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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.57 no.5 Campinas Sept./Oct. 2007
Control of postoperative pain following total knee arthroplasty: is it necessary to associate sciatic nerve block to femoral nerve block?*
Control del dolor postoperatorio de la artroplastia total de la rodilla: ¿es necesario asociar el bloqueo del nervio isquiático al bloqueo del nervio femoral?
Affonso H. Zugliani, TSAI; Nubia VerçosaII; José Luiz Gomes do Amaral, TSAIII; Louis BarrucandIV; Cátia Salgado, TSAV; Márcia Borges Hage KaramV
do Curso de Pós-Graduação em Cirurgia Geral Área
de Concentração: Anestesia e Analgesia Nível Mestrado
da Faculdade de Medicina da UFRJ; Chefe do Serviço de Anestesiologia
do MS/INTO; Responsável pelo CET/SBA do HM Souza Aguiar
IIProfessora Associada Mestre e Doutora em Medicina do Departamento de Cirurgia da FM/UFRJ; Coordenadora da Graduação e Pós-Graduação em Anestesiologia da FM/UFRJ; Responsável pelo Ambulatório de Avaliação Pré-Anestésica do Hospital Universitário Clementino Fraga Filho HUCFF-FM/UFRJ; Certificado de Área de Atuação em Dor SBA/AMB
IIIProfessor Titular da Disciplina de Anestesiologia, Dor e Terapia Intensiva da Universidade Federal de São Paulo (UNIFESP); Presidente da Associação Médica Brasileira
IVProfessor Titular de Patologia do Departamento de Anatomia Patológica da FM/UFRJ
VAnestesiologista do MS-INTO
BACKGROUND AND OBJECTIVES: Total knee arthroplasty (TKA) causes severe
tissue trauma, leading to severe postoperative pain. Good postoperative analgesia
is fundamental and one should consider that early mobilization of the joint
is an important aspect to obtain good results. There is a controversy in the
literature on the efficacy of isolated femoral nerve block. The objective of
this study was to evaluate postoperative analgesia with the association of sciatic
and femoral nerve block.
METHODS: Seventeen patients undergoing TKA under spinal anesthesia were divided in two groups: A and B. In Group A (n = 9), femoral nerve block was performed, while in Group B (n = 8), femoral and sciatic nerve block were done. The blockades were done in the immediate postoperative period with 20 mL of 0.5% of ropivacaine. Pain was evaluated in the first 24 hours using the Visual Analog Scale and the verbal scale. The length of time between the nerve block and the first complaint of pain (M1) was also evaluated.
RESULTS: The median of the duration of analgesia (M1) in Group A was 110 min, while in Group B it was 1285 min (p = 0.0001). There were no complications related to the technique used.
CONCLUSIONS: Sciatic nerve block, when associated with femoral nerve block, under the conditions of the present study, improved significantly the quality of postoperative analgesia in TKA.
Key Words: ANALGESIA: postoperative; ANESTHETIC TECHNIQUES, Regional: femoral nerve block, sciatic nerve block; SURGERY, Orthopedic: total knee arthroplasty.
JUSTIFICATIVA Y OBJETIVOS: La artroplastia total de la rodilla (ATR)
promueve gran trauma del tejido produciendo un intenso dolor en el postoperatorio.
La analgesia de postoperatorio de buena calidad es fundamental, debiendo considerar
que la movilización articular precoz es un importante aspecto para la
obtención de buenos resultados. Existen controversias en la literatura
sobre la eficacia del bloqueo aislado del nervio femoral. El objetivo de este
estudio fue evaluar la analgesia en postoperatorio con la asociación
del bloqueo de los nervios isquiático y femoral.
