Overview of Spinal Opioids in Anesthetic Practice
Regional anesthesia, which includes spinal, caudal, and epidural blocks, started being used for surgeries in the early 1900s. At first, there were concerns over its safety due to a few reports of lasting nerve damage. However, a large-scale study in the 1950s showed that these blocks are safe when done correctly and with sterile techniques, particularly with the safety advancements of the medications used in the injections. Originally used to better manage pain in cancer patients, spinal opioids are now often used to manage pain after surgery. (Katz, 1981; Cunningham, 1983; Vanstrum, 1988).
Spinal anesthesia is now considered safe and is sometimes the best or even the safest option under certain conditions. To provide surgical anesthesia, local anesthetics (medications to numb a specific area of your body) are used, but are usually paired with intrathecal opioids (powerful painkillers given into the spinal canal) to help with pain control during and after surgery. To manage ongoing pain, spinal opioids can also be used as single injections or more often through implantable pumps that slowly release the medication in your body.
Anatomy and Physiology of Spinal Opioids in Anesthetic Practice
The spine or backbone is made up of a series of bones called vertebrae and discs that act as cushions between them. The vertebrae are categorized into several regions: seven in the neck (cervical), twelve in the chest area (thoracic), five in the lower back (lumbar), and the sacrum at the base. Each vertebral level has a pair of nerves that connect to the brain and body.
The spinal cord, the main pathway for information connecting the brain and peripheral nervous system, sits within the vertebrae. It is protected by layers called the pia mater, arachnoid mater, and dura mater. The spinal cord usually reaches down to the first lumbar vertebra in adults and the third lumbar vertebra in children.
Surrounding the spinal cord and brain, we find a liquid called cerebrospinal fluid (CSF), which acts as a shock absorber to protect these areas from injury and also helps remove waste products. This fluid is largely produced in the lateral ventricles of the brain, with lesser amounts produced elsewhere. The volume of CSF in adults is about 150 mL, and it circulates from the brain to the spinal cord.
Morphine, a type of opioid medication, is often used to manage intense pain. It works by decreasing the excitability of nerve cells, increasing the threshold required for pain signals to be triggered. Morphine binds to specific receptors in the spinal cord and due to its hydrophilic (water-loving) nature, it moves slowly and provides long-lasting pain relief. An injection of intrathecal morphine (into the spinal canal) can provide pain relief for 18 to 24 hours after surgery.
On the other hand, other opioids such as fentanyl and sufentanil work faster, usually in 5 to 20 minutes, but their relief lasts only a few hours. These drugs also act on the brain, influencing sedation and breathing. The difference in effects and duration is due to the hydrophobic (water-repelling) nature of these opioids compared to the hydrophilic nature of morphine.
Why do People Need Spinal Opioids in Anesthetic Practice
During surgery, especially procedures that start quickly after a spinal injection like a caesarian section, spinal opioids combined with local anesthetic enhance the pain block, reducing the need for further painkillers afterwards. Fentanyl, a fast-acting drug, is often added to the mix during these situations to improve the effectiveness of pain relief during the operation. Post-operation, another drug called intrathecal morphine (ITM) is included for pain management. This combination is particularly helpful during surgeries where major incisions are needed or during a C-section, as it helps reduce the discomfort that comes from manipulation of the uterus.
Spinal opioids also play a crucial role in managing persistent cancer pain that isn’t relieved by other methods including systemic opioids, non-opioid analgesics, and other non-drug treatments. In this case, the intrathecal (IT) method directly delivers drugs into the CNS, the central nervous system, and is preferred over the epidural method. Why? Because epidural method would require doses about ten times higher and hence, leads to increased side effects. There are implantable IT infusion systems that facilitate this delivery. The decision to use an infusion pump generally depends on the patient’s condition, comfort, and life expectancy. If the patient has a longer life expectancy, doctors usually opt for fully implanted catheters and infusion pumps.
Spinal opioids for chronic pain management should only be considered after all other traditional treatments have proven unsuccessful. Before starting this treatment, the doctor will need to thoroughly assess the source of the pain and its effect on the patient’s daily life. It will involve using imaging studies to rule out any potentially treatable causes of pain, such as a tumor pressing on a nerve.
