Viva 6

Created on Thu, 12/17/2015 - 10:57
Last updated on Wed, 05/09/2018 - 06:07

As the duty locum Intensivist you have been called to urgently review a patient on the medical ward of a small private hospital. The patient, Jane, is a 62-year-old female who was admitted to the ward yesterday with shortness of breath and leg swelling.

She presents with shortness of breath often, and has recently been started on a bronchodilator.

A local GP registrar was on the ward reviewing another patient and noticed that Jane was working very hard to breathe. The registrar emergently intubated her prior to your arrival.

You arrive on the ward 10 minutes post intubation. The registrar and a ward nurse are hand-ventilating Jane, who is hypoxic – O2 saturations 85% - and hypotensive – BP 75/50 mmHg.

The registrar and nurse are with the patient and you have been called to assist.

Please interpret this arterial blood gas result (FiO2 100%)


(After an initial period of slightly embarrassed simulation, this turned into a discussion of mechanical ventilation strategies for asthma. The gas was never part of this viva; it has been introduced so that the solitary viva coordinator is able to do a session on their own. Also, Jane was initially 32 yars old. The age was modified to turn this into a COPD discussion)

Gas interpretation:

  • Mild acidaemia
  • Severe hypoxia (A-a gradient 566; P/F ratio is 64)
  • Metabolic alkalosis
  • Respiratory acidosis (expected CO2 is around 49)
  • Hyponatremia
What are the possible explanations for these findings?
  • Acidaemia - probably due to the respiratory acidosis
  • Severe hypoxia (A-a gradient 566; P/F ratio is 64) - 
    • Differentials are broad: pneumonia, aspiration, PE, pulmonary oedema
  • Metabolic alkalosis
    • Chronic adaptation to hypercapnea
    • Diuretic therapy
  • Respiratory acidosis (expected CO2 is around 49)
    • Tiring 
  • Hyponatremia
    • Diuretic therapy (classically, a thiazide or a loop diuretic)
Describe how you would you assess the patient.

ABCDE approach may be attempted here. An appropriate series of steps:

Immediate assessment:

A) Make sure the ETT is in correct position by auscultating the chest

B) Ensure the manual resuscitator bag is connected to wall oxygen and the reservor is inflating well

C) Assess the cardiovascular system quickly by physical examination, looking for signs of heart failure

D) Review the recently administered medications.

Some collateral history would be useful from bystanders, and background history from the notes.

 ~

Jane has a lot of wheeze on auscultation and has decreased left-sided air entry with coarse creps bilaterally. The registrar has set up the ventilator.
The observations and monitored waveforms are as you see here:

 ~

What changes would you make to her management?

The main issues are with the ventilator:

  • Decrease PEEP (to nil, potentially)
  • Decrease respiratory rate
  • Decrease the I:E ratio
  • Decrease the inspiratory rise time (i.e. make it more "steep"
  • Aim for a tidal volume of 5-6ml/kg

Also: because of the evidence of bronchospasm, one might want to start her on corticosteroids.

What further investigations would you like to perform?
  • ABG
  • EUC / CMP / FBC / CRP /BNP
  • Chest Xray - looking for pneumonia
  • Transthoracic echo - to assess the contribution from heart failure
  • Blood/sputum cultures
  • Urinary pneumococcal and legionella antigens
  • Atypical pneumonia serology
The family offer some background history. They tell you Jane has "smoker's chronic lung disease".  How would you assess the severity of this?

Historical features:

  • exercise tolerance
  • breathlessness with everyday activities
  • presence of chronic cough
  • high volume of sputum, suggestive of bronchiectasis
  • haemoptysis, suggestive of malignancy
  • home O2 requirement
  • home CPAP requirement
  • pattern of bronchodilator use
  • pattern of steroid use
  • frequency of hospitalisations
  • previous mechanical ventilation
  • anorexia and weight loss

Examination:

  • features of malnutrition
  • features of obesity (sedentary lifestyle)
  • features of chronic steroid use
  • central cyanosis
  • breathlessness at rest
  • hyperexpanded chest
  • degree of air entry
  • signs of right heart failure
The family asked you whether Jane has "a good chance". What indices are you aware of to help predict mortality in COPD?

Parameters such as the BODE index can be used:

Variable

Points on the BODE index
0 1 2 3
FEV1 (% of predicted) >65% 50-64% 36-49% <35%
Distance walked in 6 minutes <350 250-350 150-249 <149
MMRC dyspnoea scale 0-1 2 3 4
Body mass index (BMI) >21 <21    

- Among the most severe group, there is a 50% mortality at 36 months.