MÉTODO: Fueron estudiados 17 pacientes sometidos a ATR bajo raquianestesia, divididos en dos grupos: A y B. En el Grupo A (n = 9) fue realizado bloqueo del nervio femoral y en el Grupo B (n = 8) bloqueo de los nervios femoral e isquiático. Los bloqueos fueron realizados en el postoperatorio inmediato utilizando 20 mL de ropivacaína a 0,5% en cada uno. El dolor se comprobó en las primeras 24 horas a través de la Escala Analógica Visual y escala verbal. Fue observado el tiempo transcurrido entre los bloqueos y el primer quejido de dolor (M1).
RESULTADOS: La mediana del tiempo de analgesia (M1) en el Grupo A fue de 110 min y en el Grupo B de 1.285 min (p = 0,0001). No fueron observadas complicaciones atribuibles a las técnicas utilizadas.
CONCLUSIONES: El bloqueo del nervio isquiático, cuando se asocia al bloqueo del nervio femoral, e las condiciones de este estudio, mejoró de manera significativa la calidad de la analgesia en postoperatorio de la ATR.
Total knee arthroplasty (TKA) involves extensive tissue trauma 1, contributing to the development of severe postoperative pain 2, making analgesia in this phase very important 3. One should also consider that physical therapy with early joint mobilization is an important aspect to achieve good results 2,4. The regular use of non-steroidal anti-inflammatory drugs (NSAIDs) and opioids do not provide satisfactory analgesia 3,5. Morphine or local anesthetics injected in the neuro axis have known side effects 2,3,6, demanding constant vigilance. Several studies have demonstrated that peripheral nerve block in the knee area could be used as an alternative to analgesia, and the low morbidity of those techniques should be considered. There is a consensus regarding the benefits of femoral nerve block to the patient 2,7-10, due to its predominance in the innervation in this area. However, there is a controversy in the literature regarding the need to block the other nerves, especially the sciatic and obturator nerves, to obtain complete analgesia 11-13. The objective of this study was to evaluate whether the association of sciatic nerve block with femoral nerve block is necessary to obtain good postoperative analgesia in total knee arthroplasty. The duration of the analgesia and the complications of the blockades were also evaluated.
After approval by the Ethics Committee on Research of the Instituto Nacional de Traumatologia e Ortopedia (INTO), 20 patients undergoing primary total knee arthroplasty (TKA) were enrolled in the study. All procedures were performed at INTO and patients were evaluated beforehand at the Anesthesiology Clinic and agreed formally to participate in the study. On the eve of the surgery, patients were informed about the tests to evaluate pain and that they should communicate promptly the occurrence of pain.
In the operating room, monitoring consisted of non-invasive blood pressure, pulse oximetry, and cardioscope. Fractionated doses of midazolam or diazepam and a full dose of fentanyl, up to 100 µg, were used for pre- and intraoperative sedation. All surgeries were done under subarachnoid anesthesia with isobaric bupivacaine.
Inclusion criteria included: age between 40 and 75 years; BMI between 18 and 36; weight between 50 and 100 kg; and physical status ASA I, II, and III. Non-cooperative patients, those with cognitive incapability of evaluating the pain scale and to provide information, with neuromuscular diseases or peripheral neuropathies, with fixed valgus greater than 15°, and other contraindications to the techniques proposed, were excluded.
Patients were randomly divided in two groups. Group A had femoral nerve block. After the administration of the local anesthetic, a perineural catheter was introduced for possible future injections, if needed. Group B had the procedures performed in Group A associated with sciatic nerve block with a single dose of the local anesthetic.
The technique of Winnie was used for the femoral nerve block 14: access puncture 1 to 2 cm below the inguinal ligament and 1 to 2 cm lateral to the femoral artery. The needle was introduced at a 30° to 45° angle, cephalad. The device Contiplex® (B.Braun-Melsungen) for continuous blocks was used, allowing the localization of the nerve, through neurostimulation, and introduction of the perineural catheter. Contractions of the quadriceps muscle, with movements of the patella, were considered a satisfactory response to a stimulus of 0.5 mA, 1 Hz of frequency, and 0.2 ms, to determine the localization of the femoral nerve. Twenty milliliters of 0.5% ropivacaine without vasoconstrictor were injected. The sciatic nerve block was done by the anterior approach, according to the Beck technique 15, and the puncture was done at the intersection of the perpendicular line from the junction of the proximal and medial thirds of the inguinal ligament with the line parallel to this ligament originating from the major trochanter. An isolated Stimuplex A-150® or A-100® (B.Braun Melsungen) needle was used, and plantar flexion or dorsal flexion of the foot to stimuli of 0.5 mA, 1 Hz of frequency, and duration of 0.2 ms, was considered a good response in determining its position. Twenty milliliters of 0.5% ropivacaine without vasoconstrictor were injected.
