Reflection on Failed Spinal Anaesthesia:Clinical – Essay Example

Spinal anaesthesia is a very reliable surgical method because it is a very uncomplicated and straight forward technique (Wenk, et.al., 2012). The target area to be covered anatomically can easily be predicted, especially if the anaesthesia is appropriately introduced. However, failure may still be possible. An effective block would be sufficient in cases where the quality is up to standard, or when the duration is sufficient or when it is adequately intense (Abdallah, et.al., 2013).
The patient in this reflective essay shall be referred to as Robert to protect his identity in compliance with the provisions of the 2015 Nursing and Midwifery Council (NMC). He is 48 years old, generally healthy and has had no adverse medical incidents in the past. He was admitted however for revision of left knee replacement. Overall, he is healthy and had previous experiences with local and general anaesthetics. His BMI is in the normal range (28) and weighs 180 lbs. and height of 5’9”. According to the grading provided by the standards of the American Society of Anesthesiologists, he is of grade 1 status which basically translates to a rating of a normal and healthy patient (Daabiss, 2011). An anaesthetist examined him and he was later admitted into the elective unit. Reflection on Failed Spinal Anaesthesia:Clinical – Essay Example.
For his surgery, an operating room/theatre was prepared and prior to his entry into the room/theatre, the usual pre-operative checks were conducted. I checked the anaesthetic machine for possible defects of leaks, based on the 2004 standards indicated by the Association of Anaesthetists of Great Britain and Ireland (AAGBI), including the local trust guidelines and standards. Equipment for monitoring was also assessed based on the 2007 standards indicated by the AAGBI. The ABCD guidelines were also evaluated (Davies and Yesudian, 2013). This refers to

Two conditions are, therefore, absolutely necessary to produce spinal anesthesia: puncture of the dura mater and subarachnoid injection of an anesthetic agent.

Gaston Labat, 1922

Spinal (intrathecal) anaesthesia is generally regarded as one of the most reliable of regional block methods: the needle insertion technique is relatively straightforward, with cerebrospinal fluid (CSF) providing both a clear indication of successful needle placement and a medium through which local anaesthetic solution usually spreads readily. However, the possibility of failure has long been recognized, the above quote being taken from the work of Gaston Labat,²⁴ the ‘father’ of modern regional anaesthesia. His two conditions for success, although perhaps a little simplistic when related to current knowledge, still indicate the essence of the method and provide a starting point for the consideration of failure, although it may be helpful to define exactly what this means first. Literally, the word failure implies that a spinal anaesthetic was attempted, but that no block resulted; this happens, but perhaps a commoner outcome is that a block results, but is inadequate for the proposed surgery. Such inadequacy may relate to three components of the block: the extent, quality, or duration of local anaesthetic action, often with more than one of these being inadequate. This review has considered all three eventualities within the definition of ‘failure’.

Most experienced practitioners would consider the incidence of failure with spinal anaesthesia to be extremely low, perhaps less than 1%. However, a figure as high as 17% has been quoted from an American teaching hospital, yet most of the failures were judged to be ‘avoidable’.²⁸ A survey at another such institution considered that this high rate was ‘unacceptable’, and recorded the much lower, but still significant, figure of 4%, with ‘errors of judgement’ as the major factor.³² The clear implication is that careful attention to detail is vital, and it has been shown that a failure rate of <1% is attainable in everyday practice.¹⁷ Minimizing the incidence of failure is obviously a pre-requisite for gaining the benefits of spinal anaesthesia, and prevention must start with full recognition of the potential pitfalls so that clinical practice can be tailored to their avoidance. Reflection on Failed Spinal Anaesthesia:Clinical – Essay Example.

In general terms, block failure is usually ascribed to one of three aspects: clinical technique, inexperience (of the unsupervised trainee especially), and failure to appreciate the need for a meticulous approach.¹⁰ However, such broad categories reveal little about the many detailed ways in which an intrathecal injection can go astray within each of the five phases of an individual spinal anaesthetic, these being, in sequence, lumbar puncture, solution injection, spreading of drug through CSF, drug action on the spinal nerve roots and cord, and subsequent patient management. All of the problems involved are well described in the literature, but usually long ago, and many practitioners seem unaware of the issues involved. For instance, the neuroscience division of AstraZeneca received 562 ‘Product Defect Notification’ reports in the 6 yr to December 31, 2007, all ascribing failed spinal anaesthetics to ineffective bupivacaine solution (Fig. 1). Nearly one-third of reports (179) were from the UK, but virtually every country where the drug is marketed was represented. However, analysis showed that the returned material was within the product’s specification in every case so a formal review, based on a literature search, was thought to be worthwhile.

Fig 1

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Annual numbers of reports of failed spinal anaesthesia with bupivacaine received by AstraZeneca between January 1, 1993 and December 31, 2008 plotted according to region of the world.

