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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094

Rev. Bras. Anestesiol. vol.54 no.6 Campinas Nov./Dec. 2004 



Restricted dorsal spinal anesthesia for ambulatory anorectal surgery. A pilot study*


Raquianestesia posterior para cirugías anorrectales en régimen ambulatorial. Estudio piloto



Luiz Eduardo Imbelloni, TSA, M.D.I; Eneida Maria Vieira, M.D.II; Marildo Assunção Gouveia, TSA, M.D.I; José Antônio Cordeiro, M.D.III

IDiretor do Instituto de Anestesia Regional
IIDiretora do Instituto de Anestesia Regional
IIIProfessor na Faculdade de Medicina de São José do Rio Preto





BACKGROUND AND OBJECTIVES: The increasing number of ambulatory procedures requires anesthetic methods allowing patients to be discharged soon after surgery completion. Currently, anorectal procedures are performed in inpatient settings. This study aimed at evaluating the feasibility of performing these procedures in outpatient settings with low hypobaric bupivacaine doses.
METHODS: Participated in this study 30 patients physical status ASA I and II, submitted to spinal anesthesia with 0.15% hypobaric bupivacaine with 27G Quincke needle for anorectal procedures. Spinal puncture was performed with patients in the prone position with the help of a pad under the abdomen to correct lumbar lordosis and the vertebral interspace.
RESULTS: Sensory block was obtained in all patients. Sensory block spread varied T10 to L2 (mode = T12). Only three patients presented motor block. Blockade length was 122.17 ± 15.35 minutes. No hemodynamic changes were observed in all patients. No patient developed post-dural puncture headache.
CONCLUSIONS: Hypobaric bupivacaine (6 mg) has provided predominantly sensory block after injection in the prone position. Major advantages were hemodynamic stability and patients' satisfaction, being a good indication for outpatient anesthesia.

Key Words: ANESTHETICS, Local, hypobaric bupivacaine; ANESTHETIC TECHNIQUES, Regional: spinal block; SURGERY: Anorectal


JUSTIFICATIVA Y OBJETIVOS: El aumento del número de cirugías ambulatoriales exige el empleo de métodos anestésicos que permitan la liberación del paciente después de la cirugía. Frecuentemente, las cirugías anorrectales son realizadas con los pacientes hospitalizados. Este estudio examina la posibilidad de que esos procedimientos puedan ser realizados en régimen ambulatorial con bajas dosis de bupivacaína hipobárica.
MÉTODO: Treinta pacientes, estado físico ASA I y II, fueron sometidos a la raquianestesia con solución hipobárica de bupivacaína a 0,15% a través de aguja 27G Quincke para cirugías anorrectales. La punción subaracnóidea fue realizada con el paciente en decúbito ventral con auxilio de un cojin en su abdomen para corregir la lordosis lumbar y el espacio intervertebral.
RESULTADOS: El bloqueo sensitivo fue logrado en todos los pacientes. Su dispersión varió de T10 a L2 con moda en T12. Apenas tres pacientes presentaron algún grado de bloqueo motor. La duración del bloqueo fue de 122,17 ± 15,35 minutos. Estabilidad hemodinámica fue observada en todos los pacientes. Ningún paciente desarrolló cefalea después de punción de la dura-máter.
CONCLUSIONES: Seis miligramos de bupivacaína a 0,15% en solución hipobárica proporcionaron un bloqueo predominantemente sensitivo, cuando inyectados en decúbito ventral. Las principales ventajas son la rápida recuperación, estabilidad hemodinámica y satisfacción del paciente, siendo una buena indicación para anestesia ambulatorial.




The widespread growth of ambulatory procedures requires changes in the clinical anesthesia practice. Economic and social pressures have changed surgeons and anesthesiologists views. Approximately 60% to 70% of all elective procedures in the USA and some European countries, and around 50% in Brazil, are currently performed in outpatient settings 1,2. Conventional spinal anesthesia may be undesirable for such procedures due to prolonged lower limb motor block with consequent change to unplanned hospital admission 3. So, anesthesiologists must become familiar with techniques allowing fast spinal block recovery. Studies with low hypobaric bupivacaine doses have shown that this technique helps fast recovery 4,5. However, low spinal anesthesia doses depend on individual response and some patients may not obtain adequate anesthesia.

Many anesthesiologists are familiar with saddle block to help anorectal or perineal surgeries. This technique however is not widely used and is not satisfactory for outpatient procedures. The dose is more important factor for anesthetic spread than anesthetic concentration or volume 6. Lidocaine (25 mg) with fentanyl (25 µg) or ropivacaine (4 mg) with fentanyl (25 µg) have been used for low spinal anesthesia after remaining for 20 minutes in the sitting position 7, providing acceptable surgical conditions for anorectal procedures.

