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Learn how we develop our content. To learn more about Healthwise, visit Healthwise. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. Updated visitor guidelines. You are here Home » Epidural and Spinal Anesthesia. Top of the page. Topic Overview Epidural and spinal blocks are types of anesthesia in which a local anesthetic is injected near the spinal cord and nerve roots.
Credits Current as of: May 27, It was used successfully in the s for spinal anesthesia in New York, but fell out of favor due to concerns about poor tissue perfusion.
In particular, uteroplacental vasoconstriction was noted in somewhat-flawed pregnant animal models. Recent work has shown that fetal acidosis does not occur when usual doses are used. In addition, phenylephrine seems superior to ephedrine in reducing hypotension and nausea. Phenylephrine has been used as a bolus or as an infusion and has been used to treat hypotension prophylactically as well as reactively Table 9.
Optimal dosing regimens are yet to be established. Ngan Kee effectively prevented hypotension in elective obstetric patients by using a combination of crystalloid coload with a prophylactic infusion of phenylephrine.
Phenylephrine is the current vasopressor of choice for spinal hypotension, at least in the elective obstetric setting. There are, however, drawbacks. First, phenylephrine results in decreased CO, although the significance of this is uncertain.
Second, intravenous phenylephrine has been shown to decrease spinal nerve block height in pregnant and nonpregnant patients. Third, Cooper referred to two case reports of hypertensive crisis involving phenylephrine and atropine, resulting in significant morbidity. It is suggested that hypertension induced by vasopressors is limited by a reflex decrease in HR.
Atropine, in this setting, can therefore result in hypertensive crisis. Anesthesiologists more familiar with ephedrine may find this tiresome or, worse still, may commit a drug concentration error. Moreover, as a usual case requires much less than a mL bag of phenylephrine, there is a risk of cross contamination if bags are reused. Cardiovascular collapse can occur after spinal anesthesia, although it is a rare event. Bradycardia usually precedes cardiac arrest, and early, aggressive treatment of bradycardia is warranted.
Treatment of bradycardia includes intravenous atropine, ephedrine, and epinephrine. In cases of cardiac arrest after spinal anesthesia, epinephrine should be used early, and the Advanced Cardiac Life Support ACLS protocol should be initiated. Further work on spinal-induced hypotension is required. Although treatment is usually aimed at systolic blood pressure, mean blood pressure may be a better target. Different receptors may also be targeted.
For example, prophylactic intravenous ondansetron has been shown to reduce hypotension, perhaps by modulating the BJR. Different patient subpopulations may require different therapies. Most evidence pertains to the elective, healthy obstetric setting, and the extent to which this can be extrapolated to other groups remains to be seen. Last, despite published evidence of the benefits of phenylephrine over ephedrine for elective cesarean section, there is reluctance to change practice.
Psychological and institutional barriers to change need to be addressed. In patients with normal lung physiology, spinal anesthesia has little effect on pulmonary function. Lung volumes, resting minute ventilation, dead space, arterial blood gas tensions, and shunt fraction show minimal change after spinal anesthesia. The main respiratory effect of spinal anesthesia occurs during high spinal blockade when active exhalation is affected due to paralysis of abdominal and intercostal muscles.
During high spinal blockade, expiratory reserve volume, peak expiratory flow, and maximum minute ventilation are reduced. Patients with obstructive pulmonary disease who rely on accessory muscle use for adequate ventilation should be monitored carefully after spinal blockade. Patients with normal pulmonary function and a high spinal nerve block may complain of dyspnea, but if they are able to speak clearly in a normal voice, ventilation is usually adequate.
Arterial blood gas measurements do not change during high spinal anesthesia in patients who are spontaneously breathing room air. The main effect of high spinal anesthesia is on expiration, as the muscles of exhalation are impaired. Because a high spinal usually does not affect the cervical area, sparing of the phrenic nerve and normal diaphragmatic function occurs, and inspiration is minimally affected. Although Steinbrook and colleagues found that spinal anesthesia was not associated with significant changes in vital capacity, maximal inspiratory pressure, or resting end-tidal PCO2, increased ventilatory responsiveness to CO2 with bupivacaine spinal anesthesia was seen.
The sympathetic innervation to the abdominal organs arises from T6 to L2. Due to sympathetic blockade and unopposed parasympathetic activity after spinal blockade, secretions increase, sphincters relax, and the bowel becomes constricted.
Increased vagal activity after sympathetic nerve block causes increased peristalsis of the gastrointestinal tract, which can lead to nausea. Nausea may also result from hypotension-induced gut ischemia, which produces serotonin and other emetogenic substances.
