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. CONCLUSION: 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.

Volume kinetics of Ringer's solution during induction of spinal and general anaesthesia.

The kinetics of an i.v. infusion of 20 ml x kg(-1) of Ringer's solution over 60 min was studied in patients undergoing spinal (n=10) and general (n=10) anaesthesia. The induction resulted in similar changes in volume kinetic parameters in both groups. When a one-volume model was employed (n=8), however, the infusion expanded a smaller body fluid space in the four patients who had received preoperative enteric lavage (3.3 vs 8.3 litres), which is consistent with hypovolaemia. When a two-volume model was statistically justified (n=12), the induction reduced the rate of fluid equilibration between a fairly small central (V1, mean 1.4 litres) and a peripheral body fluid space by about 50% (P<0.01). The kinetic analysis suggested that a rapid fluid load of 350 ml given over 2 min just after the induction could possibly prevent arterial hypotension because of central hypovolaemia. This was confirmed in five additional patients.

High-dose intravenous infusion of irrigating fluids containing glycine and mannitol in the pig.

BACKGROUND: Large-scale absorption of electrolyte-free irrigating fluid during endoscopic surgery may result in a "transurethral resection syndrome." The severity of the syndrome can probably be modified by using mannitol 5% instead of the most widely used glycine 1.5%. METHODS: Seventeen pigs with a mean body weight of 22 (range 19-26) kg received an intravenous infusion of 100 mL kg(-1) h(-1) of either glycine 1.5% or mannitol 5% over 90 min. Central hemodynamics, whole-body and brain oxygen consumption, intracranial pressure, blood hemoglobin, and the sodium concentrations in serum and urine were monitored for 120 min. Selected measurements were made on 6 other pigs given mannitol 3% and in 2 controls not given any fluid. Morphological examinations of the hearts were conducted. RESULTS: Both glycine 1.5% and mannitol 5% transiently increased cardiac output, the aortic blood flow rate, and arterial pressures, but all of these parameters fell to below baseline after the infusions were ended. The intracranial pressure was lower (P < 0.05) and the oxygen consumption in the brain decreased (P < 0.001) during the infusion of mannitol 5%. Glycine 1.5% expanded the intracellular volume more than mannitol did (P < 0.002). Signs of myocardial damage were graded glycine 1.5% > mannitol 5% > mannitol 3%. CONCLUSIONS: Massive infusion of glycine 1.5% and mannitol 5% left the pigs in a hypokinetic hypotensive state. Glycine 1.5% increased the intracranial pressure and injured the myocardium more than mannitol 5%, which then seems to be a more appropriate irrigating fluid to use during endoscopic surgery.

Beta 2-adrenergic responsiveness in vivo during abdominal surgery.

We have studied adrenergic function in vivo during anaesthesia and surgery. Epinephrine 50 ng kg-1 min-1 was given by i.v. infusion over 30 min to 10 healthy adult volunteers and to 10 patients undergoing abdominal operations. The cAMP response to stimulation by epinephrine, which was obtained as the area under the curve (AUC) for plasma cAMP concentration divided by the AUC for plasma concentration of epinephrine, was more pronounced during surgery (mean ratio 3.5) than in the control situation (ratio 1.4; P < 0.02). This resulted in greater hypokalaemic and hyperglycaemic responses (ratios -0.67 and 4.5) than in the control group (ratios -0.33 and 1.6, respectively; P < 0.004). Mean arterial pressure decreased in the control group while it increased in the study group, and serum cortisol concentration was higher in those who underwent surgery (P < 0.02). These results are consistent with an increased adrenergic response during abdominal surgery.