As veterinary medicine is continuously evolving, so are pet owner expectations for the level of care their pets receive. Using Kirby’s Rule allows veterinary technicians to look at the overall clinical picture of the patient and implement critical thinking skills.
Kirby’s Rule of 20 was created by Rebecca Kirby, DVM, DACVIM, DACVECC, and is a checklist of 20 parameters that should be evaluated daily in critically ill patients. Kirby’s Rule of 20 is used as a tool/reference to ensure quality patient care in critical patients is being monitored. The parameters on the checklist are:
1. Fluid balance
2. Albumin/oncotic pull
3. Mentation
4. Heart rate, contractility, rhythm
5. Blood pressure
6. Oxygenation and ventilation
7. Body temperature
8. Electrolytes and acid-base
9. Glucose
10. RBCs and hemoglobin
11. Coagulation
12. Renal function
13. GI motility and integrity
14. Nutrition
15. Immune status (antibiotics)
16. Drug dosage and metabolism
17. Wound care and bandages
18. Pain control
19. Nursing care
20. Tender loving care
Fluid Balance
Physiologically speaking, the body’s fluid compartments are divided between intracellular (ICF), or within the cell, and extracellular (ECF), or the intravascular and interstitial, compartments. Fluid imbalances occur from any condition(s) that alters a patient’s ability to adequately compensate and restore its own fluid requirements, thus requiring medical intervention. Intravenous fluids are used in the critically ill to maintain intravascular volume and adequate perfusion. To develop a fluid therapy plan, things like hydration status and ongoing losses are considerations that should be included in determining maintenance and replacement fluid therapy. When it comes to monitoring fluid therapy, a variety of parameters are assessed. First, assess the patient; this is done by evaluating physical parameters (heart rate, pulse quality, mm color/moisture, CRT, extremity temperature, attitude/mentation, blood pressure, skin turgor). Next, assess ongoing losses, which can include vomiting, diarrhea, polyuria, third spacing, or wound loss. Then, assess the patient’s inputs versus outputs, which can be done by evaluating urine output and serial body weights. Additionally, lab values, such as PCV/TP, lactate levels, and acid-base status, can give insight into a patient’s fluid status. Fluid therapy should also be monitored for signs of fluid overload, or overhydration; signs include serous nasal discharge, chemosis, subcutaneous edema, ascites, increased respiratory rate, coughing, and restlessness. Overall, knowing a patient’s disease process (i.e., renal failure, CHF, SIRS, pediatric) also allows for a better understanding of the patient’s fluid requirements.
Albumin/Oncotic Pull
Albumin is the predominant protein within the intravascular space and is responsible for maintaining vascular integrity and colloid oncotic pressure (COP). Oncotic pull is what keeps fluids within the vascular space; without albumin, there would be increased intravascular permeability, resulting in fluids leaving the intravascular space and causing third spacing and edema. Critical patients often suffer from hypoalbuminemia, which can result in hypotension or interstitial or pulmonary edema. Nutritional support, synthetic colloids and intravenous albumin are therapies that can be used to raise albumin levels. It should be noted that using plasma to raise albumin is not considered an appropriate therapy, as it requires a significant amount of plasma to do so (it takes 40–50 ml/kg FFP to raise albumin by 1 g/dL).
Mentation
Assessment of the patient’s neurologic status should be performed in every critical patient, not only in those with a primary neurological disorder. These parameters include level of consciousness (LOC), breathing pattern, pupillary light reflexes (PLR), pupil size and location, posture, reflexes, and the use of coma scale evaluation. The frequency of neurologic assessment will depend on the patient’s stability. Evaluation of a patient’s LOC can be classified as normal/alert, dull/depressed/obtunded (slowed/inappropriate response to sensory stimuli), stuporous (unconscious but arousable to noxious stimuli) or comatose (unconscious and unresponsive). Changes in LOC can be indicative of decreased cerebral function (i.e., lack of oxygen supply, change in cerebral perfusion) and should be addressed quickly to prevent further deterioration. One of the most commonly used coma scales is the Modified Glasgow Coma Scale (MGCS). The MGCS can be used to record progression or regression of the TBI patient over a period of time. The MGCS involves three separate categories, including assessment of LOC, motor activity, and brainstem reflexes. A score is given for each of these categories based on the patient’s clinical findings; a higher score will correlate with a better prognosis while a lower score will correlate with a poorer prognosis. This scaling system is beneficial because it allows for an objective evaluation of the patient that can be used to monitor progression or deterioration of their neurological state. Any change in mentation (positive or negative) should be reported to the clinician and warrants intervention.
