Close monitoring is essential to detect changes that can indicate deterioration is imminent; this allows intervention to prevent a crisis before it occurs. The most useful information is provided by observing a 'trend' in the monitored vital sign, rather than a single one-off measurement. To make spotting an ongoing trend easier, accurate recording is essential. How often these parameters are monitored will depend on the severity of the condition and the perceived risk of deterioration and is customised to the individual patient and the complications that could develop, all of which can be recorded on the animal's nursing plan. It should be remembered that re-assessing a few relevant 'basic' parameters repeatedly may detect early deterioration as opposed to running more complex tests that take much longer to complete. Where specific problems are suspected from physical examination, then more specific monitoring can be performed, such as clotting times, slide saline autoagglutination, blood gases and lactate levels.

Before commencing a systematic assessment, a general assessment of the patient and their surroundings should be carried out. When approaching the patient, general observations should include body condition, posture, behaviour, mentation, as well as listening for abnormal breathing sounds or laboured respirations. In addition, the presence of any paraphernalia around the patient, such as oxygen delivery devices, infusion pumps and urinary collection bags may provide insight into their wider health status.

Monitoring needs to be tailored to the individual patient. However, there are certain parameters that should be recorded regularly regardless of the patient's status. It should be remembered that the nurse must have knowledge of physiological parameters in order to detect even the subtlest of abnormalities.

A useful path to follow when assessing major body systems is ABCD, where:

A: Airway
B: Breathing
C: Circulation
D: Dysfunction of the central nervous system (CNS)

A and B: Respiratory System

The assessment of the respiratory system should begin as the patient is approached by observing their posture, respiratory effort and pattern, and whether any airway sounds are clearly audible. In the normal patient, ventilation involves very little chest movement, and the chest wall and abdomen move out and in together. The rate should be recorded along with the effort the patient is making to breathe if this is abnormal. Bradypnoea may be associated with amongst other things hypothermia or drug toxicity, particularly opioids. Tachypnoea may reflect decreased oxygen in the blood (hypoxaemia), thoracic trauma, or shock, or may be related to a non-respiratory source, such as pain, stress, increased body temperature or metabolic acidosis. It is well documented in human medicine literature that tachypnoea is often an early and discrete sign of deterioration and may precede changes in other vital signs.

Auscultation is an important part of an assessment of the respiratory system. A stethoscope should be used to auscultate the chest wall, systematically auscultating each area, comparing the same areas on the right side of the chest to the left. There are several breath sounds one should be familiar with, but the main ones to be aware of in detecting early deterioration are reduced or absent breath sounds, wheezes and crackles.

Breath sounds may be reduced or absent where pleural disease exists. More commonly, lower airway sound abnormalities that are likely to be detected are crackles, wheezes, or rales (abnormal clicking, bubbling, or rattling sounds). Crackles may indicate pulmonary oedema such as that resulting from fluid overload, whereas wheezes are the result of airway narrowing and may be due to any condition causing broncho-constriction such as inflammation or due to mucous accumulation.

C: Circulatory System

Heart rate can be measured by auscultation of the heart and palpation of an artery. Conducting both simultaneously allows any pulse deficits to be detected. Bradycardia may be considered normal during sleep, in athletic patients, or as a consequence of medication (opioids, alpha-2 agonists), electrolyte imbalances, increased intra-cranial pressure hypothermia and feline shock. Severe bradycardia has the potential to lead to significant reduction in cardiac output, in which cardiogenic shock ensues.

Increased pulse rate is an early and sensitive indicator of vascular volume loss, acting as a compensatory mechanism to increase cardiac output, even though stroke volume is diminished. If tachycardia is due to volume loss, restoration of an effective circulating blood volume should cause the heart rate to return to normal. Other causes of tachycardia, such as pain, fever, hypoxaemia or hypercapnia, should be considered. It must be remembered that, compared with dogs, cats in shock often have heart rates that are slower than normal, frequently in the 120–180 bpm range. All pulse abnormalities should be confirmed by an electrocardiogram.

Blood Pressure Monitoring

Accurate, regular monitoring allows for the detection of subtle variations that may otherwise go unnoticed. Although an elevated blood pressure (hypertension) is an important risk factor for cardiovascular disease, it is a falling or low systolic blood pressure (hypotension) that is most significant in the context of detecting early deterioration. Hypotension is common amongst patients in the pre-arrest setting. Hypotension may indicate circulatory compromise due to sepsis or volume depletion, cardiac failure or cardiac rhythm disturbance as well as CNS depression.

Normal blood pressure values in dogs and cats

Mucous membrane colour and capillary refill time

The normal mucous membrane colour is pink. In diseased states, this colour may be yellow, pale, white, brick red or blue.

Capillary refill time (CRT) is an indication of peripheral perfusion and should not be thought of as an indicator of blood pressure. Prolonged CRT, longer than 2 seconds, suggests poor prefusion due to peripheral vasoconstriction and is often seen in patients with hypovolaemic and cardiogenic shock. Conversely, a CRT of less than one second can be seen in patients in hyperdynamic states such as systemic inflammation or fluid overload.

Mucous membrane colour and it's possible significance

D: Dysfunction of the CNS

A change in consciousness can be a sign of patient deterioration. The aim here is not to perform a full neurological examination but rather a swift assessment of the patient's consciousness.

Levels of consciousness

Central nervous system (CNS) depression may be a result of conditions such as hypovolemia, hypotension, anaemia, and those causing hypoxia, including pulmonary disease, airway obstruction or pleural space disease. Whilst metabolic disorders, such as hypoglycaemia or electrolyte derangements, can cause seizures.

Following assessment of the major body systems, a brief examination of the rest of the body should be performed.

Temperature

Core body temperature is usually assessed by a rectal thermometer reading. Body temperatures over 40°C (>104°F) are of concern; temperatures over 42°C (>107°F) are life-threatening.

Hypothermia can be defined as a body temperature less than 37°C (<99°F), although it is hard to identify a definite number. As well as factors including cold exposure, severe infection, endocrine abnormalities, and drug overdoses low core body temperature can be associated with hypovolaemia. If a reading of 36°C or below is obtained, the patient should be assessed again to double check no other signs of poor perfusion are present.

It should be remembered that changes in body temperature are a characteristic feature of sepsis; if the patient has signs or symptoms that indicate possible infection, it is important to raise the alarm.

Bodyweight

It is important to record the patient's weight at admittance. Bodyweight fluctuates daily throughout a patient's stay in the hospital due to a variety of factors, nutritional status, type of acute illness, and presence of comorbidities. Acute changes in body weight are attributed to changes in fluid balance rather than body mass. When hydrated, an acute gain in bodyweight would be a concern for excess fluid accumulation (e.g., oedema). Conversely, acute weight loss may indicate ongoing fluid losses or continued dehydration.

The Role of Intuition

The importance of the role played by human senses cannot be overstated in the management of patients at risk of clinical decline. The most important monitoring technique is clinical assessment by using your own senses.

References

1.  Farry T and Norkus C. (2019). Monitoring the critical patient. In: Norkus, C. L. (Ed.). Veterinary Technician's Manual for Small Animal Emergency and Critical Care. 2nd Edition. John Wiley & Sons, Chichester: 45–63.

2.  Humm K R and Kellett–Gregory L (2016). Monitoring small animal patients in the intensive care unit. In Practice. 38:12–17.

3.  Pachtinger G (2013) Monitoring of the emergent small animal patient. Vet Clin North Am Small Anim Pract. 43:705–720.