Hiponatremia

Hiponatremia

Pendahuluan:

Ion Natrium (Na⁺) merupakan kation utama di cairan ekstraseluler (plasma dan interstisial). Kadar normal dalam serum adalah 135 -145 mmol/L. Na⁺ berperan penting dalam pengaturan osmolaritas plasma. Kadar yang terlalu rendah atau terlalu tinggi bisa mempengaruhi fungsi otak. Sebagai contoh, hiponatremia berat (< 115 mmol/L) berpotensi menimbulkan gangguan neurologis, seperti penurunan kesadaran sampai coma dan kejang. Seringkali klinisi terjebak untuk menangani hiponatremia dengan cara terlalu agresif, sehingga justru menyebabkan penyulit dan kematian.

Beberapa poin penting yang perlu diketahui sebelum melakukan terapi cairan koreksi untuk hiponatremia:

• Tidak ada konsensus tentang tatalaksana hiponatremia.
• Gejala ringan bisanya bisa ditanggulangi dengan restriksi air.
• Gejala berat (misal, kejang atau coma) -----NaCl hipertonik (NaCl 3% yang mengandung 513 mmol Na⁺ per L)
• Kebanyakan pasien hiponatremia yang disertai hipovolemia atau gangguan hemodinamik bisa diatasi dg Normal Saline (mengandung 154 mmol Na⁺/L)
• Kejang bisa dihentikan cepat dengan menaikkan Na+ serum hanya 3 sampai 7 mmol/L.
• Kebanyakan komplikasi demielinisasi terjadi bila laju koreksi melebihi 12 mmol/L/24 jam.
• Pernah juga dilaporkan mielinolisis serebropontin pada laju peningkatan kadar Na⁺ serum 9 sampai 10 mmol/L dalam 24 jam atau 19 mmol dalam 48 jam.
• Rekomendasi : laju koreksi < 8 mmol/L/24 jam.
• Namun koreksi awal 1 -2 mmol/L/jam untuk beberapa jam pertama pada kasus berat.
• Indikasi menghentikan koreksi akut dari gejala adalah berhentinya manifestasi yang mengancam jiwa atau kadar serum sudah mencapai 125 atau 130 mmol/L, bahkan sebelum mencapai kadar tersebut jika kadar semua (baseline) di bawah 100 mmol/L

CARA KOREKSI:

• Tanpa memandang etiologi, hiponatremia berat hatrus dikoreksi dengan NaCl hipertonik (NaCl 3%) jika ada gejala neurologis, seperti penurunan kesadaran dan kejang. Tidak ada alasan kuat untuk memberikan NaCl 3% pad apasien hiponatremia simatomatik (kadar di atas 125 mEq). Pada prinsipnya, 1 liter larutan yang mengandung natrium bisa meningkatkan atau nmenurunkan kadar natrium plasma

• Besarnya perubahan kadar Na+ plasma bisa dihitung dengan rumus:

Na⁺ infus  –  Na⁺ serum

   Air tubuh total  +  1

 

• Air tubuh total pada dewasa = 60% berat badan, sedangkan pada anak 70% berat badan

ILUSTRASI KASUS:

Wanita usia 30 tahun mengalami kejang grandmal 3 kali, dua hari setelah apendektomi.
Paisen diberikan 20 mg diazepam dan 250 mg fenitoin iV dan dipasang intubasi laring dengan ventilasi mekanik. Allo-anamnesis ke perawat mengungkap pasien diberi 2 liter D5 dan 1 liter RL dalam 24 jam pertama setelah operasi, dan setelah itu dibolehkan minum
Klinik: pasien tidak dehidrasi dan BB 46 kg. stupor dan hanya respon ke nyeri tetapi tidak terhadap perintah. Lab: Na⁺ serum 112 mmol/L, osmolalitas serum 228 mOsm/kg, osmolalitas urin 510 mOsm/kg WD/ hiponatremia hipotonik karena retensi air.

Direncanakan koreksi Na⁺ dalam 5 jam pertama menjadi 117 mmol/L dengan harapan kejang menghilang, dan sesudah itu rencana dilanjutkan dengan menaikan 5 mmol/L untuk 19-20 jam kemudian. Berapa jumlah dan kecepatan infus NaCl 3% yang dianjurkan?

