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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.52 no.3 Campinas May/June 2002
Spinal anesthesia for outpatient pediatric surgery in 1 - 5 years old children with 0.5% isobaric enantiomeric mixture of bupivacaine (S75-R25) *
Raquianestesia con mezcla enantiomérica de bupivacaína a 0,5% isobárica (S75-R25) en niños con edad de 1 a 5 años para cirugía ambulatorial
Luiz Eduardo Imbelloni, TSA, M.D. I; Eneida Maria Vieira, M.D.II; Lúcia Beato, M.D.III; Francine Sperni, M.D.IV
IAnestesiologista da Casa de Saúde
Santa Maria e Clínica São Bernardo. Rio de Janeiro, RJ
IIAuxiliar de Ensino do Hospital de Base da FAMERP
IIIAnestesiologista da Casa de Saúde Santa Maria e Clínica São Bernardo. Rio de Janeiro, RJ
IVME2 do CET/SBA do Hospital de Base da FAMERP
BACKGROUND AND OBJECTIVES: Commercially
available bupivacaine is a racemic mixture of S(-) and R(+) enantiomers. Although
the S(-) bupivacaine enantiomer is less toxic than R(+) bupivacaine to cardiovascular
and central nervous systems, its relative efficacy has not yet been determined
in spinal anesthesia for pediatric surgery. The aim of this study was to evaluate
the effects of spinal anesthesia with a 0.5% isobaric mixture of S(-) bupivacaine(75%)
+ R(+) bupivacaine(25%) in 40 children aged 1 to 5 years scheduled for outpatient
METHODS: Participated in this prospective study 40 patients aged 1 to 5 years submitted to spinal anesthesia with 0.5 mg.kg-1 of a 0.5% isobaric mixture of 75% S(-) bupivacaine + 25% R(+) bupivacaine. The following parameters were observed: onset of analgesia, degree of motor block, duration of effects, cephalad spread of analgesia, cardiovascular changes, incidence of headache and transient neurological symptoms.
RESULTS: Mean onset time was 2.29 ± 0.64 min. Duration of analgesia was 4.13 ± 0.89 h. Time to ambulate was 3.50 ± 0.81 h. Mean PACU stay was 43.80 ± 31.34 min. Motor block duration was 1.89 ± 0.78 h. Sensory block level varied from T9 to T4 (Mode=T6). Motor block onset time was less than two minutes in all children, all reaching grade 3 motor block (modified Bromage scale) in the beginning of surgery. Over 55% of all patients recovered to motor block 1 or zero at the end of the surgery. No patient developed oxygen desaturation or arterial hypotension. Bradycardia was observed in one patient. There were two block failures. There were no headache or transient neurological symptoms.
CONCLUSIONS: Isobaric 0.5% levobupivacaine (R25-S75) induces a safe spinal anesthesia in patients aged 1 to 5 years scheduled for outpatient procedures, with a high success rate, short-lasting motor block, relatively low incidence of side effects and at a lower cost. Headache seems to be rare in patients below five years of age when a thin needle is used. Our results have shown that spinal anesthesia is a safe and easy technique for children between 1 and 5 years of age in outpatient procedures.
Key words: ANESTHETICS, Local: enantiomeric mixture of bupivacaine; ANESTHETIC TECHNIQUES, Regional: spinal block
JUSTIFICATIVA Y OBJETIVOS: La bupivacaína
comercialmente utilizada se presenta como mezcla racemica RS(±) bupivacaína.
Aunque el enantiómero levógiro S(-), levobupivacaína, sea menos
tóxico para el sistema nervioso central y cardiovascular de que la R(+)
bupivacaína, su relativa eficacia aun no fue determinada en la raquianestesia
en niños. El objetivo de este estudio prospectivo fue evaluar la mezcla
enantiomérica de bupivacaína S75-R25 en 40 niños, con edades
entre 1 y 5 años.
MÉTODO: Participaron del estudio prospectivo, 40 niños con edades entre 1 y 5 anos, sometidos a raquianestesia con mezcla enantiomérica de bupivacaína (S75-R25) a 0,5% isobárica en la dosis de 0,5 mg.kg-1. Fueron evaluados los siguientes parámetros: latencia de la analgesia, bloqueo motor, duración de los efectos, dispersión cefálica de la analgesia, alteraciones cardiovasculares, cefalea y síntomas neurológicos transitorios.
