Book Text

Systemic Complications

Systemic toxicity results from inadvertent intravascular injection of local anesthetic, which often results from the poor application of the previously described basic safety rules. In awake patients, the first symptoms are neurologic, expressed as complaints of drowsiness, tinnitus, visual disturbances, dysarthria, and muscular twitches, followed by convulsions, coma, and respiratory and circulatory depression. Seizures must be treated immediately with inhaled oxygen, and if they persist, intravenous

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injection of an anticonvulsant such as diazepam (0.1 mg/kg), midazolam (0.05 mg/kg), or thiopental (4 mg/kg) (thiopental is preferable because it is faster acting) is required. Persistent convulsions require succinylcholine injection (1.5 to 2 mg/kg), intubation, and assisted ventilation to prevent acidosis.

Local anesthetics slow intraventricular conduction and can produce ventricular arrhythmias and fibrillation.^[8] The most cardiotoxic agent is bupivacaine because of its blocking effect on sodium, calcium, and potassium channels. Stimulation of the parasympathetic nervous system (due to cerebral toxicity) and hypothermia are aggravating factors. Cardiotoxicity is minimized by preventing hypoxia and acidosis. Cardiac arrest is managed by external cardiac massage, assisted ventilation with oxygen, intravenous sodium bicarbonate, and inotropic support ( Table 45-8 ). Ventricular tachycardia or fibrillation requires electrical defibrillation (3 to 6 J/kg) and administration of antiarrhythmic agents (e.g., amiodarone, 5 mg/kg). Bretylium tosylate (5 mg/kg) and phenytoin are no longer recommended in this condition. Based on experimental data, several agents may be helpful, including atropine (i.e., shortens the refractory period of the

TABLE 45-8 -- Emergency treatment of cardiac complications during a regional block procedure

Common Treatment for All Cardiac Complications

1. Facemask oxygenation followed by tracheal intubation and assisted ventilation with oxygen (because hypercapnia and hypoxia exacerbate toxicity)

2. Restore hemodynamics (external cardiac massage if required)

3. Prevention of metabolic acidosis with sodium bicarbonate

Semimolar (4.2%) into a central vein: 2 mL/kg/10 min (i.e., 1 mmol/kg/10 min)

Isotonic (1.4%) into a peripheral vein: 6 mL/kg/10 min (i.e., 1 mmol/kg/10 min)

4. Prevention or early treatment of seizure activity (with benzodiazepine)^*

Inotropic Support if Hemodynamics Are Not Restored

1. IV atropine: 0.02 mg/kg (not exceeding 0.6 mg)

2. IV vasoactive agents^†

Epinephrine: 0.1 mL/kg of a 1/10,000 solution (i.e., 10 µg/kg)

Dopamine or dobutamine: 2 to 10 µg/kg/min

Occasionally, isoprenaline: 0.1 µg/kg

3. Calcium chloride: 10 to 30 mg/kg

Additional Treatment in Case of Ventricular Tachycardia or Fibrillation

1. Defibrillation: 3 J/kg (up to a maximum of 6 J/kg)

2. Antiarrhythmic agents:

Amiodarone (5 mg/kg) in case of severe bupivacaine-induced arrhythmias

Classic recommendation for use of IV bretylium tosylate (5 mg/kg in repeat top-up doses up to 30 mg/kg) is no longer supported

3. Anticonvulsants (one)^‡

IV diazepam (0.1 to 0.2 mg/kg)

IV midazolam (0.05 to 0.1 mg/kg)

IV phenytoin (5 mg/kg over 10 min)

4. Inotropic support (one or both)^†

IV atropine: 0.02 mg/kg (not exceeding 0.6 mg)

IV dobutamine: 5 µg/kg/min

5. Lipid infusion and/or propofol infusion?^[159] ^*

*Indication based on experimental data only.
†Vasopressin (1 U/kg IV, once) may be the best vasoactive agent based on experimental data (which require clinical confirmation).^[159]
‡Thiopental should preferably not be administered in this situation.

**TABLE 45-8** -- Emergency treatment of cardiac complications during a regional block procedure
Common Treatment for All Cardiac Complications
1. Facemask oxygenation followed by tracheal intubation and assisted ventilation with oxygen (because hypercapnia and hypoxia exacerbate toxicity)
2. Restore hemodynamics (external cardiac massage if required)
3. Prevention of metabolic acidosis with sodium bicarbonate
Semimolar (4.2%) into a central vein: 2 mL/kg/10 min (i.e., 1 mmol/kg/10 min)
Isotonic (1.4%) into a peripheral vein: 6 mL/kg/10 min (i.e., 1 mmol/kg/10 min)
4. Prevention or early treatment of seizure activity (with benzodiazepine)^*
Inotropic Support if Hemodynamics Are Not Restored
1. IV atropine: 0.02 mg/kg (not exceeding 0.6 mg)
2. IV vasoactive agents^†
Epinephrine: 0.1 mL/kg of a 1/10,000 solution (i.e., 10 µg/kg)
Dopamine or dobutamine: 2 to 10 µg/kg/min
Occasionally, isoprenaline: 0.1 µg/kg
3. Calcium chloride: 10 to 30 mg/kg
Additional Treatment in Case of Ventricular Tachycardia or Fibrillation
1. Defibrillation: 3 J/kg (up to a maximum of 6 J/kg)
2. Antiarrhythmic agents:
Amiodarone (5 mg/kg) in case of severe bupivacaine-induced arrhythmias
Classic recommendation for use of IV bretylium tosylate (5 mg/kg in repeat top-up doses up to 30 mg/kg) is no longer supported
3. Anticonvulsants (one)^‡
IV diazepam (0.1 to 0.2 mg/kg)
IV midazolam (0.05 to 0.1 mg/kg)
IV phenytoin (5 mg/kg over 10 min)
4. Inotropic support (one or both)^†
IV atropine: 0.02 mg/kg (not exceeding 0.6 mg)
IV dobutamine: 5 µg/kg/min
5. Lipid infusion and/or propofol infusion?^[159] ^*

auriculoventricular node), vasopressin instead of or in addition to other vasoactive agents, lipid infusion, and infusion of propofol.^[159] However, the efficacy of these agents in clinical situations has to be established. Systemic toxicity (neurologic and cardiac) is increased in patients with right-left cardiac shunts.