Patient Evaluation

The veterinarian’s first impression of the patient should enable categorization of the horse into one of three categories: mildly painful, moderately painful, or severely painful. A mildly painful horse should have a complete and detailed physical examination, but can be treated successfully on the farm. A moderately painful horse should receive a complete examination, but the option of referral should be discussed. Although the horse may be stable initially, if referral is an option, the horse should be shipped to a facility for further management before possibly decompensating. A severely painful horse should receive an abbreviated physical examination that focuses on resuscitative and analgesic therapies. The horse should be stabilized for transport to a surgical facility.

Every detailed physical examination should begin with a detailed history. Has there been any recent diet change or new shipment of hay? Has there been a change in exercise level or access to pasture? Changes in diet and exercise are known to increase the risk for colic in horses. Questions about the medication history will occasionally turn up information about supplements the horse is receiving that may be causing a problem, or may help identify an ongoing problem. Asking open-ended questions such as “Can you tell me what problems you are having?” or “What do you think is the problem?” frequently provides more useful information than direct questions.

Early in the examination of any painful horse, referral should be discussed. If it becomes necessary, the client should be prepared with regard to where the horse should be transported and what the expected costs and experience of the referral will be. In many instances, transportation has to be arranged for the horse, and clients should be counseled to start preparing transportation in the event that referral is warranted. Clients should be advised of the expected costs early in the diagnostic workup, and the insurance status of the horse should be discussed.

When a patient is stable enough for detailed examination, the clinician’s initial impression is formed by the horse’s general appearance. Is there evidence of discomfort, such as nostril flare or high respiratory rate? Is there evidence of self-trauma around the eyes that is indicative of prior pain and rolling? Is the horse covered in mud or bedding? Is the horse trembling or sweating?

Any good examination follows a system. The author’s system begins with evaluation of the mucous membranes. Mucous membranes are described in many different colors, and the term toxic line is often mentioned. The author prefers a simpler system. Injected mucous membranes are red and have prominent vasculature. The red color is a result of hyperperfusion of the vascular bed as a result of increased cardiac output in the early stages of the systemic inflammatory response syndrome (SIRS). As disease progresses, the mucous membranes become pale as a result of vasocon­striction when the body attempts to maintain perfusion in response to falling cardiac output. Finally, the vessels vasodilate, leading to the cyanotic color seen with serious hypotension and low cardiac output; this change is consistent with the later stages of SIRS. The color of the mucous membranes can help the veterinarian understand the volume status of the patient and whether there is a need for intravenous fluids. Both pale and cyanotic membranes indicate the need for intravenous resuscitative fluids. Icteric membranes are frequently encountered if the horse has been anorexic or has hepatic disease or hemolysis. The capillary refill time (CRT) is related to perfusion of the oral mucosal capillary bed. A prolonged CRT is an indication of the need for oral or intravenous fluids. Prolonged CRT with poor mucous membrane color warrants aggressive resuscitative fluid therapy. The feeling of the mucous membranes is also useful because changes in the tactile quality of the membranes are related to interstitial fluid hydration. Tacky mucous membranes indicate interstitial fluid dehydration and the need for oral or intravenous fluids. While examining the face, the veterinarian should look for nasal discharge and assess the horse’s breath odor because many cases of colic turn out to be horses with illness involving something other than the gastrointestinal tract. Ignoring signs of respiratory disease may cause the examiner to miss the entire problem that is causing the signs of colic. Like the oral mucous membranes, the sclera should be examined for evidence of inflammation or icterus. The elasticity of the skin is affected by interstitial fluid volume, and prolonged skin tenting indicates dehydration. As horses age, the skin loses elasticity, and the skin tent may be prolonged to some extent, even with normal hydration. Additionally, some hereditary dermal diseases can also affect skin tenting.

One indicator of volume status is jugular filling time. Occluding the vein should lead to a visibly distended jugular vein in about 2 seconds. Prolonged jugular fill time is an indication of hypovolemia and the need for intravenous fluids. Similarly, heart rate is affected by volume status. Cardiac output is the product of heart rate and stroke volume: CO = HR × SV. Reduced stroke volume necessitates an increase in heart rate to maintain cardiac output. Heart rate will also increase as a result of stress, pain, and systemic inflammation. Auscultation of the heart and lungs should be done deliberately and slowly. The rhythm, character, and rate of the heartbeat should be evaluated. Lung and tracheal auscultation in all fields should be evaluated for fluid, crackles, wheezes, or pleural rubs. The lung fields can be percussed for evidence of consolidation or pleural effusion. Horses with cardiac and pulmonary disease often are presented for evaluation of colic. Auscultation of the abdomen should not be rushed. An appropriate length of time should be dedicated to listening for borborygmus. Identification of different sound quality can help distinguish horses that are painful from ileus from those that have intestinal cramping from hypermotile activity. Percussion of the abdomen may reveal a “ping,” indicating that there is a gas–fluid interface in a viscus, a finding consistent with colonic gas distension and large intestinal ileus.

Obtaining the rectal temperature is important because many inflammatory conditions cause fever. Rectal temperature is not always equal to core body temperature. Low rectal temperatures are seen with hypovolemia, which leads to poor perfusion and can result in pneumorectum. External palpation of the abdomen may identify ventral edema, which develops when fluid flowing into the interstitial space exceeds that draining through the lymphatics. Pleural effusion, low oncotic pressures, and inflammation are common causes of ventral and pectoral edema.