Objective NMT Monitoring in the ICU

Drug-induced neuromuscular blockade is often used in anesthesia to enable endotracheal intubation, optimize surgical conditions, and assist with mechanical ventilation in patients who have reduced lung performance. Neuromuscular blocking drugs, or agents (NMBAs), act by inhibiting signal transduction at the motor end plate, thus resulting in reversible paralysis of skeletal muscles.

The use of NMBAs as adjuvant therapy in the management of critically ill patients admitted in the intensive care unit (ICU) has been a debated topic. Nevertheless, recent data has provided a promising outlook for the potential role of these agents in the ICU setting, as their use in the setting continues to grow. 

Some of the common indications of NMBA use in the ICU are as follows:

• • Endotracheal intubation – The operating room provides a controlled environment for performing endotracheal intubation in a patient. However, the emergent intubation of a critically ill patient in the ICU carries an increased risk of complications, such as hemodynamic collapse and hypoxemia. The use of NMBAs has been shown to lower the rates of these procedure-related complications.
    
  • Status asthmaticus / Acute Asthma – The use of positive pressure mechanical ventilation may be associated with an increased risk of pulmonary barotrauma and hemodynamic collapse in patients with status asthmaticus. The risk of these complications can be reduced by the administration of NMBAs, which help maintain lower minute ventilation. This lowers airway pressures and optimizes respiratory rate and lung volume.

    Continuous infusions of NMBAs can be used to implement lung-protective ventilation strategies

  • Acute respiratory distress syndrome (ARDS) – Patients with ARDS develop non-cardiogenic pulmonary edema that is accompanied by severe hypoxemia. These patients are admitted to the ICU and are in need of mechanical ventilation. There is an increased risk of ventilator-induced pulmonary injury in these patients and this risk can be reduced with the help of lung-protective ventilation strategies, which include the use of low plateau pressures and low tidal volume. Continuous infusions of NMBAs can be used to implement these lung-protective ventilation strategies as they prevent spontaneous respiratory efforts and lower oxygen consumption by decreasing the work of breathing.^{1, 2}

The role of NMT monitoring in critically ill patients in the ICU

The use of NMBAs in the intensive care unit carries certain risks. These include intensive care unit-acquired weakness (ICU-AW), corneal abrasions, anaphylaxis, awareness during paralysis, residual neuromuscular blockade, and prolonged duration of mechanical ventilation. Moreover, different patient populations have been shown to respond differently to the administration of NMBAs. It is, therefore, important to implement specific monitoring protocols when using these medications.³ 

Keeping this in view, the Society of Critical Care Medicine (SCCM) has suggested the use of neuromuscular transmission monitoring, also known as “train-of-four” or TOF monitoring,  in critically ill ICU patients receiving NMBAs. According to SCCM, peripheral nerve stimulation (PNS) with train-of-four (TOF) monitoring may be used for monitoring the depth of neuromuscular blockade. It should be used as a part of a comprehensive care plan that includes a detailed clinical assessment of the patient.⁴

Benefits of utilizing quantitative NMT monitoring in the ICU

The dose-response relationship of an NMBA or the degree of neuromuscular blockade can be evaluated in the intensive care unit setting by using clinical assessment, qualitative/subjective NMT monitoring, or quantitative/objective NMT monitoring. The interpretation and accuracy of the results obtained by these methods may be influenced by several different factors, including the training experience of the ICU staff, the different types of equipment used for monitoring, and the patient characteristics, such as edema and hypothermia.  

