The Effect of Disease Severity and Comorbidity on Length of Stay for Orthopedic Surgery in Rheumatoid Arthritis: Results from 2 UK Inception Cohorts, 1986-2012

OBJECTIVE

To examine factors predicting length of stay (LoS) for orthopedic intervention in rheumatoid arthritis (RA).

METHODS

LoS for orthopedic intervention was examined in 2 consecutive, multicenter inception cohorts: the Early RA Study (n = 1465, 9 centers) and the Early RA Network (n = 1236, 23 centers). Date, type of orthopedic procedure, and LoS were recorded and validated against national data, the UK National Joint Registry, and the UK Hospital Episode Statistics database. Clinical, laboratory, and radiographic measures and comorbidity recorded at baseline and annually were examined for their predictive power on LoS using regression analysis.

RESULTS

A total of 770 of 2701 patients (28.5%) had 1602 orthopedic interventions: 40% major (mainly total hip/knee replacements), 24% intermediate (mainly hand/wrist and ankle/foot surgery), and 16% minor (mainly soft tissue surgery). Median (interquartile range) LoS was 8 (5-13), 3 (1-5), and 1 (0-2) days for major, intermediate, and minor interventions, respectively. Older age predicted longer LoS (p < 0.001) whereas a more recent operation year predicted shorter LoS (p < 0.001). Markers of active disease, namely low hemoglobin, high Health Assessment Questionnaire, and high Disease Activity Scores in the first year all predicted longer LoS for all types of surgery (p = 0.001, p < 0.001, p = 0.05, respectively). Presence of 1 or more major comorbidities predicted longer LoS (p < 0.001).

CONCLUSION

Comorbidity and standard clinical and laboratory markers of disease activity affect the LoS for orthopedic surgery in RA, which has important clinical and economic implications, providing a target for improving patient outcomes.

SIGNIFICANT CHANGES IN URINARY NITROGEN

Given healthy dogs fed abundant iron and protein-free or low protein diets with sustained anemia and hypoproteinemia, we can study the capacity of these animals to produce simultaneously new hemoglobin and plasma protein. Reserve stores of blood protein-building materials are measurably depleted and levels of 6 to 8 gm. per cent for hemoglobin and 4 to 5 gm. per cent for plasma protein can be maintained for weeks or months depending upon the intake of food proteins or amino acid mixtures. These dogs are very susceptible to infection and various poisons. Dogs tire of these diets and loss of appetite terminates many experiments. Under these conditions (double depletion) standard growth mixtures of essential amino acids are tested to show the response in blood protein output and urinary nitrogen balance. As a part of each tabulated experiment one of the essential amino acids is deleted from the complete growth mixture to compare such response with that of the whole mixture. Methionine, threonine, phenylalanine, and tryptophane when singly eliminated from the complete amino acid mixture do effect a sharp rise in urinary nitrogen. This loss of urinary nitrogen is corrected when the individual amino acid is replaced in the mixture. Histidine, lysine, and valine have a moderate influence upon urinary nitrogen balance toward nitrogen conservation. Leucine, isoleucine, and arginine have minimal or no effect upon urinary nitrogen balance when these individual amino acids are deleted from the complete growth mixture of amino acids during 3 to 4 week periods. Tryptophane and to a less extent phenylalanine and threonine when returned to the amino acid mixture are associated with a conspicuous preponderance of plasma protein output over the hemoglobin output (Table 4). Arginine, lysine, and histidine when returned to the amino acid mixture are associated with a large preponderance of hemoglobin output. Various amino acid mixtures under these conditions may give a positive urinary nitrogen balance and a liberal output of blood proteins but there is always weight loss, however we may choose to explain this loss. These experiments touch on the complex problems of parenteral nutrition, experimental and clinical.

RAIDING OF BODY TISSUE PROTEIN TO FORM PLASMA PROTEIN AND HEMOGLOBIN : WHAT IS PREMORTAL RISE OF URINARY NITROGEN?

