What is the effect of sodium lactate injection? During my internship in the emergency room that day, I witnessed a tense rescue operation. An elderly person who was brought in due to severe diarrhea has a continuous decrease in blood pressure, deep and fast breathing, and the pH value on the monitor shows 7.21- indicating obvious metabolic acidosis. The attending physician quickly scanned the case and turned to the nurse, saying, "Prepare 100ml of 11.2% sodium lactate injection and slowly administer it intravenously. ”The three words "sodium lactate" on the white medicine bottle were illuminated by the light. As I stared at the moment when the medicine entered the elderly's blood vessels, I couldn't help but wonder: isn't sodium lactate "lactic acid"? How can it actually treat acidosis? What exactly is its function? With this question in mind, I embarked on a journey of exploration about sodium lactate injection.
1、 The basic understanding of sodium lactate injection: the key link from molecule to clinical practice. To understand the role of sodium lactate injection, we must first start with its "identity". Sodium lactate is not a direct "alkaline drug", but a "precursor substance" that requires metabolic transformation in the body. Its molecular structure is composed of lactate (CH3CHOHCOO ⁻) and sodium ions (Na ⁺), and it appears as a colorless or almost colorless clear liquid. The commonly used concentration in clinical practice is 11.2% (1.87% for isotonic solution).
（1） The metabolic pathway of sodium lactate: After entering the human body, the "acid-base converter" in the liver, sodium lactate does not directly neutralize acids, but needs to be catalyzed by lactate dehydrogenase in the liver to first convert into pyruvate (CH3COCOO ⁻), which then enters the tricarboxylic acid cycle and ultimately produces carbon dioxide (CO ₂) and water (H ₂ O), while producing bicarbonate (HCO3 ⁻). This process can be simply understood as follows: sodium lactate is the "raw material", the liver is the "factory", and the final product bicarbonate is the true "acid-base regulator".
It is worth noting that this metabolic process is highly dependent on liver function. If the patient's liver function is severely impaired (such as end-stage cirrhosis), sodium lactate cannot be metabolized in a timely manner, and lactate may accumulate in the body, which may actually increase the risk of acidosis. Therefore, the answer to 'what is the effect of sodium lactate injection' has been closely related to the patient's liver condition from the beginning.
（2） The core logic of acid-base balance: understanding the "application" of sodium lactate. The normal pH value of human blood is maintained between 7.35-7.45, which relies on the precise regulation of the "acid-base buffering system". Among them, bicarbonate buffer (HCO3 ⁻/H2CO3) is the most important part, with a normal ratio of 20:1. When various reasons lead to excessive acid production (such as ketone body accumulation in diabetes ketoacidosis) or excessive alkali loss (such as severe diarrhea and loss of HCO3 in intestinal fluid), this ratio will be broken, and the pH value will drop, forming metabolic acidosis.
At this point, the role of sodium lactate is reflected in "supplementing HCO3 ⁻ precursors" - HCO3 ⁻ generated through metabolism can combine with excessive hydrogen ions (H ⁺) to produce H2CO3, which is then decomposed into CO ₂ and H ₂ O. CO ₂ is excreted through respiration, thereby increasing blood pH and restoring acid-base balance. This also explains why sodium lactate can be an effective treatment option in metabolic acidosis patients with normal liver function.
2、 The core function of sodium lactate injection: correcting metabolic acidosis as an "indirect expert". Returning to the original question: "What is the effect of sodium lactate injection?" The core answer can be summarized as: indirectly correcting metabolic acidosis by generating bicarbonate ions through liver metabolism, while supplementing sodium ions to maintain electrolyte balance. But the implementation of this function needs to be understood in conjunction with specific pathological scenarios.
（1） Firefighters in Emergency Situations: Treatment of Severe Metabolic Acidosis In the emergency room, sodium lactate is most commonly used for emergency management of severe metabolic acidosis (pH<7.2). For example:
- Severe diarrhea patients: The intestinal fluid contains a large amount of HCO3 ⁻, and diarrhea leads to a significant loss of HCO3 ⁻, resulting in a relative increase in H ⁺ in the blood. The HCO3 ⁻ generated by the metabolism of sodium lactate can quickly replenish lost alkaline reserves and alleviate acidosis.
