Regional blockade and pre-existing medical conditions

THE PATIENT WITH PRE-EXISTING NEUROLOGICAL DISEASE

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JB Sartain
Cairns Base Hospital, Cairns, Qld

Introduction

Anaesthetists are concerned not to harm their patients through complications of Regional Blockade (RB). These concerns are increased in patients with Neurological Disease (ND), who may be at increased risk of further neurological damage.(1)

The two main questions addressed in this presentation are:

• What are the Risks of RB in patients with ND?
• Is RB appropriate for an individual patient with ND?

1. Risk of Regional Blockade:In the absence of appropriate randomised controlled trials, evidence of further damage in patients with ND is derived from case series, anecdotes and experimental data. There are essentially two potential causes of harm:

a) Herniation (or ‘coning’) of neural tissue
Patients with space-occupying lesions (SOLs) of the brain or spinal canal are at risk of herniation after dural puncture, with an incidence of sudden deterioration varying from 2-14% in different series.(2) A recent CT scan or MRI is therefore essential if patients may have a SOL based on the history.

In contrast, if there is no brain shift, or spinal canal distortion impeding the flow of CSF, dural puncture may actually be therapeutic, for instance in benign intracranial hypertension and normal pressure hydrocephalus.(2)

b) Increased susceptibility of damaged neural tissue to further damage

Other potential hazards of RB include trauma or pressure to nerves (from needle, catheter or haematoma) and direct neu

Peripheral nerves with pre-existing lesions may be predisposed to developing a clinically important neuropathy with even minor subsequent damage (the ‘double-crush’ phenomenon). However, the clinical importance of this for RB is unproven.(3,4)

Local Anaesthetics (LAs) have the potential for direct toxicity to nerve tissue, as evidenced by laboratory studies and reports of cauda equina syndrome with intrathecal lignocaine.(5) Direct LA neurotoxicity is concentration, time and agent dependent; it appears that lignocaine is the most and mepivacaine the least toxic of common agents. The use of adjuvant vasoconstrictors may cause nerve damage by delaying the uptake of LAs (thus increasing LA exposure), and by a dose-dependent vasoconstriction of neural arterioles (at least in peripheral nerves).(6) Consequently, it seems prudent to avoid high concentrations of more toxic agents and the use of adjunctive vasoconstrictors in patients with pre-existing ND.

2. Is RB appropriate for my patient with ND?

Quantifying the risk of damage from RB is difficult, as up to 89% of postoperative nerve damage may result from other factors, including surgical trauma, tourniquets, obstetric complications, positioning and spontaneous deterioration of pre-existing neurological disease.4 There is also evidence from case series that for most patients with ND (excluding those with SOLs), there is minimal additional risk from RB.(7,8)

Therefore, although some isolated case reports are disconcerting, it is reasonable to consider the use of RB for patients with ND.

One suggested approach is:

1. What is best for this patient? Is RB feasible or desirable for this procedure? Are there contraindications? What are the problems of other methods of anaesthesia or analgesia with this patient’s ND (Table 1)? Does the patient have airway, cardiorespiratory or other diseases that make RB preferable?
2. What is best for me? Is RB defensible to my patient, my colleagues and the Law? Have I documented the patient’s neurology and the decision process?
3. What am I best at? What is likely to work best in my hands?(9)

Table 1 Selected neurological conditions with possible risks from regional blockade and general anaesthesia

Summary

With a few exceptions, patients with ND have minimal or no increased risk from RB. The decision whether or not to use RB should be individualised on a balance of risks.

Time of Presentation
Saturday 13 May 2006 - 1330-1500

References

1. Horlocker T. Complications of spinal and epidural anesthesia. Anesthesiol Clin North America. 2000; 18(2): 461-85.
2. Crevel H, Hijdra A, de Gans J. Lumbar puncture and the risk of herniation: when should we first perform CT? J Neurology 2002; 249: 129-137.
3. Hebl J, Horlocker T, Sorenson E and Schroeder D. Regional anesthesia does not increase the risk of postoperative neuropathy in patients undergoing ulnar nerve transposition. Anesth Analg 2001; 93:1606-11.
4. Horlocker T, Kufner R, Bishop A et al. The risk of persistent paresthesia is not increased with repeated axillary block. Anesth Analg 1999; 88: 382-7.
5. Auroy Y, Benhamou D, Bargues L et al. Major complications of regional anesthesia in France: the SOS regional anesthesia hotline. Anesthesiology 2002: 97: 1274-80.
6. Neal J. Effects of epinephrine in local anesthetics on the central and peripheral nervous systems: neurotoxicity and neural blood flow. Reg Anesth Pain Med 2003; 28(2): 124-34.
7. Confavreux C, Hutchinson M, Hours M et al. Rate of pregnancy-related relapse in multiple sclerosis. N Eng J Med 1998; 338: 278-85.
8. Crawford J, James F, Nolte H et al. Regional analgesia for patients with chronic neurological disease and similar conditions. Anaesthesia 1981; 36:821.
9. Young W. Regional versus general anesthesia and the “Baconian” scientific method. Int J Obstet Anesth 2005; 14: 277-278.