Safe conduct of major regional anaesthesia Document PS3

Performed by person who is trained or is being supervised Must know

o Anatomyo Physiologyo Pharmacologyo Potential complications and management

Selection of appropriate technique Trained assistant Informed consent Appropriate infection control measures IV access must be obtained prior to commencement of technique Appropriate monitoring Anaesthetist is responsible for patient once technique employed Documentation of technique

o Including instructions for subsequent management Post block

o Appropriately trained staffo Clear labelling of cathetero Dedicated infusion pumpso Written protocols and guidelines for continued managemento Regular monitoring

Pain score BP HR Temp RR Sedation score Saturations Sensory and motor function

o Recognition and treatment of side effectso Must have anaesthetic review daily if catheter in situo Catheter can be removed by trained staff membero Surgical or other team members must be aware of analgesia being used

Epidural analgesia in obstetricso Changes in normal physiological process of labour and deliveryo Once epidural in place patient must be under the care of medical practitioner with obstetric trainingo Patient must have given informed consento From commencement to completion – must be skilled staff and equipment available to monitor and care fro

both mother and fetus and to manage complications arising from epidural

Preoperative Assessment

Surgical factorso Type of surgery – is it appropriate to employ regional techniqueso Length of time required for surgery

Patient factorso Previous experienceo Body habituso Local sepsiso Anticoagulation

Full anticoagulation with warfarin or heparin is absolute contraindication for central neuraxial blockade and relative contraindication to peripheral nerve blocks

o Bleeding disorderso Pre-existing nerve injuries/damageo Previous muscle wasting

Sterile Technique

Single shot non neuraxial blocks

Asceptic percautions Hand hygiene Wear protective gloves Skin disinfection

o 70% alcoholo chlorhexidine

Neuraxial Block or regional anaesthesia catheter placementFull aseptic techniqueMaximal barrier precautions

Full body draping Wearing a hat, mask, gown and sterile gloves

Skin preparation Chlorhexidine If contraindication for chlorhex – 70% alcohol

If ultrasound used it shouldn’t compromise the aseptic technique – need to use sterile sheath

Skills

Confirm site of surgery and site of regional block Position the patient

o Comfortable for both patient and also ergonomic for anaesthetisto Make sure all equipment are available and remain sterile and are within reacho Ultrasound to be in an appropriate position

Anatomical landmarkso Need to have a good knowledge of anatomical landmarks surround the area to be blockedo Must know what could be beyond the area you want to infiltrate

Allows you to be prepared for possible complications Eg. Pneumothorax with interscalene block Vascular infiltration with femoral nerve block

Aseptic techniqueo Dependant on what type of block is being performed (discussed in detail above)

Selection of appropriate needleo Choice of needle depends on the block being performed, the size of the patient, and preference of the

clinician. o Needles are typically classified according to tip design, length, gauge, and the presence or absence of electrical

insulation or other specialized treatment of the needles

o Tip Design Tuohy and short bevel noncutting needles provide more resistance and thus enhance the feel of the

needle traversing different tissues. Long bevel cutting needles, by contrast, do not provide as much tactile information while traversing

different tissues. Pencil point needles may be associated with less tissue trauma than short bevel needles when bony

contact occurs during spinal anesthesia, resulting in a lower incidence of postdural puncture headache.

o Needle length Should be selected according to the type of block being performed A short needle may not reach its target. Long needles have a greater risk of causing injury due to increased difficulty in their handling and

possibility of being inserted too deeply.o Needle gauge

Needles of very small size (25 and 26 gauge) are most commonly used for superficial and field blocks. Larger gauge needles (20-22 gauge) may be used in deeper blocks to avoid bending of the shaft and to

maintain better control over the needle path. When placing a continuous catheter, the needle gauge must be large enough to allow passage of the

catheter. 17-19 gauge needles are most commonly used with an 18- gauge catheter for continuous catheters

o We use Whitacre Pencil Point Spinal Needles usually ?27G Drug Selection

o To give the correct drug for the correct patient in the correct dose by the correct route at the correct timeo Should have a detailed understanding of the pharmacology, both pharmacodynamics and pharmacokinetics, of

the drugs they prescribe or administer, together with an understanding of potential complications of drug administration and how these should be managed.

o Labels Legibility of labels on ampoules and syringes should be optimised Self-adhesive pre-printed labels for application to syringes should be colour coded by class of drug

and conform to national standards In the absence of pre-printed labels for syringes, hand-written ones should be prepared, or syringes

should be labelled directly using permanent marker penso Drawing up and checking

Read the label carefully before drawing up and injecting Name, dose and expiry date

Draw up one syringe and one ampule at a time If there is an interruption the drug must be discarded Drugs given intrathecally should always be checked with another person Contamination must be avoided

Inadvertent intravascular and intraneural administrationo Intraneural

local anesthetic within the fascicle can lead to widespread axonal degeneration and permanent neural damage in animals, whereas extrafascicular injection does not disrupt the normal nerve architecture.

