Metabolic acidosis is a pathological condition that arises when the blood pH fal
ID: 53352 • Letter: M
Question
Metabolic acidosis is a pathological condition that arises when the blood pH falls due to excessive acid production. The excess protons in the blood decrease the amount of HCO3- and thus reduce the buffering capacity of blood. A rapid drop in pH can lead to death. The normal blood pH = 7.4 and the bicarbonate and carbon dioxide concentrations are 24 mM, and 1.2 mM respectively.
a.) If after a few hours of intense exercise, a marathon runner’s blood pH was found to be 7.1 and the bicarbonate concentration was 8 mM. What is the concentration of CO2 in the athlete’s blood? (Bicarbonate pKa = 6.1).
b.) A second athlete had had a blood pH = 7.03 and [CO2] = 1.2 mM, what is the blood [HCO3-]? What can you say about the health of this individual? Suggest a treatment for this condition.
c.) How might your suggestion in (b) be of benefit to middle distance runners (involving endurance running as well as sprinting)?
Explanation / Answer
In the body, most of the CO2 is in the form of a substance called bicarbonate (HCO3-). Therefore, the CO2 blood test is really a measure of your blood bicarbonate level.An arterial blood gas (ABG) test measures the acidity (pH) and levels of oxygen and carbon dioxide in the blood.
Sodium bicarbonate (NaHCO3) is the agent most commonly used to correct metabolic acidosis. The HCO3- deficit can be calculated by using the following equation:
HCO3- deficit = deficit/L (desired serum HCO3- - measured HCO3-) × 0.5 × body weight (volume of distribution for HCO3-)
This provides a crude estimate of the amount of HCO3- that must be administered to correct the metabolic acidosis; the serum HCO3- level or pH should be reassessed frequently.
HCO3- can be administered intravenously to raise the serum HCO3- level adequately to increase the pH to greater than 7.20. Further correction depends on the individual situation and may not be indicated if the underlying process is treatable or the patient is asymptomatic
a)concentration of CO2 in the athlete’s blood 35-45 mm Hg (4.6-5.9 kPa)
b) blood [HCO3-] is 22-26 mEq/L (22-26 mmol/L)
c) sprinting as well as runing causes the strong accumulation of lactate and hydrogen ions, which are waste products of anaerobic energy production. If they are not removed quickly enough from the muscle, they inhibit further muscle contraction. results in become too acidic and fatigue
Middle distances are also covered at a moderately high speed, which leads to respiratory distress relatively soon during the middle distance. If an athlete begins to gasp for breath, his body must rely on anaerobic energy supply, i.e. he reaches the anaerobic threshold. However as the body can’t be trained for long above this threshold, medium-haul aerobic and anaerobic energy supply stay relatively in balance. This means that lactate and hydrogen ions are removed in time, but the pressure on muscles and the heart are nevertheless continuously very high. For this reason, running over middle-distance is perceived as particularly unpleasant. But these distances are incredibly effective to train both the anaerobic and aerobic energy provision, as well as the considered threshold and speed endurance. The main reason for this is the psychological effect: You know that it will be over soon and bring more out of yourself than you would expect over longer distances.
Since even well-trained athletes can run just a few seconds at maximum speed, you must be economical with your power to prevent a sudden drop in performance during the run. These routes should always start with an average intensity. Even well-trained people are limited to a period of 40 to 60 seconds when running at their maximum speed because the muscles become too acidic.
The advantage is that middle distance runs near to the anaerobic threshold are best suited to burn a lot of energy in a relative short time and achieve good results.