Dogs with sustained anemia and hypoproteinemia due to bleeding and a continuing low protein or protein-free diet with abundant iron will continue to produce much new hemoglobin and plasma protein for many weeks. The stimulus of double depletion (anemia and hypoproteinemia) leads to raiding of body and tissue protein to fill the demand for new hemoglobin and plasma protein. The blood proteins in these experiments take priority over the organ and tissue proteins. This is another illustration of the "ebb and flow" or dynamic equilibrium between organ or tissue protein and blood proteins. The average dog cannot tolerate this drain of double depletion for more than 7 to 11 weeks and during this time may lose 30 to 40 per cent of body weight. Some dogs are much more resistant to this raiding than others. Some dogs show a high blood protein output during every week up to the danger point. With the largest blood protein output one usually observes the most rapid weight loss. For every kilogram of weight loss we observe 50 to 140 gm. blood protein output. The weekly blood protein production ranges from 40 to 66 gm. These experiments make heavy demands on the body protein and we expected to record a "premortal rise" in urinary nitrogen. No such observations are noted, rather a most frugal use of all protein and minimum figures for urinary nitrogen. We suspect that "premortal rise" in many experiments means a terminal infection with the related catabolism of tissue protein and high urinary nitrogen.

THE EFFECT OF dl-METHIONINE, l-CYSTINE, AND dl-ISOLEUCINE ON THE UTILIZATION OF PARENTERALLY ADMINISTERED DOG HEMOGLOBIN : A SUGGESTION FOR DESIGNING THE COMPOSITION OF THE "IDEAL" PROTEIN DIGEST

1. Further observations on the utilization of parenterally administered dog hemoglobin show that oral supplements of dl-methionine and l-cystine improve the efficiency of utilization of hemoglobin N, while a fed supplement of dl-isoleucine alone is without effect. 2. When N-isoleucine is added to a fed supplement of methionine or methionine and cystine, the utilization of parenterally given hemoglobin N is even better than with the sulfur-containing amino acids alone. 3. A suggested approach to the problem of designing the quantitatively "ideal" amino acid mixture lies in the definition of what may be called total organism-amino acid patterns of rat, dog, man, etc. These may vary considerably not only at different developmental stages in a given species, but also certainly from one species to another. 4. Further attempts to detect globin in the peripheral circulation have pointed to the need for a highly specific procedure such as that an immunologic method may offer. 5. Reduced hemin in dog plasma migrates with α₁-globulin and albumin in veronal buffer at pH 8.5 and the colored zones give strong hemochromogen absorption bands.

The metamorphosis of hemoglobin in the bullfrog

1. Tadpole and adult hemoglobin do not differ significantly in molecular weight. The molecular weight of both is in the neighborhood of 68,000. 2. Heme-heme interaction as measured by the value of n in Hill's equation is virtually the same-about 2.8-in both tadpole and adult. 3. There appears to be no significant effect of pH upon the oxygen equilibrium of tadpole hemoglobin, in contrast to large Bohr and reverse Bohr effects in the adult. This is taken to mean that during metamorphosis acid groups of globin become sensitive to the oxygenation of heme by some change in the mode of linkage between heme and globin. 4. The oxygen affinity of tadpole hemoglobin is about seven times as great as that of the adult at pH 6 and twice as great at pH 9.

The hemoglobin of the sea lamprey, Petromyzon marinus

The blood hemoglobin of the sea lamprey presents a curious mixture of primitive and highly specialized properties. Like muscle hemoglobin, it has a molecular weight of about 17,000, and apparently contains a single heme. Its isoelectric point is like that of a typical invertebrate hemoglobin. Its amino acid composition is partly characteristic of invertebrate) partly of vertebrate hemoglobins (Pedersen; Roche and Fontaine). In the present experiments, the oxygen equilibrium curve of this pigment was measured at several pH's. As expected, it is a rectangular hyperbola, the first such function to be observed in a vertebrate blood hemoglobin. Other hemoglobins known to possess this type of oxygen dissociation curve-those of vertebrate muscle, the worm Nippostrongylus, and the bot-fly larva-appear to serve primarily the function of oxygen storage rather than transport. Lamprey hemoglobin on the contrary is an efficient oxygen-transporting agent. It achieves this status by having, unlike muscle hemoglobin, a relatively low oxygen affinity, and a very large Bohr effect. In these properties it rivals the most effective vertebrate blood hemoglobins.

The oxygen equilibrium of the hemoglobin of the eel, Anguilla rostrata

Kawamoto had reported that eel hemoglobin has a hyperbolic oxygen equilibrium function, with n in the Hill equation equal to 1. On the basis of Kawamoto's data and with new measurements, it is shown that the equilibrium function is in fact S-shaped, as in most other vertebrates, and n in Hill's equation equals 1.8.

Hemoglobin patterns in American Indians

Two populations of North Carolina have been analyzed for hemoglobin patterns by paper electrophoresis. Of 534 Cherokee Indians, both mixed and full bloods, all showed normal hemoglobin. Lumbee Indians of less certain ethnic status had 1.7 percent of hemoglobin S, an equal amount of hemoglobin C, and one possible hemoglobin D trait among 1332 bloods studied.