Infusion therapy: when it is needed and what solutions are used

Infusion therapy is the targeted intravenous administration of solutions to restore blood volume, organ perfusion, fluid and electrolyte balance, and acid-base balance. It is used in cases of dehydration, shock, sepsis, major surgery, severe infections, and a number of metabolic disorders when oral fluid replacement is impossible or insufficient. A modern approach requires an individualized assessment of indications and regular reassessment of the response to therapy.

The key decision-making framework is "right patient, right reason, right solution, right volume, right rate, with mandatory reassessment." This approach is enshrined in updated clinical guidelines and emphasizes that infusions are not a "just-in-case" drip, but a controlled intervention with measurable goals.

Reassessment is performed repeatedly, including heart rate, blood pressure, peripheral blood flow indices, oxygen saturation, respiration, temperature, urine output, electrolytes, creatinine, acid-base indices, and lactate. In critical conditions, dynamic preload tests, such as the leg raise test and stroke volume monitoring, are preferred over the isolated interpretation of static indices. [1]

For both elective and emergency surgeries, the infusion strategy is developed based on the treatment phase: initial resuscitation, optimization, stabilization, and then "elimination" of excess fluid. This phased approach reduces the risk of volume overload and complications associated with a positive balance. [2]

Table 1. Checklist before starting infusions

Question	What needs to be clarified
Target	Resuscitation, maintenance, replenishment of losses, correction of electrolytes
Solution	Balanced crystalloid or saline solution, colloid for specific indications
Volume	Initial calculation based on weight and clinical situation, with a reassessment plan
Speed	Boluses for shock, slower for maintenance
Monitoring	Diuresis, hemodynamic parameters, electrolytes, lactate

Solution Selection: Crystalloids vs. Colloids

Crystalloids are the primary choice. Balanced solutions are closer in composition to plasma and, as shown by large studies in hospital and intensive care unit patients, are associated with a lower risk of adverse renal outcomes compared with 0.9 percent saline, although the results of individual randomized trials vary and the effect is small. The choice between balanced solutions and 0.9 percent saline should be made taking into account the clinical situation and the risk of hyperchloremia.

A 0.9 percent sodium chloride solution can cause hyperchloremic acidosis and has been associated with acute kidney injury in observational and some randomized studies. This is not an absolute contraindication, but it does suggest that balanced crystalloids should be preferred in most unstable patients, especially with large infusion volumes. [4]

Colloidal solutions of hydroxyethyl starch have been subject to regulatory restrictions in Europe due to an increased risk of renal complications and mortality in certain patient groups. In 2022, European regulators confirmed the decision to suspend approval of these products, reflecting an unfavorable benefit-risk balance. [5]

Albumin as a colloid has not demonstrated an overall survival benefit in large cohorts, but may be used in certain scenarios when indicated. Randomized trials in critically ill patients have shown no difference in 28-day mortality compared to crystalloids in the overall population, with some significant differences in subgroups that require cautious interpretation.

Table 2. Common crystalloids: where appropriate

Solution	Peculiarities	Typical situations
Balanced crystalloid	Closer to plasma ions, below chlorine	Most resuscitation and maintenance scenarios
Sodium chloride 0.9 percent	Risk of hyperchloremic acidosis with large volumes	Head injury, hyponatremia due to sodium loss, combined with blood transfusion
Hypertonic sodium chloride 3 percent	For emergency correction of severe symptomatic hyponatremia	Acute neurological symptoms due to hyponatremia

Maintenance infusions in adults: how much and what

For routine maintenance in adults without signs of hypovolemia, the following daily requirements are used: fluid approximately 25-30 ml per kg of body weight, sodium approximately 1 mmol per kg, potassium approximately 1 mmol per kg, and glucose 50-100 g. Correction is important for fragile patients, patients with heart or renal failure, for whom the volume and rate are reduced, and monitoring is increased.

Maintenance fluids are often prepared from a balanced crystalloid with potassium added based on the patient's needs, or from ready-made mixtures tailored to the individual's needs. In cases of coronavirus infection, sepsis, and postoperative care, the priority is to avoid both overload and underload, so volumes are adjusted based on diuresis and electrolyte dynamics, with frequent reassessment.

