With advancing age, patients tend to have more comorbid illnesses and disability, increasing the risks of adverse events and adverse drug reactions.

 

Frailty

HOMEOSTASIS: Maintaining homeostasis is a dynamic, active process. Frailty is when physiologic reserves are maxed out just for homeostasis, with any challenge breaching the threshold, increasing severity of illness which will affect patient outcomes.

HOMEOSTENOSIS: the concept that aging shrinks physiologic reserves that are available to meet challenges to homeostasis, and this causes an increase in vulnerability to disease. Physiologic reserves likely are already being consumed in the challenges encountered by age. The final outcome is the frailty seen in the elderly, where even the smallest challenge could overwhelm the available reserves and results in disaster.

 

Fluid Resuscitation in the Elderly

The prevalence of hypertension in adults older than 60-65 is 70-80%.

Patients with chronic hypertension may have higher blood pressure value needs to achieve the same level of end-organ perfusion than other patients.

That is, their physiology may be adapted to the higher blood pressures.

► A return to a "normal" blood pressure can be harmful.

At its worst, such adaptation may cause geriatric patients to go into shock with a blood pressure even above 100 systolic. Furthermore, modest amounts of blood loss in geriatric patients may lead to shock due to reduced blood volume and/or possible anemia in such an adaptive state.

Geriatric patients may be less able to tolerate excessive fluids due to possible anemia or possible electrolyte alterations in which hemodilution may worsen these condition by fluid overload. Fluid overload may also cause pulmonary edema (dyspnea, rales, rhonchi) which the elderly are at an age-related disadvantage to tolerate. 

 

Pharmacokinetic Changes

Physiological changes that impact pharmacokinetics may include a decrease in the amount of body water, decrease in muscle mass, increase in body fat, renal function deterioration, liver function deterioration, and altered distribution of drugs.

Implications of altered pharmacokinetics may include

• increased drug sensitivity,
• increased adverse drug reactions,
• increased drug toxicity, and
• dosages that should probably be decreased.

Kidney function declines with age and the elderly are more prone to nephrotoxicity related to medications.

Difficulty in compliance of drug therapy may be due to lack of money to purchase the drugs, a complicated drug regimen, forgetfulness (“Did I take it or not?”), difficulty opening containers, directions for use not understood, and other problems.

 

Immune System Dysfunction in the Elderly

IMMUNOSENESCENCE: changes that occur in the immune system with age.

As people age, so does the immune system and its capabilities decline, creating more susceptibility to infections and cancer, along with an increased incidence of autoimmune disorders.

• Decreases in immune functions with aging are among the most critical changes, leading to more infections, malignancies, and autoimmune disorders. Immunosenescence alters the inflammatory processes, creating a chronic, low-level inflammatory state.

Pneumonia and influenza are among the top 10 causes of death in those > 65.

• Anatomical and physiological changes in the elderly can impact the pathophysiology of their illnesses because of immunological changes, such as the aging of the thymus and reduction of T-cells, reduced leukocyte activity, and increased production of autoantibodies.
   
• The changes in the immunological system of the elderly make them more prone to infections and exacerbations of chronic disease processes. These infections are compounded by an aging of the hypothalamus and may not produce a fever in the face of an immunological insult such as a viral, bacterial, or occult infection.

SECONDARY IMMUNOSUPPRESSION: Because of age-related conditions such as osteoarthritis, the elderly are more likely to experience secondary immunodeficiency from drugs used for these, such as steroids. Those with rheumatoid arthritis and other autoimmune syndromes may be on immunosuppressive "biologicals" for their control, benefitting their condition but which also increases their risk of infections and cancers.