Endotracheal intubation and mechanical ventilation in severe asthma

Management of the Difficult Airway

ABSTRACT

Airway management is a fundamental component of care during resuscitation of critically ill and injured children. In addition to predicted anatomic and physiologic differences in children compared with adults, certain conditions can predict potential difficulty during pediatric airway management. This review presents approaches to identifying pediatric patients in whom airway management is more likely to be difficult, and discusses strategies to address such challenges. These strategies include optimization of effective bag-mask ventilation, alternative approaches to laryngoscopy, use of adjunct airway devices, modifications to rapid sequence intubation, and performance of surgical airways in children. The importance of considering systems of care in preparing for potentially difficult pediatric airways is also discussed.

The use of non- invasive ventilation in asthma exacerbation - a two year retrospective analysis of outcomes

Background: The use of Non-Invasive Ventilation (NIV) in acute asthma exacerbation remains controversial. Comparative data on patient characteristics that benefit from NIV in asthma exacerbation to those patients that fail NIV remains limited. Our study compares some of these patient characteristics and examines if NIV is safe and effective in carefully selected patients.

Methods: Following institutional review board approval, we extracted from the electronic medical record and conducted a retrospective chart-based review of those patients who received NIV in the emergency room for a diagnosis of asthma exacerbation from January 2017 to December 2018.

Results and Conclusion: The rate of failure of NIV overall was low, at 9.17%, with younger patients more likely to fail NIV (P = 0.03) and need invasive mechanical ventilation. Surprisingly, baseline asthma severity did not impact NIV failure rate, and neither did body mass index, smoking history, and a host of clinical characteristics. Understandably, the length of stay was significantly longer in the group of patients that failed NIV. There were no adverse events, such as an increased rate of barotrauma events in either group. In conclusion, this study contributes to the growing body of evidence that NIV is a safe and effective adjunct to routine care in the management of patients with asthma exacerbation.

Trends in the Use of Noninvasive and Invasive Ventilation for Severe Asthma

OBJECTIVES

To explore and define contemporary trends in the use of invasive mechanical ventilation (IMV) and noninvasive ventilation (NIV) in the treatment of children with asthma.

METHODS

We performed a serial cross-sectional analysis using data from the Pediatric Health Information System. We examined 2014-2018 admission abstracts from patients aged 2 to 17 years who were admitted to member hospitals with a primary diagnosis of asthma. We report temporal trends in IMV use, NIV use, ICU admission, length of stay, and mortality.

RESULTS

Over the study period, 48 hospitals reported 95 204 admissions with a primary diagnosis of asthma. Overall, IMV use remained stable at 0.6% between 2014 and 2018 (interquartile range [IQR]: 0.3%-1.1% and 0.2%-1.3%, respectively), whereas NIV use increased from 1.5% (IQR: 0.3%-3.2%) to 2.1% (IQR: 0.3%-5.6%). There was considerable practice variation among centers, with NIV rates more than doubling within the highest quartile of users (from 4.8% [IQR: 2.8%-7.5%] to 13.2% [IQR: 7.4%-15.2%]; P < .02). ICU admission was more common among centers with high NIV use, but centers with high NIV use did not differ from lower-use centers in mortality, IMV use, or overall average length of stay.

CONCLUSIONS

The use of IMV is at historic lows, and NIV has replaced it as the primary mechanical support mode for asthma. However, there is considerable variability in NIV use. Increased NIV use was not associated with a change in IMV rates, which remained stable. Higher NIV use was associated with increased ICU admissions. NIV's precise contribution to the cost and quality of care remains to be determined.

Bilevel Positive Airway Pressure ventilation efficiently improves respiratory distress in initial hours treating children with severe asthma exacerbation

OBJECTIVE

Treatment of severe asthma exacerbation could be challenging, especially in the initial hours of acute attack when systemic corticosteroid is yet to take effect. In spite of using inhaled agents, the role of non-invasive ventilation (NIV), including Bilevel Positive Airway Pressure (BiPAP), had been addressed recently.

METHODS

We reviewed 5-year experience in our hospital for records of patients who were admitted to pediatric intensive care unit because of severe asthma attack. The included admission records from 2012 to 2017 were grouped according to BiPAP use (Yes/No). Clinical parameters (heart rate (HR), respiratory rate (RR), SpO2 and serum pCO2) at selected time intervals of treatment were collected for both groups and analyzed.

RESULTS

We included data of 46 admissions from 33 different patients (24 with BiPAP and 21 without BiPAP.) The BiPAP group had significantly higher initial RR as well as higher severity scores compared with the other group (p < 0.001). The RR improved significantly in the following time intervals in BiPAP group. There was no significant difference in HR between groups in any of the time intervals. The serum pCO2 levels decreased significantly after initiation of ventilation support in the BiPAP group, and SpO2 levels improved significantly for both groups.

CONCLUSION

BiPAP seemed efficient in improving respiratory rate and oxygenation in our study. It does not seem to cause additional irritation regarding that HR was not increased in BiPAP group compared with non-BiPAP group. Overall, BiPAP ventilation is safe and efficient in treating children with severe asthma attack.

Use of noninvasive ventilation in adult patients with acute asthma exacerbation

Noninvasive ventilation (NIV) has been found to be beneficial for respiratory failure in many disease states; however, limited data are available supporting its use in acute asthma exacerbation. A retrospective chart analysis of adult patients admitted for acute asthma exacerbation and treated with NIV between January 2007 and December 2009 at a tertiary care community hospital was done. Ninety-eight patient encounters were identified. Mean age of the patients was 48.3 years, and 46% were male. Nineteen patients failed NIV and required invasive ventilation. There was no significant difference in the mean age, sex, race, and initial blood gas between patients with successful versus failed NIV. Usage of drugs, smoking, and history of past hospital or intensive care unit admission or intubation did not significantly influence the rate of failure of NIV. Patients who needed higher initial FiO2 were more likely to get intubated during their hospital stay (46.2 vs. 20.4%, P = 0.019). Patients who failed NIV were found to have longer duration of hospital stay (6.8 vs. 3.9 days, P= 0.016) and longer intensive care unit stay (4 vs. 0.9 days, P = 0.002). Use of inhalers and other medications was not found to significantly influence the rate of failure of NIV. NIV can be used initially in patients with acute asthma exacerbation, as it is associated with shorter duration of hospital stay and can prevent the morbidity of mechanical intubation. Patients with initial requirement of higher FiO2 were more likely to fail NIV and should be carefully monitored.