For obese individuals, calculations are based on adjusted body weight; for the elderly, daily volumes are reduced, with special attention to sodium to prevent iatrogenic hyponatremia. Fluid intake from medications and food, as well as hidden losses, are always taken into account.

Hypotonic maintenance solutions should not be prescribed to adults unless strictly indicated, as this increases the risk of hyponatremia. Prevention involves choosing isotonic or balanced solutions and strict sodium monitoring during the first 24 hours.

Table 3. Example of calculation of maintenance infusion in an adult

Parameter	70 kg: daily guideline
Water	1,750-2,100 ml
Sodium	about 70 mmol
Potassium	about 70 mmol
Glucose	50-100 g
Corrections	Elderly age, cardiac or renal failure - reduce volume and speed, strengthen control

Maintenance infusions in children: transition to isotonic solutions

For children aged 28 days to 18 years, isotonic solutions with added potassium and glucose are recommended for maintenance, significantly reducing the risk of hyponatremia compared to hypotonic formulas. Exceptions are made for certain groups specified in guidelines. This is a fundamental shift in recent years, enshrined in clinical recommendations. [6]

Implementation of this approach in hospitals demonstrates safety and a reduction in hyponatremia with proper composition and monitoring. Medical quality improvement programs confirm the feasibility of widespread implementation of the isotonic strategy. [7]

In real-life practice, the choice of a specific isotonic solution is made taking into account age, concomitant conditions, and laboratory parameters. Hypotonic solutions are generally avoided outside the neonatal period. [8]

Newborns under 28 days have different requirements; they are monitored using specialized protocols. It's important to note that any calculations for children require more frequent sodium and glucose monitoring than for adults. [9]

Table 4. Maintenance infusions in children: quick guidelines

Age	Basic principle	Why is this important?
From 28 days to 18 years	Isotonic solution with potassium and glucose	Reducing the risk of hyponatremia
Newborns up to 28 days	Special protocols	Features of water-electrolyte metabolism
Any age at risk of hyponatremia	Monitor sodium more often	Prevention of seizures and cerebral edema

Resuscitation in shock and sepsis: volume, rate, control

If sepsis with hypoperfusion is suspected, initial infusion resuscitation is performed with balanced crystalloid boluses, aiming to improve perfusion and diuresis. International guidelines recommend a volume of approximately 30 ml/kg in the first few hours, with mandatory reassessment based on dynamic parameters, avoidance of overload, and timely addition of vasopressors if necessary. [10]

Balanced crystalloids are considered the preferred option in this group of patients, given evidence of reduced combined renal outcomes and oxygen debt in several studies, although the benefit in terms of overall mortality is unclear. The choice should take into account concomitant head injury, where balanced solutions, like albumin, may not be the best choice. [11]

Monitoring the effectiveness of resuscitation includes clinical evaluation, urine output, lactate, and dynamic fluid response tests. A "quickly administer - quickly check - quickly adjust" strategy is superior to prolonged, unmonitored infusions. [12]

When combining infusions with blood transfusions, it is important to remember about compatibility: it is safe to use 0.9 percent saline solution of sodium chloride through the same line along with blood components; solutions containing calcium are administered through a separate line. [13]

Table 5. Algorithm for initial infusion support in sepsis

Step	Action	Explanation
1	Balanced crystalloid boluses	Approximately 30 ml per kg with revaluation
2	Dynamic response assessment	Leg raise test, stroke volume
3	Early vasopressor if no response	Reducing fluid overload
4	Monitoring lactate and diuresis	Goals of perfusion and renal protection

Correction of electrolytes and acid-base balance

Severe symptomatic hyponatremia requires immediate treatment with 150 mL boluses of 3% hypertonic saline to raise sodium by 5 mmol/L within the first hour, followed by a strict rate of correction. This rapidly reduces the risk of cerebral edema and seizures while minimizing the risk of osmotic demyelination. [14]

Safe limits for sodium correction are generally no more than 10 mmol/L in the first 24 hours and no more than 8 mmol/L thereafter, with more stringent limits in patients with risk factors. Regular repeat sodium measurements are essential, especially with high diuresis or after multiple boluses of hypertonic saline. [15]

