Endocannabinoid regulation of spinal nociceptive processing in a model of neuropathic pain.

Models of neuropathic pain are associated with elevated spinal levels of endocannabinoids (ECs) and altered expression of cannabinoid receptors on primary sensory afferents and post-synaptic cells in the spinal cord. We investigated the impact of these changes on the spinal processing of sensory inputs in a model of neuropathic pain. Extracellular single-unit recordings of spinal neurones were made in anaesthetized neuropathic and sham-operated rats. The effects of spinal administration of the cannabinoid CB(1) receptor antagonist N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251) and the cannabinoid receptor type 2 (CB(2)) receptor antagonist N-[(1S)-endo-1,3,3-trimethylbicycloheptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528) on mechanically-evoked responses of spinal neurones were determined. The effects of spinal administration of (5Z,8Z11Z,14Z)-N-(3-furanylmethyl)-5,8,11,14-eicosatetraenamide (UCM707), which binds to CB(2) receptors and alters transport of ECs, on evoked responses of spinal neurones and spinal levels of ECs were also determined. The cannabinoid CB(1) receptor antagonist AM251, but not the CB(2) receptor antagonist, significantly facilitated 10-g-evoked responses of spinal neurones in neuropathic, but not sham-operated, rats. Spinal administration of UCM707 did not alter spinal levels of ECs but did significantly inhibit mechanically-evoked responses of neurones in neuropathic, but not sham-operated, rats. Pharmacological studies indicated that the selective inhibitory effects of spinal UCM707 in neuropathic rats were mediated by activation of spinal CB(2) receptors, as well as a contribution from transient receptor potential vanilloid 1 (TRPV1) channels. This work demonstrates that changes in the EC receptor system in the spinal cord of neuropathic rats influence the processing of sensory inputs, in particular low-weight inputs that drive allodynia, and indicates novel effects of drugs acting via multiple elements of this receptor system.

Minocycline treatment inhibits microglial activation and alters spinal levels of endocannabinoids in a rat model of neuropathic pain.

Activation of spinal microglia contributes to aberrant pain responses associated with neuropathic pain states. Endocannabinoids (ECs) are present in the spinal cord, and inhibit nociceptive processing; levels of ECs may be altered by microglia which modulate the turnover of endocannabinoids in vitro. Here, we investigate the effect of minocycline, an inhibitor of activated microglia, on levels of the endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG), and the related compound N-palmitoylethanolamine (PEA), in neuropathic spinal cord. Selective spinal nerve ligation (SNL) in rats resulted in mechanical allodynia and the presence of activated microglia in the ipsilateral spinal cord. Chronic daily treatment with minocycline (30 mg/kg, ip for 14 days) significantly reduced the development of mechanical allodynia at days 5, 10 and 14 post-SNL surgery, compared to vehicle-treated SNL rats (P < 0.001). Minocycline treatment also significantly attenuated OX-42 immunoreactivity, a marker of activated microglia, in the ipsilateral (P < 0.001) and contralateral (P < 0.01) spinal cord of SNL rats, compared to vehicle controls. Minocycline treatment significantly (P < 0.01) decreased levels of 2-AG and significantly (P < 0.01) increased levels of PEA in the ipsilateral spinal cord of SNL rats, compared to the contralateral spinal cord. Thus, activation of microglia affects spinal levels of endocannabinoids and related compounds in neuropathic pain states.

Inhibition of fatty acid amide hydrolase and cyclooxygenase-2 increases levels of endocannabinoid related molecules and produces analgesia via peroxisome proliferator-activated receptor-alpha in a model of inflammatory pain.