Search strategy

For this review ‘PubMed’ and ‘Google’ databases were searched using the terms ‘failed regional anaesthesia’, ‘failed regional anesthesia’, ‘failed spinal anaesthesia’, and ‘failed spinal anesthesia’. Relevant articles were retrieved as were any possibly relevant papers in their reference lists. Supporting searches were performed on subjects that may not have been otherwise identified, specific examples being CSF volume, dural ectasia, and the chemical compatibility of local anaesthetics with adjuncts.

In addition, searches were made using ‘Planet’ (an AstraZeneca internal database), ‘Biosis’, ‘Current Contents’, ‘Embase’, ‘PsycINFO’, ‘Medline’, and ‘Medline Daily update’, using the terms ‘Failed Spinal Anaesthesia’ and ‘Failed Spinal Anesthesia’ as sole search terms and ‘spinal anesthesia’ or ‘spinal anaesthesia’ or ‘spinal anesthetic’ or ‘spinal cord anesthesia’ or ‘spinal cord anaesthesia’ or ‘anesthesia, spinal’ or ‘anaesthesia, spinal’ and ‘treatment failure’ or ‘therapy failure’, and ‘Intrathecal’. All papers identified as relevant are included in this review. Reflection on Failed Spinal Anaesthesia:Clinical – Essay Example.

Mechanisms and their prevention

Failed lumbar puncture

Inability to obtain CSF, sometimes referred to as a ‘dry tap’, is the only cause of failure which is immediately obvious. A needle with a lumen blocked at the outset is a theoretical possibility, but is most unlikely with modern equipment. However, both needle and stylet must be checked for correctness of fit before use, and the needle should not be advanced without the stylet in place because tissue or blood clot can easily obstruct the fine bore needles used now. Otherwise, a failed lumbar puncture is virtually always because of either poor positioning of the patient or incorrect needle insertion, both factors being within the control of the anaesthetist. Abnormalities of the spine (kyphosis, scoliosis, calcification of ligaments, consequences of osteoporosis), obesity, and patient anxiety make both positioning the patient and needle insertion more difficult, especially in the elderly. Texts of regional anaesthesia give more extensive instruction than can be provided here, and good clinical training is the key to success, but most difficulties are attributable to lack of adherence to the basic rules.

Positioning

The patient is placed on a firm surface; the lumbar laminae and spines are ‘separated’ maximally by flexing the whole spine (including the neck), the hips, and knees; rotation and lateral curvature of the spine are avoided; these points apply to lumbar puncture in both sitting and lateral horizontal positions; the former is usually an easier option in ‘difficult’ patients, but sometimes the reverse is true. The role of the assistant in achieving and maintaining the patient in the correct position cannot be underestimated.³⁵

Needle insertion

Although its accurate identification can be difficult using clinical land-marks, what is judged to be the third lumbar inter-space is used usually, but examination may indicate that another is preferable. Reflection on Failed Spinal Anaesthesia:Clinical – Essay Example. However, care should be taken not to venture too cephalad and risk damage to the spinal cord.³³ With the midline approach, insertion should start precisely in the mid-line, mid-way between the posterior spines, with the needle shaft at right angles to the back in both planes. Small, incremental changes in needle angle should be made only if there is resistance to advancement; if resistance is met, cephalad angulation should be tried first, and such angulation may be appropriate from the start if the patient is unable to flex fully (e.g. the obstetric patient at term). A degree of caudad angulation is sometimes needed, with a slight lateral direction being required very rarely. All authorities recommend that the anaesthetist should have a good knowledge of spinal anatomy and relate these to changes in tissue resistance as the needle is advanced so that a mental ‘picture’ of where the needle tip lies is appreciated.

The above points apply specifically to the midline approach; lateral or paramedian approaches are preferred by some,²⁷ especially if the mid-line ligaments are heavily calcified, but they are inherently more complex techniques. However, in the face of difficulty, the same basic rules apply: make sure that the patient is in the correct position and that the correct angles and insertion technique are used.

Adjuncts

A calm, relaxed patient is more likely to assume and maintain the correct position, so explanation (before and during the procedure) and gentle, unhurried patient handling are vital; light anxiolytic premedication contributes much to relaxing the patient; local anaesthetic infiltration at the puncture site must be effective without obscuring the landmarks, but must include both intradermal and s.c. injection. Achieving the correct position is a particular challenge in the patient in pain (e.g. from a fractured hip) and systemic analgesia (i.v. or inhalation) helps considerably. The aim of such adjuncts is to optimize the patient’s position and to prevent any movement. As will be discussed later, it takes only slight movement to displace the needle from its target.

Advances in ultrasound technology are reaching the stage where it can be used to overcome difficulties with lumbar puncture, but clinicians will still need to be aware of the problems and how they should be overcome.

