Anesthesia: Essays and Researches

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 13  |  Issue : 3  |  Page : 547--553

Fascia iliaca block as an anesthetic technique for: Acute lower limb ischemia


Maha Ahmed Abo-Zeid1, Reem Abdelraouf Elsharkawy1, Mohamed Farag2, Sameh Hany Emile3,  
1 Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Mansoura University, Mansoura, Egypt
2 Department of Vascular Surgery, Faculty of Medicine, Mansoura University, Mansoura, Egypt
3 Department of General Surgery, Faculty of Medicine, Mansoura University, Mansoura, Egypt

Correspondence Address:
Reem Abdelraouf Elsharkawy
Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Mansoura University, Mansoura
Egypt

Abstract

Purpose: The purpose of this study is to evaluate the efficacy of preoperative fascia iliaca block (FIB) as a sole anesthetic technique in transfemoral thromboembolectomy of unilateral acute lower limb ischemia compared to unilateral spinal anesthesia (SA) as a primary outcome. Hemodynamic variation, postoperative pain score, and the first demand for analgesia with the total postoperative analgesic required in the 1st postoperative day were considered as the secondary outcome. Patients and Methods: This prospective randomized controlled study included two groups of patients aged between 40 and 70 years, who underwent transfemoral thrombectomy for acute unilateral lower limb ischemia. Patients in the spinal group (SA) (n = 56): underwent unilateral SA using 10 mg bupivacaine 0.5% and patients in the group FIB (n = 56): received FIB with 30 mL of 0.25% bupivacaine. Sensory block was evaluated over the incisional area with 3-point scale. If the sensory block did not reach zero grade after 30 min, the patient received general anesthesia. Results: The incidence of the successful block was 100% in the SA group compared to 80.35% in the FIB group. There was a significant decrease in recorded heart rate and mean blood pressure within the SA group at 3, 10, and 20 min and 3, 20, and 45 min, respectively. Values of visual analog scale decreased significantly in SA group compared to that of the FIB group immediately and 1 h postoperative. However, the time for the first postoperative analgesic requirement and morphine consumption was comparable between the groups. Conclusion: Preoperative FIB could be considered as a promising alternative anesthetic technique to SA with better hemodynamic parameters in patients undergoing transfemoral thrombectomy for acute lower limb ischemia. It could be also due to limited precautions considered the first choice over SA for patients on perioperative anticoagulants.



How to cite this article:
Abo-Zeid MA, Elsharkawy RA, Farag M, Emile SH. Fascia iliaca block as an anesthetic technique for: Acute lower limb ischemia.Anesth Essays Res 2019;13:547-553


How to cite this URL:
Abo-Zeid MA, Elsharkawy RA, Farag M, Emile SH. Fascia iliaca block as an anesthetic technique for: Acute lower limb ischemia. Anesth Essays Res [serial online] 2019 [cited 2019 Nov 21 ];13:547-553
Available from: http://www.aeronline.org/text.asp?2019/13/3/547/260443


Full Text

 Introduction



Neuraxial anesthesia (spinal or epidural) is commonly used for patients undergoing femoral thromboembolectomy for blunting the sympathetic-mediated response to the surgical trauma and provide better perioperative analgesia and reduced perioperative opioid requirements and opioid-related adverse effects. However, in a definite patient population with certain comorbidities or coagulopathy; neuraxial anesthesia is contraindicated; hence, other peripheral nerve blocks will be the alternate choice.[1]

The fascia iliaca block (FIB) is disturbed mainly to the anterior region of the thigh by blocking the femoral and the lateral femoral cutaneous nerve. Moreover, FIB may possibly extend to the obturator, ilioinguinal, genitofemoral, lateral cutaneous nerve of the thigh, and over the psoas muscle but rarely reaches the lumbar plexus.[2],[3]

The FIB is considered as an easy technique used effectively and safely for perioperative analgesia whether for tolerating the painful positioning with spinal anesthesia (SA)[4] or for postoperative analgesia in orthopedics surgeries. It was applied either as a single injection[5] or continuous administration.[6]

The FIB is a compartment block principally selected in preference to femoral nerve block owing to wider distance and so less incidence to accidentally puncture the femoral nerve or femoral vessels with subsequent neuropathy or hematoma development which is valuable for patient with abnormal coagulation or extremity compromised blood flow.[7]

Up to best of our knowledge, only Ruzbarsky et al.[8] and Parate et al.[9] had used FIB on a limited number of cases as a primary anesthetic alternate to neuraxial anesthesia and general anesthesia (GA) for lower limb surgeries; although, it was accompanied with light-to-moderate sedation. Therefore, FIB needs more assessment as a sole anesthetic technique.

