gas exchange and ventilation/perfusion-distribution significantly improved in all groups without intergroup differences. No differences were found in haemorrhage/congestion scoring. CONCLUSIONS: In comparison to a single application the repetitive inhalation of a TIP peptide in three-hour intervals may lead to a small additional reduction the lung water content. Two alternate TIP peptide versions showed interchangeable characteristics.

Intervertebral disc injury triggers neurogenic inflammation of adjacent healthy discs.

BACKGROUND CONTEXT: Intervertebral disc degeneration is common and may play an important role in low back pain, but it is not well-understood. Previous studies have shown that the outer layer of the annulus fibrosus of a healthy disc is innervated by nociceptive nerve fibers. In the process of disc degeneration, it can grow into the inner annulus fibrosus or nucleus pulposus and release neuropeptides. Disc degeneration is associated with inflammation that produces inflammatory factors and potentiates nociceptor sensitization. Subsequently neurogenic inflammation is induced by neuropeptide release from activated primary afferent terminals. Because the innervation of a lumbar disc comes from multisegmental dorsal root ganglion neurons, does neurogenic inflammation in a degenerative disc initiate neurogenic inflammation in neighboring healthy discs by antidromic activity? PURPOSE: This study was based on animal experiments in Sprague-Dawley rats to investigate the role of neurogenic inflammation in adjacent healthy disc degeneration induced by disc injury. STUDY DESIGN: This was an experimental study. METHODS: Seventy-five 12-week-old, male Sprague-Dawley rats were allocated to 3 groups (sham group, disc injury group and disc injury+TrkA antagonist group). The disc injury group was punctured in the tail disc between the eighth and ninth coccygeal vertebrae (Co8-9) to establish an animal model of tail intervertebral disc degeneration. The sham group underwent only skin puncture and the disc injury+TrkA antagonist group was intraperitoneally injected with GW441756 two days before disc puncture. The outcome measure included quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. RESULTS: Disc injury induced an increase in aggrecan, NGF, TrkA, CGRP, SP, IL-1ß, and IL-6 mRNA levels in the injured (Co8-9) and adjacent discs (Co7-8), which reached a peak on day 1, then gradually decreased, and returned to normal on day 14. After intraperitoneal injection of GW441756 prior to puncture, the mRNA levels of the above indicators were down-regulated in Co7-8 and Co8-9 intervertebral discs on the 1st and 7th days. The protein content of the above indicators in Co7-8 and Co8-9 intervertebral discs showed roughly the same trend as mRNA levels. CONCLUSIONS: Degeneration of one disc can induce neurogenic inflammation of adjacent healthy discs in a rat model. CLINICAL SIGNIFICANCE: This model supports a key role of neurogenic inflammation in disc degeneration, and may play a role in the experience of low back pain.

Hyaluronic acid plasma levels during high versus low tidal volume ventilation in a porcine sepsis model.

BACKGROUND: Shedding of the endothelial glycocalyx can be observed regularly during sepsis. Moreover, sepsis may be associated with acute respiratory distress syndrome (ARDS), which requires lung protective ventilation with the two cornerstones of application of low tidal volume and positive end-expiratory pressure. This study investigated the effect of a lung protective ventilation on the integrity of the endothelial glycocalyx in comparison to a high tidal volume ventilation mode in a porcine model of sepsis-induced ARDS. METHODS: After approval by the State and Institutional Animal Care Committee, 20 male pigs were anesthetized and received a continuous infusion of lipopolysaccharide to induce septic shock. The animals were randomly assigned to either low tidal volume ventilation, high tidal volume ventilation, or no-LPS-group groups and observed for 6 h. In addition to the gas exchange parameters and hematologic analyses, the serum hyaluronic acid concentrations were determined from central venous blood and from pre- and postpulmonary and pre- and postcerebral circulation. Post-mortem analysis included histopathological evaluation and determination of the pulmonary and cerebral wet-to-dry ratios. RESULTS: Both sepsis groups developed ARDS within 6 h of the experiment and showed significantly increased serum levels of hyaluronic acid in comparison to the no-LPS-group. No significant differences in the hyaluronic acid concentrations were detected before and after pulmonary and cerebral circulation. There was also no significant difference in the serum hyaluronic acid concentrations between the two sepsis groups. Post-mortem analysis showed no significant difference between the two sepsis groups. CONCLUSION: In a porcine model of septic shock and ARDS, the serum hyaluronic acid levels were significantly elevated in both sepsis groups in comparison to the no-LPS-group. Intergroup comparison between lung protective ventilated and high tidal ventilated animals revealed no significant differences in the serum hyaluronic acid levels.

