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 Table of Contents  
CASE REPORT
Year : 2019  |  Volume : 33  |  Issue : 2  |  Page : 103-105

Role of ultrasound guided continuos sciatic nerve blocks in a complicated case of vasopressor induced lower limb ischemic pain


Department of Anaesthesiology and Pain Medicine, Yashoda Hospital, Secunderabad, Telangana, India

Date of Submission21-Dec-2018
Date of Decision10-Apr-2019
Date of Acceptance06-May-2019
Date of Web Publication7-Aug-2019

Correspondence Address:
Dr. Uma Pradeepa Lakkaraju
Plot No-166, Phase-2, Kapra, ECIL, Hyderabad - 500 062, Telangana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijpn.ijpn_68_18

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  Abstract 

Acute limb ischemia (ALI) is defined as any sudden decrease in limb perfusion causing a potential threat to limb viability. We are presenting a case of vasopressor-induced ALI involving both the lower limbs in a patient with altered coagulation, thrombocytopenia, and severe cardiovascular dysfunction. It is challenging to provide pain relief to a very sick hemodynamically unstable patient. A continuous peripheral nerve block of the lower limb has been shown to provide multiple benefits. In this patient, we successfully placed ultrasound-guided bilateral sciatic nerve catheters for continuous pain relief up to 2 weeks, with no major complications during or after the procedure. This case highlights that continuous peripheral nerve catheters provide good analgesia in ALI and have a positive effect on microcirculation, hence to be more frequently used.

Keywords: Digital ischemia, sciatic nerve catheters, vasopressor induced


How to cite this article:
Lakkaraju UP, Gurram RM. Role of ultrasound guided continuos sciatic nerve blocks in a complicated case of vasopressor induced lower limb ischemic pain. Indian J Pain 2019;33:103-5

How to cite this URL:
Lakkaraju UP, Gurram RM. Role of ultrasound guided continuos sciatic nerve blocks in a complicated case of vasopressor induced lower limb ischemic pain. Indian J Pain [serial online] 2019 [cited 2019 Oct 17];33:103-5. Available from: http://www.indianjpain.org/text.asp?2019/33/2/103/264084


  Introduction Top


This case report on acute limb ischemia (ALI)[1] brings to light an uncommon but devastating complication of vasopressor-induced peripheral ischemia which continues to exist and thus requires our attention. Ischemic pain is difficult to treat due to its poorly understood mechanism. In this case, it was particularly challenging in view of associated comorbidities and unstable condition of the patient. Controversy remains whether or not regional anesthetic techniques block ischemic pain. This case exemplifies the role of continuous sciatic nerve catheters in providing excellent analgesia for vasopressor-induced ischemic pain involving lower limbs.


  Case Report Top


A 45-year-old female, a known case of diabetes mellitus type 2, hypertension, coronary artery disease, and hypothyroidism, presented with a history of severe chest pain, breathlessness, and hypotension to the emergency department. A diagnosis of acute inferior wall myocardial infarction with cardiogenic shock was made after thorough cardiac testing. On general physical examination, there was no cyanosis of the limbs. She underwent right coronary artery stenting on the same day and was subsequently transferred to the intensive care unit where she was on continuous vasopressor support. She was started on intravenous (IV) fluids, antibiotics, and dopamine as well as noradrenaline (NA) at usual doses (NA 0.2 μg/kg/min), and this treatment was insufficient to stabilize the patient's condition. To maintain systolic arterial pressure of ≥90 mmHg and appropriate urine output, NA dosage was steadily increased until the highest dose of 4.16 μg/kg/min was reached 2 days after admission. On day 3 the patient developed pregangrenous changes involving both legs till the ankle [Figure 1]a. She complained of severe pain, pricking in nature involving all the digits of both the lower limbs. Pain was severe, Visual Analog Scale (VAS) >9/10 at rest, and did not respond to trial of drugs for 3 days which included nonsteroidal anti-inflammatory drugs (injection diclofenac IV 75 mg twice a day), pregabalin (75 mg twice a day), and opioids (IV fentanyl >5 μ/kg/h.). Pain management team was consulted for further management.
Figure 1: (a) Cyanosis and mottling initially in the right lower limb. (b) Postprocedure catheter in situ

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We planned for bilateral continuous sciatic nerve catheters, but this patient posed a medical challenge to our team as she was on dual antiplatelet therapy (post-PTCA status) and developed thrombocytopenia; thus, heparin was stopped, and she was put on injection bivalirudin (direct thrombin inhibitor). Her platelet count was 70,000 and her international normalized ratio was 2.18.

Procedure

The sciatic nerve was scanned at the popliteal fossa; a 55-mm insulated needle was inserted in-plane to ultrasonography probe and advanced slowly toward the sciatic nerve. Once the needle was in contact with the nerve, a bolus of 20 ml of 0.2% ropivacaine was injected and its distribution around the nerve was observed. Following this, a 20G catheter was introduced through the needle and subsequent analgesia was achieved with a continuous infusion of 0.2% ropivacaine at 5 ml/h [Figure 1]b. The procedure was performed under sterile conditions and standard monitoring.

