Bolus injection of Ringer's solution and dextran 1 kDa during induction of spinal anesthesia.
BACKGROUND
Arterial hypotension following induction of spinal anesthesia is difficult to prevent with infusion fluids. In a randomized, unblinded and controlled study we evaluated whether a rapid fluid administration planned according to volume kinetic analysis is followed by a more stable blood pressure.


METHODS
Spinal anesthesia was induced in 75 surgical patients, using one of three different fluid regimens: intravenous 'bolus injection' of 5 ml kg(-1) of Ringer's acetate over 3 min, 2 ml kg(-1) of low-molecular weight (1 kDa) dextran over 3 min, or a constant-rate infusion of 15 ml kg(-1) of Ringer's acetate over 40 min (controls). The kinetics of the fluid was studied in five patients in each group and also in eight volunteers.


RESULTS
The decrease in mean arterial pressure averaged 28%, 27% and 26%, respectively, and was fully developed 16 min after the induction. The height of the block, but not the fluid programme, correlated with the hypotension. Nausea or near-fainting associated with marked hypotension or bradycardia was recorded in none, five (20%) and two (8%) of the patients, respectively. Both bolus injections were followed by translocation of fluid from the peripheral tissues to the bloodstream, which maintained the plasma dilution at about 10% for at least 30 min until surgery began.


CONCLUSIONS
A brisk infusion of Ringer's solution or dextran 1 kDa over 3 min was followed by the same decrease in arterial pressure as a longer and 3-5-times larger infusion of Ringer's solution over 40 min during induction of spinal anesthesia.
Ewaldsson
C-A
CA
Department of Anesthesia, South Hospital, Stockholm, Sweden.
Hahn
R G
RG
D000368:Aged; D000775:Anesthesia, Spinal / Q000379:methods*; D000925:Anticoagulants / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001794:Blood Pressure / Q000187:drug effects; D003911:Dextrans / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007022:Hypotension / Q000517:prevention & control*; D007552:Isotonic Solutions / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D008970:Molecular Weight; D019637:Orthopedic Procedures / Q000379:methods; D012016:Reference Values; D000077331:Ringer's Solution; D013997:Time Factors
D000925:Anticoagulants; D003911:Dextrans; D007552:Isotonic Solutions; D000077331:Ringer's Solution