Making Sense of Fluids and Electrolytes

A hands-on guide

Zoja Milovanovic, Abisola Adeleye

• Publisher: CRC Press
• Year: 2017
• eBook ISBN: 9781315351605
• Edition: 1
• Topic: Medicine
• Subtopic: Anesthesiology & Pain Management

Interpreting the fluid requirements of a patient and working out what to do next can seem like a daunting task for the non-specialist, yet it is a skill that any doctor, nurse or paramedic needs to be fully appraised of and comfortable with.

Making Sense of Fluids and Electrolytes has been written specifically with this in mind, and will help the student and more experienced practitioner working across a variety of healthcare settings to understand why fluid imbalance in a patient may occur, to assess quickly a patient's fluid needs through a thorough clinical assessment and to develop an effective management plan. Reflecting the latest guidelines, this practical, easy-to-read and easy-to remember guide will be an invaluable tool to aid speedy and appropriate management in emergency situations, on the ward and in the clinic.

CHAPTER 1

Fluid assessment

FLUID ASSESSMENT – FORMAT

Fluid management requires a full clinical assessment with a particular focus on the systems that affect the water content of the body: cardiovascular, renal, endocrine and gastrointestinal.

In your clinical assessment, you should focus on the patient’s overall wellbeing, as well as the fluid status in the different compartments. It is crucial to gauge which compartment has an excess or deficit of fluid, as excess in one compartment does not automatically mean excess in all compartments. For example, a patient with peripheral oedema might actually have an intravascular fluid deficit that can manifest itself clinically through hypotension and tachycardia. This book focuses on these clinically challenging situations.

HISTORY

Current medical problem

Why is the patient in hospital?

It is important to know why the patient was admitted to hospital. Evaluating the course of their treatment, plus any further medical problems, is equally important. For example, a patient might have been admitted with bowel obstruction, but has subsequently had a myocardial infarction; hence both of these would be the ‘current medical problem’ and would affect fluid therapy.

Current fluid status

Consider the patient’s fluid intake and causes of extra fluid losses: do they balance out?

History is the first step in fluid assessment. What has the patient taken in versus what has been excreted? Patients can usually tell you how much they have eaten and drunk and also roughly how much urine they have passed. It is good practice to correlate this information with the fluid balance chart.

Intake

Has their medical/surgical condition stopped them from drinking enough water? If so, have they had enough replacement for their age and size? Always assess a patient’s nutrition while they are in the hospital; this is the responsibility of all health care professionals. For example, surgical patients might be ‘nil by mouth’ (NBM) and therefore require maintenance fluid therapy, as well as replacement intravenous fluids (IVF). Assess the quantity of input from the following:

• Oral intake: All types of fluid
• IVF: Note types of fluids (crystalloids, colloids, blood products) and electrolyte composition
• Parenteral feeding: Note electrolyte composition
• Enteral feeding via a nasogastric tube (NGT), nasojejunal (NJ) tube or a percutaneous endoscopic gastrostomy (PEG) tube

Output

Assess all routes of output and insensible losses a patient might have. This includes assessing the quantity of:

• Previous/current diarrhoea, vomiting, urination and faeces.
• Catheters, drains, stoma outputs, NGTs, NJs, PEGs.
• Third-space losses, which are those where fluids shift to a ‘new’ compartment which is an extension of the extracellular fluid (ECF). This is sometimes seen in paralytic ileus, peritonitis and conditions causing ‘leaking’ from capillaries, such as anaphylaxis and sepsis.
• Insensible losses, which are those that cannot be accurately measured but can contribute significantly to a patient’s fluid losses (Figure 1.1):
  • Respiratory tract: Fluid that evaporates from the respiratory tract increases with increased respiratory rate, ‘mouth breathers’ and also in ventilated patients.
  • Skin: Sweating and pyrexia will increase fluid loss.
  • Surgical evaporation: Evaporation from exposed surgical sites during the operation.

Figure 1.1 Diagram showing all input and output. (NGT, nasogastric tube; NJ, nasojejunal; PEG, percutaneous endoscopic gastrostomy.)

Signs and symptoms of fluid depletion/overload can be vague, but put in context with the fluid balance chart, they should support your diagnosis. It is important to look at trends as they will reveal the course of fluid abnormality. For example, a patient may become progressively hypotensive due to dehydration (if they are NBM with no replacement fluid given) and the observation chart will show a steady decline in blood pressure and a rise in heart rate.

Hypovolaemia

• Symptoms: thirst, oliguria/anuria, orthostatic hypotension, headache, lethargy, confusion, vomiting, diarrhoea
• Signs: decreased skin turgor, increased capillary refill time (>2 seconds), cool peripheries, dry mucous membranes, tachycardia, weak thready pulse, tachypnoea, hypotension, increased respiratory rate, coma

Hypervolaemia

• Symptoms: polyuria or oliguria, shortness of breath (SOB), orthopnoea
• Signs: peripheral and central oedema, ascites, raised jugular venous pressure (JVP), added heart sounds, basal crepitations on chest auscultation, increasing weight over a short period of time, headache, confusion, coma

Note: signs of hyponatremia might be present too (nausea, confusion, loss of appetite and general malaise).

Think about the different fluid compartments (Table 1.1).

Table 1.1 Signs and symptoms associated with each compartment

Compartment	Symptoms of hypovolaemia	Symptoms of hypervolaemia	Signs of hypovolaemia	Signs of hypervolaemia
Intravascular	Thirst, nausea		Tachycardia, hypotension	Raised JVP
Interstitial	Thirst, nausea	SOB, orthopnoea	No oedema, dry mucous membranes, poor skin turgor	Oedema, ascites In good hydration: moist mucous membranes, good skin turgor
Intracellular	Headache, coma		Difficult to assess directly	Difficult to assess directly

Past medical history

A patient’s history will guide IVF prescribing. It should outline current fluid status and highlight any indications for cautious prescribing. Do they have a medical condition which will affect their body’s ability to respond adequately to fluid deficiency or excess?

Focus on the following:

• Cardiovascular: Ischaemic heart disease (IHD) and heart failure (HF) will, in varying degrees, affect the heart’s ability to pump blood around the body. Be cautious when prescribing fluid as decreased cardiac output might result in excess fluid outside the intravascular space, especially in patients with congestive cardiac failure (CCF). At the same time, it is important to aim for euvolaemia in these patients to ensure an adequate stroke volume and cardiac output (remember the Frank–Starling mechanism). Traditionally, getting the fluid balance right in this particular group of patients has always been a big challenge for doctors.
• Renal: Depending on the extent and cause of acute kidney injury (AKI) a patient may require extra fluids, or conversely they may require dialysis. Dehydration is one of the main causes of AKI, hence most patients require IVFs to manage their condition (a balanced crystalloid such as Hartmann’s is generally the first choice). If, however, an AKI patient is oligo-anuric and develops clinical signs of fluid overload, in most cases this would be an indication for urgent renal replacement therapy. Chronic kidney disease (CKD) of varying degrees will affect how the body excretes fluids and electrolytes and hence the quantity and type of fluid required. Patients with end-stage renal failure may be on dialysis and no longer producing any urine; fluid therapy in these patients should be measured and conducted under senior guidance.
• Hepatic: Decompensated liver disease may affect s...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Acknowledgements
• List of abbreviations
• How to use this book
• 1 Fluid assessment
• 2 Keeping the balance: physiology, electrolytes and intravenous fluids
• 3 Cardiac arrest and shock
• 4 Intravenous fluid therapy in medical patients
• 5 Fluid therapy management in surgical patients
• 6 Blood products and transfusion
• Index