Perioperative Fluid Management With Dr. Carly Mitchell, Bellarmine University

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Hello, future CRNAs! Get ready for an exciting episode with Dr. Carly Mitchell, the founding program administrator for the Doctor of Nursing Practice Nurse Institute Program at Bellarmine University. Since March 2022, Dr. Mitchell has been serving as the Chief Nurse Anesthetist in an obstetric anesthesia department.

With her expertise in improving nurse institute preceptorship, obstetric and neuraxial anesthesia, and women’s health and wellness, Dr. Mitchell brings a wealth of knowledge to her dual roles. In this episode, she’ll be sharing invaluable insights on perioperative fluid management. Don’t miss out on this opportunity to learn from one of the best in the field. Tune in now!

Join the Free CSPA Community! Connect with a network of Aspiring CRNAs, Nurse Anesthesia Residents, practicing CRNAs and CRNA Program Faculty Mentors here: https://www.cspaedu.com/community

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The Bellarmine University Doctor of Nursing Practice-Nurse Anesthesia Program is designed for post-BSN students seeking doctoral preparation for advanced practice as a Nurse Anesthetist. The curriculum provides students with the specialized knowledge and skills necessary to care for diverse patient populations across the lifespan. Graduates of the program are prepared to assume clinical leadership roles in health-related organizations to improve systems of care, patient outcomes, and quality of care. Upon successful completion of the program, graduates are eligible to sit for the National Certification Exam (NCE) offered by the National Board of Certification and Recertification for Nurse Anesthetists (NBCRNA).

Learn More about the Bellarmine University Doctor of Nursing Practice-Nurse Anesthesia Program: https://www.bellarmine.edu/lansing/nursing/graduate/dnp-na/

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Perioperative Fluid Management With Dr. Carly Mitchell, Bellarmine University

We have a very special guest, Dr. Carly Mitchell, who is the founding program Administrator for the Doctor of Nursing Practice Nurse Anesthesia Program at Bellarmine University. Since March of 2022, she has held the position of Chief Nurse Anesthetist in an obstetric anesthesia department. Dr. Mitchell specializes in improving nurse anesthesia, preceptorship, obstetric and neuroaxial anesthesia, and women’s health and wellness, bringing a wealth of knowledge and expertise into her dual roles. In this episode, she will share her wisdom on perioperative fluid management. I hope you enjoy it.

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I am Dr. Carly Mitchell, Program Administrator for Bellarmine University, Chief Nurse Anesthesia Program. I’m presenting on perioperative fluid management. Perioperative fluid administration aims to achieve two primary goals. 1) Maintaining adequate intravascular volume to support cardiac output and tissue perfusion and 2) preventing electrolyte and acid-base imbalances. Intravenous fluid therapy is a fundamental aspect of anesthesia practice. As such, the anesthesia provider is responsible for selecting the appropriate IV fluids and determining the optimal timing and volume for administration.

Approximately 60% of body weight is composed of total body water. This total body water can then be divided into intracellular and extracellular components. Intracellular volume accounts for about 40% of the total body water, whereas extracellular accounts for about 20% of total body water. The extracellular compartment is further divided into the intravascular or plasma volume and the interstitial fluid. The distribution and amount of total body water change with age.

In newborn infants, total body water is about 75% to 80% of body weight because infants store less fat. During childhood, total body water slowly decreases to approximately 60% to 65% of body weight. During adolescence, the percentage of total body water approaches adult proportions, and gender differences begin to appear. Males eventually have a greater percentage of body water as a function of increasing muscle mass, whereas females have more body fat and less muscle as a function of estrogens and therefore have less body water.

Fluid Compartments And Their Compositions

As you get older, the percentage of body water declines further still. When we look at the two compartments of fluid, we can see they have very different compositions. The intracellular fluid refers to the fluid within all the cells of the body, and this fluid contains large amounts of potassium, magnesium, and phosphate ions. The extracellular fluid compartment, on the other hand, refers to all the fluid outside the cells, which contains large amounts of sodium, chloride, and bicarbonate ions plus nutrients for cells such as oxygen, glucose, fatty acids, and amino acids.

