012 Listeners Questions Episode on Blood Administration

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“What are your thoughts about using IVF pumps to administer blood products? The hospital I work at currently will not use fluid pumps, but instead calculates drops/second because they feel the pumps will cause cell lysis.” (Nicky Rivera)

Infusion devices – fluid pumps, syringe drivers – offer certain benefits. They allow fluid or drug therapy to be given reliably in a controlled fashion at a rate of our choosing.
Some inherent inaccuracies with these devices (shhhh!) and differences between devices.

Alternative is gravity flow based on drops per second or seconds per drop but patient movement can have potentially significant consequences on the rate of fluid administration.
May be possible to immobilise limb (typically) to prevent or minimise this – not very patient friendly!

At least one in-line device available in USA which attaches onto the chamber of the fluid administration set and monitors the fluid drops. Alarms if drop rate changes. Does not control fluid rate but aims to improve reliability of gravity flow administration.

Modern volumetric peristaltic infusion pumps typically classified as ‘compatible with’ or ‘suitable for’ blood administration. Most (clearly not all) blood transfusion recipients can move around and transfusions typically given over a period of hours….not using an infusion device could result in a relatively uncontrolled and unpredictable transfusion.

Are there any clinically significant downsides to using an infusion device for blood transfusion? Does what you are thinking about or worrying about actually have any consequences on the patient?

Red cell transfusions (packed red blood cells, sometimes whole blood) typically given to increase recipient oxygen-carrying capacity. Despite what the manufacturers say, could using an infusion device:

  • Reduce the positive benefit the transfusion has on the recipient’s oxygen carrying-capacity?
  • Cause some of the red cells to be broken down during passage through the pump or in some other way cause mechanical damage that affects the ability of the haemoglobin to carry and give up oxygen?
  • Adversely affect the viability of the red cells?
  • In any way increase the likelihood of there being a transfusion reaction?

(I believe that) infusion pumps are approved for clinical use with blood transfusions if manufacturers show that they do not cause in vitro haemolysis.
Infusion device typically not used in human medicine. Can usually ask patient to keep still. Also blood often used as rapid infusion in resuscitation.

In general assumption is that blood administration set with built-in filter used with volumetric infusion pumps; in-line filter added when syringe driver used.

McDevitt RI, Ruaux CG, Baltzer WI. Influence of transfusion technique on survival of autologous red blood cells in the dog. J Vet Emerg Crit Care 2011. 21(3) 2011, pp 209–216.

(Contact me for a copy of the paper)

“A number of studies are available in the human literature that compare peristaltic pumps to centrifugal pumps or other methods of administration…Most of these studies assess damage to red cells in vitro, and rarely examine the effect that transfusion administration has on in vivo red cell survival. Little consensus exists regarding whether or not damage occurs when a particular method is used, and whether or not this is clinically relevant.

Several published studies failed to demonstrate differences in hemoglobin concentration or osmotic fragility when comparing rotary and centrifugal pumps…By contrast, linear peristaltic pumps have been found to increase the free hemoglobin concentration in other studies….[One study] reported an increase in the quantity of RBC fragments when a roller pump is used in comparison with a centrifugal pump. As many of these studies only assessed in vitro parameters, or only involved humans undergoing cardiopulmonary bypass, the clinical significance in dogs is unknown.

The primary objective of the present study was to determine if the method of transfusion has an effect on the lifespan of autologous canine erythrocytes. Additional in vitro studies were also carried out to assess the impact of transfusion technique on canine RBC osmotic fragility, RBC count and hemoglobin concentrations in plasma.”

Study sample size: 9 medium-to-large breed healthy dogs

Collected blood from the dogs, biotinylated* the red cells and then transfused the blood back to the dogs.
(*Labelling red cells by attaching biotin; subsequently allows cells to be monitored.)

“Each dog was autologously transfused in sequence, using 3 different transfusion techniques via a single 20-Ga cephalic catheter:

  • The first preparation of biotinylated RBCs was transfused using a volumetric peristaltic infusion pump and standard transfusion line with built-in 170–260mm filter.
  • The second preparation was transfused using a syringe infusion pump with cells delivered through an 18mm aggregate filter
  • And the final preparation was transfused last via gravity flow using a transfusion line with built-in 170–260mm filter.

Both the infusion pump and syringe pumps were used according to the manufacturer’s specifications.
Transfusion rates for each method were set at 2mL/kg/h, which is the highest transfusion delivery rate used under the standard operating procedure for transfusions used at this institution.
Delivery rate of the control preparation was adjusted by regulating drops/min manually.”

Transfused cells left to equilibrate overnight. Blood samples collected from the dogs morning following transfusion (day 1), and every 7 days until day 49.
These samples were analysed and some other in vitro experimentation also done.

Considerable technical complications during transfusion and sampling.

Authors’ reported results were basically that:

  • There was a significance difference in 24-hour red cell survival between the three transfusion techniques; gravity flow had the highest survival, then volumetric infusion pump, and then syringe pump.
  • After 24 hours, there was no significant difference in the circulating half-life of red cells so regardless of whether gravity flow or a pump was used the red cells that survived the first 24 hours showed no subsequent change in survival time.

“The data presented here suggest that the method of transfusion used to deliver autologous RBCs has a substantial effect on probability of short-term survival of the transfused cells. Particularly remarkable is the apparent [deleterious] effect of delivery via syringe pump and microaggregate filter.
Our initial hypothesis was that the method of transfusion would have an effect on the lifespan of transfused autologous canine erythrocytes; however, we rejected this hypothesis on observation that the transfused cells, having survived the initial equilibration period, showed no significant difference in circulating half-life over the following sampling period.”

