Year: 2002
Type: editorial
Abstract: Reactions to blood donation have been with us since the early years of organized blood collection. Several investigators found that 2 to 5 percent of whole blood donations (WBD) during the World War II collection effort resulted in a vasovagal reaction (VVR).1,2 The symptoms are well known: weakness, dizziness, and pallor. Syncope characterized by loss of consciousness, bradycardia, and hypotension occurs less frequently, in 0.08 to 0.34 percent of donations.3 While the vast majority of VVRs are benign, syncopal episodes can progress to vomiting, tetany, or seizures. For the unfortunate donors who experience such a severe reaction, a hospital stay may be the "reward" for their altruism. Popovsky et al.4 found that complications of allogeneic blood donation result in a hospitalization rate of 1 per 198,000 donations, and 67 percent of reaction events are associated with VVR. Hospitalizations are due to fall-related injuries during a VVR, or prolonged recovery with slow return of predonation vital signs. Although hospitalization represents the extreme of the spectrum of blood donation reaction events, the typical manifestations may too have a significant impact on blood donor operations. When a donor reacts, a predictable sequence of events unfolds, at both the fixed or the mobile site. Donor staff are redeployed to attend the affected donor, tying up the "beltline" of waiting donors. Presenting donors awaiting their turn to be screened for the medical history or the phlebotomy frequently lose patience and leave before donating. A donor reaction may precipitate a chain reaction of VVRs by other donors. Much anecdotal evidence suggests that this scenario occurs more frequently at high school or college blood drives than in other settings. In most blood collection programs, a donor with a severe VVR is permanently deferred or, if not, typically self-defers for fear of becoming a repeat "casualty." The result is donor pool attrition. With growing awareness and concern regarding the contraction of the blood donor pool both in the United States and abroad, any aspect of blood donation that could impact the availability of blood should be examined. VVR should not be viewed as unavoidable. What is known about VVR? What is the profile of donors who suffer reactions and are there interventions that could prevent reactions, thus conserving precious resources? What role does blood collection technology play? Both the pathophysiology and the mechanism of VVR are incompletely understood. It is believed that central autonomic pathways, precipitated by emotions and hyperventilation, play a critical role. Hypoperfusion of the reticular activating system and cerebral cortex is the final common pathway for the majority of episodes.5 Interruption of blood flow for 8 to 10 seconds is sufficient to produce loss of consciousness.6 Who is at risk for VVR? The older donor, the younger donor, or the first-time donor? In the 1980s, it was common for blood collectors to discourage or actively retire donors who were 65 to 70 years of age or older. Such policies implied that it was the older donor who was at increased risk for VVR. However, the data do not support such policies. Two studies found that elderly blood donors were not at increased risk for reactions, with 0.03 percent and 0 percent of donors, respectively, having severe reactions.7,8 However, another investigator9 found that male donors over 45 years of age had a significantly longer recovery time (54 vs. 43 min) than donors younger than 30. For women in the same age brackets, the difference was similar to that found for men. Other investigators have attempted to identify the risk factors for VVR. Most frequently identified are first-time donor status, low weight, and youth. Unfortunately, most of the reports are based on anecdotal evidence, and not on controlled studies. An exception to this was a case-controlled study at three blood centers by Trouern-Trend et al.5 involving 1890 donors with syncope. Using regression analysis, they found that young age, weight and donation status were significant predictors of VVR. First-time donors, age under 20 years, and weight less than 120 pounds were independent factors for higher reaction rates. Gender, predonation blood pressure, and predonation pulse were not predictive. In this issue of TRANSFUSION, two papers provide additional insight on VVR, based on WBD and apheresis donation events. Newman10 investigated the incidence of VVR in 1302 high school students participating in on-site blood drives in Detroit. The maximum volume collected was 535 mL. Newman looked for evidence of synergy among the various risk factors. Included in the analysis were 157 nonstudent participants. The study found that African-American blood donors are significantly less likely to develop VVR (1.3% vs. 8.2%). Overall, the risk factors for VVR were first-time donor status, low weight (<130 pounds), and female gender. When first-time donor status was coupled with students weighing less than 130 pounds, the rate for a reaction jumped to 16.2 percent. Thus, risk factors can act synergistically. However, the data showed that when donors under 150 pounds were excluded, there was no difference between males and females. How should these data be interpreted? Current theory holds that peripheral baroreceptor reactivity in the donor is the key to VVR. These receptors are presumably triggered by factors including age, emotional state, and blood pressure. The degree of a donor's baroreceptive response is related to the percentage of blood volume that is removed.5 First-time donors can be expected to have more anxiety about the donation process than more experienced donors. Smaller donors lose a larger proportion of blood volume; up to 14 percent in WBD. Gribbin et al.11 have shown that ventricular baroreceptor sensitivity decreases with age, which may explain why younger donors have the predilection for reactions. Are the VVR data for whole blood and apheresis donations similar? In WBD, blood is collected rather rapidly, over 7 to 12 minutes, with only modest fluid replacement administered after the procedure. With apheresis, longer collection times allow for enhanced fluid balance. Moreover, the smaller extracorporeal volume of current generation apheresis systems minimizes the risk of hypovolemic effects. As such, VVRs are rare, with fewer than a 0.5 percent incidence in plateletpheresis, plasmapheresis, and RBC apheresis.12 Most adverse events are related to the effects of citrate anticoagulation. With the introduction of RBC apheresis, another variable, saline compensation, may influence donor reactions. In a study involving more than 59,000 donors undergoing either double RBC or automated RBC-plasma collection, Wiltbank13 found that the incidence of moderate (syncopal) and severe (prolonged recovery, tetany) reactions was significantly less than that seen in whole blood collections. For WBD, the rate of moderate reactions was 14.5 in 10,000 vs. 6.2 in 10,000 for automated collection. The incidence of severe reactions was even less, 1.2 in 10,000 procedures. The reaction rates in automated RBC collection and plateletpheresis were not significantly different. It remains unclear whether these findings are due to the saline compensation used in RBC apheresis, or to fluid equilibrium because of the longer collection times required for apheresis procedures. With this as backdrop, the findings of Tomita et al.14 are surprising. They found that the incidence of VVR was approximately three fold higher in female Japanese platelet apheresis donors than in female WBD. While the authors do not provide a definition of VVR, the blood pressure and pulse monitoring during the procedures would suggest that these reactions were of the vasovagal type. Unfortunately, there was no differentiation between mild and more severe symptoms. The authors indicate that most of the reactions were "minor." Unlike in WBD, the incidence of VVR did not correlate with age. The relatively high rate of adverse events in females may be related to circulating blood volume; donors suffering reactions had a significantly smaller blood volumes than controls. The relatively small weight of this donor population may explain the high background rate, as indicated by a 0.99 percent incidence of VVR in males. With a more refined understanding of the risk factors for VVR, blood collectors need to decide which methods of collection are best suited for specific donor groups. More studies are needed to determine whether there are interventions that can prevent or mitigate VVR. Finally, blood collectors should reevaluate policies or practices that discourage or restrict older individuals from giving the gift of life.
Source: Transfusion
Author: Mark A. Popovsky
Institutions: Harvard University, Haemonetics (United States)
Language: English
Subfield: Management of Technology and Innovation
Domain: Social Sciences
Open Access status: bronze
OpenAlex ID: W2085544446