circle system of the machine, whereas a high partial pressure of anesthetic gas exists in the patient’s tissue, blood and lungs. The result i s that anesthetic begins to flow toward the compartment with the lowest concentration, thus reducing the tissue concentrat ion. Repeated dumping of the rebreathing bag with every 6 or 8 breaths continues to upset the equilibrium that tends to reestablish. As tissue levels of the agent fall, anesthesia lightens.

The same general factors governing the slowness or rapidity of anesthetic induction tend to influence recovery. Animals in shock, with reduced cardiac output, tend t o recover much more slowly than those with near-normal cardiac function. Low minute volume due to CNS depression also slows recovery.

Uptake and distribution of agents injected intravenously differs somewhat from the gaseous agents. Since the lungs are by-passed, the system can be likened to a two-compartment system, blood and tissues.

Distribution is controlled by blood flow and by solubility of the agent in the specific tissue in question. Again, the phenomenon of internal redistribution occurs (Figure 3) as the more poorly perfused tissues begin to absorb increasing amounts of agent. %OF DOSE

mkx 1 1 1 1 2 4 8 16 32 128 Q)

I 6 8 4 2 FIGURE 3

The mechanism for termination of anesthesia varies with injectable agents but, in general, is by metabolism in the liver and other tissues combined with elimination in the urine. Factors altering the duration of anesthesia include the patient’s body temperature, blood pressure, oxygenation, state of hydration, kidney function and degree of tubular reabsorption of the agent.

REFERENCES

Cnenoweth. M.B.: Physiologic and Biochemical Responses to Methoxyflurane Anesthesia. In Experimental Animal Anesthesiology. D.C. Sawyer, Ed., U S.A.F. School of Aerospace Medicine, Brooks Air Force Base, Texas, 1965. Jones, E.W., Burnap, T.K., Nelson, T.E., Anderson, I.L., and Kerr, 13.13.: Pre- linary Studies on Fulminant Hyperprexia in a Family of Swine. Proceedings, Annual Meeting, Am. SOC. of Anesthes., 1970. Sawyer, D.C.. Eger, E.I., 11, Bahlman, S.H., Cullen, B.F., and Impelman, D.: Concentration Dependence of Hepatic Halothane and Chloroform Anesthesia on the Equine Liver. Am. J. Vet. Res., 28, 1366, 1967.

PRE -SU RG IC AL EVALUATION OF THE LARGE ANIMAL PATIENT -

INCLUDING THE RATIONAL FOR SPECIFIC LABORATORY TESTS

john F . Fessler, D. V . M., Ph. D. t Diplomate, American College of Veterinary Surgeons

Introduction: Preoperative evaluation and preparation is in-

tended to establish certain needs and optimize the physiologic homeostasis of the patient for the best possible tolerance of surgical interven- tion. It has been said that surgery i s 75% judgment, 25% technique. Up to 75% of these judgments, perhaps 99% of these judgments, are pre-surgical judgments.

There are 3 phases of surgical treatment; pre- operative, transoperative, and postoperative treatment. This i s a rather artificial breakdown, perhaps a dangerous one. Preoperative and post- operative periods are all too often viewed as separate and distinct entities. Many hospital organizations foster this concept, when in fact what i s needed for the surgical patient is continuous care. There may be an irony here regarding large animals. Mos t general practitioners and large animal practitioners who do a reputable job with surgery do not have elaborate intensive care units, preoperative preparation units, or anesthetic recovery areas. These units are usually available for small animals and certainly for man. Thus, continuous care, or continuity of care may be more matter of fact for horses and food animals.

Unfortunately, preoperative evaluation is one of the hardest things for which to establish a rigid, unbending hospital protocol. The house staff in a large hospital seems to be the first to disregard a protocol. Yet, i t i s this very group, young and inexperienced, who can benefit the most from such a protocol. Human nature being what i t is, when things are going well the preoperative routine slips. It takes a catastrophy, anesthetic, surgical, or otherwise, to reinstill in the surgeon’s mind the need for a preoperative program. The paradox is obvious. A suitable preoperative evaluation can be instrumental in preventing the catastrophy in the first place.

Diagnosis of the Surgical Disease: It i s not the purpose of this paper to explore

the diagnosis of a surgical disease per se. Determining the indication for surgery - for a case of equine colic, as an example - is a subject unto itself. Tests like biopsy, cytology, and x-ray are more related to the surgical disease than to the preoperative evaluation of the patient as a tDepartment of Large Animal Clinics, Purdue University, Lafayette, Indiana 47907.