Thus, this study was conducted to evaluate the success of FIB as a sole anesthetic technique compared to SA in thromboembolectomy as a primary outcome. While, hemodynamic variation, postoperative pain score and analgesic requirements in the first postoperative day were the secondary outcomes.

 Patients and Methods



This prospective randomized study started from November 15, 2017 to April 15, 2019 after receiving the ethical approval from the Institutional Review Board of Mansoura faculty of medicine approval (R/17.07.111). Written informed consent from every participating patient was signed. The enrolled patients aged between 40 and 70 years of either gender, American Society of Anesthesiologists physical status Classes I and II admitted to undergo unilateral surgical transfemoral thrombectomy for acute unilateral lower limb ischemia. The study was registered in Clinical trials.gov. with special identifier NCT03798834.

Patients with body mass index ≥35 kg/m2, previous vascular surgery in the same lower limb, psychiatric, neuromuscular disorders or any contraindications to SA, known allergy to local anesthetics (LA) or infection at the injection site were excluded from the study.

Patients were randomly divided by means of coded envelopes into two groups. The first group received unilateral (SA group n = 56 patients) and the second group received (FIB group n = 56 patients).

Preoperatively, patients were assessed cautiously and instructed to use a 10-mm visual analog scale (VAS) for pain and their basal pain values were recorded which was treated ≥ 4 by paracetamol 1 g intravenous (i.v.)

Preloading was started and maintained with warmed Ringer's solution adjusted at rate of 6 ml/kg started 1–2 h before anesthetic block performance.

On arrival to the operating theater, oxygen mask was applied, and the patient was monitored for peripheral oxygen saturation, heart rate (HR), and mean arterial pressure (MAP) with recorded of basal values. In the first group, unilateral SA was performed under a complete aseptic technique in the lateral decubitus position with the affected limb downward at L3–L4 or L4–L5 spaces with 10 mg hyperbaric bupivacaine 0.5% injected over 30 s via a 25-gauge spinal needle after local skin infiltration with 2 mL of 2% lidocaine was done. The lateral decubitus position was maintained for almost 15 min then the patient was turned to the supine position.

For FIB group, the block was performed ultrasound-guided under complete aseptic technique utilizing a Korean Siemens ACUSON X300 high-frequency 13–16 MHz linear array. While the patient placed in the supine position; 1 cm below the point at the junction of the lateral third and medial two-thirds of a line from the pubic tubercle to the anterior superior iliac spine, the probe was be placed in a transverse orientation on the thigh, then the femoral artery was identified. The fascia lata and the fascia iliaca sonography appeared as two hyperechoic lines. After 2 mL of 2% lidocaine, local infiltration to skin was done, a 22-G needle was introduced perpendicular to the skin parallel with the transducer in a lateral-to-medial orientation to allow visualization of the full length of the needle throughout the procedure. The needle tip was visualized penetrating the fascia lata before penetrating the fascia iliaca. After negative blood aspiration, 30 mL of 0.25% bupivacaine was injected. An expanding anechoic collection just below the fascia iliaca visually confirmed correct placement of anesthetic.

In both groups, the sensory block was assessed using pinprick over the incisional site, which is the inguinal ligament from the pubic tubercle to the anterior superior iliac spine with 5 cm above and below it. It was evaluated 15 min after LA injection. A 3-point scale was used: 2 = normal sensation, 1 = loss of sensation to pin prick (analgesia) and 0 = loss of sensation to light touch (anesthesia).[10]

Once the sensory block grade equal zero, the surgery was allowable. Otherwise, the sensory block was further examined after another 15 min. If the sensory block score still not advanced to zero grade, the patient received GA induced by fentanyl 2 μg/kg, 1–2 mg/kg of propofol and 0.5 mg/kg atracurium then the laryngeal mask was inserted. The mechanical ventilator was adjusted to maintain the end-tidal carbon dioxide tension at 30–35 mm Hg. Anesthesia was maintained with 1.5% isoflurane in 60% O2 and incremental doses of atracurium when needed. At the end of the surgery, isoflurane was discontinued. Neuromuscular blockade was antagonized before extubation with 0.04 mg/kg neostigmine and 0.02 mg/kg atropine.