Hepatic blood flow correlates to arterial blood flow. There is no autoregulation of hepatic blood flow; thus, as arterial blood flow decreases after spinal anesthesia, so does hepatic blood flow. If the mean arterial pressure MAP after placing a spinal anesthetic is maintained, hepatic blood flow will also be maintained.
Patients with hepatic disease must be carefully monitored, and their blood pressure must be controlled during anesthesia to maintain hepatic perfusion. No studies have conclusively shown the superiority of regional or general anesthesia in patients with liver disease. In patients with liver disease, either regional or general anesthesia can be given, as long as the MAP is kept close to baseline. Renal blood flow is autoregulated. The kidneys remain perfused when the MAP remains above 50 mm Hg.
Transient decreases in renal blood flow may occur when MAP is less than 50 mm Hg, but even after long decreases in MAP, renal function returns to normal when blood pressure returns to normal. Again, attention to blood pressure is important after placing a spinal anesthetic, and the MAP should be as close to baseline as possible. Spinal anesthesia does not affect autoregulation of renal blood flow. It has been shown in sheep that renal perfusion changed little after spinal anesthesia.
Many factors have been suggested as possible determinants of spinal blockade level. The four main categories of factors are 1 characteristics of the local anesthetic solution, 2 patient characteristics, 3 technique of spinal blockade, and 4 diffusion.
Characteristics of local anesthetic solution include baricity, dose, concentration, and volume injected. Patient characteristics include age, weight, height, gender, intra-abdominal pressure, anatomy of the spinal column, spinal fluid characteristics, and patient position. Techniques of spinal blockade include site of injection, speed of injection, direction of needle bevel, force of injection, and addition of vasoconstrictors.
Although all these factors have been postulated as affecting spinal spread of anesthetic, not many have been shown to change the distribution of blockade when all other factors that affect blockade are kept constant. The site of injection of local anesthetics for spinal anesthesia can determine the level of blockade. In some studies, isobaric spinal 0. However, no difference in nerve block height exists when hyperbaric bupivacaine or dibucaine is injected as a spinal anesthetic in different interspaces.
Some studies have reported changes in nerve block height after spinal anesthesia in the elderly patient as compared with the young patient, but other studies have reported no difference in nerve block height. These studies were performed with both isobaric and hyperbaric 0.
Baricity plays a major role in determining nerve block height after spinal anesthesia in older populations. Isobaric bupivacaine appears to increase nerve block height, and hyperbaric bupivacaine does not appear to change nerve block height with increasing age.
If there is a correlation between increasing age and spinal anesthesia height, it is not strong enough by itself to be a reliable predictor in the clinical setting. Just as with site of injection, it appears that baricity plays a major role in determining nerve block height after spinal anesthesia in older populations, and age is not an independent factor. Positioning of the patient is important for determining level of blockade after hyperbaric and hypobaric spinal anesthesia, but not for isobaric solutions.
Sitting, Trendelenburg, and prone jackknife positions can greatly change the spread of the local anesthetic due to effect of gravity. The combination of baricity of the local anesthetic solution and patient positioning determines spinal nerve block height.
The sitting position in combination with a hyperbaric solution can produce analgesia in the perineum. Trendelenburg positioning will also affect spread of hyperbaric and hypobaric local anesthetics due to the effect of gravity.
Prone jackknife positioning is used for rectal, perineal, and lumbar procedures with a hypobaric local anesthetic. This prevents rostral spread of the spinal blockade after injection.
Combined with Trendelenburg positioning, this may help cephalad spread. This position may inadvertently be attained when a urinary catheter is placed after spinal insertion. Speed of injection has been reported to affect spinal nerve block height, but the data available in the literature are conflicting. In studies using isobaric bupivacaine, there is no difference in spinal nerve block height with different speeds of injection. Even though spinal nerve block height does not change with speed of injection, a smooth, slow injection should be used when giving a spinal anesthetic.
If a forceful injection is given and the syringe is not connected tightly to the spinal needle, the needle might disconnect from the syringe with loss of local anesthetic.
Even though spinal nerve block height does not change with speed of injection, use a smooth, slow injection when giving a spinal anesthetic. It is difficult to maintain volume, concentration, or dose of local anesthetic constant without changing any of the other variables; thus, it is difficult to produce high-quality studies that investigate these variables singly. Axelsson and associates showed that volume of local anesthetic can affect spinal nerve block height and duration when equivalent doses are used.