For cholera and other severe dehydration, the first-line intravenous therapy remains lactated Ringer's solution, with rapid administration of large volumes according to standardized plans, followed by a transition to oral rehydration solutions. If lactated Ringer's solution is unavailable, 0.9 percent sodium chloride solution can be used. [16]

Administration of 0.9 percent sodium chloride solution in large volumes can lead to hyperchloremic acidosis and deterioration of renal perfusion, therefore, in the planned correction of metabolic disorders, balanced crystalloids are preferable unless there are specific contraindications. [17]

Table 6. Electrolyte Emergencies: Quick Reference Points

Situation	What to do	What to look at
Symptomatic hyponatremia	Boluses of hypertonic sodium chloride with a concentration of 3 percent, 150 ml	An increase in sodium of 5 mmol per liter in 1 hour, then no more than 10 mmol per liter in 24 hours
Severe dehydration in cholera	Lactated Ringer's solution according to the rapid rehydration plan, then oral solution	Pulse, consciousness, diuresis, sodium, potassium
Hyperchloremic acidosis after large volumes of sodium chloride at a concentration of 0.9 percent	Transition to balanced crystalloid, correction of blood gases	Chlorine, bicarbonate, lactate

Safety: How to Avoid Complications of Infusion Therapy

The main risks are volume overload with pulmonary edema, hyponatremia when using hypotonic solutions, hyperchloremic acidosis and acute kidney injury with large volumes of 0.9 percent sodium chloride, and catheter-related risks. Complications are minimized by proper solution selection, dosage, and strict monitoring. [18]

In critically ill patients, the safety package includes an early transition from aggressive resuscitation to cautious optimization and stabilization, followed by targeted fluid management. This phased approach reduces the incidence of pulmonary and renal complications. [19]

Hydroxyethyl starch colloids are not used due to their unfavorable safety profile and regulatory decisions in force in Europe. If a colloid is necessary, albumin is considered only in strict indications, keeping in mind the lack of a universal survival advantage. [20]

When simultaneously transfusing blood, the compatible solution in the common line remains a 0.9 percent sodium chloride solution; calcium-containing solutions should not be used in the same system due to interaction with citrate. This simple rule prevents clotting in the system and catheter thrombosis. [21]

Table 7. Minimum monitoring during infusion therapy

Indicator	Frequency	Target
Diuresis	Hourly for unstable	Not less than 0.5 ml per kg per hour in adults
Sodium, potassium, creatinine	During the first day, every 6-12 hours at risk	Prevention of hyponatremia and renal dysfunction
Lactate	According to indications, every 2-6 hours	Perfusion and response assessment
Fluid balance	Every day	Avoid a positive balance unnecessarily

Common mistakes and how to prevent them

Mistake #1 is giving large volumes of 0.9 percent sodium chloride solution without indication, which increases the risk of hyperchloremia and renal complications. Choosing a balanced crystalloid reduces these risks in most scenarios. [22]

Mistake #2: Prescribing hypotonic maintenance solutions, especially to children, increases the risk of hyponatremia and neurological complications. Current guidelines prioritize isotonic solutions. [23]

Mistake #3: Failure to reassess after boluses in shock, leading to volume overload. Dynamic testing and a cautious approach after initial stabilization improve results. [24]

Mistake #4: Infusing calcium-containing solutions through the same line as blood. A separate line is used for blood components, or only a 0.9 percent sodium chloride solution is used in the general system. [25]

Table 8. What to choose in typical clinical situations

Situation	Preferred approach
Most clinical scenarios	Balanced crystalloid, reassessed every 15-30 minutes if unstable
Sepsis with hypoperfusion	Starting boluses, early reassessment, cautious follow-up tactics
Severe dehydration in cholera	Ringer's lactate solution according to the rapid rehydration standard
Simultaneous transfusion	Through the common line only sodium chloride solution with a concentration of 0.9 percent
Severe symptomatic hyponatremia	Boluses of hypertonic sodium chloride solution with a concentration of 3 percent with strict control of the rate of correction

Brief summary

Modern infusion therapy is based on a clearly defined goal, appropriate solution selection, moderate volumes, dynamic response assessment, and strict safety monitoring. In most cases, balanced crystalloids are preferred; in children, isotonic mixtures are used for maintenance. Backup decisions and exceptions are determined by the specific clinical situation and current guidelines. [26]