-Recovery after cardiac arrest: During cardiac arrest, tissue hypoxia occurs, cellular anaerobic metabolism is enhanced, and lactate accumulates in large quantities (lactic acidosis). After recovery, as blood circulation recovers, liver function gradually recovers. HCO3 ⁻ generated by sodium lactate metabolism can help neutralize residual lactate and prevent acidosis from inhibiting myocardial contractility.
It should be emphasized that the onset of action of sodium lactate is slower than directly supplementing sodium bicarbonate (because it requires metabolic conversion), but its advantage is "mild" - it does not rapidly generate large amounts of CO ₂ like sodium bicarbonate (which may exacerbate intracellular acidosis), nor does it lead to hypernatremia (at the same dose, the sodium content of sodium lactate is lower than that of sodium bicarbonate).
（2） Long term supporters in chronic scenarios: adjuvant therapy for special diseases. In addition to emergency treatment, sodium lactate also plays a unique role in chronic disease management. For example:
- Chronic renal insufficiency: The kidneys are the main organs for excreting H ⁺ and reabsorbing HCO3 ⁻. When renal insufficiency occurs, HCO3 ⁻ production decreases and acid excretion is impaired. At this time, low-dose sodium lactate can be used as a substitute for long-term oral alkali supplementation (such as sodium lactate solution) to avoid excessive sodium load caused by long-term use of sodium bicarbonate (especially for patients with hypertension and edema).
-Hereditary renal tubular acidosis: These patients suffer from chronic metabolic acidosis due to impaired reabsorption of HCO3 ⁻ in the renal tubules or functional defects in H ⁺ excretion. Sodium lactate is metabolized to produce HCO3 ⁻, which can continuously replenish alkaline reserves and alleviate complications such as growth retardation and bone softening.
（3） The "balance guardian" during the perioperative period: During the acid-base regulation of surgical stress, patients may experience metabolic acidosis due to factors such as fasting, blood loss, anesthesia, etc. For example, a large amount of blood transfusion during major surgery (due to the presence of citrate in the stored blood, which reduces the production of HCO3 ⁻ after metabolism) and tissue hypoxia caused by prolonged hypotension (lactate accumulation) require timely adjustment of acid-base balance. At this time, sodium lactate is often used to maintain pH stability during surgery, reduce the risk of arrhythmia, coagulation disorders, etc. due to its metabolic dependence on the liver (most surgical patients have relatively normal liver function) and low sodium load.
3、 The "boundary of use" of sodium lactate injection: the key to safe medication. Although sodium lactate plays a significant role in correcting metabolic acidosis, the complete answer to "what is the effect of sodium lactate injection" must include an understanding of its limitations and risks - only reasonable use can maximize treatment benefits.
（1） Dose and speed: The scientific control of "too much or too little" requires comprehensive adjustment of the dose of sodium lactate based on the patient's degree of acidosis (calculated by BE value in blood gas analysis), body weight, and liver function. The commonly used clinical formula is: required sodium lactate (mmol)=(normal BE value - measured BE value) × body weight (kg) × 0.3 (normal BE value is 3mmol/L). Taking 11.2% sodium lactate injection as an example (containing 1mmol of sodium lactate per ml), the initial dose for adults is usually 100-200ml, slowly administered intravenously (not exceeding 3ml per minute, i.e. 3mmol/min).
If the infusion is too fast or the dosage is too large, it may lead to: - Hypernatremia: excessive intake of sodium ions can cause edema and elevated blood pressure, especially in patients with heart failure, which may trigger acute heart failure;
Metabolic alkalosis: excessive production of HCO3 ⁻, pH value exceeding 7.45, leading to increased excitability of nerves and muscles (such as hand and foot convulsions), left shift of oxygen dissociation curve (aggravated tissue hypoxia); -Lactic acid accumulation: When liver function is impaired, sodium lactate cannot be metabolized in a timely manner, leading to the accumulation of lactate ions and exacerbating acidosis (in this case, sodium bicarbonate should be used instead).
