Mechanical ventilation involves the use of a machine to assist and support patient respiration, either partially or completely. Though invasive and often uncomfortable, mechanical ventilation may be necessary for patients in a severely compromised respiratory state. A number of conditions can lead to hypoxemia, including acute respiratory distress, bradypnea or apnea with respiratory arrest, lung injury, and decreased/inhibited respiratory capacity. Signs that a patient with respiratory issues likely needs mechanical ventilation include arterial blood pH less than 7.2, carbon dioxide pressure increasing by more than 5 mm Hg/h or greater than 55 to 70 mm Hg, or oxygen pressure less than 60 mm Hg on 100% oxygen delivered through a mask.1 Because of the discomfort of mechanical ventilation, neuromuscular blockade may be administered, among other drugs.
Patients frequently experience high levels of stress and pain related to respiratory interventions like intubation and mechanical ventilation. In order to improve this experience and treatment outcomes, physicians may administer a neuromuscular blocking agent (NMBA) in conjunction with sedation/anesthesia during the initiation of mechanical ventilation. Neuromuscular blockade induces temporary and reversible muscular paralysis, which in turn prevents the patient from “fighting” ventilation and inducing a patient self-inflicted lung injury.2 Notably, NMBAs are non-sedative, non-amnestic, and non-analgesic drugs; therefore, they must be given in careful conjunction with other anesthetic agents to ensure patient safety and comfort. Neuromuscular blockade has been associated with a number of improved factors during mechanical ventilation, including the reduction of ventilator-patient dyssynchrony, prevention of shivering and other involuntary movements that could lead to unwanted complications, reduction of airway stimulation-induced elevations of intracranial pressure, and improved facilitation of gas exchange through reduction of intra-abdominal pressure and increased chest wall compliance.3
Though one of the main indications for neuromuscular blockade is mechanical ventilation, there remains some contention as to (1) which patients should receive NMBAs in addition to mechanical ventilation, (2) the ideal timing of administration, and (3) the duration of administration for patients who require long-term mechanical ventilation. The current approach to NMBA administration in the ICU remains fairly conservative. NMBAs are typically reserved for patients whose ability to respirate on their own is severely compromised and who may require the assistance of mechanical ventilation for a long time. For example, a recent review of studies on ARDS patients reported that although NMBAs were beneficial and complementary to deep sedation in patients with moderate to severe symptoms in the first 24-48 hours of hospitalization, the authors did not recommend NMBA use for patients with mild ARDS.2 Instead, they argued that the relative benefit of NMBA use was overshadowed by the risk of NMDA-induced side effects and complications, of which there are many. Relevant complications include muscular paresis, ICU-acquired weakness, masking of seizures and other neuromuscular symptoms, incidents of deep vein thrombosis, and increased duration of mechanical ventilation, hospital stay, and overall recovery.3 Failure to induce sufficient sedation can also result in consciousness during paralysis, which can be a traumatic experience.3 Due to these concerns, the use of NMBAs for mechanical ventilation has significantly decreased over the years, with an observational study reporting NMBA administration in only 13 percent of mechanically ventilated patients.4
1 Brenner, B., Corbridge, T., & Kazzi, A. (2009). Intubation and Mechanical Ventilation of the Asthmatic Patient in Respiratory Failure. Proceedings of the American Thoracic Society. Retrieved August 15, 2022, from https://www.atsjournals.org/doi/full/10.1513/pats.P09ST4
2 Bourenne, J., Hraiech, S., Roch, A., Gainnier, M., Papazian, L., & Forel, J. M. (2017). Sedation and neuromuscular blocking agents in acute respiratory distress syndrome. Annals of translational medicine, 5(14), 291. https://doi.org/10.21037/atm.2017.07.19
3 Tezcan, B., Turan, S., & Özgök, A. (2019). Current Use of Neuromuscular Blocking Agents in Intensive Care Units. Turkish journal of anaesthesiology and reanimation, 47(4), 273–281. https://doi.org/10.5152/TJAR.2019.33269
4 Arroliga, A., Frutos-Vivar, F., Hall, J., Esteban, A., Apezteguía, C., Soto, L., Anzueto, A., & International Mechanical Ventilation Study Group (2005). Use of sedatives and neuromuscular blockers in a cohort of patients receiving mechanical ventilation. Chest, 128(2), 496–506. https://doi.org/10.1378/chest.128.2.496