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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.54 no.2 Campinas Mar./Apr. 2004
Dexmedetomidine as adjuvant drug for wake-up test during scoliosis correction surgery. Case report*
Dexmedetomidina como droga adyuvante en el despertar transitorio en el intra-operatorio de corrección quirúrgica de escoliosis. Relato de caso
Airton Bagatini, TSA, M.D.I; Daniel Volquind, M.D.II; André Rosso, M.D.II; Rubens Devildos Trindade, M.D.III; João Carlos Germano Splettstösser, TSA, M.D.IV
ICo-Responsável pelo CET/SBA
IIME2 do CET/SBA do SANE
IIIAnestesiologista do CET/SBA do SANE
IVInstrutor do CET/SBA do SANE
BACKGROUND AND OBJECTIVES:Scoliosis is
a spinal defect very often requiring surgical correction. A uniqueness of this
correction is the need for intraoperative emergence and leg movement (wake up
test) to rule out central nervous system (CNS) injury after correction of the
orthopedic defect. In our report, dexmedetomidine was associated to total intravenous
anesthesia with propofol and remifentanil to induce sedation, analgesia and
ventilatory stability during wake up test in patient submitted to surgical scoliosis
CASE REPORT: Caucasian, female patient, 16 years old, physical status ASA I, with lumbar and thoracic scoliosis in 12 levels, submitted to surgery under general anesthesia. Patient was premedicated with 2 mg oral lorazepam the day before and 90 minutes before surgery. Venoclysis and left arm radial artery puncture were performed after monitoring; right subclavian vein was punctured with double lumen catheter for drug infusion and hemodynamic evaluation. Anesthesia was induced with 1 µg.kg-1 remifentanil and propofol in target-controlled infusion, for 3 µg.mL-1 plasma concentration. Neuromuscular block was achieved with 0.5 mg.kg-1 atracurium. Anesthesia was maintained with 0.4 µg.kg-1.h-1 dexmedetomidine and 0.3 µg.kg-1.min-1 remifentanil in continuous infusion, and 3 µg.mL-1 propofol in target-controlled infusion. At lower limbs movement test, propofol and remifentanil were withdrawn, but dexmedetomidine was maintained. Patient returned to spontaneous ventilation with anesthetic recovery and 14 minutes after drug withdrawal patient has moved lower limbs at verbal command. During this procedure, patient remained in Ramsay's sedation stage 3 that is, under analgesia, spontaneous ventilation and relaxed.
CONCLUSIONS: Dexmedetomidine associated to total intravenous anesthesia was an interesting option as adjuvant drug for the wake-up test as well as for perioperative analgesia and sedation.
Key Words: ANALGESICS, Opioids: remifentanil; DRUGS, a2-agonist: dexmedetomidine; HYPNOTICS: propofol; SURGERY, Orthopedic: scoliosis correction
JUSTIFICATIVA Y OBJETIVOS: La escoliosis
es un defecto de la columna vertebral que necesita muchas veces de corrección
quirúrgica. Una peculiaridad de esta corrección es la necesidad
del paciente despertar en el intra-operatorio y movimentar los miembros inferiores
con la finalidad de alejar lesiones del SNC después de la corrección
del defecto ortopédico. En este relato, fue asociada dexmedetomidina
a la anestesia venosa total con propofol y remifentanil con el objetivo de obtener
las acciones sedativa, analgésica y de estabilidad ventilatoria de esta
droga, durante el despertar transitorio en paciente sometida a corrección
quirúrgica de escoliosis.
RELATO DE CASO: Paciente del sexo femenino, 16 años, blanca, estado físico ASA I, con escoliosis torácica y lumbar en 12 niveles, fue sometida a cirugía sobre anestesia general. Como medicación pre-anestésica fue utilizado lorazepam en la dosis de 2 mg, por vía oral, en la víspera y 90 minutos antes del procedimiento. Después de monitorización, fue realizada venóclisis y punción de la arteria radial en el miembro superior izquierdo; la vena subclávia derecha fue punzionada con catéter de duplo lumen, para infusión de drogas y medidas hemodinámicas. La inducción anestésica fue hecha con 1 µg.kg-1 de remifentanil y propofol, en infusión alvo-controlada, para concentración plasmática de 3 µg.ml-1. Como bloqueador neuromuscular, fue utilizado atracúrio en la dosis de 0,5 mg.kg-1. La manutención de la anestesia fue realizada con infusión continua de dexmedetomidina (0,4 µg.kg-1.h-1), remifentanil (0,3 µg.kg-1.min-1) y propofol (3 µg.ml-1) en infusión alvo-controlada. En el momento del test para movimentación de los miembros inferiores, fueron interrumpidas las infusiones de propofol y remifentanil, manteniendo la dexmedetomidina. Con la superficialización del plano anestésico, la paciente se encargó de la ventilación espontanea y después de 14 minutos de la interrupción de las drogas, sobre comando verbal, movimentó los miembros inferiores. Durante este procedimiento, la paciente permaneció en la parte 3 de sedación de Ramsay, esto es, bajo analgesia, respirando espontáneamente y tranquila.
