37
Emergencies in the Pain Clinic

Asteghik Hacobian and Milan Stojanovic

Though an arrow is always approaching its target it never quite gets there, and Saint Sebastian died of fright.
—Tom Stoppard (1937–)

I. Procedure-related emergencies

1. Vasovagal syncope

2. Systemic local anesthetic toxicity

3. Complications of epidural and intrathecal procedures

4. Hypotension

5. Hypertension

6. Pneumothorax
II. Medication-related emergencies

1. Anaphylaxis

2. Opioid overdose

3. Opioid withdrawal

4. Steroid overdose and adrenal insufficiency
III. Conclusion
Selected Readings

The use of fluoroscopic guidance and contrast injection markedly decreases the complication rate of pain procedures. However, complications do occur and can have disastrous consequences if the clinic is not prepared to deal with these emergencies. This chapter reviews some of the emergency problems encountered in the pain clinic. Every pain management clinic specializing in interventional pain management procedures should be equipped with emergency equipment, including an airway cart, oxygen tanks, resuscitation equipment, and emergency medication, and all providers in the pain clinic should be familiar with their use and their location. Personnel trained in resuscitation should always be present in the clinic when patients are undergoing or recovering from procedures. Finally, a safety officer should be identified and given the responsibility for a regular check and documenting of the emergency equipment.
I. PROCEDURE-RELATED EMERGENCIES
1. Vasovagal syncope
Syncope is one of the most common reactions that occur in a pain clinic. Patients commonly fear needles and procedures. The best prevention is reassurance. If there is any suspicion that the patient may be very anxious, insertion of an intravenous (IV) line, with the consent of the patient, is recommended. Sometimes, an anxiolytic agent prior to the procedure is helpful, although anxiolytic agents may provide pain relief and diminish the diagnostic value of blocks. Unfortunately, vasovagal syncope can occur even during minor procedures.
Vasovagal syncope is always associated with brachycardia. During any kind of procedure, standard monitors, including noninvasive blood pressure cuff, pulse oximetry, and, in most cases, three-lead electrocardiography (ECG), should be used and patient baseline values documented.
To avoid possible patient injury from a fall due to loss of consciousness, avoid performing procedures in the standing and sitting position.
Symptoms and Signs
Pre-syncopal symptoms and signs include nausea, epigastric distress, perspiration, lightheadedness, confusion, tachycardia, and pupillary dilatation. Syncopal signs include loss of consciousness, generalized muscle weakness, loss of postural tone, pallor or cyanosis, and brief tonicoclonic seizure-like activity. Hypotension can also occur.
Treatment
In the event of any complaint from the patient, including feeling faint, nauseated, or sweating, do the following:

1.
Place the patient in the Trendelenburg position.

2.
Administer oxygen, evaluate and protect the airway, and support ventilation, depending on the severity of the case.

3.
Monitor oxygenation, ventilation, and vital signs.

4.
Establish IV access (if not present), and administer atropine 0.4 to 1 mg IV for a heart rate of less than 45 beats per minute or for a rapidly decreasing heart rate.

5.
Apply standard monitors and evaluate an ECG tracing for other possible causes of bradycardia (e.g., junctional rhythm).

6.
Continue to monitor, and keep patient supine.

7.
Make sure all the vital signs are stable and the patient is stable before being discharged home.
2. Systemic local anesthetic toxicity
Systemic local anesthetic toxicity can manifest as minor symptoms such as tinnitus, a metallic taste in the mouth, numbness of the lips, lightheadedness, or visual disturbance, or it may progress to loss of consciousness, seizure activity, and decrease in myocardial contractility.
Toxicity, which depends on the dose of local anesthetic being absorbed into the systemic circulation, may result from an accidental intra-arterial injection, an overlarge bolus, a high infusion rate, or too-frequent boluses. Toxicity can present either with central nervous system (CNS) manifestations or with cardiovascular symptoms, or with both. Cardiotoxic effects of local anesthetic include a depression of myocardial contractility and refractory arrhythmias. The CNS symptoms can progress to loss of consciousness, generalized seizure activity, or even coma.
Treatment

1.
The airway should be protected.

2.
Oxygen should be administered by mask or bag with the first sign of toxicity; in mild cases, this may be the only treatment needed.

3.
Airway, breathing, and circulation should be assessed and standard monitoring should be applied.

4.
If seizure activity interferes with ventilation, or if it is prolonged, give midazolam 1 to 2 mg IV or diazepam 5 to 10 mg IV.

