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These changes combined can lead to: decreased
chest wall compliance, decreased elastic recoil of the lungs associated with a decreased vital capacity and functional residual capacity, increased predisposition for atelectasis while under anesthesia, reduced efficiency for expiration and gas exchange impairment. All those changes combined can lead to hypoxemia. At the same time, the thermoregulatory center of geriatric patients
is weakened and therefore they are more susceptible to anesthesia-induced hypothermia. Hypothermia can be associated with bradyarrythmias, reduced minimum alveolar concentration of inhalants and shivering. Shivering can increase oxygen consumption by 400% also leading to hypoxemia. So, warm them up!
2-Provide cardiovascular monitoring and support!
The possible cardiopulmonary disease is always a possibility for the geriatric patient. Anesthesia can induce cardiovascular depression and hypotension. That is not a good combination! Therefore, close cardiovascular monitoring is detrimental to recognize the possible cardiovascular change as early as possible. The most common physiologic changes in the cardiovascular system of geriatric animals are: â baroreceptor activity, â circulation time, â blood volume, hypotension, âcardiac output and limited renal, hepatic and CNS ability to adapt to hypotension. Most of these common changes in the geriatric heart are primary related to myocardial fibrosis, valvular fibro calcification and ventricular thickening. Cardiac conduction system can also get compromised with age, leading to possible cardiac arrhythmias. Therefore, drugs known as negative inotropes and arrhythmogenics should be avoided in the geriatric patient.
Also, be careful with fluids! It is fundamental to ensure adequate venous return and fluid balance to minimize the risk of anesthesia related hypotension. However, due to the decreased cardiac reserve, fluid overload can lead to congestive heart failure and pulmonary edema. Therefore, fluid rate should be prescribed based on the individual need, hydration and physical status. So, lets use that multi-parametric monitor!
3-Use low does and/or short acting, reversible drugs! With age, the hepatic, neurological and renal functions deteriorate. All those possible changes can lead to
a prolongation of the drug elimination and possible exacerbation of the drug effects on the CNS. Older dogs and cats commonly experience decreased liver mass and hepatic blood flow secondary to reduced cardiac output. Decreased microsomal enzyme activity, and generalized reduction of metabolic activity are also common. These changes are associated with hypoproteinemia, coagulopaties and hypoglycemia. For all the geriatric patients, liver function analysis
and coagulation should be requested prior to the beginning of anesthesia or sedation, especially if highly
metabolized drugs are used. Hypotension should be avoided during anesthesia of geriatric patients since
it leads to a further decrease in hepatic blood flow, exacerbating the possible ischemic hepatic damage that is already present and associated with advanced age. The aged patient may have also compromised cognitive, sensory, motor and autonomic functions and that is usually correlated with decreased requirement for anesthetic drugs (inhalants, benzodiazepines, opioids, barbiturates) and prolonged recovery time.
Other possible problems commonly observed in elderly dogs and cats are: chronic kidney disease, urinary incontinence, bladder tumors and prostate problems. Those changes are associated with decreased renal mass, tubular size, weight and glomerular numbers leading to a reduced filtration function. Reabsorption
of protein, water and sodium, secretion of aldosterone, secretion and reabsorption of anionic and cationic compounds, formation of vitamin D, renin and elimination and metabolism of protein-bound compounds are all compromised. That can influence the regulation of
blood pressure, acid-base, erythropoietin, resulting
in hyperphosphatemia, azotemia dehydration and hypoproteinemia. Now, general anesthesia can lead
to a 40% reduction in renal blood flow and glomerular filtration. That is not a good combination! Now, that can be worse if cardiac output is already compromised by any cardiac disease. Consequently, the effects
of anesthesia on the kidney can be exacerbated in geriatric patients with pre-existing cardiovascular or renal condition. Hypoxemia, hypovolemia, hypotension, and hypercarbia are factors that contribute to renal failure following anesthesia and should be avoided to decrease the chances of worsening organ dysfunction. These factors reinforce the justification for close cardio- respiratory monitoring of older pets under general anesthesia since early recognition and treatment are key to prevent further compromise of the kidney disease.
4-Pay attention to the patient’s history! Hyperadrenocorticism, diabetes mellitus and hypothyroidism are common conditions in the geriatric patient. Older patients may have decreased adrenal responsiveness to ACTH stimulation when compared with younger dogs. It has been suggested that corticosteroid supplementation in the pre-anesthetic period may be beneficial for the geriatric animal because of the possibility of adrenal exhaustion in response to stress of anesthesia and surgery. So, knowing the patient history, understanding the physiology of the possible co-existing disease and working hard the stabilize the patient prior to the anesthesia induction will ensure a higher survival rate!
5- Anesthesia recovery is even more important in geriatric patients! The anesthetist should be ready to provide oxygen, heat and continuous cardio-respiratory
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