16. Postlethwait, R.W.: Drains and Drainage, in Textbook of Surgety, Ed. by D.C. Sabiston, Jr., W.B. Saunders Co., Philadelphia, PA 1972app 314-317. 17. Pulaski, E.J.: Common Bacterial Infections. W.B. Saunders Co., Philadelphia, PA 1964. 18. Seidenstein, M., Salomons, M.M., Herbsman, H., Shaftan, G.: Evaluation of local antibiotic instillation in extremity wounds. Surg. 68:809-812, Nov 1970.

SELECTED SURGICAL DISEASE STATES WHERE MICROBIOLOGICAL EVALUATION

IS ESSENTIAL

Robert Dixon, B.S., D. V. M. t Diplomate, American College of Veterinary Surgeons

Infections caused by bacterial organisms constitute an important problem i s selected surgical disease states. The surgeon should strive for an early definitive diagnosis based on clinical signs and symptoms, laboratory values, and culture, and antibiotic susceptibility testing. Early diagnosis combined with proper supportive care, basic surgical principles, and appropriate antibiotic treatment will generally improve the therapeutic results obtained. Examples of selected surgical disease states where micro- biological evaluation is essential include septic shock, bacterial osteomyelitis, and infectious peritonitis.

SEPTIC SHOCK Septic shock is a syndrome that i s being

recognized with increasing frequency i n animals. The incidence of septic shock in animals is not known because mortality statistics are notably sparse in the veterinary literature. However, the mortality associated with septic shock in the individual patient may be extremely high. Septic shock may be caused by an overwhelming infection with Gram positive bacteria, Gram negative bacteria or any other agent capable of producing infections, i.e., rickettsiae, fungi , parasites, viruses, etc.

Gram positive sepsis and shock is most commonly caused by: (1) An overwhelming infection with Gram positive organisms such as staphylococcus, !streptococcus, and pneumoncoccus.

(2) By disemination of a potent exotoxin without evident bacteremia [Clostridium perfringens and tetani]

(‘3) Gram positive infections that produce massive fluid losses (Necrotizing fasciitis).’ This type of septic shock i s vasculogenic, in that vasodilatation and hypotension are the chief physiologic manifestations.

tcomparative Clinical Medicine Program, Clinical Research Service, Madigan Army Medical Center, Tacoma, Washington, 98431.

Treatment consists of: (1) Appropriate antibiotics as determined by culture and anti biotic susceptibility when possible. (2) Surgical drainage where indicated (3) Correction of any existing fluid deficit

The response to treatment and survival appears to be substantially better than with Gram negative sepsis.

Gram negative sepsis i s a much more common cause of shock (endotoxic) and death in surgical practice than is Gram positive sepsis. In dogs, in experimental shock, splanchnic pooling of blood causes a secondary hypovolemia. This removes blood from the effective circulation in the cardiovascular system. This form of shock should be classified in the hypovolemic category.

The ability of Gram negative bacteria to cause shock i s apparently dependent on a lipoprotein-carbohydrate complex or endotoxin which is liberated at death from the cell wall of the Cram negative bacteria. * Some authors suggest it may result from a complex interaction of hematologic and immune systems.8

The organisms that most commonly cause Cram negative sepsis and shock are E . coli, Klebsiella sp, Proteus, Pseudomonas, and Bac teroidies.

Clinically, the syndrome in dogs may be recognized as a highly fatal syndrome and may be characterized by acute bloody diarrhea. The intestinal changes appear to be caused by a direct or indirect adverse action of endotoxin, and possibly of the sympathetic reflexes, on the intestinal vasculature.

Endotoxic shock may occur either pre, during, or post surgical manipulation or instrumen- tation. It is most usually associated with a urinary tract infection, peritonitis or GI infections, intra abdominal abscesses, burns, soft tissue infections, chronic indwelling venous catheters and trauma. Other conditions that pre- dispose the patient are serious associated diseases such as Diabetes mellitus, malignan- cies, and liver pathology. Endotoxic shock has occurred following the manipulation of a draining wound.5

The initial response of the dog to experimental injection of €. coli endotoxin i s splanchnic pooling of the blood pressure, decreased venous return to heart and a decrease in cardiac output. 4, 6 Shortly thereafter, the blood pressure rises toward normal and then slowly declines over the next few hours until the death of the animal. Clinically, the dog may also show signs similar to hypovolemic shock. Other clinical

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signs may include, tachycardia, poor capillary refill, muscle weakness, hypothermia, depressed sensorium, decreased urinary output, and hyper- ventilation.