CONCLUSIONES: La dexmedetomidina asociada a la anestesia venosa total se mostró una opción interesante, como droga coadyuvante en el test de despertar, bien como para el propósito de analgesia y sedación en el período perioperatorio.
Scoliosis is a spinal curvature and/or rotation defect sometimes requiring surgical correction 1. A uniqueness of this correction is the need for intraoperative emergence and leg movement to diagnose intraoperative central nervous system (CNS) injuries caused by spinal rectification after scoliosis correction.
Several anesthetic techniques have been used for this procedure. In our report dexmedetomidine was associated to total intravenous anesthesia with propofol and remifentanil to induce sedation, analgesia and ventilatory stability during wake-up test in patient submitted to surgical scoliosis correction.
Caucasian, female patient, 16 years old, physical status ASA I, with lumbar and thoracic scoliosis in 12 levels, submitted to surgery under general anesthesia. Preoperative evaluation revealed hematocrit: 39.2 g/dL; hemoglobin: 13.2 g/dL; creatinine: 0.79 mg/dL; urea: 18 mg/dL; glycemia: 85 mg/dL; prothrombin time: 74%; and platelets: 203000. Spinal X-ray has revealed dorsal scoliosis with convexity to the right and Cobb'sangle 2 of 22º, and lumbar scoliosis with convexity to the left and Cobb's angle of 21º. Preoperative blood pressure was 130 x 80 mmHg and heart rate was 72 beats per minute. Patient was premedicated with 2 mg oral lorazepam the day before and 90 minutes before surgery. Monitoring consisted of ECG (DII), pulse oximetry, invasive blood pressure, nasopharyngeal temperature, capnography, central venous pressure and diuresis.
After monitors placement, venoclysis was performed in the right arm with 14G intravenous catheter and left radial artery puncture with 20G intravenous catheter, both preceded by skin infiltration with 1% lidocaine without vasoconstrictor. Right internal jugular vein was punctured after anesthetic induction with a 7F double lumen catheter for drugs infusion and hemodynamic evaluation. Anesthesia was induced with 1 µg.kg-1 remifentanil and propofol in target-controlled infusion for 3 µg.mL-1 plasma concentration. Atracurium (0.5 mg.kg-1) was the neuromuscular blocker for tracheal intubation achieved with 7.5 mm tube without intercurrences. Ventilation was controlled with electropneumatic constant flow ventilator cycled by time in valve circle system with CO2 absorber. Anesthesia was maintained with dexmede- tomidine (0.4 µg.kg-1.h-1) and remifentanil (0.3 µg.kg-1.min-1) continuous infusion and propofol (3 µg.mL-1) target-controlled infusion.
At wake-up test, propofol and remifentanil were withdrawn, but dexmedetomidine was maintained. Patient returned to spontaneous ventilation with anesthetic recovery and 14 minutes after drug withdrawal patient has moved lower limbs at verbal command. During this procedure, patient remained in Ramsay's 3 sedation stage 3, that is, under analgesia, spontaneous ventilation and relaxed, with 100% oxygen saturation and 30 mmHg PETCO2. Heart rate has varied 85 to 95 bpm, systolic blood pressure 92 to 95 mmHg, diastolic blood pressure 50 to 55 mmHg and mean blood pressure 60 to 70 mmHg.
At surgery completion patient was extubated and referred to post-anesthetic recovery unit (PACU). Postoperative analgesia was induced with intravenous ketoprofen (100 mg) every 12 hours, dipirone (1 g) every 4 hours and dexmedetomidine (0.2 µg.kg-1.h-1). During the 12-hour period of PACU stay, patient has not referred significant pain and, when asked, she denied recalling intraoperative emergence period, remaining hemodynamically stable.
