Asthma - ACEM Fellowship Notes

See: [Ventilation_in_special_circumstances](x-devonthink-item://73C66D50-5D35-4744-BE63-5E36BA71F4F8) [[Ventilator strategies]], [[Peri-intubation collapse#severe asthma]], [[Non-invasive ventilation#NIV in asthma]] - [Dunn - management of life threatening asthma](x-devonthink-item://CBC59DA3-02B4-42A5-9B7E-2AC82FE8BEBF) # Pathophysiology - hyper-reactive airways and inflammation leading to episodic, reversible bronchoconstriction # Thunderstorm Asthma - triggered by thunderstorms causing grass pollen to be swept into clouds as storm forms → pollen absorbs moisture → releases allergen particles → breath into lungs → severe asthma sx - usually **late spring, early summer** when pollen load highest - ↑ risk if hx of asthma, hay fever, seasonal hay fever # Mild-moderate asthma # Severe, life-threatening asthma # Treatments | drug | dose | mechanism | indications | issues | | ------------- | ------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | salbutamol | - 4-12 puffs Q20 min - 5mg neb if severe/life-threatening | bronchodilator | all severities | metabolic acidosis w/ resp compensation | | ipatropium | - 8 puffs (21mcg/puff) Q20 min - 500mcg nebule | | | | | oxygen | aim sats >92% | | | need to match flow rate to resp rate | | magnesium | 10 mmol IV over 20-30 min | ? bronchodilator and anti-inflammatory effects | acute severe asthma with poor response or life-threatening | - hypotension | | steroids | - 100mg IV hydrocort Q6H - pred 37.5-50mg po | - delayed leukotriene response | | | | ketamine | - ~8mg/H on BiPAP - 0.5-1 mg/kg/h intubated | - sympathomimetic effects - relax bronchial smooth muscle - histamine antagonism | | | | aminophylline | - 5mg/kg loading odse 20 min - 0.3-0.6 mg/kg/h | - direct relaxation of bronchial smooth muscle → improves bronchospasm - inhibition of phosphodiasterases → ↑ cAMP → reduce Ca into cells → inhibit smooth muscle contraction | - very severe asthma refractive to all other attempts | - multifocal atrial tachycardia - need to be cardiac monitored - relative contraindication if pt *already on oral theophylline* - specialist input - children tolerate CVS toxic effects better than adults | | adrenaline | | - beta agonist | - can use in treatment-resistant asthma | - may be useful in severe/critical asthma where they are hypotensive as well | | NIV | | - helps ventilation | - severe asthma with tiring patient - unknown whether CPAP or BiPAP is optimal | - avoid very high PEEP | # Asthma ventilation See also [[Ventilator strategies]], [[Peri-intubation collapse]] # Cardiac arrest in asthma **causes** - critical lung hyperinflation - decreased preload to [[Right heart failure|RV]] - increased pericardial pressure - increased pulm vascular resistance and RV strain - tension pneumothorax **management** - treat tension Ptx if present - tx hypoxia and acidosis - tx hyperkalemia if present - ETT complications - displacement - obstruction eg mucous plugs - Ptx - equipment - secretions or dysynchrony --- # paediatric asthma see : [RCH Asthma](https://www.rch.org.au/clinicalguide/guideline_index/Acute_asthma/) #paeds # pre-school wheeze vs asthma See: [RCH preschool asthma](x-devonthink-item://355F3AA6-886F-4AB3-8954-10CE1DB9C78A) - unclear if preschool wheeze is same pathophysiology as asthma later in life, which is why the term ‘asthma’ is not used - Generally preschool wheeze in age <6 - Pre-school wheeze usually triggered by virus (eg RSV, parainfluenzae, adenovirus - Risk for developing asthma: maternal asthma, personal history of atopy, onset of wheeze > 18 months - Wheeze <1 year usually caused by [[Bronchiolitis]] - Only half of kids who have preschool asthma/wheeze will have asthma at school age **However**, recent recognition at how confusing it is to say “this isn’t asthma” and then give an asthma action plan, so there has been a recent push at RCH to change terminology and call this “preschool asthma” to streamline terminology since treatment is quite similar ![[293674CF-F8C9-4D4D-977F-0DD6C25CB13D.jpeg]] # paeds asthma severity |**Severity**|Mild|Moderate|Severe|**Life threatening**| |---|---|---|---|---| |**Features**|- Mild increased work of breathing (WOB) - Normal respiratory rate - Alert and active|- Moderate increased work of breathing - Increased respiratory rate - Active and alert|- Markedly increased work of breathing - Increased respiratory rate - Agitated - Pale - Other signs of [anaphylaxis](https://www.rch.org.au/clinicalguide/guideline_index/anaphylaxis/)|- Maximal work of breathing - Increased respiratory rate - Confused/ drowsy - Not moving - Cyanosed - Other signs of [anaphylaxis](https://www.rch.org.au/clinicalguide/guideline_index/anaphylaxis/)| ## management - O2 aim sats >90% - 12 puffs salbutamol MDI Q20 min x3 doses + 8 puffs ipatropium Q20 min 3 doses - (6 salbutamol and 4 puffs ipatropium if 1-5) - hydrocort 4mg/kg IV Q6H or methylpred 1mg/kg or dex 0.6mg/kg - cont salbutamol 6-12 puffs 1-2 hourly *if not improved after 30 min tx as life threatening* **If life threatening:** - 5mg salbutamol nebules + 500mcg ipatropium continuously (1/2 this dose if age <6) - **magnesium sulfate** 0.2 mmol/kg IV over 20 min - aminophylline 10mg/kg IV over 30 min **in a separate line** ## mild asthma flowchart ![[Pasted image 20230825004914.png]] ## moderate asthma flowchart ![[Pasted image 20230825011546.png]] ## Severe asthma flowchart ![[Pasted image 20230825011600.png]] ## life-threatening asthma flowchart ![[Pasted image 20230825011612.png]] # Critical paeds asthma hypotensive therapies to consider in intubated pt **bronchodilators** - adrenaline IV 5-25mcg/kg/min - salbutamol IV 5mcg/kg bolus up to 200mcg, then 1-20 mcg/min - aminophylline - ketamine bolus 1-3mg/kg/hour titrate to SPO2 ?92, MAP >65 - MgSO4 10-20 mmol IV - ipatropium 500mcg nebulised - volatile anaesthetic -- referral to anaesthetics/ICU for sevoflurane aiming MAC 1 **additional therapies** - treat for pneumothorax - bilat needle or finger thoracostomies - fluid bolus 1L titrate MAP > 65 - disconnect ETT for manual chest decompression - obstructive ventilation strategy: RR 6-8, low TV, IE 1:5 or above, accept high plateau pressure, permissive hypercapnia - paralysis - rocuronium 1.5 mg/kg IV bolus / cisatracurium IV - early referral for ECMO #paeds