Intravenous dypirone (30 mg.kg-1) every 4 hours, for the first 24 hours, was used as adjuvant to postoperative analgesia in all patients. Pain evaluation was done after the patient was admitted to the recovery room by an anesthesiologist who was unaware of the anesthetic procedure performed. The visual analog scale with 10 points (0 equal to absence of pain and 10 was the worst pain possible) and the verbal scale with 5 grades (absence of pain; mild pain; moderate pain; severe pain; and unbearable) were used to evaluate the intensity of pain.
When pain at rest or with passive mobilization of the knee to a 30° angle was above 3 or equal or greater than moderate pain in the first 6 hours, sciatic nerve block was done in the patients in Group A. Patients in Group B received subcutaneous nalbuphine (0.1 mg.kg-1) every 6 hours.
In case of pain above 3, or equal or greater than moderate pain, more than 6 hours after the femoral nerve block, 20 mL of 0.5% ropivacaine was administered through the catheter to patients in both groups. If the pain persisted, subcutaneous nalbuphine (0.1 mg.kg-1) was administered every 6 hours (up to 10 mg).
Evaluation of postoperative pain was done every two hours by the anesthesiologist, in the first eight hours in the recovery room and until the end of the 24-hour period. Other regular evaluations were done by the nursing staff of the ICU (Intensive Care Unit) the patient was transferred to.
M1 was defined as the length of time, in minutes, between the femoral nerve block, in Group A, or femoral and sciatic nerve block in Group B, and the first complaint of pain > 3 or equal or higher than moderate pain. M2 was defined as the length of time, in minutes, between the sciatic nerve block, in six patients in Group A, who presented early complaints of pain and the new complaint of pain again.
The size of the study group was based on data found in the literature and clinical observation of the author. Initially, it was proposed the inclusion of 38 patients; however, after the partial analysis of the first 20 cases, a decision was made to interrupt data gathering for ethical reasons.
The Student t test and Mann-Whitney test were used for the statistical analysis of the results. It was chosen a level of significance of 5% (p < 0.05).
Of the 20 patients, three were excluded: one in Group A, who became disoriented after 12 hours, and two in Group B, one for complaints of pain upon arrival to the recovery room and the other for complaining of pain after regression of the subarachnoid anesthesia, even though sciatic and femoral nerve blocks were present. Therefore, Group A had nine patients and Group B had eight. The demographic data was similar in both groups regarding age with a mean of 63 ± 6 years in Group A and 67 ± 8 years in Group B. Group A had a body mass index of 31.8 ± 2.9 and 29.2 ± 3.8 in Group B (Table I). All patients studied were classified as ASA II.
The mean length of time of postoperative analgesia (M1) was 110 minutes (min: 50; max: 645) in Group A, and 1285 minutes (min: 990; max: 1510) in Group B and this difference was statistically significant (p = 0.0001) by the Mann-Whitney test (Tables II and III).
Six (66%) of the 9 patients in Group A experienced pain > 3 or equal or higher than moderate pain in the first hours, when the sciatic nerve block was done, leading to effective analgesia that had a mean duration of 1027.5 minutes (17.1 hours M2).
The remaining patients did not complain of pain in the first 6 hours after the femoral nerve block, and the mean duration of the initial analgesia (M1) was 485 minutes (8 hours). When those patients complaint of pain, it was effectively controlled in two of them with the administration of 0.5% ropivacaine (20 mL) through the perineural femoral catheter, and the third received nalbuphine for failure of the anesthetic injected through the catheter.