Indications for endotracheal intubation and ventilation

The ability of the emergency physician to recognize and manage a patient with a compromised airway is probably the most important aspect of an individual’s care in the emergency department. Endotracheal intubation in a critically ill patient is a potentially hazardous procedure because of the technical difficulties that can be encountered during emergency airway management and the profound pathophy siological changes that the institution of mechanical ventilation can cause. This review article sets out to illustrate when invasive airway management should be considered and the potential consequences of attempts to perform endotracheal intubation and mechanical ventilation.

Extracorporeal carbon dioxide removal (ECCO2R) in respiratory deficiency and current investigations on its improvement: a review

The implementation of extracorporeal carbon dioxide removal (ECCO₂R) as one of the extracorporeal life support system is getting more attention today. Thus, the objectives of this paper are to study the clinical practice of commercial ECCO₂R system, current trend of its development and also the perspective on future improvement that can be done to the existing ECCO₂R system. The strength of this article lies in its review scope, which focuses on the commercial ECCO₂R therapy in the market based on membrane lung and current investigation to improve the efficiency of the ECCO₂R system, in terms of surface modification by carbonic anhydrase (CA) immobilization technique and respiratory electrodialysis (R-ED). Our methodology approach involves the identification of relevant published literature from PubMed and Web of Sciences search engine using the terms Extracorporeal Carbon Dioxide Removal (ECCO₂R), Extracorporeal life support, by combining terms between ECCO₂R and CA and also ECCO₂R with R-ED. This identification only limits articles in English language. Overall, several commercial ECCO₂R systems are known and proven safe to be used in patients in terms of efficiency, safety and risk of complication. In addition, CA-modified hollow fiber for membrane lung and R-ED are proven to have good potential to be applied in conventional ECCO₂R design. The detailed technique and current progress on CA immobilization and R-ED development were also reviewed in this article.

Pediatric acute asthma exacerbations: Evaluation and management from emergency department to intensive care unit

OBJECTIVE

The goal of this report is to review available modalities for assessing and managing acute asthma exacerbations in pediatric patients, including some that are not included in current expert panel guidelines. While it is not our purpose to provide a comprehensive review of the National Asthma Education and Prevention Program (NAEPP) guidelines, we review NAEPP-recommended treatments to provide the full range of treatments available for managing exacerbations with an emphasis on the continuum of care between the ER and ICU.

DATA SOURCES

We searched PubMed using the following search terms in different combinations: asthma, children, pediatric, exacerbation, epidemiology, pathophysiology, guidelines, treatment, management, oxygen, albuterol, β2-agonist, anticholinergic, theophylline, corticosteroid, magnesium, heliox, BiPAP, ventilation, mechanical ventilation, non-invasive mechanical ventilation and respiratory failure. We attempted to weigh the evidence using the hierarchy in which meta-analyses of randomized controlled trials (RCTs) provide the strongest evidence, followed by individual RCTs, followed by observational studies. We also reviewed the NAEPP and Global Initiative for Asthma expert panel guidelines.

RESULTS AND CONCLUSIONS

Asthma is the most common chronic disease of childhood, and acute exacerbations are a significant burden to patients and to public health. Optimal assessment and management of exacerbations, including appropriate escalation of interventions, are essential to minimize morbidity and prevent mortality. While inhaled albuterol and systemic corticosteroids are the mainstay of exacerbation management, escalation may include interventions discussed in this review.

Asthma: Hospitalization Trends and Predictors of In-Hospital Mortality and Hospitalization Costs in the USA (2001-2010)

BACKGROUND

In the last decade, the proportion of people with asthma in the USA grew by nearly 15%, with 479,300 hospitalizations and 1.9 million emergency department visits in 2009 alone. The primary objective of our study was to evaluate in-hospital outcomes in patients admitted with asthma exacerbation in terms of mortality, length of stay (LOS) and hospitalization costs.

METHODS

We queried the HCUP's Nationwide Inpatient Sample (NIS) between 2001 and 2010 using the ICD9-CM diagnosis code 493 for asthma (n = 760,418 patients). The NIS represents 20% of all hospitals in the USA. Multivariate logistic regression analysis was used to evaluate predictors of in-hospital mortality. LOS and hospitalization costs were also analyzed.

RESULTS

The overall LOS was 3.9 days and as high as 8.3 days in patients requiring mechanical ventilation. LOS has decreased in recent years, though it continues to be higher than in 2001. The hospitalization cost increased steadily over the study period. The overall in-hospital mortality was 1% and as high as 9.8% in patients requiring mechanical ventilation. Multivariate predictors of longer LOS, higher hospitalization costs and in-hospital mortality included increasing age and hospitalizations during the winter months. Private insurance was predictive of lower hospitalization costs and LOS as well as lower in-hospital mortality.

CONCLUSION

Asthma continues to account for significant in-hospital mortality and resource utilization, especially in mechanically ventilated patients. Age, admissions during winter months and the type of insurance are independent predictors of in-hospital outcomes.

Mechanical ventilation for severe asthma

Acute exacerbations of asthma can lead to respiratory failure requiring ventilatory assistance. Noninvasive ventilation may prevent the need for endotracheal intubation in selected patients. For patients who are intubated and undergo mechanical ventilation, a strategy that prioritizes avoidance of ventilator-related complications over correction of hypercapnia was first proposed 30 years ago and has become the preferred approach. Excessive pulmonary hyperinflation is a major cause of hypotension and barotrauma. An appreciation of the key determinants of hyperinflation is essential to rational ventilator management. Standard therapy for patients with asthma undergoing mechanical ventilation consists of inhaled bronchodilators, corticosteroids, and drugs used to facilitate controlled hypoventilation. Nonconventional interventions such as heliox, general anesthesia, bronchoscopy, and extracorporeal life support have also been advocated for patients with fulminant asthma but are rarely necessary. Immediate mortality for patients who are mechanically ventilated for acute severe asthma is very low and is often associated with out-of-hospital cardiorespiratory arrest before intubation. However, patients who have been intubated for severe asthma are at increased risk for death from subsequent exacerbations and must be managed accordingly in the outpatient setting.

Emergency endotracheal intubation-related adverse events in bronchial asthma exacerbation: can anesthesiologists attenuate the risk?

PURPOSE

Airway management in severe bronchial asthma exacerbation (BAE) carries very high risk and should be performed by experienced providers. However, no objective data are available on the association between the laryngoscopist's specialty and endotracheal intubation (ETI)-related adverse events in patients with severe bronchial asthma. In this paper, we compare emergency ETI-related adverse events in patients with severe BAE between anesthesiologists and other specialists.

METHODS

This historical cohort study was conducted at a Japanese teaching hospital. We analyzed all BAE patients who underwent ETI in our emergency department from January 2002 to January 2014. Primary exposure was the specialty of the first laryngoscopist (anesthesiologist vs. other specialist). The primary outcome measure was the occurrence of an ETI-related adverse event, including severe bronchospasm after laryngoscopy, hypoxemia, regurgitation, unrecognized esophageal intubation, and ventricular tachycardia.