Lumbosacral nerves may be blocked in three different ways: the first, with patients in the lateral position; the second with patients in the sitting position, and finally the third, with patients in the prone position. This study aimed at evaluating low 0.15% bupivacaine doses injected in the prone position, in ambulatory patients to induce surgical analgesia without lower limbs motor block.



After the Publication and Disclosure Board of Directors approval and their informed consent, participated in this study 30 patients, physical status ASA I and II, aged 20 to 60 years, submitted to spinal anesthesia for ambulatory anorectal procedures. Exclusion criteria were hypovolemia, coagulation disorders, infection and refusal of the proposed method. Monitoring included noninvasive blood pressure, heart rate and pulse oximetry. Patients were not premedicated. Venoclysis with lactated Ringer's solution infusion was started in the operating room and 25 to 50 µg fentanyl were injected through this route. Minimum fluid volume was intravenously injected in the intraoperative period, always below 500 mL. 

Patients were placed in the prone position with a pad (46 cm length, 9 cm width and 18 cm diameter) under the abdomen and 5º head-down. After dorsal region skin preparation with chlorhexidine, median spinal puncture was performed in L3-L4 interspace with disposable 27G Quincke needle (B. Braun Melsungen S.A.) without introducer. Space was identified by spontaneous CSF leakage and 6 mg (4 mL) of 0.15% hypobaric bupivacaine were administered (prepared as from 7.5 mg 0.5% isobaric bupivacaine plus 3.5 mL sterilized bi-distilled water), at a rate of 1 mL.15s-1 (Table I). Patients remained in this position until surgery completion.

Sensory block was evaluated at 1-minute intervals, and at 5-minute intervals after detection of onset time during the first 20 minutes in the dorsal region. Blockade onset was evaluated by loss of sensitivity in the region corresponding to the puncture. Lower limbs motor block was evaluated by modified Bromage scale from 0 to 3 8 where: 0 = free leg movements; 1 = inability to extend legs; 2 = inability to bend knees; 3 = inability to move ankle. At surgery completion, ability to move from the table to the stretcher was evaluated.

Sensory and motor blocks were evaluated in both limbs at 5, 10, 20, 40 and 60 minutes and at surgery completion. Hemodynamic parameters were evaluated at 3-minute intervals during the first 15 minutes after spinal puncture and then at 5-minute intervals until surgery completion.

Hypotension was defined as 30% decrease of baseline values, while bradycardia was defined as HR below 50 bpm. Hypotension was treated with 10 mg ethylenephenylephrine and bradycardia with 0.5 mg intravenous atropine. Oxygen flow of 2 L.min-1 was administered through nasal catheter or Hudson's mask. Midazolam (1 to 2 mg) was administered after the second evaluation (40 minutes).

Patients were transferred to the outpatient unit and were asked by a Anesthesiology resident about their satisfaction with anesthesia approach; patients should choose one of the terms: excellent, satisfactory or poor. Patients were discharged 4 hours after anesthetic injection and stabilization of vital signs for one hour, oriented, without nausea or vomiting, able to ingest liquids and walk. Patients were discharged after intravenous tramadol (50 mg) infusion at pain complaint. Time for injection and total sensory and motor block recovery, ability to urinate and walk, need for vesical catheter and pain data were recorded. Postoperative analgesia was induced with oral tramadol (50 mg) every 8 hours.

Patients were followed by telephone until the third postoperative day for post dural puncture headache or transient neurological symptoms (TNS), and until the 30th day for permanent neurological complications.

Quantitative variables were analyzed by descriptive statistics, being all comparisons made with non-parametric Kruskal-Wallis test. Student’s t test with Welch correction was used for mean age. Significance level was 5%.



Demographics data are shown in table II. Onset time was 2.20 ± 0.70 minutes.

All patients presented sensory roots block with no need for anesthetic complementation. Sensory block spread has varied T10 to L2 being mode equal to T12 at 20 minutes (Table III). Mean total blockade recovery time was 122.17 minutes. Total block recovery and surgery length were not significantly different between genders (p = 0.12 and 0.24, respectively). There were no evidences of sensory level differences between genders in all evaluated moments (p = 0.21 to 1). Our study has also not shown differences in mean ages (p = 0.30) and BMI (p = 0.13) between genders.

Lower limbs motor block level, according to the scale described in the method is shown in table III. There has been no total motor block during the evaluation. Motor block level 1 was observed in 3 patients at 20 minutes. There has been motor block level 2 in just one patient at 40 and 60 minutes after spinal anesthesia. No lower limb motor block was observed in 90% of patients. All patients went from the operating table to the stretcher without any help of the nursing team.

