Zenaide M.N. Quezado

Subanesthetic ketamine infusions for the treatment of children and adolescents with chronic pain: a longitudinal study

BackgroundChronic pain is common in children and adolescents and is often associated with severe functional disability and mood disorders. The pharmacological treatment of chronic pain in children and adolescents can be challenging, ineffective, and is mostly based on expert opinions and consensus. Ketamine, an N-methyl-D-aspartate receptor antagonist, has been used as an adjuvant for treatment of adult chronic pain and has been shown, in some instances, to improve pain and decrease opioid-requirement. We examined the effects of subanesthetic ketamine infusions on pain intensity and opioid use in children and adolescents with chronic pain syndromes treated in an outpatient setting.MethodsLongitudinal cohort study of consecutive pediatric patients treated with subanesthetic ketamine infusions in a tertiary outpatient center. Outcome measurements included self-reported pain scores (numeric rating scale) and morphine-equivalent intake.ResultsOver a 15-month period, 63 children and adolescents (median age 15, interquartile range 12–17 years) with chronic pain received 277 ketamine infusions. Intravenous administration of subanesthetic doses of ketamine to children and adolescents on an outpatient basis was safe and not associated with psychotropic effects or hemodynamic perturbations. Overall, ketamine significantly reduced pain intensity (p <0.001) and yielded greater pain reduction in patients with complex regional pain syndrome (CRPS) than in patients with other chronic pain syndromes (pu2009=u20090.029). Ketamine-associated reductions in pain scores were the largest in postural orthostatic tachycardia syndrome (POTS) and trauma patients and the smallest in patients with chronic headache (pu2009=u20090.007). In 37xa0% of infusions, patients had a greater than 20xa0% reduction in pain score. Conversely, ketamine infusions did not change overall morphine-equivalent intake (pu2009=u20090.3).ConclusionsThese data suggest that subanesthetic ketamine infusion is feasible in an outpatient setting and may benefit children and adolescents with chronic pain. Further, patients with CRPS, POTS, and a history of trauma-related chronic pain are more likely to benefit from this therapeutic modality.

Modulation of social deficits and repetitive behaviors in a mouse model of autism: the role of the nicotinic cholinergic system

RationaleAccumulating evidence implicates the nicotinic cholinergic system in autism spectrum disorder (ASD) pathobiology. Neuropathologic studies suggest that nicotinic acetylcholine (ACh) receptor (nAChR) subtypes are altered in brain of autistic individuals. In addition, strategies that increase ACh, the neurotransmitter for nicotinic and muscarinic receptors, appear to improve cognitive deficits in neuropsychiatric disorders and ASD.ObjectiveThe aim of this study is to examine the role of the nicotinic cholinergic system on social and repetitive behavior abnormalities and exploratory physical activity in a well-studied model of autism, the BTBR T+Itpr3tf/J (BTBR) mouse.MethodsUsing a protocol known to up-regulate expression of brain nAChR subtypes, we measured behavior outcomes before and after BTBR and C57BL/6J (B6) mice were treated (4xa0weeks) with vehicle or nicotine (50, 100, 200, or 400xa0μg/ml).ResultsIncreasing nicotine doses were associated with decreases in water intake, increases in plasma cotinine levels, and at the higher dose (400xa0μg/ml) with weight loss in BTBR mice. At lower (50, 100xa0μg/ml) but not higher (200, 400xa0μg/ml) doses, nicotine increased social interactions in BTBR and B6 mice and at higher, but not lower doses, it decreased repetitive behavior in BTBR. In the open-field test, nicotine at 200 and 400xa0μg/ml, but not 100xa0μg/ml compared with vehicle, decreased overall physical activity in BTBR mice.ConclusionsThese findings support the hypotheses that the nicotinic cholinergic system modulates social and repetitive behaviors and may be a therapeutic target to treat behavior deficits in ASD. Further, the BTBR mouse may be valuable for investigations of the role of nAChRs in social deficits and repetitive behavior.