The antinociceptive effects of the endocannabinoids (ECs) are enhanced by inhibiting catabolic enzymes such as fatty acid amide hydrolase (FAAH). The physiological relevance of the metabolism of ECs by other pathways, such as cyclooxygenase-2 (COX2) is less clear. To address this question we compared the effects of local inhibition of FAAH versus COX2 (URB597 and nimesulide, respectively) on inflammatory hyperalgesia and levels of endocannabinoids and related molecules in the hindpaw. Inflammatory hyperalgesia was measured following intraplantar injection of carrageenan. Effects of intraplantar injection of URB597 (25 microg and 100 microg) or nimesulide (50 microg) on hyperalgesia and hindpaw levels of anandamide (AEA), 2-arachidonoylglycerol (2AG) and N-palmitoylethanolamine (PEA) were determined. Although both doses of URB597 increased levels of AEA and 2AG in the carrageenan inflamed hindpaw, only the lower dose of URB597 attenuated hyperalgesia (P<0.05). Nimesulide attenuated both hyperalgesia and hindpaw oedema (P<0.001, P<0.01, respectively) and increased levels of PEA (P<0.05) in the hindpaw. Since both AEA and PEA are ligands for peroxisome proliferator-activated receptor-alpha (PPARalpha), the effects of the PPARalpha antagonist GW6471 on nimesulide- and URB597-mediated effects were studied. GW6471, but not a PPARgamma antagonist, blocked the inhibitory effects of nimesulide and URB597 on hyperalgesia. Our data suggest that both COX2 and FAAH play a role in the metabolism of endocannabinoids and related molecules. The finding that PPARalpha antagonism blocked the inhibitory effects of nimesulide and URB597 suggests that PPARalpha contributes to their antinociceptive effects in the carrageenan model of inflammatory hyperalgesia.

Better living through chemistry, constant monitoring, and prompt interventions: 26 years on home parenteral nutrition without major complications.

OBJECTIVE: We discuss 26 y of home parenteral nutrition (HPN) in an otherwise healthy patient with severe short bowel syndrome demonstrating a decrease in life-threatening complications after various management changes. METHODS: The patient is a 41-y-old male with a midgut volvulus from malrotation who developed short bowel syndrome and has been HPN dependent since the age of 15 y. His surgical and nutritional data were collected retrospectively and prospectively and included nutritional history, anthropometric parameters, laboratory results, activity levels and types, and treatments for complications. His entire HPN course has been prospectively followed. RESULTS: Since becoming HPN dependent, the patient's energy intake range has been 20-45 kcal.kg(-1).d(-1), with 0.8-1.6 g of protein.kg(-1).d(-1). He receives HPN with electrolytes, multivitamins, and trace elements nightly and his intravenous fat emulsion ranges from one to seven times per week. Adjustments to magnesium, iron, zinc, selenium, vitamin E, and carnitine are often required. During his first years of HPN, he had six episodes of catheter-related sepsis and two central venous catheter occlusions. The current central venous catheter has been in place for >13 y without infection or replacement. He developed mild osteopenia but has maintained an active lifestyle without fractures. In the second and third decades of HPN, episodes of hepatic dysfunction occurred, with improvement or resolution using various interventions including oral fish oil. CONCLUSION: This case illustrates the successful management of a life-long HPN-dependent patient in whom PN complications have been minimized, including a very recent occurrence of parenteral nutrition-associated cholestasis.

Standardized Competencies for Parenteral Nutrition Administration: The ASPEN Model.

Parenteral nutrition (PN) is a highly complex medication and its provision can be prone to a variety of errors. Safe administration of this therapy requires that the competency of clinicians, particularly nurses, be demonstrated using a standardized process. In this document, a standardized model for PN administration competency is proposed based on a competency framework, the ASPEN-published interdisciplinary core competencies, discipline-specific standards of practice, safe practice recommendations, and clinical guidelines. ASPEN recognizes that all healthcare institutions may not currently meet the aspirational goals of this document. This framework will guide institutions and agencies in developing tools and procedures and maintaining competency of staff members around safe PN administration. The ASPEN Board of Directors has approved this document.

Analgesic effects of fatty acid amide hydrolase inhibition in a rat model of neuropathic pain.