The differential diagnosis of shock i s diff icult in many situations. One must go farther than the clinical picture alone to obtain a definitive diagnosis. Unless blood cultures are obtained almost routinely from patients in whom the etiology of shock is not entirely clear, the diagnosis of bacterial shock wil l be m i ~ s e d . ~ All other sites of infection should be cultured and the antibiotic sensitivity determined. The estab- lishment of a diagnosis of septic shock early enough and supporting the patient until the shock can be reversed may help to reverse the high mortality rate.

In the canine, early signs of bacteremia may be fever and hyperventilation. These signs are possibly a primary response to bacteremia and may precede the usual signs of septic shock several hours to several days. With clinical signs of bacteremia, the clinician should search for the source of infection and begin early treatment.

I t i s not my purpose to discuss shock treat- ment in detail as there are many excellent current works on this subject. However, rule number one in the treatment of shock is to expect it in Gram negative bacteremia and prevent development of hypotension b y correcting deficiencies in plasma volume, serum albumin and erythocyte mass. Sequential steps in the evaluation and therapy of shock include. 8

(1) Rapid examination of the patient including blood status, infection sources, any pus foci, circulatory condition, and adequacy of air intake. (2 ) Careful and extensive co l lec t ion o f specimens for immediate culture, i.e., urine, blood, purulent exudates, etc.

(3) Immediately initiate appropriate parenteral antibiotics.

(4) Monitor central venous pressure, (CVP) urine output and alertness. (5) Restore circulating blood volume. (6) Administer vasoactive and cardioactive agents, i.e., Isuprel, chlorpromazine, Corticos- teroids.

(7) Surgical relief of obstructive lesions and drainage of purulent accumulations.

S U M M A R Y Infection caused by bacterial organisms con-

stitutes an important problem in surgical practice. Bacteremia due to both Gram positive

and Cram negative bacteria i s often complicated by shock.

Frequent antibiotic susceptibility tests and bacterial culture of blood, urine, body fluids, draining wounds or other sources of infection i s an essential adjunct to the proper management of surgical infections which may lead to septic shock.

In combination with current medical and surgical principles of septic shock therapy, two things may help to reverse the high mortality rate, making the diagnosis early enough and supporting the patient until the shock can be reversed

REFERENCES

1 , Shires, T.G., Carrico, C.J. and Canizaro: Shock- Major Problems in Clinical Surgery 13:151 Philadelphia, The W.B. Saunders Co., 1973 2. Lillehei, R.C. and Maclean, L.D.: Physiological Approach to Successful Treatment of Endotoxin Shock in the Experimental Animal. Archives Surgery, 78:464-471, 1959. 3. Brasmer, T.H.: Shock-Basic Pathophysiology and Treatment. 2:2:219-233, Vet Clin of N Am, May 1972. 4. Alican, F., Dalton, M.L., Hardy, J.D.: Experimental Endotoxin Shock. Am J Surg, 103:702, 1962. 5. Matsumoto, T. and Hayes, M.F.: Septic Shock - What to do and When, Consultant, J . Med Consultation, 1973. 6. Duff, J.H., Guillerno, M., and Peretz, D.I.: The Hernodynamics of Septic Shock in Man and in the Dog. Surgery, 58:174, 1965 7. Shubin, H. and Weil, M.H.' Bacterial Shock - A Serious Complication in Urological Practice. JAMA, 1.35350, 1963. 8. McCabe, W.R.. Gram negative Bacteremia - Seminar on Gram negative Infections. Washington University School of Medicine. Schering Corp., 1973.

O S T E O M Y E L I T I S

Osteomyelitis denotes infection in bone. It may be present in both the acute and chronic forms. Osteomyelitis may occur from direct contaminat ion o f bone or may be of hematogenous origin. This disease may be caused by either bacterial or mycotic agents. This paper wi l l deal specifically with bacterial osteomyeli t i s .

The most common bacterial organisms isolated from cases of osteomyelitis are staphylococcus sp., streptococcus sp., and coli- forms.

The acute form of bacterial osteomyelitis originates in the medullary cavity, involves large areas of the affected bone, and is characterized by sequestration and lysis. 1 It may be caused by contamination of fractures, improper surgical technique or seeding via the hematogenous route.

Chronic osteomyel i t is usual ly fo l lows injections which penetrate to the periosteum or deeper, or from deep puncture wounds.

Bacterial osteomyelitis usually involves the metaphysis of one bone. Osteomyelitis of the maxilla or mandible may result from severe periodontal disease.

The diagnosis of osteomyeltis should be based on (1) clinical signs, (2) radiographic studies and ( 3 ) culture of the causative organisms.

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