Furthermore, after documented sensory block zero, during the surgery; if any patient complained of intolerable pain related to the surgical site, 2 mcg/kg fentanyl was given. If the pain persisted, the patient received GA in the same previous steps.

Block failure was declared when the need to receive GA was due to perioperatively inadequate sensory blockade of the incisional site after 30 min of LA injection. Subsequently, patients were further classified according to the need to conversion to GA into succeeded and failed block.

Ringer's solution was infused as judged by losses and hemodynamic measurements. Intraoperative monitoring included; HR and MAP recorded immediate, 3, 10, 20, 30, 45, and 60 min after LA injection then at the end of the surgery, 1 and 3 h postoperatively. Hypotension (fall of MAP by 20% or more from basal value) was corrected by fluid supplementation and/or 5 mg of ephedrine incremental. Bradycardia (HR <50 bpm) was treated with incremental 0.5 mg atropine i.v.

The surgical duration was recorded from starting the surgery till dressing. Paracetamol 15 mg/kg was infused at the end of surgery and repeated every 6 h in the 1st postoperative day.

The postoperative pain was recorded using VAS immediately, 1, 4, 8, 12, and 24 h postoperatively. Whenever VAS ≥4; 0.04 mg/kg i.v. morphine was given. Analgesic duration (time from LA injection to the first analgesic request) and the total morphine consumption during the 1st postoperative day were recorded.

Postoperatively, any sensory deficit, motor weakness, postoperative headache, pruritus, nausea, or vomiting were reported and appropriately treated.

Sample size

According to a previous study, the success rate of SA was 96.8%.[11] If there is a true difference in favor of the standard treatment (SA) of 1%, then 112 patients are required to be 80% sure that the upper limit of a one-sided 95% confidence interval (or equivalently a 90% two-sided confidence interval) was exclude a difference in favor of the standard group of >10%.

Statistical analysis

Data entry and analyses were performed using Statistical Package version 17 (SPSS, Inc., Chicago, IL, USA). Data normal distribution was examined using the Shapiro–Wilk's test. Paired t-test was conducted to evaluate the impact of time on the mean of continuous variable in the two groups. Continuous, parametric data were reported as mean ± standard deviation by independent t-test between the two groups.

For the subdivided groups according to the succeeded and failed block; one-way analysis of variance with post hoc analysis was used for parametric data, whereas Kruskal–Wallis test was used for nonparametric data followed by Mann–Whitney U-test for intergroup significant difference. The statistical significance level was set at P < 0.05.

 Results



[Table 1] of the demographic and surgical features of the patients did not differ statistically among the two groups.{Table 1}

The incidence of the succeeded block was 100% in the SA group, while it was 80.35% in the FIB group [Figure 1]. Two patients in succeeded FIB group required intraoperative fentanyl analgesic and continued the surgery without conversion into GA.{Figure 1}

As regards the HR [Figure 2], there was statistically significant decrease to the basal values in SA group at 3, 10, and 20 min after LA injection (P = 0.014, 0.003, and 0.009, respectively). However, no patient showed bradycardia requiring therapeutic intervention.{Figure 2}

[Figure 3] shows the mean blood pressure where there was a statistically significant decrease in SA group at 3, 20, and 45 min after LA injection compared to the basal values (P = 0.000, 0.045, and 0.024, respectively).{Figure 3}

Fourteen patients (25%) in the SA group developed hypotension, whereas in the FIB group, seven patients (12.5%) had hypotension. All those patients had good respond to 5 mg ephedrine i.v. after volume expansion.

