Absa Cape Epic – Multi-stage events and kidney damage
Posted on 14 March 2019
In 2018, eight riders were withdrawn from the Absa Cape Epic and referred to Dr Geoff Bihl, a nephrologist at Mediclinic Vergelegen, for additional care. Most of these patients received treatment for a combination of severe dehydration (>7% body weight), rhabdomyolysis (the breakdown of muscle), where this can lead to life-threatening blood electrolyte abnormalities i.e. potassium, acute kidney injury or heat stroke. The decision to withdraw a rider is not taken lightly, or without due consideration to all factors affecting the rider.
According to Dr Geoff Bihl, “The Epic is a unique event for all competitors as a whole and for each competitor specifically. It is a multi-stage event where the world’s top mountain bike athletes compete on the same route as the weekend warrior.” Dr Bihl is often called upon to receive and treat riders from the Absa Cape Epic who have been withdrawn from the race as a result of potentially serious harm to the riders’ kidneys.
“Elite athletes are well trained in endurance, hydration techniques, and in understanding their own physiology. This isn’t always true with the more social rider, where fitness is usually not a problem and most are well- if not over-trained, but the prolonged exposure to strenuous exercise often at a higher rate than a training ride together with incessant heat places an increased strain on their physical being,” says Dr Bihl.
Repetitive strenuous exercise with little recovery requires fitness, excellent hydration, and of course nutrition. In multi-stage events, riders typically push themselves harder, the routes are designed to be tough and challenging, the pressure, stigma and cost in time and money of the race all affect performance expectation.
“To prevent any serious damage, we encourage riders to learn how to monitor themselves adequately rather than waiting until fatigue, thirst and muscle cramps develop as those are late symptoms,” explains Dr Bihl. A rough guide is a fluid intake of 400-500 ml per hour increasing to a max of 750 per hour when the temperatures exceed 30c.
Ensuring adequate hydration before the ride/stage is also critical and this includes a good urine voiding before the race, clear urine colour (SG <1) and stable pre-race weight (should be worked out a good period before the stage event).
Dehydration (defined as greater than 2% loss of body weight) may negatively affect performance but in highly trained endurance athletes, plasma volume and sodium serum concentration can be well preserved up to 5% body weight loss. According to Dr Bihl, one study of Ironman triathletes indicated that dehydration up to 5% body weight loss did not correlate with the occurrence of medical complications.
For doctors managing the riders as part of Mediclinic’s role at the Absa Cape Epic, there is an urgent need to understand the riders’ hydration status in order to manage treatment in severe cases. Straightforward signs such as dry mucous membranes, decreased skin turgor and sunburn are not accurate, while a urine specific gravity may help as will any evidence of haematuria on the dipstick (may suggest rhabdomyolysis).
To better understand the hydration levels of athletes, Mediclinic doctors first question riders and then, where necessary, make use of the on-site pathology services of Pathcare for blood tests for a more accurate reading. For the vast majority of patients, time allowing, euhydration can be achieved by drinking and eating normal beverages and meals.
Dr Darren Green, Race Doctor to the Absa Cape Epic emphasises the value of such tests, “Pathcare services afford us the opportunity for early and accurate diagnosis of renal impairment and allows us to plan appropriate expert management to prevent permanent loss of function.”
“Traditionally, the use of intravenous administration of fluids has been reserved for the treatment of clinical severe dehydration (hypotension, positive raised leg test) and in the setting of presumed heat illness in the collapsed athlete,” explains Dr Bihl. At-risk riders would be highlighted through the information gained by Pathcare readings.
Dr Bihl goes on to explain, “Treatment of exercise-associated hyponatremia with IV infusion to correct plasma sodium levels is also a standard and accepted use of IV fluid infusions although not always recommended in the field where monitoring can be difficult.”
The importance of well-motivated and fully informed decision making is highlighted in professional sport. “IV fluids and plasma binders are not allowed in World Anti-Doping Agency–governed competitions,” cautions Dr Bihl. He also strongly emphasises that routine IV therapy cannot be recommended as best practice for the majority of athletes. Repetitive insults to renal function may have an effect on long-term renal function although again there are few studies to allow for specific recommendations.
To manage riders’ health and for riders to prepare for conditions, Dr Bihl recommends that in multi-stage events the ambient temperature and humidity levels for the next stage should be announced at race briefings and a warning issued of an increased sweat rate and therefore the risk of dehydration. Increased fluid intake thus becomes critical for the riders.