Complications of Local Anesthetic Techniques By Dr. Mahmoud Abdelkhalek

Complications of Local Techniques Spinal& epidural anesthesia: Hypotension Nerve Injury Infection and Hematoma Peripheral Nerve Blocks Local Anesthetic Systemic Toxicity

Hypotension Mechanism: Signs include: Arterial and venous dilatation caused by sympathetic pharmacological denervation reduce cardiac afterload and preload Systemic hypotension results, and may be severe enough to compromise organ perfusion Signs include: Tachycardia Low BP Confusion Nausea Dizziness

Hypotension Treatment: Fluid preloading may reduce the incidence of hypotension Left lateral position is helpful in pregnant patients Intravenous titration of a vasopressor agent (e.g. bolus doses of ephedrine 5 mg or metaraminol 1 mg) usually restores arterial pressure rapidly Directly acting arterial constrictors are more appropriate than indirectly acting sympathomimetics if tachycardia is present and in patients with severe ischemic heart disease

Nerve Injury Nerve injury may result from direct trauma caused by the needle, or through chemical toxicity Epidural and subarachnoid block should be undertaken in the conscious patient; to allow early identification of impingement upon a nerve or the spinal cord

Infection and Hematoma Spinal abscess: A devastating complication of central nervous blockade Presents as sudden, painless loss of motor function, usually several days after performance of the block Meticulous aseptic technique helps to reduce the incidence of this complication but some cases arise spontaneously, probably as a result of bacteremia caused by surgery and inoculation of a small and otherwise asymptomatic epidural hematoma Urgent magnetic MRI and referral to a neurosurgeon are indicated if spinal abscess is suspected

Infection and Hematoma Epidural hematoma: A common complication of epidural catheter placement The large majority of hematomata are asymptomatic and resolve spontaneously They may be apparent only upon spinal imaging Large hematomata may cause permanent nerve injury

Infection and Hematoma Epidural catheters should not be inserted in patients who are receiving warfarin or intravenous heparin, or who have abnormal coagulation for some other reason Caution should be exercised if a patient is receiving low- dose heparin for thromboprophylaxis At least 12 h should be allowed to elapse between administration of low-molecular-weight heparin prophylaxis and epidural block Often, imaging is delayed because numbness and weakness are attributed to the effects of the epidural block; low concentrations of local anesthetic (e.g. 0.1% or 0.125% bupivacaine) do not cause weakness and cause minimal numbness, and there should be a high level of suspicion about the possibility of epidural hematoma if these signs arise in the postoperative period

Infection and Hematoma If blood is obtained via the needle or catheter during insertion and the patient is expected to be fully heparinized (e.g. during cardiac or major vascular surgery), the procedure should be postponed for 24 h As with spinal abscesses, urgent imaging and referral to a neurosurgeon are indicated

Peripheral Nerve Injury Peripheral nerves may be injured directly, through peripheral nerve blockade or vascular catheter insertion or surgery, indirectly, by poor positioning during anesthesia, or through ischemia during severe hypoxemia or hypotension Peripheral nerve injury occurs during 0.1% of anesthetics. The position of the patient during general anesthesia is the commonest cause of injury The brachial plexus and superficial nerves of the limbs (ulnar, radial and common peroneal) are the most frequently affected nerves The usual mechanism of injury to superficial nerves is ischemia from compression of the vasa vasorum by surgical retractors, leg stirrups or contact with other equipment Ischemic injury is more likely to occur during periods of poor peripheral perfusion associated with hypotension or hypothermia Nerve injury may occur as part of a compartment syndrome after ischemia from poor positioning, particularly when the legs are placed in Lloyd-Davies supports and the patient is positioned head-down

Peripheral Nerve Injury Nerves may also be injured by traction (e.g. the brachial plexus during excessive shoulder abduction) Meticulous care is necessary when positioning the patient. Padding should be used beneath tourniquets and to protect pressure points Extreme joint positions should be avoided Close surveillance of tourniquet ischemia times is essential Although many injuries recover within several months, all patients with a peripheral nerve injury must be referred to a neurologist for assessment and continuing care Many ulnar nerve palsies occur in patients with an anatomical predisposition, and this may be deduced from a history of numbness after sleep or as a result of posture at work In these patients, the elbows should not be placed in flexion during surgery

Peripheral Nerve Blocks There is a risk of direct damage to nerves in association with any peripheral nerve block Paraesthesia or pain in the distribution of a nerve are signs of the proximity of a nerve and should prompt needle withdrawal Pain during injection of local anesthetic, failure to abolish the muscular twitch from a nerve stimulator or the requirement for increased injection force may indicate intraneural positioning of the needle and should prompt immediate cessation of injection and withdrawal of the needle

Systemic Toxicity Occurs by accidental intravascular injection, LA overdose, or unexpectedly rapid absorption Systemic toxicity manifests itself mainly at CNS and CVS CNS effects first appear to be excitatory due to initial block of inhibitory fibres; subsequently, block of excitatory fibres

Systemic Toxicity CNS effects (in approximate order of appearance): Numbness of tongue Tremors Perioral tingling Convulsions Disorientation Seizures Drowsiness Generalized CNS depression Tinnitus Coma Visual disturbances respiratory arrest Muscle twitching

Systemic Toxicity

Systemic Toxicity: Precautions Intravenous access should be secured and adequate resuscitation equipment and drugs should be immediately available before a local anesthetic block is undertaken The patient should be adequately monitored The lowest dose of the least toxic drug available should be used to achieve the effect required (Table )

Local Anesthetic Toxicity: Precautions

Systemic Toxicity: Precautions Local anesthetics should always be injected slowly with repeated aspiration for blood, and with constant verbal contact and observation of the patient Any change in the patient’s apparent mental state should prompt immediate cessation of injection Injection of a test dose of a local anesthetic which contains adrenaline usually results in sudden tachycardia if intravascular injection has occurred The addition of adrenaline reduces the speed of absorption from tissues, allowing larger maximum doses, reducing the potential for toxicity and prolonging the action of the local anesthetic

Treatment of LA systemic toxicity Use the A, B, C’s for the management of local anesthetic toxicity A= airway Maintain a patent airway, administer 100% oxygen B= breathing May need to be assisted with positive pressure ventilation or intubation C= circulation Check for a pulse If no pulse, initiate CPR

Treatment of LA systemic toxicity Convulsions are very common in significant toxicity and administration of an anticonvulsant (e.g. diazepam 10 mg, thiopental 50 mg) is often necessary

Treatment of LA systemic toxicity Hypotension: (Fluids+ Vasopressors) Rapid infusion of IV fluids Place the patient in a head down position (Trendelenburg) Phenylephrine shots or infusion Ephedrine (typically 5 mg shots) If refractory treat the patient with epinephrine (5-10 mcg shots) Repeat and escalate the dose as necessary

Systemic Toxicity: Treatment Arrhythmias may occur and should be treated appropriately Severe heart block may require an infusion of isoprenaline or pacing Chest compressions are required if there is no palpable pulse Survival from local anesthetic toxicity should approach 100%

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