The aim of the initial emergency examination is to rapidly identify any imminently life-threatening problems via a streamlined, efficient, clinical examination. The cardiovascular, respiratory and central nervous systems should be evaluated first followed by abdominal palpation and body temperature. The initial survey of each major body system is abbreviated such that the clinical signs that yield the most important information are examined first. Stabilization measures should be initiated for any major problems prior to the remainder of the full physical evaluation.
The most common conditions that change the clinical haemodynamic parameters are hypovolaemia, anaemia, sepsis/inflammatory response syndrome and abnormal cardiac function. Familiarity with how each condition in isolation affects the clinical haemodynamic parameters facilitates identification of the patient with multiple causes of abnormal perfusion. Most animals with abnormal perfusion have some component of hypovolaemia so recognizing uncomplicated hypovolaemia is the rational starting point. In uncomplicated hypovolaemia, mucous membrane colour, capillary refill time (CRT) and vigour, pulse profile (height and width), heart rate, and cardiac auscultation provide the means of intravascular volume assessment. A normal animal should have pink mucous membranes with a vigorous capillary refill that takes 1-1¾ seconds. Pulses (femoral and metatarsal) should be carefully palpated to allow assessment of their height (to estimate pulse pressure) and their width i.e., the length of time the pulse lasts. Assessing the height and width of the pulse together allows an estimation of pulse volume and a perceptive clinician can generate a mental image of the pulse profile. One should develop an awareness of the normal variation in pulse profile. A normovolaemic animal that is stressed or painful will have slightly higher and narrower pulse profile than a resting animal.
In the compensatory stages of hypovolaemia dogs will develop a moderate tachycardia of 140-160 beats per minute. The increased heart rate, reduced blood volume and increase in cardiac contractility produces a pulse which is narrower and higher than normal. This pulse profile is often referred to as "bounding" or "snappy" but these terms often serve to confuse rather than clarify. In compensatory hypovolaemia metatarsal pulses should still be palpable. Mucous membranes should be pink to pinker than normal with a rapid CRT of less than one second duration.
The increases in heart rate seen in dogs with hypovolaemia are surprisingly independent of body weight such that severe hypovolaemia results in a heart rate of 180-220 in most dogs. Heart rates in excess of this should raise suspicions of a primary arrhythmia rather than just a sinus tachycardia in response to hypovolaemia. Heart sounds are often very quiet due to the severe hypovolaemia (as are heart murmurs which will become apparent during volume loading!). Mucous membranes have little or no red coloration (white, muddy, or grey), and CRT is prolonged or absent. Femoral pulses are extremely weak (referred to as thready) and metatarsal pulses should not be palpable.
The ability to estimate intravascular volume status using clinical signs becomes invaluable when assessing the response to acute volume replacement. In general, during successful volume replacement perfusion parameters will gradually and predictably return to normal through the same stages in reverse. This enables the clinician to rapidly detect an inadequate response to volume resuscitation and pursue the underlying cause.
Successful emergency management of the animal with difficulty breathing demands that the clinician remains acutely aware of the fragility of the dyspnoeic patient. Even the stress of a brief major body system evaluation can prove fatal, especially in cats. Consequently, the risks of any diagnostic tests must be carefully weighed against the potential benefits and treatment may have to be instituted prior to a definitive diagnosis. Most dyspnoeic cats will benefit from a period in 100% oxygen in an oxygen cage prior to a complete major body system evaluation.
Initial evaluation of the respiratory system comprises respiratory rate, effort and respiratory auscultation. A normal animal should have a respiratory rate of 15-30 breaths per minute and (because the majority of a resting inspiration is due to diaphragmatic contraction) there should be very little apparent chest movement. During normal inspiration, diaphragmatic contraction displaces abdominal viscera caudally and the abdominal wall moves out passively. It should therefore be intuitive that contraction of the abdominal muscles can only assist with expiration. Abdominal effort should not be confused with paradoxical abdominal movement that is a manifestation of severe dyspnoea. As dyspnoea worsens, increased intercostal contraction draws the diaphragm cranially on inspiration and the abdominal wall moves in. Straightening of the neck and open mouth breathing occur in both dogs and cats, however, some other postural manifestations of dyspnoea vary between species. Dogs prefer to stand with abducted elbows, while cats tend to sit in sternal recumbency. Constantly changing body position in cats implies a much worse degree of dyspnoea than it does in dogs. Lateral recumbency due to dyspnoea is a serious sign in a dog, however, it often means impending death in a cat.
In a dyspnoeic animal the respiratory pattern can help localize the level of the respiratory tract affected in two common situations. Dynamic upper airway obstruction is usually associated with prolonged inspiration with inspiratory stridor or stertor, followed by a short expiration. Small airway disease, such as feline asthma, classically presents with a longer expiratory phase with increased abdominal effort on auscultation. Most other causes of dyspnoea are associated with mixed respiratory patterns. Pulmonary auscultation in the dyspnoeic patient is one of the true arts of veterinary medicine. The easiest way to ensure a complete auscultation is to divide the chest into a noughts and crosses board, then auscult each square. Lung sounds are normally slightly louder and more coarse in the cranioventral lung fields compared to the dorsocaudal fields and are symmetrical when the same area is compared on both sides of the chest (with the exception of the area of cardiac dullness in the left cranial fields. Pleural space disease causes muffling of lung sounds, whereas small airway or parenchymal disease usually makes them louder. The ability to establish a working diagnosis on the basis of history and physical examination without additional diagnostic tests, such as chest radiographs, can mean the difference between life and death in some dyspnoeic animals.
Central Nervous System
Initial evaluation of the CNS often amounts to deciding whether the abnormalities of gait and mentation are appropriate for the other problems identified in the major body system assessment. Dysfunction greater than expected from the degree of cardiovascular or respiratory compromise present should raise the suspicion of CNS disease and should prompt a more complete neurological examination. In general, gait abnormalities in single limbs are associated with less serious problems than when multiple limbs are affected.
Abdominal palpation and body temperature
Following examination of the major body systems, abdominal palpation is performed. Abnormalities such as pain on palpation, a large, hard urinary bladder or a fluid thrill may be detected. Lastly, body temperature is taken by rectal thermometer. A body temperature greater than 104°F (40°C) should be sufficient to raise concern, whereas a temperature of >107°F (42°C) can be life threatening.
Streamlining and standardizing the approach to major body system evaluation in the emergency patient allows the small animal emergency clinician to rapidly identify, assess and stabilize life-threatening abnormalities in an expedient fashion.