Peng and coworkers showed that concentration of local anesthetic is directly related to dose when determining effective anesthesia. However, dose of local anesthetic plays the greatest role in determining spinal nerve block duration, as neither volume nor concentration of isobaric bupivacaine or tetracaine alter spinal nerve block duration when the dose is held constant. Studies have repeatedly shown that spinal nerve block duration is longer when higher doses of local anesthetic are given.
When performing a spinal anesthetic, be cognizant of not only the dose of local anesthetic but also the volume and concentration so the patient is not overdosed or underdosed. The use of hyperbaric solutions minimizes the importance of dose and volume except when doses of hyperbaric bupivacaine equal to or less than 10 mg are used.
In those cases, there is less cephalad spread and a shorter duration of action. A dose of hyperbaric bupivacaine between 10 and 20 mg results in similar nerve block height.
When using hyperbaric solutions, it is important to note that patient positioning and baricity are the most influential factors on nerve block height, except when low doses of hyperbaric bupivacaine are used. No single intervention guarantees asepsis. Therefore, a multiprong approach is advisable.
In the past, most institutions had reusable trays for spinal anesthesia. These trays required preparation by anesthesiologists or anesthesia personnel to ensure that bacterial and chemical contamination would not occur. Currently, commercially prepared, disposable spinal trays are available and are in use by most institutions. These trays are portable, sterile, and easy to use. Figure 9 shows the contents of a standard, commercially prepared spinal anesthetic tray.
The ideal skin preparation solution should be bactericidal and have a quick onset and long duration. Chlorhexidine is superior to povidone iodine in all these respects. In addition, the ideal agent should not be neurotoxic. Unfortunately, bactericidal agents are neurotoxic. It is therefore prudent to use the lowest effective concentration and allow the preparation to dry.
Although subject to debate, 0. Contamination of equipment with skin preparation can theoretically lead to the introduction of neurotoxic substances into neural tissue. Of more concern is accidental neuraxial injection of antiseptic solution, possibly from antiseptic solution and local anesthetic being placed in adjacent pots.
Therefore, after skin preparation, unused antiseptic should be discarded before commencement of the procedure and intrathecal drugs should be drawn directly from sterile ampules. Tinted antiseptic solutions may decrease the likelihood of drug error and allow easy identification of missed skin during application. Proving a benefit of individual infection control measures is difficult due to the rarity of infectious complications.
Past evidence has been contradictory. Yet, in there were calls for routine face mask use after it was unambiguously proven, using polymerase chain reaction PCR fingerprinting, that a case of Streptococcus salivarius meningitis originated in the throat of the doctor who had performed a lumbar puncture.
It is our strong belief that face mask wearing should be mandatory when performing spinal anesthesia. A American Society of Regional Anesthesia and Pain Medicine ASRA practice advisory recommended mask wearing in addition to removing jewelry, thorough hand washing, and sterile surgical gloves for all regional anesthesia techniques. Major components of an aseptic technique also included a surgical hat and sterile draping. Other international professional bodies have similar guidelines.
Prophylactic antibiotics are unnecessary for spinal anesthesia. If, as it happens, antibiotic prophylaxis is required for the prevention of surgical site infection, it may be prudent to administer antibiotics before insertion of a spinal needle. The reader is referred to Infection Control in Regional Anesthesia for more information.
Resuscitation equipment must be available whenever a spinal anesthetic is performed. This includes equipment and medication required to secure an airway, provide ventilation, and support cardiac function. All patients receiving spinal anesthesia should have an intravenous line. The patient must be monitored during the placement of the spinal anesthetic with a pulse oximeter, blood pressure cuff, and ECG.
Fetal monitoring should be used in the case of a pregnant patient. Noninvasive blood pressure should be measured at 1-minute intervals initially, as hypotension may be sudden.
Shivering and body habitus may make noninvasive blood pressure measurement difficult. Consideration should be given to invasive blood pressure monitoring if the patient has significant cardiovascular disease.
Needles of different diameters and shapes have been developed for spinal anesthesia. The ones currently used have a close-fitting, removable stylet, which prevents skin and adipose tissue from plugging the needle and possibly entering the subarachnoid space.
Figure 10 shows the different types of needles used along with the type of point at the end of the needle. The pencil-point needles Sprotte and Whitacre have a rounded, noncutting bevel with a solid tip. The opening is located on the side of the needle 2—4 mm proximal to the tip of the needle. The needles with cutting bevels include the Quincke and Pitkin needles. The Quincke needle has a sharp point with a medium-length cutting needle, and the Pitkin has a sharp point and short bevel with cutting edges.