The use of neuraxial blockade, a technique of regional anesthesia, for surgeries has been shown to decrease post-surgery death rates and lower the chance of other serious complications like blood clots in the deep veins, lung embolism, pneumonia, respiratory depression, and the need for blood transfusions. Post-surgery, poor pain management can lead to numerous negative effects including instability in the body’s major systems, higher metabolic turnover, impaired immune response, and unusual blood platelet activation, making these methods particularly beneficial to those with ongoing health issues or those who have experienced heart surgery.
IT opioids can enhance the quality of the sensory block provided by the local anesthetic used alone. When properly administered, IT opioids can provide superior pain relief compared to epidural and intravenous (IV) methods. Plus, their side effects are mostly similar to that of systemic opioids, except that patients may experience itching more commonly. Finally, it’s more straightforward and easier to perform spinal anesthesia than epidural anesthesia.
When a Person Should Avoid Spinal Opioids in Anesthetic Practice
Some people cannot receive a spinal anesthetic, which numbs your body below the waist, for certain reasons. If a person refuses to have a spinal, has an inherited or developed bleeding disorder, has taken blood thinning or clot prevention medications, or has an infection at the site where the needle would be inserted, it is unsafe to perform a spinal.
A spinal anesthetic is also not suitable for people with a condition that increases the pressure inside their skull, such as a brain tumor. This is because the procedure has the potential to cause a severe condition known as brainstem herniation, where the brain tissue gets pushed out of its normal position.
Before receiving a spinal anesthetic, it is critical to gather the patient’s medical history, especially concerning any abnormal bleeding issues. This would include cases such as bleeding from the lining of organs, unusual bleeding after injury, dental work, or surgery, significant nosebleeds, or heavy menstrual periods. If there’s any sign or history of unusual bleeding, it’s important to consult a hematologist (a blood specialist) before receiving a spinal.
If there’s no case of unusual bleeding in the past, having a normal prothrombin time (a blood test to assess clotting), activated partial thromboplastin time (another clotting test), and platelet count (the blood cells that help stop bleeding) means a spinal anesthetic can safely be given. However, a mild variety of a bleeding disorder known as Von Willebrand disease may still be present.
There’s no agreed-upon blood platelet count below which a spinal anesthetic is considered unsafe. This varies based on the individual’s condition as well as from one medical center to another. Some older medical textbooks suggest a platelet count of at least 100 X 10^9/L, yet many doctors will administer spinal anesthesia even if the platelet count is lower, depending on the patient’s situation. This could be the case for a cancer patient with severe pain, or for a pregnant patient for whom general anesthesia could be risky due to obesity and an abnormal airway. In general, a platelet count of 75 X 10^9/L might be enough, but again this depends on other factors.
Having a low platelet count was not a barrier to spinal anesthesia even for patients with certain blood disorders as long as there was no history or signs of bleeding. In fact, it has even been proposed that a lower safe limit for healthy pregnant women who have no history or signs of bleeding might be 50 X 10^9/L.
In case the platelet count is low, tools such as the thromboelastogram (TEG) might be used to assess the function of the platelets, which helps doctors decide whether it is safe to administer spinal anesthesia. Patients with severe preeclampsia, a pregnancy complication characterized by high blood pressure, and a platelet count less than 100 X 10^9/L may have abnormal platelet function that can be picked up by this test.
Other factors can also complicate the delivery of a spinal anesthetic. This includes spinal stenosis (narrowing of the spaces within the spine), a history of spinal surgery, and spina bifida (a birth defect affecting the spinal cord). These conditions alter the structure of the spine and can make the spread of anesthesia unpredictable. Moreover, nerve injury has been reported in patients with these conditions after receiving spinal anesthesia.
Bacteremia, the presence of bacteria in the blood, is another factor that might make spinal anesthesia difficult to administer due to the risk of spreading the bacteria to the layers surrounding the spinal cord. However, if the benefits outweigh the risks and the patient has responded positively to antibiotic therapy, it might be safer to proceed with spinal anesthesia compared to general anesthesia.
