Prolonged Muscle Weakness After Neuromuscular Blockade in the Intensive Care Unit

[Deep versus moderate neuromuscular block during one-lung ventilation in lung resection surgery]

BACKGROUND AND OBJECTIVES

Neuromuscular relaxants are essential during general anesthesia for several procedures. Classical anesthesiology literature indicates that the use of neuromuscular blockade in thoracic surgery may be deleterious in patients in lateral decubitus position in one-lung ventilation. The primary objective of our study was to compare respiratory function according to the degree of patient neuromuscular relaxation. Secondary, we wanted to check that neuromuscular blockade during one-lung ventilation is not deleterious.

METHODS

A prospective, longitudinal observational study was made in which each patient served as both treated subject and control. 76 consecutive patients programmed for lung resection surgery in Gregorio Marañon Hospital along the year of 2013 who required one-lung ventilation in lateral decubitus were included. Ventilator data, hemodynamic parameters were registered in different moments according to train-of-four response (intense, deep and moderate blockade) during one-lung ventilation.

RESULTS

Peak, plateau and mean pressures were significantly lower during the intense and deep blockade. Besides, compliance and peripheral oxygen saturation were significantly higher in those moments. Heart rate was significantly higher during deep blockade. No mechanical ventilation parameters were modified during measurements.

CONCLUSIONS

Deep neuromuscular blockade attenuates the poor lung mechanics observed during one-lung ventilation.

Optimizing drug therapy in the surgical intensive care unit

This article provides a review of commonly prescribed medications in the surgical ICU, focusing on sedatives, antipsychotics, neuromuscular blocking agents, cardiovascular agents, anticoagulants, and antibiotics. A brief overview of pharmacology is followed by practical considerations to aid prescribers in selecting the best therapy within a given category of drugs to optimize patient outcomes.

Critical illness neuromuscular abnormalities

CINMAs occur commonly in acutely critically ill inflamed patients, and can prolong respiratory failure, lead to ventilator dependency, and contribute to the development of chronic critical illness. The etiology of NMDs are diverse and overlap, and distinguishing different disease entities by clinical exam and electrophysiologic studies can be difficult. CIP, which has been the most widely studied CINMA, represents the peripheral nervous system manifestation of the MODS. Patients with CIP, particularly those with severely reduced nerve function, have a prolonged rehabilitation and a high mortality rate. Although there are no definitive treatments, diagnosing a CINMA may provide helpful prognostic information. Future preventative measures may include immunoglobulin, nerve growth factors, or strict glycemic control, although in the CCI phase general supportive care is given, including prevention of iatrogenic complications, nutritional support, psychosocial support, and physical therapy. The early recognition of CINMAs and prevention of associated complications are important to enabling CCI patients with CINMAs to recover and return home with an acceptable functional level and quality of life.

Agreement between muscle movement and peripheral nerve stimulation in critically ill pediatric patients receiving neuromuscular blocking agents

OBJECTIVE

The purpose of this study was to determine the degree of agreement between clinically observed muscle movement(s) and train-of-four scores obtained by peripheral nerve stimulation during a neuromuscular blocking agent infusion and after it was discontinued.

DESIGN

The study included a method-comparison design.

SETTING

Subjects were located in the pediatric intensive care unit of a metropolitan children's hospital.

PATIENTS

Study patients included 27 children who required neuromuscular blocking agent infusions.

OUTCOME MEASURES

Outcome measures were determined by clinical observation of muscle movement and train-of-four scores obtained from peripheral nerve stimulation during and after a neuromuscular blocking agent infusion.

RESULTS

Poor agreement was found between observed muscle movement and corresponding train-of-four scores during therapeutic infusions (most kappa were less than 0.30), whereas fair to substantial agreement was found between the 2 techniques after the infusion was discontinued (kappa ranging from 0.34 to 0.70).

CONCLUSION

Until additional research is available, nurses must titrate the neuromuscular blocking agent infusion on the basis of the clinical endpoints for paralysis in combination with an assessment of the child's movements and response to peripheral nerve stimulation to prevent overdose and prolonged muscle paralysis.

[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.

Weaning from mechanical ventilation

For the ventilator-dependent patient, weaning should be accomplished by withdrawing support safely, efficaciously, and efficiently. Success depends largely on physiologic determinants of respiratory system function, avoidance of ventilator-associated complications, and attention to patient readiness. Recent clinical trials, predictors of weaning, current techniques of weaning, the concept of reloading the respiratory pump, and determinants of ventilator dependency are all discussed.