Spinal anesthesia was satisfactory for the procedure in all patients and no patient needed complementation with general anesthesia. There were no blood pressure and heart rate changes, as well as nausea and vomiting. No patient presented with urinary retention or post-dural puncture headache. There have been no reports on back, breeches or legs pain which could be classified as transient neurological symptoms, and there have also not been late neurological complications. All patients have classified their satisfaction with the technique as excellent.



Anesthetic technique of choice for anorectal procedures in several hospitals is regional anesthesia, such as spinal anesthesia or caudal block, which may be undesirable when patients are to be discharged within a few hours. Low hypobaric bupivacaine doses (6 mg) injected in the rate of 1 mL.15s-1 through 27G Quincke needle have induced posterior spinal anesthesia (sensory) in 90% of patients. Only three patients have presented some level of lower limbs motor block.

By definition, baricity is the ratio between injected solution density and CSF density. Mean CSF density is 1,00059 ± 0,00020 g·mL-1 9. Local anesthetics density may be decreased by water dilution. Bupivacaine at 0.15%, the baricity of which is 0,9954 g·mL-1 a 37 ºC, is hypobaric in all patients 4,5. This fact was confirmed by the presence of sensory roots block in 90% of patients with motor block in just 3 patients, when spinally administered in the prone position.

A special spinal anesthetic technique was described in 1961 10, in which patients would receive anesthesia in just one limb for orthopedic surgeries, and was called hemi-spinal anesthesia. This technique induces sensory and motor block preferentially on one side.

The dural sac in the vertebral canal is formed by external, dura mater, internal, called pia mater and arachnoid membranes. Spinal cord and nervous radicles involved by pia are located within the dural sac. Posterior radicles form sensory roots and anterior radicles form motor roots. To perform the puncture with patients in the prone position and a pad has to be placed under the abdomen to correct lordosis and increase spinal interspace 11. In our protocol, patients were placed in the prone position with a pad, and dose and type of anesthetics were injected in this position aiming at inducing anesthesia solely in posterior radicles (sensory) thus avoiding anterior radicles blockade (motor). The objective was reached in 90% of patients.

One advantage of minimum motor block observed with this technique was patients' ability to go from the operating table to the stretcher and of early ambulating. Full dose spinal anesthesia induces total motor block with patients' immobility, allowing for hospital discharge only after total blockade recovery. In our study, all patients went from the operating table to the stretcher without help.

7.5 mg of 0.15% bupivacaine associated to fentanyl has promoted blockade recovery in 2.94 hours 4, similar to 2.96 hours obtained with 6.1 mg of  0.18% bupivacaine 12. Decreasing the dose to 5 mg of 0.15% bupivacaine has promoted recovery time of 2.32 hours, or 20% less 5. In our study, the blockade of sensory roots only, observed in 90% of patients, has decreased recovery time to 2.20 hours, approximately 7 minutes less than the other study 5, allowing immediate ambulation and hospital discharge after meeting discharge criteria.

Urinary retention is a well-known complication of anorectal surgeries, especially hemorrhoidectomy 13-15 with mean incidence of 15% and affecting 1% to 52% of patients. Its exact etiology is not known. It has been correlated to detrusor muscle dysfunction or urethral spasm secondary to pain and to remaining sacral parasympathetic nerve block. There has been no urinary retention in our study.

The incidence of post-dural puncture headache should not be a limiting factor for choosing spinal anesthesia if fine needles are used. Our study has used 27G needles and this complication has not been observed.

It has been shown a major difference (33%) in the incidence of temporary neurological symptoms after high hypobaric bupivacaine doses as compared to low doses (3.6%) for knee surgeries 16. No temporary neurological symptoms were observed in this group of patients after low hypobaric bupivacaine doses. Another factor which might have contributed to the absence of these symptoms in our study was the prone position for the surgery. Other authors have suggested that positioning during surgery may contribute to temporary neurological symptoms, especially the lithotomy position and during knee procedures 17,18.

Hypotension during neuraxial block is caused by vasodilation, with predominance of venous dilation and consequent decrease in venous return and cardiac output. The level of hypotension is related to the level of the blockade. Head-down position during surgery may have also contributed to prevent hypotension. Since sympathetic nervous systems goes to L2 and sensory block was installed only in lumbosacral and lower chest regions without total motor block, this could have been one factor contributing for the lack of hypotension, which if present, would be treated with vasopressants.

Our study has concluded that low hypobaric bupivacaine doses may have several advantages, especially for outpatient procedures, such as fast recovery, hemodynamic stability, decreased risk for temporary neurological symptoms, and patients' satisfaction.



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Correspondence to
Dr. Luiz Eduardo Imbelloni
Address: Av. Epitácio Pessoa, 2356/203 Lagoa
ZIP: 22471-000 City: Rio de Janeiro, Brazil

Submitted for publication March 3, 2004
Accepted for publication June 28, 2004



* Received from Instituto de Anestesia Regional, São José do Rio Preto, SP

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