The use of neuromuscular blocking drugs in the intensive care unit: a US perspective

Respiratory muscle dysfunction: a multicausal entity in the critically ill patient undergoing mechanical ventilation

Respiratory muscle dysfunction, particularly of the diaphragm, may play a key role in the pathophysiological mechanisms that lead to difficulty in weaning patients from mechanical ventilation. The limited mobility of critically ill patients, and of the diaphragm in particular when prolonged mechanical ventilation support is required, promotes the early onset of respiratory muscle dysfunction, but this can also be caused or exacerbated by other factors that are common in these patients, such as sepsis, malnutrition, advanced age, duration and type of ventilation, and use of certain medications, such as steroids and neuromuscular blocking agents. In this review we will study in depth this multicausal origin, in which a common mechanism is altered protein metabolism, according to the findings reported in various models. The understanding of this multicausality produced by the same pathophysiological mechanism could facilitate the management and monitoring of patients undergoing mechanical ventilation.

Neuromuscular blockade and skeletal muscle weakness in critically ill patients: time to rethink the evidence?

Neuromuscular blocking agents are commonly used in critical care. However, concern after observational reports of a causal relationship with skeletal muscle dysfunction and intensive care-acquired weakness (ICU-AW) has resulted in a cautionary and conservative approach to their use. This integrative review, interpreted in the context of our current understanding of the pathophysiology of ICU-AW and integrated into our current conceptual framework of clinical practice, challenges the established clinical view of an adverse relationship between the use of neuromuscular blocking agents and skeletal muscle weakness. In addition to discussing data, this review identifies potential confounders and alternative etiological factors responsible for ICU-AW and provides evidence that neuromuscular blocking agents may not be a major cause of weakness in a 21st century critical care setting.

Impact of sustained neuromuscular blockade on outcome of mechanically ventilated children

BACKGROUND

Neuromuscular blocking agents (NMBA) are commonly administered to critically ill children in pediatric intensive care units (PICU) in the USA and Europe. Although NMBA are frequently used in PICU patients, their role in the PICU setting has not yet been clearly defined. The aim of this study was to describe the sustained administration of NMBA and its impact on outcome of PICU patients.

METHODS

A 3-year retrospective cohort study was conducted to compare mechanically-ventilated patients who received NMBA for at least 12 h with patients who did not (control group).

RESULTS

A total of 317 consecutive patients were ventilated over 3473 days. Patients were similar in age, weight and severity scores. Thirty-four children (10.7%) received NMBA. Compared with controls, the neuromuscular blockade (NMB) group had a longer duration of mechanical ventilation (13.7 vs 5.5 days, P= 0.000), longer PICU stay (20 vs 11 days, P= 0.000) and increased occurrence of ventilator-associated pneumonia (6.6 vs 4.1/1000 ventilator days, P= 0.010). The NMB use was not associated with higher mortality (8.8% vs 17.6%, P= 0.287) or longer hospital stay (30.5 vs 23 days, P= 0.117).

CONCLUSION

Although the use of NMBA was not associated with greater mortality, we found that sustained use of NMBA is associated with prolonged mechanical ventilation, longer PICU stay and higher incidence of ventilator-associated pneumonia when compared with controls. Larger studies are necessary to confirm these findings.

Use of Sedatives and Neuromuscular Blockers in a Cohort of Patients Receiving Mechanical Ventilation

OBJECTIVE

To describe the use of sedatives and neuromuscular blocking agents (NMBs) and their impact in outcome in an international cohort of patients receiving mechanical ventilation.

METHODS

We analyzed the database of a prospective, multicenter cohort of 5,183 adult patients who received mechanical ventilation for > 12 h. We considered that a patient received a given agent when it was administered for at least 3 h in a 24-h period.