It contains carbon dioxide that is being transported from the cells to the lungs to be excreted, plus other cellular waste products that are being transported to the kidneys for excretion. The cell membranes serve as the primary barrier to the movement of substances between the extracellular and intracellular compartments. However, there are special mechanisms for transporting ions through the cell membranes that serve to maintain the ion concentration differences between the extracellular and intracellular fluid compartments.

Fluid exchange between the extracellular compartments is largely dependent on Starling forces. These are four transcapillary pressures whose gradients dictate the direction of fluid movement across the capillary epithelium. These four pressures can be subdivided according to their function. The first group is forces that move fluid from the capillary to the interstitial space, and this includes the capillary hydrostatic pressure, which is the intravascular blood pressure driven by the force of the cardiac output and impacted by vascular tone, and it serves to push fluid out of the capillary.

The interstitial oncotic pressure is the osmotic force of colloidal proteins within the interstitial space that pulls fluid out of the capillary into the interstitial space. The second group of pressures are forces that move fluid from the interstitial space into the capillary, such as the interstitial hydrostatic pressure, which is the hydrostatic pressure of the interstitial space that pushes fluid into the capillary. The capillary or plasma oncotic pressure is the osmotic force of the colloidal proteins within the vascular space that pulls fluid into the capillary.

Increases in capillary hydrostatic pressure and interstitial oncotic pressure favor the filtration of fluid into the interstitial space. Increases in interstitial hydrostatic pressure and capillary or plasma oncotic pressure favor the absorption of fluid into the intravascular space. A thin gel-like layer known as the glycocalyx coats the endothelial membrane and is involved in the regulation of endothelial permeability. Intravenous fluid resuscitation and other factors that increase intravascular hydrostatic pressure can degrade the glycocalyx layer, particularly in patients with sepsis or other conditions associated with microcirculatory dysfunction.

Because electrolytes move freely across the endothelial membranes, they do not create significant osmotic forces in transcapillary fluid equilibrium. However, they do play an important role in the fluid shifts between the intracellular and extracellular compartments. Understanding the normal electrolyte composition of the intravascular, intracellular, and extracellular compartments is essential for selecting replacement fluids that maintain the electrolyte balance and water distribution between these compartments.

Crystalloid And Colloid Solutions

Despite the availability of numerous crystalloid and colloid replacement fluids, the ideal fluid is still a subject of debate. Understanding the composition of each type of fluid is crucial for making informed decisions about which replacement fluids to use. Crystalloid solutions are mixtures of electrolytes and water. They can be categorized by composition, such as balanced versus unbalanced. Balanced solutions contain electrolytes in proportions similar to plasma, whereas unbalanced solutions like normal saline do not match plasma electrolyte ratios.

They can be categorized by tonicity, such as hypotonic, isotonic, and hypertonic. The thing to know about crystalloids is that these solutions do not contribute to oncotic pressure and diffuse out of the intravascular space shortly after administration. Colloid solutions contain large molecular weight substances like albumin or synthetic starches. They have a higher plasma oncotic pressure, helping to maintain intravascular volume longer than crystalloids. Consequently, a smaller volume of colloid solution is needed to maintain the same intravascular volume compared to crystalloid solutions. In critically ill patients with increased vascular permeability, colloids may have a shorter intravascular half-life than anticipated. Choosing between crystalloids and colloids and among different colloid solutions involves weighing the different risks and benefits.

Perioperative Fluid: Water follows salt. Water moves from a lower concentration of solutes to a higher concentration of solutes in fluid management.

Categorizing Fluids by Tenacity

I mentioned that fluids can be categorized according to their tenacity. I do want to spend a little bit of time talking about this particular concept. Tenacity compares the osmolarity of a solution relative to the osmolarity of the plasma. Since plasma is isotonic to cells, we can use the tenacity of a solution in comparison to the tenacity of the cells. When we are selecting a particular IV solution to administer, we have to consider how it will affect cell volume. Hypotonic solutions contain fewer solutes compared to that of the cells. When we give a hypotonic solution, the water from that solution will shift from the intravascular space to the intracellular space or inside the cell and cause the cell to swell. Remember, water follows salt. Water is going to move from a lower concentration of solutes to a higher concentration of solutes.