Heart Rate, Contractility, Rhythm
Assessment of heart function involves both a mechanical and electrical evaluation. Frequent auscultation of heart rate, palpation of pulse quality, blood pressure measurement and evaluation of mucous membrane color can all be used as indicators of the heart’s ability to appropriately pump blood and provide systemic perfusion. Heart rate is usually the first cardiovascular parameter you perform when going through your initial assessment. Tachycardia is generally accepted as a heart rate greater than 160–180 bpm in dogs and greater than 200 bpm in cats. Bradycardia is generally accepted as a heart rate less than 80–100 bpm in dogs and less than 150–160 bpm in cats. Tachycardia could be indicative of fear, excitement, anxiety, pain, or shock (hypovolemia, hypotension). Bradycardia could be indicative of conduction disturbances, decreased cardiac output, poor perfusion, neurologic disease (i.e., increased intracranial pressure), hypothermia, increased vagal tone, drug overdose, or severe electrolyte disturbances. Pulse rate and quality should be taken in conjunction with HR auscultation. Pulse rate is reflective of systemic perfusion, and should match the auscultated HR. Pulse quality is reflective of the amount of blood that is pumped through the body with each heartbeat, which is known as stroke volume. An animal’s pulse quality can be described as normal (a steady pulsation against your finger that is synchronous with the heart rate), weak (a lighter than normal pulsation against your finger), bounding (a harder than normal pulsation against your finger), or absent (lack of pulsation against your finger). A normal pulse is indicative of normal stroke volume. Weak pulses are concerning for decreased stroke volume, poor contractility, or peripheral vasoconstriction. It should also be noted whether or not pulse deficits (absent pulses during cardiac contraction) are present, as they are also an indicator of inadequate stroke volume. Bounding pulses are reflective of systolic-diastolic difference in arterial blood pressure, which is concerning for increased stroke volume and vasodilation. Absent pulses indicate a failure in appropriate peripheral perfusion. Contractility refers to the strength of contraction of each heartbeat. In addition to noting the HR during auscultation, it should also be noted if there are any irregularities, which can indicate an arrhythmia and would warrant performing further diagnostics, such as an electrocardiogram (ECG). Use of an electrocardiogram (ECG) enables an evaluation of the heart’s electrical components, and is helpful in determining if an arrhythmia is present. Being familiar with what a normal ECG rhythm looks like is important to be able to recognize when an abnormal ECG rhythm occurs. Common arrhythmias seen in critical care include tachyarrhythmias (sinus tachycardia, VPCs, ventricular tachycardia, SVT, atrial fibrillation) and bradyarrhythmias (sinus bradycardia, AV blocks, atrial standstill, sick sinus syndrome, bundle branch blocks).
Blood Pressure
Arterial blood pressure monitoring can be very useful in critical care cases. Blood pressure (BP) is reflective of appropriate cardiac output and perfusion; maintaining a systolic BP >90 mm Hg or mean BP >60 mm Hg is essential for maintaining organ perfusion. Blood pressure is most easily measured via noninvasive indirect methods, such as oscillometric or Doppler technique. It is important to use the appropriate cuff size (approximately 40% of the limb circumference) as well as to use the same limb for each measurement to ensure consistency and accuracy of results. In critically ill patients, hypotension is more common than hypertension. Hypotension is caused by decreased cardiac preload, or decreased venous return. Examples of disease processes that can cause hypotension include hypovolemia, GDV, anaphylaxis, sepsis, SIRS, pleural space disease and heart disease. Trends in blood pressure readings are more important than a one-time measurement. Other methods of monitoring perfusion besides BP include mentation, heart rate, pulse quality, mucous membrane color, capillary refill time, and extremity temperature.