Na⁺ infus  –  Na⁺ serum                       =          513   –  112  

  Air tubuh total  +  1                           60%BB + 1

         401                                            =          401                              =          14.02

(60% x 46) + 1                                               28.6

Artinya 1 L NaCl 0.3% akan meningkatkan kadar Na+ plasma ~ 14 mmol/L

Dalam 5 jam pertama diperlukan hanya menaikkan kadar Na⁺ sebesar 5 mmol/L, berarti hanya dibutuhkan: 5 : 14 = + 0.357 L NaCl 3% atau 357 ml. Jadi laju pemberian adalah 357: 5 = + 72 ml per jam atau 18 tetes per menit (jika menggunakan set infus Otsuka ). Setelah 5 jam, kadar Na⁺ naik menjadi 117 mmol/L. kejang hilang pasien masih somnolen, berikutnya direncanakan menaikkan 5 mmol dalam waktu 19-20 jam. Laju pemberian adalah 357 : 19 = ~ 18 ml/jam. Biasanya pemberian infus demikian lambat memerlukan infusion pump. Dan kebutuhan maintenance 20 jam bisa diberikan Normal saline. NaCl 3% tidak diteruskan setelah Na⁺ plasma mencapai 125 atau 130 mmol/L. Klinisi bisa menentukan sendiri berapa kadar Na⁺ yang dikehendaki setelah waktu tertentu (tidak ada konsensus) dan bisa saja memodifikasi sesuai respons. Yang terpenting adalah koreksi dilakukan tidak terlalu cepat.

Referensi :

Adrogue, HJ; and Madias, NE. Primary Care: Hyponatremia. New England Journal of Medicine 2000; 342(21):1581-1589..

Symptoms of Low Sodium & Too Much Water

 

Overview

Sodium is the major electrolyte in the blood. It is used for blood volume control and to transmit impulses for nerve and muscle stimulation. The body tightly regulates the balance of sodium, as too much or little can be deadly. Too little sodium or excess water outside the cells is called hyponatremia. Conditions where this can happen include serious burns, cancer, congestive heart failure, excessive water intake during exercise, kidney disease and liver cirrhosis.

 

Brain Function

The brain is sensitive to changes in sodium levels. The elderly population can be susceptible to hyponatremia. General confusion can be a symptom of low sodium, and brain function can deteriorate to include hallucinations, decreased consciousness or even a coma in extreme instances.

 

Nausea

Nausea or loss of appetite is a symptom of hyponatremia. Vomiting may also occur. Severe vomiting and diarrhea cause loss of water and electrolytes like sodium, and may trigger hyponatremia or make it worse.

Muscle Problems

Feelings of weakness or lethargy may be present as a symptom of hyponatremia. Muscle spasms, cramps or possibly seizures may occur because of low sodium. Sodium helps regulate muscle contractions, so that is why hyponatremia may result in muscle weakness or spasms when there is not enough sodium in the body fluid to stimulate proper muscle contraction.

 

Treatment

Call a health care professional if symptoms of hyponatremia are present, as treatment includes diagnosis of hyponatremia from a health care professional. Treatments may include intravenous fluids, medications or water restriction. Recovery time depends on the severity and how quickly the hyponatremia came on. Hyponatremia that has occurred in a few days or less is typically more severe than chronic hyponatremia because the brain has time to adjust to the sodium level changes.

Read more: http://www.livestrong.com/article/436677-symptoms-of-low-sodium-too-much-water

 Hyponatremia 

 

Definition

The normal concentration of sodium in the blood plasma is 136-145 mM. Hyponatremia occurs when sodium falls below 130 mM. Plasma sodium levels of 125 mM or less are dangerous and can result in seizures and coma.

 

Description

Sodium is an atom, or ion, that carries a single positive charge. The sodium ion may be abbreviated as Na⁺ or as simply Na. Sodium can occur as a salt in a crystalline solid. Sodium chloride (NaCl), sodium phosphate (Na₂HPO₄) and sodium bicarbonate (NaHCO₃) are commonly occurring salts. These salts can be dissolved in water or in juices of various foods. Dissolving involves the complete separation of ions, such as sodium and chloride in common table salt (NaCl).

About 40% of the body's sodium is contained in bone. Approximately 2-5% occurs within organs and cells and the remaining 55% is in blood plasma and other extracellular fluids. The amount of sodium in blood plasma is typically 140 mM, a much higher amount than is found in intracellular sodium (about 5 mM). This asymmetric distribution of sodium ions is essential for human life. It makes possible proper nerve conduction, the passage of various nutrients into cells, and the maintenance of blood pressure.