RESULTS

Of 39 patients, 21 (53.8 %) were intubated by an anesthesiologist and 18 (46.2 %) by other specialists. Crude analysis revealed that ETI performed by an anesthesiologist was significantly associated with attenuated risk of ETI-related adverse events [odds ratio (OR) 0.090, 95 % confidence interval (CI) 0.020-0.41, p = 0.001]. The benefit of attenuated risk remained significant after adjusting for potential confounders, including Glasgow Coma Score, age, and use of a neuromuscular blocking agent (OR 0.058, 95 % CI 0.010-0.35, p = 0.0020).

CONCLUSIONS

Anesthesiologist as first exposure was independently associated with attenuated risk of ETI-related adverse events in patients with severe BAE. The skill and knowledge of anesthesiologists should be applied to high-risk airway management whenever possible.

Outcomes of invasive mechanical ventilation in children and adolescents hospitalized due to status asthmaticus in United States: a population based study

OBJECTIVE

Current national estimates of and outcomes of Invasive Mechanical Ventilation (MV) in status asthmaticus (SA) are unclear. The objective of this study is to estimate the incidence and outcomes of MV in hospitalized SA children and adolescents.

METHODS

We used the Nationwide Inpatient Sample (NIS, 2009-2010), the largest all-payer hospital discharge database in United States. All hospitalizations (age ≤21 years) with a primary diagnosis of SA were selected. MV was identified using ICD-9-CM procedure codes. Multivariable regression analyses were used to examine the association between MV and outcomes (Length of Stay (LOS) and Hospital Charges (HC)).

RESULTS

Over the study period, of the 250 718 SA hospitalizations, MV was needed for <96 h in 0.37% hospitalizations and 0.18% had MV for ≥96 h. Complications occurred in 12.4% (30 991) of all hospitalizations with pneumonia (10.8%) being the most common. A total of 65 patients died in hospitals (the overall in-hospital mortality [IHM] rate was 0.03%). About 55 of these deaths occurred among those who had MV (4% IHM rate for those receiving MV). The mean LOS and hospital HC included without MV (2.1 d, $11 921) MV < 96 h (4.8 d, $52 201); MV > 96 h (15.6 d, $200 336). After adjustment for patient/hospital level factors, the need for MV was associated with significantly higher LOS and HC (p < 0.0001). Those who had MV<96 h (OR = 2.58, 95% CI = 1.77-3.77) or MV ≥ 96 h (OR = 6.23, 95% CI = 3.87-10.03) had higher risk of developing pneumonia.

CONCLUSIONS

Although MV is infrequently needed in children and adolescents hospitalized for SA (0.55% incidence rate), it is associated with higher IHM rate and significant hospital resource utilization.

Noninvasive ventilation in acute asthma

Noninvasive ventilation (NIV) has well-recognized benefits in acute exacerbation of chronic obstructive pulmonary disease and pulmonary edema. Its utilization in acute asthma, however, remains controversial. In this review, we describe the physiological basis to justify NIV use in acute asthma and contribute a critical appraisal of the available literature relating to this practice. A discussion of some of the more pertinent, clinically relevant practicalities is also provided. Original research articles were identified using the electronic PubMed database. Randomized controlled trials of NIV in the setting of acute asthma were selected. Retrospective observational studies were also included if they were considered to contribute to the literature review. The use of NIV in the acute asthma setting has been shown to be associated with improvements in important physiological variables including measures of airflow and respiratory rate, and lends support to further study in this field. Improvements in airflow may be a direct effect of applied positive airway pressure or an indirect effect secondary to better dispersal of aerosolized medication. Reductions observed in respiratory rate and dyspnea are likely influenced by the amount of pressure support provided. Evidence suggestive of any improvement in mortality, intubation rate, or hospital/intensive care unit length of stay, however, is lacking. Studies to date have been hampered by small numbers and a lack of demonstrable meaningful clinical outcomes. Data relating to mortality, endotracheal intubation rates, and hospital length of stay/admission should be sought in future large clinical trials.

Patient origin is associated with duration of endotracheal intubation and PICU length of stay for children with status asthmaticus

OBJECTIVE

To describe intubation practices and duration of mechanical ventilation in children with status asthmaticus admitted from emergency departments (ERs) to pediatric intensive care units (PICUs).

DESIGN

Retrospective cohort study using the Virtual PICU Performance System database (VPS, LLC) of children with status asthmaticus admitted to a participating PICU between December 2003 and September 2006. The primary outcome measure was intubation prior to intensive care unit (ICU) admission. Secondary outcomes included length of intubation and medical length of stay.

SETTING

Thirty-five PICUs in the United States.

PATIENTS

Children who were intubated and mechanically ventilated during their ICU stay for asthma and were admitted from an ER.

RESULTS

A total of 4051 patients with status asthmaticus were identified. Intubation data were available from 35 of the 53 centers. Of all, 187 children were intubated for asthma, of which 157 were admitted from an ER and had complete data. Of all, 85 patients were from community hospital ERs and 72 were from the institution's own ER. In all, 115 (73%) patients were intubated prior to ICU admission and 42 (27%) patients were intubated after PICU admission. Of patients who received mechanical ventilation for status asthmaticus and were intubated prior to PICU admission, a greater proportion were intubated at community hospital ERs than in the institutions' own ERs. Eighty-five percent of the patients from community hospital ERs were intubated prior to PICU admission as opposed to 60% from institution's own ERs (P = .0004). However, median duration of intubation and PICU stay from community hospital ERs was significantly shorter than from the hospitals' own ERs (25 vs 42 hours P = .011; 57 vs 98 hours P = .0013, respectively). Logistic regression analysis revealed that after controlling for the effects of age, race, gender, and a revised version of the Paediatric Index of Mortality score of patients who were admitted for status asthmaticus and required mechanical ventilations, patients treated in community hospital ERs represented a greater proportion of preadmission intubation. The odds ratio for preadmission intubation was 5.1 if the patients arrived from community hospital ERs (95% confidence interval 1.91-13.6).

CONCLUSION

PATIENTS with status asthmaticus are more likely to be intubated when they are admitted from community hospital emergency rooms, although the duration of intubation and PICU stay is shorter.

