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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.51 no.6 Campinas Dec. 2001
Comparison between 0.25% bupivacaine and 0.2% ropivacaine in epidural anesthesia for thoracic surgery*
Estudio comparativo entre bupivacaína a 0,25% y ropivacaína a 0,2% en anestesia peridural para cirugía de tórax
Marcus Vinícius Martins Novaes, M.D.I; Carlos Roberto Lopes Francisco, M.D.II; Karina Bernardi Pimenta, M.D.III; Paulo Sérgio Gomes Lavinas, M.D.IV
ICo-responsável do CET/SBA do
Hospital do Câncer; Anestesiologista do Instituto Fernandes Figueira -
FIOCRUZ, Rio de Janeiro, RJ
IIAnestesiologista do Hospital do Câncer, Rio de Janeiro, RJ
IIIAnestesiologista do Hospital de Câncer; Intensivista da Clínica São Vicente da Gávea, Rio de Janeiro, RJ
IVResponsável pelo CET/SBA; Chefe do Serviço de Anestesiologia do Hospital do Câncer, Rio de Janeiro, RJ
BACKGROUND AND OBJECTIVES: Combined general/epidural
anesthesia has been used for several surgical procedures. Little has been published
in the literature about its use in thoracic surgery. This study aimed to evaluate
hemodynamic and ventilatory effects of combined general/epidural anesthesia
with 0.25% bupivacaine and 0.2% ropivacaine in patients submitted to thoracotomy.
METHODS: Participated in this prospective, comparative and randomized study 40 patients divided in two groups of 20. Each group received 10 ml of epidural local anesthetics. Group B received 0.25% bupivacaine and Group R received 0.2% ropivacaine. Epidural anesthesia was induced with the patients in lateral position, using the paramedian approach and a catheter for drug injection. General anesthesia was then induced in all patients with tracheal intubation. Hemodynamic and ventilatory parameters were evaluated in 9 moments.
RESULTS: In Group B, systolic blood pressure was lower at moment 5 and diastolic blood pressure was lower at moments 1 and 5. The need for ephedrine to correct hypotension was 8/20 in Group B as compared to 6/20 in Group R. Upper airway peak pressures and isoflurane MAC values were higher at moments 5 and 6 in Group R.
CONCLUSIONS: The association of thoracic epidural anesthesia and general anesthesia was safe and efficient for patients submitted to thoracotomy. Bupivacaine has produced a higher decrease in blood pressure and lower peak airway pressures as compared to ropivacaine.
Key Words: ANESTHETICS, Local: bupivacaine, ropivacaine; ANESTHETIC TECHNIQUES, Regional: thoracic epidural
JUSTIFICATIVA Y OBJETIVOS:
La anestesia peridural asociada a anestesia general ha sido usada en varias
especialidades quirúrgicas. En cirugía torácica su uso es poco
discutido en la literatura. Este estudio tuvo como objetivo evaluar los efectos
hemodinámicos y ventilatorios de la anestesia peridural torácica con
bupivacaína a 0,25% y ropivacaína a 0,2% asociada a anestesia general
en pacientes sometidos a toracotomia.
MÉTODO: Participaron de este estudio prospectivo, comparativo y aleatorio, cuarenta pacientes divididos en dos grupos de veinte. Cada grupo recibió un volumen de 10 ml de anestésico local, por vía peridural torácica. Grupo B (Bupivacaína 0,25%) y el Grupo R (Ropivacaína 0,2%). El bloqueo peridural fue realizado con los pacientes en decúbito lateral, punción paramediana y catéter para inyección de los fármacos A seguir, todos los pacientes recibieron anestesia general con IOT. Fueron analizados parámetros hemodinámicos y ventilatorios en 9 momentos.
RESULTADOS: La presión arterial sistólica fue menor en el momento 5 y la presión arterial diastólica en los momentos 1 y 5, ambas en el grupo B. La necesidad de efedrina para corregir hipotensión arterial fue de 8/20 en el grupo B, contra 6/20 en el grupo R. La presión de pico en las vías aéreas superiores fue siempre mas elevada en el grupo R y los valores de la CAM del isoflurano fueron mas elevados en los momentos 5 y 6 también en el Grupo R.
CONCLUSIONES: La técnica combinada peridural torácica y anestesia general se mostró eficaz y segura en los pacientes sometidos a toracotomia. Cuando se utilizó bupivacaína, la diminución de la presión arterial fue mayor y la presión máxima en las vías aéreas fue menor de que cuando fue utilizada ropivacaína.
Epidural anesthesia is beneficial both in the peri and postoperative period1.
The reversible blockade of sensory, motor and sympathetic fibers allows analgesia, relaxation and hemodynamic control, respectively2. The thoracic access has proven to be more effective than the lumbar approach in cardiac patients because it optimizes myocardial O2 balance with less sympathetic reflex changes3,4. The technique provides excellent analgesia5, faster extubation7, lower postoperative epinephrine and norepinephrine levels in cardiac surgeries8 and myocardial protection9.
