Stewart used physicochemical principles of aqueous solutions to develop an understanding of variables that control hydrogen ion concentration (H+) in body fluids. He proposed that H+ concentration in body fluids was determined by PC02, strong ion difference (SID = sum of strong positive ion concentrations minus the sum of the strong anion concentrations) and the total concentration of nonvolatile weak acid (&ot) under normal circumstances. Albumin is the major weak acid in plasma and represents the majority of A , .These 3 variables were defined as independent variables, which determined the values of all other relevant variables (dependent) in plasma, including H' . The major strong ions in plasma are sodium and chloride. The difference between Na+ and CI-may be used as an estimation of SID. A decrease in SID below normal results in acidosis he purpose of this article is to review the basic T principles of Stewart's approach to acid-base chemistry,'-3 to show how these principles can be easily applied clinically, and to show the clinical usefulness of this approach in the evaluation of the acid-base status in a variety of species and disease states in an emergency or critical care setting. Principles of Stewart's Acid-Base ChemistryStewart's quantitative approach to acid-base chemistry provides a mathematical explanation of the relevant variables that control H+ in body fluids and their interactions. The approach treats body fluids as a system that contains multiple interacting constituents. The Henderson-Hasselbalch approach to evaluating acid-base status considers the interactions of only a few variables in the system, such as pH, PC02, and bicarbonate, whereas Stewart considers the interactions among more variables and allows one to identify the variables that control H+. 1-3Stewart uses 3 physical laws of aqueous solutions to write equations that describe the interactions among the variables in the system. These laws are (1) the maintenance of electrical neutrality (positively charged ion concentrations equal the negatively charged ion concentrations), (2) the satisfaction of the dissociation equilibria for weak electrolytes (partially dissociated when dissolved in water), and ( 3 ) the conservation of mass. Strong electrolytes are completely dissociated in water so there is no equilibrium equation to consider. Equations that satisfy the physical (increase in H+) and an increase in SID above normal results in alkalosis (decrease in H+). Unidentified strong anions such as lactate will decrease the SID, if present. Equations developed by Fencl allow Stewart's work to be easily applied clinically for evaluating the metabolic (nonrespiratory) contribution to acid-base balance. This approach separates the net metabolic abnormality into components, and allows one to easily detect mixed metabolic acid-base abnormalities. The Fencl approach provides insight into the nature and severity of the disturbances that exist in the patient. Sodium, chloride, protein, and unidentified anion derangements may contribute to the...

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A llama, a miniature horse, and a miniature donkey with severe bilateral congenital flexural deformities of the metacarpophalangeal and metatarsophalangeal joints were treated successfully by arthrodesis with dynamic compression plating or external skeletal fixation. The flexor tendons were more taut than the suspensory ligaments and were transected. In the llama, the suspensory ligament was transected, and overcorrection caused ischemic necrosis of one distal limb and subluxation of the other fetlock joint. In the horse and donkey, the suspensory ligament was preserved and wedge osteotomy was performed to correct the deformity.

The accuracy of diagnoses based on examination of frozen sections was determined by comparing the results to those obtained by examination of tissues prepared using conventional methods (formalin fixation, paraffin-embedded tissue). One hundred ninety-four specimens were examined using the frozen section technique; 37 were examined to confirm a tentative diagnosis or to document lymph node metastasis and the remainder were examined to diagnose an unknown pathologic process. Of the 194 specimens examined, an accurate, specific diagnosis was obtained in 161 (83%); in 19 (10%), the pathologic process was correctly identified, but a specific diagnosis was not obtained; and in 2 (1%) the diagnosis was deferred. The remaining 12 (6%) were incorrectly diagnosed by the frozen section technique. When the number of specimens in which a specific diagnosis was obtained was combined with the number of specimens in which the pathologic process was correctly identified, the overall accuracy rate of the frozen section technique was 93%. There was no difference in the accuracy of the frozen section technique based on the reason for submission of the sample, source of tissue submitted, or the type of pathologic process (i.e., inflammatory or neoplastic). Of the 12 incorrect diagnoses, 4 (33%) were because of sampling errors and 8 (67%) were caused by interpretation errors.(ABSTRACT TRUNCATED AT 250 WORDS)

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SummaryLong-term clinical and radiographicresponse to surgical and conservativemanagement of 22 dogs with fragmentedsesamoids was evaluated. Mean follow-up was 3.6 years (range = 3 monthsto 11.0 years).Initial (retrospective) and follow-up(prospective) radiographs of the affectedpalmar sesamoids and associatedmetacarpophalangeal joints were evaluatedusing a graded scoring system. A lameness evaluation and physicalexamination were performed at followupin a blinded manner. In addition,owners were asked to complete a questionnaireregarding their pet’s thoraciclimb lameness.There was not any difference betweengroups (sesamoidectomy, conservativemanagement, incidental finding)in age at onset, duration of lamenessprior to therapy, body weight at treatment, time to follow-up, number ofaffected joints, nor owner perceptionsof whether they thought the lamenessimproved, resolved, or recurred, andwhether or not they were pleased withthe outcome.Sesamoid fragmentation treated bysesamoidectomy resulted in significantlygreater progression of radiographicchanges that were consistentwith degenerative joint disease.Chronic lameness resolved or improvedto the point of owner satisfactionwith conservative therapy in most cases. Continued lameness, or recurrent,although improved lameness associatedwith heavy activity, occurred followingsurgical extirpation of the affectedsesamoids in many cases. Given thesefindings, a more conservative approachto the treatment of chronic lamenessassociated with sesamoid fragmentationmay be warranted.Long-term clinical and radiographic response to surgical and conservative management of 22 dogs with fragmented sesamoids was evaluated. Mean follow-up was 3.6 years. Sesamoid fragmentation treated by sesamoidectomy resulted in significantly greater progression of radiographic changes that were consistent with degenerative joint disease. Chronic lameness resolved or improved to the point of owner satisfaction with conservative therapy in most cases. Continued or recurrent lameness was common following sesamoidectomy. Conservative therapy should be attempted prior to sesamoidectomy for dogs with chronic lameness associated with palmar metacarpophalangeal sesamoid fragmentation.