The first reports on dexmedetomidine in humans and evidence analgesic, sedative, ventilatory and hemodynamic stability properties of this drug date from the early 1990s. 4,5.
Dexmedetomidine is a high-selective a2-agonist in the order of 1620:1, considered today the prototype of a2-agonists and is formed by medetomidine's dextrogyrous enantiomer 6. It has been approved in the USA by the Food and Drug Administration in 1999 for clinical use in humans, being initially used in intensive care centers for intubated patients under mechanical ventilation 7,8.
Dexmedetomidine analgesic and sedative properties have made it the adjuvant drug of choice to maintain patients intraoperatively awaken and able to move lower limbs, as preconized for surgical scoliosis correction to evaluate possible CNS injury 1,8.
Even in high doses, dexmedetomidine is not followed by respiratory depression and allows patients to be easily awakened and cooperative 9.
Dexmedetomidine sedative properties are due to the activation of a2-agonist receptors in locus coeruleus, resulting in increased activity of inhibitory neurons, which are part of the g-aminobutyric acid (GABA) pathway, determining CNS depression 8.
Dexmedetomidine has major activity in modulating pain involving supra-spinal and spinal receptors, inhibiting stimulation conduction through Ad and C fibers. It also intervenes in descending noradrenergic post-synaptic pathways of cholinergic neurons and on encephalins and nitric oxide release 4,5.
Total intravenous anesthesia with propofol and remifentanil was chosen due to drugs pharmacokinetic properties which have helped patient's emergence. Metabolized by plasma esterases, remifentanil has context-dependent half-life of 10 minutes, not taking into consideration drug infusion time 10.
Fast metabolism drugs, as those already mentioned, allow fast return to spontaneous ventilation and consciousness without residues or active metabolites, allowing patients to respond to verbal commands.
Propofol was administered through Diprifusor®, infusion pump developed for target-controlled continuous infusion of this drug. It has a software which relates patients' age and weight to target-dose to calculate infusion rate and emergence time after drug withdrawal, as from 16 years of age 11.
Patient has awakened 14 minutes after drugs withdrawal, which has been considered adequate since Diprifusor® has estimated emergence in 12 minutes. There are reports in the literature with emergence times varying 5.7 to 8.9 minutes, but using different anesthetic techniques, such as midazolam, mivacurium, alfentanil 12, fentanyl, nitrous oxide and isoflurane 13.
Bispectral index was a monitored parameter in reports found in the literature 12,14. In our case, due to the unavailability of brain electric activity monitoring with bispectral index (BIS), target-controlled dose was higher than needed, resulting in late emergence (14 minutes) as compared to the literature. However, it has not impaired surgery duration, but has urged for the observation of this potential bias in further cases.
Dexmedetomidine pharmacokinetic properties in central vasomotor centers and related to the cardiovascular system were important for the maintenance of controlled arterial hypotension necessary to decrease intraoperative bleeding 8. In our case, systolic blood pressure was maintained between 95 and 92 mmHg, diastolic blood pressure between 55 and 50 mmHg and mean blood pressure between 60 and 70 mmHg which is in line with the literature (mean blood pressure of 55 to 65 mmHg) when controlled intraoperative arterial hypotension is used 15.
Dexmedetomidine has met all postoperative analgesic needs during its infusion time, not requiring additional doses of opioids, such as morphine. The literature is not totally in agreement as to this item and continuous or intermittent intravenous opioids and epidural or spinal analgesia have been used in larger scale remaining postoperative analgesia a matter of each center's experience 15.
The day after surgery, patient was asked about anesthesia and wake-up test and has reported no pain and no recalls of that moment. Dexmedetomidine associated to total intravenous anesthesia has shown to be an interesting option as adjuvant drug in the emergence test, as well as for perioperative analgesia and sedation.
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Dr. Airton Bagatini
Rua Santana, 483/301
90040-373 Porto Alegre, RS
Apresentado (Submitted) em 01 de
abril de 2003
Aceito (Accepted) para publicação em 01 de julho de 2003
* Recebido do (Received from) CET/SBA do SANE Hospital Ernesto Dornelles, Porto Alegre, RS