Pseudo-successful lumbar puncture

The appearance of clear fluid at the needle hub is usually the final confirmation that the subarachnoid space has been entered. Rarely, however, the clear fluid is not CSF, but local anaesthetic injected as a ‘top-up’ for an epidural which then proved inadequate for a Caesarean section, or even spreading there from the lumbar plexus.²⁶ Unfortunately, a positive test for glucose in the fluid does not confirm that this fluid is definitely CSF because extracellular fluid constituents diffuse rapidly into fluids injected into the epidural space.Reflection on Failed Spinal Anaesthesia:Clinical – Essay Example.  Another, even rarer, suggested cause of clear fluid appearing at the needle hub, but not confirming successful lumbar puncture, is a congenital arachnoid cyst.³⁹

Solution injection errors

The appearance of CSF in the needle hub is an essential pre-requisite for spinal anaesthesia, but it does not guarantee success, which also requires that a fully effective dose is both chosen and actually deposited in the CSF.

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Dose selection

Studies of many factors influencing intrathecal drug spread have shown that the dose injected, within the range normally used, has only a small effect on the extent of a spinal anaesthetic, but is far more important in determining the quality and duration of block.²⁰ Overall, the actual dose chosen will depend on the specific local anaesthetic used, the baricity of that solution, the patient’s subsequent posture, the type of block intended, and the anticipated duration of surgery. Thus, knowledge of the factors influencing intrathecal drug spread and clinical experience with any particular local anaesthetic preparation are important guides to choosing an effective dose.

However, the need to guarantee an adequate effect means that the doses of drugs injected in standard ‘single shot’ techniques are larger than is strictly necessary, experience with dose titration during continuous spinal anaesthesia showing clearly that lower doses are often effective.²¹ In attempts to either minimize hypotension, for example by attempting to produce a unilateral block, or speed postoperative mobilization, by decreasing duration, some practitioners use lower doses than is traditional³ (e.g. 5–10 rather than 15 mg of hyperbaric bupivacaine). Used correctly, and in appropriate situations, such doses can be reliable, but they do mean that the margin for error is reduced and that the consequences of other problems (e.g. Loss of injectate—see below) will be exaggerated and so risk an inadequate block. It becomes even more important to ensure that the whole of that lower dose reaches the CSF and then spreads properly, remembering that the ‘dead space’ of the needle will contain a significant proportion of what is a small volume to start with.

Loss of injectate

The Luer connection between syringe and needle provides a ready opportunity for leakage of solution. A particular variant of this problem being a leak through a defect at the junction of needle hub and shaft.⁶ Given the small volumes involved, the loss of even a few drops may cause a significant decrease in the mass of drug reaching the CSF, and thus in its effectiveness. To avoid this, it has long been conventional teaching that the syringe containing the injectate must be inserted very firmly into the hub of the needle, and that a subsequent check is made that no leakage occurs.

Misplaced injection

Needle and syringe must be connected firmly, but great care should be taken to avoid either anterior or posterior displacement of the needle tip from subarachnoid to epidural space, where deposition of a spinal dose of local anaesthetic will have little or no effect. Fluid aspiration, after attachment of the syringe, should confirm free flow of CSF and, thus, that the needle tip is still in the correct space, but such aspiration may displace the tip unless performed carefully, as may the force of the injection of the syringe contents.Reflection on Failed Spinal Anaesthesia:Clinical – Essay Example.  To prevent displacement at any stage, it has been advocated that the dorsum of one hand should be anchored firmly against the patient’s back and the fingers used to immobilize the needle, while the other hand is used to manipulate the syringe.⁴⁰ Most practitioners would recommend aspiration for CSF after the injection to confirm that correct placement is maintained, and some advocate that this is done half way through as well although neither of these practices has been shown to influence the outcome of the block.^32,40

Tip displacement must be guarded against with any type of spinal needle, but it is a particular issue with the ‘pencil point’ needles now used widely to minimize the incidence of post-dural puncture headache. The opening at the end of these needles is proximal to the tip, so only a minor degree of ‘backward’ movement during syringe attachment may result in epidural injection as was recognized at an early stage in the widespread use of such needles.¹² The distances involved are of the order of a millimetre or two, but (as with leakage) misplacement of only a small amount of solution can have significant effects. An additional issue with pencil-point needles is that the opening, being much longer than the bevel of a Quincke needle, may ‘straddle’ the dura so that some solution reaches the CSF, and some the epidural space (Fig. 2).⁴¹ This may be exaggerated by the dura acting as a ‘flap’ valve across the needle opening. Initially, CSF pressure pushes the dura outwards so that aspiration is successful (Fig. 3A), but subsequent injection pushes the dura forward and the solution is misplaced . Reflection on Failed Spinal Anaesthesia:Clinical – Essay Example.