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EPIDURAL AND SPINAL BLOCK

COMPLICATIONS

 Leonel Canto Sánchez. M .D.

Arterial Hipotensión. This is the most common cardiovascular complication, and results from the sympathetic block. In the epidural block the incidence is much less frecuent versus spinal block, due to:
• The long onset time, that permits a vasodilation below the level of the block and vasoconstriction above the level of the block, in the case of the spinal block the onset time is short, and there is no chance to the patient to develop this compensatory mechanism.
• Usually in the case of spinal analgesia the level of the sympathetic block is higher in comparation of the sensory level, in the epidural block the levels of both are the same.
The prophylaxis of arterial hipotension include: administration of IV fluids, avoid supine position in the obstetric patient, never performe this blocks in patients with previous hipotension no matter the etiology. The treament is: a) Insuring normovolemia by administration of IV fluids, b) A marked fall in blood pressure requieres pharmacologic intervention with vasoconstrictor drugs like ephedrine or phenyleprine, c) Severe bradycardia is treated with atropine, d) Cardiovascular collapse is treated with ACLS methods.

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Back pain. The administration of chloroprocaine with EDTA preservative in the epidural space has been reported to produce severe back pain, recently the drug company put in the market this local anesthetic agent without preservative and the risk to produce back pain.

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Problems derived of the malposition of the catheter. Epidural catheters can curl and turn on themselves in the epidural space and actually form a knot such that be difficult to remove. This complication is usually due to attempts to advance excesive length of the catheter in the epidural space more than 3 cm (advance the catheter into the epidural space no more than 3 cm). When is not possible to advance the catheter in the epidural space, then the needle and the catheter should be withdrawn together, if the catheter is sheared informe the patient and no attempt should be made to retrieve the catheter segment, fortunately segments of catheter in the space rarely are associated with clinical significant problems. The epidural catheter can espontaneous migrate to a blood vessel or to the intrathecal space, this make very important the aspiration test of the catheter before the administration of drugs.

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Accidental Dural Puncture. This complication is the number one worry in the anesthesia practitioners of epidural blockades due to the annoying of the symptoms that suffers the patient, also for the necessity that this must be keeping rest in bed in order to don't percieve the headache.

The exact mechanism of postdural puncture headache (PDPH) mainly when the patient takes the seated o vertical position is unknow. Numerous studies have postulated that postdural puncture headache (PDPH) is due to the lost of spinal fluid (CSF) that causes a drop in the pressure in the intrathecal space. PDPH may also be caused by the reflex cerebrovasodilation in the coroid plexus wich is known to follow reduction in CSF volume, this would account for the beneficial effect of caffeine or theophyline both cerebral vasoconstrictor in the treatment of PDPH. Recently some authors mention in the etiology of PDPH the influence of the injection of air in the epidural space. Some people believe PDPH is influenced by psychologic factors.

The PDPH is typically located in the fronto-occipital region radiating to the neck and shoulders, and this intimately bound to the position of the patient, being classic that uprigth position conditions or increases the clinical symptoms and the supine position abolishes it. Sometimes the PDPH is accompanied by nausea, vomiting, diplopia, tinnitus and deafness, neck stiffness and cranial nerve palsy most commonly in the sixth nerve. The onset time of PDPH oscillates between 24 to 48 posterior hours to the dural puncture, however sometimes the PDPH could come immediately. The duration of the PDPH without treatment oscillates between five to seven days, lapsed this time period the patient usually has a complete and permanent relief of their symptoms.

Several factors exist that could increase the incidence of PDPH, they are: a) The age, as this increases the incidence of the PDPH decreases, b) The sex of the patient also influences the incidence of PDPH, some authors reported a higher incidence of PDPH in women especially pregnant than in men, a rational explanation for the role of gender in the etiology of PDPH is lacking.

In journals could be found a great amount of recommendations for treatment of PDPH, the more frequent will be mentioned next:

• Psychological support. This is very important because the patients that suffer of PDPH have a great fear to keep this symptom or any another sequel for the rest of their life, a wide range of emotions from misery, tears, panic, anger and resentment to aggression develops. There the importance to discuss with the patient during preanesthesia the risks and benefits of the epidural analgesia, as well as the possible complications, treatment and outcome of the same.
• Posture. The patient will remain in a comfortable horizontal position. Remembering that maintain the patient for many hours or days resting in bed doesn't modify the outcome of the PDPH, the only thing that is obtained with this is to differ the onset and the treatment of the PDPH.
• Hydration. With the objective of increasing the volume of the CSF for many years was recommended the additional hydration of the patients, however in the current moment scientific evidence doesn't exist that prove this fact, therefore the value of this therapy remains in interdict.
• Medications. A great amount of drugs has been used for the treatment of the PDPH, among them we could mention: steroides, analgesics, tranquilizers, vasopressin, etc., that have been tried without proven effect. The administration of caffeine has also been recommended because their effect of cerebral vasoconstriction, unfortunately there is a high index of recurrence rate of the PDPH, which has caused that at the moment the administration of caffeine is only a useful temporizing measure in the treatment of the PDPH, similar situation has been demonstrated for the administration of teophyline instead of caffeine. Recently good results in the treatment of PDPH with the application of serotonin receptor agonist drugs have been reported lending support to the vascular cause of PDPH, the cost of these medications has limited their use.