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whole. On the other hand, the finding of bacteria in acidic fluid from a horse with colic, as an indication of already existing peritonitis, certainly has prognostic implications. Without a diagnosis there wi l l be no surgery. Suffice it to say, diagnosis is preoperative evaluation.

Reasons for Preoperative Evaluation:

The reasons for carrying out a pre-surgical evaluation include establishing the needs of the patient and establishing the needs of the surgeon. The need for preoperative medical support with fluids, electrolytes, and antibiotics must be determined. The indicated methods of anesthesia and monitoring must be chosen. Electrocardiographic monitoring should be routine during general anesthesia of large animals but shock patients demand additional attention to blood pressure, central venous pressure, and urinary flow.

Pre-surgical evaluation helps in the develop- ment o f an ins ight i n to the po ten t ia l post-operative hazards and wound healing potential, or deficit, of the patient. Wound healing should receive special consideration when dealing with the obese, debilitated, parasitized, anemic, or recumbent patient. Routine laboratory studies wil l usually reveal a suspicious problem.

Preoperative evaluation must involve the entire surgical team. Good records must be accessible to all members of the team and the lines of communication kept open and used. The single individual cannot manage the large animal intensive care patient. The single individual cannot “care” for this type of patient and handle other routines simultaneously, i .e., outpatients, elective cases, personal schedules, and interruptions.

Select ion of the surgeon may be a preoperative consideration. Wi l l the case be handled by a member of the house staff or by the chief of the service? The common standard castration of a young, healthy colt can be bungled by a beginner and s t i l l heal well. However, the aged, parasitized brood mare on winter pasture with strangulated bowel from a pedunculated lipoma needs a surgeon with technical experience, judgment, and fore- thought about supportive treatment in order to increase her chances for survival. History and Physical Examination:

A complete history and thorough physical examination are the beginning and frequently the end of a pre-surgical evaluation of the large animal patient. Although we may be weary of the often repeated, time worn cliches about the importance of a history and physical examina- tion, they are the very essence of it all. Our best

diagnostic tool is ourselves! The signalment can alert the surgeon to

special problems requiring preoperative investi- gation or consideration. Geographic location, breed, and age can be very revealing. It may be difficult to identify a specific number of years beyond which a horse or cow is considered aged. Foals are probably better surgical risks regarding such things as healing potential and postopera- tive hazards but are definitely greater anesthetic risks than adult horses. Also, they suffer from in fect ious diseases and parasi t ism more frequently. Surgery of the aged horse is often for an age-related disease. Except for valuable breeding animals, natural selection and agri- business reduces or eliminates the age problem for food animals.

If worth taking at all, the history should be detailed. To be sure, there are all degrees of detail, with a standard castration or simple umbilical hernia at one end of the spectrum and an acute abdominal catastrophy at the other end. The owner’s complaint dictates the line of questioning but it cannot stop there.

Specific questions about previous coughing, nasal discharge, febrile episodes, colic, the travelling schedule, the worming program, or the consistency of the feces can be very revealing. A horse that has just been on the show circuit may be incubating influenza. Inhalation anesthesia and influenza combined may result in pneumonia and pleuritis. A thin, rough-looking foal recently recovered from strangles requires special ef for ts to ident i f y a l inger ing endocarditis or other atypical forms of this disease. The race horse under stress with inter- mittent spasmodic colic or feces of cow-pile consistency may be a salmonella carrier. Salmonellosis and surgery, any surgery, are a devastating combination, devastating to the patient and to the surgeon. The importance of detecting a swamp fever suspect needs no ramification. In other words, present or previous illnesses may reflect on recoverability.

The history of drug use i s very pertinent to the large animal surgical patient. The continuous use of steroids, phenylbutazone, or antibiotics can create special problems. Parenteral as well as oral antibiotics can alter the intestinal bacteria flora and contribute to the salmonel- losis problem. Phenylbutazone has not been reported to cause blood dyscrasias in animals as have been identified in man. But, the history of i t s use in the surgical patient should be a matter of record.