Part of this can be explained mechanically because the perineurium, a tough multilayer epithelial sheath, is not easily distensible to compensate to an increase in intrafascicular pressure.

o Intravascular Regular aspirations Stop injecting Treat symptoms and toxicity

Monitoringo Routine monitoring during administration of nerve blocks:o Pulse oximetryo Noninvasive blood pressureo Electrocardiogramo Respiratory rateo Mental status

Management of hypotension associated with central neuraxial block

Severe hypotension may be the result of vasodilatation, bradycardia, and decreased contractility.

Volume loading the patient with 10-20 ml/kg of crystalloid fluid or appropriate amount of colloid immediately prior and during the administration of a spinal anesthetic may be helpful. The patient’s cardiac function and medical history should be taken into account prior to this measure. Left uterine displacement is essential for the parturient. Trendelenburg position may help increase blood pressure by autotransfusion. Care must be taken not to extend the neuraxial blockade even higher.

Hypotension should be treated with metaraminol, a direct acting alpha adrenergic agonist, which increases venous tone and causes arterial constriction.

Ephedrine has a direct beta adrenergic effect, increasing heart rate and contractility as well as some indirect vasoconstriction (α).

Pre loading with fluid Trendelenberg position if possible

o Care to not extend the blockade even higher Treat with metaraminol

o Direct and indirect acting sympathomimetic agent that has agonist effects at both alpha and beta adrenoreceptors

o Alpha agonist activity predominateso Peripheral vasoconstriction

Increases SVR Increases preload

Ephedrine can also be usedo Ephedrine acts both indirectly (by causing release of noradrenaline from sympathetic nerve terminals) and

directly by stimulation of alpha- and beta -adrenoreceptors.

Phenylephrine is a direct- acting sympathomimetic agent that has agonist effects at alpha- adrenoceptors. The dose that stimulates alpha1 receptors is far less than the dose needed to stimulate alpha2 receptors. Clinically, phenylephrine mimics the effects of noradrenaline, but is less potent and longer lasting

High Spinal Block

High neural blockade can occur with either epidural or spinal anesthesia. This complication may be due to the administration of excessive doses of local anesthetic, failure to reduce doses in patients susceptible to excessive spread (i.e. elderly, pregnant, obese, or short patients), increased sensitivity, and excessive spread. When dosing a spinal or epidural, it is important to monitor the patients’ vital signs and block level.

Incremental dosing of epidurals allows the anesthesia provider to determine if the block is progressing more rapidly than anticipated. With hyperbaric spinal techniques, changing the patients’ position may slow down excessive spread. Prevention is based on careful consideration in the dosing of the neuraxial block, anticipation of potential complications, and continual monitoring of the blocks progression.

Initial symptoms include the following: dyspnea numbness or weakness of the upper extremities (i.e. tingling in the fingers) nausea will usually precede hypotension (hypoperfusion of the brain is responsible for nausea) mild to moderate hypotension

Management is supportive and dependent on the degree and height of the block. Early recognition is important to stop block progression – reverse trendelenberg/head raised. Serious cardio-respiratory compromise can be avoided.

Contraindications for neuraxial blockadeAbsolute Contraindications:

Patient refusal Inability to guarantee sterility of medications/equipment Infection at the site of injection Coagulopathy (acquired, induced, genetic) Severe hypovolemia

o Hypovolemia should be corrected prior to spinal anesthesia. o A spinal anesthetic in a severely hypovolemic patient may lead to cardiac arrest.

Increased intra-cranial pressure (i.e. brain tumor or recent head injury) Severe aortic stenosis Severe mitral stenosis Ischemic hypertrophic sub aortic stenosis Severe uncorrected anemia Allergy to local anaesthetic

Relative Contraindications: Sepsis (may spread infection to subarachnoid/epidural space) Uncooperative patient (dementia, psychosis, emotional instability) Preexisting neurological deficits (hard to differentiate natural progression versus neurological trauma related to

neuraxial blockade) Demyelinating lesions (i.e. multiple sclerosis may be exacerbated by surgical stress, temperature changes, or natural

progression. However, it may be difficult to differentiate these potential causes from the use of spinal anesthesia.) Stenotic valvular heart lesions Severe spinal deformity

Adequacy of block

Afferent functionPinprick and cold are most commonly used, but mechanical stimuli such as touch, skin pinch, pressure and gas jets can be used. Loss of sensation to cold occurs before pinprick, and both of these before touch, each stage correlating with inhibition of C, Ad and Ab fibres respectively.