A study has shown that epidural anesthesia effects on pulmonary function seem to be beneficial6. Both local anesthetics and opioids help diaphragmatic function10 by improving lung volume and capacity11 and decreasing postoperative complications1,2. Beneficial effects on coagulation12, such as decrease in platelet aggregation13 and blood flow and venous emptying improvement14, have also been described.
This study aimed to compare 0.25% bupivacaine and 0.2% ropivacaine in combined thoracic epidural/general anesthesia in patients submitted to thoracotomy.
After the Medical Ethics Committee approval and their informed consent, participated in this study 40 patients of both genders, aged 19 to 78 years, submitted to thoracotomy under combined thoracic epidural/general anesthesia. Patients were randomly divided in two groups. Group B (n=20) received 0.25% bupivacaine and Group R (n=20) received 0.2% ropivacaine. Exclusion criteria were age below 18 and above 80 years, body mass index higher than 27.5 kg/m2, symptomatic coronary disease, congestive heart failure, systolic blood pressure equal to or higher than 100 mmHg, significant renal, liver or cerebral-vascular disease, insulin-dependent diabetes, physical status ASA IV and V and/or FEV1 lower than 60% of baseline values, chronic obstructive lung disease, and epidural anesthesia counterindications.
The day before surgery patients were evaluated by clinical and lab exams and informed about the study and the technique.
Patients were premedicated with oral diazepam (10 mg) the night before surgery.
At the operating room and after a 14G catheter insertion, sedation was completed with titrated doses of midazolam, if necessary. Patients were monitored with automatic sphygmomanometer, pulse oximetry, continuous ECG in 5 shunts and invasive blood pressure in the radial artery.
After monitoring, patients were hydrated with 500 ml of lactated Ringer's solution and placed in the lateral position for thoracic epidural paramedian puncture performed in T6-T7 or T7-T8 interspace, using the loss of resistance to air technique. After introducing the catheter 5 cm into the epidural space, a test dose with 3 ml of 2% lidocaine with epinephrine 1:200,000 was applied. With patients in the supine position and after 3 minutes of the test dose (proven negative), a fixed volume of 10 ml of local anesthetics was injected, being 0.25% bupivacaine in Group B and 0.2% ropivacaine in Group R.
General anesthesia was induced 20 minutes after local anesthetic injection. During pre-oxygenation, venous lidocaine (20 mg) and fentanyl (50 µg), followed by 0.3 mg.kg-1 etomidate (maximum of 20 mg) in 2 minutes and 0.1 mg.kg-1 vecuronium were administered. Ventilation was performed under mask with 100% oxygen and isoflurane in increasing concentrations up to 1.5 MAC for 10 to 15 minutes. Fentanyl (2 µg.kg-1) was injected 3 minutes before tracheal intubation (Robertshaw tube) and venous lidocaine (1.5 mg.kg-1) was injected one minute before intubation. Anesthesia was maintained with 100% oxygen and isoflurane in a semi-closed circle system with CO2 absorber. Hydration was adequate to patients submitted to lung surgeries. Ventilation was mechanically controlled and in one-lung for most part of the surgery.
During and after general anesthesia induction other parameters were monitored: PETCO2, hourly urine output, naso-pharyngeal temperature and heart and lung auscultation with an esophageal scope.
Patients remained in PACU for the immediate postoperative period (until the next morning), unless when pneumectomies or other clinical conditions would indicate the referral to the Intensive Care Unit.
Postoperative analgesia was obtained with epidural fentanyl in continuous infusion.
Studied variables were: invasive blood pressure (systolic, diastolic and mean), heart rate, peak upper airway pressure (UA), pulmonary compliance, SpO2, PETCO2 and isoflurane's MAC, in addition to the need for ephedrine. Evaluations were performed in 9 moments, as follows:
M0 - Control (after epidural catheter)
M1 - 10 min after local anesthetic injection
M2 - 20 min after local anesthetic injection
M3 - 10 min after induction
M4 - before TI
M5 - 2 min after TI
M6 - after lateral position
M7 - after surgical incision
M8 - after rib retractor
For statistical analysis, SNEDECOR's F test was used for analysis of variance to compare arithmetic means of continuous variables (one-way); non parametric Chi-square test to compare ratios of discrete variables. Significance level was 5% (p < 0.05) for both cases.
Mean SPB, DBP, MBP and HR are shown in figures 1, 2, 3 and 4, respectively, in the 9 observation moments. After applying SNEDECOR's F test to compare means between Groups B and R, it was observed that there has only been a significant SBP difference in moment M5 when Group R was higher. As to DBP, there have been significant differences between groups in moments M1 and M5, again with higher values for Group R. There were no statistically significant differences in MBP and heart rate.
Upper airway peak pressure values after TI are shown in table III. There were significant differences in the four moments evaluated and means were higher for Group R.