The critically ill asthmatic--from ICU to discharge

Status asthmaticus (SA) is defined as an acute, severe asthma exacerbation that does not respond readily to initial intensive therapy, while near-fatal asthma (NFA) refers loosely to a status asthmaticus attack that progresses to respiratory failure. The in-hospital mortality rate for all asthmatics is between 1% to 5%, but for critically ill asthmatics that require intubation the mortality rate is between 10% to 25% primarily from anoxia and cardiopulmonary arrest. Timely evaluation and treatment in the clinic, emergency room, or ultimately the intensive care unit (ICU) can prevent the morbidity and mortality associated with respiratory failure. Fatal asthma occurs from cardiopulmonary arrest, cerebral anoxia, or a complication of treatments, e.g., barotraumas, and ventilator-associated pneumonia. Mortality is highest in African-Americans, Puerto Rican-Americans, Cuban-Americans, women, and persons aged ≥ 65 years. Critical care physicians or intensivists must be skilled in managing the critically ill asthmatics with respiratory failure and knowledgeable about the few but potentially serious complications associated with mechanical ventilation. Bronchodilator and anti-inflammatory medications remain the standard therapies for managing SA and NFA patients in the ICU. NFA patients on mechanical ventilation require modes that allow for prolonged expiratory time and reverse the dynamic hyperinflation associated with the attack. Several adjuncts to mechanical ventilation, including heliox, general anesthesia, and extra-corporeal carbon dioxide removal, can be used as life-saving measures in extreme cases. Coordination of discharge and follow-up care can safely reduce the length of hospital stay and prevent future attacks of status asthmaticus.

Isoflurane for life-threatening bronchospasm: a 15-year single-center experience

BACKGROUND

Children with severe bronchospasm requiring mechanical ventilation may become refractory to conventional therapy. In these critically ill patients, isoflurane is an inhaled anesthetic agent available in some centers to treat bronchospasm. We hypothesized that isoflurane is safe and would lead to improved gas exchange in children with life-threatening bronchospasm refractory to conventional therapy.

METHODS

A retrospective review was conducted and included mechanically ventilated children treated with isoflurane in a quaternary pediatric ICU for life-threatening bronchospasm, from 1993 to 2007. Demographic, blood gas, ventilator, and outcome data were collected.

RESULTS

Thirty-one patients, with a mean age of 9.5 years (range 0.4-23 years) were treated with isoflurane, from 1993 to 2007. Mean time to initiation of isoflurane after intubation was 13 hours (0-120 h), and the mean maximum isoflurane dose was 1.1% (0.3-2.5%). Mean duration of isoflurane administration was 54.5 hours (range 1-181 h), with a total mean duration of mechanical ventilation of 252 hours (range 16-1,444 h). Isoflurane led to significant improvement in pH and P(CO(2)) within 4 hours of initiation (P ≤ .001). Complications during isoflurane administration included hypotension requiring vasoactive infusions in 24 (77%), arrhythmia in 3 (10%), neurologic side effects in 3 (10%), and pneumothorax in 1 (3%) patient.

CONCLUSIONS

Isoflurane led to improvement in pH and P(CO(2)) within 4 hours in this series of mechanically ventilated patients with life-threatening bronchospasm. The majority of patients in this series developed hypotension, but there was a low incidence of other side effects related to isoflurane administration. Isoflurane appears to be an effective therapy in patients with life-threatening bronchospasm refractory to conventional therapy. However, further investigation is warranted, given the uncertain overall impact of isoflurane in this context.

Severe Asthma

Despite vast improvements in the care of children with asthma over the past decades, asthma remains a common cause of admission to pediatric intensive care units. During the 1990s asthma prevalence and hospital admissions increased in the United States and worldwide. The increase occurred in both males and females and across all ethnic groups. However, the largest increases occurred in children of low socioeconomic status living in urban settings. Recent asthma statistics should be interpreted with consideration of changes made in the method for reporting asthma prevalence (Fig. 23-1). From 1980 to 1996, the National Health Interview Survey (NHIS) conducted by the CDC measured pediatric asthma prevalence as the percentage of children with asthma in the past 12 months. Since 1997, asthma prevalence estimates have been defined as: having received an asthma diagnosis, currently having the disease at the time of the interview, and experiencing an attack in the past year. The more specific definition may have led to a reduction in the number of children reported to have asthma.

Status asthmaticus in the medical intensive care unit: a 30-year experience

OBJECTIVES

To investigate the characteristics, trends in management (permissive hypercapnia; mechanical ventilation (MV); neuromuscular blockade) and their impact on complications and outcomes in Status Asthmaticus (SA).

METHODS

We performed a retrospective observational study of subjects admitted with SA to a single multidisciplinary MICU over a 30-year period. All laboratory, radiologic, respiratory care, physician notes and orders were extracted from an electronic medical record (EMR) maintained during the entire duration of the study.

RESULTS

Two hundred and twenty-seven subjects were admitted with 280 episodes of SA. While subjects reflected our regional population (52% Hispanic), African Americans were over-represented (22%) and Caucasians under-represented (21%). Thirty-eight percent reported childhood asthma, 27% were steroid dependent (10% in the last 10 years), and 18% had a recent steroid taper. One hundred and thirty-nine (61.2%) required intubation. The duration of hospitalization was similar between mechanically ventilated and non-ventilated subjects (5.8±4.41 vs. 6.8±7.22 days; p=0.07). The overall complication rate remained low irrespective of the use of permissive hypercapnia or mode of mechanical ventilation (overall mortality 0.4%; pneumothorax 2.5%; pneumonia 2.9%). The frequency of SA declined significantly in the last 10 years of the study (12.4 vs. 3.2 cases/year).

CONCLUSIONS

Despite the frequent use of mechanical ventilation, mortality/complication rates remained extremely low. MV did not significantly increase the duration of hospitalization. At our institution, the frequency of SA significantly decreased despite an increase in emergency room visits for asthma.

Safety and clinical findings of BiPAP utilization in children 20 kg or less for asthma exacerbations

PURPOSE

To investigate safety and clinical findings of bilevel positive airway pressure (BiPAP) utilization in children 20 kg or less for asthma exacerbations.

METHODS

Retrospective and prospective descriptive analysis of 165 enrolled subjects with moderate and severe asthma exacerbations who weighed 20 kg or less and who received BiPAP treatment at a large, urban children's hospital pediatric emergency department (PED).

RESULTS

Age was 0.6-8.27 years (mean 3.7 years, SD 1.6 years). None exhibited worsening hypoxia, pneumothorax, or death. Four progressed to intubation after significant period on BiPAP. Overall, BiPAP subjects showed improvement in pediatric asthma score (PAS). BiPAP initiation PAS range was 8-15 (mean 12.1, SD 1.6); BiPAP termination or 4 h PAS mean was 6.3 (SD 2.2); delta PAS showed improvement mean 5.8 (SD 2.4). Seventy-one had trial off BiPAP in PED for clinical improvement; seven were restarted. PED BiPAP duration range was 30-720 min (mean 210 min, SD 158 min); total hospitalization BiPAP duration was 1-90 h. Ninety-nine (60%) subjects were admitted to the PICU and continued BiPAP for 0-47 h (mean 6.6 h, SD 8.6 h). Fifty-seven (35%) required ward admission; none were transferred to PICU. Nine (5%) were discharged home from the PED; none returned within 72 h.

