Context The combination of multiple clinical factors culminates in neuromuscular respiratory failure in up to 30% of the patients with Guillain-Barré syndrome [GBS]. Although guidelines exist as to when to proceed with intubation, early indicators of subsequent progression to respiratory failure have not been established.
Objectives To identify clinical and respiratory features associated with progression to respiratory failure and to examine patterns of respiratory decline in patients with severe GBS.
Design Retrospective survey.
Setting Tertiary care hospital.
Patients One hundred fourteen consecutive patients with severe GBS admitted to the intensive care unit between January 1, 1976, and December 31, 1996.
Main Outcome Measures Early markers of impending respiratory failure, requirement for mechanical ventilation, and patterns of respiratory decline.
Methods The clinical and electrophysiologic features of 60 patients receiving mechanical ventilation were compared with 54 patients with severe GBS who did not receive mechanical ventilation. Daily preventilation maximal inspiratory and maximal expiratory respiratory pressures and vital capacity were analyzed. Multivariate predictors of the necessity for mechanical ventilation were assessed using logistic regression analysis.
Results Progression to mechanical ventilation was highly likely to occur in those patients with rapid disease progression, bulbar dysfunction, bilateral facial weakness, or dysautonomia. Factors associated with progression to respiratory failure included vital capacity of less than 20 mL/kg, maximal inspiratory pressure less than 30 cm H2O, maximal expiratory pressure less than 40 cm H2O or a reduction of more than 30% in vital capacity, maximal inspiratory pressure, or maximal expiratory pressure. No clinical features predicted the pattern of respiratory decline; however, serial measurements of pulmonary function tests allowed detection of those at risk for respiratory failure.
Conclusions While inherently unpredictable, the course of patients with severe GBS can, to some extent, be predicted on the basis of clinical information and simple bedside tests of respiratory function. These data may be used in the decisions regarding admission to the intensive care unit and preparation for elective intubation.
THE MANAGEMENT of patients with Guillain-Barré syndrome [GBS] can be intimidating. The unpredictable course and potential for rapidly producing life-threatening respiratory failure may prompt admission to an intensive care unit [ICU]. However, it is clearly unnecessary to transfer every patient with GBS to the ICU based on the potential for deterioration alone. At present, only limited data are available to provide guidance in this situation. Although many studies have identified factors that are associated with the need for ventilation [severe generalized weakness, bulbar involvement, or rapid disease progression], these factors were variably analyzed prior to intubation.1-5 It is, therefore, difficult to know how to use this information in the assessment of a patient before the point of respiratory failure as many of the clinical findings identified may have occurred after intubation.
In their observational series of 19 patients, Ropper and Kehne6 established strict criteria for intubation in GBS based on previously defined clinical and respiratory factors.7 Patients were intubated when clinical evidence of fatigue or severe oropharyngeal weakness resulting in aspiration occurred. They also intubated when vital capacity [VC] measurements fell below 15 mL/kg or if PO2 values were less than 70 mm Hg on room air.6 Many textbooks have since reiterated the guidelines for intubation adhered to in this article.8-10 These clinical and respiratory factors are accurate in determining when to proceed with intubation but do not provide guidance for the early respiratory management of patients with GBS.
Serial measurements of respiratory function are frequently advocated in patients with GBS.8-10 However, there is little detailed clinical information in the literature on the patterns of decline of neuromuscular respiratory function and the respiratory values at which preemptive measures are warranted.11 Respiratory management would be simplified and guidelines for the use of elective intubation and admission to the ICU could be developed if accurate predictors of respiratory failure could be identified early in the course of the disease.
Patients, materials, and methods
The medical records of 114 patients with GBS admitted to the ICU between January 1, 1976, and December 31,1996, were reviewed. Standard diagnostic criteria for GBS were used.9,12 All patients were examined by a neurologist. The clinical, biochemical, and electrophysiologic features of 60 of these patients with GBS who received mechanical ventilation were compared with a group of 54 patients with GBS who were admitted to the ICU but who did not receive mechanical ventilation. These patients were admitted for many reasons including autonomic dysfunction, bulbar weakness, comorbid disease, systemic complications, and importantly, concerns regarding progression of disease and development of respiratory dysfunction.
All data were collected before ventilation or to peak disability in patients who had received mechanical ventilation and those who did not, respectively. Demographic features analyzed were age, sex, time to peak disability, presence of pulmonary comorbidity [chronic obstructive airways disease, asthma, or pulmonary fibrosis], and antecedent event, in particular, preceding gastrointestinal illness [diarrhea or abdominal pain]. Time to peak disability was defined as time to intubation [patients who underwent ventilation], or time to worst score on the Hughes disability scale [patients who did not undergo ventilation], from onset of neuropathic symptoms.8 The use of specific treatment with intravenous immunoglobulin or plasma exchange was also analyzed. Clinical features analyzed were presence of bilateral facial weakness, upper limb paralysis [complete absence of movement in the upper limbs], autonomic dysfunction [unexplained blood pressure or heart rate fluctuations or significant bladder or bowel dysfunction], and bulbar weakness [dysarthria, dysphagia or impairment of the gag reflex]. The results of cerebrospinal fluid examination [protein level and cell count] and chest radiographs performed prior to peak disability were analyzed. The compound muscle action potential [CMAP] was analyzed on the first nerve conduction study performed at the Mayo Clinic, Rochester, Minn. Low CMAP amplitude was defined as less than 20% of the lower limit of normal.13 Inexcitable nerves were defined as CMAP amplitude absent in all nerves tested or present in only 1 nerve with a CMAP amplitude less than 10% of the lower limit of normal and absent in all other nerves tested.14
Serial respiratory function tests including VC [measured in milliliters per kilograms], maximal inspiratory pressure [PImax], maximal expiratory pressure [PEmax] [measured in centimeters of water], and arterial blood gases were analyzed daily. For PImax, negative values are usually measured, but in this article, these values are expressed, for simplicity, as positive [eg, PImax of –50 cm H20 is recorded as 50 cm H20]. Respiratory factors were measured by a respiratory therapist using standard techniques. For those with facial weakness, the lips would be held sealed by the respiratory technician or an anesthesia mask would be used. When multiple respiratory measurements were recorded, the best score was analyzed. We also reviewed the patterns of respiratory decline in each patient. The time of day at which intubation occurred was analyzed and, for each patient, it was determined whether this was an elective or urgent procedure.
Characteristics between patients with GBS who received mechanical ventilation and those who did not were assessed for comparability using the Wilcoxon rank sum test for continuous variables and the Fisher exact test for categorical variables. Multivariate predictors of ventilation were assessed using logistic regression analysis with a backward elimination procedure of nonsignificant variables. In this model, mechanical ventilation [yes vs no] was the dependent variable and all variables with a univariate P