Halothane treatment in life-threatening asthma

Acute Severe Asthma in Adolescent and Adult Patients: Current Perspectives on Assessment and Management

Asthma is a chronic airway inflammatory disease that is associated with variable expiratory flow, variable respiratory symptoms, and exacerbations which sometimes require hospitalization or may be fatal. It is not only patients with severe and poorly controlled asthma that are at risk for an acute severe exacerbation, but this has also been observed in patients with otherwise mild or moderate asthma. This review discusses current aspects on the pathogenesis and pathophysiology of acute severe asthma exacerbations and provides the current perspectives on the management of acute severe asthma attacks in the emergency department and the intensive care unit.

Inhalational anesthesia: basic pharmacology, end organ effects, and applications in the treatment of status asthmaticus

The potent inhalational anesthetic agents are used on a daily basis to provide intraoperative anesthesia. Given their beneficial effects on airway tone and reactivity, they also have a role in the treatment of status asthmaticus that is refractory to standard therapy. Although generally not of clinical significance, these agents can affect various physiological functions. The potent inhalational anesthetic agents decrease mean arterial pressure and myocardial contractility. The decrease in mean arterial pressure reduces renal and hepatic blood flow. Secondary effects on end-organ function may result from the metabolism of these agents and the release of inorganic fluoride. The following article reviews the history of inhalational anesthesia, the physical structure of the inhalational anesthetic agents, their end-organ effects, reports of their use for the treatment of refractory status asthmaticus in the intensive care unit (ICU) patient, and special considerations for their administration in this setting including equipment for their delivery, scavenging, and monitoring.

Therapeutic applications and uses of inhalational anesthesia in the pediatric intensive care unit

OBJECTIVE

To review the physical properties, end-organ effects, therapeutic applications, and delivery techniques of inhalational anesthetic agents in the pediatric intensive care unit.

DATA SOURCE

A computerized, bibliographic search regarding intensive care unit applications of inhalational anesthetic agents.

MAIN RESULTS

Although the end-organ effects of inhalational anesthetic agents vary depending on the agent, general effects include a dose-related depression of ventilatory and cardiovascular function. With increasing anesthetic depth, there is a decrease in alveolar ventilation with a reduction in tidal volume and an increase in PaCO2 in spontaneously breathing patients. The potent inhalational anesthetic agents decrease mean arterial pressure and myocardial contractility. The decrease in mean arterial pressure reduces renal and hepatic blood flow. Secondary effects on end-organ function may result from the metabolism of these agents and the release of inorganic fluoride. Beneficial effects include sedation, amnesia, and anxiolysis, making these agents effective for sedation during mechanical ventilation. Bronchodilatory and anticonvulsant properties have led to their use as therapeutic agents in patients with refractory status asthmaticus and epilepticus. Issues regarding their delivery in the intensive care unit include equipment for their delivery, scavenging, and monitoring.

CONCLUSIONS

The literature contains reports of the therapeutic use of the potent inhalational anesthetic agents in the pediatric intensive care unit. Potential applications include sedation during mechanical ventilation as well as therapeutic use for the treatment of status asthmaticus and epilepticus.

Acute asthma during pregnancy

In addition to preventing maternal and fetal hypoxia, the goals of treating acute asthma exacerbation during pregnancy mirror those in the nongravid patient: rapid reversal of airflow obstruction with aerosolized bronchodilators,reduction of likelihood of recurrence by the addition of corticosteroids, and ongoing assessment of mother and fetus. Disposition decisions are multifaceted and must take into account the health and well-being of the pregnant patient and that of her fetus. Discharge planning includes prescription of scheduled 3-2 agonist treatments until symptoms resolve, intensification of daily treatment as needed, prescriptions for systemic and ICSs, as well provision of patient education, a personalized action plan, and close follow-up.

Respiratory effects of halothane in a patient with refractory status asthmaticus

We describe the case of a 36 year old patient who was admitted to the intensive care unit (ICU) for an acute asthma attack that failed to respond to conventional treatment and required mechanical ventilation. The patient's condition improved after halothane was administered; treatment with this inhalational anaesthetic lasted 7 h, and the beneficial effect was obtained by employing concentrations between 0.5 and 2%. Under constant mechanical ventilator settings, a highly significant linear correlation between peak airway pressure and arterial pCO(2)(r: 0.98 P<0.001) was observed. The decrease in p(a)CO(2)induced by halothane may be explained by the diminished dead space that results from the drop in peak airway pressure. Arterial hypotension, which improved with inotropic agents, was the only complication that seemed related to the inhaled anaesthetic. The patient was extubated 24 h after her arrival to the ICU and discharged 72 h later. A causal relationship between the administration of halothane and clinical improvement is suggested.

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.

Emergent management of acute asthma

In almost no other field is the gap between diagnostic and therapeutic knowledge and its general application so great as it is in asthma. As previously mentioned, most asthma deaths are preventable. Identification of high-risk patients, intensive education about asthma (purpose of each medication; necessity of compliance, particularly with inhaled corticosteroids; proper use of inhalers and spacer devices; home use of PEFR meter), self-treatment of mild or moderate attacks with oral corticosteroids, and written crisis plan for severe attacks explicitly telling the patient what to do and whom to call are necessary. In addition, all potential exacerating factors should be eliminated (external triggers, medication, gastroesophageal reflux, allergic rhinitis, and sinusitis). High doses of inhaled corticosteroids should be provided to all those patients, and referral to a specialist is highly recommended for such high-risk patients.