In comparison to the other methods, the use of quantitative NMT monitoring offers some clear benefits over subjective methods:

• Objective monitoring – Quantitative NMT monitoring provides objective measurements and readable metrics such as TOF ratios, which takes the guesswork out of understanding the precise state of the patient’s neuromuscular block, leaving nothing to the subjective opinion of the ICU staff. A TOF ratio, or percentage, reading is displayed on the screen and the staff can make objective decisions regarding the dose adjustments for each patient beyond the basic number of twitches expected that is provided by subjective monitoring.
• Easy understanding of the results – The ICU staff can easily comprehend the paralytic state or the depth of neuromuscular blockade of the patient, based on the quantitative results. No calculations or further observations are needed on the part of the ICU staff, potentially assisting in ensuring the patient is not under or over paralyzed for their needs.
• Less room for errors – The simplification of the decision-making process helps ease some of the burden on the frontline ICU staff, thereby leaving less room for medical errors.  

How does the Stimpod NMS450X NMT Monitor fit in the ICU?

There are several features that make the Stimpod NMS450X+ an excellent option for quantitative NMT monitoring in the intensive care unit. Some of these features are discussed below:

• Simple to Use in the ICU – The Stimpod system is intuitive and easy to implement as standard. It requires limited training required for primary functions and to interpret data, and is customizable specifically for ICU clinician focus and use.
• Rapid Setup & Use at ICU Bedside –  The system features electrode placement verification for setup confirmation, it is capable of attaining TOF Data/Depth of Block State in under one minute, and the system will power up to last settings for ease and speed in monitoring the same patient over time.
• Ultimate in Portability and flexibility of use in ICU – The system is battery powered for maximum freedom of movement from bed to bed, ICU to ICU, building to building. It can be used quickly from the palm of your hand, obviating the need for wall-power, mounting, or setup space. The system features a compact carrying case for protected transport.
• Unbeatable Cost/Value Ratio for the ICU – The most economical system for Quantitative Monitoring, featuring the use of off the shelf electrodes for maximum cost-efficacy. 

NMT monitoring in COVID-19 Patients

The global pandemic of COVD-19 has resulted in a massive strain on healthcare systems all across the globe. The novel respiratory virus has been found to cause ARDS in patients. As with the other cases of ARDS, the use of NMBAs has been recommended for the facilitation of protective lung ventilation in COVID-19 patients.⁵ Quantitative NMT monitoring would thus be of great importance in these patients as well.

If you have any questions regarding the monitoring of COVD-19 patients in the ICU or the use of Stimpod in these patients, please reach out to us. 

Over 4 million patients are admitted to the intensive care unit in the US every year, and nowadays, ICU survivorship is a top concern. Optimizing patient recovery and outcomes have become important objectives for healthcare professionals and researchers. Several potential indications for the use of NMBAs in the ICU setting have been identified; however, there are certain risks associated with the use of these medications. Objective NMT monitoring in the ICU using state-of-the-art devices, such as the Stimpod NMS 450X+, offers the ideal solution.

References

1. Tezcan B, Turan S, Özgök A. Current Use of Neuromuscular Blocking Agents in Intensive Care Units. Turk J Anaesthesiol Reanim. 2019;47(4):273‐281. doi:10.5152/TJAR.2019.33269
2. DeBacker J, Hart N, Fan E. Neuromuscular blockade in the 21st century management of the critically ill patient. Chest 2017;151:697–706.
3. Workum JD, Janssen SHV, Touw HRW. Considerations in Neuromuscular Blockade in the ICU: A Case Report and Review of the Literature. Case Reports in Critical Care, 2020.
4. Murray MJ, DeBlock H, Erstad B, Gray A, Jacobi J, Jordan C, McGee W, McManus C, Meade M, Nix S, et al. Clinical practice guidelines for sustained neuromuscular blockade in the adult critically ill patient. Crit Care Med 2016;44:2079–2103.
5. Alhazzani W, Møller MH, Arabi YM, et al. Surviving Sepsis Campaign: guidelines on the management of critically ill adults with Coronavirus Disease 2019 (COVID-19). Intensive Care Med. 2020;46(5):854‐887. doi:10.1007/s00134-020-06022-5

Contributors

Christian Escobar, Roche Janse van Rensburg, Maruschka van der Bank, Lourie Höll

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