Archive for the ‘Asthma’ Category
Posted by James
We installed two waste gas scavenging systems into the operating room. This was simple and inexpensive, as the ICU is contiguous with the operating room.
An adequate scavenging device can be made by connecting the exhaust port of the ventilator to a T- piece that is attached to a 3-L reservoir bag. Wall suction is applied to the remaining limb of the T-piece until the reservoir bag partially fills with each breath, but never fully collapses. Leaks are readily detectable, since isoflurane has a characteristic pungent odor.
Since this is a nonrebreathing system, a great deal of isoflurane is vaporized hourly. The cost for 24 h of continuous use is high, but it is partially offset by decreased use of other sedatives and muscle relaxants.
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Posted by James
Isoflurane produces bronchodilation through (3-ad- renergic receptor stimulation, direct relaxation of bronchial smooth muscle, antagonism of the action of acetylcholine and histamine, and interference with hypocapnic bronchoconstriction. Thus, a patient who is already receiving maximum doses of standard bron- chodilators may show an additional response. As our case reports suggest, isoflurane acts rapidly and may be lifesaving while high-dose corticosteroids take effect. In contrast, ketamine, an intravenous anesthetic agent that has also been used in asthma, acts by adrenergic stimulation. Little response is seen in patients receiving large doses of P-agonists and theophylline.
There are several advantages of isoflurane over other inhalational anesthetic agents. Historically, diethyl ether and cyclopropane were used, but their extreme flammability precluded their use in electrically active environments. Isoflurane is the least fat soluble of the anesthetic vapors and has the lowest blood gas solubility coefficient. Consequently, depth of anesthesia can be most rapidly adjusted with isoflurane, and time to recovery of consciousness is short, despite prolonged use.
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Posted by James
Case 3
A 27 month-old-boy was admitted to the pediatric ICU for the third time suffering from an exacerbation of asthma. The day prior to hospital admission he had been exposed to grass and pollen on a farm. At a rural hospital he was given albuterol, prednisone, and oral theophylline and transferred to our hospital. En route, he received hydrocortisone 125 mg IV and albuterol inhalations. The ABG values on admission were a pH of 6.94, Pco2 of 132 mm Hg, and Po2 of 79 mm Hg. Heart rate was 168 beats per minute and RR was 22 breaths per minute. Chest roentgenogram showed marked hyperinflation with no consolidation or pneumothorax. Following sedation with fentanyl and paralysis with pancuronium bromide, he was intubated. Subsequent ABG values were pH of 7.01, Pco2 of 122 mm Hg, and Po2 of 106 mm Hg (FIo2 of 0.7). The PIP was 44 cm H20. Positive end-expiratory pressure of 4 cm H20 was added. Drug therapy included methylprednisolone 15 mg IV every eight hours, albuterol 2 jig/kg/min IY atropine 0.6-mg inhalations, and aminophylline 10 mg/h IV (theophylline levels maintained at 16 to 20 mg/L).
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Posted by James
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.
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Posted by James
Tnhalational anesthetic agents have been sporadically used for status asthmaticus unresponsive to maximal standard therapy. Unfortunately, many agents have serious side effects and the delivery systems have been difficult to use outside the operating room, particularly in patients with high airway pressures.
Isoflurane, a halogenated ether, is an anesthetic agent that produces bronchodilation through a number of mechanisms. Recent technologic developments allow isoflurane to be easily and safely administered for prolonged periods of time to patients with severe bronchospasm.
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Posted by James
These considerations have prompted others to investigate simpler techniques of aerosol delivery in acute asthma. Recently, it has been suggested that p- agonist delivered by metered dose inhaler with a spacer device is simpler and as effective as В N in this setting. However, some acutely ill patients are unable to use these devices properly while others are psychologically not prepared to accept a form of therapy that they perceive as already having failed at home. Continuous nebulization may achieve the goal of simplifying treatment while introducing a new mode of bronchodilator delivery in patients with acute airway obstruction.
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Posted by James
This study compared CN of P-agonists with the standard method of BN in the initial emergency department management of asthma. Both methods were demonstrated to be effective with no significant differences in their bronchodilator activity or toxicity. Bolus nebulization was associated with a more rapid initial response, whereas FEV, improved progressively with CN. The change in FEV, was greater with CN than BN and had not yet reached a plateau after 2 hours with the former. However, the initial FEV, was lower in the CN group and this may have contributed to the aparently greater response in these patients. At the end of 2 hours, FEV, was virtually identical in both arms and we believe that the treat¬ments were equally efficacious.
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