Question
When do we use neuromuscular blocking agents (NMBAs)?
Answer
Some indications for neuromuscular blocking agents (NMBAs) involve providing muscle paralysis during surgery, during endotracheal intubation, and when a patient is on mechanical ventilation. The closed head injury population can quickly become agitated with increased movements, leading to higher intracranial pressures (ICP) and complications. We administer NMBAs to assist in paralyzing muscle movements to maintain acceptable ICP pressures. Besides closed head injuries, trauma patients can also develop epileptic seizures that consume high oxygen amounts. The use of NMBAs reduces the patient's oxygen consumption during such seizures.
Types of Neuromuscular Blocking Agents:
- Depolarizing
- Succinylcholine
- Nondepolarizing
- Vecuronium
- Pancuronium
- Rocuronium
- Atracurium
- Cisatracurium
- Mivacurium
There are different types of neuromuscular blocking agents. NMBAs are categorized into two categories, depolarizing and nondepolarizing. Note that some NMBAs can cross the blood-brain barrier or are reversible, but others are not. There is only one depolarizing agent, Succinylcholine. Succinylcholine crosses the blood-brain barrier. It has a shorter onset and duration, which makes it ideal for intubation. The nondepolarizing agents do not cross the blood-brain barrier and have a more prolonged onset and duration. Nondepolarizing agents are practical for long-term use and are reversible. When we use a depolarizing agent for patients in surgery or on the mechanical ventilator, we can also deliver a nondepolarizing agent for long-term needs. Then when the patient is ready to wake up, we can administer the appropriate drug agent to reverse the effects.
Most patients in the ICU are on nondepolarizing drugs, usually on a drip, as they may have multiple things going on. Because a neuromuscular blocking agent only paralyzes the muscles, patients can still feel pain. Therefore, we need to remember that an analgesic or sedation must also be administered along with the neuromuscular blocking agents. When patients are ready to wean off the ventilator, they require tapering off both NMBAs and sedation medications.
This Ask the Expert is an edited excerpt from the course, Drug Agents for Respiratory Care, presented by Dr. Duane Reed, EdD, RRT, RCP.
