Dietary citrate and plasma ionized calcium: Implications for platelet donors.

BACKGROUND: Platelet donors receive 40 mmol or more of IV citrate anion during donation. When plasma ionized calcium ([Ca2+ ]) falls by ∼20%, half of the donors report symptoms of hypocalcemic toxicity. Citrus juices contain clinically relevant amounts of citrate anion. We asked whether citrus juice can lower [Ca2+ ] thus potentially contributing to hypocalcemic toxicity. METHOD: Six volunteers were given 20.4 mmol of citrate anion as grapefruit juice or orange juice. Capillary blood obtained by fingerstick was analyzed for [Ca2+ ] using an iSTAT point-of-care blood analyzer. [Ca2+ ] was measured at baseline and then 30, 60, 120, and 180 minutes after drinking juice. Subjects were tested with the alternative juice on a subsequent day. The outcome measure was the percent change in plasma [Ca2+ ] from baseline. RESULTS: [Ca2+ ] fell -2.2% to -11.5% in four of six subjects 30 minutes after drinking grapefruit juice. The effect persisted up to 3 hours. [Ca2+ ] fell -2.1% to -12.2% in four of six subjects 30-60 minutes after drinking orange juice. The effect abated after 2 hours. We could not correlate gender or body surface area to these findings. SUMMARY AND CONCLUSIONS: Citrus juice may lower [Ca2+ ] for 2-3 hours. This could add to the effect of IV citrate infusion during platelet donation, thus worsening the expected fall in [Ca2+ ]. This, in turn, would likely increase the rate and severity of hypocalcemic toxicity. It is prudent to advise platelet donors to avoid high citrate anion beverages, such as citrus juice, for at least 4 hours prior to donation.

A liquid calcium+vitamin D3 supplement is effective prophylaxis against hypocalcemic toxicity during apheresis platelet donation.

Hypocalcemic toxicity, because of return of citrate anion to the donor, is the major toxicity of apheresis platelet donation. Oral calcium carbonate, given prophylactically at the start of donation, has shown limited ability to alleviate this toxicity. We examined whether repeated prophylactic doses of calcium carbonate, or of a liquid preparation containing calcium citrate, calcium phosphate, and vitamin D3 , would be more effective at preventing symptoms of hypocalcemic toxicity. Symptoms were reported by 48% of donors who received no prophylaxis and 60% of donors who received 1000 mg of oral calcium carbonate at the start of, and every 20 minutes during, donation (P = 0.711). Only 19.2% of donors who received the liquid preparation (1000 mg calcium, 1000 IU vitamin D3 ) reported symptoms (P = 0.040 versus no prophylaxis, P = 0.039 versus calcium carbonate). This difference was not because of gender, weight, age, or blood volume of the donor. Neither calcium preparation prevented a measurable fall in plasma ionized calcium during donation. We conclude that liquid calcium citrate/calcium phosphate/vitamin D3 provides effective prophylaxis against hypocalcemic toxicity during platelet donation, however it does not prevent a fall in plasma ionized calcium.

Physiological measurements corroborate symptomatic improvement after therapeutic leukapheresis in a pregnant woman with chronic myelogenous leukemia.

Therapeutic leukapheresis can control the white blood cell count (WBC) of pregnant women with chronic myelogenous leukemia (CML) who have hyperleukocytosis without leukostasis. The medical justification for this treatment has not been objectively documented. We report a 27-year-old woman, diagnosed with CML at 10-week gestation, who developed severe dyspnea on exertion. A workup that included chest CT and echocardiography with a bubble study detected no cardiopulmonary pathology to explain her symptoms, and thus she was referred for leukapheresis. Prior to her first leukapheresis, which lowered her WBC from 154 × 10(3) /µL to 133 × 10(3) /µL, her oxygen saturation (SpO2 ) on room air decreased from 98 to 93% during 100 feet of slow ambulation and she was dyspneic. Just after the leukapheresis, her dyspnea on exertion was much improved and her SpO2 remained at 98% with repeat ambulation. Spirometry and lung volume studies obtained before and after her first leukapheresis demonstrated 32 and 31% improvements in forced vital capacity and forced expiratory volume in 1 s respectively, a 25% increase in functional residual capacity, and a 142% improvement in expiratory reserve volume. Residual volume decreased by almost 20%. Three times in a week, leukapheresis was continued until her WBC was controlled with interferon α-2b approximately 4 weeks later. Her dyspnea had completely resolved. She gave birth by elective caesarean section to a healthy boy at 32 weeks. Corroboration of symptom relief by leukapheresis with physiological data may justify such treatment in pregnant patients with CML. J. Clin. Apheresis 31:393-397, 2016. © 2015 Wiley Periodicals, Inc.

Automated red blood cell exchange for acute drug removal in a patient with sirolimus toxicity.

Sirolimus is an immunosuppressant used to prevent graft versus host disease in allogeneic hematopoietic stem cell transplant recipients. It has a large volume of distribution (12 ± 7.5 l/kg) and within the intravascular space ∼95% of it is bound to red blood cells. Because of potential toxic effects at high trough levels, therapeutic drug monitoring is recommended for sirolimus. We present a case of severe hepatic dysfunction due to Hepatitis B and sirolimus toxicity, in a 51-year-old male stem cell transplant recipient. An automated red cell exchange decreased his blood sirolimus level from 22.6 to 10.3 ng/ml (55% reduction) and improved his liver enzymes. Re-equilibration of sirolimus from other compartments to the blood necessitated a series of four red cell exchanges, after which the sirolimus level was 4.7 ng/ml. Although the patient ultimately succumbed to multiorgan failure, red cell exchange may be considered for acute removal of sirolimus in selected patients.