CONCLUSIONS

BiPAP utilization in acute pediatric asthma exacerbations for patients 20 kg or less is safe and may improve clinical outcomes. These findings warrant future prospective investigation of BiPAP efficacy in pediatric asthma patients.

Acute severe asthma: new approaches to assessment and treatment

The precise definition of a severe asthmatic exacerbation is an issue that presents difficulties. The term 'status asthmaticus' relates severity to outcome and has been used to define a severe asthmatic exacerbation that does not respond to and/or perilously delays the repetitive or continuous administration of short-acting inhaled beta(2)-adrenergic receptor agonists (SABA) in the emergency setting. However, a number of limitations exist concerning the quantification of unresponsiveness. Therefore, the term 'acute severe asthma' is widely used, relating severity mostly to a combination of the presenting signs and symptoms and the severity of the cardiorespiratory abnormalities observed, although it is well known that presentation does not foretell outcome. In an acute severe asthma episode, close observation plus aggressive administration of bronchodilators (SABAs plus ipratropium bromide via a nebulizer driven by oxygen) and oral or intravenous corticosteroids are necessary to arrest the progression to severe hypercapnic respiratory failure leading to a decrease in consciousness that requires intensive care unit (ICU) admission and, eventually, ventilatory support. Adjunctive therapies (intravenous magnesium sulfate and/or others) should be considered in order to avoid intubation. Management after admission to the hospital ward because of an incomplete response is similar. The decision to intubate is essentially based on clinical judgement. Although cardiac or respiratory arrest represents an absolute indication for intubation, the usual picture is that of a conscious patient struggling to breathe. Factors associated with the increased likelihood of intubation include exhaustion and fatigue despite maximal therapy, deteriorating mental status, refractory hypoxaemia, increasing hypercapnia, haemodynamic instability and impending coma or apnoea. To intubate, sedation is indicated in order to improve comfort, safety and patient-ventilator synchrony, while at the same time decrease oxygen consumption and carbon dioxide production. Benzodiazepines can be safely used for sedation of the asthmatic patient, but time to awakening after discontinuation is prolonged and difficult to predict. The most common alternative is propofol, which is attractive in patients with sudden-onset (near-fatal) asthma who may be eligible for extubation within a few hours, because it can be titrated rapidly to a deep sedation level and has rapid reversal after discontinuation; in addition, it possesses bronchodilatory properties. The addition of an opioid (fentanyl or remifentanil) administered by continuous infusion to benzodiazepines or propofol is often desirable in order to provide amnesia, sedation, analgesia and respiratory drive suppression. Acute severe asthma is characterized by severe pulmonary hyperinflation due to marked limitation of the expiratory flow. Therefore, the main objective of the initial ventilator management is 2-fold: to ensure adequate gas exchange and to prevent further hyperinflation and ventilator-associated lung injury. This may require hypoventilation of the patient and higher arterial carbon dioxide (PaCO(2)) levels and a more acidic pH. This does not apply to asthmatic patients intubated for cardiac or respiratory arrest. In this setting the post-anoxic brain oedema might demand more careful management of PaCO(2) levels to prevent further elevation of intracranial pressure and subsequent complications. Monitoring lung mechanics is of paramount importance for the safe ventilation of patients with status asthmaticus. The first line of specific pharmacological therapy in ventilated asthmatic patients remains bronchodilation with a SABA, typically salbutamol (albuterol). Administration techniques include nebulizers or metered-dose inhalers with spacers. Systemic corticosteroids are critical components of therapy and should be administered to all ventilated patients, although the dose of systemic corticosteroids in mechanically ventilated asthmatic patients remains controversial. Anticholinergics, inhaled corticosteroids, leukotriene receptor antagonists and methylxanthines offer little benefit, and clinical data favouring their use are lacking. In conclusion, expertise, perseverance, judicious decisions and practice of evidence-based medicine are of paramount importance for successful outcomes for patients with acute severe asthma.

The study of severe asthma in Latin America and Spain (1994-2004): characteristics of patients hospitalized with acute severe asthma

OBJECTIVE

Studies assessing the characteristics and management of patients hospitalized with asthma have been limited to a small number of facilities and have evaluated short time periods. The present study evaluated long-term changes among hospitalized asthma patients at a large number of facilities.

METHODS

This was a retrospective, hospital-based observational case series, designated the Study of Severe Asthma in Latin America and Spain, which was conducted in Spain and in eight Latin-American countries. We reviewed the hospital records of 3,038 patients (age range, 15-69 years) hospitalized with acute severe asthma at one of nineteen tertiary-care hospitals in 1994, 1999 and 2004.

RESULTS

Over time, the use of inhaled corticosteroids and long-acting beta2 agonists increased significantly, whereas the use of theophylline as a controller medication decreased. The utilization of pulmonary function tests also increased. There was a significant reduction in the mean hospital stay (8.5 days, 7.4 days and 7.1 days in 1994, 1999 and 2004, respectively, p = 0.0001) and a significant increase in the mean of the lowest arterial pH at hospital admission. In contrast, there was a significant decrease in the proportion of cases in which PEF was determined in the emergency room (48.6% in 1994 vs. 43.5% in 2004, p = 0.0001). We found the quality of asthma management and care to be generally better in Spain than in Latin America.

CONCLUSIONS

Although there have been certain improvements in the management of asthma between severe exacerbations and during hospitalization, asthma management remains suboptimal in Spain and, especially, in Latin America.

Emergency presentation and management of acute severe asthma in children

Acute severe asthma is one of the most common medical emergency situations in childhood, and physicians caring for acutely ill children are regularly faced with this condition. In this article we present a summary of the pathophysiology as well as guidelines for the treatment of acute severe asthma in children. The cornerstones of the management of acute asthma in children are rapid administration of oxygen, inhalations with bronchodilators and systemic corticosteroids. Inhaled bronchodilators may include selective b2-agonists, adrenaline and anticholinergics. Additional treatment in selected cases may involve intravenous administration of theophylline, b2-agonists and magnesium sulphate. Both non-invasive and invasive ventilation may be options when medical treatment fails to prevent respiratory failure. It is important that relevant treatment algorithms exist, applicable to all levels of the treatment chain and reflecting local considerations and circumstances.