5.
If the patient’s airway is compromised, give thiopental 50 to 200 mg and intubate the trachea; succinylcholine 1.5 mg/kg IV may be given to facilitate intubation; muscle relaxation abolishes muscle activity but the neuronal seizure activity continues.
Treatment of cardiovascular toxicity

1.
Airway, breathing, and circulation should be supported according to the acute cardiac life support (ACLS) protocol; oxygen should be administered and emergency assistance should be called.

2.
Ventricular tachycardia should subside over time as a result of drug distribution; adequate circulatory support, including lidocaine 100 mg IV, should be provided in the meantime.

3.
Bupivacaine-induced ventricular arrhythmia may be more responsive to bretylium 5 to 10 mg/kg IV every 15 to 20 minutes, to a maximum of 30 mg/kg, followed by lidocaine; prolonged cardiopulmonary resuscitation (CPR) or cardiopulmonary bypass may be required until the cardiotoxic effects subside.
3. Complications of epidural and intrathecal procedures
(i) Epidural hematoma
Epidural hematomas are extremely rare if coagulation parameters are normal. However, in a patient with rapid onset of neurologic deficit and severe back pain, the diagnosis it should be entertained. Sometimes the only symptom is severe pain in the back. The treatment includes immediate magnetic resonance imaging (MRI), steroids, and emergent surgical consult for decompression and laminectomy to evacuate hematoma.
(ii) Epidural abscess
Epidural abscess is a rare complication but it should be considered a possibility in a patient with severe back pain, local back tenderness, fever, and leukocytosis with or without neurologic deficit after an epidural or intrathecal injection or catheter placement. An immediate MRI, preferably with gadolinium enhancement, emergency surgical consult for possible decompression laminectomy, and IV antibiotics will be needed.
(iii) High spinal anesthetics
With fluoroscopy and contrast dye, the incidence of this complication is rare. However, it may still occur as a result of an unintentional subarachnoid injection of local anesthetic during an epidural, a celiac plexus block, a lumbar sympathetic block, a stellate ganglion block, or an occipital nerve block.
Symptoms and signs
These may include nausea, vomiting, hypotension, bradycardia, dyspnea, and high sensory level, and they can progress to apnea and unresponsiveness.
Treatment

1.
Establish an adequate airway, administer oxygen, assess sensory and motor level.

2.
Support ventilation if muscles of respiration are affected; if the airway cannot be protected, endotracheal intubation may be necessary.

3.
Support blood pressure and heart rate until the local anesthetic wears off.
(iv) Accidental overdose via neuraxial pump
Intrathecal or epidural pumps implanted on the anterior abdominal wall are a common mode of continuous delivery of opioids into the intrathecal or epidural space. Some of these pumps have two ports, the catheter access port and the drug reservoir port. In case of accidental overdose of morphine (the most common opioid used for intrathecal pump delivery), the patient may experience respiratory depression with or without CNS depression.
In the event of possible morphine overdose, do the following:

1.
Establish airway access, breathing, and circulation.

2.
Intubation may be necessary.

3.
Give naloxone 0.04 to 2 mg IV.

4.
Withdraw 30 to 40 mL of CSF through the catheter access port to decrease the concentration of morphine in the CSF.

5.
Stop the pump infusion.

6.
Monitor the patient’s vital signs.

7.
Repeat the dosage of naloxone every 2 to 3 minutes. Since the half-life of naloxone is considerably shorter than that of intrathecal or epidural morphine, repeated administration or continuous infusion may be necessary.
In severe cases, intrathecal naloxone may be indicated.
4. Hypotension
Acute systemic causes of hypotension include vasovagal syncope, allergic reaction, myocardial ischemia, adrenal insufficiency, and pulmonary embolism. Patients with a preexisting condition such as hypothyroidism, cardiac dysrhythmias, left ventricular dysfunction, or sepsis are predisposed to hypotension. Iatrogenic causes include the following:

Intrathecal or subdural injection of local anesthetic

High neuraxial block

Celiac plexus block (neurolytic or with local anesthetic) without adequate pre-block hydration

Lumbar sympathetic block

Tension pneumothorax

Rapid release of tourniquet during Bier block, causing release of drugs such as labetalol, guanethidine, and bretylium

IV phentolamine
Symptoms and signs include pallor, lightheadedness, vomiting, tachycardia, tachypnea, pupillary dilation, confusion, and decreased muscle tone.
Treatment

1.
Give supplemental oxygen.

2.
Put the patient in the Trendelenburg position or elevate lower extremities.

3.
Immediately establish IV access (if not already present).

4.
Give IV fluid (boluses of lactated Ringer’s solution) if not contraindicated.

5.
Monitor the patient’s vital signs, ECG tracing, oxygen saturation, and verbal communication.

6.
Administer if necessary; administer ephedrine 10 mg every 5 to 10 minutes, or phenylephrine in a bolus of 50 to 100 µg IV, or start a phenylephrine infusion of 100 µg/min and maintain at 40 to 60 µg/min.