Cannabinoid-based medicines have therapeutic potential for the treatment of pain. Augmentation of levels of endocannabinoids with inhibitors of fatty acid amide hydrolase (FAAH) is analgesic in models of acute and inflammatory pain states. The aim of this study was to determine whether local inhibition of FAAH alters nociceptive responses of spinal neurons in the spinal nerve ligation model of neuropathic pain. Electrophysiological studies were performed 14-18 d after spinal nerve ligation or sham surgery, and the effects of the FAAH inhibitor cyclohexylcarbamic acid 3-carbamoyl biphenyl-3-yl ester (URB597) on mechanically evoked responses of spinal neurons and levels of endocannabinoids were determined. Intraplantar URB597 (25 microg in 50 microl) significantly (p < 0.01) attenuated mechanically evoked responses of spinal neurons in sham-operated rats. Effects of URB597 were blocked by the cannabinoid 1 receptor (CB1) antagonist AM251 [N-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide] (30 microg in 50 microl) and the opioid receptor antagonist naloxone. URB597 treatment increased levels of anandamide, 2-arachidonyl glycerol, and oleoyl ethanolamide in the ipsilateral hindpaw of sham-operated rats. Intraplantar URB597 (25 microg in 50 microl) did not, however, alter mechanically evoked responses of spinal neurons in spinal nerve ligated (SNL) rats or hindpaw levels of endocannabinoids. Intraplantar injection of a higher dose of URB597 (100 microg in 50 microl) significantly (p < 0.05) attenuated evoked responses of spinal neurons in SNL rats but did not alter hindpaw levels of endocannabinoids. Spinal administration of URB597 attenuated evoked responses of spinal neurons and elevated levels of endocannabinoids in sham-operated and SNL rats. These data suggest that peripheral FAAH activity may be altered or that alternative pathways of metabolism have greater importance in SNL rats.

Effectiveness of a clinical practice guideline for parenteral nutrition: a 5-year follow-up study in a pediatric teaching hospital.

OBJECTIVE: To determine the effectiveness of a clinical practice guideline (CPG) on the use of parenteral nutrition (PN) at a tertiary care pediatric hospital. METHODS: Review of prospectively collected data on hospital-wide PN use 2 years before and 5 years after the establishment of the CPG. Effectiveness of the CPG was measured as the percentage of PN courses lasting fewer than 5 days and the number of PN starts per 1000 patient days. RESULTS: During the study period, 5745 PN courses were administered. The mean (SD) number of PN starts per 1000 inpatient days was 8.86 (0.78) before the CPG and 9.54 (2.49) afterwards (p = .28). The percentage courses of PN lasting for fewer than 5 days declined from 26.3% before the CPG to 18.4% afterwards (p < .0001). A multivariate model confirmed that the rate of short-term PN starts declined after the CPG was issued. The mean (SD) number of PN courses shorter than 5 days in the 2 years before the CPG was 2.33 (0.42) per 1000 patient days versus 1.75 (0.45) in the 5 years after the CPG was instituted (p = .005), which is a 25% decline. The services with the highest volume of PN use showed the most significant decreases in short-term PN use. A cost savings to the hospital of more than $50,000 may have been realized. CONCLUSIONS: In a large pediatric tertiary care hospital, a CPG was successfully deployed. CPGs can favorably affect the use rates and costs of parenteral nutrition.

A Comparison of the α2/3/5 Selective Positive Allosteric Modulators L-838,417 and TPA023 in Preclinical Models of Inflammatory and Neuropathic Pain.

GABA(A) receptors containing α2/3 subunits are current targets in the battle to develop new pain medications, as they are expressed in the spinal cord where increasing inhibitory drive should result in analgesia. However, this approach is prone to a range of side effects including sedation, cognitive impairment, and abuse as a consequence of the widespread influence of GABA. The ability to make subtype selective low-efficacy benzodiazepine compounds, which potentiate the action of GABA at specific α subunits, has the potential to reduce this side effect profile. In this study, we have investigated the effects of the medium-efficacy positive allosteric modulator (PAM) L-838,417 and the low-efficacy PAM TPA023 in a number of preclinical inflammatory and neuropathic pain models. We conclude that either the higher level of efficacy at α2/3 or efficacy at α5 is required for compounds to have a significant analgesic effect in a range of models, and, therefore, although the side-effect profile of compounds can be reduced compared to typical benzodiazepines, it is unlikely that it can be completely eliminated.

