Preclinical DMVD – what you should know before anaesthesia

Managing anaesthesia in dogs with preclinical DMVD (Degenerative Mitral Valve Disease) can feel like walking a tightrope. While they’re not yet in heart failure, these patients are often sensitive to fluid shifts, vasodilation and tachycardia – particularly in stage B2 and beyond. It’s understandable to feel cautious, but with the right approach, anaesthesia can be performed safely. This guide outlines practical steps for managing these patients, focusing on drug choices, fluid therapy, and peri-anaesthetic monitoring. 

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Fluid therapy: Use with care

Preclinical DMVD isn’t a strict contraindication to IVFT, but it does call for restraint. These patients have limited tolerance for volume overload, which can tip them into congestive heart failure (CHF).

Key principles:

• Only if needed: Don’t start fluids routinely – assess for volume deficits first. If perfusion and blood pressure are stable, IVFT may not be necessary.
• Go slow: If fluids are required, use conservative rates (0–2 ml/kg/hr) and avoid boluses where possible.
• Be prepared: Keep frusemide on hand, but don’t try to balance fluids and diuretics simultaneously. If needed, assess filling status using TFAST, lung ultrasound, thoracic radiography or—ideally—Doppler echocardiography.
• Mind the flushes: In small patients, IV line flushes add up fast. Decant pre-filled flushes into 1 ml syringes to limit accidental volume delivery and keep the whole team fluid-aware.
• Track everything: Monitor total volume administered throughout the procedure.

Cardiac medications: Maintain the routine

Continue cardiac medications as usual – including on the day of the procedure—unless specifically contraindicated (e.g. ACE inhibitors in hypotensive patients). 

Points to consider:

• Don’t guess staging: Perform echocardiography to investigate murmurs before anaesthesia. For elective procedures, reassess B1 cases not scanned in the last six months.
• Pre-optimise B2 cases: If possible, start pimobendan 1–2 weeks before planned anaesthesia to support cardiac function.
• Monitor SRR: Encourage owners of advancing B2 patients to track sleeping respiratory rate in the lead-up to procedures – this helps establish a baseline and can detect early decompensation.
• Reminder: Coughing is not a reliable sign of CHF.

Fasting and water access

Water: Allow free access up until premedication unless the patient is:

• Brachycephalic
• Prone to regurgitation
• Likely to drink excessively before premed

Food: Withhold as per your standard anaesthetic protocol.

Drug choices: Thoughtful and stage-specific

• Acepromazine (ACP): Avoid or use with caution, especially in stage B2, due to risk of vasodilation and hypotension. In early B1 cases, low-dose ACP may be acceptable.
• Midazolam and opioid: Premed with an opioid alone, then co-induce with midazolam. Avoid giving midazolam too early – it can cause disinhibition or agitation.
• Avoid alpha-2 agonists: Vasoconstriction increases mitral regurgitation. Also avoid ephedrine for the same reason, particularly if hypotension arises.
• Use regional blocks: Local techniques (e.g. nerve blocks, splash blocks) reduce inhalant needs. High inhalant concentrations reduce cardiac output through systemic vasodilation.

Summary

• Reassess if needed: If there’s been no echo in 6+ months, a repeat scan is worthwhile before elective anaesthesia.
• Use IVFT judiciously: Only when indicated, with slow rates and careful volume monitoring.
• Stick with cardiac meds: Maintain usual medications unless advised otherwise.
• Avoid extremes: Choose anaesthetic protocols that minimise vasodilation and vasoconstriction.
• Think local: Regional anaesthesia can significantly improve stability and reduce inhalant requirements.

Still unsure how to proceed? Get in touch with our cardiology team – we’re always happy to help.

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