Another is the MMRC breathlessness scale,  a subjective report of how breathless the patient feels; 0 is "doin fine" and 4 is "can't leave the house".

The family inform you that Jane had fevers before coming to hospital. How does this alter your investigations or management?
  • Streptococcus pneumoniae and Haemophilus influenzae account for 80% of the pathogens. The rest are atypicals and viruses, such as Moraxella,Mycoplasma pneumoniaePseudomonas, RSV, adenovirus, influenza and parainfluenza. There may or may not be an actual pneumonia (the left side of the chest was quiet)
  • Antibiotics may benefit as this may be an infective exacerbation
Apart from antibiotics, what will your non-ventilator management consist of for the following days?
  • Bronchodilators (salbutamil and anticholinergics)
  • Methylxanthines
  • Steroids
  • Antibiotics
  • Management of any underlying heart failure

Disclaimer: the viva stem above is the original CICM stem, acquired from their publicly available past papers. However, because the college do not make the rest of the viva text or marking criteria available, the rest has been confabulated. It sounds like a plausible viva and it can be used for the purpose of practice, but all should be aware that it does not represent the "true" canonical CICM viva station. 

 

References

An excellent resource for this topic is the chapter on COPD in Oh's manual (ch 26) by Matthew T Naughton and David V Tuxen.

The use of BNP to differentiate between COPD exacerbations and CCF exacerbations:

Morrison, L. Katherine, et al. "Utility of a rapid B-natriuretic peptide assay in differentiating congestive heart failure from lung disease in patients presenting with dyspnea." Journal of the American College of Cardiology 39.2 (2002): 202-209.

Kim, V; Benditt, JO; Wise, RA; Sharafkhaneh, A (2008). "Oxygen therapy in chronic obstructive pulmonary disease"Proceedings of the American Thoracic Society 5 (4): 513–8

Salpeter SE, Buckley NS, Salpeter EE. Anticholinergics but not beta agonists reduce severe exacerbations and
respiratory mortality in COPD
. J Gen Int Med 2006; 21 : 1011–19.

Guyatt GH, Townsend M, Pugsley SO et al . Bronchodilators in chronic airflow limitation. Effects on airway function, exercise capacity, and quality of life. Am Rev Respir Dis 1987; 135 : 1069–74.

Pauwels RA, Buist AS, Ma P et al. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. NHLBI/WHO global initiative for chronic obstructive lung disease (GOLD) workshop summary. Am J Respir Crit Care Med 2001; 163 : 1256–76. - the link is to the updated Feb 2013 document.

Plant P, Owen J, Elliott M. Early use of noninvasive ventilation for acute exacerbations of chronic obstructive pulmonary disease on general respiratory wards: a multicentre randomised controlled trial. Lancet 2000;
355 : 1931–5.

Ram FSF, Picot J, Lightowler J, Wedzicha JA. Non-invasive positive pressure ventilation for treatment of respiratory failure due to exacerbations of chronic obstructive pulmonary disease.Cochrane Database of Systematic Reviews 2004, Issue 3.

Menzies R, Gibbons W, Goldberg P. Determinants of weaning and survival among patients with COPD who require mechanical ventilation for acute respiratory failure. Chest 1989; 95: 398–405.

Connors A, McCaf free D, Gray B. Effect of inspiratory flow rate on gas exchange during mechanical ventilation. Am Rev Respir Dis 1981; 124 : 537–43.

Burns KEA, Adhikari NKJ, Keenan SP, Meade MO. Noninvasive positive pressure ventilation as a weaning strategy for intubated adults with respiratory failure. Cochrane Database of Systematic Reviews 2010, Issue 8. Art. No.: CD004127. DOI: 10.1002/14651858.CD004127.pub2.

Hajizadeh, Negin, Keith Goldfeld, and Kristina Crothers. "Audit, research and guideline update: What happens to patients with COPD with long-term oxygen treatment who receive mechanical ventilation for COPD exacerbation? A 1-year retrospective follow-up study." Thorax 70.3 (2015): 294.

Siafakas, N. M., et al. "Optimal assessment and management of chronic obstructive pulmonary disease (COPD)." European Respiratory Journal 8.8 (1995): 1398-1420.

Celli, Bartolome R., et al. "The body-mass index, airflow obstruction, dyspnea, and exercise capacity index in chronic obstructive pulmonary disease." New England Journal of Medicine 350.10 (2004): 1005-1012.

Stenton, Chris. "The MRC breathlessness scale." Occupational Medicine 58.3 (2008): 226-227.