Some heart conditions can affect the body’s response to spinal anesthesia. Patients who have low blood volume, an enlarged heart due to a condition called hypertrophic obstructive cardiomyopathy, or narrowed heart valves due to a condition called mitral stenosis, might have a significant drop in blood pressure in response to spinal anesthesia as it reduces the pressure in the blood vessels. Severe aortic stenosis, a condition characterized by narrowing of the main heart valve, is considered a strong reason not to administer spinal anesthesia due to the changes it can induce in the heart’s blood supply.
In the end, the decision to administer spinal anesthesia is always a balance of risks versus benefits and is decided on a case-by-case basis.
Equipment used for Spinal Opioids in Anesthetic Practice
In performing a spinal injection for pain relief (using opioids), the same resources used for spinal anesthesia with local anesthetics are required. Here is what will be used:
- Sanitized gloves, a face mask, and a sterile hat for the doctor to ensure cleanliness during the procedure
- An antiseptic solution which is a substance that prevents infection
- A clean, sterile sheet to cover the area where the procedure will be performed
- Monitoring devices like a pulse oximeter (measures the oxygen level in your blood), an electrocardiogram (ECG to measure the electrical activity of the heart), and a device to monitor your blood pressure
- A spinal anesthesia kit that includes spinal needles, local anesthetic (a drug to block sensations of pain from the injected area) for the injection site, and also to induce surgical anesthesia (numbing a larger area of the body)
- Emergency response equipment
- Extra equipment for expectant patients, such as a fetal monitor, may be necessary under certain conditions
Who is needed to perform Spinal Opioids in Anesthetic Practice?
A procedure involving neuraxial opioids, which are drugs that help manage pain in the spine and brain, is usually handled by a specific type of doctor called an anesthesiologist. These doctors have further specialized in managing pain. Alternatively, a spine specialist, who could be an orthopedist (a doctor who focuses on the skeleton and muscles) or a neurosurgeon (a doctor who operates on the brain and spinal cord), may perform the procedure.
A nurse is also often on hand to help out. They work in a clean and contamination-free environment, giving the doctor whatever they need during the procedure. This setup helps ensure that the procedure goes smoothly and effectively.
Preparing for Spinal Opioids in Anesthetic Practice
Before performing a spinal procedure, the doctor will need to examine the patient’s medical history and conduct several tests to rule out any bleeding disorders. They will also need to inquire about any medication being taken by the patient as some can increase the risk of bleeding. High volumes of alcohol consumption are also important to mention as alcohol, paired with aspirin or anti-inflammatory drugs, can foster excessive bleeding for up to two days. Patients who are prescribed 325mg of aspirin or a low dosage of an anti-inflammatory drug on a daily basis can generally undergo a spinal procedure without concern. However, it is noted that the break period for certain drugs prior to anesthesia does vary. Therefore, reference to the 2018 American Society of Regional Anesthesia and Pain Medicine guidelines would provide clarity on whether a safe period has passed since the patient’s last dose.
On the day of the procedure, the patient should be informed of the process, related risks and available benefits. The patient should also be aware of potential side effects which can include nausea, itching, headaches or other neurological complications. The doctor will also clarify to patients undergoing a caesarian operation that general anesthesia has been proven to be less safe than spinal anesthesia. Further, any headaches arising from the procedure are usually treatable. Fostering open communication with the patient at this point often results in patients asking for treat, including in some cases, a blood patch. Also, the risk of rare complications from the procedure such as neurological deficits, while rare (about 1 in 10,000 to 1 in 25,000), should be stated. Most of these problems usually improve over time.
There is one very rare complication, Subependymal Hemorrhage (SEH). This is internal bleeding in the brain which some believe is uncommon enough to neglect from discussion. However, it might be prudent to mention the risk, adding that in patients without bleeding disorders, the odds perhaps range from 1 in 100,000 to 1 in 200,000.