Finally, the Greene spinal needle has a rounded point and rounded noncutting bevel. If a continuous spinal catheter is to be placed, a Tuohy needle can be used to find the subarachnoid space before placement of the catheter.
Pencil-point needles provide a better tactile sensation of the layers of ligament encountered but require more force to insert than bevel-tip needles. The bevel of the needle should be directed longitudinally to decrease the incidence of PDPH.
Small-gauge needles and needles with rounded, noncutting bevels also decrease the incidence of PDPH but are more easily deflected than larger-gauge needles. Introducers have been designed to assist with the placement of spinal needles into the subarachnoid space due to the difficulty in directing needles of small bore through the tissues.
Introducers also serve to prevent contamination of the CSF with small pieces of epidermis, which could lead to the formation of dermoid spinal cord tumors. The introducer is placed into the interspinous ligament in the intended direction of the spinal needle, and the spinal needle is then placed through the introducer.
Proper positioning of the patient for spinal anesthesia is essential for a fast, successful nerve block. It has been shown to be an independent predictor for successful first attempt at neuraxial nerve block. Before beginning the procedure, both the patient and the anesthesiologist should be comfortable.
This includes positioning the height of the operating room table, providing adequate blankets or covers for the patient, ensuring a comfortable room temperature, and providing sedation for the patient if required. Personnel trained in positioning patients are invaluable, and commercial positioning devices may be useful. When providing sedation, it is important to avoid oversedation. The patient should be able to cooperate before, during, and after administration of the spinal anesthetic.
There are three main positions for administering a spinal anesthetic: the lateral decubitus, sitting, and prone positions. A commonly used position for placing a spinal anesthetic is the lateral decubitus position.
Figure 11 shows a patient in the lateral decubitus position. It is beneficial to have an assistant to help hold and encourage the patient to stay in this position. Depending on the operative site and operative position, a hypo-, iso-, or hyperbaric solution of local anesthetic can be injected.
Strictly speaking, the sitting position is best utilized for low lumbar or sacral anesthesia and in instances when the patient is obese and there is difficulty in finding the midline. In practice, however, many anesthesiologists prefer the sitting position in all patients who can be positioned this way. The sitting position avoids the potential rotation of the spine that can occur with the lateral decubitus position. Using a stool for a footrest and a pillow for the patient to hold can be valuable in this position.
The patient should flex the neck and push out the lower back to open up the lumbar intervertebral spaces. Figure 12 depicts a patient in the sitting position, and the L4—L5 interspace is marked. If a higher level of blockade is necessary, the patient should be placed supine immediately after spinal placement and the table adjusted accordingly. The prone position can be utilized for induction of spinal anesthesia if the patient needs to be in this position for the surgery, such as for rectal, perineal, or lumbar procedures.
A hypobaric or isobaric solution of local anesthetic is preferred in the prone jackknife position for these procedures. This avoids rostral spread of the local anesthetic and decreases the risk of high spinal anesthesia. The prone position is utilized for spinal anesthesia if the patient needs to be in this position for the surgery, such as for rectal, perineal, or lumbar procedures.
The patient is then positioned in the prone position with vigilant monitoring, including frequent verbal communication with the patient. When performing a spinal anesthetic, appropriate monitors should be placed, and airway and resuscitation equipment should be readily available.
All equipment for the spinal blockade should be ready for use, and all necessary medications should be drawn up prior to positioning the patient for spinal anesthesia. Adequate preparation for the spinal reduces the amount of time needed to perform the nerve block and assists with making the patient comfortable. Proper positioning is the key to making the spinal anesthetic quick and successful.
Once the patient is correctly positioned, the midline should be palpated. The iliac crests are palpated, and a line is drawn between them to find the body of L4 or the L4—L5 interspace. Other interspaces can be identified, depending on where the needle is to be inserted. The skin should be cleaned with skin preparation solution such as 0. A small wheal of local anesthetic is injected into the skin at the planned site of insertion. More local anesthetic is then administered along the intended path of the spinal needle insertion to the estimated depth of the supraspinous ligament.
This serves a dual purpose: additional anesthesia for the spinal needle insertion and identification of the correct path for spinal needle placement.
Care must be taken in thin patients to avoid dural puncture, and inadvertent spinal anesthesia, at this stage. If the midline approach is used, palpate the desired interspace and inject local anesthetic into the skin and subcutaneous tissue. Next, the spinal needle is passed through the introducer. The needle passes through the subcutaneous tissue, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space, dura mater, and subarachnoid mater to reach the subarachnoid space.
