(1) Advancing age is not in itself a contraindication to general anaesthesia or major surgery.
(2) Preoperative screening of old patients for the presence of subdisease or impaired organ function is necessary before anaesthesia or surgery.
(3) Anaesthetic doses should be based on lean body weight not actual body weight if the animal is obese.
(4) Generally, anaesthetic and other drug doses need to be reduced in ageing patients.
(5) Attempts must be made to avoid the development of hypothermia and hypotension during anaesthesia of old patients.
(6) Reduce exposure to known risk factors for acute organ failure, especially acute renal failure.
Objectives of surgery in old patients
The objective of performing surgery in geriatric patients is to prolong active, enjoyable life and procedures that offer no benefits to the patient should be avoided. However, a policy of avoiding all ‘high risk’ surgery would deny some patients with responsive conditions the benefits of surgical treatment.
The decision to perform elective surgery on old patients has to be a clinical judgement following full discussion with the owner. Owners should be made aware that older patients generally need preoperative screening, take longer to recover, require more post-surgical nursing, and may need careful (sometimes expensive) monitoring.
Ageing changes affecting the liver, kidneys, and the cardiovascular and respiratory systems are of major importance in anaesthesia. To maximise the benefits of any surgical procedure the physiological, pharmacological and pathological changes commonly seen in older animals need to be understood by both the surgeon and the anaesthetist.
A substantial proportion of surgery is performed in older animals, for example for the removal of tumours, and advancing age is not in itself a contraindication to major surgery or to the administration of a general anaesthetic. However, it is important to assess the elderly patient fully before surgery because they frequently have multiple organ system disease necessitating modifications in technique. Postoperative support is also very important, and mortality and morbidity may be higher if pre- and post-surgical risk factors are not managed properly.
Many old animals are kept on long-term treatments such as non-steroidal anti-inflammatory drugs (NSAIDS), corticosteroids, diuretics, cardiac stiulants and anticonvulsants. A pre-surgical review of medications is important because they may affect anaesthesia.
Phenytoin and primidone are potentially hepatotoxic when they interwith anaesthetic agents and they also cause CNS depression, so reducing the dose of anaesthetic needed.
Chronic glucocorticoid administration may induce adrenal insufficiency predisposing to cardiac instability during anaesthesia. This is another reason why glucocorticoid administration immediately before induction of anaesthesia has been advocated.
Long-term diuretic administration may cause metabolic alkalosis, hypokalaemia, and sometimes hypomagnesaemia – all of which should be corrected before surgery.
It is important to review the presenting history in detail, perform a comphysical examination and perform laboratory screening tests of geriatric animals for signs of subclinical disease or impaired organ function.
The author advocates the following as a minimum pre-surgery screening programme for geriatric patients:
- (1) complete blood count and differential
- (2) haematocrit
- (3) total serum protein
- (4) serum urea
- (5) serum creatinine
- (6) serum electrolytes (sodium, potassium, chlorine and calcium)
- (7) blood glucose
- (8) serum bile acids
- (9) ECG examination
- (10) urinalysis – protein, pH, glucose and sediment.
In an ideal situation the following would also be included in a geriatric screen:
- (1) T4
- (2) serum ALT, AP
- (3) survey chest and abdominal radiographs
- (4) arterial and venous blood gas analysis
- (5) systolic and diastolic blood pressure measurement.
It is important to review recent medications and existing diagnostic information such as previous radiographs, or laboratory data.
Local or regional anaesthesia may be safer than general anaesthesia in severely debilitated animals. Sedation is usually required, and perineural injection, field block, surface analgesia, intravenous regional analgesia or epidural and spinal injections can be used. Identification of anatomical landmarks may be difficult in obese subjects.
Epidural anaesthesia is a useful procedure when the anaesthetic is injected at the lumbosacral junction but cranial epidural should be avoided because sympathetic fibres may be blocked causing hypotension.
Acupuncture has been recommended as a method of providing analgesia for minor procedures in ‘high risk’ geriatric veterinary patients ().
With increasing age skin loses its elasticity and vascularity making it vulnerable to trauma and it bruises easily. Gentle handling during surgery is therefore advisable.
Wound healing may be delayed in older patients, and there may be a reduction or delayed response in the formation of granulation tissue. Wounds in older patients may also be more susceptible to infection and patients with evidence of systemic infection, renal disease, hepatic disease, cardiovascular disease or endocrine disorders are likely to exhibit delayed wound healing.
Hypoproteinaemia will adversely affect wound healing by impairing fibroplasia, neovascularisation, remodelling and tensile strength so prolonging the healing phase. Maintaining a positive protein-energy balin patients before elective surgery and during the postoperative recovery period is an important therapeutic objective which might necessitate special feeding techniques in some individuals.
Haemostasis needs to be vigilant during surgery because local blood losses may seem small if the patient has transient hypotension but could result in significant postoperative haemorrhage following recovery. Haemorrhage at wound sites is a major risk factor for the development of infection or dehiscence.
Advancing age, prolonged anaesthesia and surgery time, hypotension, obesity, some therapeutic agents and the presence of concurrent disease may all increase the risk of wound infection. The presence of gross obesity may delay return to normal mobility.
Selections from the book: Mike Davies “Canine and Feline Geriatrics”, 1996.