Rapamycin increases fetal hemoglobin and ameliorates the nociception phenotype in sickle cell mice

Fetal hemoglobin-inducing therapies are disease-modifying and ameliorate the pain phenotype in sickle cell disease (SCD). Rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, increases HbF in erythroid precursor cells in vitro. We hypothesized that rapamycin would increase HbF levels and improve nociception phenotype in SCD mice. We used sine-wave electrical stimulation to examine nocifensive phenotype and evaluate myelinated [2000Hz (Aβ-fiber) and 250Hz (Aδ-fiber)] and unmyelinated (5Hz C-fibers)] sensory fiber function. Rapamycin significantly increased γ-globin mRNA and HbF levels [+2.3% (0.7, 3.9), mean increase (95% confidence interval, CI), p=0.006]. In homozygous (sickling) mice, long- (16 weeks), but not short-term (6 weeks), rapamycin treatment increased 2000Hz and 250Hz current thresholds in a pattern that varied according to sex. In male, but not female mice, rapamycin (compared with vehicle) was associated with increases in 2000Hz [21Units (7, 35), mean difference (95% CI), p=0.009 for sex∗treatment interaction] and 250Hz [9Units (1, 16), p=0.01] current thresholds. In rapamycin-treated homozygotes, HbF levels directly correlated with myelinated [2000Hz(Aβ-fiber, r=0.58, p=0.01) and 250Hz(Aδ-fiber, r=0.6, p=0.01)] but not unmyelinated sensory fiber current thresholds. These findings suggest that in SCD mice, rapamycin increases HbF and modulates current thresholds of myelinated fibers. Therefore, mTOR signaling might be implicated in the pathobiology of SCD.

Cognitive and behavior deficits in sickle cell mice are associated with profound neuropathologic changes in hippocampus and cerebellum

Strokes are perhaps the most serious complications of sickle cell disease (SCD) and by the fifth decade occur in approximately 25% of patients. While most patients do not develop strokes, mounting evidence indicates that even without brain abnormalities on imaging studies, SCD patients can present profound neurocognitive dysfunction. We sought to evaluate the neurocognitive behavior profile of humanized SCD mice (Townes, BERK) and to identify hematologic and neuropathologic abnormalities associated with the behavioral alterations observed in these mice. Heterozygous and homozygous Townes mice displayed severe cognitive deficits shown by significant delays in spatial learning compared to controls. Homozygous Townes also had increased depression- and anxiety-like behaviors as well as reduced performance on voluntary wheel running compared to controls. Behavior deficits observed in Townes were also seen in BERKs. Interestingly, most deficits in homozygotes were observed in older mice and were associated with worsening anemia. Further, neuropathologic abnormalities including the presence of large bands of dark/pyknotic (shrunken) neurons in CA1 and CA3 fields of hippocampus and evidence of neuronal dropout in cerebellum were present in homozygotes but not control Townes. These observations suggest that cognitive and behavioral deficits in SCD mice mirror those described in SCD patients and that aging, anemia, and profound neuropathologic changes in hippocampus and cerebellum are possible biologic correlates of those deficits. These findings support using SCD mice for studies of cognitive deficits in SCD and point to vulnerable brain areas with susceptibility to neuronal injury in SCD and to mechanisms that potentially underlie those deficits.

Dexmedetomidine ameliorates nocifensive behavior in humanized sickle cell mice

Patients with sickle cell disease (SCD) can have recurrent episodes of vaso-occlusive crises, which are associated with severe pain. While opioids are the mainstay of analgesic therapy, in some patients, increasing opioid use results in continued and increasing pain. Many believe that this phenomenon results from opioid-induced tolerance or hyperalgesia or that SCD pain involves non-opioid-responsive mechanisms. Dexmedetomidine, a specific α2-adrenoreceptor agonist, which has sedative and analgesic properties, reduces opioid requirements, and can facilitate opioid withdrawal in clinical settings. We hypothesized that dexmedetomidine would ameliorate the nociception phenotype of SCD mice. Townes and BERK SCD mice, strains known to have altered nociception phenotypes, were used in a crossover preclinical trial that measured nocifensive behavior before and after treatment with dexmedetomidine or vehicle. In a linear dose-effect relationship, over 60-min, dexmedetomidine, compared with vehicle, significantly increased hot plate latency in Townes and BERK mice (P≤0.006). In sickle, but not control mice, dexmedetomidine improved grip force, an indicator of muscle pain (P=0.002). As expected, dexmedetomidine had a sedative effect in sickle and control mice as it decreased wakefulness scores compared with vehicle (all P<0.001). Interestingly, the effects of dexmedetomidine on hot plate latency and wakefulness scores were different in sickle and control mice, i.e., dexmedetomidine-related increases in hotplate latency and decreases in wakefulness scores were significantly smaller in Townes sickle compared to control mice. In conclusion, these findings of beneficial effects of dexmedetomidine on the nociception phenotype in SCD mice might support the conduct of studies of dexmedetomidine in SCD patients.