Temperature perception is lost before pinprick, is generally at a higher level, and is usually assessed by the application of ‘cold’ using alcohol skin prep, ice, ethyl chloride, or a cold gel bag.

Loss of vibration and proprioceptive sensation have also been used.

Efferent functionAs a block extends cephalad, there is progressive impairment of motor as well as sensory function.

The commonest method of assessment is the modified ‘Bromage scale’.

0 - No motor block

1 - Inability to raise extended leg; able to move knees and feet

2 - Inability to raise extended leg and move knee; able to move feet

3 - Complete block of motor limb

Split it into three groups of assessment1. Sensory level

a. Analgesia to pin prickb. Loss of temperature c. Anaesthesia to soft touch

2. Motor blockadea. Bromage scoringb. Dynamometry

3. Sympathetic blocka. Haemodynamic statusb. Temperature regulation

What to do if block isn’t working?

No block: The wrong solution has been injected Local deposited in the wrong place Ineffective block

Repeating the procedure or conversion to general anaesthesia are the only option.

If, after operation, the patient has significant pruritus, it is likely that only an opioid was injected.

Good block of inadequate cephalad spread: The level of injection was too low Anatomical abnormality has restricted spread, Some injectate has been misplaced.

If a hyperbaric solution was used, flex the patient’s hips and knees and tilt the table head down. This straightens out the lumbar curve, but maintains a cephalad ‘slope’ and allows any solution ‘trapped’ in the sacrum to

spread further. A variation with the same aim, but perhaps better suited to the obstetric situation, is to turn the patient to the full lateral

position with a head down tilt, reversing the side after 2–3 min.

If a plain (and usually slightly hypobaric) solution has been used, it may help to sit the patient up, but beware of peripheral pooling of blood.Good, but unilateral block:

This is most likely because of positioning, Longitudinal ligaments supporting the cord have blocked spread.

If the operation is to be on the anaesthetized limb, then the surgeon should know that the other leg has sensation, and the patient should be reassured and closely monitored.

Otherwise, turning the patient onto the unblocked side if a hyperbaric solution was used (or the reverse for plain solutions) may facilitate spread.

Patchy block (This term is used to describe a block that appears adequate in extent, but the sensory and motor effects are incomplete.):

Local anaesthetic was at least partially misplaced Dose given was inadequate.

If this becomes apparent before surgery starts, the options are to repeat the spinal injection or to use a greater degree of systemic supplementation than was planned, the latter being the only option after skin incision.

Infiltration of the wound and other tissues with local anaesthetic by the surgeon may also be useful in such situations.

Inadequate duration:

Inadequate dose of local anaesthetic Use of short acting local given by accident instead of bupivacaine

Often the only option is to convert to general anaesthesia.

Complications of regional anaesthesia

Systemic toxicity of the local anaestheticMost commonly caused by unintended intravascular injection. To minimise risk:

adhere to the recommended dosages aspirate repeatedly and inject fractionally (negative aspiration does not entirely exclude intravascular injection) observe spread of local anaesthetic on ultrasound inject slowly observe and maintain verbal contact with the patient.

Nerve damage (extremely rare)To minimise risk:

ensure needle tip is in view before advancing when using ultrasound avoid parasthesia when inserting the needle use a suitable nerve stimulator use atraumatic needles.

HaematomaTo minimise risk:

consider not performing blocks in patients with a clinically manifest coagulation disorder or receiving anticoagulation treatment

refer to guidelines for regional anaesthesia in patients receiving antithrombotic therapy

Infection (especially with continuous catheter technique)To minimise risk:

insert the needle using an aseptic technique avoid injection through infected areas regularly check the catheter insertion site (at least once a day) immediately remove the catheter if the patient reports tenderness at the point of catheter entry (most sensitive indicator

of infection)

General contraindications to regional anaesthesia Allergy to local anaesthetic Rejection of technique by patient Clinically manifest severe coagulation disorders Infection or haematoma at injection site Lack of experience with performing nerve block Relative contraindication: neurological defects (previous documentation necessary)

Complications of neuraxial anaesthesia

The end result of neuraxial blockade:

Decreased sympathetic tone with an unopposed parasympathetic tone. This imbalance will result in many of the expected alterations of normal homeostasis noted with the administration of

epidural and spinal anesthesia.

