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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.55 no.6 Campinas Nov./Dec. 2005
Bilateral pudendal nerves block for postoperative analgesia with 0.25% S75:R25 bupivacaine. Pilot study on outpatient hemorrhoidectomy*
Analgesia pos-operatoria con bloqueo bilateral del nervio pudendo con bupivacaína S75:R25 a 0,25%. Estudio piloto en hemorroidectomia bajo régimen ambulatorial
Luiz Eduardo Imbelloni, TSA, M.D.I; Lúcia Beato, TSA, M.D.II; Carolina Beato, M.D.II; José Antônio Cordeiro, M.D.III; Dulcimar Donizete de Souza, M.D.IV
do Instituto de Anestesia Regional, Hospital de Base, São José do
Rio Preto, Anestesiologista da Clínica São Bernardo, Rio de Janeiro,
IIAnestesiologista da Clínica São Bernardo, Rio de Janeiro, RJ
IIIProfessor Livre Docente em Probabilidade e Estatística da Faculdade de Medicina de São José do Rio Preto, SP
IVDoutor em Ciências da Saúde; Diretor Adjunto de Pessoal da Faculdade de Medicina de São José do Rio Preto, SP
OBJECTIVES: Hemorrhoidectomy may be performed under several anesthetic techniques
and in outpatient regimen. Postoperative pain is severe and may delay discharge.
This study aimed at evaluating bilateral pundendal nerves block for post- hemorrhoidectomy
METHODS: Bilateral pundendal nerves block with 0.25% S75:R25 bupivacaine was performed with nerve stimulator in 35 patients submitted to hemorrhoidectomy under spinal anesthesia. Evaluated parameters were pain severity, duration of analgesia, demand analgesia and possible technique-related complications. Data were evaluated 6, 12, 18, 24 and 30 hours after surgery completion.
RESULTS: Successful pudendal nerves stimulation was achieved in all patients. There has been no severe pain in all evaluated moments. At 12 hours after blockade, all patients had perineal anesthesia; at 18 hours, 17 patients and at 24 hours, 10 patients still presented perineal anesthesia. Postoperative analgesia was optimal for 18 patients; satisfactory, for 5 patients; and unsatisfactory, for 7 patients. Mean analgesic duration was 23.77 hours. There were no changes in blood pressure, heart rate, no nausea and vomiting were observed. All patients had spontaneous micturition. No local anesthetic-related local or systemic complications were observed. Technique was considered excellent by 27 patients and only 3 male patients considered it satisfactory due to penile anesthesia.
CONCLUSIONS: Bilateral pudendal nerves block oriented by nerve stimulator provides excellent analgesia with low need for opioids, without local or systemic complications and without urinary retention. Controlled studies might be able to show whether this should be the first analgesic option for hemorrhoidectomies. Perineal anesthesia lasting 20.21 hours shall induce further studies with stimulator-oriented pudendal block.
Key words: ANESTHETICS, Local: bupivacaine, enantiomeric mixture (S75:R25); ANESTHETIC TECHNIQUES, Regional: pudendal block; SURGERY, Anorectal: hemorrhoidectomy
Y OBJETIVOS: La hemorroidectomia puede ser realizada bajo varias técnicas
anestésicas y en régimen ambulatorial. El dolor pos-operatorio es
intenso y puede atrasar el retorno para el hogar. El objetivo de este estudio
fue evaluar las ventajas y la realización del bloqueo bilateral de los
nervios pudendos para analgesia pos-operatoria en hemorroidectomias.
MÉTODO: El bloqueo bilateral de los nervios pudendos con bupivacaína S75:R25 a 0,25% fue realizado con estimulador de nervios en 35 pacientes sometidos a la hemorroidectomia bajo raquianestesia. Fueron evaluadas intensidad del dolor, duración de la analgesia, analgesia de demanda y eventuales complicaciones relacionadas a la técnica. Los datos fueron evaluados a las 6, 12, 18, 24 y 30 horas después del término de la intervención quirúrgica.
