Renato Santiago Gomez

Morphine versus remifentanil for intubating preterm neonates.

A double-blind, randomised controlled study was conducted to evaluate the intubation conditions in 20 preterm neonates following the use of either morphine or remifentanil as premedication. The findings suggest that the overall intubation conditions were significantly better (p = 0.0034) in the remifentanil group than in the morphine group. No severe complications were observed in either group.

Single-injection femoral nerve block with 0.25% ropivacaine or 0.25% bupivacaine for postoperative analgesia after total knee replacement or anterior cruciate ligament reconstruction

STUDY OBJECTIVE To investigate the effects of single-injection femoral nerve block (FNB) in postoperative pain after total knee replacement (TKR) and anterior cruciate ligament (ACL) reconstruction. DESIGN Prospective, randomized, double-blind study. PATIENTS 96 ASA physical status I, II, and III patients, scheduled for TKR or ACL reconstruction. INTERVENTIONS All patients received a standard spinal anesthetic, then were randomly divided into three treatment groups as follows: Group B (n = 30) received an FNB with 40 mL of 0.25% bupivacaine containing epinephrine, 1:200,000; Group R (n = 32) received an FNB with 40 mL of 0.25% ropivacaine; and Group C (n = 28) received no FNB. MEASUREMENTS The following clinical outcomes were assessed at up to 6 hours (T1), 6 to 10 hours (T2), and 10 to 24 hours (T3) after spinal anesthesia was given: visual analog scale (VAS) for pain, both at rest and on movement (no or mild pain, moderate pain, or severe pain); morphine use; sensory block in the femoral, obturator, and lateral femoral cutaneous nerve dermatomes; and motor block of the femoral and obturator nerves. MAIN RESULTS Except for VAS during rest and on movement at time T3, there were more Group C patients who experienced moderate or severe pain than those who had no pain or mild pain, when compared with Groups R and B. Sensory block in the femoral and lateral femoral cutaneous nerve dermatomes did not differ between Groups R and B at any times. However, sensory block in the obturator nerve dermatome was lower in Group R than Group B only at T3. We observed a lower, significant use of morphine at T2 when comparing Groups R and B with Group C. No Group R patient and about 30% of Group B patients remained with motor block of femoral and obturator nerves at T3. Except for frequency of nausea, which was highest in Group C, the frequency of other side effects was similar among the three groups. CONCLUSIONS Femoral nerve block using 0.25% ropivacaine or 0.25% bupivacaine is an effective method of postoperative analgesia after TKR and ACL reconstruction, particularly for the first 10 hours after spinal anesthesia.

Avaliação da dor em neonatologia

JUSTIFICATIVA Y OBJETIVOS: El estudio del dolor ha avanzado mucho en las ultimas decadas haciendo con que la evaluacion y la intervencion sean una preocupacion creciente entre los profesionales de la salud. El objetivo de la evaluacion del dolor debe ser el de proporcionar datos precisos para determinar cuales acciones deben ser toma de las para aliviarlo o eliminarlo y la mismo tiempo, evaluar la eficacia de esas acciones. La finalidad de esta revision fue discutir los metodos utilizados en la evaluacion del dolor en neonatologia, cuando las estrategias de tratamiento utiliza de las sin una evaluacion sistematica del dolor no son eficaces o adecua de las. CONTENIDO: No existe ninguna tecnica ampliamente aceptada y facilmente ejecutable y uniforme para la evaluacion del dolor en ninos, especialmente en los recien nacidos y lactantes que pueda ser utilizada en todas las situaciones. Antes de confiar en la exactitud de los datos de Evaluacion, se hace necesario que los profesionales de la salud se sientan seguros con los instrumentos usados en la recoleccion del esos datos. Varios indicadores pueden ser usados en la evaluacion, cuantificacion y calificacion del estimulo doloroso, y cuando se analizan en conjunto, permiten el desglose entre el dolor y los estimulos no dolorosos. Aunque sea deseable la estandarizacion objetiva para la medicion de la intensidad del dolor, tal medida no existe todavia. La medicion ene sea franja etaria es hecha por medio de parametros fisiologicos (frecuencia cardiaca, frecuencia respiratoria, presion arterial, etc) y comportamentales (expresion facial, postura y vocalizacion o verbalizacion), utilizando escalas de evaluacion, cada una con sus ventajas y limitaciones. CONCLUSIONES: La actual atencion para mejores metodos de medida y evaluacion del dolor aporto para aumentar la sensibilidad de los profesionales de salud con relacion a la naturaleza de las experiencias dolorosas. El dolor debe ser entendido como la quinta senal vital y evaluada de manera sistematizada, tambien en los recien nacidos.BACKGROUND AND OBJECTIVES The study of pain has seen a great development in the last decades, making evaluation and intervention a growing concern among health professionals. The objective of pain evaluation should be to provide accurate data to determine the actions that should be taken to relieve or abolish it and, at the same time, to evaluate the efficacy of those actions. The objective of this review was to discuss the methods used to evaluate pain in neonatology, since treatment strategies used without systematic pain evaluation are not effective or adequate. CONTENTS A widely accepted, easy to apply and uniform technique to evaluate pain in children, especially newborns and infants, that can be used in all situations does not exist. Before trusting the accuracy of the data, it is necessary that health professionals trust the instruments used to collect the data. Several indicators can be used to evaluate, quantify, and qualify the painful stimulus and, when analyzed as a set, allow the discrimination between pain and non-painful stimuli. Although the objective standardization of measuring pain severity is desirable, it does not exist. Measurement of pain in this age group is done by assessing physiological (heart rate, respiratory rate, blood pressure, and etc.) and behavioral (facial expression, posture, and vocalization or verbalization) parameters using evaluation scales, each one with its advantages and limitations. CONCLUSIONS The current concern with better methods to measure and evaluate pain contributed to increase the sensitivity of health professionals regarding the nature of painful experiences. Pain should be valued as the fifth vital sign and evaluated in a systemized manner, including in newborns.