Although there was bleeding from the site of needle puncture during the procedure and up to 3 h after, it was controlled on applying compression. At 2-week follow-up, she reported significant pain relief (VAS 2/10), and there were signs of improved peripheral circulation (on arterial Doppler).


  Discussion Top


The International Association for the Study of Pain Task Force on Taxonomy, updated in 2011, classified ischemic pain under the umbrella category of neuropathic pain.[2] The pathophysiology, neurological pathways, and central registration and processing of ischemic pain are complex and poorly understood. Ischemic pain typically has elements of both nociceptive and neuropathic pain and frequently its nociceptive pathways include the sympathetic nervous system.[3] Munk et al.[4] showed that surgical pain is primarily mediated through the thin unmyelinated C-fibers and myelinated Aδ-fibers, whereas ischemic pain primarily mediates through the thicker Aβ-fibers. Thus, using local anesthetics in higher concentrations, it may be possible to obtain sufficient pain relief. Cometa et al.[5] showed that in ischemic tissue, release of bradykinin, serotonin, acetylcholine, adenosine, potassium ions, and hydrogen ions is responsible for ischemic pain. Tissue acidosis evidently initiates the pain pathway as increasing levels of hydrogen ion concentration may act on skeletal muscle nociceptors resulting in pain impulse transmission.

Vasopressors such as dopamine and NA are frequently used in shock states because of their positive inotropic effects and their effect on contraction of the peripheral vasculature. However, this can lead to the development of peripheral ischemia and gangrene. When dopamine is used in higher doses of up to 20–50 μg/kg/min, vasoconstriction may occur due to alpha-receptor stimulation.[6] NA, an alpha-receptor stimulator in doses more than 1–2 μ/kg/h, is also thought to have vasospastic effects more intense in the digital vascular beds. As a result, peripheral ischemia and thus ischemic pain are not unexpected following high doses of dopamine or NA, and one such case was first reported in 1973 by Holzer et al.[7]

The patient in our report had risk factors for peripheral vascular disease and diabetes mellitus, and treatment with high doses of vasopressors was prolonged. Therefore, the development of gangrenous changes in both the lower limbs in this patient could be multifactorial but mainly precipitated by vasopressor use. When managing ischemic pain, especially in a critically ill and hemodynamically unstable patient, choosing a reliable technique that results in minimal hemodynamic effects is crucial. Although there are many studies[8] on various aspects of the postoperative pain control in patients with peripheral vascular disease with limb ischemia, there are no studies on administration of continuous peripheral nerve blocks (CPNBs) to control pain in the patient's vasopressor-induced ALI.

In view of the benefits of regional blockade such as increasing the blood flow to the affected tissue (at least by reducing pain-induced vasoconstriction), it may be advantageous to promote its use in vasopressor-induced ischemic pain. We speculate that continuous sciatic nerve block produced considerable pain relief in this patient by attenuating the conduction of noxious stimuli through primary afferent nerve fibers.


  Conclusion Top


Even though recent case reports and literature reviews suggest a lack of support for the use of regional anesthetics in ischemic pain, this case marks the usefulness of CPNBs, especially for vasopressor-induced lower-limb ischemic pain.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Creager MA, Kaufman JA, Conte MS. Clinical practice. Acute limb ischemia. N Engl J Med 2012;366:2198-206.  Back to cited text no. 1
    
2.
IASP Taxonomy Working Group. IASP Taxonomy: Pain Terms. IASP Taxonomy Working Group; 2011. Available from: http://www.iasp-pain.org/Content/NavigationMenu/GeneralResourceLinks/PainDefinitions/default.htm. [Last accessed on 2012 Oct 15].  Back to cited text no. 2
    
3.
Sanni A, Hamid A, Dunning J. Is sympathectomy of benefit in critical leg ischaemia not amenable to revascularisation? Interact Cardiovasc Thorac Surg 2005;4:478-83.  Back to cited text no. 3
    
4.
Munk-Andersen H, Laustrup TK. Compartment syndrome diagnosed in due time by breakthrough pain despite continuous peripheral nerve block. Acta Anaesthesiol Scand 2013;57:1328-30.  Back to cited text no. 4
    
5.
Cometa MA, Esch AT, Boezaart AP. Did continuous femoral and sciatic nerve block obscure the diagnosis or delay the treatment of acute lower leg compartment syndrome? A case report. Pain Med 2011;12:823-8.  Back to cited text no. 5
    
6.
Kaul S, Sarela AI, Supe AN, Karnard DR. Gangrene complicating dopamine therapy. J R Soc Med 1997;90:80.  Back to cited text no. 6
    
7.
Holzer J, Karliner JS, O'Rourke RA, Pitt W, Ross J Jr. Effectiveness of dopamine in patients with cardiogenic shock. Am J Cardiol 1973;32:79-84.  Back to cited text no. 7
    
8.
Seretny M, Colvin LA. Pain management in patients with vascular disease. Br J Anaesth 2016;117 Suppl 2:ii95-106.  Back to cited text no. 8
    


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