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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094On-line version ISSN 1806-907X

Rev. Bras. Anestesiol. vol.54 no.5 Campinas Sept./Oct. 2004 



Unilateral spinal anesthesia with low 0.5% hyperbaric bupivacaine dose*


Raquianestesia unilateral con baja dosis de bupivacaína a 0,5% hiperbárica



Luiz Eduardo Imbelloni, TSA, M.D.I; Lúcia Beato, TSA, M.D.II; José Antônio Cordeiro, M.D.III

IDiretor do Instituto de Anestesia Regional, Anestesiologista da Casa de Saúde Santa Maria e Clínica São Bernardo. Rio de Janeiro
IIAnestesiologista da Casa de Saúde Santa Maria e Clínica São Bernardo. Rio de Janeiro
IIIProfessor Livre Docente na FAMERP





BACKGROUND AND OBJECTIVES: Unilateral spinal anesthesia may be advantageous, especially for outpatient procedures. Low anesthetic doses, pencil point or cutting point needles, slow injection rate and the lateral position have been reported as helping unilateral spinal anesthesia technique. This longitudinal study aimed at investigating the depth of unilateral spinal anesthesia with 5 mg of 0.5% hyperbaric bupivacaine injected with 27G Quincke needle with patients in the lateral position and limb to be operated on facing downward.
METHODS: Spinal anesthesia with 0.5% bupivacaine and 27G Quincke needle was induced in 30 patients physical status ASA I-II submitted to orthopedic surgeries. Spinal puncture was performed with patients previously placed with the side to be operated on facing downward and 5 mg of 0.5% hyperbaric bupivacaine were injected at 1 mL.15s-1. Sensory and motor blocks (pinprick and 0 to 3 scores) were compared between operated and contralateral sides.
RESULTS: Motor and sensory blocks between operated and contralateral sides were significantly different in all moments. Unilateral spinal anesthesia was obtained in 85.7% of patients. There has been hemodynamic stability in all patients. No patient has developed post dural puncture headache.
CONCLUSIONS: In the conditions of our study, 0.5% hyperbaric bupivacaine (5 mg) has provided predominantly unilateral block. Twenty minutes were enough for blockade installation. Major unilateral spinal anesthesia advantages are hemodynamic stability, patients’ satisfaction and faster anesthetic recovery.

Key Words: ANESTHETICS, Local: hyperbaric bupivacaine; ANESTHETIC TECHNIQUES, Regional: unilateral spinal


JUSTIFICATIVA Y OBJETIVOS: La raquianestesia unilateral pode presentar ventajas, principalmente en pacientes ambulatoriales. Bajas dosis de la solución anestésica, agujas punta de lápiz o punta cortante, lenta velocidad de inyección y la posición lateral han sido relatados como facilitadores de la producción de raquianestesia unilateral. El presente estudio longitudinal investiga el grado de raquianestesia unilateral utilizando 5 mg de bupivacaína a 0,5% hiperbárica inyectada a través de aguja 27G tipo Quincke en el paciente en decúbito lateral, con miembro a ser operado vuelto para abajo.
MÉTODO: Raquianestesia con 0,5% de bupivacaína fue realizada a través de aguja 27G Quincke en 30 pacientes estado físico ASA I y II sometidos a cirugías ortopédicas. La punción subaracnóidea fue realizada con el paciente previamente colocado con el lado a ser operado vuelto para abajo y fueron inyectados 5 mg de bupivacaína a 0,5% hiperbárica en la velocidad de 1 ml.15s-1. Bloqueos sensitivo y motor (picada de aguja y escala de 0 a 3) fueron comparados entre los lados a ser operados y el contralateral.
RESULTADOS: Los bloqueos motor y sensitivo entre el lado operado y el contralateral fueron significativamente diferentes en todos los momentos. Raquianestesia unilateral fue obtenida en 85,7% de los pacientes. Estabilidad hemodinámica fue observada en todos los pacientes. Ningún paciente desenvolvió cefalea pós-raquianestesia.
CONCLUSIONES: En las condiciones de este estudio la bupivacaína hiperbárica a 0,5% (5 mg) proporcionó un predominante bloqueo unilateral. Veinte minutos fueron suficientes para la instalación del bloqueo. Las principales ventajas de la raquianestesia unilateral son la estabilidad hemodinámica, la satisfacción del paciente y recuperación mas rápida de la anestesia.




Anesthesiologists often act on procedures involving just one lower limb, especially in short orthopedic surgeries. Unilateral spinal anesthesia may show advantages for these procedures as compared to conventional spinal anesthesia, which are: lower incidence of hypotension, fast blockade recovery and increased patients’ satisfaction 1-3. Anesthetic injection in the lateral position, low anesthetic doses, direction of pencil point or cutting point needles and slow injection rate have been suggested to induce unilateral spinal anesthesia 1-5. For this purpose, hypobaric 1,2,6-8, isobaric 3,9 and hyperbaric 5,10-13 solutions have been used to induce unilateral spinal anesthesia.

