Fluid Overload in Small Animal Patients

2024 AAHA Fluid Therapy Guidelines for Dogs and Cats

Fluids are drugs used in veterinary patients capable of producing beneficial therapeutic or inadvertent harmful effects within the body's intravascular, interstitial, and intracellular fluid spaces. The individualized design of a fluid therapy plan requires careful patient assessment and targeted selection of proper fluid types, administration routes, and rates, along with adjustments during therapy tailored specifically as per the individual patient's fluid requirement and therapeutic response. Personalized fluid prescriptions and vigilant patient monitoring help avoid patient morbidity from body fluid deficiencies, fluid excess, and electrolyte derangements and support better patient outcomes. These guidelines provide an overview of fluid dynamics within the fluid spaces of the body, describe various types of fluids and their uses, and outline recommendations for fluid administration for resuscitation, rehydration, and maintenance purposes. The guidelines also outline approaches to fluid therapy for anesthetized patients and reiterate the recommendations of reduced fluid rates in this population of patients. Additionally, the guidelines include practical fluid therapy strategies for patients with various common disorders. The goal of these guidelines is to help veterinary professionals safely and effectively prescribe and administer fluid therapy for canine and feline patients.

Investigation of biomarkers for impending fluid overload in a feline acute haemorrhage-resuscitation model

OBJECTIVE

To determine biomarkers for impending fluid overload during intravenous fluid administration in a feline haemorrhage-resuscitation model.

STUDY DESIGN

Randomized crossover study.

ANIMALS

A group of six domestic cats (mean age and weight: 21 months; 4.9 kg, respectively).

METHODS

The cats underwent three treatments, 2 months apart. They were anaesthetized and instrumented to measure a range of physiological, blood gas, haematological and biochemical variables over time. Samples were taken during a health check, before haemorrhage, after haemorrhage and then at 30 minute intervals during fluid resuscitation and 24 hours later. The three treatments were: 1) control, sham haemorrhage and resuscitation; 2) lactated Ringer's solution (LRS); and 3) 6% tetrastarch 130/0.4 (Vol) where the cats underwent a controlled haemorrhage then resuscitation by administering LRS and Vol at 60 and 20 mL kg^-1 hour^-1, respectively, for 120 minutes. Fluid overload was identified by nasal discharge and radiographic evidence. Biomarkers were variables that exceeded the reference interval for cats during treatment. Potential biomarkers were analysed using receiver operating characteristic curves (p < 0.05).

RESULTS

Mean ± standard deviation total blood loss was 10.2 ± 2.3, 29.3 ± 9.0 and 29.1 ± 6.3 mL kg^-1 for control, LRS and Vol, respectively. The total volume of LRS and Vol administered was 120 and 40 mL kg^-1, respectively. Haematocrit, albumin, magnesium, chloride-to-sodium ratio and sodium-chloride difference were identified as potential biomarkers. These variables exceeded the reference intervals from 30 minutes of resuscitation onwards. A chloride-to-sodium ratio > 0.84 was the most sensitive (90%) and specific (75%) of all potential biomarkers.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes in physiological variables, haematocrit and albumin were poor biomarkers of impending fluid overload compared with electrolytes. Finding the ideal biomarker to identify impending fluid overload of commonly used intravenous fluids should improve the safety of their administration in cats.

Closed-Loop Control for Fluid Resuscitation: Recent Advances and Future Challenges

Fluid therapy is extensively used to treat traumatized patients as well as patients during surgery. The fluid therapy process is complex due to interpatient variability in response to therapy as well as other complicating factors such as comorbidities and general anesthesia. These complexities can result in under- or over-resuscitation. Given the complexity of the fluid management process as well as the increased capabilities in hemodynamic monitoring, closed-loop fluid management can reduce the workload of the overworked clinician while ensuring specific constraints on hemodynamic endpoints are met with higher accuracy. The goal of this paper is to provide an overview of closed-loop control systems for fluid management and highlight several key steps in transitioning such a technology from bench to the bedside.

Terms, Definitions, Nomenclature, and Routes of Fluid Administration

Fluid therapy is administered to veterinary patients in order to improve hemodynamics, replace deficits, and maintain hydration. The gradual expansion of medical knowledge and research in this field has led to a proliferation of terms related to fluid products, fluid delivery and body fluid distribution. Consistency in the use of terminology enables precise and effective communication in clinical and research settings. This article provides an alphabetical glossary of important terms and common definitions in the human and veterinary literature. It also summarizes the common routes of fluid administration in small and large animal species.

A pilot study evaluating adaptive closed-loop fluid resuscitation during states of absolute and relative hypovolemia in dogs

OBJECTIVE

To evaluate and determine the performance of a partially automated as well as a fully automated closed-loop fluid resuscitation system during states of absolute and relative hypovolemia.

DESIGN

Prospective experimental trial.

SETTING

Research laboratory.

ANIMALS

Five adult Beagle dogs.

METHODS

Isoflurane anesthetized mechanically ventilated dogs were subjected to absolute hypovolemia (controlled: 2 trials; uncontrolled: 3 trials), relative hypovolemia (2 trials), and the combination of relative and absolute controlled hypovolemia (2 trials). Controlled and uncontrolled hypovolemia were produced by withdrawing blood from the carotid or femoral artery. Relative hypovolemia was produced by increasing the isoflurane concentration (1 trial) or by infusion of intravenous sodium nitroprusside (1 trial). Relative hypovolemia combined with controlled absolute hypovolemia was produced by increasing the isoflurane concentration (1 trial) and infusion of IV sodium nitroprusside (1 trial). Hemodynamic parameters including stroke volume variation (SVV) were continuously monitored and recorded in all dogs. A proprietary closed-loop fluid administration system based on fluid distribution and compartmental dynamical systems administered a continuous infusion of lactated Ringers solution in order to restore and maintain SVV to a predetermined target value.

MEASUREMENTS AND MAIN RESULTS

A total of 9 experiments were performed on 5 dogs. Hemodynamic parameters deteriorated and SVV increased during controlled or uncontrolled hypovolemia, relative hypovolemia, and during relative hypovolemia combined with controlled hypovolemia. Stroke volume variation was restored to baseline values during closed-loop fluid infusion.

CONCLUSIONS

Closed-loop fluid administration based on IV fluid distribution and compartmental dynamical systems can be used to provide goal directed fluid therapy during absolute or relative hypovolemia in mechanically ventilated isoflurane anesthetized dogs.