Unable to shed light on the mechanisms for what they call “the dramatic losses of autologous RBCs following both pump and syringe administration methods”.

“The present study utilized a comparatively small number of healthy animals, thus the power of this study to detect significant differences in half-life may be reduced. The present study, however, did identify a substantially altered probability of transfusion survival in the immediate post-transfusion period. Of the 3 methods assessed in this study, the greatest effect was noted when red cells were transfused using a syringe pump and microaggregate filter. This method of blood administration is more commonly used in smaller patients (eg, cats, very small dogs), and replication of this finding in cats is warranted.”

Study limitations for clinical application:

  • Small sample size (as mentioned by authors too)
  • Healthy dogs – would findings be replicated in sick dogs being transfused?
  • Autologous* transfusions but typically clinical patients receive heterologous blood – could this difference ne significant? (*Dogs transfused with their own red blood cells)
  • Blood only stored for short period prior to transfusion. Units used clinically often stored for days or weeks with more time for storage lesions to develop – would that compromise red cell viability even more than in this study?

Study was not designed to evaluate clinical significance and patient-centred consequences

In essence what we need to decide is does this study using the methodologies and sample size involved mean that if we use a syringe driver or a volumetric infusion pump in sick dogs there will be a reduction in 24-hour survival and that this reduction will have clinical relevance. And strictly speaking we can’t answer that question.

Heikes BW, Ruaux CG. Effect of syringe and aggregate filter administration on survival of transfused autologous fresh feline red blood cells. J Vet Emerg Crit Care 2014. 24(2):162–167.

Feline red cells meant to be smaller than canine red cells; also some other physical and chemical differences
Transfusion rates typically lower for cats than most clinical canine patients.

“The objective of the study reported here was to carry out transfusion studies of autologous feline RBCs, using essentially the same biotin-labeling and flow cytometry method previously used in the dog, to assess the effect of transfusion technique on short-term survival and circulating half-life of autologous RBCs in the cat. Our hypothesis was that use of a microaggregate filter would be associated with increased risk of early loss and decreased circulating half-life of transfused autologous RBCs in cats.”

6 healthy cats

“The day following blood collection and labeling all cats were transfused with their own, labeled RBCs. Intravenous catheters (22 Ga)j were placed in a cephalic vein, then each cat was transfused in random order using either a syringe pump + microaggregate filter or via a standard blood-giving set (10 drops/mL) using gravity. Blood was transfused at 2 mL/kg/h via syringe pump setting, while administration rates were regulated via drop counting and adjustment for the gravity-administered cells. Gravity administration rates achieved were variable, with most cats receiving the gravity-administered cells over a period of approximately 60 minutes (an overall rate of approximately 4 mL/kg/h for the typical 4.5 kg cat in this study).”

“The data presented here suggest that, in marked contrast to previously reported findings in dogs, the use of a syringe + microaggregate filter system to administer autologous RBC transfusions to cats is not associated with an increased risk of either short-term (<12 h) or long-term (up to 6 wk) accelerated loss of transfused cells. There was no difference in survival attributable to transfusion method in this study….

The study reported here used autologous RBCs with short storage times, a situation that is quite different to one where the patient receives cells from a donor cat that may have been stored prior to administration. The potential impact of mechanical administration systems on survival of stored, allogenic feline RBCs following transfusion is unknown at this time, but is an area of significant interest.

Given the lack of difference in red cell survival and half-life with differing administration techniques in this study, the common practice of using these filters inline does not appear to be contraindicated in feline patients.”

Any evidence from human medicine?

Influence of transfusion technique on transfused cell survival has been investigated in human medicine by various groups using several different methods for transfusion…
BUT typically in vitro studies looking at immediate changes in RBC parameters (e.g. osmotic fragility) rather than in vivo red cell survival.

A reasonable clinical approach to red cell transfusion at this time?

Aim: to give the volume of blood we have calculated over the required period of time.

Too fast may result in unnecessary complications
Too slow may result in delayed clinical improvement, and potentially wastage of product if transfusion time exceeds hospital’s policy necessitating product being discarded.

“I don’t think we have great evidence that the use of infusion devices results in shortened red cell lifespan or reduced viability but there is potentially a signal to be concerned. Given the implications that this might have on the patient’s clinical progression and outcome I guess it makes sense to try not to use an infusion device where possible. In a patient in whom gravity flow alone can be used predictably and reliably, perhaps with the aid of some sort of in-line flow monitoring device, then sure, why not do this.

BUT I would also say that in my personal clinical experience this group would be a minority of the patients I have transfused. Of course that may just reflect my individual case experience but I suspect not. The majority of the patients that I have transfused have had some degree of mobility and activity in their kennel, even if recumbent they can move their limbs or their head. And in these cases I would personally still be using an infusion device based on the evidence that I have found to date

 And I say this partly because one of the things that we do need to factor in is just the plain reality of life in what can often be a busy practice setting. Even if you were using one of those in-line flow monitoring devices, you would still have to have someone available to respond urgently if the alarm sounds. Don’t get me wrong I think if you don’t have any infusion devices and these in-line flow monitoring gadgets work then sure use it but it is still likely to be more labour intensive than when using an infusion device.

If you were using gravity flow of blood to a patient that was able to move around, potentially over a period of 4-6 hours, I would just be worried about being able to monitor that transfusion frequently enough.  Having worked in years gone by in situations where there were either no infusion devices, or not enough infusion devices, I think it can be a real challenge if you are busy and potentially understaffed.

Do you have a different take on the evidence currently available?
Does your practice give all red cell transfusions by gravity flow alone?
If they do, how do you find it? Do you think I am over-egging the practical implications of doing this?

As always, I would love to hear from you!

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