As for patients in Group B (n = 8), in four, pain was controlled after the first complaint with a bolus injection of the anesthetic through the femoral catheter; one of them received nalbuphine due to failure of obtaining analgesia after the injection through the catheter; and three did not complaint of pain at the 24-hour evaluation.
There were no neurological complications, hematoma formation or pain on the site of the punctures, as well as signs of systemic intoxication caused by the local anesthetic.
Two patients in each group experienced nausea and vomiting.
Transitory hypotension occurred in one patient in Group A, 30 minutes after the femoral block, and one in Group B, 20 minutes after the femoral and sciatic nerve block.
Surgery lasted a mean of 132 minutes in Group A, and 116 min in Group B. The mean dose of isobaric bupivacaine used for the subarachnoid anesthesia was 17.4 mg in Group A and 18.2 mg in Group B.
The femoral nerve predominates in the innervation of the knees. The role of the sciatic and obturator nerves, through their radicular branches, seems to vary in each individual. The areas of cutaneous innervation of those nerves, which might not be constant in the case of the obturator nerve, as well as the cutaneous femoral posterior, are not involved. Studies have demonstrated the benefits of the femoral nerve block in controlling postoperative pain in total knee arthroplasty (TKA), reducing the consumption of systemic opioids and consequently their side effects. These advantages are evident when compared with other alternatives, such as the administration of intravenous morphine, controlled by the patient 2, in regular doses 8, or injected in the neuroaxis 6. The incidence of side effects is even greater when compared with the continuous epidural administration of local anesthetics 2 in which, besides the bilateral motor and sensitive blockade, it can also cause hypotension and postural hypotension due to sympathetic blockade.
However, despite the suppression of pain in areas innervated by the femoral nerve, supplemental doses of opioids are often necessary for effective sedation in most patients. Wang7 observed a mean consumption of 0.38 mg.kg-1 of morphine in the first 24 hours in a group of 15 patients, and Singelyn 2,16 used the opioid piritramide. The addition of clonidine and/or opioid to the anesthetic solution in continuous perineural femoral block resulted in analgesia of high quality. It is possible that the systemic effects of those drugs contributed for these results. The association of sciatic and femoral nerve block has been advocated by some authors 3,4,12,17-19. Allen 11, studying 36 patients divided in three groups compared the femoral nerve block (G1) to the femoral nerve block associated with sciatic nerve block (G2) and a control group (G3). Intravenous morphine was administered immediately after the blockades. The results were similar between the first two groups, leading the authors to recommend the use of the femoral nerve block alone. The short duration of analgesia (8 hours) could be attributed to the low concentration of the local anesthetic used (single dose of 0.25% bupivacaine). The use of intravenous morphine could be another confusing factor.
In this study, according to the results of Group A, only three out of nine patients (33%) achieved adequate analgesia with the isolated femoral nerve block. In those patients, the mean duration of analgesia after the initial dose of ropivacaine was 8 hours and was reinstituted on demand in two patients, after injection of a new dose of the local anesthetic through the catheter. In one of them it was necessary to administer intravenous nalbuphine, probably due to inadequate positioning of the catheter, which was difficult to advance when it was introduced. This seems to demonstrate the wide dissemination of this nerve, and the minimal participation of the other nerves, in the sensitive supply of the knee. The remaining six patients (66%) complained of pain in the first three postoperative hours, coinciding with the regression of the anesthesia of the neuroaxis, at which time the sciatic nerve block was done. These data are similar to the study of Weber 17, who demonstrated the need of this blockade in 67% of the 36 patients in the study treated with continuous femoral nerve block and the results of BenDavid 19 in 10 out of 12 patients undergoing TKA.
We observed that the patients in Group A, who received sciatic nerve block, that from that point on, the mean duration of analgesia (M2) was 17 hours, close to Group B, with a mean of 23 hours, demonstrating the importance of its sensitive component in the region involved.
