Bottom line: No published evidence compares monitoring frequency (eg, q4, q8, etc.) to determine what is safest and most effective for monitoring dosage of neuromuscular blocking agents.  Professional recommendations advocate every 2-12 hours.

Summary:  ASA.  Practice guidelines for the prevention, detection, and management of respiratory depression associated with neuraxial opioid administration.  Anesthesiology.  2009; 110(2): 218-230.
Page 221 begins review of recommendations and evidence for effectiveness of methods for detecting respiratory depression, and on p. 222, recommendation by expert consensus for monitoring after single injection and continuous infusion depend on class of drugs (neuraxial lipophilic opioids v. neuraxial hydrophilic opioids), clinical condition of patient and concurrent medications.

AACN Procedure Manual for Critical Care, 6th ed. [In print at EUH]

Recommends train of four (TOF) testing every 4-8 hours during infusion after patient is stable and after optimal dose for neuromuscular blockade is achieved (p. 310.)  References guidelines (see below.)

Clinical practice guidelines for sustained neuromuscular blockade in the adult critically ill patient.  Crit Care Med.  2002;30:142-156.
In the monitoring section, the guidelines recommend monitoring but do not provide specifics.  They do however, cite a study (Kleinpell) that surveys ICUs about their practices, as well as one prospective study (Strange) that compares TOF to clinical assessment and one retrospective study (Frankel) about implementing standards for monitoring in a surgical unit.

(“Monitoring, Physiologic”[MAJR]) AND “Neuromuscular Blockade”[MAJR] AND (train-of-four OR electric stimulation) AND (prospective study OR observational study OR cohort study OR comparison study)
Here is a PubMed search for comparison and cohort studies evaluating train-of-four.  Some are evaluating specific devices or stimulation methods.  Baumann (2004) and Strange (1997) address the use of the TOF itself.

There is also an RCT by Rudis (1997) that compares clinical assessment to TOF for reduction in dose of neuromuscular nondepolarizing agent to maintain paralysis .

Reviewed by John Nemeth 4/14