Sedation Levels for Intraspinal Injections
General anesthesia is generally deemed appropriate for interventional pain procedures requiring an incision, and the anesthesia professional fees are covered by insurance companies for these procedures. Examples of these type of procedures include spinal cord stimulation (SCS) and pumps to deliver intrathecal (IT) analgesics. For certain other interventional procedures, particularly percutaneous spinal treatment modalities such as radiofrequency (RF) lesioning or intraspinal steroid injections, clinical arguments surrounding the use of different levels of sedation are unresolved.
The clinical argument against deep sedation stems from the fear of undetected harm when a needle makes contact with neural tissue. It is claimed that a patient’s conscious ability to communicate about pain or paresthesia is needed to let the clinician know whether a neural structure is in danger of compromise. In this view, a heavily sedated and unaware patient poses a risk that could lead to harm and medical liability. But the safety benefit of patient wakefulness is also challenged. The placement of needles in a person who is fully awake, with only local anesthesia or light sedation, invites sudden movement that could also compromise safety and even cause grave harm.
Risks of Patient Movement
When a patient moves violently during an intraspinal injection, neurological damage can occur. According to the American Society of Anesthesiologists Closed Claims Project, of 284 chronic pain management claims, 276 (96 percent) were related to invasive procedures with blocks and injections and comprised 78 percent of the claims.1 Of the 276 claims for invasive pain procedures, 114 (or 40 percent) involved epidural steroid blocks and were associated with such serious injuries as nerve injury, infection, death, and brain damage. Sixty-one of 114 epidural steroid injections resulting in claims had used local anesthetics.1 When only local anesthetics are administered, some patients will respond violently to even small levels of stimuli. The longer a patient has experienced chronic pain, the more sensitive they are to smaller units of noxious stimuli. Myofascial irritation can produce as strong of a withdrawal reflex in some individuals as a needle making contact with neural tissue in other individuals.
Certainly many patients receiving intraspinal injection under local anesthetic have found them relatively painless. This actuality leads some clinicians and insurance companies to conclude sedation is unnecessary and certainly does not warrant the extra hassle or cost of an anesthesiologist. But when spinal injections cause neural damage, patient jerking and movement is often implicated. Several claimants in the ASA study complained of pain and sudden movement during the procedure.2 Some argue that pain and paresthesias are warning signs that, in the non-sedated individual, can prevent the sudden movement or jerking that can cause neural injury. However, as reported by Lofsky,2 it is the pain in the awake individual that triggers movement causing injury, rather than a case of sedation protecting the patient from injury.
It is apparent that the selection of sedation level may have extraordinary implications for safety. To put patients in the “twilight zone” of conscious sedation is often considered the logical compromise between total unconsciousness and complete alertness. One textbook author contends that, although sedation is undesirable to accomplish RF procedures, a wide variance in patient pain tolerance renders it “better to have a sedated patient than to have a non-sedated patient who moves on the table and whose muscles are tense.”3 The author argues in favor of light sedation, to engage the cooperation of the patient and, ostensibly, to prevent a potentially hazardous movement in non-sedated individuals.3 However, the choice of the “twilight zone” is perhaps the riskiest of all options, as the patient is neither fully cognizant enough to comply with instructions to remain immobile nor rendered incapable of movement as a fully sedated patient would be. Therefore, movement may be more, not less, likely under light sedation—indeed, it may be involuntary and not just because neural tissue has been compromised.
Because any type of pain triggers the reflex to move, patients respond not only to neural compromise but to contact with muscle, bone, and ligaments. Therefore, sudden movement is not an effective indicator of impending neural damage, as often argued, because more sites of contact provide more sites to trigger violent movement. A movement at the wrong moment could move neural tissue into the path of the needle.
Patient Protest is Unreliable as Safety Measure
Wakefulness does not guarantee a patient will respond to potentially harmful stimuli. For example, it was recently reported that for a person who had an epidural steroid injection without sedation, needle placement led to a puncture of the spinal cord and paraplegia.4 The physicians relied on the subject’s complaint of paresthesia or shooting pain to guide them. The complaint did not come. The patient did not react as the spinal cord was injected with the steroid. In this instance, consciousness failed to provide the expected protection after all.
There is another reason patient protest cannot be relied on as a safety measure, particularly in the treatment of patients who have experienced chronic pain and long term opioid therapy. A large percentage of these patients exhibit hyperalgesia, therefore, an invasive procedure produces an augmented pain response that is also more emotionally and physically demanding than would be experienced by the average individual. Not only is it compassionate to anesthetize these patients, but their typically heightened pain response renders it even more unsafe to allow for unrestrained pain reflexes.
Considerations for Appropriate Sedation
Careful patient selection, then, is an important consideration. Insurance coverage for anesthesia services should not be based upon the type of procedure the type of patient and risk of the procedure. A cervical intralaminar injection in a nervous hyperalgesic patient would probably be safer if the patient were anesthesized then if this patient were to receive only a local anesthetic. It is also important to maximize safety procedures such as real-time fluoroscopy, placing patients in optimal positions, standardizing medication and procedural approaches, and performing procedures in a fully monitored setting. Complete training in interventional procedures is perhaps the most essential safety measure.
In practice, clinicians must weigh the risks and benefits of interventional procedures with their own clinical expertise. The majority of physicians who do interventional procedures are anesthesiologists and physiatrists. Many clinicians do not have access to suites staffed with personnel to administer general anesthesia. Insurance payers, Medicare included, do not cover anesthesia for most intraspinal injections. This practice of denying anesthesia claims based on the procedure alone shortchanges medical decision-making and precludes the use of anesthesia to some patients whose safety would be better served to have the procedures performed under anesthesia.