Hyponatremia

1. During periods of intense activity, your body releases an antidiuretic hormone called ADH or vasopressin that causes the body to retain water (by decreasing the amount of water that is expelled in urine). Why does this make endurance athletes particularly vulnerable to developing hyponatremia?

The loss of sodium ions can lead to dehydration because sodium makes up 90% of the extracellular fluid and when your sodium levels are low your fluid becomes imbalanced and causes dehydration. (VanMeter, Hubert p 21,23)

The patient in “The Red Hat Hikers” scenario is suffering from hyponatremia. Hyponatremia is defined as a serum sodium level of less than 136mEq/L. Sodium is an electrolyte that is found predominately in the extracellular fluid, and it is the chief regulator of water in the body. Sodium is also important for muscle contraction, nerve impulses, acid-base balance and chemical reactions that occur inside the cell (McCance & Huether, 2014). Normal sodium levels in the body are maintained by the kidneys and the hormone aldosterone. Aldosterone is secreted by the adrenal cortex at the completion of the renin-angiotensin-aldosterone system, and it helps stimulate the proximal tubules of the kidneys to reabsorb sodium and water. The anti-diuretic hormone (ADH) also indirectly affects sodium levels because it regulates water balance in the body (McCance & Huether, 2014).

Effect of Exercise on Arterial Pressure and Vascular Resistance Abbie DeBerg Ms. Brantley May 30, 2012

It is evident that healthy adults running a marathon that replaces with only free water will run into pathophysiology challenges that will affect performance. Adequate fluid intake is crucial for prolonged, strenuous exercises to maintain adequate hydration, thermoregulation, maintain plasma volume and avoid dehydration (Duvillard et al, 2004). Although athletes are prone to hydrate as much as they can during extensive marathons, research shows that fluid replacement with only free water or even hypotonic beverages can be detrimental.

In periods of extreme stress, the sympathetic nervous system will override autoregulation. An increase in sympathetic flow to the kidney will result in what two important effects that will aid maintenance of blood pressure?

Exercise increases heart rate by a process of sympathetic autonomic stimulation. Sympathetic (adrenergic) nerves increase the excitability of the sino-atrial node and reduce the P-R interval .As exercise continues, the physiological changes in the body are continuously monitored by a number of physiological systems and the balance of activity of the sympathetic system (speeding up) and the parasympathetic system (slowing down) is constantly adjusted. When exercise is over, the heart rate does not drop immediately as the body has to undergo a period of re adaption to return to the resting state.

iii. the mechanisms by which a single session of vigorous exercise affects the diuresis produced by the water load (subject C).

Choice “E” is the best answer. The treatment of SIADH and the need for rapid correction of hyponatremia depend on the degree of hyponatremia, whether the patient is symptomatic, and on whether the hyponatremia is acute (< 48 h) or chronic. The patient is experiencing severe symptoms of hyponatremia (unresponsive, Cheyne-Stokes respirations). Usage of any or a combination of the following is indicated: 3% hypertonic saline, loop diuretic with saline, vasopressin-2 receptor antagonists (vaptans), and water restriction. Furosemide and other loop diuretics can be used to increase the excretion of free water. The amount of excess water that must be removed to correct the hyponatremia can be calculated using total body water (TBW). TBW equals body

Figure 1 shows that the systolic and diastolic pressure while the subject was sitting down, 119/64, is lower than that of the other body positions and exercise. Standing showed the second lowest systolic and diastolic pressure, 121/83. Lying down showed a slightly higher blood pressure of 123/84. The highest blood pressure, 133/94, was measured when the subject had just completed some physical activity. Figure 2 and 3 display, respectively, the difference between heart contractions at rest and after exercise, as illustrated by the greater number of contractions following exercise in the same amount of time compared to resting conditions. In addition to displaying the interval lengths for three sequential beats from Figures 2 and 3, Table 1 also includes the heart rate for before and post exercise, 102 bpm and 132 bpm, respectively. Figure 4 shows similar

Hypovolemia can be due to many predisposing factors such as fracture and surgery. The patient experienced a type of open fracture which is categorize by a wound in combination with the fracture (Whiteing, N., 2008, p. 50). Open Reduction Internal Fixation (ORIF) is the most common surgical technique for patients with open fracture which also includes tibia and fibula (William, L & Hopper, P., 2011, p. 1071). Since it was a major surgery massive blood loss or hypovolemia can be experience by a patient who will undergo this procedure. Craft, J., Gordon C., & Tiziani, A. (2011, p. 895) states that hypovolemia is a decrease in extracellular fluid volume and decrease in blood volume. In addition, Buttaro, T., (2013, p. 982) implies that there is approximately two (2)

The sympathetic and parasympathetic systems are affected due to overtraining. An individual can experience the signs and symptoms of the sympathetic nervous system, such as an increase in heart rate and blood pressure, loss of appetite, decrease body mass, sleep disturbances, emotional instability, and high basal metabolic rate. Similarly, the signs and symptoms of the parasympathetic overtraining include early onset of fatigue, decreased resting heart rate, and rapid heart rate recovery after exercise, and a decreased in resting blood pressure. (Kenney et al., 2015, p.355). The parasympathetic signs are seen more often in individuals who perform a high training volume. The physiological

Current guidelines dictate a slow correction of sodium, not exceeding 10 mmol/24 hrs to prevent central pontine myelinolysis (CPM) (Greenberg et al, 2015, Spasovski et al, 2014, Verbalis et al, 2007, Verbalis et al, 2013). CPM is a non-inflammatory demyelinating disease characterized by the loss of myelin in the base of the pons and carries a poor prognosis, often times resulting in death. It was first described by Adams et al in 1958, in patients with hyponatremia in the setting of alcoholism and malnutrition (Adams, et al, 1958, Martin, 2004, Staikov, et al, 2015). The exact mechanism of demyelination remains unknown, however one proposed theory is that when osmotically active substances such as sodium are very low in the serum in the setting of hyponatremia, free water shifts into the brain and the brain adapts by allocating water into the cerebrospinal fluid and redirecting intracellular solutes out of the cells. If serum osmolarity rises back to normal too quickly, an osmotic gradient develops and causes destruction of myelin. The pons is vulnerable as it is less capable of transporting solutes across membranes than other areas of the brain leading to localized pontine demyelination. Catastrophic outcomes such as pseudobulbar palsy, spastic tetraparesis, locked-in syndrome and death can occur (Martin, 2004). In the patient described above, he developed

It’s common among young people who challenge themselves to “water drinking contests,” or athletes who mistakenly over-hydrate while training, Scientific American reported.

In schools around the country there are kids who are involved in sports, but lack the amount of fluids your body needs to function properly. The reason why this happens is due to dehydration. People in sports get pushed so hard and hardly ever get the chance to run to the water fountain to get a drink of water. Dehydration causes people to faint, vomit, and produces a fever because of the lack of fluids in their body.