Medical and ventilatory management of status asthmaticus

Despite improved understanding of the basic mechanisms underlying asthma, morbidity and mortality remain high, especially in the "inner cities." The treatment of choice in status asthmaticus includes high doses of inhaled beta 2-agonists, systemic corticosteroids, and supplemental oxygen. The roles of theophylline and anticholinergics remain controversial, although in general these agents appear to add little to the bronchodilator effect of inhaled beta-agonists in most patients. Anti-leukotriene medications have not yet been evaluated in acute asthma. Other therapies, such as magnesium sulfate and heliox, have their advocates but are not recommended as part of routine care. If pharmacological therapy does not reverse severe airflow obstruction in the asthmatic attack, mechanical ventilation may be temporarily required. Based on our current understanding of ventilator-induced lung injury, optimal ventilation of asthmatic patients avoids excessive lung inflation by limiting minute ventilation and prolonging expiratory time, despite consequent hypercapnia. Unless respiratory function is extremely unstable, the use of paralytic agents is discouraged because of the increased risk of intensive care myopathy. Patients who have suffered respiratory failure due to asthma are at increased risk for subsequent death due to asthma (14% mortality at 3 years) and should receive very close medical follow-up. In general, severe asthmatic attacks can best be prevented by early intervention in the outpatient setting. In the words of Dr. Thomas Petty, "... the best treatment of status asthmaticus is to treat it three days before it occurs".

Acute weakness syndromes in critically ill patients--a reappraisal

Over the last twenty years, increasing numbers of critically ill, mechanically ventilated patients who develop acute profound muscle weakness have been described. These acute weakness syndromes have not been well understood and they have been given many names including: acute steroid myopathy, acute quadriplegic myopathy, the floppy person syndrome, critical illness polyneuropathy, critical illness polyneuromyopathy, and prolonged neurogenic weakness. Many of these "syndromes" either overlap or represent the same disease process in different patients. Many have been incompletely diagnosed. During this review it became evident that the acute weakness syndromes currently recognized in critically ill patients could be categorized into four major groups: myopathy, neuromuscular junction abnormalities, neuropathy and polyneuromyopathy. Each had different possible aetiologies. "Myopathy" includes acute necrotizing myopathy and disuse atrophy. Neuromuscular junction abnormalities are subdivided into myasthenia-like syndromes and prolonged neuromuscular blockade. Neuropathies are divided into critical illness polyneuropathy and acute motor neuropathy. The anterior horn cell injury in Hopkins syndrome should also be considered in this group. Polyneuromyopathies include various combinations of neuropathy and myopathy in the same patients.

Toxic myopathies

Toxic myopathies may occur with a variety of prescribed medications, illicit drug abuse, or other toxins. The article discusses an overview of some of the compounds that may cause myopathy, the clinical and laboratory features, histology, mechanisms of action, and potential risk factors of myopathy. The ability to recognize these syndromes is essential to avoid unnecessary tests and to avoid delay in treatment, especially in critically ill patients or patients with other neuromuscular diseases.

Direct muscle stimulation in acute quadriplegic myopathy

We have previously found that muscle is electrically inexcitable in severe acute quadriplegic myopathy (AQM). In contrast, muscle retains normal electrical excitability in peripheral neuropathy. To study the relationship between muscle electrical excitability and all types of flaccid weakness occurring in the intensive care unit, we identified 14 critically ill, weak patients and measured the amplitude of compound muscle action potentials (CMAPs) obtained with direct muscle stimulation (dmCMAP) and with nerve stimulation (neCMAP). In 11 of 14 patients dmCMAP amplitudes were reduced and the ratio of the neCMAP amplitude to the dmCMAP amplitude (nerve/muscle ratio) was indicative of loss of muscle electrical excitability. In 2 other patients, the nerve/muscle ratio indicated neuropathy. Direct muscle stimulation may allow differentiation of AQM from neuropathy even in comatose or encephalopathic critically ill patients. AQM may be more common than has previously been appreciated.

Septic shock

PURPOSE

Many patients with sepsis require surgery for their management, often on an urgent or emergency basis. Anaesthetists are commonly required to manage patients with sepsis and septic shock in the operating room, past anaesthesia recovery area, and the intensive care unit. Since little has been written in the Anaesthesia literature on sepsis and septic shock, a review of this topic was considered appropriate.

SOURCE

References were obtained from computerized searches on the National Library of Medicine (English language), recent review articles and personal files. PRINCIPLES FINDINGS: Septic shock is a common cause of morbidity and mortality. Its presentation may be subtle or catastrophic. Successful management depends on an understanding of the pathophysiology of the syndrome, allowing rapid, appropriate resuscitation. This often requires aggressive correction of volume deficit, maintenance of adequate perfusion pressure with inotropic and vasopressor therapy, mechanical ventilation and correction of coagulopathy. Appropriate cultures must be taken and antibiotic therapy started, often empirically. Anaesthetic management should include careful haemodynamic monitoring. Anaesthesia induction and maintenance must be tailored to the haemodynamically unstable patient.