Status asthmaticus complicated by atelectasis in a child

A case of an 11-year-old boy who was admitted for severe status asthmaticus complicated by extensive atelectasis is reported. Atelectasis involved all left lobes and the right upper lobe of the lung. Although the patient was refractory to maximal medical therapy and continued to deteriorate after intubation, he responded dramatically to the administration of isoflurane. Atelectasis was reduced immediately after fiberoptic bronchial lavage and the use of high frequency ventilation, with a marked improvement in blood gases. Isoflurane provided sedation during prolonged mechanical ventilation without significant adverse effects, aiding the care of this pediatric patient who ultimately recovered.

Treatment of critical status asthmaticus in children

Status asthmaticus is complex in its etiology and pathophysiology and may be associated with significant morbidity and mortality. Although there are many therapeutic options, specific inhaled beta 2-agonists, corticosteroids, and oxygen remain the mainstay of therapy. Several new drugs and some older drugs are being used in management; their exact role in treatment at present, however, relies largely on personal preferences. Innovative methods of providing ventilatory support are also emerging. What is quite clear is the fact that involvement of specialists (pulmonologists and intensivists) early in the course of severe status asthmaticus is needed to ensure optimal management and possibly favorable outcomes.

Treatment of acute severe asthma assisted by hypothermia

A 20-year-old woman in status asthmaticus who failed to respond to conventional therapy and ventilation of the lungs with 0.5-2.0% halothane, was cooled to 30 degrees C for almost 5 days as the arterial carbon dioxide tension rose above 15 kPa. Halothane was not of immediate value, contrary to other reports. A reduction in carbon dioxide production by controlled hypothermia permitted more suitable ventilation parameters, but extensive muscle weakness caused by a steroid-induced myopathy complicated weaning from respiratory support. Prospective measurement of serum creatinine phosphokinase concentration in patients given high dose corticosteroids may herald the onset of a myopathy.

Respiratory and hemodynamic effects of halothane in status asthmaticus

The respiratory and hemodynamic effects of halothane in patients with status asthmaticus who required mechanical ventilation was evaluated. Halothane was administered in 12 patients in a concentration of 1% for thirty minutes. Standard drug treatments and ventilator settings were not modified during halothane administration. The following data were collected before and after halothane administration: arterial blood gases, peak inspiratory pressure, VD/VT, pulmonary arterial pressure, right heart pressures and cardiac index (by means of the thermodilution method). After halothane treatment PaCO2 significantly decreased, arterial pH increased, peak inspiratory pressure decreased and VD/VT decreased significantly. Mean pulmonary arterial pressure and right heart pressures decreased and the cardiac index was unchanged. The heart rate significantly decreased and arrhythmias did not occur during halothane administration. The administration of halothane in patients with status asthmaticus requiring mechanical ventilation produces a rapid reduction in bronchospasm and barotraumatic injury and a rapid improvement in arterial blood gases, without any adverse hemodynamic effects.

Mechanical ventilation in patients with acute severe asthma

PURPOSE

Acute respiratory failure necessitating intubation and mechanical ventilation in patients with acute severe asthma is relatively uncommon, and there are few data available regarding positive pressure ventilation in critically ill patients with asthma. We therefore decided to evaluate our experience with the use of mechanical ventilation for acute asthma and to critically review previous reports on this subject.

PATIENTS AND METHODS

A retrospective analysis of all medical records of patients who required mechanical ventilation for acute severe asthma was performed for the period of 1980 to 1988. Various clinical parameters were reviewed and examined via Fisher's exact test for association with survival.

RESULTS

Twenty-seven patients who underwent ventilation for a total of 32 episodes of mechanical ventilation comprised our study group. The overall mortality was 22%. A total of 76 complications were documented, including six episodes of barotrauma. The mean duration of artificial ventilation was 114 hours for nonsurvivors and 77 hours for survivors (p less than 0.05).

CONCLUSION

Although there appears to be a trend toward increased survival after mechanical ventilation for acute asthma, ventilation of critically ill asthmatic patients continues to be a potentially perilous venture associated with significant morbidity and mortality.

The use of ketamine for the emergency intubation of patients with status asthmaticus

We describe five patients with status asthmaticus whose respiratory acidosis persisted despite conventional treatment. Four were intubated with ketamine and succinylcholine and mechanically ventilated with immediate improvement of respiratory acidosis. One patient had been intubated previously with diazepam and succinylocholine and had a rise in pCO2 to 97. Ketamine was given IV with a rapid fall in pCO2. This improvement immediately after intubation is in contrast to previous reports of asthmatics whose respiratory acidosis and bronchospasm worsened immediately after intubation.

[Intracranial hypertension during status asthmaticus]

In three consecutive patients suffering from life-threatening asthma in a comatose state (mean age: 37 +/- 4 yr; Glasgow coma score: 3; bilateral mydriasis), intracranial pressure was monitored with an extradural transducer set-up a mean of 2 h after the onset of the coma. The aims were to detect intracranial hypertension and to improve its therapy. Basal therapy associated: 1) mechanical ventilation; 2) theophylline 1.5 g X 24 h-1, salbutamol 30 mg X 24 h-1, hydrocortisone 2 g X 24 h-1, pancuronium 0.5 mg X kg-1 X 24 h-1; 3) pentobarbitone 35 mg X kg-1 X 24 h-1, normal hydration, normothermia and 30 degrees head-up tilt. If the intracranial pressure rose above 15 mmHg, an i.v. bolus of pentobarbitone (5 mg X kg-1) was given if the barbiturate blood level was equal or below 100 micrograms X l-1. In case of failure, a dose of mannitol (20 mg) completed the therapy if blood therapy was equal or below 320 mosm X l-1. All patients developed intracranial hypertension (21, 53 and 23 mmHg, respectively). The intracranial hypertension followed the bronchospasm and disappeared with it. Hypoxaemia, hypercapnia and high peak airway pressures could explain the intracranial hypertension. All patients recovered without sequelae. This data should make us use with great care all treatments likely to increase the intracranial pressure during life-threatening asthma.