Exertional Collapse Associated with Sickle Cell Trait

During an intense summer high school football conditioning session, an athlete shows signs of muscle weakness, an inability to catch his breath, pain in his legs and back, then he gradually slumps to the ground, indicating he cannot continue with the drill. It is important to recognize what is going on and what the appropriate response should be.

Discussion
Without recent trauma, the differential diagnosis for an athlete showing signs of sudden collapse is more than likely caused by one of four major problems in the following order: sudden cardiac arrest, heat stroke, exertional collapse associated with Sickle Cell Trait (ECAST) or asthma.2 Generally, these conditions differ in their presentation given the circumstances in which they occur.

Sudden cardiac arrest (SCA) associated collapse is usually instantaneous when compared to other forms of collapse. The athlete collapses to the ground and is unresponsive. A severe asthma attack usually occurs in patients with a known history of asthma and inhaler use and is readily recognized with wheezing, cough, chest tightness and breathlessness.

Exertional heat stroke (EHS) can more closely mimic ECAST, yet the conditions surrounding the collapse help differentiate between the two. For example, if at the beginning of football season, an offensive lineman collapses after several hours of activity in the hot summer sun, the diagnosis is most likely EHS. However, if early in the season, during the beginning of practice, an athlete collapses after participating in repetitive and intense running drills lasting only a few minutes, ECAST is a more likely diagnosis. While EHS is associated with a change in mental status, ECAST typically occurs without an alteration in consciousness. In addition, obtaining a core body temperature using a rectal thermometer can help differentiate EHS from ECAST.1

Overview
Sickle cell trait (SCT) is the inheritance of one gene for sickle hemoglobin and one for normal hemoglobin. This condition affects 300 million people worldwide; in the United States, it is present in nine percent of people of African descent, 0.5% of Hispanics and 0.2% of Caucasians. The relative risk of death in athletes with ECAST is approximately 40 times higher in athletes with SCT than those without.3,5 During intense or extensive exertion, in an environment of low oxygen, lactic acid build up, hyperthermia of muscles, and dehydration of red cells coursing through the muscles, the sickle hemoglobin can change the shape of red cells from round to crescent or sickle-shape.1,3 This mutation can make these red blood cells “sticky” and “stiff” and so tend to “logjam” or block small blood vessels that supply muscles and can cause a condition known as fulminant ischemic rhabdomyolysis, a rapid breakdown of muscles starved of blood.1,2 Muscle breakdown contents such as myoglobin can cause, among other things, kidney damage and potentially kidney failure.

Evaluation and Treatment
An exertional sickling collapse is a medical emergency. Coaches and athletic trainers should recognize and quickly respond to any signs or symptoms of ECAST. The collapsed athlete can usually still talk or respond, but in some cases can deteriorate rapidly and become unresponsive within minutes.1 Symptoms include: muscle weakness, where athletes “slump to a stop” as their legs become weak and can no longer hold them; lying fairly still, without yelling in pain; having muscles that feel and look normal (compared to heat cramps, where athletes “hobble to a halt” grabbing a cramping leg muscle, yelling in pain with visibly contracted and hardened muscles); rapid breathing; a core temperature less than 103o F; and a progressive slumping and collapsing to the ground.

Heat, dehydration, altitude, asthma and acute illness can increase the risk for, and worsening of, exertional sickling.2 The Emergency Action Plan in such a situation should include activating Emergency Medical Services (EMS) as needed, assessing vital signs while monitoring for shock and decreased levels of responsiveness, providing supplemental oxygen at 15 L/min by non-rebreather mask and cooling the athlete if necessary. If the athlete fails to improve, attach an AED, with EMS starting an intravenous line with normal saline, and be prepared to start CPR if needed, and get the athlete quickly to the hospital.1

Injury Prevention
While it is important to be prepared to appropriately respond to exertional sickling, it is instructive to keep in mind that “an ounce of prevention is worth a pound of cure” as it pertains to this issue. Prevention of ECAST should be the primary goal for athletes with SCT, as well as their parents, coaches and athletic trainers.3

For those entrusted to safeguard students as they participate in sport, it is important to know, among other things, whether they have asthma, exertional fatigue, heat intolerance and the sickle cell trait. It is recommended to know the status of an athlete with regards to the sickle cell trait 2,4 as it is a part of the preparticipation physical exam (PPE) where students are asked: “Do you or does someone in your family have sickle cell trait or disease?”6

Although all 50 states screen at birth for sickle cell, many students and parents may not know their sickle cell trait status.2 Since 2010, the NCAA has required all student-athletes to have sickle cell status documented, though athletes can opt out of this requirement.5 The NCAA SCT program has significantly decreased the ECAST death rate in Division I football conditioning.3

Proposed primary prevention strategies focus on conditioning activities year-round to maintain fitness and exercise modifications for SCT athletes. These modifications include: athletes setting their own pace with exercise; slow increase in the pace of training, with adequate recovery time between repetitive sprints or drills;5 acclimatization to altitude and temperature, appropriate hydration, avoiding extreme/high-intensity drills, and knowledge of predisposing factors (i.e., heat, altitude, dehydration, asthma and recent illness), as well as early symptoms of ECAST, with modifications or cessation of the training session when these factors are present.3

Summary
Although SCT is generally a benign condition in everyday life, it can pose a significant risk for certain athletes, particularly for athletes who participate in all-out exertion activities for even a few minutes. Screening for SCT and implementing appropriate primary prevention strategies can help prevent ECAST and enable youth with SCT to safely participate in athletic activities.1

Resources

1. Douglas J. Casa, PhD & Rebecca L. Stearns, PhD, editors: Preventing Sudden Death in Sport and Physical Activity, pp 151-162, 2017

2. Scott Anderson, ATC; E. Randy Eichner, MD; et al.; National Athletic Trainers’ Association - Health Care for Life & Sport: Consensus Statement: Sickle Cell Trait and the Athlete, June, 2007

3. Katherine S. Cools, MD, et al.; Sudden death in high school athletes: a case series examining the influence of sickle cell trait, Pediatric Emergency Care, 2022 February 01; 38(2): e497- e500.

4. Douglas J. Casa, PhD, et al., The Inter-Association Task Force for Preventing Sudden Death in Collegiate Conditioning Sessions: Best Practices Recommendations, Journal of Athletic Training, 2012; 47(4):477-480.

5. Chad Asplund, MD, MPH, and Jacob J. Miller, MD, et al., ECAST: Exercise Collapse Associated with Sickle Cell Trait, American Medical Society for Sports Medicine, 2011.

6. David t. Bernhardt, MD, William O. Roberts, MD, MS, editors, PPE: Preparticipation Physical Evaluation, 5th ed., American Academy of Pediatrics, 2019.