Anaesthesia and analgesia for endocrine and renal cases

• CKD and anaesthesia preparation - tests

  Physical exam and detailed history, then complete blood count, serum chemistry profile and urinalysis (minimum USG), SDMA, NIBP

  These tests provide vital information (can reduce patient morbidity and mortality) by indicating drug dose reduction is sensible.
• CKD and anaesthesia preparation - trends and indications

  Mild increases in BUN and creatinine may indicate severe disease.

  Trends are more useful than singular measurements.

  Renal patients may be dehydrated, anaemic, azotaemic, anorexic or acid-base anomalies.

  Azotaemia increases the sensitivity of anaesthetic drugs by affecting the permeability of the blood brain barrier.
• Sedation, premedication and preparation of CKD - overview

  Having data about kidney function prior to choosing and delivering drug dosages can help avoid overdosing a patients and increasing morbidity.

  Some anaesthetic drugs can have deleterious effects in renal physiology but for the most part tend to be well tolerated at appropriate doses.
• Sedation, premedication and preparation of CKD - phenothiazines

  E.g. Acepromazine

  Can cause Vasoldilation and subsequent hypotension that may dip below the range of auto regulation.

  Appropriate doses along with careful monitoring of blood pressure and treatment of hypotension is essential.
• Sedation, premedication and preparation of CKD - alpha-2 Adrenergic agonists

  e.g. Medetomidine, dexmedetomidine.

  Are used in cats with renal disease because this class of drug has the potential to cause up to a 60% decrease in cardiac output and a 50% decrease in RBF is seen dogs alongside an increase in GFR. Can assume that the mechanisms in cats are similar to dogs although there is no solid evidence.

  Should be avoiding in blocked cats due to their diuretic effect and should be used with caution in other cases of renal impairment when possible.
• Sedation, premedication and preparation of CKD - Benzodiazepines

  e.g. diazepam, midazolam.

  Are well tolerated in renally impaired cats, nevertheless, this class of drug can cause paradoxical excitement and should be used alone with caution in cats and young, healthy animals. Co-administration with an opioid is recommended.
• Sedation, premedication and preparation of CKD - opioids


  E.g. Buprenorphine, methadone, Butorphanol, morphine.

  Are generally safe for renally impaired cats and their use is often beneficial. Opioid administration may help decrease the sympathetic response associated with pain and surgery, minimising renal vasoconstriction.

  Administration of opioids can decrease the amount of inhalant necessary to keep the patient under, avoiding unnecessary hypotension.
• Induction and maintenance of CKD patients

  Induction agents like Propofol and Alfaxalone are good choices for anaesthetic inductions since the negative effects associated are transient and, with subsequent fluid therapy, minimised.

  Ketamine is avoided in the cat as it relies on renal excretion. Compromised renal function may lead to impaired drug elimination.

  Inhalants should always be used sparingly in CKD patients as they are strong vasodilators and can cause hypotension and a reduction in RBF.
• Managing the CKD patient intra and post-operatively


  Avoid renal vasoconstriction and GFR reduction.

  Treat pain/ nociception.

  Local regional anaesthesia (nerve blocks).

  IVFT continue into post operative period and encourage diuresis.

  Oxygen supplementation post operatively.

  Maintain normothermia.
• Approach to anaesthesia - hyperthyroidism

  Hyperthyroidism is the most common endocrinnopathy in middle to older aged cats.

  Treatment options include radioactive iodine, anti-thyroid medication, low iodine diet or surgery.

  Stabilise before you anaesthetise.

  Surgery is not without risk - bleeding, hyper and hypotension, inadvertent removal of parathyroid gland, hypocalcaemia post-op.

  Minimise stress, preoxygenate, premeditate, pre-place cannula.

  CKS can be exacerbated after treatment.
• Approach to anaesthesia - Hypothyroidism

  Common in dogs.

  Dogs may require GA before or during treatment, stabilise before hand.

  For anaesthesia of an uncontrolled hypothyroid:

  • Use short acting drugs
  • Anticipate prolonged recover and try to avoid and support hypothermia.
  • Cardiovascular signs will be common.
• Approach to anaesthesia - hypoadrenocorticism (Addison’s)

  Stabilise before you anaesthetise.

  Unstable digs can not mount a stress response, so provide exogenous steroids peri-operatively (hydrocortisone, dexamethasone and prednisolone).

  Consider postponing elective surgery until stable.

  Emergency cases unresponsive to fluids and inotropes - include Addisons as a ddx.
• Approach to anaesthesia - hyperadrenocorticism (Cushing’s)

  Stabilise before anaesthetise.

  Condition caused by excessive glucocorticoids.

  Animals may require GA during treatment.

  Prone to hypoxaemia and hypertension.

  Pulmonary thromboembolism can occur.

  Thin skin, prone to bruising.

  Hepatomegaly and large abdomen.
• Approach to anaesthesia - glucose homeastasis disruption

  Stabilise before GA.

  Aim to avoid hypoglycaemia and prolonged severe hyperglycaemia (ketoacidosis).

  Schedule GAs in the morning to avoid long starvation periods.

  Monitor blood glucose every 30-60 minutes.

  Respond if necessary (glucose and insulin).

  Diabetic patients might be dehydrated, hypovoleamic, or both, especially if fasted or anorexic for long periods of time.