Efficacy of ethanol locks in reducing central venous catheter infections in pediatric patients with intestinal failure.

PURPOSE: We sought to determine whether a regimen of 70% ethanol locks could reduce the rate of central venous catheter (CVC) infections in parenteral nutrition-dependent children with intestinal failure. METHODS: We performed a retrospective review of 23 parenteral nutrition-dependent children in our multidisciplinary intestinal rehabilitation clinic who started ethanol lock therapy between September 2007 and June 2009. The treatment regimen consisted of a 70% ethanol lock instilled 3 times per week in each catheter lumen. The rate of CVC infections before and after initiation of ethanol lock therapy was compared using the Wilcoxon signed ranks test with significance set at P < .05. RESULTS: The most common diagnoses leading to intestinal failure were necrotizing enterocolitis (26.1%), gastroschisis (21.7%), and intestinal atresia (14.3%). Ethanol locks were well tolerated with no reported adverse side effects. The infection rate decreased from 9.9 per 1000 catheter days prior to initiation of ethanol locks to 2.1 per 1000 catheter days during therapy (P = .03). CONCLUSIONS: A regimen of ethanol lock therapy administered three days per week appears to be a safe and effective means of reducing the rate of CVC infections in parenteral nutrition-dependent children with intestinal failure.

Characterisation of the cannabinoid receptor system in synovial tissue and fluid in patients with osteoarthritis and rheumatoid arthritis.

INTRODUCTION: Cannabis-based medicines have a number of therapeutic indications, including anti-inflammatory and analgesic effects. The endocannabinoid receptor system, including the cannabinoid receptor 1 (CB1) and receptor 2 (CB2) and the endocannabinoids, are implicated in a wide range of physiological and pathophysiological processes. Pre-clinical and clinical studies have demonstrated that cannabis-based drugs have therapeutic potential in inflammatory diseases, including rheumatoid arthritis (RA) and multiple sclerosis. The aim of this study was to determine whether the key elements of the endocannabinoid signalling system, which produces immunosuppression and analgesia, are expressed in the synovia of patients with osteoarthritis (OA) or RA. METHODS: Thirty-two OA and 13 RA patients undergoing total knee arthroplasty were included in this study. Clinical staging was conducted from x-rays scored according to Kellgren-Lawrence and Larsen scales, and synovitis of synovial biopsies was graded. Endocannabinoid levels were quantified in synovial fluid by liquid chromatography-mass spectrometry. The expression of CB1 and CB2 protein and RNA in synovial biopsies was investigated. Functional activity of these receptors was determined with mitogen-activated protein kinase assays. To assess the impact of OA and RA on this receptor system, levels of endocannabinoids in the synovial fluid of patients and non-inflamed healthy volunteers were compared. The activity of fatty acid amide hydrolase (FAAH), the predominant catabolic endocannabinoid enzyme, was measured in synovium. RESULTS: CB1 and CB2 protein and RNA were present in the synovia of OA and RA patients. Cannabinoid receptor stimulation of fibroblast-like cells from OA and RA patients produced a time-dependent phosphorylation of extracellular signal-regulated kinase (ERK)-1 and ERK-2 which was significantly blocked by the CB1 antagonist SR141716A. The endocannabinoids anandamide (AEA) and 2-arachidonyl glycerol (2-AG) were identified in the synovial fluid of OA and RA patients. However, neither AEA nor 2-AG was detected in synovial fluid from normal volunteers. FAAH was active in the synovia of OA and RA patients and was sensitive to inhibition by URB597 (3'-(aminocarbonyl) [1,1'-biphenyl]-3-yl)-cyclohexylcarbamate). CONCLUSION: Our data predict that the cannabinoid receptor system present in the synovium may be an important therapeutic target for the treatment of pain and inflammation associated with OA and RA.

Quantitative profiling of endocannabinoids and related compounds in rat brain using liquid chromatography-tandem electrospray ionization mass spectrometry.

A sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method is described for the simultaneous identification and quantification of eight endocannabinoid (EC) or related "entourage" compounds in rat brain tissue. Analytes were extracted and purified from rat brain tissue using an ethyl acetate/hexane solvent extraction, followed by a solid phase extraction (SPE) protocol. Chromatographic separation was achieved using a gradient elution, with a mobile phase of acetonitrile, formic acid, and ammonium acetate, at pH 3.6. A Thermo Hypersil C8 HyPurity Advance column (100x2.1 mm i.d., 3 microm) was used with a flow rate of 0.3 ml/min). Anandamide (AEA), 2-arachidonyl glycerol (2-AG), 2-arachidonylglyceryl ether (noladin ether), O-arachidonyl ethanolamide (virodhamine), 2-linoleoyl glycerol (2-LG), arachidonyl glycine, oleoyl ethanolamide (OEA), and palmitoyl ethanolamide (PEA) were quantified by positive ion tandem electrospray ionization mass spectrometry. Internal standards were deuterated AEA, deuterated 2-AG, and heptadecanoyl ethanolamide (HEA). Linearity was proven over the range of 25 fmol to 250 pmol, with a limit of detection of 25 fmol on column for all analytes except 2-AG, noladin ether, and 2-LG (250 fmol). This corresponded to a limit of quantification in biological tissue of 10 pmol/g for all analytes except 2-AG (100 pmol/g). Intra- and interday precision in biological tissue was routinely approximately 20% or lower, and accuracy was between 65% and 155%. This method was used to quantitatively profile regional differences in nine discrete rat brain regions for AEA, 2-AG, 2-LG, OEA, PEA, noladin ether, virodhamine, and arachidonyl glycine.

An evidence-based approach to nasogastric tube management: special considerations.

Although there have been helpful literature reviews on pediatric nasogastric (NG) tube management, there is a lack of evidence with regards to special circumstances, such as at-risk patients with altered neurological status or developmental disabilities. At our hospital, an interdisciplinary Enteral Feeding Task Force was created to address the special needs and concerns of complex pediatric patients. We carefully weighed the evidence from the literature, incidents at our hospital and other children's hospitals, and a synthesis of expert opinion. This article describes our evidence-based process of policy revision, and it includes excerpts from our revised NG tube management policy.

The role of enteral nutrition in the reversal of parenteral nutrition-associated liver dysfunction in infants.

BACKGROUND: Liver dysfunction in children dependent on parenteral nutrition (PN) is well established, and the extent of hyperbilirubinemia has been shown to correlate with morbidity and mortality. The aim of this study was to assess whether increasing provisions of enteral nutrition can improve PN-associated hyperbilirubinemia over time. METHODS: A retrospective review was conducted on infants in our institution's Short Bowel Syndrome Clinic from 1999 to 2004. Inclusion criteria included PN duration more than 1 month, serum direct bilirubin more than 3 mg/dL while on PN, and tolerance of full enteral nutrition with eventual discontinuation of PN. Paired t tests were used for statistical analyses. RESULTS: Twelve infants were identified with a PN duration of 5 +/- 1 months. Five patients underwent liver biopsy while on PN, and histological evidence of cholestasis was found on all specimens. Peak total and direct bilirubin levels were 10.5 +/- 1.9 and 7.0 +/- 1.6 mg/dL, respectively, and occurred at time of PN discontinuation. Only 2 patients had improvement in serum bilirubin levels before initiation of full enteral nutrition. After initiation of full enteral nutrition and discontinuation of PN, all patients achieved permanent normalization of bilirubin levels by 4 months (P < .05) after a 1-month plateau phase. Alkaline phosphatase levels approached reference range within this time but were not significant. CONCLUSION: These data demonstrate for the first time that although PN-dependent infants can achieve normalization of marked hyperbilirubinemia with enteral nutrition, the improvement in liver function usually begins only after full enteral nutrition is tolerated and PN is withdrawn. These findings support the aggressive weaning of PN to enteral nutrition in infants with short bowel syndrome.