Outcomes using extracorporeal life support for adult respiratory failure due to status asthmaticus

Our objective was to describe the outcomes for extracorporeal life support (ECLS) use in adult respiratory failure because of status asthmaticus and to determine whether ECLS use in status asthmaticus is associated with greater survival than other indications for ECLS. This retrospective cohort study used the multicenter, International ECLS Organization Registry. The study population included 1,257 adults with respiratory failure requiring ECLS. Status asthmaticus was the primary indication for ECLS in 24 patients. A total of 83.3% of asthmatics survived to hospital discharge compared with 50.8% of nonasthmatics (n=1,233) [odds ratio (OR) favoring survival for asthmatics=4.86, 95% confidence interval (CI) 1.65-14.31, p=0.004]. The survival advantage for asthmatics remained significant after adjustment for potential confounders. Complications were noted in 19 of 24 asthmatics (79.2%). In conclusion, we found that status asthmaticus, as an indication for ECLS in adult respiratory failure, seemed to be associated with greater survival than other indications for ECLS. However, complications are common and whether ECLS confers a survival advantage compared with other salvage treatment options remains unknown. More detailed information and complete reporting of ECLS use for status asthmaticus are needed to determine whether and when the potentially life-saving intervention of ECLS should be initiated in the asthmatic failing conventional therapy.

Mechanical ventilation for asthma: a 10-year experience

BACKGROUND

Asthmatics requiring admission to the intensive care unit and/or mechanical ventilation have increased morbidity and mortality. The purpose of this study is to examine morbidity and mortality in patients requiring intubation and mechanical ventilation for asthma over a 10-year period. This study also reviews the clinical features and management of these patients.

METHODS

We performed a retrospective review of medical records over a 10-year period of adult patients who required mechanical ventilation for a primary diagnosis of asthma. The study was conducted at a university-affiliated, county hospital.

RESULTS

One hundred twenty-seven patients with 162 episodes of asthma requiring mechanical ventilation were identified. The majority of the patients (64%) were women. The predominant ethnicity was African-American (65%). These patients had multiple risk factors for asthma mortality, including recent hospital admissions, prior episodes of near-fatal asthma, medication non-compliance, and poor outpatient follow-up. Over the 10 years of the study, outpatient management of these patients changed, with the percentage of admissions in which patients had been given inhaled corticosteroids increasing from 18 percent in 1990 to 80 percent in 1998. Management of mechanical ventilation also changed. The average tidal volume settings significantly decreased after 1995. The most common complication was atelectasis, which was seen in 33 cases. Evidence of barotrauma, including pneumothorax, pneumomediastinum, and subcutaneous emphysema, was present in 10 cases. There were four deaths. All four of the patients suffered cardiopulmonary arrest in the field with subsequent anoxic brain injury and withdrawal of care.

CONCLUSIONS

Although these patients had multiple risk factors for mortality from asthma, no deaths in this study were related to complications of mechanical ventilation. This low mortality may be related to changes in management of mechanical ventilation as well as changes in chronic outpatient asthma therapy.

The increased cost of complications in children with status asthmaticus

Status asthmaticus is one of the most common causes of admission to a pediatric intensive care unit (PICU). There is little published data, however, examining the complications associated with the treatment of status asthmaticus in children in the PICU. Our hypothesis was that children experiencing a complication would have an increased duration of hospitalization for status asthmaticus. We performed a retrospective review of the complication profile and hospital course of all children admitted to a PICU with status asthmaticus over a 9 years period. Twenty-two (8%) of the 293 children admitted to the ICU with status asthmaticus experienced one or more complications during their treatment. The most common complications were aspiration pneumonia, ventilator-associated pneumonia, pneumomediastinum, pneumothorax, and rhabdomyolysis. Intubated children were significantly more likely than non-intubated children to experience a complication (RR 15.3; 95% CI 6.7-35). Fifteen (42%) of the 36 intubated children experienced a complication. Intubated children experiencing a complication had significantly longer duration of mechanical ventilation (163 +/- 169 hr vs. 66 +/- 65 hr, P = 0.03), ICU length of stay (237 +/- 180 hr vs. 124 +/- 86 hr, P = 0.02) and hospital charges (US dollars 117,184 +/- 111,191 vs. US dollars 38,788 +/- 27,784; P = 0.001) than intubated children not experiencing a complication. In this review, complications were associated with increased morbidity and duration of hospitalization in children with status asthmaticus, particularly in those intubated as part of their therapy. This suggests that intubation and mechanical ventilation itself may increase the risk of developing a complication in this population.

Acute severe asthma

Acute severe asthma remains a major economic and health burden. The natural history of acute decompensations is one of resolution and only about 0.4% of patients succumb overall. Mortality in medical intensive care units is higher but is less than 3% of hospital admissions. "Near-fatal" episodes may be more frequent, but precise figures are lacking. However, about 30% of medical intensive care unit admissions require intubation and mechanical ventilation with mortality of 8%. Morbidity and mortality increase with socioeconomic deprivation and ethnicity. Seventy to 80% of patients in emergency departments clear within 2 hours with standardized care. The relapse rate varies between 7 and 15%, depending on how aggressively the patient is treated. The airway obstruction in the 20-30% of people resistant to adrenergic agonists in the emergency department slowly reverses over 36-48 hours but requires intense treatment to do so. Current therapeutic options for this group consist of ipratropium and corticosteroids in combination with beta2 selective drugs. Even so, such regimens are not optimal and better approaches are needed. The long-term prognosis after a near-fatal episode is poor and mortality may approach 10%.

Ketamine to avoid mechanical ventilation in severe pediatric asthma

Children experiencing severe asthma exacerbations may deteriorate to respiratory failure requiring endotracheal intubation and mechanical ventilation. Mechanical ventilation is often life saving in this setting, but also exposes the asthmatic child to substantial iatrogenic risk. We present two cases of severe asthma exacerbations in prepubertal children for whom the administration of a bolus of intravenous ketamine followed by a continuous infusion of a relatively large dose of ketamine led to prompt improvement, obviating the need for mechanical ventilation. These cases suggest that for children experiencing severe asthma exacerbations, intravenous ketamine may be an effective temporizing measure to avoid exposing these children to the risks associated with mechanical ventilation.

Management of mechanical ventilation in acute severe asthma: practical aspects

BACKGROUND

Acute severe asthma induces marked alterations in respiratory mechanics, characterized by a critical limitation of expiratory flow and a heterogeneous and reversible increase in airway resistance, resulting in premature airway closure, lung, and chest wall dynamic hyperinflation and high intrinsic PEEP.

DISCUSSION

These abnormalities increase the work of breathing and can lead to respiratory muscle fatigue and life-threatening respiratory failure, in which case mechanical ventilation is life-saving. When instituting mechanical ventilation in this setting, a major concern is the risk of worsening lung hyperinflation (thereby provoking barotrauma) and inducing or aggravating hemodynamic instability. Guidelines for mechanical ventilation in acute severe asthma are not supported by strong clinical evidence. Controlled hypoventilation with permissive hypercapnia may reduce morbidity and mortality compared to conventional normocapnic ventilation. Profound pathological alterations in respiratory mechanics occur during acute severe asthma, which clinicians should keep in mind when caring for ventilated asthmatics.