Values of VAS were decreased significantly in SA group in comparison to succeeded FIB group immediately and 1 h postoperatively (P = <0.001 and 0.002, respectively), while when compared with failed FIB group noticed 1 h postoperative (P value 0.011) [Figure 4].{Figure 4}

[Table 2] shows the postoperative analgesia during the 1st postoperative day. The analgesic duration (hours) was 11.9 ± 7.9, 8.2 ± 7.3, and 10.7 ± 9.7 in the SA group, succeeded FIB and failed FIB groups, respectively (P = 0.073). Morphine consumption in the 1st postoperative day was not significant between SA group (4.1 ± 3 mg), succeeded FIB (5.2 ± 2.7 mg), and failed FIB group (5 ± 5 mg) (P = 0.181). Two patients in succeeded FIB group required intraoperative fentanyl analgesic and continued the surgery without conversion into GA.{Table 2}

Two patients in the SA group reported nausea required no therapeutic intervention. No patient in either group had any symptoms or signs of LA toxicity or postoperative headache.

 Discussion



This study conducted on 112 patients demonstrated 80.35% success incidence of preoperative FIB as a sole anesthetic technique compared to the SA (100%) without requiring conversion to GA for thromboembolectomy of unilateral acute lower limb ischemia.

In contrast to the present study, the success rate of FIB as the primary anesthetic technique was 100% without conversion to GA in Ruzbarsky et al.'s study. This difference could be attributed to the small patient's number which was six and using variant sedation included midazolam 1–2 mg, fentanyl up to 50 μg, and propofol infusions from 0 to 30 μg/kg/min started from patients' positioning.[8]

Another successful application of FIB as the sole anesthetic technique was used by Parate et al. in their case report for emergent transfemoral thrombectomy. Furthermore, they had used dexmedetomidine infusion 0.5 mcg/kg bolus over 10 min started immediately after FIB, followed by 0.5 μg/kg/h all over the surgical duration.[9]

Contradictory to the higher failure rate recorded in this study; Johnston et al. had reported lesser rate of failure, which was 7.2% necessitating conversion to GA. In their retrospective study, a more proximal approach rather than FIB was applied involved block of the femoral nerve in addition to the lateral femoral cutaneous nerve for hip fractures surgeries on 375 patients.[12]

The explanation is mainly due to the authors had considered failed block and so starting GA after repeating both nerves' blockade twice. As well the succeeded block was operated under mild sedation by propofol/alfentanil.

The supposed explanation of the mechanism in the FIB group is the cutaneous innervation of the lumbar plexus nerves differs largely between individuals, such as for obturator nerve which may be missing.[13]

Acute lower limb ischemia (critical limb ischemia [CLI]) is a critical condition that affects patients with peripheral artery disease.[14] Many studies[14],[15],[16],[17] had considered CLI when the patient had constant ischemic pain necessitating analgesia for >14 days duration and/or recognized tissue loss as a result of ischemia.

Severe peripheral ischemia was defined as ischemia could threat the viability of the limb necessitating thrombolytic treatment, angioplasty, bypass surgery, or even amputation.[18]

Since the majority of peripheral arterial occlusive disease occurs in elderly who usually had various comorbidity as; obesity, elevated serum triglyceride level, angina pectoris, diabetes mellitus, and smoking.[19] Besides those patients usually receiving antiplatelet (either reversible as warfarin or irreversible as clopidogrel antiplatelet agent) and/or an anticoagulant therapy to augment the benefit aimed to avoid bypass graft thrombosis.[18],[20] Moreover, antiplatelet treatment decreases the occurrence of major cardiovascular complications in patients with peripheral arterial disease.[18],[21] In spite of the beneficial benefits of these drugs, this may hinder those patients from getting neuraxial anesthesia as SA mainly demanding an international normalized ratio <1.5 to perform it.[22]

Neuraxial anesthesia is more preferable when compared to GA as a reduction in intra-operative blood loss, blood transfusion, reduced deep-venous thrombosis with subsequent pulmonary embolism,[23] and minor postoperative delirium.[24],[25] Despite those various advantages of SA, it causes vasodilatation through the sympathetic blockade.[26],[27],[28]

Post-spinal rapid hemodynamic instability is more deleterious in most patients with CLI who had preexisting reduced physiological reserve and compromising vital organs perfusion from aging and associated multiple morbidities.[29]

