Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.57 no.6 Campinas Nov./Dec. 2007
LETTER TO THE EDITOR
Postoperative analgesia for orthopedic surgeries of the hip and femur: comparison between psoas compartment and inguinal perivascular blocks
I would like to thank the Editor the opportunity to make a few comments to clarify the study mentioned above 1.
Major orthopedic surgeries, such as partial or total prosthesis of the hip and total prosthesis of the knee, are common in the elderly, while osteosynthesis of the femur, with or without bone graft, usually from the anterior superior iliac crest (ASIC), are more common in young patients, usually after motor vehicle accidents. In the immediate postoperative period of all those procedures, regional analgesia, with or without a catheter, provides fast and qualified recovery of the patients. The long study of Imbelloni et al. analyzes post-operative analgesia (POA) at rest, although in elderly patients, analgesia associated with respiratory therapy and early mobilization of operated limbs2,3 should also be a priority due to the consequences of immobilization. However, some aspects were not very clear 1.
1. Analgesia Comparing Table III Pain Scale at the Different Moments, with Table IV Number of Patients with Sensitive Blockade of the Different Nerves in the First 24 Hours of the Postoperative Period and the text corresponding to the moment 12 hours, we face an incoherence: in Table III, Group 1 and Group 2 presented analgesia in 96 (pain scale of zero) and 83 (pain scale of zero) patients, respectively and, therefore, one supposes a blockade of the five nerves involved. However, in Table V, moment 12 hours recorded sensitive blockade of the five nerves in 76 patients in Group 1 and two patients in Group 2.
2. Volume of anesthetic and the obturator nerve On the contrary to the use of catheters that reach the small pelvis or parasacral and lumbar paravertebral regions, the course of the obturator nerve, the dispersion of 40 mL of anesthetic solution with one injection does not necessarily reach those places 4. Detection of the anesthesia of this nerve is not restricted to the determination of cutaneous sensibility 5, but to the function of the adductor muscles of the thigh. Testing peripheral sensitivity to evaluate the compromise of the obturator nerve in anterior lumbar plexus block is a mistake and should be abandoned because of its random cutaneous expression. It is only justified in superficial incisions of the medial aspect of the thigh that do not affect the musculature (postoperative painful reflex contraction of thigh adductors). Bouaziz et al. verified, in 30 patients, absence of cutaneous innervation in the territory of the obturator nerve in 57% of the cases, hypoanesthesia in 23% and only 20% with cutaneous sensorial deficit. The proper procedure would be to test voluntary movements of the thigh adductors. However, this is not recommended in the postoperative period of hip surgeries due to possible subluxation of the joint since adduction is often associated with internal rotation of the thigh. In contrast, posterior lumbar plexus block with the final position of the needle in the virtual compartment between the psoas major and quadratus lumborum muscles or inside the major psoas muscle are more likely to reach the obturator nerve. Biboulet et al. 6 that tested the cutaneous sensitivity of the obturator nerve and not the adductors muscles of the thigh, after anterior lumbar block with up to 36.5 mL of 0.375% ropivacaine, identifying wrong results regarding this nerve, and concluded that postoperative regional peripheral analgesia should not be routinely used in those cases.
3. Compromised dermatomes and sclerotomes In surgeries in the region of the ASIC, especially for donation of bone grafts, what really bothers the patient and hinders immobilization are: the dermatome of incision, i.e., the cutaneous aponeurotic segment with innervation mainly from the terminal cutaneous branches of T12, and not from the iliohypogastric nerve (T12-L1), and the myotome corresponding to the external oblique muscle (T12) 7. The sclerotome of the ASIC 7 has less postoperative nociceptive participation due to the absence of the periosteum (surgically removed) and for being incapable of mobilization. In those cases, I usually infiltrate the subcutaneous tissue, reaching the terminations of T12 and the iliohypogastric nerve (T12-L1), with a long action local anesthetic before the surgical dressing, because the anesthetic solution of the anterior lumbar plexus block does not guarantee anesthesia/analgesia of the T12 and L1 roots. In general, this is enough for a good postoperative analgesia, although, at times, multimodal analgesia associated with NSAIDs and minor analgesics provides better analgesia. However, a report published recently stressed the need to block other sacral peripheral nerves to obtain postoperative analgesia in hip surgeries 2.
4. Innervation of the lower limb The description of the innervation of the upper segment of the leg, as mentioned, corresponds to that of the thigh. It was obviously an involuntary typing error.
5. Radiological studies Radiographic images 30 minutes after administration of contrast, when it is not completely absorbed, does not produce precise opaque densities by the process of absorption, leading to erroneous identification with bone limits. Figure 1 1 shows the wrong interpretation of the non-ionic contrast. Besides, instead of being printed horizontally, it should be vertically, with the needle to the left side of the figure.
Finally, I would like to congratulate the authors on the size of the study population (n = 200) without central, epidural, or subarachnoid blockade, a collateral effect by extension.
Dr. Karl Otto Geier,
Porto Alegre, RS
01. Imbeloni LE, Beato L, Beato C et al. Analgesia pós-operatória para procedimentos cirúrgicos ortopédicos de quadril e fêmur: comparação entre bloqueio do compartimento do psoas e bloqueio perivascular inguinal. Rev Bras Anestesiol, 2006;56:619-629.
02. Ambulkar R, Shankar R Analgesia after total hip replacement. Anaesthesia,2006;61;507.
03. Chelly JE, Casati A, Al-Samsam T et al. Continuous lumbar plexus block for acute postoperative pain management after open reduction and internal fixation of acetabular fractures. J Orthopaedic Trauma, 2003;17:362-367.
04. Geier KO Bloqueio "3 em 1" por via anterior: bloqueio parcial, completo ou superdimensionado? Correlação entre anatomia, clínica e radioimagens. Rev Bras Anestesiol, 2004;54:560-572.
05. Bouaziz H, Vial F, Jochum D et al. An evaluation of the cutaneous distribution after obturator nerve block. Anesth Analg, 2002;94:445-449.
06. Biboulet P, Morau D, Aubas P et al. Post-operative analgesia after total-hip arthroplasty: comparison of intravenous patient-controlled analgesia with morphine and single injection of femoral nerve or psoas compartment block. A prospective, randomized double-blind study. Reg Anesth Pain Med, 2004;29:102-109.
07. Netter FH Atlas of Human Anatomy. 9th Ed. East Hanover, New Jersey, Novartis, 1997; 467, plate 250.