CVS

Nerve fibers that affect vasomotor tone of the arterial and venous vessels arise from T5-L1

The venous system contains about 75% of the total blood volume while the arterial system contains about 25%. Dilation of the venous system is predominantly responsible for decreases in blood pressure since the arterial system is able to maintain much of its vascular tone.

Total peripheral vascular resistance in the normal patient (normal cardiac output and normovolemic) will decrease 15-18%. In the elderly the systemic vascular resistance may decrease as much as 25% with a 10% decrease in cardiac output.

Heart rate may decrease during a high block due to blockade of the cardioaccelerator fibers (T1-T4). Heart rate may also decline as a result of a decrease in SVR, decreased right atrial filling, and decreases in the intrinsic chronotropic stretch receptor response.

Total body oxygen consumption decreases in response to the extent of spinal blockade, providing a margin of safety. Severe hypotension may be the result of vasodilatation, bradycardia, and decreased contractility. Aggravating factors such as a head up position or the weight of a gravid uterus on venous return in the parturient may cause further declines in blood pressure.

Dilatation of venous system (75% of blood volume) o Decrease BP

Decreased peripheral resistance Decrease venous return Decreased CO High block

o T1-T4 – decreased HR Decreased HR can be from decreased SVR, decreased right atrial filling and decreased chronotropic stretch receptor

response Decreased contractility

Respiratory

Neuraxial blockade plays a very minor role in altering pulmonary function. Even with high thoracic levels of blockade, tidal volume is unchanged. There is a slight decrease in vital capacity. This is the result of relaxation of the abdominal muscles during exhalation. The phrenic nerve is innervated by C3-C5 and is responsible for the diaphragm. The phrenic nerve is extremely hard to block, even with a high spinal. In fact, apnea associated with a high spinal is thought to be related to brainstem hypoperfusion and not blockade of the phrenic nerve. This is based on the fact that spontaneous respiration resumes after hemodynamic resuscitation has occurred.

Patients with chronic lung disease depend on intercostal and abdominal muscles to aid their inspiration and exhalation. Neuraxial blockade may reduce the function of these muscles, having a detrimental impact on the patient’s ability to breathe, as well as affect the ability to clear secretions and cough.

Thoracic and abdominal surgical procedures are associated with decreased phrenic nerve activity resulting in decreased diaphragmatic function and FRC (functional reserve capacity). This can lead to atelectasis and hypoxia due to ventilation/perfusion mismatching.

minor effect slight decrease in vital capacity

o due to relaxation of abdominal muscles during expiration Thoracic and abdominal surgical procedures

o Decreased phrenic nerve activityo Decreased diaphragm activityo Decreased FRCo Atelectasis, hypoxia due to V/Q mismatch

GIT

Since sympathetic outflow originates at T5-L1, neuraxial blockade results in a sympathectomy with a predomination of parasympathetic nervous system effects. The end result is a small, contracted gut with peristalsis. Hepatic blood flow decreases in relation to decreases in mean arterial pressure but does not differ significantly from other anesthetic techniques.

Small contracted gut with peristalsis Decreased hepatic blood flow due to decreased MAP

Renal

Autoregulation maintains adequate blood flow to the kidneys as long as perfusion pressure is maintained.

Neuraxial blockade effectively blocks sympathetic and parasympathetic control of the bladder at the lumbar and sacral levels. Urinary retention can occur due to the loss of autonomic bladder control. Detrusor function of the bladder is blocked by local anesthetics. Normal function does not return until sensory function returns to S3.

Autoregulation of renal blood flow maintained Block sympathetic and parasympathetic control of bladder Urinary retention Normal function returns when sensory function returns to S3

Metabolic and endocrine

Surgery produces a host of neuroendocrine responses related to inflammatory response and activation of somatic and visceral afferent nerve fibers. This response results in the release of adrenocorticotropic hormone, cortisol, epinephrine, norepinephrine, vasopressin, and activation of the renin-angiotension-aldosterone system. The release of these substances has the following clinical manifestations: hypertension, tachycardia, hyperglycemia, protein catabolism, depressed immune response, and alteration in renal function. As noted earlier, neuraxial blockade can effectively block this response.

Surgery leads to neurohormonal response related to inflammatory response Release of adrenocoricotropic hormone, cortisol, adrenaline, noradrenalin, vasopressin, activation of RAS Neuroaxial blockade can effectively block this response

Other

Bleeding Infection Haematoma Nerve injury – neuropraxia usually