RESULTADOS: El tiempo de latencia fue de 2,29 ± 0,64 min. La duración de la analgesia fue de 4,13 ± 0,89 h. El tiempo de deambulación fue de 3,50 ± 0,81 h. El tiempo de permanencia en la SRPA fue de 43,80 ± 31,34 min. La duración del bloqueo motor fue de 1,89 ± 0,78 h. El nivel sensitivo de bloqueo varió entre T9 y T4 (Moda=T6). El inicio del bloqueo motor fue menor que dos minutos en todos los niños. Todos presentaron bloqueo motor grado 3 (escala modificada de Bromage) al inicio de la cirugía. Más de 55% de los pacientes presentaron bloqueo motor 1 ó ausencia de bloqueo al final de la cirugía. No fue observada desaturación o hipotensión arterial. Bradicardia fue observada en un paciente. Ocurrieron dos fallas. Cefalea y SNT no fueron observados.
CONCLUSIONES: La mezcla enantiomérica de la bupivacaína (S75-R25) a 0,5% isobárica produce una anestesia segura en pacientes de 1 a 5 años en régimen ambulatorial, con alto índice de suceso, bloqueo motor de corta duración de acción, relativa baja incidencia de efectos colaterales y un costeo menor. Cefalea pós-punción parece ser rara en pacientes abajo de 5 años cuando se utiliza agujas de calibre fino. Nuestros resultados mostraron que la raquianestesia es segura y fácilmente realizable en niños de 1 a 5 años en régimen ambulatorial.
Since the first publications on spinal anesthesia for pediatric patients appeared in Brazilian literature 1,2, this technique has become a routine in several centers. Spinal anesthesia has a fast onset, with uniform analgesia and excellent muscle relaxation. Spinal anesthesia allows for low local anesthetic doses with low toxicity risk. Amide anesthetics are regularly used for pediatric spinal anesthesia, among them lidocaine 1 and bupivacaine 3. However, duration of spinal lidocaine may be short in some children requiring general anesthesia complementation 1. On the other hand, bupivacaine has a fast onset and long duration of action.
The isolation of racemic bupivacaine resulted in the identification of levogyrous and dextrogyrous enantiomers. Levobupivacaine may be used pure or in mixtures of varying ratios such as 10% R(+) bupivacaine and 90% S(-) bupivacaine; or 25% R(+) bupivacaine + 75% S(-) bupivacaine 4, that was used in this study (S75-R25 bupivacaine).
Local anesthetics baricity is one major factor influencing anesthetic distribution in the CSF 4. Hyperbaric 1,2 and isobaric 3 solutions are used in pediatric spinal anesthesia with excellent results, but the excess enantiomeric mixture of 0.5% isobaric bupivacaine has not yet been tested in children.
This study aimed at evaluating analgesia quality, spread, regression time, and time for PACU and hospital discharge following 0.5% isobaric S75-R25 bupivacaine spinal anesthesia in children aged 1 to 5 years submitted to outpatient procedures.
After the Hospitals Ethical Committee approval and parents informed consent, 40 patients aged 1 to 5 years, submitted to outpatient pediatric surgeries (Table I) under spinal anesthesia with 0.5 mg.kg-1 S75-R25 bupivacaine were evaluated. Exclusion criteria were spinal anesthesia contraindications, such as increased intracranial pressure, hemorrhagic disorders, neurological disorders or puncture site infection.
Children were oriented not to ingest solid food or milk for 6-8 hours before surgery. Fluids without residues were ingested up to 2 hours before anesthetic induction. All children were premedicated with oral midazolam (0.8 mg.kg-1) 20 minutes before admission to the operating room. Anesthesia was induced under mask with oxygen and sevoflurane up to 5%, followed by venous puncture and 0.9% saline infusion. Already anesthetized, children were placed in the left lateral position and lumbar puncture was paramedially performed in L3-L4 or L4-L5 interspace with disposable pediatric needles (26G Atraucan® - B. Braun Melsungen AG), without introducer. Correct needle position was confirmed by CSF visualization. Once CSF was obtained, needle was directed to the cephalad region and the calculated dose of 0.5% S75-R25 bupivacaine (supplied by Cristália-Produtos Químicos e Farmacêuticos Ltda) in sterilized packages was injected without barbotage at 1 ml.15 s-1. Patients were then immediately placed in the supine position.