RESULTS

A total of 3,540 patients (68%; 95% confidence interval [CI], 67 to 69%) received a sedative at any time while receiving mechanical ventilation. The median number of days of use was 3 (interquartile range [IQR], 2 to 6 days). The persistent use of sedative was associated with more days of mechanical ventilation (median, 4 days [IQR, 2 to 8 days], vs 3 days [IQR, 2 to 4 days] in patients who did not receive sedatives [p < 0.001]); more weaning days (median, 2 days [IQR, 1 to 3 days], vs 2 days [IQR, 1 to 5 days] in patients who did not receive sedatives [p < 0.001]); and longer length of stay in the ICU (median, 8 days [IQR, 5 to 15 days], vs 5 days [IQR, 3 to 9 days] in patients who did not receive sedatives [p < 0.001]). Six hundred eighty-six patients (13%; 95% CI, 12 to 14%) received an NMB for at least 1 day. The median number of days of use was 2 (IQR, 1 to 4 days). The administration of an NMB was independently related with age, a normal previous functional status, main reason of mechanical ventilation (patients with ARDS received more NMBs), and with patient management (patients requiring permissive hypercapnia, prone position, high level of positive end-expiratory pressure, and high airways pressure).

CONCLUSIONS

The use of sedatives is very common, and their use is associated with a longer duration of mechanical ventilation, weaning time, and stay in the ICU. NMBs are used in 13% of the patients and are associated with longer duration of mechanical ventilation, weaning time, stay in the ICU, and higher mortality.

The effect of neuromuscular blockade on oxygen supply, consumption, and total chest compliance in patients with high oxygen requirements undergoing mechanical ventilation

We investigated the effects of neuromuscular blockade with atracurium on oxygen consumption, oxygen delivery and total chest compliance in 20 sedated intensive care patients who required mechanical ventilation with an inspired oxygen fraction of at least 0.6. The reverse Fick method was used to measure oxygen consumption. Total chest compliance was measured from the ventilator pneumotachograph and pressure transducer. Measurements were made before neuromuscular blockade, at a standard level of neuromuscular blockade, and after demonstrated recovery of neuromuscular function. There was no statistical difference in any of the parameters measured. However there were large changes in oxygen consumption (range -35% to +17%) and total chest compliance (range -19.7% to +9.7%) in individuals. We conclude that in the setting of critical oxygenation, neuromuscular blockade cannot be assumed to reduce oxygen requirements or improve total lung compliance. If, however, neuromuscular blockade is selected as an adjunct to therapy, we recommend that the indices of oxygenation are calculated.

Neuromuscular-blocking drugs. Use and misuse in the intensive care unit

The use of NMB agents for more than 24 to 48 hours in critically ill patients is associated with many potential complications. Neuromuscular-blocking drugs should be used only when their use is essential for optimal patient care. The indications for neuromuscular blockade must be defined clearly, and patients should be evaluated during treatment for the need for continued muscle relaxation. The smallest doses of NMB agents that will accomplish clinical goals should be used. This dosage can be determined through clinical evaluations and peripheral nerve monitoring. It is essential that all patients treated with NMB drugs receive appropriate sedation and analgesia. Myopathies, neuropathies, and alterations of the neuromuscular junction can occur in the ICU setting, and nondepolarizing muscle relaxants seem to be involved in the development of these disorders. Clinicians should be aware of risk factors that may predispose certain patients to neuromuscular complications, including sepsis and the use of high-dose steroids. Neuromuscular-blocking agents should be avoided in these patients if possible. Although not proved, early recognition and treatment of iatrogenic neuromuscular complications may improve patient outcome.

Prospective documentation of sedative, analgesic, and neuromuscular blocking agent use in infants and children in the intensive care unit: A multicenter perspective

OBJECTIVE: To describe the use of neuromuscular blocking agents (NMBA) in critically ill children. DESIGN: Prospective cohort study. SETTING: Two pediatric intensive care units (ICUs). PATIENTS: All children who received NMBA in the ICUs during the study year. INTERVENTIONS: None Measurements: Data on use of NMBA agents and concurrent use of narcotic and sedative agents were collected. Demographic and outcome information was also obtained. MAIN RESULTS: NMBAs were used for either short-term (<6 hrs) or long-term neuromuscular blockade in 6%-9% of patient ICU days and for long-term blockade in 14%-16% of ventilatory support days. The overall mortality rate among ICU patients who received NMBA was 18%. Choice of agent varied between ICUs; however, succinyl choline was used in only 1% of cases for short-term neuromuscular blockade. The most frequent indication for long-term NMBA use was facilitation of mechanical ventilatory support (49%). Among these children, 46% received high frequency oscillatory ventilation. Long-term neuromuscular blockade was most frequently monitored by clinical examination rather than peripheral nerve stimulation. Paralysis for >6 hrs after discontinuation of NMBA was significantly more common when the agent was administered as an infusion instead of as bolus doses. Myopathy after long-term use of NMBA was seen in only 1 patient (0.4%). Doses (mg/kg) of NMBA did not significantly vary by patient age, but they did increase over time. CONCLUSIONS: Use of NMBA is more common in critically ill children than in reported studies of critically ill adults. Use of NMBA in critically ill children is associated with high severity of illness and mortality rates. Choice of NMBA and method of administration varies among providers. Concurrent use of narcotic and sedative agents with NMBA is frequent, but medication choice also varies among medical providers.