Dexmedetomidine as an Adjuvant to Analgesic Strategy During Vaso-Occlusive Episodes in Adolescents with Sickle-Cell Disease.

Patients with sickle‐cell disease (SCD) can experience recurrent vaso‐occlusive episodes (VOEs), which are associated with severe pain. While opioids are the mainstay of analgesic therapy, in some patients with SCD, increasing opioid use is associated with continued and increasing pain. Dexmedetomidine, an α2‐adrenoreceptor agonist with sedative and analgesic properties, has been increasingly used in the perioperative and intensive care settings and has been shown to reduce opioid requirement and to facilitate opioid weaning. Therefore, there might be a role for dexmedetomidine in pain management during VOEs in patients with SCD. Here, we present the hospital course of 3 patients who during the course of VOEs had severe pain unresponsive to opioids and ketamine and were treated with dexmedetomidine. Dexmedetomidine infusions that lasted for 3 to 6 days were associated with marked reduction in daily oral morphine‐equivalent intake and decreases in pain scores (numeric rating scale). There were no hemodynamic changes that required treatment with vasoactive or anticholinergic agents. These preliminary findings of possible beneficial effects of dexmedetomidine in decreasing opioid requirements support the hypothesis that dexmedetomidine may have a role as a possible analgesic adjuvant to mitigate VOE‐associated pain in patients with SCD.

Blood collection vials and clinically used intravenous fluids contain significant amounts of nitrite

Abstract The biology of the inorganic anion nitrite is linked to nitric oxide (NO) as nitrite can be reduced to NO and mediate its biological activities. Thus, studies of nitrite biology require sensitive and selective chemical assays. The acetic and ascorbic acids method is selective for nitrite and measures it in biological matrices. However, one of the pitfalls of nitrite measurements is its ubiquitous presence in sample collection tubes. Here, we showed high levels of nitrite in collection tubes containing EDTA, sodium citrate or sodium heparin and smaller amounts in tubes containing lithium heparin or serum clot activator. We also showed the presence of nitrite in colloid and crystalloid solutions frequently administered to patients and found variable levels of nitrite in 5% albumin, 0.9% sodium chloride, lactated ringers, and dextrose‐plus‐sodium chloride solutions. These levels of nitrite varied across lots and manufacturers of the same type of fluid. Because these fluids are administered intravenously to patients (including those in shock), sometimes in large volumes (liters), it is possible that infusions of these nitrite‐containing fluids may have clinical implications. A protocol for blood collection free of nitrite contamination was developed and used to examine nitrite levels in whole blood, red blood cells, plasma and urine from normal volunteers. Nitrite measurements were reproducible, had minimal variability, and did not indicate sex‐differences. These findings validated a method and protocol for selective nitrite assay in biological fluids free of nitrite contamination which can be applied for study of diseases where dysfunctional NO signaling has been implicated. Graphical abstract Figure. No Caption available. HighlightsNitrite is one of the most important NO‐derived chemical species.Nitrite contamination during sample collection is an issue for nitrite assays.Variable levels of nitrite were found in blood collection tubes.Variable levels of nitrite were found in intravenous fluids used clinically.A protocol to collect biological samples without nitrite contamination is described.

Altered nocifensive behavior in animal models of autism spectrum disorder: The role of the nicotinic cholinergic system.

Caretakers and clinicians alike have long recognized that individuals with autism spectrum disorder (ASD) can have altered sensory processing, which can contribute to its core symptoms. However, the pathobiology of sensory alterations in ASD is poorly understood. Here we examined nocifensive behavior in ASD mouse models, the BTBR T+Itpr3tf/J (BTBR) and the fragile-X mental retardation-1 knockout (Fmr1-KO) mice. We also examined the effects of nicotine on nocifensive behavior given that nicotine, a nicotinic cholinergic receptor (nAChR) agonist that has antinociceptive effects, was shown to improve social deficits and decrease repetitive behaviors in BTBR mice. Compared to respective controls, both BTBR and Fmr1-KO had hyporesponsiveness to noxious thermal stimuli and electrical stimulation of C-sensory fibers, normal responsiveness to electrical stimulation of Aβ- and Aδ-fiber, and hyperresponsiveness to visceral pain after acetic acid intraperitoneal injection. In BTBR, nicotine at lower doses increased, whereas at higher doses, it decreased hotplate latency compared to vehicle. In a significantly different effect pattern, in control mice, nicotine had antinociceptive effects to noxious heat only at the high dose. Interestingly, these nocifensive behavior alterations and differential responses to nicotine antinociceptive effects in BTBR mice were associated with significant downregulation of α3, α4, α5, α7, β2, β3, and β4 nAChR subunits in several cerebral regions both, during embryonic development and adulthood. Taken together, these findings further implicate nAChRs in behaviors alterations in the BTBR model and lend support to the hypothesis that nAChRs may be a target for treatment of behavior deficits and sensory dysfunction in ASD.