Perioperative monitoring consisted of non-invasive blood pressure at 5-minute intervals, heart rate and hemoglobin oxygen saturation (SpO2). ECG was continuously monitored at CM5. When blood pressure dropped bellow 30% of baseline values, treatment consisted of increasing crystalloids infusion and ephedrine administration. Heart rate was considered normal when around 125 bpm in children aged 1 to 3 years and 100 bpm in children aged 3 to 5 years. If HR decreased more than 15% of control, 0.01 mg.kg-1 atropine was administered.
After blockade and sevoflurane withdrawal, blockade onset was evaluated and defined as time for loss of sensitivity in the region corresponding to the puncture metamer. Segmental analgesia level was defined as loss of pinprick sensation and was tested 10 minutes after anesthetic injection. Motor block was evaluated by modified Bromage scale (0 = no blockade and 3 = total motor block) in the beginning and the end of surgery.
After surgery, children were transferred to PACU for continuous monitoring of vital signs and blockade regression observation. Analgesia duration was considered as the time elapsed for sensitivity to return to the dermatome corresponding to the puncture, and motor block duration as time for total return of lower limbs muscle activity. All adverse effects were recorded. In the presence of pain, 20 mg.kg-1 iv metamizol was administered. As soon as children were freely moving lower limbs, they were transferred to the day-care unit.
Hospital discharge was allowed when children were awaken, ambulating freely, with stable vital signs, no pain, no nausea and vomiting and able to ingest fluids. Patients were followed for 3 postoperative days to evaluate post-dural puncture headache or transient neurological symptoms (TNS) defined by pain or dysesthesias on back, buttocks or legs irradiating to lower extremities and resolving within 72 hours. Children were followed for 30 days to evaluate irreversible neurological complications. Results are shown in mean (± SD) and were analyzed by Kruskal-Wallis and Wilcoxon Signed Rank (median test) tests for comparing blood pressure, heart rate and oxygen saturation values being considering significant when p < 0.05.
Demographic data are shown in table II. Blockade characteristics are shown in table III. Onset time was 2.29 ±0.64 min. Analgesia duration was 4.13 ± 0.89 h. Ambulation time was 3.50 ± 0.81 h. PACU stay was 43.80 ± 31.34 min. Motor block duration was 1.89 ± 0.78 h. Upper analgesia level varied from T9 to T4 with Mode in T6 (Figure 1).
Motor block onset time was less than two minutes for all children. All presented motor block Bromage level 3 at the beginning of surgery. At the end, motor block level 3 was observed in 5 patients, level 2 in 12, level 1 in 15 and level zero in 6 patients. At the end of the surgery, 55% of patients presented motor block 1 or zero (Figure 2).
No patient developed oxygen desaturation or arterial hypotension. There has been a significant difference in MBP and HR between values at admission to the operating room and after spinal anesthesia (Table IV). Bradycardia was observed in 1 patient and corrected with atropine. There were two block failures and the surgery was performed under general anesthesia. There were no post-dural puncture headache or transient neurological symptoms.
Spinal anesthesia with 0.5% isobaric enantiomeric mixture of bupivacaine (S75-R25) induced adequate anesthesia in children aged 1 to 5 years and enabled outpatient abdominal surgeries. Motor block duration was shorter than in the adult. There were 2 failures complemented with general anesthesia.
Several authors have described both positions, sitting and lateral, as well as the use of different needle sizes. Regardless of age, we preferred left lateral position and 27G Quincke or 26G Atraucan cutting-edge needles 6,7.
Sedation or general anesthesia is often needed for pediatric blockade. This way, sensory block evaluation is difficult in small children sedated or even anesthetized with superficial inhalational anesthesia. Immediately after puncture, inhalational anesthesia was withdrawn and sensory level evaluation by pinprick was possible in almost all patients. Some authors counterindicate a deep sedation due to the possibility of paresthesia during spinal puncture, increasing the risk for permanent neurological injury 7. In our study, with sevoflurane inhalational induction, there have been no neurological complications up to 30 post-anesthetic days.