Neuromuscular blockade in children

Neuromuscular blocking agents (NMBAs) have been widely used to control patients who need to be immobilized for some kind of medical intervention, such as an invasive procedure or synchronism with mechanical ventilation. The purpose of this monograph is to review the pharmacology of the NMBAs, to compare the main differences between the neuromuscular junction in neonates, infants, toddlers and adults, and moreover to discuss their indications in critically ill pediatric patients. Continuous improvement of knowledge about NMBAs pharmacology, adverse effects, and the many other remaining unanswered questions about neuromuscular junction and neuromuscular blockade in children is essential for the correct use of these drugs. Therefore, the indication of these agents in pediatrics is determined with extreme judiciousness. Computerized (Medline 1990-2000) and active search of articles were the mechanisms used in this review.

Mature minors should have the right to refuse life-sustaining medical treatment

Imagine that you are a teenager and have cancer. You undergo a year of chemotherapy and after a brief return to normal life, you have a relapse. Your physician says that chemotherapy and radiation therapy could be tried, but a bone marrow transplant (BMT) is your only chance of a real cure. He tells you and your parents that you could die as a result of complications from the transplant, but without it you would only be expected to live one year. You and your family discuss the alternatives and decide to have the transplant. You ask what will happen if the BMT fails, but both your physician and your family tell you that right now you must fight to get better and not think negative thoughts. You do not ask any more questions.

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.

Muscle dysfunction in the intensive care unit

Muscle weakness, particularly impairment of the respiratory muscles, is a frequent abnormality in ICU patients. This is more relevant in some clinical situations--for example, in weaning patients from mechanical ventilation. Intensive care procedures that are designed to "rest" respiratory muscles, such as mechanical ventilation, may also contribute to impaired muscle function. Pharmacologic administration of glucocorticoids, several antibiotics, NMB agents, and so on has the potential to cause untoward effects. The development of myopathy and prolonged paresis has been increasingly recognized after prolonged use of these drugs in the ICU. Pathophysiologic changes in the nerve, muscle, or neuromuscular junction associated with the patient's underlying condition may also play a role in the development of impaired function. The assessment of muscle function is difficult and inaccurate. The techniques developed have a poor predictive value because of the difficulty in making the measurements in uncooperative patients and the lack of standardization. Furthermore, it is likely that some voluntary maneuvers underestimate muscle strength. Invasive procedures such as phrenic nerve stimulation or EMG recording are also of limited value.

[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.

Adjuncts to analgesia. Sedation and neuromuscular blockade

This article provides an overview of some of the current issues involved in sedation and anxiolysis in the intensive care unit. The problems involved in trying to monitor sedation levels are discussed, as are some of the newer options available for physiologic monitoring of the central nervous system. The problem of abnormal mental states in the intensive care unit and the range of antidepressant therapy now available are also covered. The importance of sleep deprivation and the properties of the neuromuscular blockers are also discussed.

A Perspective on the Use of Sustained Paralytic Therapy in Critically Ill Patients

While the patterns of use of neuromuscular blocking agents (NMBAs) in critically ill patients have undergone changes over the past decade, NMBAs are still used in the intensive care unit to facilitate mechanical ventilation. Prior to the initiation of neuromuscular blockade (NMB), clinicians should confirm that nonpharmacologic and pharmacologic strategies have not alleviated the need for NMB therapy. Recommended agents for use are pancuronium or vecuronium in hemodynamic instability.17 In patients receiving NMB therapy, the FDA recommends and clinical studies support an improved outcome with the use of peripheral nerve stimulation monitoring. There continues to be a need to provide education to health care clinicians regarding the dosing, monitoring, and unpredictable effects of NMB therapy.

