Fluid challenge in patients submitted to spinal block.

Area of Science:

• Anesthesiology and Perioperative Medicine
• Cardiovascular Physiology
• Fluid Management

Background:

• Routine prehydration with colloid solutions is commonly used to prevent hypotension following spinal anesthesia.
• Recent evidence challenges the routine use of prehydration, prompting further investigation into its efficacy.
• Understanding the hemodynamic effects of prehydration is crucial for optimizing patient safety during subarachnoid blocks.

Purpose of the Study:

• To evaluate the influence of a 15 mL/kg pre-emptive bolus of 6% hydroxyethyl starch on heart rate (HR), mean arterial blood pressure (MAP), and cardiac index (CI).
• To assess the effectiveness of colloid prehydration in preventing spinal anesthesia-induced hypotension in patients undergoing lower limb orthopedic surgery.
• To compare hemodynamic parameters between patients receiving colloid prehydration and a control group.

Main Methods:

• A randomized controlled study involving 40 patients (ASA I-II) undergoing spinal anesthesia for elective lower limb orthopedic surgery.
• Group A (n=20) received a 15 mL/kg preanesthetic infusion of 6% hydroxyethyl starch; Group B (n=20) served as the control.
• Hemodynamic parameters (HR, MAP, CI) were monitored using a Model Flow method at baseline and at 5-minute intervals for 35 minutes post-spinal block.

Main Results:

• Mean arterial blood pressure (MAP) was significantly higher in the hydroxyethyl starch group compared to the control group (ANOVA: P<0.001).
• A significant decrease in MAP from baseline was observed in the control group at 5 minutes post-spinal block (P<0.05).
• Heart rate and cardiac index trends were similar between groups, and heart rate was not significantly affected by colloid infusion.

Conclusions:

• Despite fluid prehydration with hydroxyethyl starch, a decrease in mean arterial blood pressure could not be entirely prevented.
• The reduction in MAP was less pronounced in the prehydrated group compared to the control group.
• The findings suggest that while prehydration may offer some benefit, it does not completely abolish spinal anesthesia-induced hypotension.