In 1970, Gouveia 1 studying 5% lidocaine spinal anesthesia has shown that the dose preconized for adult patients was not sufficient for pediatric anesthesia. In children with 2-115 months of age, 0.4 mg.kg-1 of 0.5% isobaric or hyperbaric bupivacaine has induced a median sensory block in T4 3, unnecessary for inguinal and perineal surgeries. In our study, in spite of the dose of 0.5 mg.kg-1 of S75-R25 bupivacaine, median sensory block was T6, or two segments below the above mentioned study 3.
Onset is fast with isobaric bupivacaine in children and takes less than two minutes 9. With S75-R25 bupivacaine, blockade onset was also shorter than two minutes. In adults, it has been observed an onset time (1.78 min.) 10 shorter than that obtained in children. This could be explained by residual general anesthesia, making difficult a response to painful stimulation. Sensory block onset with S75-R25 bupivacaine in pediatric spinal anesthesia needs further studies.
Incidence of side-effects was very low. Only one child needed atropine to correct bradycardia. Different from adolescents and adults, small children tolerate thoracic blockade levels with minor cardiocirculatory changes. Studying the effects of spinal anesthesia in children with high blockade level (thoracic), the expected heart rate and blood pressure decrease, common after spinal induced sympathectomy, has not been observed 11. Children below 5 years of age show minor or no blood pressure and heart rate changes after spinal anesthesia with sensory level between T5-T6 12. In our study, with children aged 1 to 5 years and levels between T9-T4, no systolic and diastolic blood pressure decrease was seen in the four evaluated moments. However, there has been a significant mean blood pressure difference between admission to the operating room and beginning of spinal anesthesia, which may be explained by the stress caused in children by a hostile environment. It is very difficult to determine blockade extension in pediatric spinal anesthesia, but anesthesia duration is consistently shorter than in adults. In children below two years of age, motor function recovery takes in average 70 minutes as compared to 114 minutes in children above 5 years of age and to 336 minutes in adults 12. Similar to 5% lidocaine 1, there has been a fast motor block recovery with levobupivacaine and 55% of children presented with motor block 1 or zero at the end of surgery. The reason for motor block time decrease is unknown, but might be related to the difference in CSF volume, spinal cord and roots diameter and area and also to local anesthetic absorption speed in the spinal space 12.
All types of needles are used in children. Our study has used 26G Atraucan needles, which combine a cutting edge with a pencil tip. Studying 200 children aged 2 to 128 months anesthetized with 24G Sprotte, 25G Quincke, 26G Atraucan and 27G Whitacre needles, a 5% post-dural puncture headache incidence was found, being 6% with Sprotte, 6% with Whitacre and 8% with Atraucan 13. In a different study with 60 children aged 1 to 7 years anesthetized with 25G Whitacre and Quincke needles, the same 5% incidence was observed 12. In patients with mean age of 44 years, 26G Atraucan needles have induced 0.4% of headache 14. In our study with 40 children aged 1 to 5 years and anesthetized with 26G Atraucan needles, there has been no post-dural puncture headache. Other authors 15 have described difficult CSF aspiration resulting in blockade failure, what has also been observed in our study.
Comparing spinal anesthesia with 50 mg of 1% lidocaine and general anesthesia for outpatient knee arthroscopy it has been observed that spinal anesthesia has provided faster recovery and better postoperative analgesia 16.
In the conditions of our study, 0.5% isobaric S75-R25 bupivacaine has induced adequate and safe anesthesia in patients aged 1 to 5 years for outpatient procedures. Short duration motor block followed by a low incidence of side-effects were useful for outpatient pediatric surgeries.
We acknowledge Prof. José Antonio Cordeiro for this statistical analysis support and advice.
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Luiz Eduardo Imbelloni
Address: Av. Epitácio Pessoa, 2356/203 Lagoa
ZIP: 22471-000 City: Rio de Janeiro, Brazil
Submitted for publication
August 27, 2001
Accepted for publication November 12, 2001
* Received from CET/SBA do Hospital de Base da Faculdade de Medicina de São José do Rio Preto (FAMERP) e Clínica São Bernardo, Rio de Janeiro, RJ