Fluid Resuscitation in Critically Ill Patients - Pros and Cons

Introduction:-

Intravenous fluids have always been considered 'safe,' so very few studies were performed until recently. However, they are considered drugs, and several pieces of research are being performed. Using intravenous fluids to increase or maintain the water content or hydration in patients is a general and critical procedure in an I.C.U. Different fluids have different effects on various diseases, populations, and gender.

What Is Fluid Resuscitation?

Fluid resuscitation (the process of reviving someone) is carried out in the I.C.U. on patients with infection, shock, or burns. Intravenous fluids have always been considered 'safe,' so very few studies were performed until recently. They are considered drugs, and quite a few researches have been performed.

However, the choice of resuscitation (process of reviving someone) fluids remains a matter of argument. The selection of appropriate fluid affects the patient outcome. Saline has been a unanimous choice as a resuscitation fluid. However, as various studies are being carried out, using saline as a resuscitation fluid for critically-ill patients has become questionable. It has been found that the high chloride content of saline may develop acute kidney injury (A.K.I.) in patients.

Another possible choice of fluid is buffered crystalloid or balanced crystalloid. Buffered crystalloids were first used for resuscitating patients during the London cholera epidemic in 1832. Buffered crystalloids are intravenous fluids whose composition closely resembles the blood plasma (the fluid part of the blood). However, it is still doubtful whether the use of balanced crystalloids can improve the condition of patients. Therefore, let us study both fluids in detail.

What Is Normal Saline?

It is a mixture of sodium chloride and water. Normal saline is used as an intravenous fluid and has 0.9% of sodium chloride. It is a crystalloid fluid.

What Are the Cons of Using Saline as a Resuscitation Fluid?

1. It has been found to negatively affect patients with metabolic acidosis. The high chloride content or hyperchloraemia of saline in critically ill septic patients has been proven to be fatal.

2. Hyperchloraemia has been found to decrease the flow of blood and fluids in the kidney. This happens due to the constriction of the blood vessels in the kidney due to an increase in the chloride content. This leads to an acute kidney injury (A.K.I.). In critically ill I.C.U. patients' A.K.I. can prove fatal.

3. Normal saline may cause low blood pressure or hypotension.

4. Few studies have found normal saline to trigger the release of inflammatory mediators.

5. Normal saline is thought to negatively affect the body's reaction to an injury causing bleeding during operative procedures. A high-risk group of patients who underwent surgery and had increased transfusion requirements associated with normal saline was recognized.

6. Saline resuscitation may lead to postoperative nausea and vomiting.

What Are the Pros of Using Saline as a Resuscitation Fluid?

1. Normal saline has been the preferred resuscitation fluid for a long time. Unless and until relevant and strong evidence of a better alternative comes to light, normal saline will remain the preferred choice of fluid.

2. Most of the anti-saline studies are observational. No randomized controlled trials were performed while conducting the studies. It is unclear whether the hyperchloraemia associated with normal saline administration is due to an increase in the volume of saline used during resuscitation or the chloride amount in normal saline.

3. Sodium and chloride are found in the extracellular fluid (fluid outside the cells). The presence of these ions in the resuscitation fluids is favorable as they can be retained in their respective compartments.

4. Normal saline is cost-effective. Replacing saline with an expensive alternative does not make sense.

What Are Buffered Crystalloids?

These are the resuscitation solutions in which the chloride ion is replaced by bicarbonate to reduce the disturbance created in the acid base that results from the intravenous fluid administration. Lactated Ringer's solution, Hartmann solution, or Plasma Lyte are some of the buffered crystalloids.

What Are the Cons of Using Buffered Crystalloids?

1. The buffered crystalloids do not come close to the composition and concentration of the extracellular fluids in the human body.

2. Buffered crystalloids are hypotonic solutions. This means they have a lower concentration than the concentration of the extracellular fluid. Hence a generous administration of these could cause cerebral edema- swelling of the brain.

3. The presence of calcium in them can inactivate the administered antibiotics.

4. Some buffered crystalloids have been found to decrease heart function.

5. Excess use of buffered crystalloids can cause an increase in the alkali content of the body- Alkalosis.

6. Since buffered crystalloids are hypotonic, they may lead to hyponatremia - a decrease in the concentration of sodium in the body of critically ill patients.

What Are the Pros of Using Buffered Crystalloids?

1. In patients with a disturbed acid-base balance, balanced crystalloids should be used for resuscitation.

2. It is a good choice for acidosis patients like diabetic ketoacidosis, as the alkaline nature of the buffered crystalloid will maintain the balance.

3. It may decrease the risk of developing A.K.I. in critically ill patients.

4. By increasing the recovery rate in patients with acidosis, the I.C.U. discharge can be fast, reducing the overall treatment cost.

5. In diabetic ketoacidosis (DKA), the recovery rate is delayed due to hyperchloraemia. In such cases, it is advised to use buffered crystalloids rather than normal saline.

What Are the Conditions Where Fluid Resuscitation Is Recommended?

Fluid resuscitation is primarily indicated in the following conditions:

• During Surgery - A balanced crystalloid should be used if there is a risk of A.K.I. (acute kidney injury) or I.V. fluid needed is more than 2 liters.

• In the Case of Sepsis - Balanced crystalloids should be used.

• Traumatic Brain Injury - Normal saline 0.9% should be used.

• Special cases needing individual attention include, diabetes, diabetic ketoacidosis, severe hyperkalemia, renal dysfunction, abnormal sodium concentration, and acid-base balance.

Conclusion:-

Statistical analysis, such as meta-analysis, combining results from different scientific studies, shows no mortality difference between the saline and buffered crystalloid groups. However, balanced crystalloids have been found to reduce the mortality risk in non-TBI (traumatic brain injury) patients. Evidence from several studies also suggests that using buffered crystalloids over normal saline may reduce the mortality rate in critically ill patients. Randomized trials have found that buffered crystalloids cause less hyperchloremic metabolic acidosis during major surgeries. However, we need large-scale randomized trials with better designs to arrive at a definite conclusion.