Fluid challenge in patients submitted to spinal block.

AIM: The practice of routinely prehydrating patients by infusing a colloid solution for prevention of spinal anesthesia-induced hypotension has been challenged recently. The aim of the study was to evaluate the influence of a 15 mL/kg pre-emptive bolus of colloids (6% hydroxyhethyl starch) on heart rate (HR), mean arterial blood pressure (MAP), cardiac index (CI) in patients submitted to subarachnoid block with hyperbaric bupivacaine 0.5%, 0.2 mg/kg for orthopedic surgery of the lower limb.

METHODS: Patients were monitored by a Model Flow method. Forty patients (ASA I-II) scheduled to undergo to spinal anesthesia for elective orthopedic surgery of the lower limb were enrolled in the study. The 20 patients in Group A were treated with a preanesthetic infusion of 15 mL/kg of hydroxyhaethyl starch 6%, Group B (20 untreated patients) was the control group. HR, MAP, CI were collected at T0 (first relevation); T1 (after 5 min from the spinal block); T2 (after 10 min); T3 (after 15 min); T4 (after 20 min); T5 (after 25 min); T6 (after 30 min); T7 (after 35 min).

RESULTS: Our data show that MAP value is higher in treated patients than in control group (ANOVA: P<0.001) and at T1 in Group B MAP was lower than at T0 (P<0.05). HR and CI trend appear similar in the 2 groups. Our results show that heart rate is not affected by colloid infusion. This may be due to the substantial cardiovascular stability of the selective spinal anesthesia, which does not activate a clinical relevant compensatory vagal effect. Fluid prehydration would expand the vascular space and hence compensate for the reduction in systemic vascular resistance, although MAP reduction following the induction of spinal anesthesia is present in both treated and control groups.

CONCLUSION: Our data show that despite to fluid challenge, we could not prevent MAP decrease in Group A, even if it is more marked in Group B.