CONCLUSIONS

The management of the septic patient in the perioperative period presents a challenge for the anaesthetist. Haemodynamic and respiratory instability should be anticipated. Management requires multisystem intervention and careful anesthetic management.

Economic impact of prolonged motor weakness complicating neuromuscular blockade in the intensive care unit

OBJECTIVE

We compared a case-series of ten patients who developed prolonged neuromuscular weakness after continuous, nondepolarizing, neuromuscular blockade with a group of controls without neuromuscular weakness to determine the economic impact of the neuromuscular weakness.

DESIGN

Frequency-matched case control trial.

SETTING

Medical and surgical intensive care units of a 937-bed tertiary care, university-affiliated teaching hospital.

PATIENTS

Ten patients developed prolonged neuromuscular weakness after continuous administration of nondepolarizing neuromuscular blockers. Ten patients from a 1994 drug utilization database who did not develop motor weakness after paralysis were identified to serve as controls.

MEASUREMENTS AND MAIN RESULTS

The medical and accounting records of the patients were retrospectively reviewed. Charge data were obtained from patient accounts. Institutional ratios to convert charges to full costs and marginal costs were obtained from the Hospital Finance Department of Henry Ford Hospital. The economic impact of the diagnosis and recovery of the motor weakness was estimated for the intensive care unit (ICU) and hospital stays and compared with those values for control patients. Median hospital charges (excluding rehabilitation), totaling $91,476, were attributed to the patients who developed neuromuscular weakness and included charges for neuromuscular blocking agents, continuous mechanical ventilation, ICU and hospital beds, neurologic studies, and physical therapy services. In the control patients, median charges were $22,191 (p = .001). The total median cost differential for a patient in the neuromuscular weakness group was in excess of $66,713 (95% confidence interval $23,485 to $189,214, p = .001). Significant differences were also found for patient charges, full costs, and marginal costs for mechanical ventilation (p = .002), neurologic studies (p = .014), as well as ICU (p = .002) and hospital (p = .001) stays.

CONCLUSIONS

The development of motor weakness was associated with an increase in ICU and hospital stays, continued mechanical ventilation, and disproportionate healthcare expenditures in excess of $66,000 per patient. A prospective evaluation of the true prevalence of neuromuscular weakness after neuromuscular blockade and of the costs to the healthcare system is needed.

Generalized Paralysis in the Intensive Care Unit: Emphasis on the Complications of Neuromuscular Blocking Agents and Corticosteroids

Generalized weakness in intensive care unit (ICU) patients is increasingly recognized as a frequent complication and a common cause of prolonged ventilator dependency. Intravenous corticosteroids and neuromuscular blocking agents, sepsis, and multiorgan failure have been strongly implicated in the ICU paralysis syndromes, but the pathophysiology of these disorders is poorly understood. The combination of neuromuscular blocking agents and corticosteroids may induce three distinct syndromes of generalized weakness in ICU patients: acute myopathy, prolonged neuromuscular blockade, and critical illness polyneuropathy. More than one syndrome may occur simultaneously, and the distinctions may be difficult in a particular patient, but a specific diagnosis usually can be established after careful clinical, electrodi-agnostic, and histological evaluation. Acute myopathy with generalized weakness, preserved eye movements, elevated creatine kinase levels, and myopathic motor units on electromyography (EMG) have developed in asthmatics requiring neuromuscular blockers and steroids. Muscle biopsy has shown distinctive changes, with fiber atrophy, scattered necrosis, and thick (myosin) filament depletion on ultrastructural studies. Patients who have had a prolonged ICU stay or sepsis with failure to wean from the ventilator, distal weakness, and areflexia probably have critical illness polyneuropathy. EMG in these patients has demonstrated reduced or absent motor and sensory potentials with neurogenic motor units. Prolonged neuromuscular blockade most commonly has occurred in patients with renal failure who received prolonged infusions of neuromuscular blockers. Severe flaccid, areflexic paralysis with normal sensation, facial weakness, and ophthalmoparesis persists for days or weeks after the neuromuscular blockers have been discontinued. Repetitive nerve stimulation has shown a decrement of the compound muscle action potential, and it establishes a disorder of neuromuscular transmission in most patients. We critically examine the clinical, electrophysiological, and pathological features of each of these syndromes, and we summarize current understanding of the pathophysiology of these disorders and the relationship to neuromuscular blocking agents and corticosteroids.