Analysis of Pre- and Post- Donation Calcium Status in Healthy Donors Undergoing Plateletpheresis

Introduction

Over years, an increased demand of platelet concentrates for patients with numerous medical and surgical conditions led to an increased use of technologically advanced “apheresis” for platelet concentrates. This has led to a drift in the accelerated use of single donor platelets obtained by automated blood collections.¹

Plateletpheresis is a process where the whole blood is collected from a donor and the platelets are separated and the rest of the blood components are transfused back to the donor. The modern automated apheresis machine has been used as a principal device to collect platelet concentrates.² In order to obtain platelets by means of apheresis, citrate infusion is needed to prevent the clotting of extra corporeal blood in the cell seperators.³

Citrate is employed as the primary anticoagulant in donor plateletepheresis procedures. The anticoagulant effect of citrate develops from its propensity to chelate calcium ions resulting in the inability of calcium ions to take part in the coagulation cascade. The plasma citrate concentration reaches up to 15 to 24 mmol/L within the apheresis machine, depleting the calcium ion concentration below 0.2 to 0.3 mmol/L, the level required for clotting to happen. This level of anticoagulation requisites the infusion of 500 mL of ACD-A solution and the infusion of this magnitude of solution into a donor results in a calcium ion concentration of 0.2 mmol/L, a level discordant with life. However, this may not happen due to many reasons. First, when blood remits from the apheresis machine to the donor, the citrate in the blood is diluted all over the total extracellular fluid, and the intravascular space. In addition, the muscles, kidney and the liver rapidly imbibes citrate, releasing the bound calcium. Though the compensatory mechanisms switch on, citrate infusion can result in the reduction of ionized calcium levels to a level where symptoms develop in the donor.⁴

The reduced calcium in many of the donors is considered physiologic and of little clinical significance. Due to repeated platelet donations or during prolonged plateletepheresis, citrate accumulation may outpace its metabolism, resulting in hypocalcaemia, which may cause significant adverse donor reactions.³ The objective of this study is to compare pre donation and post donation calcium status in donors and analyse the statistical differences and to study the adverse effects of calcium deficiency among the donors.

Materials and Methods

The study was conducted at Swamy Vivekananda charitable blood bank, Ballari and sixty donors were recruited for the study after obtaining the informed consent. Standard operating procedures derived from Director General of Health Services (DGHS) guidelines for apheresis donor selection was followed.⁵ Donors were subjected to clinical examination. Blood pressure and pulse rate were recorded. Blood grouping and Rh-typing were done.

Donors were selected based on the following criteria:

1. Weight: > 50 Kg

2. Age: 18 to 60 years

3. At least 3 months from last donation

4. Platelet count: > 150 x 103 /cumm

5. Absence of any illness

6. No consumption of non-steroidal anti-inflammatory drugs in last 7 days

7. Negative tests for Human immune virus (HIV), Hepatitis-B (HBsAg), Hepatitis, Syphilis and Malaria.

Each donor was analysed using calibrated automated analyzer for platelet count (Sysmex kx – 21) and chemistry analyzer for calcium (Erba Chem 5x). Blood flow rate for all collections was maintained at 50-60 mL/min with anticoagulant to blood ratio of 1:2. The end point was 300 mL of single donor platelet (SDP) with target yield of 3.5x10¹¹ platelet per unit. In this plateletepheresis, 250 mL of ACD (anticoagulant) was used. Two millilitres of whole blood from the donor was collected into plain vial just before and within 30 min after the procedure. Pre and post plateletepheresis calcium values were analysed.

For easy understanding, calcium levels were categorised as Normal (No signs or symptoms), Modest low (Negligible signs and symptoms) and Low levels (Significant signs and symptoms) based on the donor clinical status.

Results

Pre donation calcium status was analysed based on the categories described in the methodology. Out of 60 blood donors, 27 donors had calcium levels ranging from 8.6- 10.3 mg/dL, 28 donors had calcium levels ranging from 8.8-9.9 mg/dL and 5 donors had calcium levels ranging from 8.4-9.0 mg/dL and none of the donors had any symptoms of hypocalcaemia.