RESULTADOS: En todos los pacientes, fue logrado éxito con la estimulación de ambos los nervios pudendos. En ningún momento de la evaluación ocurrió dolor intenso. Hasta 12 horas después del bloqueo, todos los pacientes presentaron anestesia en la región perineal; con 18 horas, 17 pacientes y 24 horas, 10 pacientes A analgesia pos-operatoria fue óptima en 18 pacientes; satisfactoria, en cinco pacientes; e insatisfactoria, en siete pacientes. La duración media de la analgesia fue de 23,77 horas. No ocurrieron alteraciones de la presión arterial, de la frecuencia cardiaca, ni fueron observados náuseas o vómitos. Todos los pacientes tuvieron micción espontánea. Ninguna complicación local o sistémica fue relacionada al anestésico local. Veintisiete pacientes clasificaron de excelente la técnica de analgesia y apenas tres pacientes del sexo masculino quedaron satisfechos, justificado por la anestesia en el pene.
CONCLUSIONES: El bloqueo bilateral de los nervios pudendos, orientado por estimulador de nervios proporciona una analgesia de excelente calidad, con baja necesidad de opioides, sin complicaciones local o sistémica y sin retención urinaria. Estudios controlados permitirán demostrar si esta técnica debe ser la primera opción para la analgesia en hemorroidectomias. La permanencia de anestesia perineal por 20,21 horas deberá inducir nuevos trabajos con el bloqueo de los nervios pudendos orientado por estimulador para el acto quirúrgico.
Hemorrhoidal diseases are common throughout the world and are symptomatic in 4.4% of the population 1. Approximately 90% of anorectal procedures may be performed in outpatient regimen 2. Among all treatments for hemorrhoidal diseases, surgical resection seems to be the best to eliminate symptoms and improve quality of life 3. However, severe postoperative pain may prolong hospital stay 4. Postoperative pain is a major outpatient regimen problem 5. A retrospective study with 1100 patients submitted to outpatient procedures has shown that 35% of patients had moderate to severe pain at home, in spite of analgesic therapy 6. Several analgesic methods have been proposed for post-hemorrhoidectomy pain relief, such as subcutaneous morphine with infusion pump 7, transcutaneous electric stimulation 8, dexametazone 9, perianal infiltration with bupivacaine 10, posterior perineal block 11 and of the ischiorectal fossa 12.
The pudendal nerve is formed by posterior S2, S3 and S4 branches and is divided in four branches: inferior anal nerves, perineal nerves, posterior labial nerves (females), posterior scrotal nerves (males), clitoris dorsal nerve (females) and penile dorsal nerve (male) 13. In theory, pudendal nerve block may provide perineal analgesia or anesthesia being often used by surgeons and obstetricians. Peripheral nerve stimulator, which is an excellent teaching method for regional anesthesia, helps the anesthesiologist in this type of blockade due to location monitored by perineal muscles contracture.
Different animal and human studies have shown that levogyrous local anesthetics are less toxic for central nervous and cardiovascular systems as compared to racemic or dextrogyrous bupivacaine, with intrinsic ability to promote vasoconstriction and less intense motor block 14,15. A comparison of racemic and bupivacaine with levogyrous enantiomeric excess of 50% (S75;R25) for brachial plexus block, has not shown differences in observed parameters 16. Authors concluded suggesting that S75:R25 is a safer alternative as compared to racemic bupivacaine due to lower toxicity 16.
This study aimed at evaluating post-hemorrhoidectomy analgesia with 0.25% S75:R25 bupivacaine bilaterally injected in pudendal nerves located with the aid of electrical stimulation.
After the Ethics Committee approval and their informed consent, participated in this study 35 patients physical status ASA I and II, aged 20 to 60 years, submitted to spinal anesthesia with 50 mg of 2% isobaric lidocaine for hemorrhoidectomy in outpatient regimen. Spinal anesthesia was induced in the left lateral position in L3-L4 interspace, by the paramedial route with 27G Quincke needle (B. Braun Melsungen S.A.). Monitoring consisted of noninvasive blood pressure, heart rate and pulse oximetry. Patients were not premedicated. Venoclysis was installed in the operating room with lactated Ringer's and 50 to 100 µg fentanyl were intravenously administered. Minimum intraoperative fluids were administered, always below 500 mL.