CONCLUSION

We focus on the practical management of controlled hypoventilation. Particular attention must be paid to ventilator settings, monitoring of lung hyperinflation, the role of extrinsic PEEP, and administering inhaled bronchodilators. We also underline the importance of deep sedation with respiratory drive-suppressing opioids to maintain patient-ventilator synchrony while avoiding as much as can be muscle paralysis and the ensuing risk of myopathy. Finally, the role of noninvasive positive pressure ventilation for the treatment of respiratory failure during severe asthma is discussed.

[Management of severe acute asthma in adults]

Any life-threatening episode of asthma requires early pre-hospital specialized medical management by emergency medical crews. Gravity depends on both clinical criteria and a peak expiratory flow rate (PEFR) more than 30% below either the level predicted by the reference graph or the patient's reference value. Initial treatment combines continuous nebulizations containing a beta2-agonist and ipratropium bromide, with oxygen administration and intravenous corticosteroid bolus. Recommended as second-line treatment in the absence of adequate response are: intravenous magnesium sulphate and continuous-perfusion beta2-agonists (electric syringe), or, in the case of shock, epinephrine. If mechanical ventilation is required, its settings should aim for low tidal volumes, low frequency, and increased expiratory time.

[Non-invasive bi-level ventilation in paediatric status asthmaticus]

Invasive ventilation in status asthmaticus is associated with an increased mortality and morbidity. To avoid intubation associated complications, non-invasive bi-level ventilation is often used in adults and children. We report the clinical history of an 11-month old infant, which encountered intubation criteria but was treated successfully by full-face mask non-invasive bi-level ventilation. Despite difficulties in application due to young age and lack of age related material, non-invasive bi-level ventilation is a good tool in the treatment of children with status asthmaticus.

Pressure-controlled ventilation in children with severe status asthmaticus

OBJECTIVE

The optimum strategy for mechanical ventilation in a child with status asthmaticus is not established. Volume-controlled ventilation continues to be the traditional approach in such children. Pressure-controlled ventilation may be theoretically more advantageous in allowing for more uniform ventilation. We describe our experience with pressure-controlled ventilation in children with severe respiratory failure from status asthmaticus.

DESIGN

Retrospective review.

SETTING

Pediatric intensive care unit in a university-affiliated children's hospital.

PATIENTS

All patients who received mechanical ventilation for status asthmaticus.

INTERVENTIONS

Pressure-controlled ventilation was used as the initial ventilatory strategy. The optimum pressure control, rate, and inspiratory and expiratory time were determined based on blood gas values, flow waveform, and exhaled tidal volume.

MEASUREMENT AND MAIN RESULTS

Forty patients were admitted for 51 episodes of severe status asthmaticus requiring mechanical ventilation. Before the institution of pressure-controlled ventilation, median pH and Pco(2) were 7.21 (range, 6.65-7.39) and 65 torr (29-264 torr), respectively. Four hours after pressure-controlled ventilation, median pH increased to 7.31 (6.98-7.45, p <.005), and Pco(2) decreased to 41 torr (21-118 torr, p <.005). For patients with respiratory acidosis (Pco(2) >45 torr) within 1 hr of starting pressure-controlled ventilation, the median length of time until Pco(2) decreased to <45 torr was 5 hrs (1-51 hrs). Oxygen saturation was maintained >95% in all patients. Two patients had pneumomediastinum before pressure-controlled ventilation. One patient each developed pneumothorax and subcutaneous emphysema after initiation of pressure-controlled ventilation. All patients survived without any neurologic morbidity. Median duration of mechanical ventilation was 29 hrs (4-107 hrs), intensive care stay was 56 hrs (17-183 hrs), and hospitalization was 5 days (2-20 days).

CONCLUSIONS

Based on this retrospective study, we suggest that pressure-controlled ventilation is an effective ventilatory strategy in severe status asthmaticus in children. Pressure-controlled ventilation represents a therapeutic option in the management of such children.

Management of respiratory failure in status asthmaticus

Status asthmaticus is a life-threatening episode of asthma that is refractory to usual therapy. Recent studies report an increase in the severity and mortality associated with asthma. In the airways, inflammatory cell infiltration and activation and cytokine generation produce airway injury and edema, bronchoconstriction and mucus plugging. The key pathophysiological consequence of severe airflow obstruction is dynamic hyperinflation. The resulting hypoxemia, tachypnea together with increased metabolic demands on the muscles of respiration may lead to respiratory muscle failure. The management of status asthmaticus involves intensive pharmacological therapy particularly with beta-adrenoceptor agonists (beta-agonists) and corticosteroids. Albuterol (salbutamol) is the most commonly used beta2-selective inhaled bronchodilator in the US. Epinephrine (adrenaline) or terbutaline, administered subcutaneously, have not been shown to provide greater bronchodilatation compared with inhaled beta-agonists. Corticosteroids such as methylprednisolone should be administered early. Aerosolized corticosteroids are not recommended for patients with status asthmaticus. Inhaled anticholinergic agents may be useful in patients refractory to inhaled beta-agonists and corticosteroids. In patients requiring mechanical ventilation, the strategy aims to avoid dynamic hyperinflation by enhancing expiratory time to allow complete exhalation. Complications of dynamic inflation are hypotension and barotrauma. Sedation with opioids, benzodiazepines or propofol is required to facilitate ventilator synchrony but neuromuscular blockade should be avoided as myopathy has been a reported complication. Overall, in the management of patients with status asthmaticus, the challenge to the pulmonary/critical care clinician is to provide optimal pharmacological and ventilatory support and avoid the adverse consequences of dynamic hyperinflation.

The pulmonary physician in critical care . 12: Acute severe asthma in the intensive care unit

Most deaths from acute asthma occur outside hospital, but the at-risk patient may be recognised on the basis of prior ICU admission and asthma medication history. Patients who fail to improve significantly in the emergency department should be admitted to an HDU or ICU for observation, monitoring, and treatment. Hypoxia, dehydration, acidosis, and hypokalaemia render the severe acute asthmatic patient vulnerable to cardiac dysrrhythmia and cardiorespiratory arrest. Mechanical ventilation may be required for a small proportion of patients for whom it may be life saving. Aggressive bronchodilator (continuous nebulised beta agonist) and anti-inflammatory therapy must continue throughout the period of mechanical ventilation. Recognised complications of mechanical ventilation include hypotension, barotrauma, and nosocomial pneumonia. Low ventilator respiratory rates, long expiratory times, and small tidal volumes help to prevent hyperinflation. Volatile anaesthetic agents may produce bronchodilation in patients resistant to beta agonists. Fatalities in acute asthmatics admitted to HDU/ICU are rare.