Brainstem anaesthesia after peribulbar anaesthesia

PurposeTo present a case of brainstem anaesthesia as a complication of peribulbar anaesthesia.Clinical featuresA 75-yr-old woman received peribulbar anaesthesia for cataract surgery. A few seconds after the block was performed, she had a respiratory arrest, became unconscious, and developed hypertension and tachycardia followed by hypotension and bradycardia. Ventilatory and haemodynamic support were performed before the patient regained adequate spontaneous breathing and normal heart rate and blood pressure.ConclusionPeribulbar anaesthesia generally cames a low risk of serious complications. However, respiratory arrest and brainstem anaesthesia may occur as complications of peribulbar blocks.RésuméObjectifPrésenter un cas d’anesthésie du tronc cérébral compliquant une anesthésie péribulbaire.Éléments cliniquesUn bloc péribulbaire était réalisé chez une femine de 75 ans pour l’extraction d’une cataracte. Quelques secondes après l’injection, la patiente cessait de respirer et perdait conscience. Elle devenait hypertendue et tachycarde puts hypotendue et bradycarde. La ventilation et la circulation devaient être supportées jusqu’au retour spontané à la normale.ConclusionEn général, l’anesthésie péribulbare comporte un faible risque de complications sérieuses. Un arrêt respiratoire par anesthésie du tronc cérébral est toujours possible.

Differential effects of calcium channel antagonists on tityustoxin and ouabain-induced release of [3H]acetylcholine from brain cortical slices

In this paper, the effect of calcium channel blockers on acetylcholine release induced by tityustoxin and ouabain in rat brain cortical slices is described. Cadmium, a non-specific blocker of calcium channels, inhibited the release of ACh induced by tityustoxin. L-type calcium channel blockers (verapamil, nifedipine and diltiazen) had no effect on the release of ACh induced by tityustoxin. The release of ACh was also unaffected by nickel, a T-type calcium channel blocker, and the conotoxins GVIA and MVIIC, blockers of N and Q-type calcium channels. Agatoxin IVA, a specific blocker of the P-type calcium channel, inhibited the release of ACh induced by tityustoxin by 50%. The spontaneous release of ACh as well as ouabain-induced release of ACh was unaffected by any of the calcium channel blockers studied. It is concluded that ACh release induced by tityustoxin is mediated by Ca2+ influx via P-type calcium channels.

Remifentanil for sedation and analgesia in a preterm neonate with respiratory distress syndrome

We present the efficacy and safety of the use of remifentanil for intubation, sedation and analgesia in a preterm infant during mechanical ventilation for respiratory distress syndrome. A 34‐week‐old baby, born by cesarean delivery that developed respiratory distress, required intubation and ventilatory support. For intubation, the baby was given midazolam (0.2 mg·kg−1) and remifentanil (1 μg·kg−1). The intubation conditions were assessed and classified as excellent. The remifentanil infusion was started at dose 0.75 μg·kg−1·min−1 and the dose adjustments were made depending on the neonatal infant pain scale (NIPS), hemodynamic and respiratory changes or the presence of spontaneous movements. Pulse oximetry, respiratory rate, ECG and invasive blood pressure were continuously monitored. He was given surfactant within 2.5 h of life after which ventilator parameters could be progressively decreased. Three hours later, the remifentanil infusion was decreased to 0.5 μg·kg−1·min−1, and he remained sedated (NIPS < 2). Six hour after surfactant administration, blood gases and chest X ray were normal. The remifentanil infusion was then discontinued and 30 min later the baby was awake and extubated with success. There were no side effects after intubation or during the continuous infusion. The profile of remifentanil allowing a rapid recovery, the absence of side effects and a good level of sedation and analgesia support the choice of this opioid for sedation in the NICU.

Early awakening and extubation with remifentanil in ventilated premature neonates

Background:  Morphine is one of the most commonly used drugs for sedation and analgesia during mechanical ventilation, but its pharmacological profile has limitations, such as prolonged duration of action, especially in premature neonates. Because of its very short context‐sensitive half‐time, remifentanil has rapid onset and quickly decreases in plasma concentration after interrupting administration. The aim of the present study was to compare a continuous infusion of remifentanil and morphine during mechanical ventilation of premature neonates with respiratory distress syndrome (RDS).