Bilateral pudendal nerves block was performed at surgery completion with patients in lithotomy position and under spinal anesthesia effect. The needle access was transperineal and medial to ischial tuberosity on both sides, using beveled insulated needle with 100 mm (B. Braun Melsungen AG, 21G 0.8 x 100 mm needle) connected to peripheral nerve stimulator (Stimuplex®, B. Braun Melsungen AG) set to release a square pulsatile current of 1 mA, with 2 Hz frequency, perpendicularly inserted to a depth of approximately 7 cm, trying to obtain anal sphincter contraction. After perineal contraction, 20 mL of 0.25% bupivacaine (S75:R25) were injected in each side.
Patients were followed for six hours in the hospital and then at 12, 18, 24 and 30 hours by telephone when they were questioned about pain severity, which was classified as: absent (level 0), mild (level 1), moderate (level 2) or severe (level 3). Patients were also asked whether the operated region was insensitive (anesthesia). Pain at first evacuation was evaluated with the same scale and time between blockade and first evacuation was recorded. Patients were asked about postoperative analgesia, which should be classified as excellent, satisfactory or poor.
Oral tramadol was prescribed in case of pain. Analgesia was classified as optimal if no analgesic (tramadol) was needed; satisfactory (one dose) and unsatisfactory (two or more doses). Demographics data, painless period, pain severity, oral analgesic frequency, total doses and complications, such as urinary retention, were evaluated.
Qualitative variables (presence of pain, pain severity, pain at first evacuation, blockade at 6, 12, 18, 24 and 30 hours and level of satisfaction) were evaluated with regard to gender by Fisher's Exact test. Quantitative variables compared with regard to time were analyzed by paired t test, and with regard to gender by t test for two samples, assuming different variances.
Demographics data are shown in table I. Spinal anesthesia was satisfactory for all patients and no patient needed complementation with general anesthesia. Both pudendal nerves were successfully stimulated in all patients. There were no changes in blood pressure and heart rate, there were no postoperative nausea or vomiting. All patients had spontaneous micturition. No local or systemic complications were related to local anesthetics.
Pain severity in the first 30 postoperative hours is shown in table II and there has been no maximum pain (severe) throughout the study. All patients presented perineal anesthesia 12 hours after blockade. At 18 hours, 22 patients; at 24 hours, 12 patients and at 30 hours, no patient presented perineal anesthesia (Table II).
At 6 and 12 postoperative hours no female has referred mild pain and four males have referred it (remaining males did nor refer pain), showing a higher incidence of pain in males in these moments. At 18 hours, one female has referred mild pain as compared to 10 males, with a high incidence of pain among males. At 24 hours, two females have referred moderate pain and no one has referred mild pain, while among males there has been one case of moderate and nine cases of mild pain, showing a higher incidence of mild or moderate pain among males. Two females have referred pain at first postoperative evacuation as compared to eight males. At 12 post-blockade hours, all patients had perineal anesthesia; at 18 hours, 22 patients, being 15 females and 7 males, indicating lower probability of blockade for males in this period. At 24 hours, blockade persisted in 12 patients, being 5 females and 7 males, with no statistically significant difference in this moment.
Analgesia duration was 15 to 20 hours in 10 patients; 21 to 25 hours, in 14 patients; 26 to 30 hours, in 10 patients; and more than 31 hours in 1 patient, with mean duration of 23.77 hours. Postoperative analgesia was optimal for 23 patients; satisfactory, for 5 patients, and unsatisfactory, for seven patients. There has been no need for postoperative analgesia in 23 patients. First evacuation was approximately 30 hours after bilateral pudendal nerves block; 10 patients have referred pain at evacuation, while 25 patients have not. Analgesic technique was considered excellent by 32 patients and only 3 male patients have considered it satisfactory due to penile anesthesia. There has been no difference in level of satisfaction between genders (p = 0.10) (Table III and Table IV).