The management of acute severe asthma

Asthma is a common cause of morbidity and mortality in the United States, with over two million Emergency Department (ED) visits each year. Airway inflammation is recognized as a major component in the pathophysiology of asthma. The classic presentation of asthma is that of wheezing, cough, and dyspnea, however, the severity of airflow limitation correlates poorly with clinical signs. Forced exhaled volume in 1 s (FEV(1)) and the peak expiratory flow rate (PEFR) are direct reflections of the severity of airflow obstruction and are the standard measures used in the ED to assess the severity of airflow obstruction and the response to therapy. Beta2-adrenergic bronchodilators, ipratropium bromide, and corticosteroids form the cornerstone of therapy. Inhaled corticosteroids, leukotriene modifying drugs, and noninvasive positive pressure ventilation should be considered in patients with severe disease and in those who have responded poorly to standard therapy. Mechanical ventilation is usually well tolerated and may be lifesaving in patients with refractory asthma. Precautions are required to prevent dynamic hyperinflation during assisted ventilation.

Clinical predictors of acute respiratory acidosis during exacerbation of asthma and chronic obstructive pulmonary disease

Mechanical ventilation (MV) during exacerbation of asthma or chronic obstructive pulmonary disease (COPD) is unequivocally needed when apnoea, cardiorespiratory arrest, coma, hypoxia or treatment failure is present. The need is less clear when the patient can respond, has intact airway reflexes and spontaneous respiration. In this situation, acidosis is an important factor in the decision to institute MV. This study aimed to provide a clinical means of identifying patients with acute respiratory acidosis (ARA) in a setting where blood gas analysis is unavailable. We undertook a prospective, observational study of consecutive patients who presented to two emergency departments with severe and life-threatening exacerbation of asthma or COPD. Each underwent clinical assessment, treatment and blood gas analysis. The outcome measure was ARA or mixed ARA and metabolic acidosis. A total of 127 episodes in patients aged 15-90 years (65.3% males and 34.7% females) were included in the study. Of these, 62.2% had asthma and 37.8% had COPD; 71.7% had life-threatening and 28.3% had severe attacks. Overall, the adjusted odds ratio (and 95% confidence intervals) for predictors of ARA were 7.09 (1.79-28.06) for drowsiness, 4.11 (1.31-12.88) for flushing, 3.34 (1.01-11.02) for having COPD and 2.86 (1.01-8.07) for intercostal retractions. In conclusion, with drowsiness, the likelihood of ARA is about seven times higher. The presence of flushing, COPD and intercostal retractions also increase the risk of ARA.

Clinical course and outcome of patients admitted to an ICU for status asthmaticus

STUDY OBJECTIVES

To describe the prognostic factors, clinical course, and outcome of patients with status asthmaticus treated in a medical ICU (MICU).

DESIGN

Analysis of prospective data.

SETTING

A multidisciplinary MICU of an inner-city university hospital.

PATIENTS

We collected data on 132 hospital admissions of 89 patients with status asthmaticus treated in our MICU from August 1995 through July 1998.

MEASUREMENTS

APACHE (acute physiology and chronic health evaluation) II scores were among the parameters measured.

RESULTS

Seventy-nine percent of the patients were female, and 67% were African American (mean +/- SD age, 42.4 +/- 15.1 years). Patients in 48 of the 132 hospital admissions (36%) required invasive mechanical ventilation; sepsis developed in patients during 17 hospital admissions (13%), nonpulmonary organ failure developed during 16 hospital admissions (12%), and ARDS developed during 2 hospital admissions (2%). Pneumothorax developed in four patients and required tube thoracostomy in all four patients. The median APACHE II score was 11. Predicted mortality and actual mortality were 6.7% and 8.3%, respectively. The two most common immediate causes of death were pneumothorax (n = 3) and nosocomial infection (n = 3). All the deaths occurred in female patients. Compared with survivors, nonsurvivors had higher APACHE II scores (median, 26 vs 15; p < 0.0001), PaCO(2) (63.8 +/- 21.3 mm Hg vs 47.8 +/- 19.1 mm Hg, p = 0.0101), and lower arterial pH (7.09 +/- 0.12 vs 7.27 +/- 0.12, p < 0.0001), respectively. Patients in 10 of 48 hospital admissions (21%) who required mechanical ventilation died.

CONCLUSIONS

The hospital mortality of patients admitted to an MICU for status asthmaticus is higher than expected. Higher APACHE II score and PaCO(2) and lower arterial pH within 24 h of hospital admission are associated with increased mortality. Sepsis and nonpulmonary organ failure are more likely to develop in nonsurvivors than survivors.

Status asthmaticus in children: a review

About 10% of American children have asthma, and its prevalence, morbidity, and mortality have been increasing. Asthma is an inflammatory disease with edema, bronchial constriction, and mucous plugging. Status asthmaticus in children requires aggressive treatment with beta-agonists, anticholinergics, and corticosteroids. Intubation and mechanical ventilation should be avoided if at all possible, as the underlying dynamic hyperinflation will worsen with positive-pressure ventilation. If mechanical ventilation becomes necessary, controlled hypoventilation with low tidal volume and long expiratory time may lessen the risk of barotrauma and hypotension. Unusual and nonestablished therapies for severe asthma are discussed.

Heliox does not improve FEV1 in acute asthma patients

Thirteen patients with an acute exacerbation of asthma and pre-treatment FEV1 between 20%-60% of predicted were tested to determine whether a blend of 70:30, helium:oxygen (heliox) improved FEV1. No pretreatment with bronchodilators occurred. The change in absolute and predicted FEV1 was measured after five minutes of breathing heliox. It was found that the absolute FEV1 during heliox was not significantly different from the absolute FEV1 before heliox. The difference between the absolute FEV1 during and before heliox was found to be -0.04 l. The percent predicted FEV1 during heliox was 40.8% +/- 13.0% vs. 41.5% +/- 11.9% before heliox. The difference between the percent predicted FEV1 during and before heliox was found to be -0.7%. We conclude that 70:30 heliox does not improve FEV1 in these patients.

Successful use of nasal BiPAP in three patients previously requiring intubation and mechanical ventilation

Noninvasive mask ventilation may be used to treat patients with impending respiratory failure. In this case series, three patients with severe chronic obstructive pulmonary disease, who required mechanical ventilation in the past, were successfully treated with nasal bi-level positive airway pressure (BiPAP). All patients tolerated BiPAP well without complications. Therefore, nasal BiPAP may be considered a treatment option for patients with severe COPD who have previously required intubation and mechanical ventilation.