Acetate and hypercalciuria during total parenteral nutrition.

Hypercalciuria and negative calcium balance are complications of total parenteral nutrition (TPN). Because metabolism of the TPN formula generates an acid load that can induce hypercalciuria, we evaluated the effect of supplementing the formula with acetate. In a randomized crossover study six patients on continuous and six on cyclic TPN received no added acetate or 160 mmol acetate/d replacing 160 mmol chloride/d for 3 d each. Blood and urine measurements were obtained on day 3 of each formula. Acetate, which is metabolized to bicarbonate, increased blood pH and decreased renal acid excretion. Urinary Ca decreased in every patient from 422 +/- 63 to 240 +/- 46 mg/d (10.5 +/- 1.6 to 6.0 +/- 1.4 mmol/d) and from 468 +/- 68 to 285 +/- 54 mg/d (11.7 +/- 1.7 to 7.1 +/- 1.3 mmol/d) during continuous and cyclic TPN, respectively. Filtered Ca load decreased slightly whereas renal tubular Ca reabsorption increased significantly with acetate. Serum parathyroid hormone, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and urinary cyclic AMP were not different.

Whole-body protein turnover in adult hemodialysis patients as measured by 13C-leucine.

Muscle wasting may occur in patients with chronic renal failure (CRF). To determine whether this is due to a decrease in the synthesis or an increase in the breakdown of muscle protein, we evaluated postabsorptive whole-body protein breakdown, oxidation, and synthesis rates at steady state during a primed, continuous infusion of 13C-leucine. This was done in seven subjects on chronic maintenance hemodialysis (MHD) and in seven normal control subjects. The protein breakdown rate in MHD was not different from that in controls (103 +/- 19 and 106 +/- 19 mumol leucine.kg-1.h-1, respectively). In MHD, however, the protein oxidation rate was 43% greater than that in controls (20 +/- 6 and 14 +/- 4 mumol leucine.kg-1.h-1, p less than 0.05), whereas net protein synthesis was less (p less than 0.05). Reduced net synthesis and increased oxidation rates of protein in the postabsorptive state may therefore contribute to the muscle-wasting syndrome in patients with CRF.

Skeletal muscle function in chronic renal failure: an index of nutritional status.

To determine whether skeletal muscle function testing (SMF) provides an index of nutritional status in patients with chronic renal failure (CRF), two groups with comparable CRF were studied. In 48 well-nourished (WN) and 17 malnourished (MN) patients with stable CRF, and in 33 WN nonazotemic controls, adductor pollicis function was assessed. The force at 10 Hz was expressed as a % of force at 100 Hz (F10/F100), and maximal relaxation rate (MRR) as % force loss/10 ms. Standard nutritional assessment was also performed. The WN group was not significantly different from controls for either F10/F100 or MRR. The F10/F100 of the MN group was significantly greater than either the WN group or controls (p less than 0.001), while MRR was less (p less than 0.001). Significant malnutrition by conventional parameters was shown in patients with abnormal F10/F100, and also in patients with abnormal MRR. Hence, SMF as described is unaffected by azotemia, and provides a functional measure of nutritional status in CRF.

Humoral hypercalcemia complicating adenosquamous carcinoma of the proximal colon.

Hypercalcemia as a complication of carcinoma of the colon is uncommon (1). It usually occurs in the presence of anorectal or rectal carcinoma that metastasizes to the lumbosacral vertebrae (2-4). Hypercalcemia complicating colon carcinoma in the absence of bone metastases--so-called humoral hypercalcemia of malignancy or paraneoplastic hypercalcemia--is rare. Only two such cases associated with adenocarcinoma of the colon (5,6) and two cases associated with adenosquamous carcinoma of the distal colon (rectum and sigmoid) (7) have been reported. We describe the first reported case of an adenosquamous carcinoma of the cecum and ascending colon that was accompanied by severe humoral hypercalcemia. The hypercalcemia was associated with a parathyroid hormone (PTH)-like substance.