Oxygenation and Ventilation
Pulmonary function can be compromised in critically ill patients for a variety of reasons, and assessing respiratory parameters is vital. Ventilation is the process of appropriate gas exchange within the alveoli; oxygen is inhaled, and carbon dioxide is exhaled. Oxygenation refers to how well oxygen is diffused from the alveoli, bound to hemoglobin, and dissolved and delivered to bodily tissues. The “gold standard” for measuring oxygenation and ventilation status is through arterial blood gas; however, this is not always a feasible option. Alternatively, parameters such as respiratory rate, respiratory effort, respiratory character, lung auscultation, pulse oximetry, and venous blood gas can be used. Pulse oximetry (SpO2) is an easy, noninvasive means to measure the oxygen saturation of hemoglobin. A venous blood gas allows for measurement of CO2, which is the parameter that indicates appropriate ventilation. For patients who are not oxygenating well (i.e., SpO2 <95%), supplemental oxygen therapy may be necessary. For patients who are not ventilating well (i.e., CO2 >60 mm Hg), intubation and manual/mechanical ventilation may be necessary. Another tool worth mentioning is the oxyhemoglobin dissociation curve. The curve depicts the relationship between oxygen hemoglobin saturation and partial pressures of oxygen. The curve is determined by hemoglobin’s affinity for oxygen (how readily hemoglobin acquires and releases oxygen molecules). The relationship is sigmoid in shape, and factors such as temperature, PCO2 and pH affect the curve. The curve shows that small changes in hemoglobin saturation (SpO2) correlate with large changes (roughly 4x lower value) in PaO2.
Body Temperature
Body temperature is part of the initial clinical examination and should be measured regularly in every critically ill patient. Temperature is most accurately measured via rectal thermometer, and fluctuations should be reported to the clinician. Animals maintain their temperature within a range called the “set point.” The set point is determined by the thermoregulatory center in the hypothalamus. When an animal’s temperature rises or falls out of this range, the body reacts by increasing or decreasing the core temperature in an attempt to return to the set point. Hyperthermia can be attributed to environmental exposure (i.e., heatstroke), infectious sources, inflammatory sources, or neoplastic diseases. Hypothermia can be attributed to anesthetic recovery or systemic disease processes (i.e., cardiovascular disorders, shock). Permissive hypothermia is sometimes tolerated in cases of traumatic brain injury or head trauma, as lower temperatures decrease metabolic demands.
Electrolytes and Acid-Base
Electrolyte abnormalities are a common finding on lab work and can have harmful consequences if not identified and corrected. Sodium, potassium, chloride, and calcium should all be monitored and maintained within their normal ranges. They are critical for cell function, cardiac performance, vascular tone, brain function, neuromuscular activity, and fluid balance. Other electrolytes that should be monitored, if possible, are phosphorus and magnesium. Changes in electrolytes can manifest as changes in mentation (sodium), ECG rhythms (potassium, calcium), and acid-base status (chloride).
Assessment of acid-base status gives insight into three physiologic processes: alveolar ventilation (venous), acid-base (venous or arterial), and oxygenation (arterial). Venous blood gas (VBG) analysis is arguably one of the most routinely used point-of-care tests done in the critical care setting. A VBG is performed when there is a need to know what a patient’s acid-base or ventilation status is. The results of a VBG give the veterinary team more information about the severity of a critical patient’s disease, so that appropriate interventions (i.e., fluid therapy, electrolyte supplementation, oxygen support) can be provided. When evaluating a patient’s VBG result, the values needed for interpretation are pH, PCO2, and HCO3. The pH is a measurement of acidity or alkalinity of the blood (how many hydrogen molecules are present in the blood). An excess of hydrogen ions causes a decrease in pH (acidosis), while a shortage of hydrogen ions causes an increase in pH (alkalosis). The PCO2 is a measurement of the partial pressure of carbon dioxide in the blood. PCO2 is an indicator of the respiratory component of a blood gas analysis. An excess of CO2 causes an acidosis, while a shortage of CO2 causes an alkalosis. The HCO3 is a measurement of bicarbonate (bicarb) in the body. Bicarb is a major buffer, and represents the metabolic component of blood gas analysis. Acid-base disturbances in critically ill animals include metabolic acidosis, metabolic alkalosis, respiratory acidosis and respiratory alkalosis. Metabolic acidosis is the most common acid-base derangement in critically ill animals.