The Thoroughbred and Standardbred present- ed for joint surgery must be free of intra-articu- lar steroids for the joint in question. The great mobility of these animals with frequent changes

35

of owners, trainers, and veterinarians can make it difficult, and occasionally impossible, to establish the "steroid status" of a joint. In addition to the so-called steroid joint which may have an unfavorable prognosis for surgery, recent intra-articular injection of steroids can inhibit healing and reduce the patient's resistance to infection. There can be no "taking chances" here. If in doubt about the steroid sta- tus, postpone surgery for 60 days from the time the history is certain.

The large, muscular Quarterhorse can be affected with muscle heat buildup (3-4 inches of edema) post-anesthesia azoturia, and post- operative limb paralyses more frequently than any other class of horse. For many of the azoturia cases, the owner can acknowledge previous attacks of tying-up. If the history i s suggestive, a creatine phosphokinase (CPK) and glutamic oxalocetic transaminase (SCOT) should be included with the preoperative laboratory studies. A CPK above 120 I.U. and an SCOT above 300 sigma units must be regarded with suspicion. Such information may not alter the surgery schedule or modify the anesthetic and restraint procedures (wh ich should be preventive in nature); but, it i s helpful in establishing the operative risk and communi- cating this to the owner and to the surgical team.

Finally, to protect the owner's financial invest- ment, the insurance status of the patient must be determined. Most livestock insurance agencies are cooperative and grant permission for elective surgery providing they have been informed. Wi th the exception of emergency surgery, failure to obtain permission, which usually includes payment of an extra premium, wi l l void the insurance. Physical Examination:

Surgeons are always in a hurry; they have an intense interest in the problem at hand and frequently fail to examine the whole animal or even the whole system involved. The real purpose of a pre-surgical examination i t to discover unsuspected lesions or conditions which may require modification, postponement, or even abandonment of an anticipated operation. Speaking of modification, how many veterinarians have dropped a colt for routine castrat ion and discovered an abdomina l cryptorc h id?

If general anesthesia is to be used, there are no distinctions for elective surgery versus emergency surgery or for routine surgery versus special surgery. The animal i s placed under the same set of anesthetic conditions regardless of the operative procedure. For this patient, every body system deserves attention. Organs that

carry out regulatory functions must be in working order; brain, lungs, liver, kidneys, endocrine glands, each must be evaluated, even if in only a superficial or cursory fashion.

The cardiovascular system deserves special attention, particularly in the horse. Heart sounds in the horse can be so variable under normal physiologic conditions, under the influence of preanesthetic drugs, or with disease that it takes considerable experience or special training to make meaningful interpretations. However, the presence of a systolic murmur in a horse in shock may ind icate impend ing cardiac fa i lure. Occasionally, atrial fibrillation and/or endo- carditis can be identified in a horse presented for some other, unrelated surgical disease. An irregular ventricular rhythm associated with a pulse deficit, in an otherwise normal horse, is indication for an ECG as a part of the pre-surgical evaluation.

A cardiac murmur associated with a low-grade fever and history of strangles is indicative of endocarditis. Although there are no specific electrocardiographic findings for endocarditis, an ECC should also be performed for these cases in order to identify an associated cardiac conduction defect. This i s not to suggest that an ECC be used for every horse with an incomplete heart block, split first heart sound, or other variation of normal. But, for selected cases, like the SCOT and CPK, the ECG can help establish the operative risk.

Many veterinarians doing equine surgery receive Thoroughbreds and Standardbreds as referral cases from racetrack practitioners. The animals frequently arrive wi th a specific compla in t about a speci f ic joint and accompanying radiographs. It is very important to examine all 4 legs of this race horse, i.e., the whole system. It may be prudent to x-ray all the lumps and bumps on this horse to make certain there is only one surgical disease. It would be unfortunate to operate for a sesamoid fracture in one leg and be completely unaware of a splint fracture, carpal chip, or other surgical disease elsewhere in the same horse. Owners and trainers expect a prognosis for the future racing performance of these animals. They are concerned about the economics involved. If the costs are to be higher or the results less favorable than originally anticipated, these people need to be so informed. A complete examination of the musculoskeletal system aids in establishing a complete prognosis. Oftentimes the decision i s to go ahead with surgery even though other problems have been identified. Laymen readily accept less than optimal results from surgery, or from the horse when the animal returns to