Isotonic solutions, on the other hand, will remain in the intravascular space because the water and solute concentrations are already at equilibrium. Hypertonic solutions will pull water from the intracellular space to the intravascular space and cause the cell to shrink. I’ve included this table to show how the different IV fluids, be they crystalloid or colloid solutions, are categorized according to tenacity. Whether they’re hypotonic, isotonic, or hypertonic solutions, keep in mind that we’re talking about the osmolarity of the fluid relative to plasma or cells. This is important because the addition or loss of fluid occurs in the extracellular fluid compartment, and this new osmolarity in the extracellular fluid compartment determines the direction of the fluid shifting. Fluids will shift until the osmolarity between the extracellular fluid and intracellular fluid compartments equilibrate.

Looking closer at hypotonic solutions, hypotonic solutions have a lower osmolarity than the plasma or cells, and giving a hypotonic solution increases the extracellular fluid and intracellular fluid volumes, and it decreases plasma osmolarity. It’s important to note that these solutions can cause a sudden fluid shift from blood vessels into cells, and if a fluid shift is significant enough, it could cause cardiovascular collapse from intravascular fluid depletion and increased intracranial pressure from fluid shifting into brain cells. These fluids are akin to giving free water, and this free water is distributed throughout all the body compartments. This explains why hypotonic solutions are poor expanders of intravascular volume and why you should never give a hypotonic solution to a patient with increased intracranial pressure.

The wild card is D5W because technically it does contain dextrose, which is an osmotically active molecule, but this glucose is metabolized to carbon dioxide and water. Essentially, all that’s left is water. Isotonic solutions have an osmolarity that approximates the plasma or the cells. These solutions expand the plasma volume and the extracellular fluid compartment. As such, they are indicated for volume replacement. Giving an isotonic solution increases the extracellular fluid volume, but the intracellular fluid and the plasma osmolarity stay the same.

Normal saline, which is one of the most commonly administered crystalloid solutions, is slightly hypertonic compared to the other fluids in this category as it contains more chloride than the extracellular fluid. When used in large volumes, it can cause mild hyperchloremic metabolic acidosis. This is why Lactated Ringers or LR is a better choice for large-volume resuscitation, such as with trauma. The lactate in LR functions as a buffer. Lactate is converted to bicarbonate by the liver and the kidneys and bicarbonate reduces the risk of metabolic acidosis. Normal saline does not contain any buffers or other electrolytes, and it is preferred to LR, which contains a hypotonic concentration of sodium in the presence of things such as brain injury, hypochloremic metabolic alkalosis, or hyponatremia.

Many patients with hyperkalemia, including those with renal failure, should receive normal saline because it doesn’t contain any potassium. Normal saline or plasma light are the preferred solutions for the dilution of packed red blood cells. However, you should avoid LR due to its calcium content. These solutions expand the intravascular fluid compartment. you want to be sure to closely monitor the patient for signs and symptoms of fluid overload, especially if the patient has hypertension or congestive heart failure.

Hypertonic solutions have an osmolarity that exceeds the plasma or cells. Giving a hypertonic solution expands the intravascular volume by pulling fluid from the intracellular fluid compartment into the extracellular fluid compartment. The extracellular fluid and plasma osmolarity increase, but the intracellular fluid decreases. Hypertonic solutions are indicated for cellular and interstitial overhydration because they are higher osmotic pressure solutions. Hypertonic saline solutions are used in trauma and head-injured patients to mobilize fluids into the intravascular space, but they carry risks such as osmotic demyelination syndrome. You want to avoid hypertonic solutions in patients with cellular dehydration like diabetic ketoacidosis or patients with impaired heart or kidney function as they can’t handle the extra fluid loads.

Traditional Approach To Perioperative Fluid Management

The traditional approach to perioperative fluid management uses the 4-2-1 rule to determine maintenance fluid requirements. Using this rule, total maintenance fluids are calculated based on a patient’s weight in kilograms with the following equation, 4 mls per kilogram per hour for the first 10 kilograms plus 2 mls per kilogram per hour for the second 10 kilograms, plus an additional 1 ml per kilogram per hour for the remainder of the weight. For example, a 70-kilogram patient would require 4 mls per kilogram per hour times 10 kilograms, plus 2 mls per kilogram per hour times the next 10 kilograms with an additional 1 ml per kilogram per hour times 50 kilograms for a total of 110 MLS per hour. In addition to maintenance fluid requirements, the anesthesia provider would calculate the fluid deficit from a patient’s NPO status in addition to intraoperative blood loss and other insensible fluid losses.