This study aimed at evaluating the possibility of asymmetric spinal anesthesia distribution with low hyperbaric bupivacaine doses and at comparing results of both limbs and the incidence of hypotension during the proposed anesthetic approach.



After Clinicas Publication and Disclosure Board of Directors approval and informed patient consent was obtained, participated in this prospective study 30 patients physical status ASA I and II, aged 20 to 51 years, to be submitted to elective orthopedic surgeries involving just one limb. Exclusion criteria were hypovolemia, coagulation disorders, infection and patients’ refusal. Monitoring included noninvasive blood pressure, heart rate and pulse oximetry. Patients were not premedicated. Venoclysis with lactated Ringer’s was installed at operating room arrival and 100 µg fentanyl associated to 10 mg metoclopramide were intravenously injected.

Patients were placed in the lateral position with the limb to be operated on facing downward. Spine was horizontally positioned before spinal puncture and table was leveled in the horizontal position (zero) during the procedure. Spinal puncture was paramedially performed at L3-L4 interspace with 27G Quincke needle (B. Braun). 5 mg of 0.5% hyperbaric bupivacaine were injected with the bevel facing downward at the rate of 1 mL.15s-1. Patients were maintained in this position for 20 minutes and then placed in the supine position.

Sensory block was evaluated by the loss of cold feeling (ice) and 27G pinprick, while motor block was evaluated by modified Bromage scale (0 = no motor block to 3 = total motor block). Sensory and motor blocks were evaluated on both limbs at 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 as compared to baseline, while bradycardia was defined as HR below 50 bpm. Hypotension would be treated with 5 mg intravenous ethylenephenylephrine and bradycardia with 0.5 mg intravenous atropine. A pneumatic tourniquet was inflated during the procedure with 100 mmHg above systolic blood pressure. A flow of 2 L.min-1 oxygen was administered via nasal catheter or Hudson’s mask. Midazolam (1 to 2 mg) was administered after the second evaluation (40 minutes).

Patients were followed up until the third postoperative day to obtain information about their satisfaction with the technique and to look 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 and Kruskal-Wallis non-parametric and signal non-parametric tests were used for comparisons. Significance level was 5%.



Demographics data are shown in table I.

Two male patients (21 and 36 years old) had unsatisfactory sensory and motor blocks and were excluded from the study which was then performed with 28 patients.

Results have shown that the operated limb has reached higher sensory levels as compared to the contralateral limb in all evaluation moments (p < 0.00005). Sensory block spread in the operated limb has varied L4 to T4 with mode equal to T11. Only two patients had contralateral limb sensory block varying T8 to T6 and no patient had sensory block equal to or above in the contralateral limb in all studied moments (Table II). Unilateral sensory block was present in 26 patients (92.8%) and in both limbs in 2 patients (7.2%).

Results have shown that the operated limb has reached more intense motor block as compared to the contralateral limb in all evaluation moments. At 20 minutes, there has been total motor block in 25 out of 28 patients, and motor block level 2 in the operated limb of two patients. No patient presented total motor block in the contralateral limb. At 40 minutes, blockade was the same in the operated limb and there has been motor block level 2 in the contralateral limb of 2 patients and level 1 in 2 patients. There has been unilateral motor block in 24 patients (85.7%).

Spinal anesthesia was satisfactory for all 28 patients and no patient needed general anesthesia complementation. Tourniquet was placed on the thigh of 27 patients and below the knee of one patient. There has been no tourniquet pain complaint. There have been no blood pressure and heart rate changes. No patient has developed post dural puncture headache. No TNS or late neurological complications were observed.

There have been two failures due to insufficient level of anesthesia and new spinal anesthesia was induced with 60 mg of 2% isobaric lidocaine. Remaining patients were happy with the technique. All 24 patients with unilateral spinal anesthesia reported having enjoyed feeling the contralateral limb.



Adequate unilateral spinal anesthesia for lower limbs orthopedic surgery with 5 mg of 0.5% hyperbaric bupivacaine was obtained for all patients, except for the two excluded from the study. Unilateral blockade was obtained in 85.7% of patients. All patients were happy with the technique and there has been no hypotension.

The distance between left and right side roots varies 10 to 15 mm in the lumbar and thoracic region and may provided restricted spinal nerves unilateral block. Several reports have suggested that low hypobaric, isobaric or hyperbaric doses slowly injected may provide unilateral spinal anesthesia if patients remain in the lateral position for 15 to 30 minutes, resulting in spinal anesthesia distribution to the operated side 1-9.

Major reasons for inducing unilateral spinal anesthesia are to prevent hemodynamic changes and induce motor block to improve patients’ comfort. Several factors influence spinal anesthetic spread 14: CSF volume, local anesthetic baricity, patients’ position during and after injection, anesthetic dose and injection site.

