Unfortunately, the attitude of many anesthesiologists continues to be swayed by anecdotal reports of the complications of regional blockade. This clouds their decision-making with regard to their choice of technique. A good example is the Woolley and Roe case in the United Kingdom (2) after which spinal anaesthesia fell into disfavour in that country for almost a generation. It is to be hoped that in the future evaluation of techniques and drugs will be more scientific, unbiased and evidence-based (1).
In obstetric practice, neurological symptoms are usually reported by a nurse or surgical colleague some hours or days after the procedure. This is unfortunate because successful resolution of some neurological complications requires urgent treatment (eg. spinal epidural haematoma and abscess; meningitis; compressive and ischaemic neuropraxias).
Almost invariably, obstetricians, midwives and patients assume that the block is the cause of the symptoms although this is rarely the case.
A: INITIAL ENQUIRIES.
1 . THE PATIENT:
A detailed neurological history should be obtained and any conditions pre-disposing to neuropathy should be viewed with suspicion. These conditions include:
backache,
obesity,
disc disease,
local or systemic infection,
coagulopathy,
diabetes mellitus,
neurofibromatosis,
malignancy,
previous trauma.
Pregnancy and labour (particularly prolonged active second stage, abnormal posture and instrumental delivery) can, by themselves, produce nerve trauma (5) and backache (Chapter 84).
A comprehensive drug history (particularly with regard to the use of salicylates, NSAIDs, anti-coagulants, B12, anti-thyroid medications, hypoglycaemic agents, steroids and anti-metabolites) should be taken (Chapter 34).
A complete physical and neurological examination should be carried out without delay and the details carefully recorded. Because the interpretation of many neurological signs is subjective, it may be necessary for a second clinician to re-examine the patient.
2. THE LABOUR AND MODE OF DELIVERY:
Factors which have been implicated in the aetiology of nerve damage include:
mode of delivery;
posture during labour;
use of retractors or diathermy;
injections of local anaesthetic or vasopressors by the obstetrician;
major blood loss and other causes of hypotension (which may cause spinal cord ischaemia) (6) (Chapter 6).
It may be necessary to ascertain details of patient positioning or equipment usage from staff who were present in the operating or delivery room.
3. THE ANAESTHESIA:
Critically review the anaesthetic technique with particular reference to:
type of block (Chapter 70),
degree of technical difficulty (Chapter 105),
possibility of inadvertent dural puncture (Chapter 31),
distribution and severity of paraesthesiae at the time of insertion of block,
occurrence of a 'bloody' tap,
type, baricity and concentration of anaesthetic (eg. chloroprocaine) (Chapter 106),
additives to the anaesthetic (eg. adrenaline, clonidine, preservatives),
other drug usage (eg. sodium nitroprusside, diazoxide),
equipment usage (eg. continuous micro-catheter spinal),
details asepsis/antisepsis precautions taken (7),
possibility of incorrect drug usage,
experience of the operator,
difficulty with removal of the catheter (Chapter 75),
integrity of the removed catheter or spinal needle tip (Chapter 42), and
site of injection (eg. epidural above L2 - L3).
Spinal cord injury has been caused by lumbar puncture performed above L2-3 (Figure 16.1). Check the needle or catheter insertion site for signs of infection or other inflammation. The possibility that unsterile equipment has been used should be considered and needles and catheters from the same batch should be checked (microbiologically if thought appropriate).
Retained segments of fractured catheters may cause nerve irritation and damage (Chapter 104).
If parasthesiae or bleeding were noticed during the procedure, their significance should be evaluated in the context of the injury being investigated. The distribution of a parasthesia is most important when evaluating a neurological injury later on.
Many blocks are induced and/or maintained with mixtures of drugs and adjuvants prepared in the delivery room or at the bedside. Strict protocols for checking, diluting and mixing of drugs and for rechecking of ampoules and packaging should be adhered to (8).
If a wrong drug has been injected, its potential for causing nerve damage should be evaluated. The cause of the mistake should be reviewed and recommendations made to prevent its recurrence.
If infection has occurred, it should be borne in mind that many mixtures are prepared using sterile solutions obtained from ampoules which may not be sterile on the outside. Enquire whether:
1. drug mixing has occurred (eg opioids and adrenaline),
2. local anaesthetic contains an anti-microbial adjuvant (Chapter 5),
3. multi-dose vials have been used, or
4. solutions were drawn up using a sterile bacterial/viral filter.
The use of these filters may also reduce the potential for neurological damage caused by foreign matter such as crystals, shards of glass or fragments of rubber.
Under some circumstances, neurotoxicty has been associated with the use of certain local anaesthetic agents. For example, hyperbaric, concentrated (5%) lignocaine solutions have been associated with sacral nerve root damage when administered by slow injection through microspinal catheters (9).
Ideally, all drug mixtures should be prepared under sterile conditions in a laminar flow facility but this is often not possible. It is appropriate to have a hospital pharmacist review all dilution and mixing procedures before they are adopted.
Some local anaesthetics, such as etidocaine and bupivacaine, may cause prolonged neural blockade. This cause of prolonged blockade should only be proposed after all other possible causes have been excluded.
B. SITE AND NATURE OF THE INJURY
The anatomical site of the injury should be determined as accurately as possible in case the location of the neurological lesion is incompatible with the site of block placement (eg. prolapsed thoracic disc in a patient who received a lumbar epidural) (10).
The nature of the lesion should be described in terms of:
1. type: upper or lower motor neuron,
2. loss of function or modality: complete or partial, and
3. laterality.
C. DIAGNOSIS CONFIRMATION
If nerve damage is suspected, the clinical findings should be confirmed and documented by an appropriately-qualified colleague (neurologist, neurosurgeon). Further investigations may be required in order to establish a firm diagnosis. These may include magnetic resonance imaging, computed tomography and nerve-conduction or electromyographic studies.
D. DOCUMENTATION AND FOLLOW-UP
All findings and investigations should be recorded and, ideally, reported to a central data-base or journal. The patient and her obstetrician should be informed of the diagnosis and of the investigation and management plan. It is prudent to contact the medical insurer if there is any hint that litigation may follow.
It is important to remain in contact with the patient during the period of investigation and treatment and to reassure them about anaesthesia in the future. A letter to the patient, and the patient's primary doctor or physician with full details of the complication, investigations, treatment and recommendations about future anaesthesia care should follow.
References:
1. Ong BY, Cohen MM, Esmail A, et al: Parasthesia and motor dysfunction after labor and delivery. Anesth Analg 1987 66:18-22.
2. Cope RW: The Woolley and Roe Case. Anaesthesia 1954 9:275-283.
4. Vines G: Is there a database in the house? New Scientist 1995 145;1961;14-15.
5. Redick LF: Maternal perinatal nerve palsies. Postgrad Obstet Gynecol 1992 12:1-6.
6. Bromage PR: Spinal thrombophlebitis after hypotensive anaesthesia. NZ Med J. 1974 80:519-520.
8. Crowhurst JA, Simmons SW: Safety of Epidural Infusion Systems. Anaesth Intens Care 1994 22:6:741-743.
9. Bensons JS: FDA Safety Alert: Cauda equina syndrome associated with small-bore catheters in continuous spinal anesthesia. Food and Drug Administration. Rockville, Md. May 29, 1992.