Glucose
Glucose is considered the body’s primary energy source and is utilized by every cell. Glucose is stored in the liver in the form of glycogen. Ideally, blood glucose levels should be maintained between 65–120 mg/dL. Alterations in blood glucose (BG) can occur from many disease states/processes. Hypoglycemia can be caused by excess insulin (i.e., overdose, insulinoma), toxins (i.e., xylitol), hepatic disease, metabolic disease (i.e., hypoadrenocorticism, Fanconi syndrome), or sepsis. Hyperglycemia can be caused by lack of insulin (i.e., diabetes mellitus, DKA), neurological disorders, or renal disease. In critical illness, hypoglycemia is more common than hyperglycemia. Depending on the disease state, frequent blood glucose monitoring may be necessary, in which case placement of a sampling catheter may be worthwhile.
RBCs and Hemoglobin
Red blood cells (RBCs) contain hemoglobin, and are therefore responsible for carrying and transporting oxygen molecules throughout the circulatory system; each hemoglobin molecule can carry four oxygen molecules. Maintaining adequate hemoglobin levels is therefore essential to maintaining adequate oxygen delivery. Measuring packed cell volume (PCV) is a quick and easy test to measure the concentration of RBCs. In critical patients, a decrease in RBCs can become life-threatening due to impaired perfusion and lead to multiorgan dysfunction. The kidneys respond to decreased oxygen delivery from anemia by releasing erythropoietin, a hormone which stimulates production of RBCs by the bone marrow. The spleen is responsible for storage and removal of old or damaged red blood cells. If anemia is present and associated with clinical signs (tachycardia, tachypnea, lethargy, altered mentation), administration of blood component therapy (i.e., whole blood, packed red blood cells) may be warranted. Administering blood products is not a benign therapy; it requires blood typing and cross-matching to limit the chance of a reaction, as well as frequent monitoring during a transfusion for signs of a reaction.
Coagulation
Coagulation is the process of clot formation within the vasculature. Coagulation abnormalities occur in the critically ill due to disease processes affecting hemostasis. These include thrombocytopenia, von Willebrand’s, hemophilia, hepatic disease, rodenticide toxicity, or hypercoagulable states (i.e., Cushing’s, IMHA, sepsis). Evaluation of clotting times (PT, aPTT) requires specific blood draw techniques to ensure accuracy. It is also necessary to monitor for signs of hemorrhage, which include petechiae, ecchymoses, hematuria, or bleeding from incisions and wounds. In cases of severe coagulopathy, it may be indicated to implement blood component therapy (i.e., frozen plasma). Another concern in the critically ill is the development of disseminated intravascular coagulopathy (DIC). DIC is a systemic activation of coagulation that leads to widespread microvascular thrombosis.
Renal Function
The kidneys are vital to life and are responsible for many functions that help maintain overall homeostasis. Their functions include fluid regulation, hormone production, and excretion of metabolic waste products. They maintain the volume and composition of body fluids (water and electrolyte balance), they absorb solutes (proteins, amino acids, glucose), and they remove metabolic waste from the body (urea, uric acid, creatinine). The kidneys receive approximately 20–25% of overall cardiac output and help maintain arterial blood pressure, and therefore are susceptible to damage/injury during periods of poor perfusion. When any of the kidney’s functions become disrupted, there can be systemic consequences. A common disease process in critically ill patients is acute kidney injury (AKI). Acute kidney injury (AKI) is a clinical syndrome, defined as a rapid deterioration in kidney function resulting from injury. Azotemia is recognized by abnormally high concentrations of body waste compounds within the blood, primarily blood urea nitrogen (BUN) and creatinine. Azotemia from AKI can further be grouped as prerenal, intrinsic renal, and postrenal, and is reflective of the type of AKI a patient is experiencing. Prerenal refers to “before” the kidney, meaning injury is caused by other physiological factors in which renal ischemia results (i.e., hypovolemia, dehydration, cardiac compromise, vasodilatory diseases). Intrinsic renal refers to direct damage to the renal parenchyma (i.e., toxins, infectious insult, neoplasia). Postrenal refers to “after” the kidney, meaning there is an obstruction or impediment in the outflow of urine that prevents urine from being eliminated from the body (i.e., urethral obstruction, urolithiasis, trauma). Urine output (UOP) should be closely monitored in the critically ill, as decreased urine output can also be indicative of impaired renal function. Normal UOP in a well-perfused, hydrated animal should be between 1–2 ml/kg/h. During states of abnormal UOP (i.e., polyuria, oliguria), urinary catheters should be placed and maintained to obtain a more accurate assessment of UOP. Other renal parameters to monitor include serial body weights, auscultation, and bloodwork to evaluate renal values.