7.
Depending on the cause, the patient may need to be transferred to an inpatient cardiology unit.
5. Hypertension
Hypertension could be the result of acute pain or an exacerbation of chronic pain. Anxiety, preexisting disease, and essential hypertension are other common causes. Rebound hypertension after a sudden discontinuation of alpha-blockers (e.g., clonidine) or beta-blockers (e.g., propranolol) can cause hypertension, and both these drugs are occasionally used as pain treatments. Drug interactions can cause hypertension (e.g., monoamine oxidase inhibitor interactions with meperidine, tricyclic analgesics, and ephedrine). Accidental vascular injection of vasopressors (e.g., epinephrine in local anesthetic solutions) or absorption of vasopressors from topical solutions (e.g., cocaine) can also induce hypertension. Other causes include hypoxia and hypercarbia.
Treatment

1.
Give supplemental oxygen.

2.
Ensure adequate ventilation.

3.
Treat underlying cause.

4.
Cancel planned procedures for diastolic blood pressure greater than 110

5.
Treat with nifedipine 10 mg sublingual or labetolol 2.5–5 mg IV every 5 to 10 minutes

6.
Depending on the severity, the patient may need to be transferred to an inpatient facility or be followed up with primary care physician
6. Pneumothorax
This may occur as a complication of intercostal nerve block, stellate ganglion block, celiac plexus block, intrascalene nerve block, supraclavicular nerve block, and trigger point injections in the chest and anterior abdominal wall. The incidence of pneumothorax with intercostal nerve blocks is actually rare in experienced hands. Pneumothorax has been reported with transforaminal selective thoracic epidural blocks. However, again in experienced hands, the incidence is very rare.
Symptoms and signs
A small pneumothorax usually causes no symptoms, although chest pain and dyspnea may occur. Depending on the severity of the pneumothorax, signs on physical examination include tachypnea, asymmetrical expansion of the chest on the affected side, deviation of the trachea away from the pneumothorax, hyper-resonance to percussion, and diminished breath sounds on the affected side. Despite these very specific diagnostic features, pneumothorax is actually very difficult to diagnose with a stethoscope, and a chest radiograph (taken in the upright position and at the end of maximal expiration) is often needed to confirm the diagnosis. Tension pneumothorax manifests as decreased breath sounds, wheezing, hypotension, and circulatory collapse.
Treatment

1.
If the situation is life-threatening and cardiovascular collapse is imminent, a large-bore 14-gauge catheter should be inserted in the midclavicular line in the second intercostal space just above the rib. To prevent air from entering the intrapleural space, a syringe should be placed over the catheter before insertion, followed by insertion of a chest tube with placement of waterseal and suction.

2.
Airway breathing and circulation should be supported and standard monitoring used. Oxygen should be administered.

3.
A small pneumothorax occupying less than 25% of the hemithorax in asymptomatic individuals can be treated on an outpatient basis without removing the area. Serial chest radiographs to exclude nonexpansion should be obtained. The pneumothorax should spontaneously resolve in 7 to 10 days.
II. MEDICATION-RELATED EMERGENCIES
1. Anaphylaxis
Signs and symptoms
Anaphylaxis presents with cardiovascular manifestations including hypotension, tachycardia, and dysrhythmias; pulmonary manifestations including bronchospasm, dyspnea, pulmonary edema, laryngeal edema, hypoxemia, and cough; and dermatologic manifestations including urticaria, facial edema, and pruritus. In its mildest form, there may simply be urticaria; in its worse form, there is complete cardiovascular collapse usually with severe bronchospasm.
Treatment

1.
Stop the administration of the drug.

2.
Administer oxygen.

3.
Assess the airway and ventilation.

4.
Intubate the patient if necessary.

5.
Administer epinephrine, the absolute treatment of choice, 50 to 100 µg IV; for persistent bronchospasm, give 0.5 µg/min IV, then titrate against the patient’s response.