The 20% incidence of hypotension in the SA group was similar to other literature ranging from 15%[30] to 33%.[31] Especially the SA was performed unilaterally at low-level Sp A, using small-dose hyperbaric bupivacaine with slow injection over 30 s approach, those altogether documented to permit low neuroaxial block level) thus stable hemodynamic parameters.[32]

The early significant bradycardia in the SA group is explained by the neuraxial blockade level exceeds T4, blocking cardioacceleratory fibers with subsequent reduction in both venous return and systemic vascular resistance resulting in decrease in cardiac output and HR.[31]

The minimal hemodynamic variations among FIB group which recorded in the current study were similar to the finding or Parate et al., in their case report although the patient aged 70 years with recent myocardial infarction and dexmedetomidine was infused all over the surgical duration.[9] This is because of FIB rarely reaches the lumbar plexus and devoid of central sympathetic blockade.[2],[3]

The limitation of this study is the inability to ensure the blindness of the technique. Because this study compare between two different techniques.

 Conclusion



Preoperative FIB could be considered as a promising alternative anesthetic technique to SA with better hemodynamic parameters in patients undergoing transfemoral thrombectomy for acute lower limb ischemia. It could be also due to limited precautions considered the first choice over SA for patients on perioperative anticoagulants.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Horlocker TT, Vandermeuelen E, Kopp SL, Gogarten W, Leffert LR, Benzon HT, et al. Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional anesthesia and pain medicine evidence-based guidelines (Fourth edition). Reg Anesth Pain Med 2018;43:263-309.
2Capdevila X, Biboulet P, Bouregba M, Barthelet Y, Rubenovitch J, d'Athis F. Comparison of the three-in-one and fascia iliaca compartment blocks in adults: Clinical and radiographic analysis. Anesth Analg 1998;86:1039-44.
3Hanna MH, Peat SJ, D'Costa F. Lumbar plexus block: An anatomical study. Anaesthesia 1993;48:675-8.
4Yun MJ, Kim YH, Han MK, Kim JH, Hwang JW, Do SH. Analgesia before a spinal block for femoral neck fracture: Fascia iliaca compartment block. Acta Anaesthesiol Scand 2009;53:1282-7.
5Mouzopoulos G, Vasiliadis G, Lasanianos N, Nikolaras G, Morakis E, Kaminaris M. Fascia iliaca block prophylaxis for hip fracture patients at risk for delirium: A randomized placebo-controlled study. J Orthop Traumatol 2009;10:127-33.
6Morau D, Lopez S, Biboulet P, Bernard N, Amar J, Capdevila X. Comparison of continuous 3-in-1 and fascia iliaca compartment blocks for postoperative analgesia: Feasibility, catheter migration, distribution of sensory block, and analgesic efficacy. Reg Anesth Pain Med 2003;28:309-14.
7Kumar NS, NK, MR, Sebastian D, Gowda Rm P. Dexamethasone as an additive to bupivacaine in fascia lliaca compartment block: A prospective, randomized and double blind study. J Clin Diagn Res 2014;8:GC05-8.
8Ruzbarsky JJ, Gausden EB, Goldwyn EM, Lowenwirt IP, Kotlyar V. The fascia iliaca block as the primary intraoperative anesthesia for hip fracture surgery: A preliminary study. HSS J 2018;14:77-82.
9Parate LH, Channappa NM, Pujari V, Iyer S. Fascia iliaca block as the sole anesthesia technique in a patient with recent myocardial infarction for emergency femoral thrombectomy. Saudi J Anaesth 2015;9:199-201.
10Parrington SJ, O'Donnell D, Chan VW, Brown-Shreves D, Subramanyam R, Qu M, et al. Dexamethasone added to mepivacaine prolongs the duration of analgesia after supraclavicular brachial plexus blockade. Reg Anesth Pain Med 2010;35:422-6.
11Fuzier R, Bataille B, Fuzier V, Richez AS, Maguès JP, Choquet O, et al. Spinal anesthesia failure after local anesthetic injection into cerebrospinal fluid: A multicenter prospective analysis of its incidence and related risk factors in 1214 patients. Reg Anesth Pain Med 2011;36:322-6.