36

racing, if they have been prepared for them. Lastly, the physical examination findings must

be properly recorded. Although large animal surgeons are not as likely to operate on the wrong patient, as has occurred in small animal clinics and human hospitals, they have been known to operate on the wrong leg or the wrong side of the correct leg. Lesions must be measured with a caliper, a ruler, or a photograph for future reference. This should be a routine pre-surgical habit, even an obsession. Body weight itself is a good example. A recorded pre- operative body weight i s probably the one best index for following the postoperative nutritional status and recovery of the large animal patient. Daily weight measurements are extremely valuable when large volumes of fluid are being lost and replaced. Marked fluctuations, 30 to 700 pounds a day, are due largely to variations in body water content.

liming: Except for l i fe-saving procedures -

tracheotomy, Caesarian section, control of hemorrhage, first aid for the open chest or abdomen - every large animal surgical patient should be given a basic pre-surgical evaluation and be allowed to adjust to the hospital environ- ment before being additionally stressed with surgery. Wi th man, physicians have always been concerned about the emotional preparation of their patient. Wi th horses, surgeons must be cognizant of the possible detrimental effects of racing stress and transportation fatigue. Wi th food animals, every large animal practitioner is keenly aware of the effects of frenzy and heat exhaustion.

Fractures are non-elective surgeries but not necessarily emergencies. Temporary splints like a Robert Jones dressing do permit safe postpone- ment of surgery for up to 24 hours in selected cases. This is valuable time to treat shock, permit some hospital adjustment of the patient, do a complete radiographic study of the injury, plan a precise surgical approach, and obtain the necessary help.

Surgery for an abdominal catastrophy is emergency and usually lifesaving in nature. But, the restlessness of a horse in shock can be easily confused with continuous abdominal pain. For such cases, surgery should be postponed, up to several hours, in order to establish fluid therapy and get a “headstart” wi th reconstitution of the blood volume. Additional t ime wil l permit the establishment of an accurate diagnosis and a positive indication for surgery. It i s unfortunate to perform abdominal surgery on a horse with septic shock, salmonellosis, arsenic poisoning or o ther systemic disease tha t can cause

symptomatic colic. For the abdominal catastrophy, the rapid ad-

ministration of large volumes of fluid are necessary and life-saving initially. But, the preoperative build-up of the patient i s best carried out by slower rates of administration. Fluid and electrolyte imbalances may have developed over a period of many hours or several days. A similar length of time may be required to repair them. Any permissible time delay of surgery wi l l permit better physiologic preparation of the patient and improve the chances for a successful outcome.

Al l elective surgery patients should be admitted to the hospital the day before surgery, especially if transported long distances. This type of t iming wi l l help the surgeon as well as the animal. The animal can be held off feed. Preoperative preparation including grooming, removing shoes, trimming feet, and clipping the surgery site can be carried out before anesthesia. To do these mundane things as part of the transoperative period is negligent planning.

In contradistinction, prolonged periods of preoperative hospitalization are to be avoided. I t is virtually impossible to congregate horses without experiencing periodic outbreaks of influenza. Salmonella organisms and other bacterial opportunists have a predilection for the stressed surgical patient. Surgical clinics with a large patient volume and overcrowding should make every effort to minimize or eliminate delays in the surgery schedule in order to help prevent colonization of the preoperative patient with a pathogen.

Laboratory Tests: The use of laboratory tests during the pre-

surgical evaluation of a large animal patient wi l l vary wi th everything from the condition of the animal to the practice situation of the surgeon. I t has been said that a history and physical examination are good, as far as they go, but there are shortcomings of patient evaluation without laboratory tests. To be sure, without test results there are no objective facts. The patient may be unusual; clinical evaluation can be erroneous, even for the experienced clinician. Without test results there are no objective means for monitoring response to treatment. This would appear to be the most valid reason for establishing a pre-surgi cal cl i n icopat hologic baseline; not only to determine where the patient should be going but to know where it has been.

Perhaps i t i s axiomatic that every laboratory test should be requested on the basis of a clinical indication. If a surgeon has been conscientious about the history and physical exam, he should

37

not be criticized for "flying by the seat of his pants" if in his judgment no preoperative laboratory tests are indicated. After all, the surgeon is first of all a clinician, a medical specialist that performs surgery. However, in the hospital setting, the minimum routine should be something more than no tests at all.