Inhibition of Na+,K+‐ATPase by Ouabain Opens Calcium Channels Coupled to Acetylcholine Release in Guinea Pig Myenteric Plexus

Abstract: Ouabain, an Na+,K+‐ATPase inhibitor, increases the release of acetylcholine (ACh) from various preparations in a Ca2+‐independent way. However, in other preparations the release of ACh evoked by ouabain is dependent on the presence of extracellular calcium. In the present study, we have labeled the ACh of myenteric plexus longitudinal muscles of guinea pig ileum and compared the effect of calcium channel blockers on ouabain‐evoked release of [3H]ACh. Release of [3H]ACh evoked by ouabain is dose dependent and decreased markedly in the absence of calcium or in the presence of cadmium, a nonspecific calcium channel blocker. N‐type calcium channel blockage by the ω‐conotoxins GVIA (selective N‐type calcium channel blocker) and MVIIC (a nonselective calcium channel blocker) inhibited by 45 and 55%, respectively, the release of [3H]ACh. L‐type calcium channel suppression by low concentrations of verapamil, nifedipine, and diltiazem had no effect on the release of [3H]ACh. The release of transmitter was also not affected significantly by nickel, a T‐type calcium channel blocker. In addition, ω‐agatoxin‐IVA, at concentrations that block P‐ and Q‐type calcium channels, did not affect significantly the release of [3H]ACh. Thus, extracellular Ca2+ is essential for the release of ACh induced by ouabain from guinea pig ileum myenteric plexus. In this preparation, the N‐type calcium channel plays a dominant role in transmitter release evoked by inhibition of Na+,K+‐ATPase, but other routes of calcium entry in addition to these channels can also support the release of neurotransmitter induced by ouabain.

An Evaluation of the Antinociceptive Effects of Phα1β, a Neurotoxin from the Spider Phoneutria nigriventer, and ω-Conotoxin MVIIA, a Cone Snail Conus magus Toxin, in Rat Model of Inflammatory and Neuropathic Pain

Voltage-sensitive calcium channels (VSCCs) underlie cell excitability and are involved in the mechanisms that generate and maintain neuropathic and inflammatory pain. We evaluated in rats the effects of two VSCC blockers, ω-conotoxin MVIIA and Phα1β, in models of inflammatory and neuropathic pain induced with complete Freund’s adjuvant (CFA) and chronic constrictive injury (CCI), respectively. We also evaluated the effects of the toxins on capsaicin-induced Ca2+ influx in dorsal root ganglion (DRG) neurons obtained from rats exposed to both models of pain. A single intrathecal injection of Phα1β reversibly inhibits CFA and CCI-induced mechanical hyperalgesia longer than a single injection of ω-conotoxin MVIIA. Phα1β and MVIIA also inhibited capsaicin-induced Ca2+ influx in DRG neurons. The inhibitory effect of Phα1β on capsaicin-induced calcium transients in DRG neurons was greater in the CFA model of pain, while the inhibitory effect of ω-conotoxin MVIIA was greater in the CCI model. The management of chronic inflammatory and neuropathic pain is still a major challenge for clinicians. Phα1β, a reversible inhibitor of VSCCs with a preference for N-type Ca2+ channels, has potential as a novel therapeutic agent for inflammatory and neuropathic pain. Clinical studies are necessary to establish the role of Phα1β in the treatment of chronic pain.

Mechanism of action of volatile anesthetics: involvement of intracellular calcium signaling.

There have been extensive efforts to characterize the mechanism of action of volatile anesthetics, but their molecular and cellular actions are still a matter of debate. Volatile anesthetics act primarily on synaptic transmission in the central nervous system but proof of this as the predominant mechanism of action remains elusive. Changes in neurotransmitter release may relate to direct interaction of the anesthetic molecule with an ion channel protein or synaptic protein, but can also be a consequence of alterations in intracellular signaling. Calcium is one of the most important messengers in cells and its intracellular concentration may be modified by several agents including volatile anesthetics. Neuronal excitability is in part determined by calcium availability that is controlled by several mechanisms. Because voltage-gated calcium channels (VGCC) play a key role in controlling Ca2+ entry and in initiating cellular responses to stimulation through an elevation of intracellular calcium concentration ([Ca2+](i)), they are thought to be one of the targets for volatile anesthetics. However, [Ca2+](i) can also be altered without the participation of VGCC through receptor-mediated pathways. Indeed, calcium homeostasis is also controlled by plasma membrane Ca2+ -adenosine triphosphatase, sarcoplasmic-endoplasmic reticular Ca2+ -ATPase, the Na+ -Ca2+ exchanger, and mitochondrial Ca2+ sequestration. Alteration of any of those mechanisms that control [Ca2+](i) may lead to a change in presynaptic transmission or postsynaptic excitability. Here we will review some of the recent progress in identifying putative actions of volatile anesthetics, specifically the effect on intracellular calcium homeostasis in neurons.