Cervical intervertebral disc degeneration and dizziness.

Clinical studies have found that patients withcervical degenerative disease are usually accompanied by dizziness. Anterior cervical surgery can eliminate not only chronic neck pain, cervical radiculopathy or myelopathy, but also dizziness. Immunohistochemical studies show that a large number of mechanoreceptors, especially Ruffini corpuscles, are present in degenerated cervical discs. The available evidence suggests a key role of Ruffini corpuscles in the pathogenesis of dizziness caused by cervical degenerative disease (i.e. cervical discogenic dizziness). Disc degeneration is characterized by an elevation of inflammatory cytokines, which stimulates the mechanoreceptors in degenerated discs and results in peripheral sensitization. Abnormal cervical proprioceptive inputs from the mechanoreceptors are transmitted to the central nervous system, resulting in sensory mismatches with vestibular and visual information and leads to dizziness. In addition, neck pain caused by cervical disc degeneration can play a key role in cervical discogenic dizziness by increasing the sensitivity of muscle spindles. Like cervical discogenic pain, the diagnosis of cervical discogenic dizziness can be challenging and can be made only after other potential causes of dizziness have been ruled out. Conservative treatment is effective for the majority of patients. Existing basic and clinical studies have shown that cervical intervertebral disc degeneration can lead to dizziness.

Cervical Proprioception Impairment in Neck Pain-Pathophysiology, Clinical Evaluation, and Management: A Narrative Review.

Neck pain is very common, but most of the causes are unknown, making diagnosis and treatment extremely challenging. Current studies have found that one of the main problems in patients with neck pain is the impairment of cervical proprioception, which subsequently leads to cervical sensorimotor control disturbances. Cervical spine has a very delicate proprioceptive system that plays a crucial role in controlling posture and balance. Cervical proprioceptive impairment in neck pain occurs through a variety of mechanisms. Experimental neck muscle pain induced by injection of hypertonic saline results in inhibition of the activation of painful muscle; chronic neck pain causes structural and functional impairment of cervical muscles; excessive activation of mechanoreceptors in degenerative cervical discs and facet joints produces a large number of erroneous sensory signals. Clinical examinations to assess the link between structural pathology and neck pain have been unsuccessful, opening the way for the development of function-based tests. To date, eight neck sensorimotor control tests have been reported to evaluate patients with chronic neck pain. Although some tests may involve different subsystems (such as oculomotor system and vestibular system), all tests measure sensorimotor control in the neck, and the most commonly used is cervical joint position error (JPE) test. Current studies support the effectiveness of exercises targeting different aspects of sensorimotor function, in particular retraining aimed at improving cervical proprioception and muscle coordination. Based on the available evidence, it is recommended that patients with neck pain should be assessed and managed for cervical proprioceptive impairment and sensorimotor control disturbances.

Contributions of aversive environmental stress to migraine chronification: Research update of migraine pathophysiology.

Clinical studies have suggested that internal and/or external aversive cues may produce a negative affective-motivational component whereby maladaptive responses (plasticity) of dural afferent neurons are initiated contributing to migraine chronification. However, pathophysiological processes and neural circuitry involved in aversion (unpleasantness)-producing migraine chronification are still evolving. An interdisciplinary team conducted this narrative review aimed at reviewing neuronal plasticity for developing migraine chronicity and its relevant neurocircuits and providing the most cutting-edge information on neuronal mechanisms involved in the processing of affective aspects of pain and the role of unpleasantness evoked by internal and/or external cues in facilitating the chronification process of migraine headache. Thus, information presented in this review promotes the understanding of the pathophysiology of chronic migraine and contribution of unpleasantness (aversion) to migraine chronification. We hope that it will bring clinicians' attention to how the maladaptive neuroplasticity of the emotion brain in the aversive environment produces a significant impact on the chronification of migraine headache, which will in turn lead to new therapeutic strategies for this type of pain.