The body continually regulates its handling of sodium. When dietary sodium is too high or low, the intestines and kidneys respond to adjust concentrations to normal. During the course of a day, the intestines absorb dietary sodium while the kidneys excrete a nearly equal amount of sodium into the urine. If a low sodium diet is consumed, the intestines increase their efficiency of sodium absorption, and the kidneys reduce its release into urine.

The concentration of sodium in the blood plasma depends on two things: the total amount of sodium and water in arteries, veins, and capillaries (the circulatory system). The body uses separate mechanisms to regulate sodium and water, but they work together to correct blood pressure when it is too high or too low. Too low a concentration of sodium, or hyponatremia, can be corrected either by increasing sodium or by decreasing body water. The existence of separate mechanisms that regulate sodium concentration account for the fact that there are numerous diseases that can cause hyponatremia, including diseases of the kidney, pituitary gland, and hypothalamus.

 

Causes and symptoms

Hyponatremia can be caused by abnormal consumption or excretion of dietary sodium or water and by diseases that impair the body's ability to regulate them. Maintenance of a low salt diet for many months or excessive sweat loss during a race on a hot day can present a challenge to the body to conserve adequate sodium levels. While these conditions alone are not likely to cause hyponatremia, it can occur under special circumstances. For example, hyponatremia often occurs in patients taking diuretic drugs who maintain a low sodium diet. This is especially of concern in elderly patients, who have a reduced ability to regulate the concentrations of various nutrients in the bloodstream. Diuretic drugs that frequently cause hyponatremia include furosemide (Lasix), bumetanide (Bumex), and most commonly, the thiazides. Diuretics enhance the excretion of sodium into the urine, with the goal of correcting high blood pressure. However, too much sodium excretion can result in hyponatremia. Usually only mild hyponatremia occurs in patients taking diuretics, but when combined with a low sodium diet or with the excessive drinking of water, severe hyponatremia can develop.

Severe and prolonged diarrhea can also cause hyponatremia. Severe diarrhea, causing the daily output of 8-10 liters of fluid from the large intestines, results in the loss of large amounts of water, sodium, and various nutrients. Some diarrheal diseases release particularly large quantities of sodium and are therefore most likely to cause hyponatremia.

Drinking excess water sometimes causes hyponatremia, because the absorption of water into the bloodstream can dilute the sodium in the blood. This cause of hyponatremia is rare, but has been found in psychotic patients who compulsively drink more than 20 liters of water per day. Excessive drinking of beer, which is mainly water and low in sodium, can also produce hyponatremia when combined with a poor diet.

Marathon running, under certain conditions, leads to hyponatremia. Races of 25-50 miles can result in the loss of great quantities (8 to 10 liters) of sweat, which contains both sodium and water. Studies show that about 30% of marathon runners experience mild hyponatremia during a race. But runners who consume only pure water during a race can develop severe hyponatremia because the drinking water dilutes the sodium in the bloodstream. Such runners may experience neurological disorders as a result of the severe hyponatremia and require emergency treatment.

Hyponatremia also develops from disorders in organs that control the body's regulation of sodium or water. The adrenal gland secretes a hormone called aldosterone that travels to the kidney, where it causes the kidney to retain sodium by not excreting it into the urine. Addison's disease causes hyponatremia as a result of low levels of aldosterone due to damage to the adrenal gland. The hypothalamus and pituitary gland are also involved in sodium regulation by making and releasing vasopressin, known as anti-diuretic hormone, into the bloodstream. Like aldosterone, vasopressin acts in the kidney, but it causes it to reduce the amount of water released into urine. With more vasopressin production, the body conserves water, resulting in a lower concentration of plasma sodium. Certain types of cancer cells produce vasopressin, leading to hyponatremia.

Symptoms of moderate hyponatremia include tiredness, disorientation, headache, muscle cramps, and nausea. Severe hyponatremia can lead to seizures and coma. These neurological symptoms are thought to result from the movement of water into brain cells, causing them to swell and disrupt their functioning.

In most cases of hyponatremia, doctors are primarily concerned with discovering the underlying disease causing the decline in plasma sodium levels. Death that occurs during hyponatremia is usually due to other features of the disease rather than to the hyponatremia itself.

 

Diagnosis

Hyponatremia is diagnosed by acquiring a blood sample, preparing plasma, and using a sodium-sensitive electrode for measuring the concentration of sodium ions. Unless the cause is obvious, a variety of tests are subsequently run to determine if sodium was lost from the urine, diarrhea, or from vomiting. Tests are also used to determine abnormalities in aldosterone or vasopressin levels. The patient's diet and use of diuretics must also be considered.