Last late autumn, my mother was admitted to the emergency department due to severe dehydration caused by acute gastroenteritis. I stood at the entrance of the emergency room, watching as the nurse pushed the treatment cart in. The bottle of liquid labeled "Compound Sodium Lactate Ringer Injection" in the metal tray swayed slightly under the light. What exactly does this medicine do? "I grabbed the nurse and asked, but the nurse only said," Supplement body fluids and electrolytes. But in the later treatment, this bottle of liquid not only helped the mother correct dehydration, but also stabilized her electrolyte imbalance caused by vomiting. At that moment, I suddenly realized that this seemingly ordinary injection may contain the key code to maintaining life balance. Today, I will use my personal experience as a guide to break down the function of "Compound Sodium Lactate Ringer Injection" with everyone.
---1. The basis of action of compound sodium lactate Ringer injection: ingredients and pharmacological mechanisms. To understand its action, one must first understand "what it is". Compound Sodium Lactate Ringer Injection is not a single drug, but a compound solution composed of multiple electrolytes and buffering agents. Its composition strictly simulates the electrolyte concentration of human extracellular fluid - containing 3.10g of sodium lactate, 6.00g of sodium chloride, 0.30g of potassium chloride, and 0.20g of calcium chloride (anhydrous) per 1000ml. This ratio is not arbitrarily set, but a "golden combination" validated by extensive physiological research.
（1） Composition analysis: A "replica" of extracellular fluid. The main electrolytes in human extracellular fluid (including plasma and interstitial fluid) are sodium ions (Na ⁺) and chloride ions (Cl ⁻), followed by potassium ions (K ⁺) and calcium ions (Ca ² ⁺), which together maintain cell osmotic pressure, charge balance, and physiological functions.

In the composition of compound sodium lactate Ringer injection, sodium chloride provides Na ⁺ and Cl ⁻ (Na ⁺ is about 130mmol/L, Cl ⁻ is about 109mmol/L), which are close to the normal range of Na ⁺ (135-145mmol/L) and Cl ⁻ (96-106mmol/L) in plasma; Potassium chloride supplementation of K ⁺ (about 4mmol/L) is consistent with plasma K ⁺ (3.5-5.5mmol/L); Calcium chloride provides Ca ² ⁺ (approximately 1.5 mmol/L), which is close to plasma free calcium levels (1.1-1.3 mmol/L). As for sodium lactate (about 28mmol/L), it is a key regulator of acid-base balance.
You may ask: Why choose sodium lactate instead of sodium bicarbonate for direct alkaline supplementation? This is precisely the ingenuity of its design - after entering the human body, sodium lactate needs to be converted into pyruvate through the action of liver lactate dehydrogenase under aerobic conditions, and then enters the tricarboxylic acid cycle for metabolism into CO ₂ and water, ultimately generating bicarbonate (HCO ∝⁻). This "slow release" method avoids the short-term alkaline overdose that may occur due to direct input of sodium bicarbonate, and is more in line with the body's own metabolic rhythm.
（2） Pharmacological mechanism of action: multidimensional "balance maintainer" Based on the above components, its mechanism of action can be summarized as "three-dimensional balance": 1. Osmotic balance: Na ⁺ is the main determinant of extracellular fluid osmotic pressure (accounting for more than 90%). The concentration of Na ⁺ in the injection solution is similar to that in plasma, and it does not cause drastic changes in intracellular and extracellular osmotic pressure after input, avoiding cell edema caused by hypotonic solution (such as brain edema) or cell dehydration caused by hypertonic solution.
2. Electrolyte balance: K ⁺ participates in nerve impulse conduction and myocardial function, while Ca ² ⁺ affects coagulation, muscle contraction, and nerve excitability. When patients lose these ions due to vomiting, diarrhea, and excessive sweating, injection can accurately supplement and prevent muscle weakness caused by low potassium and hand and foot convulsions caused by low calcium.
3. Acid base balance: HCO ∝⁻ generated by the metabolism of sodium lactate can neutralize excessive acidic substances in the body (such as lactate and ketone bodies produced during metabolic acidosis). This indirect alkaline supplementation method is milder than directly using sodium bicarbonate and is particularly suitable for patients with normal liver function (if liver function is severely impaired and lactate metabolism is impaired, other alkaline solutions may need to be used).

The function of Compound Sodium Lactate Ringer Injection is essentially to simulate the components of extracellular fluid, from three dimensions of osmotic pressure, electrolytes, and acid-base, to help the human body restore internal environmental stability.