Prior to the procedure, the medical team would have prepared for any unexpected events. An intravenous line would have been set up, and vital sign monitors (ECG, pulse oximetry, and blood pressure) will be on hand throughout the procedure. There will also be advanced airway protection equipment available, with trained staff ready to use it. Before the procedure can commence, a checklist will be followed by the staff to ensure that all is in order.
How is Spinal Opioids in Anesthetic Practice performed
Spinal anesthesia is a type of pain-relieving medicine given through your back to numb your lower body. Sometimes, your doctor might use spinal anesthesia along with general anesthesia, which is a medicine to help you sleep during surgery. It’s usually done while you’re awake so you can let your doctor know if you’re having any pain or strange feelings. This might mean the needle is touching a nerve, and the doctor would then move it slightly to avoid any problems. There’s no solid proof, but some think this might help lower the odds of having nerve issues after your operation.
The procedure can be done with you either sitting up or lying on your side. Both positions work fine, but sitting might make it easier for the doctor to find the right spot for the needle. If you’re sitting, you’ll sit with your back straight and your arms resting on a table or holding a pillow. You’ll be asked to round out your back, kind of like an angry cat. A helper might also be there to help you hold your position and curve out your lower back. If you’re lying on your side, you’ll curl up in a ball, often referred to as the “fetal position.” Whichever position you’re in, the doctor will find the right spot for the needle by looking at the outside of your body. The needle goes in near a point in your lower back that is right in line with the top of your hip bones.
For both of these positions, a needle is put into the middle of your back or slightly to the side. Before the needle goes in, the area is cleaned with an antibacterial solution and needs to be kept some sterial. Then the doctor numbs your skin, often with a lidocaine shot. After this, an introducer (a thin, hollow tube) is inserted, which will help guide the spinal needle. You might feel some changes in sensation as the needle goes through different layers in your back. Once the needle is in the right spot, your medicines can be given.
Sometimes the doctor might not be able to use the usual approach due to problems like arthritis, spinal deformities, or difficulties with positioning. In such cases, the doctor might use a paramedian approach where the needle is slightly off to the side. Like the previous methods, this approach can be used for injecting local anesthetics and/or opioids.
Occasionally, a small amount of blood might be seen initially, but then it clears up. This happens if a blood vessel is accidently nicked by the needle. As long as the blood clears up, the procedure can continue. If there is difficulty with the needle insertion, your doctor might advise waiting a day or two before surgery, especially if you’ll be receiving a blood thinner such as heparin during surgery.
The timing of when spinal anesthesia is given can affect how long you get pain relief after surgery. If given before surgery, it can help lower the stress response as well decrease the doses of anesthetics and pain medicines needed during surgery. As a result, the benefits of getting it before the operation often outweigh having a few extra hours of pain relief afterward.
Just like with any medicine, spinal anesthesia can have some side effects. Back pain might occur due to bruising and/or inflammation in the area where the needle was inserted. This usually improves within a few days and can be treated with cold compresses and over-the-counter pain medicines. Shivering might occur in at least 40% of people. It usually happens with anesthesia and seems to be due to dilation of the blood vessels and a drop in body temperature. Nausea, vomiting, urine retention (having difficulty peeing), itchiness, and breathing troubles could also occur. These effects are similar to those seen with IV opioid medicines used to control pain, but the intensity can be higher with spinal opioids due to the direct insertion into the spine.
Serious breathing issues can occur at times, but this is often due to overdose. Itchiness is a common side effect of spinal opioids, and this can be effectively treated with medications like naloxone or ondansetron. Similarly, spinal opioids can also cause urine retention by acting on the spinal cord and the part of the brain that controls urination. Quiet, comfortable sleep could, at times, lead to unnoticed breathing troubles. These could be serious and possibly life threatening.
Possible Complications of Spinal Opioids in Anesthetic Practice
Sometimes, spinal block anesthesia may not work as predicted. This doesn’t necessarily mean there was an issue with the procedure, but it does need to be taken care of properly. The spinal block might not work if the needle moves while being inserted, if it doesn’t go fully into the space around the spinal cord, or if it is accidentally injected into a nerve. If this happens, it’s better to use general anesthesia. Trying to do the spinal block again could have serious side effects like very low blood pressure, a slow heart rate, and even breathing or heart problems.