12Johnston DF, Stafford M, McKinney M, Deyermond R, Dane K. Peripheral nerve blocks with sedation using propofol and alfentanil target-controlled infusion for hip fracture surgery: A review of 6 years in use. J Clin Anesth 2016;29:33-9.
13Bouaziz H, Vial F, Jochum D, Macalou D, Heck M, Meuret P, et al. An evaluation of the cutaneous distribution after obturator nerve block. Anesth Analg 2002;94:445-9, table of contents.
14Rooke TW, Hirsch AT, Misra S, Sidawy AN, Beckman JA, Findeiss LK, et al. 2011 ACCF/AHA focused update of the guideline for the management of patients with peripheral artery disease (updating the 2005 guideline): A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines: Developed in Collaboration with the Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society for Vascular Medicine, and Society for Vascular Surgery. J Vasc Surg 2011;54:e32-58.
15Rutherford RB, Baker JD, Ernst C, Johnston KW, Porter JM, Ahn S, et al. Recommended standards for reports dealing with lower extremity ischemia: Revised version. J Vasc Surg 1997;26:517-38.
16Dormandy JA, Rutherford RB. Management of peripheral arterial disease (PAD). TASC working group. TransAtlantic Inter-Society Consensus (TASC). J Vasc Surg 2000;31:S1-S296.
17Second European consensus document on chronic critical leg ischemia. Circulation 1991;84:IV1-26.
18Warfarin Antiplatelet Vascular Evaluation Trial Investigators, Anand S, Yusuf S, Xie C, Pogue J, Eikelboom J, et al. Oral anticoagulant and antiplatelet therapy and peripheral arterial disease. N Engl J Med 2007;357:217-27.
19Jensen SA, Vatten LJ, Myhre HO. The prevalence of chronic critical lower limb ischaemia in a population of 20,000 subjects 40-69 years of age. Eur J Vasc Endovasc Surg 2006;32:60-5.
20Collinge CA, Kelly KC, Little B, Weaver T, Schuster RD. The effects of clopidogrel (Plavix) and other oral anticoagulants on early hip fracture surgery. J Orthop Trauma 2012;26:568-73.
21Antithrombotic Trialists' Collaboration. Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. BMJ 2002;324:71-86.
22Gleason LJ, Friedman SM. Preoperative management of anticoagulation and antiplatelet agents. Clin Geriatr Med 2014;30:219-27.
23Mauermann WJ, Shilling AM, Zuo Z. A comparison of neuraxial block versus general anesthesia for elective total hip replacement: A meta-analysis. Anesth Analg 2006;103:1018-25.
24Luger TJ, Kammerlander C, Luger MF, Kammerlander-Knauer U, Gosch M. Mode of anesthesia, mortality and outcome in geriatric patients. Z Gerontol Geriatr 2014;47:110-24.
25Neuman MD, Silber JH, Elkassabany NM, Ludwig JM, Fleisher LA. Comparative effectiveness of regional versus general anesthesia for hip fracture surgery in adults. Anesthesiology 2012;117:72-92.
26Liu SS, McDonald SB. Current issues in spinal anesthesia. Anesthesiology 2001;94:888-906.
27Rooke GA, Freund PR, Jacobson AF. Hemodynamic response and change in organ blood volume during spinal anesthesia in elderly men with cardiac disease. Anesth Analg 1997;85:99-105.
28Butterworth J. Physiology of spinal anesthesia: What are the implications for management? Reg Anesth Pain Med 1998;23:370-3.
29Lim HH, Ho KM, Choi WY, Teoh GS, Chiu KY. The use of intravenous atropine after a saline infusion in the prevention of spinal anesthesia-induced hypotension in elderly patients. Anesth Analg 2000;91:1203-6.
30Tarkkila P, Isola J. A regression model for identifying patients at high risk of hypotension, bradycardia and nausea during spinal anesthesia. Acta Anaesthesiol Scand 1992;36:554-8.
31Carpenter RL, Caplan RA, Brown DL, Stephenson C, Wu R. Incidence and risk factors for side effects of spinal anesthesia. Anesthesiology 1992;76:906-16.
32Moosavi Tekye SM, Alipour M. Comparison of the effects and complications of unilateral spinal anesthesia versus standard spinal anesthesia in lower-limb orthopedic surgery. Braz J Anesthesiol 2014;64:173-6.