SpO2 (Table VI) was significantly higher in two moments (M6 and M7) for Group B.
Table VII shows MAC values after anesthetic induction and the two moments in which they were higher for Group R (M5 = p < 0.01 and M6 = p < 0.05).
Eight out of 20 Group B (40%) patients needed at least one ephedrine dose (at some time after epidural block) as compared to 30% (6/20) in Group R, however without statistical significance [x2 = 0.44ns (p < 0.05)].
Hemodynamic effects of thoracic epidural anesthesia depend on several factors and should be carefully analyzed. Anesthetic volume and concentration, puncture site, ventricular filling conditions, type of surgery and physical status should be taken into consideration when analyzing results2.
Of both agents compared, bupivacaine is a racemic mixture and ropivacaine is synthesized as its S(-) enantiomer. Ropivacaine is less cardiotoxic, has a lower arrhythmogenic potential and higher safety margin between the convulsive and the lethal dose without loosing potency and duration of action. Physical-chemical properties are very similar, except for liposolubility. Both are similar in sensory block, but ropivacaine's motor block is less intense and of shorter duration in low concentrations15.
There has been an increase in systolic (SBP) and diastolic (DPB) blood pressure soon after tracheal intubation (TI) in Group R. Although not being significant, SBP and DBP changes at M6, M7 and M8 have shown a trend to increase also in Group R, which may point to a less potent sympathetic block with ropivacaine.
Upper airway peak pressures (UA) were higher in all moments for Group R. Several factors may cause an increase in UA pressure: secretions, bronchospasm, one-lung ventilation, insufficient muscle relaxation, surgical procedure, lateral position, malpositioning of the needle through needle catheter, age and chronic obstructive pulmonary disease16,17. It is possible that the lower motor block caused by 0.2% ropivacaine18 would increase intercostal muscles tone leading to lower thoracic compliance. So, pressures generated in UAs to expand the lungs would be higher. Although observing a progressive decrease in lung compliance, and according to other authors19, this decrease was not significant when comparing both groups. So, the low motor block level of ropivacaine, per se, may not be the single reason for high UA pressures in Group R, even because bupivacaine concentrations were also low.
Although a significant SpO2 decrease in Group R as compared to Group B, in moments M6 and M7 (exactly the moments of high UA pressures and low lung compliance), this was not clinically significant. Considering that both SpO2 and PETCO2 remained within normal levels20,21 and that there were no major changes in hemodynamic parameters related to thoracic epidural anesthesia22 as opposed to what has been observed by other authors24,25, it is possible that the proposed combined technique has not affected V/Q ratio, intrathoracic blood flow or post-induction short-circuit, as shown by Hahenberg et al.23.
MAC values point to the need of a deeper anesthesia in moments of higher stimuli (M4, M7 and M8). Both groups showed an increasing trend in MAC values. There have been statistically significant differences between groups in two moments: two minutes after TI and after lateral position. In both moments there has been a higher need for isoflurane to maintain hemodynamic control in Group R. Again, there has been a higher hypotensive trend in Group B, where blood pressure was maintained with less inhalational anesthetics.
Finally, the quality of the combined technique was evaluated in moments M7 and M8.Both groups had higher MAC mean values, although without statistical significance. So one may state that both 0.25% bupivacaine and 0.2% ropivacaine were effective in inducing anesthesia with the proposed technique and low isoflurane concentrations.
The anesthetic technique was safe and satisfactory in all patients studied. There were no events that could not be corrected by anesthesia basic and routine procedures. Blood pressure, ventilatory parameters and isoflurane concentration corrections were within what is clinically expected and accepted according to surgical stages and no anesthesia-induced complications were observed in the peri and postoperative period.
1. To the thoracic surgery department of Hospital do Câncer, represented by Dr. Edson Toscano, for the support and understanding during the protocol.
2. To former-residents of Hospital do Câncer who helped me in data collection, Drs. Rodrigo César Bitencourt Alvarenga, Marcelo de O. L. Bandeira de Mello, Luiz Guilherme L. Soares, Paulo Luiz V. da Silva Júnior, Zélia Viana Duarte, Flávio Elias Callil.
3. To the secretary of the Anesthesiology department, Miss Ana Cristina P. de Souza, for typing and formatting the study.
4. To Mr. Marcos Padilha for the review.
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Correspondence to Submitted for publication Fevruary 14, 2001 * Received
from Instituto Nacional de Câncer/Hospital do Câncer 1 - Rio de Janeiro
Dr. Marcus Vinícius Martins Novaes
Address: Rua Belizário Távora, 302/104 Bl. 01 - Laranjeiras
ZIP: 22245-070 City: Rio de Janeiro, Brazil
Accepted for publication May 25, 2001
Submitted for publication Fevruary 14, 2001
* Received from Instituto Nacional de Câncer/Hospital do Câncer 1 - Rio de Janeiro - RJ