Dose response, recovery, and cost of doxacurium as a continuous infusion in neurosurgical intensive care unit patients

OBJECTIVES

To determine the optimal dosing of doxacurium as a continuous infusion in neurosurgical patients with traumatic brain injury; to determine the effects of bolus administration of doxacurium on heart rate (HR), blood pressure (BP), and intracranial pressure (ICP); to monitor neuromuscular recovery after discontinuation of prolonged doxacurium infusion; and to compare the cost of doxacurium with other current neuromuscular blocking drugs.

DESIGN

Prospective, open-label study.

SETTING

Neurosurgical intensive care unit (ICU) of a university-affiliated teaching hospital.

PATIENTS

Eight critically ill, mechanically ventilated patients with traumatic head injury and normal renal and hepatic function. Patients had ICP monitoring.

INTERVENTIONS

A bolus injection of doxacurium (0.05 mg/kg) followed by a continuous infusion (0.015 mg/kg/hr), adjusted to maintain one twitch during Train-of-Four nerve stimulation of the adductor pollicis muscle.

MEASUREMENTS AND MAIN RESULTS

Bolus injections of doxacurium did not alter the HR, BP, or ICP. Patients were paralyzed 66 +/- 12 (SEM) hrs, with recovery of the fourth twitch occurring 118 +/- 19 mins after infusion of the doxacurium was discontined. There were no incidences of prolonged weakness, myopathy, or other adverse events.

CONCLUSIONS

Continuous infusion of doxacurium provides stable neuromuscular blockade for neurosurgical patients with traumatic brain injury. Doxacurium is devoid of clinically important interactions with HR, BP, or ICP and is less costly than other neuromuscular blockers used in the ICU.

Neuromuscular transmission and its pharmacological blockade. Part 4: Use of relaxants in paediatric and elderly patients, in obstetrics, and in the intensive care unit

The pharmacodynamic and pharmacokinetic characteristics of the non-depolarizing muscle relaxants are dependent on age. Thus differences are found between paediatric patients, adults, and elderly patients. Muscle relaxants cross the placenta and thus may cause problems in the fetus. Many of the potential adverse effects of relaxant administration are seen more pronounced in intensive care patients. Prolonged effects and problems in wearing patients from the ventilator are observed when muscle relaxants are used in such patients. Critical illness neuropathy is a syndrome different from relaxant induced neuromyopathy, but may be enhanced by relaxant administration.

The use of neuromuscular blocking drugs in intensive care practice

Critically ill patients represent a very different population from that of the operating theatre, but much of our knowledge of many of the neuromuscular blocking drugs is derived from intraoperative use. The diversity of clinical-practice and case-mix differences in intensive care are probably responsible for the absence of a formal consensus about the use of neuromuscular blocking drugs in the intensive care unit (ICU). Various surveys suggest that these drugs are used comparatively infrequently, but we do not know whether current usage is either safe or appropriate. In addition to the adverse effects which inevitably accompany prolonged paralysis and immobility, the steroidal relaxants, pancuronium and vecuronium, have also been associated with myopathy. This seems to be aggravated by concurrent use of pharmacologic doses of corticosteroids or the aminoglycoside antibiotics. Neither the mechanism nor the validity of the association with steroidal relaxants is known at present. Muscle dysfunction is a common feature of critical illness, and it is possible that neuromuscular blocking drugs interfere with muscle repair and regrowth. Patients with multiple organ failure present a particular challenge both because of the extent of tissue injury and because drug clearance via the liver or kidneys is generally impaired.

Comparison of the infusion requirements and recovery profiles of vecuronium and cisatracurium 51W89 in intensive care unit patients