Carbon monoxide incompletely prevents isoflurane-induced defects in murine neurodevelopment

BACKGROUNDnCommonly used anesthetics have been shown to disrupt neurodevelopment in preclinical models. It has been proposed that such anesthesia-induced neurotoxicity is mediated by apoptotic neurodegeneration in the immature brain. Low dose carbon monoxide (CO) exerts cytoprotective properties and we have previously demonstrated that CO inhibits isoflurane-induced apoptosis in the developing murine brain. Here we utilized anti-apoptotic concentrations of CO to delineate the role of apoptotic neurodegeneration in anesthesia-induced neurotoxicity by assessing the effect of CO on isoflurane-induced defects in neurodevelopment.nnnMETHODSnC57Bl/6 mouse pups underwent 1-hour exposure to 0ppm (air), 5ppm, or 100ppm CO in air with or without isoflurane on postnatal day 7. Cohorts were evaluated 5-7weeks post exposure with T-maze cognitive testing followed by social behavior assessment. Brain size, whole brain cellular content, and neuronal density in primary somatosensory cortex and hippocampal CA3 region were measured as secondary outcomes 1-week or 5-7weeks post exposure along with 7-day old, unexposed controls.nnnRESULTSnIsoflurane impaired memory acquisition and resulted in abnormal social behavior. Low concentration CO abrogated anesthetic-induced defects in memory acquisition, however, it also resulted in impaired spatial reference memory and social behavior abnormalities. Changes in brain size, cellular content, and neuronal density over time related to the age of the animal and were unaffected by either isoflurane or CO.nnnCONCLUSIONSnAnti-apoptotic concentrations of CO incompletely prevented isoflurane-induced defects in neurodevelopment, lacked concentration-dependent effects, and only provided protection in certain domains suggesting that anesthesia-related neurotoxicity is not solely mediated by activation of the mitochondrial apoptosis pathway.

Dexmedetomidine for patients undergoing diagnostic cardiac procedures: A noninferiority study

When anesthetizing children with congenital heart disease for diagnostic cardiac catheterization, anesthesiologists and cardiologists seek to use anesthetic regimens that yield minimal hemodynamic changes and allow for spontaneous ventilations. Recently, dexmedetomidine has been used as an anesthesia adjunct because of its sedative and analgesic properties and minimal ventilatory depressive effects. We tested the hypothesis that the combination of sevoflurane and dexmedetomidine is non-inferior to sevoflurane alone as it refers to hemodynamic measurements during diagnostic cardiac catheterization in children with a transplanted heart, one ventricle (Fontan procedure), or normal cardiac physiology. Patients were anesthetized with inhalation of sevoflurane in nitrous oxide/oxygen and, after baseline hemodynamic measurements, successive boluses of dexmedetomidine followed by continuous infusion were administered. In this study, non-inferiority was shown when differences at steady-state (dexmedetomidinexa0+xa0sevoflurane) compared to baseline (sevoflurane alone) and its associated 95% confidence interval fell completely within the range of plus or minus 20%. Forty-one (26 normal physiology, 9 cardiac transplantation, and 6 Fontan) patients were enrolled. Non-inferiority of sevofluranexa0+xa0dexmedetomidine compared with sevoflurane alone was shown for heart rate, but not for arterial blood pressure in patients with normal and cardiac transplant physiology. In patients with normal cardiac physiology, non-inferiority was demonstrated for bispectral index. Therefore, while the lack of depressive respiratory effects and non-inferiority for heart rate are desirable, the lack of non-inferiority of dexmedetomidinexa0+xa0sevoflurane combination for arterial blood pressure do not justify the routine use of this combination compared with sevoflurane alone for children with congenital heart disease undergoing cardiac catheterization.