![Kate White](/sites/default/files/images/media/image/Scherm%C2%ADafbeelding%202024-03-24%20om%2008.33.11.png)
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Anesthesia of the geriatric patient
Kate White & Flo Hillen
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Anesthetizing the older patient is a daily occurrence in veterinary practice; here the authors review current knowledge and advise on the safest approach to such animals.
Kate White
MA, Vet MB, PhD, DVA, Dip. ECVAA, FRCVS, School of Veterinary Medicine, University of Nottingham, Nottingham, UK
Dr. White graduated from Cambridge University and after a spell in general practice she undertook a residency in anesthesia. She then worked for 10 years as a self-employed consultant in referral practices, pharmaceutical companies, academia, zoos and biomedical research establishments providing anesthesia services. She is past president (2014-2016) of the worldwide Association of Veterinary Anesthetists. Her research interests span numerous aspects of analgesia and anesthesia in many different species, with a particular emphasis on patient safety. She is currently Professor and deputy Head of School at Nottingham Veterinary School.
![Kate White](/sites/default/files/images/media/image/Scherm%C2%ADafbeelding%202024-03-24%20om%2008.33.11.png)
Flo Hillen
B.SocSci, BVMedSci, BVMBVS, PGCHE, FHEA, MRCVS, School of Veterinary Medicine, University of Nottingham, Nottingham, UK
Dr. Hillen graduated from the University of Nottingham in 2016. After several years in small animal practice and a short time in industry she joined the University of Nottingham as a Teaching Associate in anesthesia. She is currently undertaking an ECVAA approved residency in anesthesia and analgesia alongside her undergraduate teaching commitments.
![Flo Hillen](/sites/default/files/images/media/image/Scherm%C2%ADafbeelding%202024-03-24%20om%2008.32.32.png)
Key points
- An increase in the life expectancy of our pet population means that veterinary surgeons are now frequently presented with geriatric patients in need of procedures requiring general anesthesia.
- Although age is not a disease state, changes associated with healthy aging reduce functional organ reserve, meaning that elderly patients are less able to cope with physiological stress.
- Geriatric patients also have an increased incidence of clinical and subclinical disease which may have implications for anesthesia.
- An understanding of how these physiological and pathophysiological changes might affect anesthesia can help the clinician to make decisions which optimize patient comfort and safety.
Introduction
A rise in the life expectancy of our domestic pets, and a change in owners’ attitude towards their healthcare, has resulted in geriatric patients being presented to veterinary practices more commonly than in the past, and they are often admitted for surgical or diagnostic procedures requiring general anesthesia. Geriatric animals are typically defined as those which have reached 75-80% of their expected lifespan, although this should perhaps be interpreted with some caution, as the average lifespan is likely due, at least in part, to breed-specific pathology rather than simply variation in biological aging 1. It is also unlikely that a young animal with life-limiting disease is physiologically similar to an aged patient. In general, animals which appear to be old should probably be considered to be so, and if this is incongruous with their physical age further investigation is warranted.
Healthy aging in both humans and animals is associated with changes which result in a reduction in physiological reserve, and older animals are more likely to be affected by clinical and subclinical disease, all of which have implications for anesthesia. A multicenter retrospective analysis concluded that increasing age was an independent risk factor for perioperative mortality; apparently healthy dogs and cats over 12 years of age were approximately 10 and 2.1 times more likely respectively to die from anesthetic-related complications than their younger counterparts 2. This increased risk is likely the result of greater susceptibility to the effects of anesthetic drugs due to decreased functional reserve, hypothermia, prolonged recovery and an increased incidence of subclinical disease.
Age-related physiological changes
Respiratory system
Within the lungs, the small airways (i.e., less than 2 mm diameter) close at low lung volume, and ventilation to or from alveoli beyond them ceases; in older patients, this closure occurs at higher volumes than in younger animals. Although pulmonary fibrosis and respiratory muscle weakness in older animals results in an increased functional residual capacity (FRC), closing capacity (the maximum volume of air within the lungs at which small airway closure can be detected) also increases with loss of elastic recoil. In time, closing capacity will exceed FRC 3. Atelectasis and resulting ventilation-perfusion (V/Q) mismatch leads to an increased alveolar-arterial (A-a) oxygen gradient and therefore decreased arterial oxygen tension. As a result, geriatric animals are more prone to rapid desaturation and are less able to respond to hypoxia and hypercapnia.
Cardiovascular system
Geriatric patients have less cardiovascular reserve and thus a reduced ability to respond to hypotension. In these patients, blood flow to the organs, including the liver and kidneys, may be reduced, increasing susceptibility to dysfunction in the face of ischemia. In animals without specific cardiovascular pathology, age-related changes include myocardial atrophy and fibrosis, valvular fibrocalcification and ventricular thickening. Involvement of the heart valves may lead to varying degrees of insufficiency, whilst inclusion of the conduction system can predispose patients to the development of arrythmias.
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