Isoflurane Therapy for Status Asthmaticus in Children and Adults: CASE REPORTS

Case 1

A 20-vear-old woman with a seven-year history of asthma was admitted to the hospital with a history of worsening bronchospasm for one week following a flu-like illness. She had l>een using albuterol, ipratropium, and l>eclomethasone inhalers without im­provement. She was transferred to our Intensive Care Unit (ICU) owing to increasing respiratory distress. On admission to the ICU, her heart rate (HR) was 120 lieats per minute, respiratory rate (RR) was 18 breaths per minute, and Mood pressure (BP) was 150/80 mm Hg. Initial arterial blood gas (ABC) determinations were a pH of 7.30, Pco, of 35 mm Hg, and P<>2 of 45 mm Hg. Complete blood cell count (CBC), electrolytes, and liver function test results were normal.

Supplemental oxygen was given and an aininophylline infusion at 60 mg/h was begun. Albuterol 2.5 mg every four hours was alternated with atropine inhalations 1.2 mg every four hours, such that an inhalation treatment was received every two hours. Meth- ylprednisolone 250 mg intravenously (IV) was given every six hours. Theophylline levels were maintained within the therapeutic range. The inhaled bronchodilators were administered with increasing frequency due to worsening bronchospasm, until administration occurred every 15 minutes. Twelve hours after ICU admission, ABG values were a pll of 7.22, Pc:o2 of 55 mm Hg, and Po2 of 137 mm Hg. She was intubated and ventilated, after sedation with diazepam and paralysis with pancuronium bromide. Her broncho­spasm worsened and ventilation became increasingly difficult. Despite manipulations in inspiratory flow, tidal volume, and RR, Pco2 rose to 77 mm Hg, and peak inspiratory pressure (PIP) was in excess of 60 cm H20.
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Isoflurane inhalation was initiated, using a ventilator (Siemens Servo 900C) with attached vaporizer (Siemens Electronics, Calgary, Canada). Treatment with all other medications except steroids was discontinued. The isoflurane concentration was quickly increased to 1 percent. Over the next 90 minutes, PIP fell to 50 cm H20 and static compliance rose from 0.012 to 0.02 L/cm H20. The PaCO, fell to 44 mm Hg and pH rose to 7.32. Within five hours there was marked clinical improvement. Table 1 shows the change in dynamic compliance, Pco2, and HR during the use of isoflurane. The mean arterial BP remained above 70 mm Hg throughout therapy.

Table 1—Changes during Isoflurane Use

HR,

Pco2,

Beats per

BP,

Time

mm Hg

Compliance

Isoflurane, %

Minute

mm Hg

1440

67

0.6/62

0

155

170/115

1455

57

0.676/70

1

180/70

1530

54

0.710/70

1

125/75

1610

44

0.770/50

1

150

105/75

1820

39

0.770/40

1

125

140/70

2130

32

0.790/30

1

125

110/60

0115

32

0.786/32

1

120

115/60

0430

30

0.724/40

1

105

110/70

0750

32

0.720/40

1

105

110/65

Isoflurane was continued for 16 hours and therapy with albuterol and aminophvlline recommenced. Isoflurane treatment was discon­tinued when bronchospasm resolved and it seemed likely that the patient would tolerate extubation. Awakening occurred in 20 min­utes, and she was extubated 40 minutes after the isoflurane treatment was discontinued.

The remainder of her hospital course was unremarkable. Although her aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) levels increased transiently on day 2 to 170 U/L and 412 U/L, respectively, the values returned to normal the next day. There was no clinical evidence of hepatic damage. All other laboratory values remained within normal limits.

Case 2

An 18-year-old male patient, with a long history of severe asthma since childhood, awoke at home with severe dyspnea. Long-term medications included theophylline, cromolyn sodium (cromoglycate sodium), and albuterol. He arrived in the Emergency Department unconscious and had gasping respirations. Initial ABG values were a pH of 6.77, Pco2 of 162 mm Hg, and Po2 of 133 mm Hg. After intubation he was given aminophylline 150 mg IV loading dose, followed by an infusion at 40 mg/h, methylprednisolone 250 mg every six hours IV, albuterol 20 jig/min IV, and ipratropium 0.5 mg by inhalation, alternating with albuterol 5 mg by inhalation every 15 minutes. Fentanyl, diazepam, and pancuronium bromide were given as needed.
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One hour after intubation, ABG values were a pH of 6.85, Pco2 of 145 mm Hg, and Po2 of 499 mm Hg (FIo2 of 1.0). The PIP was 72 cm H20. Treatment with 1 percent isoflurane was commenced. Within one hour, Pco2 fell to 71 mm Hg and the isoflurane concentration was decreased to 0.6 percent. Because the PIP remained at 70 cm H20, bronchoscopy was performed for the removal of mucous plugs, but few were found. He was maintained on a regimen of aminophylline, methylprednisolone, and inhaled albuterol while ventilated. After 34 hours of isoflurane anesthesia, and once he had been stable for several hours with a Pco2 of 35 mm Hg and a PIP of 36 cm H20, the isoflurane treatment was discontinued. He was placed on a T-piece 55 minutes after the isoflurane treatment was stopped and was extubated four hours later. He had an uneventful hospital course. No hepatic or renal biochemical abnormalities ensued.


Category: Asthma

Tags: Isoflurane Therapy, Status Asthmaticus

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