After a spinal block, there’s a chance of developing a certain kind of headache (known as a post-dural puncture headache). The chance of this happening depends on the size of the needle used and the patient’s characteristics. For example, women, pregnant people, younger people, and people who have had these types of headaches before are more likely to get them. There are also certain positions and needles that can increase the risk. However, important complications like these are rare if the procedure is done correctly.
There’s also a small risk of nerve injury, breathing problems due to local anesthesia, and even a severe type of spinal bleeding (known as spinal epidural hematoma or SEH). If a patient starts having new symptoms after the spinal block, they need to see a neurologist right away and get a type of scan called an MRI. Quick treatment can increase the chances of recovery from this condition. We also need to remember that higher blood pressure and obesity can increase the risk of SEH.
Meningitis, an infection of the fluid and membranes covering the brain and spinal cord, can also occur following a spinal block. This can happen if tools were contaminated, if bacteria from the mouth of the practitioner somehow got into the patient’s body, or if the patient had some sort of infection already. However, the rate of meningitis after this type of procedure is relatively similar to the spontaneous rate of meningitis in the general population.
What Else Should I Know About Spinal Opioids in Anesthetic Practice?
Opioids are a type of powerful pain relief medicine that can be used during surgery, either by themselves or mixed with local anesthetic. They can help manage stress during an operation, reduce the amount of other anesthesia needed, and improve pain relief after surgery. For smaller or less complicated surgeries, a low dose of an opioid called fentanyl might be added to the local anesthetic. For surgeries that involve big cuts, a different type of opioid, called ITM, is usually given. Opioids can be useful for a few different types of surgeries, which we’ll explain below.
Opioids can also help control severe chronic pain, which is pain that lasts for a long time and doesn’t get better with most treatments.
In foot and ankle surgeries, which are usually done on an outpatient basis (meaning you go home the same day), a small amount of fentanyl is often the opioid of choice. It can make the pain relief from spinal block anesthesia better and can also help control pain for up to four hours after surgery. But because patients often go home quickly after these surgeries, some doctors prefer not to use opioids to avoid any side effects – like feeling sick, throwing up, or getting itchy – that might delay their going home.
In the case of C-section (Caesarean section) deliveries, a mix of a local anesthetic and an opioid is often the preferred method of anesthesia in the US and Canada. A study showed that using opioids makes the need for extra pain relief during surgery much less likely. Spinal or epidural anesthesia is generally better during a C-section than putting the patient to sleep because it avoids any problems with managing the patient’s breathing (which is more complex in pregnant women) and lowers the amount of blood lost during surgery. This method also means that the mom can be awake, have a loved one present, and start bonding with the baby quickly.
Spinal anesthesia is also useful for hip fracture surgery, especially in older patients. It can reduce the chances of blood clots, lung problems, and the need for blood transfusions. Patients who had knee replacement surgery and were given ITM as part of their anesthesia had lower pain levels 12 hours after surgery and used less pain medicine in the two days following surgery.
ITM has been successfully used in heart surgeries as well, leading to less postoperative pain and a decrease in the amount of other painkillers needed after surgery. Studies have shown that patients who received ITM were less likely to have lung problems after heart surgery and less likely to need a long hospital stay. It also helps patients recover more quickly after certain types of heart surgery. In children ages 3 months to 6 years old who had heart surgery, spinal block anesthesia with certain drugs resulted in less pain and a smaller need for other painkillers after surgery.
Patients who receive a spinal injection of ITM should have their alertness and breathing rate checked every hour for the first 12 hours and every two hours for the next 12. If patients have other health issues, are overweight, or are given certain other medicines or anesthesia methods, their sedation and breathing should probably be checked hourly for the full 24 hours after surgery. In high-risk cases, additional monitoring equipment may be needed. It’s crucial to remember that patients who are overweight are more likely to have slowed breathing.