（2） Taboos and caution: Three groups of people need to take a detour, not all acidosis patients are suitable for sodium lactate. The following situations should be disabled or used with caution: 1 Severe liver dysfunction (such as acute liver failure, decompensated cirrhosis): The liver is unable to metabolize sodium lactate, and there is a high risk of lactate accumulation; two Lactic acidosis (such as excessive lactate production caused by sepsis and shock): At this time, the patient's lactate level has exceeded the standard, and the use of sodium lactate may further exacerbate lactate accumulation; three Hypernatremia or heart failure: Sodium lactate contains sodium ions, which can increase blood sodium concentration and circulatory burden, potentially exacerbating the condition.
（3） Monitoring and adjustment: During the use of sodium lactate in the dynamic observation "treatment loop", the following indicators must be closely monitored: - Blood gas analysis: pH, HCO3 ⁻, BE values are measured every 1-2 hours to evaluate the correction of acidosis; -Blood electrolytes: Pay close attention to blood sodium and potassium (after correction of acidosis, potassium ions may transfer into cells, which may lead to hypokalemia); -Liver function: Monitor blood lactate levels in patients with liver disease. If lactate levels continue to rise, medication should be stopped promptly; -Vital signs: Observe respiratory rate (after correction of acidosis, deep breathing will weaken) and heart rate (heart rate increases during acidosis and tends to be normal after correction).
4、 Comparison and Reflection: Sodium Lactate vs. Other Alkaline Drugs. You may ask, "Since sodium bicarbonate can directly neutralize acid, why use sodium lactate?" This requires comparing the characteristics of different alkaline drugs (not using a table here, using paragraphs to explain):
- Sodium bicarbonate: directly provides HCO3 ⁻, takes effect quickly (10-20 minutes), but the disadvantage is that it may lead to excessive production of CO ₂ (requiring patients to have normal respiratory function to eliminate CO ₂), high risk of hypernatremia (1g of sodium bicarbonate contains 11.9mmol of sodium), and rapid infusion may cause intracellular acidosis (CO ₂ penetrates the cell membrane faster than HCO3 ⁻, and the intracellular pH may decrease instead). -Sodium lactate: It takes 30-60 minutes to take effect, but there is no additional burden of CO ₂ after metabolism (the generated CO ₂ is a normal metabolite), and the sodium content is low (1g of sodium lactate contains 5.5mmol of sodium), making it more suitable for patients with normal liver function, long-term alkaline supplementation, or sodium load sensitivity. -Trimethylaminomethane (THAM): It can simultaneously neutralize acids inside and outside the cell, does not rely on respiration to excrete CO ₂, but may cause hypoglycemia, hyperkalemia, and is expensive and rarely used in clinical practice.
Therefore, the answer to "what is the effect of sodium lactate injection" needs to be understood within the framework of "individualized treatment" - selecting the most suitable alkaline medication based on the patient's liver function, acid tolerance, heart and kidney function, etc.
After the rescue was completed that day, I specifically checked the follow-up situation of the elderly person: after intravenous injection of sodium lactate for 30 minutes, the pH of the blood gas was rechecked to 7.32, the breathing gradually stabilized, and the blood pressure also returned to the normal range. The attending physician said, "Although this medicine does not directly 'anti acid', it is actually safer through liver metabolism conversion." At that moment, I finally understood that the effect of sodium lactate was far beyond the four words' alkaline drugs' - it was a 'bridge' in the human metabolic network and a 'regulatory key' selected by doctors based on the patient's condition.
From emergency rescue in the emergency room to long-term management of chronic diseases, sodium lactate injection has always been an important tool for regulating acid-base balance due to its unique mechanism of action. Its "function" is not only chemical acid-base neutralization, but also precise maintenance of the homeostasis of life - by respecting the metabolic laws of the human body itself, it corrects pathological states while minimizing interference with physiological functions.
The next time we see that white medicine bottle, we can both understand that it contains not only medicinal solutions, but also medical understanding and reverence for the complexity of life. When we ask 'what is the effect of sodium lactate injection', the answer may be hidden in that simple summary: it is a 'metabolic assistant' that helps the body regain balance, and an 'invisible guardian' that safeguards the stability of life.