Levosimendan increases brain tissue oxygen levels after cardiopulmonary resuscitation independent of cardiac function and cerebral perfusion.

Prompt reperfusion is important to rescue ischemic tissue; however, the process itself presents a key pathomechanism that contributes to a poor outcome following cardiac arrest. Experimental data have suggested the use of levosimendan to limit ischemia-reperfusion injury by improving cerebral microcirculation. However, recent studies have questioned this effect. The present study aimed to investigate the influence on hemodynamic parameters, cerebral perfusion and oxygenation following cardiac arrest by ventricular fibrillation in juvenile male pigs. Following the return of spontaneous circulation (ROSC), animals were randomly assigned to levosimendan (12 µg/kg, followed by 0.3 µg/kg/min) or vehicle treatment for 6 h. Levosimendan-treated animals showed significantly higher brain PbtO2 levels. This effect was not accompanied by changes in cardiac output, preload and afterload, arterial blood pressure, or cerebral microcirculation indicating a local effect. Cerebral oxygenation is key to minimizing damage, and thus, current concepts are aimed at improving impaired cardiac output or cerebral perfusion. In the present study, we showed that NIRS does not reliably detect low PbtO2 levels and that levosimendan increases brain oxygen content. Thus, levosimendan may present a promising therapeutic approach to rescue brain tissue at risk following cardiac arrest or ischemic events such as stroke or traumatic brain injury.

Expert consensus of the Chinese Association for the Study of Pain on ion channel drugs for neuropathic pain.

Neuropathic pain (NPP) is a kind of pain caused by disease or damage impacting the somatosensory system. Ion channel drugs are the main treatment for NPP; however, their irregular usage leads to unsatisfactory pain relief. To regulate the treatment of NPP with ion channel drugs in clinical practice, the Chinese Association for the Study of Pain organized first-line pain management experts from China to write an expert consensus as the reference for the use of ion channels drugs . Here, we reviewed the mechanism and characteristics of sodium and calcium channel drugs, and developed recommendations for the therapeutic principles and clinical practice for carbamazepine, oxcarbazepine, lidocaine, bulleyaconitine A, pregabalin, and gabapentin. We hope this guideline provides guidance to clinicians and patients on the use of ion channel drugs for the management of NPP.

Expert consensus of Chinese Association for the Study of Pain on the radiofrequency therapy technology in the Department of Pain.

On the basis of continuous improvement in recent years, radiofrequency therapy technology has been widely developed, and has become an effective method for the treatment of various intractable pain. Radiofrequency therapy is a technique that uses special equipment and puncture needles to output ultra-high frequency radio waves and accurately act on local tissues. In order to standardize the application of radiofrequency technology in the treatment of painful diseases, Chinese Association for the Study of Pain (CASP) has developed a consensus proposed by many domestic experts and scholars.

IL-17 contributed to the neuropathic pain following peripheral nerve injury by promoting astrocyte proliferation and secretion of proinflammatory cytokines.

Central neuroinflammation is important in the pathophysiological processes of neuropathic pain following peripheral nerve injury. Recently, interleukin-17 (IL-17) has been detected in different inflammatory conditions of the central nervous system and contributes to neuropathic pain associated with multiple sclerosis, experimental autoimmune encephalomyelitis. The present study, based on the rat model of spinal nerve ligation, analyzed the infiltration of cluster of differentiation (CD)4+ T cells and the expression of IL­17 in the spinal cord during the maintenance phase of neuropathic pain, and investigated central inflammatory reaction and astrocyte activation. The results demonstrated that the infiltrated CD4+ T cells in the spinal cord increased in the rat model of spinal nerve ligation, and immunofluorescence staining demonstrated that the CD4+/IL­17+ cells were located at superficial laminae of spinal dorsal horn. This was accompanied by significant upregulation of IL­17. Furthermore, the mRNA expression levels of IL­1ß and IL­6 were also significantly enhanced in model rats compared with the sham and control groups in the spinal dorsal horn. In vitro, the proliferation ability and secretion of proinflammatory cytokines notably increased in the IL­17­stimulated astrocytes. Results from the present study indicate that IL­17 may contribute to neuropathic pain by promoting the proliferation of astrocytes and secretion of proinflammatory cytokines in spinal nerve ligation­induced neuropathic pain.