---Secondly, the clinical core role of compound sodium lactate Ringer injection can be traced back to the case of the mother: she lost a large amount of digestive fluid (including Na ⁺, K ⁺, HCO ∝⁻) due to frequent vomiting, and dehydration caused a decrease in blood volume, resulting in dry mouth, decreased urine output, and increased heart rate. The doctor chose compound sodium lactate Ringer injection precisely because of its multiple effects of "replenishing fluids, correcting acidity, and regulating electrolytes". In fact, this kind of injection is widely used in clinical practice, and its core functions can be summarized into the following three categories:
(I) Correction of water and electrolyte disorders: the most basic but critical "life supply" water and electrolyte disorders are common complications of many diseases, such as gastroenteritis, burns, major surgery, diabetes ketoacidosis, etc. At this point, patients not only lose water, but also experience the loss of electrolytes such as Na ⁺, K ⁺, and Ca ² ⁺. -Isotonic dehydration (the most common type, where water and electrolytes are lost in proportion): After administration of compound sodium lactate Ringer injection, its isotonic properties can rapidly expand blood volume and replenish lost electrolytes. For example, an adult weighing 60kg with mild isotonic dehydration (losing about 3% of body fluids, or 1.8L) will gradually recover urine output, slow heart rate, and increase blood pressure after infusion of 1000-1500ml. -Hypoosmotic dehydration (more electrolyte loss than water): At this time, the extracellular fluid is in a hypotonic state, and water is transferred into the cell, which may lead to brain edema. Although theoretically, hypotonic dehydration requires the supplementation of hypertonic saline solution, in clinical practice, compound sodium lactate Ringer injection is often used first because its Na ⁺

concentration (130mmol/L) is slightly lower than that of plasma (135-145mmol/L). However, with the body's self-regulation (such as reduced secretion of antidiuretic hormone, promoting water excretion), the hypotonic state can be gradually corrected to avoid vascular irritation caused by hypertonic solution. -Hyperosmotic dehydration (more water loss than electrolytes): At this time, priority should be given to hydration, but compound sodium lactate Ringer injection can still be used as an adjunct - its small amount of K ⁺ and Ca ² ⁺ can prevent dilute hypokalemia and hypocalcemia caused by simple hydration.
Regardless of the type of dehydration, the function of Compound Sodium Lactate Ringer Injection is to "precisely replenish" and restore disrupted water and electrolytes to their original positions.
（2） Maintain acid-base balance: metabolic acidosis is a common acid-base imbalance in clinical practice, which is often seen in severe infection (sepsis), shock (tissue hypoxia leading to lactic acid accumulation), renal insufficiency (acid excretion disorder), diabetes ketosis (excessive ketone body production), etc. At this point, the concentration of HCO ∝⁻ in the body decreases and the pH drops (<7.35). The sodium lactate in compound sodium lactate Ringer injection is metabolized by the liver to produce HCO ∝⁻, which can neutralize excessive H ⁺. Taking sepsis patients as an example, due to insufficient tissue perfusion, cellular hypoxia, enhanced glycolysis, and increased lactate production (normal lactate levels of 1-2 mmol/L can rise to over 4 mmol/L in severe sepsis). At this time, the compound sodium lactate Ringer injection is injected. Although exogenous supplementation of lactic acid is provided, with anti infection treatment and improved circulation (oxygen supply recovery), the liver will accelerate the metabolism of lactic acid, generate HCO ∝⁻, and actually help correct acidosis. It should be emphasized that this "acid to acid" method is only suitable for patients with normal or mildly impaired liver function. If the patient has severe liver failure (such as end-stage cirrhosis), lactate cannot be metabolized, and the infusion may worsen hyperprolactinemia, then sodium bicarbonate injection should be chosen.
