الفهرس 
Physiological changes with agingOnly 14 pages are availabe for public view
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Abstract
The elderly patients presenting for orthopedic surgeries represent a challenge to the anesthesia practitioner. Patients may be sicker than one would presume from their clinical presentation. Compensation for age-related changes is usually adequate, but limitation of physiological reserve is evident during times of stress such as the perioperative period.
Physiological changes occur with aging in all organ systems. The cardiac output decreases, blood pressure increases and arteriosclerosis develops. The lungs show impaired gas exchange, a decrease in vital capacity and slower expiratory flow rates. The creatinine clearance decreases with age although the serum creatinine level remains relatively constant due to a proportionate age-related decrease in creatinine production. Functional changes, largely related to altered hepatic drug metabolism are common in the elderly. Progressive elevation of blood glucose occurs with age on a multifactorial basis and osteoporosis is frequently seen due to a linear decline in bone mass after the fourth decade. Lean body mass declines with age and this is primarily due to loss and atrophy of muscle cells. Degenerative changes occur in many joints and this, combined with the loss of muscle mass, inhibits elderly patients’ locomotion. These changes with age have important practical implications for the clinical management of elderly patients: metabolism is altered, changes in response to commonly used drugs make different drug dosages necessary and there is need for rational preventive programs of diet and exercise in an effort to delay or reverse some of these changes.
Preparation to lower the risk of complications and improve outcomes during and after procedures requiring anesthesia is very important. Traditionally surgical risk has been considered more important than the anesthetic risk. The risk from anesthesia is more related with the presence of co-existing diseases than with the age of the patient. Thus, it is more important to determine the patient’s status and estimate the physiologic reserve in the preanesthetic evaluation. If the condition can be optimized before surgery this should be done without delay, because long delays increase the rate of morbidity.
Diabetes mellitus and cardiovascular diseases are very common among geriatric patients. Pulmonary complications are one of the leading causes of postoperative morbidity in elderly patients. Pulmonary optimization is needed for these patients. Laboratory and diagnostic studies, the history and physical examination are of great importance. More issues that must be always in mind in a geriatric patient is the significant possibility of depression, malnutrition, immobility and dehydration. It is important to determine the cognitive status of an elderly patient.
Advancing age is not a contradiction for either general or regional anesthesia. Some aspects of regional anesthesia may provide benefit for the patient. It affects the coagulation system by preventing postoperative inhibition of fibrinolysis. Furthermore, it decreases the incidence of deep vein thrombosis after total hip arthroplasty. The use of peripheral blocks in the elderly promises favorable outcomes without compromising the safety of the airway or risking major hemodynamic effects. However, it should always be kept in mind that there are some anatomic changes in geriatric patients and that peripheral blocks have shown to last longer in these cases. The hemodynamic effects of regional anesthesia may be associated with reduced blood loss in pelvic and lower extremity operations. More important, the patient maintains his airway and pulmonary function.
Advanced age and general anesthesia are associated with hypothermia. Maintenance of normothermia is important as hypothermia is related to myocardial ischemia and hypoxemia in the early postoperative period. In case of general anesthesia it is of major importance to titrate drug doses and it would be prudent to use short-acting drugs. The optimal physiological management is required to produce the best surgical outcome.
Post-operative care for geriatric patients involves four basic principles, namely the postoperative visit, post-operative analgesic regimen, fluid and oxygen therapy and post-operative placement of the patient. Fluid prescription post-operatively will depend upon the nature of the procedure performed, the expected ongoing losses and the expected period that oral intake will be limited. Oxygen prescription also depends on the nature of the procedure and the pre-existing medical condition of the patient. Analgesic regimens will be tailored to the type of surgery and physical status of the patient. Elderly patients can be safely given a PCA device on the ward, but should only receive one if they have the understanding and dexterity to use it. Age should not be a discriminator to admission to the ICU. Indeed if it is felt that major surgery will be of benefit to the patient then it seems perverse to deny them appropriate post-operative care.
Complication rates and morbidity following anesthesia are increased in the elderly. Awareness of complication development is the first step in risk reduction. Complications can occur at various periods in the recovery phase. Examples of these complications include: postoperative nausea and vomiting (PONV), respiratory complications such as aspiration, postoperative lung atelectasis& pneumonia, cardiac complications such as myocardial infarction, arrhythmias &heart failure, deep venous thrombosis (DVT), neurological complications such as cognitive dysfunction and delirium. With an active management program, good results can be obtained in these patients even in the very old.