Using a single dose of 0.5% bupivacaine to block the sciatic and femoral nerves in 22 patients in the postoperative period of open knee surgeries, Misra et al. 20 found that it took a mean of 17 hours before the first request for analgesia. Cook 18 observed a 61% reduction in the consumption of morphine in the first 24 hours in a group of 67 patients who had femoral and sciatic nerve block (0.35 mg.kg1), in a single dose, when compared with 30 patients who were treated only with femoral nerve block (0.58 mg.kg1). In this study, patients were not randomly divided; 0.5% bupivacaine or 0.7% ropivacaine were used. The impossibility to maintain the femoral nerve block might have caused the increased morphine consumption. Werber 17 observed the use of morphine in the first 24 hours in only 25% of the patients with sciatic and femoral nerve block, and the last one was maintained with the use of a perineural catheter for bolus injections. Phan-Dang 12 noted an 81% reduction in morphine consumption in the first 36 hours in the group (n = 14) that underwent sciatic and femoral nerve block when compared with the group (n = 14) that received only femoral nerve block. They recommended the use of the catheter both in the femoral and sciatic nerves, but they questioned its cost/benefit ratio and the possibility of intoxication if two continuous infusions are administered. In the present study, there was no evidence of significant pain (> 3) arising from the area innervated by the sciatic nerve, which develops later. This could be caused by the greater duration of its sensitive blockade or to its minor influence in knee sensitivity when compared with the femoral nerve. The bolus administration through the perineural femoral catheter, with a syringe, in case of pain, was effective and could be a low-cost alternative when infusion pumps are not available or infrastructural conditions are not optimal. The doses administered on demand should be prescribed observing the minimal safe intervals, and administered by nurses or physicians properly oriented. Singelyn et al. 16 studied 45 patients receiving three types of infusion through perineural femoral catheters for postoperative analgesia in TKA. They concluded that the bolus administration consumed 58% less bupivacaine when compared with continual injection associated or not with bolus administration, which produced similar analgesia. Eledjan et al. 21 had the same conclusion using the same alternatives. One hundred and thirty-six patients undergoing large surgeries of the knees, including 66 TKA, were studied.
The degree of the motor blockade obtained with 0.5% ropivacaine did not hinder physical therapy in the first 24 hours, according to the physical therapists. Mean hospital stay for both groups (five days) was similar to the mean for this type of surgery in our institution.
The total dose of ropivacaine used to achieve the blockade in both nerves was 200 mg, allowing for the safe administration of extra 100-mg boluses at intervals of at least 8 hours in the first 24 hours. This anesthetic was chosen due to its reduced cardiotoxicity in comparison with other long acting anesthetics available. This is justified considering the age (above 60 years) of most patients undergoing TKA. Misra et al. 20 used a total dose of 3 mg.kg-1 of bupivacaine in 22 patients undergoing concomitant blockade of both the sciatic and femoral nerves. They observed a mean peak plasma concentration of 0.74 µg.mL-1 achieved in approximately 60 minutes. Levels above 2 µg.mL-1 are considered toxic. The same time was achieved by Simon et al. 22, using a mean of 730 mg of mepivacaine in 20 patients, and Elmas et al. 23, with 500 to 650 mg of lidocaine in 45 patients. These data confirm the low rate of absorption of the local anesthetic in those areas 20. On the other hand, bupivacaine produces a toxic, cumulative metabolite, desmethylbupivacaine, which should be considered in the case of continuous infusion 23.
