What are the age related factors which adversely affect outcome in the elderly (>65 years) critically ill patient?
CVS: High prevalence of cardiac disease, CAD, silent ischemia, less responsive to symathetic stimulation and therefore lesser response to catecholamines, greater diastolic dysfunction and conducting system disease, likelihood of being on cardiac drugs. ( 3 marks)
RS: Swallow dysfunction- risk of aspiration
Decreased ventilatory response to hypoxia and hypercapnia
Decreased chest wall complance, muscle strength and increase in closing volume.
Renal: Decrease in renal function, lower muscle mass so a serum creatinine at the upper end of normal may indicate renal failure
Metabolic: Reduced BMR, risk of overfeeding
CNS: Higher incidence of delirium, age related loss of cerebral volume
Drug dosing: Altered pharmacokinetics, reduced renal and hepatic reserve, need dose adjustment, increased sensitivity to sedation and analgesia
Greater operative morbidity and mortality
This question closely resembles a part of Question 9 from the first paper of 2012. To simplify revision, parts of that answer are reproduced below. However, the college answer does not seem to answer the college question. The question asked for age related factors which adversely affect outcome ; the college answer instead went on to discuss age-related changes in physiology, and how these influence intensive care management.
Let us talk about the outcomes first.
Influence of age:
- Mechanical ventilation : in-hospital mortality among octogenarians = 70%
- If the reason for ventilation was pneumonia, in-hospital mortality for the over-65s = 62%
- In hospital mortality for octogenarians admitted with sepsis = 85%
- In brain injury, risk of death or disability is doubled in the elderly.
Influence of functional status and co-morbidities:
- Functional dependence: in-hospital mortality = 30% (vs. 7.8% if independent)
- Dementia: mortality = 55.9% versus 8.2% in those without cognitive impairment.
- Delirium: independent predictor of reintubation, prolonged hospital stay and mortality.
- Malnutrition: low BMI increases mortality in the elderly.
Expected functional outcome:
- Only 14% of patients aged 85 years or older went home without home health care.
- After discharge, mortality occurred predominantly during the first 3 months. If you survive ninety days, you're probably going to be ok.
- Many elderly patients do not want intensive care. "In a population of patients with limited life expectancy and aged 60 years or older, 74% stated that they would not choose treatment if the burden of treatment were high and the anticipated outcome survival with severe functional impairment".
Now; how does old age influence intensive care management?
- Intubation may be easier due to the patient being edentulous
- Intubation may be more difficult due to C-spine and TMJ arthritis
- Bag-mask ventilation may be more difficult because of missing teeth and wasting of facial soft tissues
- Swallowing may be impaired and aspiration is more likely
- Mechanisms maintaining airway patency are impaired, and extubation failure is more likely
- Greater risk of post-induction cardiovascular collapse
- Decrease in expectations: SpO2 goals may be lowered (~ 92%, due to "senile emphysema")
- Chest physiotherapy becomes more important (decreased respiratory muscle strength)
- Early extubation is favoured (to prevent deconditioning)
- There is decreased sensitivity of respiratory centres to hypoxia and hypercapnia, which must be considered.
- Responsiveness to β-adrenergic receptor stimulation is decreased; higher doses of vasopressors may be required
- Baroreceptors and chemoreceptors are less reactive
- Levels of circulating catecholamines are increased
- An increased blood pressure goal is therefore appropriate when titrating vasopressors: chronic hypertension is almost assured, and with this, organ bloodflow autoregulation is impaired (i.e. more closely tied to pressure).
- Increased risk of delirium (therefore, greater vigilance in screening for delirium)
- Decreased expectation of neurological performance, eg. when assessing for extubation (pre-existing dementia)
- Parkinson disease (unusual response to antidopaminergic drugs)
- Pre-existing weakness may produce a "difficult to wean" scenario
Changes in approach to the support of renal function
- Age-related decrease in GFR is to be expected
- Renal blood flow decreases; the kidneys are more susceptible to fluctuations of blood pressure
- Renal blood flow autoregulation undegoes a left-shift; thus a higher perfusion pressure may be required (eg. a MAP of 75-80)
- Because of these factors, old kidneys are more susceptible to dialysis-associated renal dysfunction. This influences the decision as to whether one does or does not offer dialysis.
Changes in approach to nutrition
- Albumin is expected to be low (due to age-related decrease in albumin synthesis)
- Decreased glycogen reserve means greater vigilance in monitoring for hypoglycaemia
- Decreased metabolic rate means nutritional requirements may be lower than predicted by crude approximations of caloric requirements
- Likelihood of premorbid malnutrition is greater - thus, more susceptible to refeeding syndrome
Changes in approach to blood transfusion
- Age-related hanges in haematological function influence your expectations: these patients are more likely to be chronically anaemic, and well adapted to anaemia.
- Decreased marrow cellularity results in a diminished response to anaemia and EPO.
- Chronic anaemia of malnutrition may pre-date ICU admission
Changes in interpetation of the clinical features of sepsis
- There is diminished immune response, both cellular and humoural.
- The elderly may not mount a febrile response, and may actually be hypothermic with sepsis
- Decreased synthetic function of the liver may result in diminished synthesis of CRP
Changes in pharmacology
- Drug levels may not represent the effective "free" fraction due to changed in protein binding and volume of distribution
- Dose adjustments need to be made to accoun
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Muschler, George F., et al. "Age‐and gender‐related changes in the cellularity of human bone marrow and the prevalence of osteoblastic progenitors." Journal of Orthopaedic Research 19.1 (2001): 117-125.
Grady, C. L., et al. "Age-related changes in brain activity across the adult lifespan."Cognitive Neuroscience, Journal of 18.2 (2006): 227-241.
de Rooij, Sophia E., et al. "Factors that predict outcome of intensive care treatment in very elderly patients: a review." Critical Care 9.4 (2005): R307.