Post donation calcium status was analysed based on the categories as described in the methodology. Out of 60 blood donors, 18 donors had normal levels of serum calcium ranging from 9-10 mg/dL, 25 had modest levels ranging from 8.5-9.8 mg/dL with negligible symptoms like light headedness and nausea and 17 had low levels ranging from 8.0-8.8 mg/dL with symptoms of shivering, twitching and vomiting. None of the cases had any serious complications like seizures, tetany or hypotension.

Discussion

Blood donation is considered to be a safe procedure with very few adverse reactions. However in the recent past, some hazards have developed during donation. Therefore, more stricter precautions are now required to be followed during donation procedure.⁶

A decreasing donor pool in the presence of escalating blood transfusion demands has resulted in the need to maximally employ each blood donor. This has led to a trend in the augmented use of automated cell separators.

While apheresis donation shares in common many unpleasant reactions with whole blood donation, because of the differences, eccentric complications also exist. Overall, evidence suggests that the reiteration of adverse reactions to apheresis donation is less than that seen in whole blood donation. The most common apheresis related reaction is hypocalcaemia caused due to citrate anticoagulation, which is usually mild; however at times can pose a serious threat to the donor. Other reactions to apheresis donation are hypotension and air embolism which are very uncommon.⁴

In our study, we found that 28% of our healthy donors exhibited significant low levels of calcium and had symptoms related to hypocalcaemia. These results correspond well with that of Bolan et al., (2001) who observed decrease in Ca levels by about 33% resulting in an increase in nerve irritability with subsequent paraesthesia, shivering, light-headedness, twitching, and tremors. The various complications that the donors developed were nausea, vomiting and in those whom there was decreased calcium levels, the symptoms progressed to carpopedal spam, seizures and tetany.

The results were analysed with paired t-test to obtain the p value and a statistically significant difference was found in pre donation and post donation calcium status among the donors.

Also, Bolan et al., (2001)⁷ stated that infusion rate of citrate during plateletepheresis is adjusted so that metabolism, redistribution and short period of apheresis procedure prevents accumulation of citrate to toxic levels. In cases of longer duration procedure or increased rate of infusion, citrate accumulation in blood will overwhelm its metabolism resulting in marked decrease in calcium and magnesium levels which may explain development of citrate toxicity in some donors during apheresis.

Joseph et al., (2013)⁸ and Bialkowski et al., (2016)⁹ revealed that during apheresis, citrate is infused at a rate higher than its removal to permit short runs. They also stated that although donors can generally tolerate up to 20% decrease in Ca levels, rapid infusion can be associated with hypocalcaemia in the form of neuromuscular excitability or even seizures. In consistent with this, Humpe et al., (2000)¹⁰ showed that ACD infusion rates of 0.8, 1.0 and 1.2 mL ACD-A/ min/L were accompanied by declines in calcium levels by 10-15%, 15-25% and 20-35% respectively.

Das et al., noticed that mean Ca reduced from 2.62±0.12 – 2.36±0.12 mmol/L. Furthermore, drop in mean Ca from 1.33±0.1 – 0.84±0.1 mmol/L was statistically significant (p< 0.001). Other studies have also reported that although the decrease in Ca was tolerable and not significant, the drop in Ca was statistically significant (p< 0.001). Now that it is evident that acute hypocalcaemia occurs during the plateletepheresis, these ions must be monitored during citrate anticoagulated plateletepheresis.

Based on the results obtained from our study, it can be concluded that plateletepheresis procedures are very safe for donors. In fact severe adverse reactions occur in only a small percentage (0.89%) of donors. Prophylactic oral calcium carbonate supplementation might help reduce the risk of citrate toxicity in this category of the donors with clinical symptoms and help in future retention of these donors.^11-15 It is important to be aware of the risk factors and the etiology of adverse donor reactions in order to protect the donors.³

Conclusion

Overall, plateletepheresis donations performed on apheresis machines are safe, and have very few adverse reactions than those with whole blood donations. Based on the results obtained in our study, we can say that plateletepheresis is a safe procedure for donors. The adverse reactions of donations are well tolerated and can be easily treated. Scrupulous surveillance and overseeing by transfusion medicine specialist with prophylactic oral calcium supplementation will make donors’ experience more pleasant, thereby promoting and increasing voluntary apheresis donor pool in India.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Acknowledgement

Gratefulness and many thanks to the donors and medical staff who provided a great support for this study to be accomplished.