o2 Asthmatic die from hypoxia Keep Sp02 > 94% A slight ∧ in Pco2 may occur, (not clinically significant)
Bronchodilators Salbutamol First line therapy Nebulizer (back to back nebs) Dose? Not improving consider IV (back door) Monitor K Salbutamol toxicity= ∧Lactic acidosis
Anticholinergics Ipratropium bromide Blocks muscarinic receptors in smooth muscle, resulting in bronchodilation Dose: 500mcg Can give up to 3 dose’s initially then ever 4/24
Mg Controversial Best evidence is in the sick/dying asthmatic Cause smooth relaxation, inhibits histamine & acetylcholine release from nerve endings Indicated when bronchodilators are failing Dose: 2-4mg over 30-60mins
Steroids Prednisolone vs Hydrocortisone Given within 1st hour greatly reduces hospital admission Target airway oedema and secretions via anti-inflammatory role Dose: Pred 50mg PO, Hydrocort 100-200mg IV
Adrenaline Given via Neb or IV Alpha effects target ∨ airway oedema Beta effect target ∨bronchodilation Used as a rescue therapy in the hypotensive, poor responding asthmatic Dose: Neb 1-6mg in 3ml Nacl Dose: IV 6mg in 100mls 5% dextrose (1-15mls/Hr), “also push dose’s 0.10-0.50mcg”.
AB’s Not routinely indicated Give Underlying pneumonia/bacterial cause Preventing VAP
NIV Becoming more popular, (research, case reports) Unloads resp muscles, augments alveolar ventilation until asthma resolves. CPAP vs BiPAP Start with low IPAP & EPAP Good indicator which patients need intubating
What the literature says on NIV. Clinical Evidence:
Intubating Ketamine for bronchodilator effects Use rapid sequence intubation Fluid bolus before (pre-load) Allow permissive hypercapnea
Challenges of Mechanical Ventilation Effective pre-oxygenation difficult No margin for error or delay Need to be intubated by most senior person available Develop high Intrathoracic pressure after RSI Intubation causes higher mortality via= lung hyperinflation, VILI, cardiovascular collapse.
The BIG issue Asthmatics require prolonged expiratory times Severe asthma pt initiates inspir before expir ceases Results in increase lung volume, auto-peep and hyperinflation Minimizing hyperinflation and avoiding excessive airway pressures are the goals Use low RR and prolonged exhalation times Allow Co2 to rise, but keep pH .7.15 Monitor (P plat) >30 cm H20 against expir time
Initial Ventilator Settings Assist control mode Tidal volume 7-8mL/kg (use ideal body weight) RR 10-12bpm Fi02: 100% PEEP: 0cm H20 Patients require deep sedation to tolerate the Vent.
Crashing Ventilated Asthmatic D.O.P.E.S.
Take Home Points Assessment skills are paramount Maximizing therapy to prevent MV is the GOAL!!! Mg works in the sick asthmatic NIV works Experience makes a big difference These patients will challenge you