Neuromuscular Blocking Agents in the Management of Respiratory Failure: Indications and Treatment Guidelines

Pharmacodynamics of cisatracurium in the intensive care unit: an observational study

Background

Data from previous studies indicate that optimal conditions for intubation are met 120 seconds after administration of 0.15 mg.kg^-1 cisatracurium (ED95 × 3) following the induction of anesthesia. The aim of this study was to compare the doses required for complete paralysis after induction of anesthesia in ICU patients with the dose used in patients undergoing elective surgery.

Methods

Seventeen ICU patients undergoing percutaneous tracheostomy and 17 patients undergoing an elective surgical procedure under muscle relaxation were included. In both groups, an initial intravenous bolus of cisatracurium besylate was given at a dose of 0.15 mg.kg^-1 followed by repeated boluses of 0.03 mg.kg^-1 every four minutes. The objective was to obtain no response to the train-of-four (TOF). The contractile response of the corrugator supercilii muscle was monitored every minute by observing the TOF in response to a peripheral nerve stimulator with a constant current set to 60 mA.

Results

After the initial dose of cisatracurium, none of ICU patients (0/17) versus 15/17 of the elective surgery patients were completely paralyzed (P < 0.0001). There was a delay in the onset of neuromuscular blockade among the ICU patients. The cumulative doses of cisatracurium were significantly higher in the ICU group with 38 ± 14 mg (that is, 10 ± 4.7 ED95) versus 11 ± 2 mg (that is, 3 ± 0.3 ED95) in the elective surgery group (P < 0.0001).

Conclusion

The dosing of cisatracrurium for ICU patients, which is based on the dose recommended for elective anesthesia, is unsuitable because the onset is too slow. This phenomenon is probably caused by changes in the pharmacodynamics and pharmacokinetics. These data suggest that neuromuscular monitoring should be used in the ICU.

Monitoring neuromuscular blockade in the intensive care unit: the peripheral nerve stimulator

Traditionally, neuromuscular blocking agents (NMBAs) have been administered in the operating room as an adjunct to anesthetics. Recent studies in the United States have indicated that 98% of the anesthesiologists and critical care nurses surveyed use NMBAs at least occasionally. When monitoring the use of NMBAs, a combination of clinical monitoring and peripheral nerve stimulator monitoring has been recommended. However, the most effective techniques have yet to be described. Understanding the complexities of NMBAs and the absolute need for accurate monitoring techniques is imperative for clinicians. The purpose of this literature review is to evaluate current literature regarding monitoring techniques of NMBAs and to guide the advanced practice nurse's role in critical care.

Clinical uses and controversies of neuromuscular blocking agents in infants and children

OBJECTIVE

To review the pharmacology of neuromuscular blocking drugs (NMBDs), their use in critically ill or injured infants and children, and the relevance of developmental changes in neuromuscular transmission.

DATA SOURCES

Computerized search of the medical literature.

STUDY SELECTION

Studies specifically examining the following were reviewed: a) the developmental changes in neuromuscular transmission; b) the pharmacokinetics and pharmacodynamics of all clinically available NMBDs in neonates, infants, children, and adults; and c) clinical experience with NMBDs in the critical care setting. Particular attention was directed toward studies in the pediatric population.

DATA SYNTHESIS

Neuromuscular transmission undergoes maturational changes during the first 2 months of life. Alterations in body composition and organ function affect the pharmacokinetics and pharmacodynamics of the NMBDs throughout active growth and development. Numerous NMBDs have been developed during the last two decades with unique pharmacologic profiles and potential clinical advantages. The NMBDs are routinely used in critically ill or injured patients of all ages. This widespread use is associated with rare but significant clinical complications, such as prolonged weakness.

CONCLUSIONS

Significant gaps in our knowledge of the pharmacokinetics and pharmacodynamics of NMBDs in infants and children continue to exist. Alterations in electrolyte balance and organ-specific drug metabolism may contribute to complications with the use of NMBDs in the critical care arena.

[The use of curare-like agents in resuscitation]

OBJECTIVE

To analyse current data on use of neuromuscular blocking agents (NBA) in the intensive therapy unit (ITU) patients and to propose practice guidelines.

DATA SOURCES

We did a Medline search of French and English language articles on NBA administration in ITU patients from 1960 to 1998. Data were also selected from our own collection of articles and books.

STUDY SELECTION

Original articles, clinical cases, letters to the editor and review articles were considered.

DATA EXTRACTION

Data on pharmacology of NBA in the ITU patient were extracted, as well as data on administration patterns and cost.

DATA SYNTHESIS

The indications for myorelaxation in ITU patients include either short term use, as in anaesthesia, or long term administration for facilitation of mechanical ventilation, control of increased intracranial pressure, status epilepticus, tetanus and oxygen demand in case of muscular hyperactivity, diagnostic and therapeutic procedures facilitation. A beneficial effect of NBA on the prognosis of the disease for which these agents have been used is not yet proven. Suxamethonium, because for its short onset time and duration of action, is the agent of choice for endotracheal intubation if myorelaxation is required. Among the benzylisoquinolines, atracurium and besilate of cisatracurium are convenient agents in ITU patients, whereas mivacurium is of no special interest. Among the aminosteroids, pancuronium and vecuronium are the most often used agents in the ITU. Rocuronium has not yet been extensively assessed. Myorelaxants carry risks for morbidity and mortality. The difficulty to assess the neurological status and the level of sedation is a recognised adverse effect. An accidental disconnection from the circuit and the resulting asphyxia is nowadays recognised without delay by the ventilator. NBAs increase the rate of bronchopulmonary infections. Cardiovascular complications include extreme bradycardia or sinus arrest following vecuronium administration, and cardiac arrest after suxamethonium injection mainly in burned or traumatised patients. Conversely to anaesthesia, NBAs do not carry a significant risk for anaphylactic or anaphylactoid complications in the ITU. Tachyphylaxis occurs mainly in burns and other pathologies modifying acetylcholine receptors. Neuromuscular complications include myopathy from steroids, postparalytic syndrome, deconditioning syndrome and intensive care polyneuropathy. Prolonged curarisation after discontinuation of NBA administration has a multifactorial origin and must be differentiated from neuromuscular complications. For prolonged neuromuscular blockade, pancuronium, vecuronium and atracurium are the agents of choice. The association with an adequate sedation is essential. Assessment of depth of neuromuscular blockade is not based on clinical symptoms but on train-of-four (TOF) twitch monitoring. A convenient basic relaxation is usually obtained with the suppression of the two last responses to TOF.

CONCLUSION

The use of NBA in ITU patient should result from a rational decision making procedure, the blockade titrated with a TOF monitor and maintained as superficially and shortly as possible.