Surgical treatment for left atrial rupture due to myxomatous mitral valve disease in three dogs: A case report.

INTRODUCTION: Myxomatous mitral valve degeneration (MMVD) is an acquired heart disease which sometimes result in pulmonary oedema and left atrial rupture. In previous reports, left atrial rupture has been non-surgically controlled and its prognosis investigated. There is, however, no report concerning surgically treated left atrial rupture with mitral valvuloplasty and follow-up results. OBJECTIVES: This report aimed to develop a surgical strategy for a case of left atrial rupture caused by MMVD. MATERIALS AND METHODS: Three dogs were presented at a private hospital for surgical treatment of MMVD. All three dogs had a previous history of left atrial rupture due to MMVD. The left atrium rapture was diagnosed from indicating that characteristics of the drained pericardial effusion consistent with blood. Mitral valvuloplasty was performed in all dogs using an extracorporeal circulation machine, and the surgical procedure was modified according to each case. In cases with severe adhesion between the pericardial and left atrial appendage, suturing of the left atrial appendage was performed strategically. Additionally, in cases with severe hypotension caused by left atrial rupture, cardiopulmonary bypass was started as soon as possible during the surgical procedure. DISCUSSION AND CONCLUSION: Since the haemodynamics of all dogs had improved, and the owner reported no cardiac-related clinical signs, all drugs were withdrawn 3 months after surgery. Since left atrial rupture due to MMVD can cause hypotension, cardiopulmonary bypass should be started as soon as possible during the surgical procedure to maintain the blood pressure and suturing of the left atrial appendage should be performed strategically.

Hemodynamic Effects of Protamine Infusion in Dogs with Myxomatous Mitral Valve Disease Undergoing Mitral Valvuloplasty.

Protamine, an antagonizing agent to heparin, is indispensable for dogs undergoing cardiopulmonary bypass. Protamine-induced hypotension (PIH) during cardiac anesthesia has been reported in humans. The purpose of this study was to describe the hemodynamic effect of protamine administration in dogs during cardiac surgery in clinical cases. Study design: Retrospective, clinical, cohort study. A total of 14 client-owned dogs who suffered heart failure due to medically uncontrolled myxomatous mitral valve disease (MMVD) were included in this study. The severity of MMVD was classified according to American College of Veterinary Internal Medicine staging (ACVIM: stage B2, C, D) and dogs undergoing mitral valve surgery. Records with clinical data for dogs treated between July 2019 to August 2020 were examined for age, sex, breed, body weight, concurrent diseases, hospitalization, anesthetic record, and mortality within 3 months after the operation. PIH was defined as mean arterial pressure (MAP) lowered by 20% of that before protamine infusion. To evaluate the effect of protamine on hemodynamic variables, each of the other values was compared with values at the beginning of protamine infusion. MAP decreased by 41.0 and 45.7% in two dogs (14.3%) compared with pressure before protamine infusion. Others did not show obvious alteration in hemodynamic variables. Epinephrine treatment alleviated hypotension in one dog. Another dog with systemic hypotension concomitant with elevated central venous pressure did not respond to epinephrine treatment and a reboot of extracorporeal circulation was required. Reheparinization and reinstitution of cardiopulmonary bypass successfully resuscitate the second dog. In conclusion, clinicians should alert the incidence of severe hypotension even with slow protamine infusion following canine cardiac surgery. This study also provides two effective treatments for catastrophic hypotension during protamine infusion.

Metabolic alkalosis following mitral valvuloplasty in a dog with preoperative acute kidney injury.

CASE DESCRIPTION: An 11-year-old sexually intact male Shih Tzu diagnosed with acute kidney injury and left-sided congestive heart failure that had nonelective mitral valve surgery. CLINICAL FINDINGS: Metabolic alkalosis developed postoperatively, and plasma bicarbonate concentration peaked 2 days after surgery (40.2 mmol/L; pH, 7.550). TREATMENT AND OUTCOME: Acetazolamide administration increased the urinary excretion of bicarbonate and contributed to the improvement of the dog's acid-base status and oxygenation capacity. Metabolic alkalosis persisted for 4 days after surgery, and no treatment was required after resolution. Plasma urea nitrogen and creatinine concentrations normalized 2 days after surgery. CLINICAL RELEVANCE: Severe metabolic alkalosis can occur as a complication following mitral valve surgery. Acetazolamide may be suitable for the treatment of severe metabolic alkalosis.

Early experience with low-prime (99 ml) extracorporeal membrane oxygenation support in children.

Quick setup is mandatory for cardiopulmonary resuscitation using an extracorporeal membrane oxygenation (ECMO) assist device. Our conventional ECMO circuit for pediatric patients consists of a centrifugal pump (CX-HP) and membrane oxygenator (CX10H). Because of the large priming volume (260 ml), the circuit had to be primed with donor blood and required 30 minutes for setup. We started to use a low-prime ECMO with small centrifugal pump (HPM-15) and membrane oxygenator (MENOX Alpha Cube) for induction of ECMO beginning in 2000. The priming volume of this low-prime circuit is only 99 ml. The circuit can be primed without donor blood, even in the small patient, and requires only 10 minutes to set up. We review our experiences with cardiopulmonary resuscitation for sudden cardiopulmonary collapse in pediatric patients, including postcardiotomy patients. From 1997 to 2000, 23 patients underwent ECMO support with a conventional circuit (group A). From 2000 to 2004, we used low-prime circuit for induction of ECMO in 12 patients (group B). After the induction of ECMO with low-prime circuit, ECMO was converted to conventional heparin-bonded circuit for the longer support. The results suggested that the quick induction of ECMO with low-prime circuit has significant advantages in cardiopulmonary support in pediatric patients.