Resistance changes as the spinal needle passes through each level on the way to the subarachnoid space. Subcutaneous tissue offers less resistance to the spinal needle than ligaments. Once this pop is felt, the stylet should be removed from the needle to check for flow of CSF. For spinal needles of higher gauge 26—29 gauge , this usually takes 5—10 seconds, but in some patients, it can take a minute or longer. Debris can obstruct the orifice of the spinal needle. If necessary, withdraw the needle and clear the orifice before attempting the spinal anesthetic again.
A common cause of failure to obtain CSF flow is the spinal needle being off the midline. The midline should be reassessed and the needle repositioned. If the spinal needle contacts bone, the depth of the needle should be noted and the needle placed more cephalad. If bone is contacted again, the needle depth should be compared with that of the last bone contact to determine what structure is being contacted. For instance, if bone contact is deeper than the first insertion, the needle should be redirected more cephalad to avoid the inferior spinous process.
If bone contact is at roughly the same depth as the original insertion, it may be lamina being contacted, and the midline should be reassessed. If bone contact is shallower than the original insertion, the needle should be redirected caudally to avoid the superior spinous process.
When the spinal needle needs to be reinserted, it is important to withdraw the needle back to the skin level before redirection. Only make small changes in the angle of direction when reinserting the spinal needle as small changes at the surface lead to large changes in direction when the needle reaches greater depths.
Bowing and curving of the spinal needle when inserting through the skin or introducer can also steer the needle off course when attempting to contact the subarachnoid space. Paresthesias may be elicited when passing a spinal needle. The stylet should be removed from the spinal needle, and if CSF is seen and the paresthesia is no longer present, it is safe to inject the local anesthetic.
A cauda equina nerve root may have been encountered. If there is no CSF flow, it is possible that the spinal needle has contacted a spinal nerve root traversing the epidural space. The needle should be removed and redirected toward the side opposite the paresthesia.
After free flow of CSF is established, inject the local anesthetic slowly at a speed of less than 0. Additional aspiration of CSF at the midpoint and end of injection can be attempted to confirm continued subarachnoid administration but may not always be possible when small needles are used.
Once local anesthetic injection is complete, the introducer and spinal needle are removed as one unit from the back of the patient. The patient should then be positioned according to the surgical procedure and baricity of local anesthetic given. The table can be tilted in either the Trendelenburg or the reverse Trendelenburg position as needed to adjust the height of the nerve block after testing the sensory level.
Local anaesthetics and other painkillers are injected using a fine needle into this space. Your anaesthetist will insert the needle and when they are certain that it is in the right position they will inject anaesthetic through it.
The time that the spinal lasts for varies but is usually 1 to 3 hours. Your anaesthetist will put enough anaesthetic through the needle to make sure that it lasts longer than the expected length of the operation. A spinal anaesthetic can be used for most people, usually giving a safe and effective form of pain relief both during and after an operation or procedure.
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Learn more here about the development and quality assurance of healthdirect content. The spinal anaesthetic can cause your blood pressure to drop. If this happens, your anaesthetist will give fluid into your drip and medicine to increase your blood pressure.
You might find that you find it difficult to pass urine. This happens especially in men. If this happens you might need a urinary catheter until the spinal anaesthetic has worn off completely and your bladder function returns to normal.
You might get a particularly bad headache that is caused by the spinal anaesthetic. This happens in 1 in to 1 in spinal anaesthetics given for young women giving birth but it is much less likely in an older person. Normally this type of headache resolves with rest, drinking plenty of fluids and taking simple painkillers.
Very occasionally you may require another procedure similar to the initial spinal anaesthetic to resolve the headache. If you get a bad headache after you have been discharged home it is important that you see your GP or attend hospital as you will need to be reviewed by an anaesthetist.
A high block - very occasionally the spinal anaesthetic can affect higher up the body than is needed for the operation. In this situation you may experience weakness of your arms and, in very rare situations, difficulty in breathing.
If this occurs your anaesthetist will explain to you what is happening and assist your breathing until the spinal anaesthetic wears off. Nerve damage. This is the complication that patients understandably worry most about. The risk of permanent nerve damage is extremely rare - about 1 in 50, The risk of temporary loss of sensation, pins and needles and sometimes muscle weakness is higher but usually resolves in a few days to weeks.
Headache after a spinal or epidural injection ; Royal College of Anaesthetists, February Nerve damage associated with a spinal or epidural injection ; Royal College of Anaesthetists, last updated February I have surgery on tuesday for the investigqtion of adno minal pains.
Despite having three general anesthic surgies last year i am territerrified of going under. Last time i was uncontrollable in the Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Egton Medical Information Systems Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions.
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