（3） Expansion and Microcirculation Improvement: "Basic Fluid" in Shock Treatment The essence of shock is insufficient effective circulating blood volume, leading to tissue perfusion disorders. Early and rapid expansion is key. Compound Sodium Lactate Ringer Injection, as an isotonic crystal fluid, is one of the preferred liquids for shock resuscitation (the other commonly used is 0.9% Sodium Chloride Injection). -Rapid expansion: About 25% of the input remains in the blood vessels (the rest enters the interstitial fluid), but it can quickly increase blood pressure and cardiac output. For example, in patients with hemorrhagic shock, rapid infusion of 1000-2000ml of compound sodium lactate Ringer injection while waiting for blood transfusion can temporarily maintain blood flow to important organs (heart, brain, kidneys). -Improving microcirculation: In addition to supplementing capacity, the K ⁺ and Ca ² ⁺ contained in it also help maintain the function of capillary endothelial cells. Research has shown that compared to simple 0.9% sodium chloride injection, compound sodium lactate Ringer injection can reduce capillary leakage and lower the risk of tissue edema due to its presence of sodium lactate (which can mildly dilate blood vessels) and a more physiological electrolyte concentration.
In the treatment of my mother, the doctor used the triple effects of compound sodium lactate Ringer injection - replenishing water, regulating electrolytes, and correcting acidity. After only 6 hours, her mental state improved significantly, urine output recovered, and blood sodium and potassium returned to normal ranges.
---III. Precautions and Special Scenarios for the Use of Compound Sodium Lactate Ringer Injection Although it is a commonly used liquid in clinical practice, "effectiveness" does not mean "omnipotence". Proper use should be based on the specific situation of the patient to avoid adverse reactions caused by blind infusion.
（1） Adjustment for special populations: It is not a case of "losing everything" - Patients with heart failure: Their heart pumping ability decreases, and rapid and large infusion may induce acute pulmonary edema. It is necessary to control the infusion rate (generally<100ml/h) and monitor central venous pressure (CVP) or pulmonary capillary wedge pressure (PCWP).
-Patients with renal insufficiency: The ability of the kidneys to excrete potassium and sodium decreases, and blood potassium and sodium levels need to be evaluated before infusion. If the patient has developed hyperkalemia (blood potassium>5.5mmol/L), use should be avoided (as the injection contains approximately 4mmol/L of K); If hyponatremia exists, the dosage needs to be adjusted and closely monitored.
-Newborns and the elderly: Newborns with immature liver function (weak lactate metabolism) and the elderly may have concurrent liver and kidney dysfunction, both requiring a reduction in the dosage of sodium lactate (alternative products such as acetic acid Ringer's solution can be used).
（2） Combination and contraindications with other liquids: Caution should be exercised when pairing. Combination with hypertonic saline: In severe hyponatremia (blood sodium<120mmol/L), rapid increase in blood sodium (1-2mmol/L increase per hour) is necessary. At this time, 3% hypertonic saline can be infused first, followed by maintenance with compound sodium lactate Ringer injection to avoid excessive fluctuations in blood sodium.
-Combined use with magnesium containing preparations: Ca ² ⁺ in the injection may antagonize magnesium preparations (such as magnesium sulfate) (Ca ² ⁺ and Mg ² ⁺ compete for receptors at the neuromuscular junction), requiring intermittent infusion. -Taboo compatibility: Cannot be mixed with amphotericin B (which may cause precipitation), ceftriaxone (calcium ceftriaxone precipitation risk) and other drugs for infusion, and should be used separately.
You may wonder: Since it has so many effects, can all dehydration be used? Actually, it's not like that. For example, in patients with hyperkalemia (such as renal failure and oliguria), infusion of compound sodium lactate Ringer injection containing K ⁺ can exacerbate hyperkalemia and may induce arrhythmia; For example, in patients with metabolic alkalosis (such as massive vomiting and loss of gastric acid), the metabolism of sodium lactate to produce HCO ∝⁻ will further aggravate alkalosis. At this time, 0.9% sodium chloride injection should be chosen.

When my mother was discharged from the hospital, the supervising doctor said, "This bottle of liquid may seem simple, but it is our 'basic weapon' - many urgent and severe treatments start with correcting the internal environment." This sentence made me understand that the function of compound sodium lactate Ringer injection is not only to replenish fluids, but also to build a 'stable stage' for the body, allowing its repair mechanism to start smoothly.
From simulating extracellular fluid components to maintaining multidimensional internal environmental balance; From dehydration correction for common gastroenteritis to emergency support for shock and sepsis, this transparent liquid always safeguards the balance of life in a "gentle and precise" manner. It may not have an immediate effect, but it uses the most physiological way to fight for the most precious treatment time for patients.
Next time you see the nurse pushing it towards the ward, will you also have more understanding? This is not a simple 'suspension of water', but a 'gentle confrontation' with the imbalance of life - the effect of compound sodium lactate Ringer injection is so ordinary but great.