Clinicopathologic study of the equine patient scheduled for an elective surgery should include a complete blood count (CBC), total plasma protein, and fecal examination. For the very young, or older horse, the more important should be the caution to do the tests in the first place and secondly, to make careful interpreta- tions. Otherwise, no distinction for age alone is necessary. This composite of tests adds "objec- tivity" to the clinical findings and selects those cases that may require additional pre-surgical attention, be that treatment for internal parasites, a blood transfusion during the preoperative or transoperative period, or a more elaborate laboratory study.

Many horses, particularly foals, may be clinically normal but have an elevated white cell count (WBC). A WBC above l2,OOO/mm3 should be viewed with suspicion. These animals should receive additional scrutiny for the detection of a deep-seated infection. Postponement of surgery for an additional day or two may be wise in the event a disease is in the incubation stage. If nothing else, the CBC should be repeated in 24 to 48 hours in order to rule out the effects of excitement, recent transportation, or laboratory error. Regardless of the variations known to occur with exercise, excitement, the breed of horse, the level of training or condition, and steroid therapy, a CBC i s s t i l l the series of tests for which normal equine values are best established and correct interpretations most accurately made.

Total protein i s performed with a refracto- meter using plasma from the microhematocrit tube. Total protein i s used as a survey test for the nutritional state of the patient, the functional state of the liver, and t o evaluate hydration in the presence of anemia. Again, to add "objectivity" to the clinical impressions. Values below 5.5 gm.% or above 8.0 gm.% are signals for more careful evaluation of the patient.

The presence of internal parasites has little or no bearing on the preoperative status of most large animal patients for which other findings are within normal limits. However, it i s not uncommon to encounter horses with low hemoglobin levels from stables with no established parasite control program. If the hemaglobin i s below 12 gm.%, elective surgery should be postponed until a reason for the anemia i s established and corrected. Fecal

examination can be performed routinely simply as the first step in identifying a cause for anemia if such is present.

Clinicopathic study of the non-elective or emergency surgical patient in shock must be complete and detailed. Determining the severity of, and correcting, fluid and electrolyte imbalances requires a physiologic approach using a battery of tests. These tests must be performed in series, even as frequently as every 15 to 30 minutes, in order to establish the rate of deterioration of a patient or its response to therapy.

A single test alone is useless because of well known extraneous influences and the wide ranges of normal. The desirability of 9 tests has been established in order to determine the precise fluid and electrolyte status of an equine patient; PCV, total protein, BUN, sodium, potassium, bicarbonate, pH, p02, and pC02. Application of this entire battery of tests in each case is probably economically prohibitive and simply impractical in most situations. However, an abbreviated series of tests is essential to the well-being of the patient and justified in any practice situation where major equine surgery is performed.

Minimum laboratory data for the non-elective or intensive care patient must include CBC, total protein, and blood HCO3 (or total C02). Acidosis is probably as deleterious over a short period of time as any other single metabolic defect, including hypoxia. Blood gases and bicarbonate give the best reflection of this but a total C02 alone i s the bare minimum. A convenient field kit is available for this.*

Regarding electrolytes, pre-surgical equine colic cases are usually near normal but require careful monitoring and adjustments postopera- tively. A preoperative serum potassium is advisable for patients that have been off feed for any period of time and as a baseline for later reference.

Serum enzymes have been mentioned. There is no reason to consider such tests as CPK and SCOT as routine but their selected use does have a place. To be sure, there is a grey zone between high normal values and significant elevation for these tests. The values must be interpreted in light of the history and physical findings.

Liver dysfunction in the horse is usually made apparent by history and physical examination. A history of unexplained fever, anorexia, toxemia, weight-loss, or icterus are indications for liver function studies. Most of these cases are presented as medical patients rather than surgical patients. However, the subacute or chronic equine infectious anemia horse may be 'Harleco, Philadelphia, Pa. 19143

38

presented for surgery and does not make a good combination wi th anesthesia. An immunodiffu- sion test (Coggin’s test) need not be considered routine but complete failure to use the test as a pre-surgical evaluation may be unwise. The author encounters about 1 animal in 500 presented for surgery that is suspicious and for which the test is performed. Serum enzymes are usually normal in these patients.

Sorbitol dehydrogenase (SDH) appears to be a liver specific enzyme in the horse but is primarily useful for acute disease. Levels of 250 I.U. are suspicious and 400 I.U. and over significant. Veterinary clinical pathologists would appear to be on the threshold of developing new tests (SDH, glutamic dehydro- genase, and coagulation tests) and sophisti- cating presently available tests for application in the horse.

