Critical care - Age-related changes: Nursing

Normal age related physiologic changes occur gradually over time resulting in a decrease in reserved capacity, which is the functional ability of the bodys organs to function beyond whats needed for normal day to day activities.

These changes can decrease the ability of the critically ill older adult to adapt to illness, which can increase the risk of complications.

As the nurse, you'll recognize these age related changes and consider complications that can develop in your critically ill older adult patient.

As a result, starting with the cardiovascular system, there's an age related tendency for a decrease in the number of contractile cells in the heart called cardiomyocytes along with an accumulation of collagen and fibrosis.

The cardiomyocytes also tend to hypertrophy or increase in size resulting in a slight thickening of the left ventricular wall with no significant change in size of the left ventricular cavity.

There are also alterations with calcium signaling within the myocardium during contraction, leading to delayed relaxation during diastole and prolonged contraction during systole together.

These changes can make the heart a less efficient pump leading to reduced cardiac output. Additionally, a loss of cells in the sino atrial node which is responsible for generating impulses that stimulate a heartbeat is associated with a reduced maximal heart rate, which is the highest number of times the heart can beat per minute during physical activity.

These age related changes reduce cardiac functional reserve, impairing the heart's ability to meet increased demands that can occur during a critical illness.

Other age related vascular changes include dysfunction of the endothelial cells, lining blood vessels. These cells become less effective in balancing substances that cause vasodilation and vasoconstriction.

As a result, arteries tend to stiffen blood flow decreases and there's an increased risk of atherosclerosis and thrombosis arterial wall stiffness also contributes to increased afterload and an increase in systolic BP.

Lastly, an impaired barrow reflex which helps maintain BP during position changes can result in orthostatic hypotension and an increased risk of falls moving on to the pulmonary system.

The overall work of breathing increases as an individual ages making it more difficult to meet increased oxygen demands.

The size of the thoracic cavity tends to decrease due to loss of intervertebral disc height and narrowed rib spaces which can limit the available space for the lungs to expand.

Also, ribcage cartilage begins to calcify, contributing to stiffening of the chest wall and decreasing its compliance or its ability to expand as lungs fill with air.

Additionally, the primary muscles of respiration, the diaphragm and intercostal muscles decrease in strength. So older patients may require the use of accessory muscles like the sternocleidomastoid scalene and trapezius muscles when respiratory demands are increased.

Other changes include diminished elastic recoil in the lungs, leading to alveolar distension, a decreased ability to move air out of the lungs and an increased residual volume or the amount of air remaining in the lungs.

After exhalation. On top of that, a decreased alveolar surface area and reduced capillary blood volume can limit gas exchange leading to a decrease in the partial pressure of oxygen or Pao two in the blood and hypoxemia.

Lastly, the cough reflex diminishes and mucociliary clearance is reduced. So, the older individual's ability to clear respiratory secretions becomes less effective.

Increasing the risk for aspiration and respiratory infections like pneumonia. Next up are renal changes that contribute to an overall reduction in renal function, which can increase the risk of acute kidney injury during a critical illness.

These changes involve a decrease in kidney mass and a reduced number of nephrons which are the functional units of the kidneys.

Also, blood vessel thickening decreases the amount of blood flow to the kidneys and the glomerular filtration rate or GFR, which measures the amount of blood filtered by the kidneys each minute is reduced.

These changes lead to a decrease in creatinine clearance, which is how much creatinine a byproduct of protein metabolism is removed from the blood in the kidney tubules.

There's a decrease in mitochondrial energy production that's needed for active transport across cell membranes. This impairs the kidneys ability to reabsorb substances back into the blood like glucose and protein which can lead to glycosuria and proteinuria.

The older adult is also predisposed to fluid imbalance and dehydration factors that contribute to this are a decreased ability to retain sodium.

A diminished sensitivity to vasopressin or antidiuretic hormone and an overall tendency to produce a more dilute urine. On top of that thirst perception is typically impaired leading to a reduced intake of water.

Finally, there's an age related reduction in renin production which leads to decreased aldosterone and an impairment of the renin angiotensin aldosterone system.

All right. Last up are neurocognitive changes which make functions like processing sensory input, problem solving and recalling recent events more difficult.

Also cerebral bloodflow diminishes with age which impairs cerebral perfusion and slows processing speed. Other age related changes include a decrease in certain neurotransmitters such as acetylcholine, dopamine, serotonin and glutamate that contribute to impaired cognition, alterations in motor function and dysregulation of sleep wake cycles.

There's also an increase in the permeability of the blood brain barrier which elevates the risk of neuroinflammation during a critical illness.

These changes diminish the brains homeostatic reserve, which when coupled with stressors, like those involved in a critical illness, increases the risk for acute brain dysfunction, also known as delirium characterized by a rapid onset of fluctuating alterations in consciousness that involve a decreased environmental awareness, disorientation and perceptual disturbances such as hallucinations.

All right, as a quick recap, normal age related physiologic changes occur gradually over time resulting in a decrease in reserve capacity, which is the functional ability of the body's organs to function beyond what's needed for normal day to day activities.

These changes can decrease the ability of a critically ill older adult to adapt to an illness, which can increase the risk of complications.

As the nurse youll recognize these changes and consider complications that can develop in your critically ill older adult patient as a result.