6.
Administer IV fluids.

7.
H1 blocker (Benadryl 50 to 100 mg IV), H1 blocker (cimetidine50 to 300 mg IV) may be used.

8.
Steroids, hydrocortisone 5 mg/kg IV or dexamethasone 1 to 5 mg/kg IV may be used.
In the event of circulatory collapse

1.
Perform endotracheal intubation.

2.
Administer epinephrine 1 to 5 mg IV, or via endotracheal tube if no IV access; titrate to response.

3.
For cardiac arrest, follow ACLS protocol.
2. Opioid overdose
Symptoms and signs
Symptoms and signs include miosis, sedation, hypoventilation, apnea, and coma.
Treatment
First establish an airway, support ventilation and give supplemental oxygen. Give naloxone 0.04 to 0.4 mg IV. If the patient has been on chronic opioid therapy, it is wise to administer no more than 0.04 mg every 2 minutes, which will help avoid inducing a withdrawal syndrome. Because naloxone has a half-life of 1 hour, monitoring and repeated injections might be needed. Close monitoring and a naloxone infusion (0.5 to 1.2 mg/hr) might be required, depending on the half-life and mode of administration of the opioid being reversed. Because vomiting is associated with naloxone administration, it is safer to keep the patient in the lateral decubitus position to prevent aspiration (endotracheal intubation should also be considered).
When treating a patient on chronic opioid therapy, in whom opioid overdose is causing sedation but not significant hypoventilation, observation for a few hours is the best therapeutic approach.
3. Opioid withdrawal
Opioid withdrawal rarely causes life-threatening symptoms. The exception is the patient on chronic opioids who receives naloxone.
Signs and symptoms

Hypertension, nausea, vomiting

Aspiration pneumonia (a possible complication)

Fever, chills, runny nose, yawning, sweating, irritability, diarrhea, abdominal cramping, and muscle aches
Treatment
Resumption of opioid treatment, in general, is the best way to stop the withdrawal syndrome. Generally, 25% to 40% of the previous dose aborts most of the symptoms. In severe cases, clonidine 0.2 to 0.4 mg/day can be added. For symptomatic treatment of nausea, use prochlorperazine, metoclopramide, or droperidol. For treatment of muscle aches, use nonsteroidal anti-inflammatory drugs and for (see Appendix VIII for prescribing information). It may be helpful to admit the patient to an addiction service unit and taper the drug with monitoring.
For a full description of opioid tolerance and withdrawal, see Chapter 30 (IV).
4. Steroid overdose and adrenal insufficiency
When used inappropriately and excessively in a cyclical weekly fashion, epidural triamcinolone (150 to 300 mg) has been shown to suppress adrenal production of cortisol and the pituitary synthesis of endogenous corticotropin.
Symptoms and signs
Adrenal insufficiency presents as weakness, fatigue, hypotension, weight loss, and anorexia. In its ultimate form—adrenal crisis—nausea, vomiting, and abdominal pain may become persistent. Lethargy may deepen to somnolence. Hypovolemic shock may be precipitated, with a poor hemodynamic performance, although the latter is usually not evident when exogenous hormone is available because mineralocorticoid activity of the adrenal medulla is still maintained.
Treatment
Patients who have been treated with repeat epidural steroid injections within the last month may benefit from supplemental stress-dose steroids before major surgery, or if other stressors develop (e.g., infection, hypoglycemia in diabetes). Some authorities, however, do not give supplementary steroids unless their patients have been on high-dose systemic steroids. Most surgeons at Massachusetts General Hospital do not give prophylactic steroids to patients who have received epidural steroid injections.
Should acute adrenal insufficiency occur, immediate treatment is necessary. First-line therapy is fluid and electrolyte resuscitation and steroid replacement.
III. CONCLUSION
Many of the unwanted sequelae of pain procedures are lifethreatening and require immediate and expert intervention. It is important to be prepared for these events in terms of personnel training, equipment available, equipment maintenance, and protocol development. Bad events are rare, but vigilance and preparedness are necessary to avoid adverse outcomes.
SELECTED READINGS

1.
Barash PG, Cullen BF, Stoelting RK, eds. Clinical anesthesia. Philadelphia: Lippincott, 1989.

2.
Cousins M, Bridenbaugh P, eds. Neural blockade in clinical anesthesia and management of pain, 2nd ed. Philadelphia: Lippincott, 1988.

3.
Isselbacher K, Braunwald E, Wilson JD, eds. Harrison’s principles of internal medicine, 13th ed. New York: McGraw-Hill, 1994.

4.
Kay J, Findling JW, Ralf H. Epidural triamcinolone suppresses the pituitary-adrenal axis in human subjects. Anesth Anal 1994;79: 501–505.

5.
Levy JH. Allergic reactions during anesthesia. J Clin Anesth 1988;1:39–46.

6.
Moore DC. Regional block: A handbook for use in the clinical practice of medicine and surgery, 4th ed. Springfield, IL: Thomas, 1965.

7.
Orkin FK, Cooperman LH, eds. Complications in anesthesiology. Philadelphia: Lippincott, 1988.

8.
Wyngaarden JB, Smith LH Jr, Bennett JC, eds. Cecil’s textbook of medicine. Philadelphia: WB Saunders, 1992.