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Blood patch. The injection of autologous blood in the epidural space is at the moment the most effective treatment of the PDPH, an incidence of 96% has been reported of permanent and definitive cure of the PDPH in the patients that have received this treatment. Reason of discussion has been the amount of blood that should apply in the epidural space, the studies of Szeinfeld have concluded that a volume between 12 to 15 ml of blood is the most appropriate thing, because this is distributed along 7 to 14 segments, the mean spread was nine segments. The blood patch will indicate only until the moment in which appear the PDPH never before.

The injection of epidural blood immediately after the dural puncture that some publications have mentioned, is controversial regarding their possible benefice effects and to the potential risk of producing an infection in the epidural space. The quality of future epidural analgesia after blood patch has been addressed in several case reports, they did not detect a reduced efficacy of later epidural analgesia

The blood patch should be performed with meticulous attention to sterile technique. The risk of epidural abscess formation precludes its use in the presence of fever or other signs of infection. If the blood patch fails to relieve headache, most would consider a repeat patch justifiable. If this fails also some would repeat the patch, while others would try alternative therapy like epidural saline infusion during twenty four hours.

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Epidural saline. From the decade of the fiftyes some authors have recommended the application of physiologic saline solution through the epidural catheter when finishing the effect of the epidural block for prophylaxis of PDPH. The results that are obtained with this injection are not permanent, they only diminish the incidence of the PDPH and the necessity of applying a blood patch. The mechanism for which this effect takes place has been clarified recently for the studies of Hatfalvi. Barrios-Alarcon reports that the Dextran 40 administration in the epidural space instead of physiologic saline solution produces better results to which they are obtained with this last solution.

Finally we will mention the approaches that are recommended use in the moment in which dural puncture takes place: For preference will be attempted carry other epidural block in another interspace with the habitual technique, but diminishing a 25% the volume of the dose of the local anesthetic, with this routine fall notably the possibility PDPH in the patient. When finishing the surgical procedure and provided this for sure the epidural block has vanished completely, an injection of 30 ml of phisiologic saline solution is administered through the epidural catheter, previous test of aspiration of the same, and applying intermittent volumes of five cc.

During the postanesthetic period is not recommended to maintain the patient in bed rest, neither to force the administration of fluids, the only that advice are the administration of caffeine, by means of pills or drinks that contain this medication (in the case of out patient) or intravenous sodium benzoate caffeine ampules in lactated Ringer solution in hospitalized patient. If the patient presents PDPH, after this treatment, the following step will be the application of a epidural blood patch for preference in the same interspace in which the wet tap occur. Once finished the injection of blood in the epidural space will be maintained the patient in supine position for one hour, at the finish of this time we request to the patient that take the vertical position in order to value the result of this treatment. If the PDPH persist the patient for 24 hrs will be observed, in order to value, once lapsed this time the necessity of repeating the blood patch, just in case of persisting the PDPH.

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Subdural or subarachnoid accidental injection. The unnoticed administration of local anesthetic agentes in the subdural or intrathecal space is always a potential complication of the epidural blockade. In the case of subdural injection the most frecuent etiology is the rotation of the epidural needle when this is already in the epidural space, this produce the diffusion of the drug in the subdural space that is another potential space. Speaking about the accidental intrathecal injection the most frecuent etiology is the single shoot doses of the local anesthetic in the epidural space. The signs and symptyoms of this complications are very similar hemodynamic collapse with respiratory arrest, the only difference is: In case of subdural the onset time is longer 20 to 30 minutes and the signs and symptoms are less dramatic, in the intrathecal accidental injection the onset time is short almost immediate and the collapse is very deep. The treatment is CPR and the administration of vasoconstrictor agents, atropine some times and IV fluids, mechanical ventilation.

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Accidental Intravascular Injection. The injection of local anesthetic agents by accident in the intravascular space produce all the signs and symptoms of systemic toxicity of this drugs. The treatment is the same for local anesthetic systemic toxicity as was described previously in the lecture of local anestethic.

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Neurological complications. For their study and treatment these will be divided in, 1) Unrelated to anesthesia as patient position, surgical retractors, surgical trauma, tourniquet long pressure, cast or dresing aplication and undiagnosed neurologic diseases, and 2) Related to anesthesia, as trauma to nerve fibers with the needle or the catheter, accidental injection of drugs, anterior spinal artery syndrome, space occupying lesions such epidural hematoma or abscess and adhesive arachnoiditis. With epidural or intrathecal opiods: nausea, vomiting, itching, delay respiratory depression. In the spinal block the cauda equina syndrome, transient neurologic symptoms or transient radicular irritation. All of this complication will be review during the lecture the etiology, prophylaxis, diagnoses, treatment and outcome.

In recent years there has been interest in combining spinal with continuous epidural blockade in order to achieve a rapid onset time and prolong anesthesia duration. The technique is to locate initially the epidural space with an epidural needle, through witch the spinal needle is advanced into the intrathecal space, once the tip of the spinal needle is in the subarachnoide space we can injected here the dose of local anesthetic agent or narcotics or the mixture of both. The spinal needle is withdraw and an epidural catheter passed through the epidural space, and we can use this catheter to extend the duration of the block.

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