The selection and administration of neuromuscular blocking (NMB) drugs in intensive care unit (ICU) patients remain controversial. We compared the dose-response and recovery pharmacodynamics of a new intermediate-acting NMB drug, cisatracurium besylate, to the intermediate-acting NMB drug, vecuronium (VEC), in a prospective, randomized, double-blind, multicenter study in critically ill adults. After informed consent, 58 mechanically ventilated ICU patients from five medical centers were randomized to receive either cisatracurium or VEC. Fifty-four of the 58 patients received NMB drugs before entering this study but demonstrated at least partial recovery (> or = one twitch) in the train-of-four (TOF) response before initiation of the NMB study drug. NMB drug infusion was titrated by peripheral nerve stimulation to maintain at least one twitch in the TOF response. NMB drugs were infused for 1-5 days. After discontinuation of NMB drug infusion, recovery of neuromuscular transmission was monitored with an accelerometer. NMB drug infusion for 28 cisatracurium patients averaged 2.6 +/- 0.2 (mean +/- SEM) micrograms.kg-1.min-1 with a mean duration of 80 +/- 7 h. After discontinuing cisatracurium administration, recovery to 70% TOF ratio averaged 68 +/- 13 min. The mean infusion rate for 30 VEC patients was 0.9 +/- 0.1 micrograms.kg-1.min-1 with a mean duration of 66 +/- 12 h. Neuromuscular recovery after VEC averaged 387 +/- 163 min, which was significantly longer (P = 0.02) than that after cisatracurium. Prolonged recovery of neuromuscular function after discontinuation of NMB drug infusion (identified by the primary investigator at each medical center) was reported in two cisatracurium patients and 13 VEC patients (P = 0.002), and occurred despite the routine use of neuromuscular twitch monitoring. Seven VEC and one cisatracurium patients died during the infusion of study drug or within 48 h after discontinuation of the NMB drug infusion. In summary, we found recovery of neuromuscular function after discontinuation of NMB drug infusion in ICU patients is significantly faster with cisatracurium than with VEC. In addition, routine neuromuscular monitoring was not sufficient to eliminate prolonged recovery and myopathy in ICU patients.

Double-blind, randomized, multicenter study of doxacurium vs. pancuronium in intensive care unit patients who require neuromuscular-blocking agents

OBJECTIVE

To compare the neuromuscular-blocking and hemodynamic effects of doxacurium vs. pancuronium administered by intermittent bolus to intensive care unit (ICU) patients who required neuromuscular block to facilitate mechanical ventilation for > or = 24 hrs.

DESIGN

A multicenter, prospective, double-blind, randomized study comparing doxacurium, a new benzylisoquinolone neuromuscular-blocking agent, with pancuronium.

SETTING

ICUs of three tertiary care hospitals.

PATIENTS

Forty critically ill patients (29 male, 11 female) with an average age of 52.5 yrs (range 19 to 80).

INTERVENTIONS

With approval of our Institutional Review Boards and after obtaining informed consent, 40 critically ill patients were entered into the study. Histories and the results of physical examinations were recorded, laboratory data were collected, and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were calculated during the 8 hrs before the start of the study medication. Patients received either doxacurium (initial dose of 0.04 mg/kg) or pancuronium (initial dose of 0.07 mg/kg) by bolus injection with continuous measurement of vital signs every minute for 15 mins. We measured the degree of neuromuscular blockade using a peripheral-nerve stimulator to measure the Train-of-Four count. Patients were rebolused (doxacurium dose of 0.025 mg/kg, pancuronium dose of 0.05 mg/kg) based on clinical criteria, which were substantiated by measurement of the Train-of-Four count. The neuromuscular-blocking drugs were stopped when the patient no longer required paralysis or after 5 days of therapy, whichever came first. Group comparisons were made using repeated measures analysis of variance, Fisher's exact test, and two sample t-tests, when appropriate. Spearman's rank-correction coefficients were calculated to assess the relationship of onset time and recovery time with all baseline laboratory values and the APACHE II scores. A p < .05 was used to establish statistical significance.

MEASUREMENTS AND MAIN RESULTS

There were no differences between the two groups with respect to age, gender, or APACHE II scores. There were no differences between groups in terms of adverse experiences, nor with respect to time of onset of block, number of doses, or the duration of neuromuscular blockade (2.6 vs. 2.2 days for doxacurium vs. pancuronium, respectively). There was a statistically significant increase in heart rate after the initial dose of pancuronium (120 +/- 23 vs. 109 +/- 22 beats/min postinjection vs. preinjection, respectively; p < .05) without any differences noted after doxacurium (107 +/- 21 vs. 109 +/- 21 beats/min, respectively). Furthermore, once neuromuscular block was discontinued, the pancuronium group had a more prolonged and variable recovery time (279 +/- 229 mins) compared with the doxacurium group (138 +/- 46 mins, p < .05).

CONCLUSIONS

In critically ill patients requiring neuromuscular block for > 24 hrs, doxacurium was well tolerated without evidence of tachycardia and with a relatively prompt recovery profile.