Minimum effective fluid volume of colloid to prevent hypotension during caesarean section under spinal anesthesia using a prophylactic phenylephrine infusion: An up-down sequential allocation study.
OBJECTIVE
The aim of this study was to de termine the minimum effective fluid volume (MEFV) of hydroxyethyl starch 130/0.4 (HES) infused in a preload fashion which would prevent hypotension in 50% of parturients undergoing caesarean section. A secondary objective was to measure the hemodynamic effect of fluid loading on the subjects.


METHODS
This is a prospective, double-blinded, dose-finding study using an up-down sequential allocation design.


METHODS
In the operating room.


METHODS
Thirty healthy parturients undergoing caesarean section under spinal anesthesia using a prophylactic phenylephrine infusion were included in this study.


METHODS
The initial HES volume infused in the first patient was 500 mL. A failure of treatment to HES preload was defined as a single episode of systolic hypotension below 20% of baseline value. The next patient in the sequence was given a volume of HES adjusted by either an increment or a decrement of 100 mL according to the previous subject response to fluid preload.


METHODS
Stroke volume and cardiac output were measured with a bioreactance-based non-invasive cardiac output monitor (NICOM).


RESULTS
The MEFV of HES was 733 mL (95% CI: 388-917 mL). Fluid loading before the administration of the spinal anesthesia resulted in an increase in stroke volume and cardiac output. The combined effect of spinal anesthesia and a phenylephrine infusion reduced the maternal heart rate and cardiac output, but not the stroke volume.


CONCLUSIONS
Our study is the first to investigate variable fluid loading volumes in this population. A HES preload of approximatively 700 mL prevented maternal hypotension in 50% of the parturients under the conditions of this study. We suggest that up-down sequential allocation design is a useful tool to compare different fluid loading regimens in this setting.
Maisonneuve-Rosemont Hospital affiliated to the University of Montreal, 5415 boul. L'Assomption, Montreal, (QC), H1T 2M4, Canada. Electronic address: loubertch@yahoo.fr.
Christian
C
Loubert
Maisonneuve-Rosemont Hospital affiliated to the University of Montreal, 5415 boul. L'Assomption, Montreal, (QC), H1T 2M4, Canada. Electronic address: pogagnon@gmail.com.
Pierre-Olivier
PO
Gagnon
University College London Hospitals NHS Foundation Trust, 235 Euston Road, London, NW1 2BU, United Kingdom. Electronic address: roshanagfernando@gmail.com.
Roshan
R
Fernando
D000773:Anesthesia, Obstetrical / Q000009:adverse effects* / Q000379:methods; D000775:Anesthesia, Spinal / Q000009:adverse effects; D002302:Cardiac Output / Q000187:drug effects; D002585:Cesarean Section / Q000379:methods*; D004311:Double-Blind Method; D005260:Female; D005440:Fluid Therapy / Q000379:methods*; D006801:Humans; D006895:Hydroxyethyl Starch Derivatives / Q000008:administration & dosage*; D007022:Hypotension / Q000209:etiology / Q000517:prevention & control*; D010298:Parity; D010656:Phenylephrine / Q000627:therapeutic use; D011247:Pregnancy; D011256:Pregnancy Outcome; D014662:Vasoconstrictor Agents / Q000627:therapeutic use
D006895:Hydroxyethyl Starch Derivatives; D014662:Vasoconstrictor Agents; D010656:Phenylephrine
Caesarean; Colloid; Hemodynamics; NICOM; Phenylephrine; Spinal