External hemorrhoidal thrombosis is probably one of the most common anorectal emergency diagnoses and surgery is the treatment, of choice. In our study, postoperative analgesia with bilateral pudendal nerves block under spinal anesthesia has resulted in mean 23.77 hours analgesia with low need for opioids and 23 patients without rescue medication.
Hemorrhoidectomy is a short procedure, however extremely painful, and few studies are directed toward postoperative analgesia 17. Major pain factors are related to surgical procedure. Milligan-Morgan technique (open) seems to be much more painful as compared to Reis Neto semi-open hemorrhoidectomy or even to the closed procedure 18. Some authors use posterior perineal block for anesthesia and postoperative analgesia.
There are several variants of initial descriptions 11,19,20. Differences refer to technical details, equipment and anesthetic drugs. It is also necessary to differentiate pararectal infiltration from perineal block. Pararectal (or perineal) infiltration is a superficial posterior perineal block often used as single technique 21. Our study has used bilateral pudendal nerves block oriented by nerve stimulator, resulting in perineal anesthesia for 20.21 hours and showing that blockade may be used as single technique for the proposed procedure. It was not our proposal to evaluate differences in the incidence of pain between genders. However, there has been higher incidence of pain among males as compared to females in all evaluated periods and during first evacuation. These data shall be the object of further studies.
All anesthetic drugs have already been used for posterior perineal block: bupivacaine, lidocaine, mepivacaine, ropivacaine, associated or not, with or without epinephrine, and in volumes varying from 20 to 50 mL. Lidocaine or mepivacaine administered to 400 patients have induced analgesia for 5 hours in 31.5%, for more than 10 hours in 48.5% and for more than 15 hours in 9.2%; 3.2% had no need for analgesics 11. One to three mL of 0.5% bupivacaine injected in the base of each hemorrhoid 10 minutes before incision have allowed a painless period 10 times longer as compared to control group 10. The injection of 20 mL of 0.25% bupivacaine with levogyrous enantiomeric excess of 50% (S75:R25) in each pudendal nerve has promoted mean 23.77 hours analgesia. A different publication 16 evaluating the same solution with twice the concentration (0.5%) in the brachial plexus has not evaluated analgesia duration, thus not allowing the comparison of results.
Spinal anesthesia leads to clinical vesical function disorders due to the interruption of micturition reflex. Bladder function remains imperfect until the blockade has regressed to the 3rd sacral segment in all patients 22. With long lasting anesthetics, accumulated volume may exceed the cystometric capacity of the bladder 17. For this reason, spinal anesthesia in our study was induced with 50 mg of 2% isobaric lidocaine, in an attempt to prevent urinary retention caused by the anesthetic technique, which was confirmed by spontaneous micturition in all patients. This shows that bilateral pudendal nerves block has resulted in perineal anesthesia for approximately 20 hours without preventing spontaneous micturition.
This pilot study has used bilateral pudendal nerves block with the aid of peripheral nerve stimulator to control postoperative pain of patients submitted to hemorrhoidectomy under spinal anesthesia. The study has its limitations because analgesia results were not compared to a different method.
Based on our results, we consider that bilateral pudendal nerves block with peripheral nerve stimulator for postoperative analgesia with 0.25% S75:R25 bupivacaine may be indicated for all anorectal procedures, provided no previous infection is present. With this technique, analgesia is effective, without local or systemic complications, making first evacuation less painful and without side effects, such as urinary retention. In the future, controlled and comparative studies may show whether this technique should be the first option for hemorrhoidectomy analgesia. Mean perineal anesthesia duration of 21.20 hours shall induce further studies with pudendal nerves block and nerve stimulator.
We acknowledge professor Manoel Antônio Pereira Alvarez for suggesting the study.
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Dr. Luiz Eduardo Imbelloni
Address: Av. Epitácio Pessoa, 2356/203 Lagoa
ZIP: 22471-000 City: Rio de Janeiro, RJ
publication April 28, 2005
Accepted for publication July 6, 2005
* Received from Instituto de Anestesia Regional, São José do Rio Preto, SP