It was difficult to obtain motor responses in three patients when trying to locate the sciatic nerve. This was achieved after trying for 10 to 15 minutes, using maneuvers of rotation of the lower limb around its long axis. When the nerve is under the antero-posterior projection of the femur or the minor trochanter might hinder the access to this nerve. Moore et al. 24, using imaging exams, concluded that in 85% of the cases internal rotation of the lower limb makes access to the nerve easier by the anterior approach. Morin et al. 4 did not get any stimuli in four patients, out of 30, after trying for 15 minutes. This relative difficulty of the anterior approach seems to have dampened its use. However, postoperative bandaging of the limb, which reaches the proximal one third of the thigh, besides the postural maintenance of the patient, makes it the technique of choice for the postoperative period of TKA. The proximity with the area of the femoral block also simplifies the process. Preoperative block by posterior approaches, such as parasacral, subgluteus, or mediofemoral, were proposed by Mansur et al. 25, Ben-David et al. 11, and Phan-Dang et al. 9, respectively. Ben-David et al. 11 defend the sciatic nerve block with long acting local anesthetic only in the postoperative period, after the return of its function. They claim that the diagnosis of an eventual surgical lesion of the nerve could be delayed in the presence of nerve block. Patients with marked, fixed valgus (15°) were excluded from the study. In those cases, realigning the axis of the leg could stretch the fibular nerve, with the consequent lesion, requiring immediate intervention. If nerve blocks are done only in the postoperative period, the communication between the anesthesiologist and the surgeon allows for their delay, in case of surgical problems that justify their use.
A patient excluded (Group B) from the study developed severe pain after regression of the neuroaxis block, although under proven blockade of the sciatic and femoral nerves. After the administration of nalbuphine, without relief, an obturator nerve block was performed, with complete and immediate cessation of pain and the analgesia was maintained for 11 hours. This may indicate the variable influence of this nerve in the sensitive supply of the knee. This was clinically important only in one patient (6%), suggesting that the routine block of this nerve is not necessary. MacNamee et al. 26 achieved more prolonged analgesia and reduce consumption of morphine in the group of 30 patients in which obturator nerve block was associated with femoral and sciatic nerve block, all of them with a single dose, when compared with the group (n = 30) without this association. The study of Morin et al. 4 did not demonstrate any differences in morphine consumption between the group (n = 26) of continuous posterior lumbar plexus block, with inclusion of the obturator nerve, and the group (n = 36) of continuous femoral block. They concluded that the obturator nerve does not have a significant contribution for the development of postoperative pain in TKA. Kaloul et al. 27 reached to the same conclusion regarding morphine consumption using those same techniques in two groups of 20 patients.
The intercurrences observed included two cases of nausea and/or vomiting, of low severity, in each group. A patient in Group A developed systolic hypotension (90 mmHg) 30 minutes after the femoral nerve block. The same happened with one patient in Group B 20 minutes after the nerve block (SBP = 70 mmHg) and bradycardia (48 bpm). In both cases, increasing the infusion of crystalloid and plasma expanders promptly reversed the clinical picture, but 2 mg of ethylephrine was administered intravenously to one of the patients. The lack of other signs and symptoms in those episodes indicates that it is unlikely that they were caused by systemic toxicity of the local anesthetic. The vasodilation after sciatic and femoral nerve block is restricted to the area supplied by these nerves, through their sympathetic branches and, therefore, is not very important. Drainage of blood through the drain in the immediate postoperative period, characteristic of TKA, could have contributed to the development of this intercurrence. However, it was not relevant in those patients.
Interruption of data gathering, after a partial analysis, was a consequence of the marked difference observed between groups A and B. It became evident that patients in Group A would be exposed to unnecessary suffering, which would involve ethical questions.
The results of this study indicate that sciatic nerve block with one single dose of 20 mL of 0.5% ropivacaine associated with femoral nerve block, with the same volume of the same anesthetic solution, improved significantly the quality of postoperative analgesia in TKA.
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Dr. Affonso H. Zugliani
Rua Ipiranga, 32/801 Laranjeiras
22231-120 Rio de Janeiro, RJ
Submitted em 17 de julho de 2006
Accepted para publicação em 25 de junho de 2007
* Received from Instituto Nacional de Traumatologia e Ortopedia (MS-INTO), Rio de Janeiro, RJ