You are asked to review an 88-year-old man who has fallen from a ladder. He is in the ED with a large subdural haematoma (SDH) and significant mid-line shift on CT scan. His GCS is 6/15. He has a past medical history that includes atrial fibrillation (treated with warfarin and digoxin), chronic renal impairment (creatinine 190 µmol/L), non-insulin-dependent diabetes and mild cognitive impairment.

a) List the factors in this patient’s history that suggest his outcome may be poor?

b) Outline how age-related changes in cardio-respiratory physiology and response to medications would impact on the management of this patient

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College Answer

  • Factors predictive of poor outcome:
    • Severe TBI in an elderly patient
    • SDH increased risk of poor outcome
    • Warfarin therapy
    • Pre-existing co-morbidities – renal disease, diabetes, neurological dysfunction

Age-related changes:

  • Cardiovascular
    • Increased incidence of coronary artery disease
    • Systolic and diastolic dysfunction with CCF
    • Conduction disorders (SSS, AF, BBB)
    • Valvular disease
    • Decreased response to sympathetic stimulation
  • Respiratory
    • Decreased respiratory muscle strength
    • Decreased respiratory centre sensitivity to hypoxia and hypercarbia
    • Reduced elastic recoil of lung
    • Increased chest wall stiffness
    • Reduced vital capacity and FEV1.

Response to medications

  • Age has been shown in multiple studies to be an independent risk factor for adverse drug reactions.
  • Age related physiological changes affect absorption, distribution, metabolism and elimination of drugs.
  • Poly-pharmacy is common, thus increased risk of adverse drug reaction.
  • Cognitive impairment and drug errors – overdose, non-adherence, failure to disclose full medication list to often multiple medical practitioners involved in care.
  • Reducing renal blood flow and GFR with age alters drug elimination potentially leading to drug accumulation.

Discussion

A more detailed all-systems look at age-related changes in the response to critical illness can be found in Question 8 from the second paper of 2007:"What are the age related factors which adversely affect outcome in the elderly (>65 years) critically ill patient?"

How did the college arrive at this answer?

What are the predictors of poor outcome in traumatic brain injury?

  • Everyone seems to agree that age is a predictor of poor outcome.
  •  Steyerberg et al found that age was associated with poor neurological outcomes and decreased survical. 
  • Amacher et al also found that it doesnt matter how good your GCS is on admission, your old age will still play a role.
  • Being over 60 is a poor prognostic indicator.
  • Steyerberg et al found that a traumatic subarachnoid (rather than subdural) was a determinant of poor prognosis.
  • Mortality in elderly patients with subdural haematoma is very high if they present with a GCS 3-5
  • For these people,  craniotomy may not be justified, because of the extremely poor outcomes overall.

As far as age-related physiological changes go...

From this article on geriatric cardiology, I quote the following physiological changes associated with age:

Cardiovascular changes

  • A decrease in elasticity and an increase in stiffness of the arterial system. Thus:
    • Increased afterload on the left ventricle
    • left ventricular hypertroph
    • Increase in systolic blood pressurey,
    • Changes in the left ventricular wall that prolong relaxation of the left ventricle in diastole; thus diastolic dysfunction and the propensity towards pulmonary oedema
    • Aortic valve calcification
  • Dropout of atrial pacemaker cells resulting in a decrease in intrinsic heart rate.
  • With fibrosis of the cardiac skeleton there is calcification at the base of the aortic valve and damage to the His bundle as it perforates the right fibrous trigone.
  • Decreased responsiveness to β-adrenergic receptor stimulation
  • Decreased reactivity to baroreceptors and chemoreceptors,
  • Increase in the levels of circulating catecholamines.

Respiratory changes

  • Decrease in exchange surface area ("senile emphysema"):
    • Dilatation of alveoli
    • Enlargement of airspaces
    • loss of supporting tissue for peripheral airways
    • Carbon monoxide transfer decreases with age, reflecting mainly a loss of surface area.
  • Decreased static elastic recoil of the lung, thus
    • Increased residual volume
    • Increased functional residual capacity.
  • Decreased expiratory flow rates (especially small airways)
    • The ventilation/perfusion ratio heterogeneity increases, with low V/Q zones appearing as a result of premature closing of dependent airways.
  • Decreased compliance of the chest wall, thus increased work of breathing
  • Decreased respiratory muscle strength (though this depends on the heart, and on nutrition)
  • Decreased sensitivity of respiratory centres to hypoxia and hypercapnia

Pharmacokinetic changes:

  • Reduction in first-pass metabolism, thus increased oral bioavailability of a few drugs.
  • Body fat increases, body water decreases; thus:
    • Hydrophilic drugs have a smaller volume of distribution
    • lipophilic drugs have an increased volume of distribution and a longer half-life
  • Drugs with a high hepatic extraction ratio decrease in systemic clearance
  • Activities of cytochrome P450 enzymes are preserved in normal ageing
  • Renal clearance may be decreased due to age-related changes in renal function

References

References

Langlois, Jean A., Wesley Rutland-Brown, and Marlena M. Wald. "The epidemiology and impact of traumatic brain injury: a brief overview." The Journal of head trauma rehabilitation 21.5 (2006): 375-378.

 

Steyerberg, Ewout W., et al. "Predicting outcome after traumatic brain injury: development and international validation of prognostic scores based on admission characteristics." PLoS medicine 5.8 (2008): e165.

 

Stocchetti, Nino, et al. "Traumatic brain injury in an aging population." Journal of neurotrauma 29.6 (2012): 1119-1125.

 

Amacher, Loren A., and David E. Bybee. "Toleration of head injury by the elderly." Neurosurgery 20.6 (1987): 954-958.

 

Jamjoom, Abdulhakim, et al. "Outcome following surgical evacuation of traumatic intracranial haematomas in the elderly." British journal of neurosurgery 6.1 (1992): 27-32.

 

Cheitlin, Melvin D. "Cardiovascular physiology—changes with aging." The American journal of geriatric cardiology 12.1 (2003): 9-13.

 

Shi, Shaojun, and Ulrich Klotz. "Age-related changes in pharmacokinetics."Current drug metabolism 12.7 (2011): 601-610.

 

Corsonello, A., C. Pedone, and R. Antonelli Incalzi. "Age-related pharmacokinetic and pharmacodynamic changes and related risk of adverse drug reactions." Current medicinal chemistry 17.6 (2010): 571-584.

 

Carbonin, P., et al. "Is age an independent risk factor of adverse drug reactions in hospitalized medical patients?.Journal of the American Geriatrics Society39.11 (1991): 1093-1099.

 

Timiras, Paola S., ed. Physiological basis of aging and geriatrics. CRC Press, 2013.

 

Janssens, J. P., J. C. Pache, and L. P. Nicod. "Physiological changes in respiratory function associated with ageing." European Respiratory Journal 13.1 (1999): 197-205.