“What are the odds?”
I have discussed in lecture and in conversation the reasonable consideration of continuous peripheral nerve blocks when ACS is a potential risk and strategies we can utilize to optimize patient care and minimize the possibility of delaying the diagnosis of ACS. I was pleased to see this topic discussed in an article, “Pro-Con: Regional Anesthesia in the Patient at Risk for Acute Compartment Syndrome” in the most recent issue (May 2013) of ASRA NEWS, and this has prompted me to discuss some of my opinions and experience on the topic. I would highly recommend that you read the same article and consider studying some of the references as well.
I think it is always a reasonable question to ask before any intervention, “What are the risks of DOING this?” Having observed thousands of outcomes after performing continuous nerve blocks for an expanded range of cases and circumstances, I am now more pressed to ask the question, “What are the risks of NOT doing this?” Certainly, everything we ever do as clinicians is based on a risk-benefit ratio to the patient, and this scenario is no different. It is my estimation that within the context of a nerve block program with at least a moderately developed infrastructure and a thoughtful treatment strategy, the likelihood of masking the initial symptoms of an ACS and delaying a diagnosis is nearly non-existent. I would opine further that WITH a CPNB in a mature block program, you are MORE LIKELY to detect the earliest symptoms of an ACS. Allow me to explain.
The first consideration we should address is the patient population that you are likely to be treating, and the scenario in which the particular patient you are planning to block received their injury. If the patient was involved in a high-speed collision and sustains a midshaft tibia-fibula fracture, then an ACS is a real possibility. They might have up to a 1 in 10 chance in developing an ACS. In fact, if the clinical scenario warrants, the surgeon may need to consider performing a fasciotomy or fasciotomies preemptively. If the patient falls a short distance and lands awkwardly against something which leads to their midshaft radius-ulna fracture (primarily due to their poor bone quality), though we will remain vigilant, unless there are other significant factors, this patient has essentially no real risk of an ACS. For the sake of argument, we will still identify both patients as ‘at risk’ for an ACS; however, the extent to which I will alter my treatment plan will differ between these patients.
The second consideration is the essential element in the diagnosis of an ACS that occurs no matter the initial presenting symptom: a change! This is critical no matter what post-operative analgesia plan is selected. If the patient receiving IV morphine complains of escalating pain, and the response is to continue to give morphine more often, then the diagnosis will be delayed. If ongoing evaluation of pain to passive stretch is not performed, or if we are not actively seeking changes in sensation, then the diagnosis can be delayed. In neither scenario would I prescribe maintaining an anesthetic (vs analgesic) nerve block which would prohibit all neurologic evaluation of change to the nerve distribution that is at risk for an ACS.
Let me dispel another myth regarding ischemic pain.
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