GI Motility and Integrity
It is not uncommon for critically ill patients to initially present in a state of shock. Shock states result in perfusion priority being given to vital organ systems (brain, heart, lungs), which means other organ systems like the GI tract suffer. Hypoperfusion to the GI tract can contribute to increased intestinal permeability, which can lead to bacterial translocation and potentially sepsis. Common diseases associated with gastrointestinal dysfunction are parvovirus, hemorrhagic gastroenteritis, ileus, foreign body obstruction, gastric ulceration, gastric atony, IBD, PLE, and secondary disease states (i.e., pancreatitis, cholangiohepatitis, hepatic lipidosis). The use of prokinetics, such as metoclopramide, can help enhance motility. Gastroprotectants (such as famotidine, pantoprazole, ondansetron, and sucralfate) can all be used to decrease acid secretions and limit the likelihood of ulceration. Antiemetics (such as maropitant) should be used to curb nausea.
Nutrition
Nutrition is probably the most overlooked aspect of caring and managing critically ill patients. As veterinary medicine has advanced, so has the outlook on providing nutritional support to our patients. Nutrition should be provided to every patient, every time, as it is necessary for recovery from all disease processes. The methods of providing nutrition in a hospital setting include enteral and parenteral nutrition. Enteral nutrition is when nutrition is provided via the GI tract. The use of nasoesophageal and nasogastric feeding tubes are minimally invasive, relatively short-term methods of providing nutritional support; bolus feeding or trickle feeding options are available. Additionally, esophagostomy tubes can be surgically placed for more long-term nutritional support. For enteral nutrition, the patient’s resting energy requirement (RER) should be calculated, and feedings should be started at 1/4 to 1/3 RER. One potential complication of enteral nutrition is refeeding syndrome, which is a potentially life-threatening catabolic state in which there’s a rapid shift of intracellular electrolytes, causing hypokalemia, hypophosphatemia, and hypomagnesemia. Parenteral nutrition is when nutrition is provided intravenously. Parenteral nutrition can further be divided into partial parenteral nutrition (PPN) or total parenteral nutrition (TPN). Strict sterile technique is required when placing IV access for parenteral nutrition. One advantage to PPN/TPN is that the nutritional formulation can be custom made (dextrose, lipids, amino acids, electrolytes, vitamins) based on the patient’s specific needs.
Immune Status
The function of the immune system is to protect the body from invasion of foreign microorganisms. The immune system of the critical patient can be affected by patient factors, disease factors, and environmental factors. These factors include immunosuppression (i.e., leukopenia, undergoing chemotherapy), GI dysfunction (risk for bacterial translocation, aspiration, malnutrition), drug suppression, autoimmune disease processes, wound contamination, indwelling catheters/tubes/drains, infectious agents (i.e., zoonotic diseases), and nosocomial infections. Monitoring should include evaluation of white blood cells (i.e., daily CBC, daily blood smear), submission of culture and susceptibility, body temperature (monitor for fever), and daily assessment of wounds and/or insertion sites (i.e., incisions, IV catheter insertion sites) for signs of infection (discharge, odor, heat). Ideally, gloves should be worn with every patient and changed between patients. Use of antibiotics should be carefully chosen so as not to contribute to antibiotic resistance.
Drug Dosage and Metabolism
Pharmacokinetics is a branch of pharmacology that is concerned with how drugs move within the body; the processes include absorption, distribution, metabolism, and excretion. The medications of each patient should be reviewed daily to assess drug doses, dose frequency, and drug interactions. Medical calculations should also be double checked prior to administering medications to prevent over/underdosing, especially as patient weights can change while hospitalized. Patient considerations should also be reviewed, such as patients with renal/hepatic disease that may have altered metabolisms, or determining if a patient still requires a medication.
