Bendroflumethiazide, Chlortalidone, Hydrochlorothiazide, Indapamide, Metolozone, Xipamide
Issues for Surgery
For treatment of hypertension – loss of blood pressure (BP) control if omitted.
For treatment of oedema – risk of fluid retention and increased risk of exacerbation of symptoms in heart failure patients if omitted.
For diabetes insipidus – risk of hypovolaemia (due to polyuria) if omitted.
Hypovolaemia, hypotension and/or electrolyte disturbances if continued (see Interaction(s) with Common Anaesthetic Agents, Interaction(s) with other Common Medicines used in the Perioperative Period and Further information).
Advice in the Perioperative period
Elective and Emergency Surgery
Continue – including the following combination products: -
Consideration should be given to prescribing the components of combination products as separate medicines perioperatively. However, some components of combination products do not exist as individual medicines (e.g. hydrochlorothiazide). If there is any doubt about the need to continue/withhold component agents of a combination product, advice should be sought from an anaesthetist.
Correct electrolyte abnormalities (especially hypokalaemia and hypomagnesaemia) prior to surgery1 – see Further Information.
Monitor urea and electrolytes (U&E’s) and BP. Dosage reduction should be considered in patients with hypovolaemia, hypotension, or electrolyte disturbances1.
For patients with diabetes mellitus, monitor blood glucose (BM) concentrations since thiazides can provoke hyperglycaemia2, 3.
Interaction(s) with Common Anaesthetic Agents
Thiazide and related diuretics can increase the risk of hypotension when used concomitantly with inhalational or intravenous anaesthetics2, 3, 4.
Neuromuscular Blocking Drugs (NMBDs)
Thiazide and related diuretics may increase the response to NMBDs, probably due to their hypokalaemic effect, although there appears to be no clinical significance – monitor3, 4.
Interaction(s) with other Common Medicines used in the Perioperative Period
Potassium-sparing diuretics can increase the risk of hypotension when used concomitantly with the antiemetics droperidol and prochlorperazine2.
Concomitant use of thiazide and related diuretics with Non-Steroidal Anti-inflammatory Drugs (NSAIDs) increases the risk of hyponatraemia2.
Concomitant use of thiazide and related diuretics with gabapentin increases the risk of hyponatraemia2.
Thiazide and related diuretics may cause hypokalaemia; this potentially increases the risk of torsade de pointes when given with ondansetron – monitor serum potassium closely2, 3, 4.
NSAIDs (also see Electrolyte Disturbances above)
Concomitant use of thiazide and related diuretics with NSAIDs increases the risk of acute renal failure (ARF)2, 3.
NSAIDs can cause fluid retention and may antagonise the diuretic actions of thiazides and related diuretics2, 4.
Hypokalaemia is reported to occur in up to 34% of patients undergoing surgery (mostly non-cardiac). It is thought to significantly increase the risk of ventricular fibrillation and cardiac arrest in cardiac disease1, 3. In one study, hypokalaemia was independently associated with perioperative mortality. Care should be taken with patients taking diuretics and patients prone to developing arrhythmias1. The risk of hypokalaemia is greater with thiazide diuretics than equipotent doses of other types of diuretics2.
NB: Potassium supplementation alone may not be sufficient to correct hypokalaemia in patients who are also deficient in magnesium3.