Respiratory medicine


Respiratory medicine


Mark A Rodrigues and Emily R McCall-Smith


Outline





Initial Assessment




Breathing



ent Check respiratory rate and oxygen saturations


ent Look at the work of breathing: nasal flaring, use of accessory muscles. Is the patient able to complete sentences? Often patients with respiratory distress fix their rib cage and shoulder girdle by supporting themselves on straight arms and grasping the sides of the bed


ent Perform a respiratory exam, particularly assessing for chest wall movement, air entry into the lungs, and additional sounds (crackles or wheeze) on auscultation. Also look for signs of a pneumothorax by assessing the percussion note. Tracheal deviation, displacement of the apex beat away from the side of the pneumothorax and haemodynamic instability are clinical findings indicating a pneumothorax is under tension. This is a medical emergency, requiring urgent needle decompression


‘RR 35/min, oxygen saturations are 89% on room air. The patient is using his accessory muscles and unable to speak in full sentences. On auscultation, there is symmetrical chest wall movement, lung fields are resonant throughout, with reduced air entry at the base of the lungs, and a widespread bilateral polyphonic wheeze.’


You start the patient on high-flow oxygen via a non-rebreather mask (to maintain saturations between 94% and 98%). You prescribe 5 mg of salbutamol to be nebulized with oxygen.




image


Figure 3.1



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Figure 3.2






Initial Investigations




ent ABG: Perform if (a) the SpO2 is<92% or (b) if there are any features of life-threatening asthma. Patients are likely to be hypoxic. The PaCO2 is likely to be low (due to hyperventilation), causing a respiratory alkalosis (low H+/high pH). However, if a patient becomes exhausted, their respiratory rate will reduce, and the PaCO2 will go from low to normal to high (indicating a near-fatal exacerbation)


ent Bloods: Check Hb (for anaemia), U&Es (for dehydration and to monitor potassium when giving salbutamol), WCC, CRP±blood cultures (for evidence of infection). Theophylline levels if on aminophylline


ent Peak flow: This helps measure the severity of an asthma attack (Table 3.1), as well as the response to treatment. It is most useful if measured as a percentage of a patient’s previous best, but it can also be measured as a percentage of predicted (which is based on height, sex and age)


ent ECG: Arrhythmias can be a sign of a life-threatening attack (or if not a clear asthma history, could be an alternative diagnosis)


ent CXR is indicated if:


ent there are any life-threatening features of asthma


ent there is another diagnosis suspected, e.g. pneumothorax


ent bacterial infection is suspected


ent failure to respond to treatment


ent prior to CPAP/BiPAP/intubation


‘The patient’s peak flow is 40% of his usual best. ABG on air shows hypoxaemia and a respiratory alkalosis (PaO27 kPa, PaCO23.1 kPA, H+28 nmol/L (pH 7.55), and HCO320.3 mmol/L). CXR shows hyperinflation. The lungs are clear, no pneumothorax. ECG shows sinus tachycardia. Bloods are normal.’




Initial Management [1]



ent Oxygen: Should be given to all hypoxic patients. Aim for saturations of 94–98%


ent Salbutamol: 5 mg nebulized with oxygen should be given as soon as possible. These can then be given ‘back-to-back’, i.e. every 10 minutes if the initial response is poor. Only consider IV beta-2 agonists for those who are unable to undergo inhaled therapy


ent Ipratropium bromide: 500 micrograms every 4–6 hours, nebulized, if the attack is severe or life-threatening or if there is a poor response to nebulized salbutamol


ent Corticosteroids: 40 mg prednisolone (oral) or 200 mg hydrocortisone (IV) if unable to swallow. Corticosteroids should be given in all cases of acute asthma. Oral corticosteroids are as effective as IV corticosteroids if the patient can absorb them. Continue for at least 5 days or until recovery


ent Antibiotics: Only required if there is any evidence of an infection (pyrexia, crackles on auscultation/consolidation on CXR, or raised WCC/CRP)


ent Review medications: May need to stop drugs such as beta-blockers and sedatives.






Definitive Management



ent Ideally patients should be admitted under a respiratory specialist rather than to a general ward


ent Aim to identify the trigger that precipitated the asthma attack


ent Continue regular nebulized therapy initially, e.g. salbutamol 5 mg every 4 hours±ipratropium bromide 500 micrograms every 6 hours


ent After 24 hours, consider changing nebulized salbutamol to inhaled salbutamol, and adding in high-dose inhaled corticosteroid


ent Continue 40 mg of prednisolone for at least 5 days. The dose does not need to be tapered down, unless the patient is on maintenance corticosteroid treatment or has been on corticosteroid treatment for>3 weeks


ent Prescribe ongoing oxygen requirement, e.g. 2 L/min via nasal cannulae


ent Don’t forget to prescribe DVT prophylaxis as long as there are no contraindications


ent Patients can be discharged when they are no longer requiring nebulized therapy, and when the beta-2-agonist therapy can be stretched to every 4 hours


ent Prior to discharge the PEFR should be>75% of best/predicted, with<25% diurnal variation


ent Patients should be discharged with a personal self-management asthma plan and their inhaler technique should be assessed


ent After discharge, patients should be reviewed by an asthma-specialist within 30 days.






Initial Assessment








Initial Investigations



In contrast to asthma, peak flow is not useful in the management of acute COPD. image



ent ABG: One of the most important investigations in an exacerbation of COPD. It allows assessment of the degree of oxygenation (PaO2) and ventilation (PaCO2). Check within 20 minutes of starting or changing flow of oxygen. Aim for a PaO2>6.6 kPa and H+<55 (pH>7.25). If this is achieved, increase the oxygen to achieve PaO2>7.5 kPa. Aim for oxygen saturations of 88–92%. If possible, compare to a baseline, e.g. clinic ABG result


ent CXR: To exclude other causes of dyspnoea, especially a pneumothorax. Look for areas of consolidation. This is a priority investigation and may need to be a portable CXR if the patient is not stable enough to go to the X-ray department


ent ECG: Look for evidence of a myocardial infarction or arrhythmias


ent Bloods: FBC, U&Es, CRP. Look for evidence of infection, check for anaemia, assess renal function. Theophylline levels if on aminophylline


ent Blood culture: If the patient is pyrexial


ent Sputum culture: If the patient has purulent sputum


‘ABG (on 2 L/min oxygen) PaO26.0 kPa, PaCO23.1 kPa, H+33 nmol/L (pH 7.48), HCO326 mmol/L. WCC 8.6×109/L. CRP is 12 mg/L. Renal function is normal. CXR shows hyperinflated lungs with coarsening of the background markings in keeping with COPD. No consolidation or pneumothorax. ECG: sinus rhythm.’


Nov 18, 2017 | Posted by in PHARMACY | Comments Off on Respiratory medicine
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