In our study, puncture site, bupivacaine volume and concentration were constant and patients have remained in the lateral position for 20 minutes.

Patients’ position, during and immediately after local anesthetic injection, influences spinal drugs spread. When anesthetic solutions more or less dense than CSF are used, it is theoretically possible to control spinal block spread. The maintenance for a certain period may limit anesthesia to the operated side only.

However, optimum lateral position duration is difficult to define because when high hyperbaric bupivacaine doses (12.5 and 15 mg) 10 or (12 to 20 mg) 15 are used, there is anesthetic migration even when patients remain in the lateral position for 30 minutes 10 to 1 hour 15. Conversely, if low anesthetic doses (5 to 8 mg of 0.5% hyperbaric bupivacaine) are used, 10 to 15 minutes in the lateral position are enough to prevent anesthetic migration when patients are placed in the supine position 11,12,16. In our study, 5 mg of 0.5% hyperbaric bupivacaine and 20 minutes in the lateral position have resulted in unilateral spinal anesthesia in 85.7% of patients, with migration in two patients only.

Spinal anesthesia duration depends not only on the local anesthetic, but also on the dose. The use of 6, 8 and 10 mg of 0.75% hyperbaric bupivacaine and the maintenance of the lateral position result in mean analgesia duration of 93, 123 and 147 minutes, respectively 17. In our study, longest time between injection and surgery completion has been 2.30 hours, similar to the same dose of 0.15% hypobaric bupivacaine, which has been 2.32 hours 2 and of 0.5% isobaric bupivacaine, which has been 2.34 hours 3.

Decreased local anesthetic dose is a major factor for surgical anesthetic induction in the operated side and may affect spinal anesthesia success. Unilateral spinal anesthesia has been firstly described with 4 to 5 mg hyperbaric tetracaine 4. In this study, 5 mg of 0.5% hyperbaric bupivacaine had an incidence of 6.6% failures, differently from previous studies with the same dose of 0.15% hypobaric bupivacaine 2 and 0.5% isobaric bupivacaine 3, where no failures have been observed.

Most common spinal anesthesia needles are non-cutting pencil point needles (Whitacre and Sprotte) and cutting-type needles (Quincke). Pencil point needles have a lateral opening resulting in a different anesthetic flow as compared to cutting tip needles, which have a terminal opening. Similar to previous studies 1-3, Quincke needles have been chosen for allowing fast CSF appearance 18 and low incidence of headache 19.

Major unilateral spinal anesthesia advantage as compared to bilateral spinal anesthesia is hemodynamic stability. The first study on unilateral spinal anesthesia has reported an incidence of 18% hypotension as compared to 50% with bilateral spinal anesthesia 4. Skin temperature evaluated on the foot is a simple method to determine sympathetic function. Temperature increases as result of venous dilatation induced by sympathetic block.

In two recent studies 21,22, skin temperature has shown that bilateral sympathetic block may be prevented in 70% of patients if hyperbaric bupivacaine is slowly injected in low doses. One objective of unilateral spinal anesthesia is to decrease hypotension, which may be present with spinal anesthesia, fact confirmed when conventional spinal anesthesia was compared to asymmetric spinal anesthesia 22.

Hyperbaric solutions for unilateral spinal anesthesia have an incidence of 10% 12 to 20% 23 hypotension, regardless of injection rate. With 7.5 and 10 mg of 0.5% hyperbaric bupivacaine and successful unilateral spinal anesthesia, no hypotension has been observed 12, fact confirmed by this study with 5 mg of 0.5% hyperbaric bupivacaine.

The regression of two segments with low 0.5% hyperbaric bupivacaine doses varies 67 22 to 99 23 minutes. We have not evaluated the regression of two segments, but rather total motor block recovery which has varied 1.75 to 3.25 hours. So, 5 mg hyperbaric bupivacaine may be a good indication for outpatient procedures.

Pencil point needle and slow injection are factors contributing for transient neurological symptoms, especially when hyperbaric lidocaine is used 24. With cutting point and hyperbaric bupivacaine, no transient neurological symptoms were seen in this study, what is in line with other authors 11,25, who have evaluated the influence of 0.5% hyperbaric bupivacaine injection rate on lateral distribution.

In conclusion, in the conditions of this study, unilateral blockade has been obtained in 85.7% of patients when 5 mg hyperbaric bupivacaine were used. Major unilateral spinal anesthesia advantages are high cardiocirculatory stability, patients’ satisfaction in remaining with an unblocked limb and faster anesthetic recovery.



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

Submitted for publication September 22, 2003
Accepted for publication January 20, 2004



* Received from Instituto de Anestesia Regional da Faculdade de Medicina de São José do Rio Preto (FAMERP), São José do Rio Preto, SP

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