The use of bleeding tests as a matter of routine is questionable for the horse. Regardless of the laboratory technique used (Lee White, capillary tube), there i s a wide variation of normal for both coagulation time and bleeding time. These times are naturally prolonged in the horse, apparently because of a normally low level of antihemophilic globulin. It is important to be attentive to the hemoglobin because of the clinical impression that anemic horses have a tendency to bleed.

Fortunately, the presence of natural bleeding diseases in either the horse or food animals i s relatively rare. Only several isolated cases of hemophilia have been reported in the horse and these have been identified by the presence of overt clinical signs. Dicumarol poisoning was only occasional in the horse during that period of time when i t was common in food animals. Now it i s even less frequent because of the education of farmers about spoiled sweet clover. A complete history with attention to the feeding program should be suitable precaution. Horses with subacute swamp fever or established liver disease have definite bleeding tendencies, However, the possibility of missing these cases with a careful history and physical examination i s remote.

Laboratory studies for cattle have been over- looked u n t i l recent t imes. Improved understanding of the metabol ic changes associated with left abomasal displacement (LDA) has resulted in a greater attention to the cow‘s fluid and electrolyte needs.

Because of the less frequent use of general anesthesia in cattle, there i s probably no need for a minimum number of tests. The selection of tests i s based on the surgical disease in question. In an academic practice, a CBC, urinalysis, and SDH should be utilized. The high prevalence of

infection in the cow with an LDA (metritis, mastitis) signals the value of a CBC. The SDH can be helpful in evaluating the severity of liver damage in these cases; values of 1,000 I.U. are significant. When the level reaches 4,000 I .U., there may be reason to expect a stormy recovery with persistent ketosis.

The urinalysis is the simplest, cheapest, and probably the most valuable test in the cow. It gives a rough but useful measure of the severity of ketosis, the severity of dehydration, and the metabolic status of the patient. However, interpretation can be difficult. Cows with an LDA may have an acid urine in the presence of metabolic alkalosis. Conclusion:

The assessment of the operative risk i s the ultimate art in the practice of surgery. When the history and physical examination have been evaluated and when the clinicopathologic results are available, the final assessment of the physiologic reserve of a patient to withstand surgery i s subjective. It i s based on the experience of the subjective surgeon derived as objectively as possible but ultimately has to be subjective.

REFERENCES

1. Allen, B.V., and R.K. Archer: A Blood Coagulation Test (Normotest) as Another Measure of Liver Function in the Horse. Eq. Vet. Jour.. 4, No. 4 (1972): 21 7-222. 2. Cole, W.H , and R . M Zollinger. Textbook of Surgery. 9th Ed., Appleton-Century-Crofts, New York, 1970. 3. Donawick, W.J. . and J .T . Alexander: Laboratory and C l in ica l Determinations in the Management of the Horse with Intestinal Obstruction. Proc. Am. Assoc. of Equine Practitioners, 16th Annual Meeting (1970): 343-354. 4. Kaneko, J.J., and C.E Cornelius: Clinical Biochemistry of Domestic Animals. 2nd Ed., Academic Press, New York. 1971 5. Simeone, F.A.. Davis-Christopher Textbook of Surgery, The Biological Basis of Modem Surgical Practice. 70th Ed., W.B. Saunders Co., Philadelphia, 1972. 6. Tasker. J.B.: Fluid Therapy in Equine Medicine. Unpublished material. Am. Assoc. of Equine Practitioners, Dec. 5, 1971

METABOLIC MANAGEMENT OF THE HORSE WITH ACUTE ABDOMINAL CRISIS*

William 1. Donawick, D. V . M., Ph. D. t Diplomate, American College of Veterinary Surgeons

Modern principles of surgery place high priority on the provision for the metabolic needs of the patient as an adjunct t o surgical management. Few dispute the benefits derived from attention to the patient’s needs for water, electrolytes, acid-base balance and energy. Yet, there remain those who shun i t s use altogether or, equally disturbing, reserve such support for the critically ill patient in whom the need for surgery is far beyond debate.

to r . Donawick is Associate Professor of Surgery, A Diplomate of the American College of Veterinary Surgeons and recipient of U.S. Public Health Service Career Development Award 1 K4 HL70. 589 from the National Heart and Lung Institute.

Pretoriuskop, South Africa, 10 August 1974. ‘Originally presented at the First International Equine Veterlnafy Conference,

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