However, using this method, it was not uncommon for patients to receive upwards of 5 liters of fluid intraoperatively. What we have come to learn is that optimal fluid management is likely dependent on individual hemodynamic status, and any overarching strategies will likely benefit some but may cause harm to others. In fact, the Enhanced Recovery After Surgery or ERAS Society provides a strong recommendation for using advanced hemodynamic monitoring, such as arterial line monitoring and stroke volume monitoring, in high-risk patients undergoing major surgery with large intravascular fluid loss in order to practice a strategy of goal-directed fluid therapy.

Goal-Directed Fluid Therapy

In a goal-directed fluid therapy-based strategy, fluid therapy is titrated in response to advanced hemodynamic monitoring, which serves as a surrogate for optimizing stroke volume and cardiac output. Several studies, primarily of high-risk patients undergoing major abdominal surgery, have concluded that the use of a goal-directed fluid therapy algorithm has improved postoperative morbidity and decreased intensive care unit length of stay.

Overview Of Bellarmine University’s CRNA Program

I want to thank you for taking the time to listen to this presentation on fluid management. As such, I want to take a few moments to tell you a little bit about our program. Bellarmine University Doctor of Nursing Practice spans 36 months and encompasses 101 credit hours. It’s tailored for post-BSN students pursuing doctoral-level preparation as nurse anesthetists. Classes begin in August 2024 with ongoing enrollment of twenty students per cohort each year. The first two semesters consist of full-time study online in an asynchronous format, followed by seven semesters of full-time study on-site. The curriculum commences with foundational courses introducing advanced practice nursing and fostering doctoral-level thinking. Key courses include Foundations of Scholarship, Healthcare Informatics, and National and Global Health Policy.

Anesthesia-specific coursework begins in the third semester, focusing on Applied Sciences, Anatomy, Physiology, Pathophysiology, Pharmacology, and basic principles of Nursing Anesthesia. Students also engage in immersive learning experiences facilitated by our advanced simulation center, equipped with high-fidelity mannequins, point-of-care ultrasound simulators, and specialized task trainers. Students practice essential skills such as airway management and invasive procedures to enhance their clinical proficiency.

In semester four, the clinical practicum phase commences and extends throughout the remainder of the program, emphasizing the practical application of theoretical concepts learned in the nurse anesthesia curriculum. Students gain hands-on experience in administering anesthesia care to individuals across the lifespan at diverse clinical sites within prominent regional hospitals. All clinical rotations, including primary and specialized placements, are conducted locally through our formal collaboration with Norton Healthcare.

Successful completion of the program qualifies graduates to sit for the National Certification Exam administered by the National Board of Certification and Recertification for Nurse Anesthetists, marking their readiness to practice as certified registered nurse anesthetists. To learn more about our program of study, admission criteria, and application process, I invite you to join one of our upcoming information sessions on July 24th, August 21st, or September 25th. All sessions are held in person and online.

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That sums up perioperative fluid management. Thank you so much to Dr. Carly Mitchell for presenting this topic. It was a pleasure to have you on the show, and we hope to have you back. For those of you listening, thank you as always. We appreciate you and best of luck on your CRNA journey.

Important Links

FREE! CRNA School Interview Prep Guide: https://www.cspaedu.com/irptwqbx

Join the Free CSPA Community! Connect with a network of Aspiring CRNAs, Nurse Anesthesia Residents, practicing CRNAs and CRNA Program Faculty Mentors here: https://www.cspaedu.com/community

Get access to application & interview preparation resources plus ICU Educational Workshops that have helped 1,000s of nurses accelerate their CRNA success. Become a member of CRNA School Prep Academy: https://cspaedu.com/join

Get CRNA School insights sent straight to your inbox! Sign up for the CSPA email newsletter: https://www.cspaedu.com/podcast-email

Book a mock interview, resume or personal statement critique, transcript review and more: www.teachrn.com

Learn More about the Bellarmine University Doctor of Nursing Practice-Nurse Anesthesia Program: https://www.bellarmine.edu/lansing/nursing/graduate/dnp-na/