Wound Care and Bandages
Wound care involves not only wounds or bandages from incisions or lacerations, but also insertion sites. Any incision should be inspected daily for signs of infection or dehiscence; any dressings over an incision should be changed when soiled. Any wounds that have bandages should also be inspected and changed daily. IV catheter sites should be broken down, inspected and re-taped daily; any sign of infection, loss of patency, or inflammation, and the insertion site should be removed and replaced. Any tube insertion sites (i.e., feeding tubes, chest tubes, Penrose drains, etc.) should be inspected for patency and gently cared for. During handling of any wound or bandage, gloves should be worn always.
Pain Control
Being able to recognize, evaluate and alleviate pain is integral to the well-being of our patients. Over the last several years, the concepts of pain and pain management have become more prevalent within the veterinary field. Within emergency and critical care, the physiology, recognition, and management of pain have been given more research and attention. The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage”. Nociceptors (pain receptors) are present in the nervous system and become stimulated by a noxious stimulus (stimulation of a nerve ending). Nociception is the sensory process that involves a series of electrical events that start at the site of tissue injury, convey signals to the central nervous system, and result in the perception of pain. Nociception is essentially the pain pathway and can be broken down into four processes: transduction, transmission, modulation, and perception. A noxious stimulus occurs at the site of tissue damage, which initiates the transduction process the pain pathway. Transduction is the conversion of physical energy into electrical energy by the nociceptor. The electrical energy then becomes a nerve impulse that can travel in the pain pathway along the nervous system. Transmission is propagation of the electrical nerve impulses in the nervous system. This moves the nerve impulse from the site of tissue damage to the spinal cord. Modulation is amplification, inhibition, or suppression of nerve pain signals within the spinal cord. Perception is the integration, processing, and recognition of nerve signals in the brain. Perception is how the animal feels pain and is a subjective experience. Signs of pain can be classified as either behavioral (i.e., vocalizations, inability to rest, agitation, change in temperament, drop in activity level, insomnia, inappetence, immobility) or physiological (i.e., tachycardia, tachypnea, hypertension, hyperthermia, increased metabolic rate, decreased GI blood flow, immune suppression). Pain assessments should be included in the physical assessment of a patient. Monitoring for changes in pain using pain scoring systems is a great way to determine if pain is being managed appropriately or if additional pain relief therapies are needed. Pain, if left unidentified/untreated, leads to greater morbidity, mortality, and suffering.
Nursing Care and Tender Loving Care
Providing nursing care to the critically ill involves skilled, knowledgeable, attentive, and trained nursing staff. Nursing care is everything that goes above and beyond and that might not explicitly be listed on the treatment sheet—things like giving soft/plush bedding, physical therapy for recumbent patients, warming up food, providing urinary catheter care, ensuring cleanliness/baths, giving “privacy screens” for timid patients, applying eye lubrication for patients in oxygen kennels, flushing IV catheters to ensure patency when not on IV fluids, evaluating pain scores, etc. It is our job to care for our patients and be their advocate. All patients should be handled and spoken to kindly in order to help minimize stress and anxiety that can develop in a hospital setting. Taking the extra time to love and snuggle on your patients gives us a mental break and helps patients feel better.
References
1. Silverstein DC. Small Animal Critical Care Medicine. St. Louis, MO: Elsevier, Saunders; 2015.
2. Scalf R. Study Guide to the AVECCT Examination. San Antonio, TX: AVECCT; 2014.
3. Battaglia AM, Steele AM, Battaglia AM. Small Animal Emergency and Critical Care for Veterinary Technicians. St. Louis, MO: Elsevier; 2016.
4. Norkus C. Veterinary Technician’s Manual for Small Animal Emergency and Critical Care. Hoboken, NJ: Wiley-Blackwell; 2013.
5. Creedon JM, Davis H. Advanced Monitoring and Procedures for Small Animal Emergency and Critical Care. Oxford: Wiley-Blackwell; 2012.