Support of mean arterial pressure during tepid cardiopulmonary bypass: effects of phenylephrine and pump flow on systemic oxygen supply and demand

Conventional hemofiltration during cardiopulmonary bypass increases the serum lactate level in adult cardiac surgery

OBJECTIVE

To evaluate the effect of hemofiltration during cardiopulmonary bypass on lactate level in adult patients who underwent cardiac surgery.

DESIGN

An observational study.

SETTING

Prince Sultan cardiac center, Riyadh, Saudi Arabia.

PARTICIPANTS

The study included 283 patients classified into two groups: Hemofiltration group (n=138), hemofiltration was done during CPB. Control group (n = 145), patients without hemofiltration.

INTERVENTIONS

Hemofiltration during cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

Monitors included hematocrit, lactate levels, mixed venous oxygen saturation, amount of fluid removal during hemofiltration and urine output. The lactate elevated in group H than group C (P < 0.05), and the PH showed metabolic acidosis in group H (P < 0.05). The mixed venous oxygen saturation decreased in group H than group C (P < 0.05). The number of transfused packed red blood cells was lower in group H than group C (P < 0.05). The hematocrit was higher in group H than group C (P < 0.05). The urine output was lower in group H than group C (P < 0.05).

CONCLUSIONS

Hemofiltration during cardiopulmonary bypass leads to hemoconcentration, elevated lactate level and increased inotropic support. There are some recommendations for hemofiltration: First; Hemofiltration should be limited for patients with impaired renal function, positive fluid balance, reduced response to diuretics or prolonged bypass time more than 2 hours. Second; Minimal amount of fluids should be administered to maintain adequate cardiac output and reduction of priming volumes is preferable to maintain controlled hemodilution. Third; it should be done before weaning of or after cardiopulmonary bypass and not during the whole time of cardiopulmonary bypass.

Sheep (Ovis aries) as a model for cardiovascular surgery and management before, during, and after cardiopulmonary bypass

Because of its similarity to humans in important respects, sheep (Ovis aries) are a common animal model for translational research in cardiovascular surgery. However, some unique aspects of sheep anatomy and physiology present challenges to its use in these complicated experiments. In this review, we discuss relevant anatomy and physiology of sheep and discuss management before, during, and after procedures requiring cardiopulmonary bypass to provide a concise source of information for veterinarians, technicians, and researchers developing and implementing protocols with this model.

A hyperosmolar-colloidal additive to the CPB-priming solution reduces fluid load and fluid extravasation during tepid CPB

Cardiopulmonary bypass(CPB) is associated with fluid overload. We hypothesized that fluid gain during CPB could be reduced by substituting parts of a crystalloid prime with 7.2% hypertonic saline and 6% poly(O-2-hydroxyethyl) starch solution (HyperHaes®). 14 animals were randomized to a control group (Group C) or to Group H. CPB-prime in Group C was Ringer’s solution. In group H, 4 ml/kg of Ringer’s solution was replaced by the hypertonic saline / hydroxyethyl starch solution. After 60 min stabilization, CPB was initiated and continued for 120 min. All animals were allowed drifting of normal temperature (39.0°C) to about 35.0°C. Fluid was added to the CPB circuit as needed to maintain a 300-ml level in the venous reservoir. Blood chemistry, hemodynamic parameters, fluid balance, plasma volume, fluid extravasation rate (FER), tissue water content and acid-base parameters were measured/calculated. Total fluid need during 120 min CPB was reduced by 60% when hypertonic saline/hydroxyethyl starch solution was added to the CPB prime (p<0.01). The reduction was related to a lowered FER. The effect was most pronounced during the first 30 min on CPB, with 0.6 (0.43) (Group H) compared with 1.5 (0.40) ml/kg/min (Group C) (p<0.01). Hemodynamics and laboratory parameters were similar in both groups. Serum concentrations of sodium and chloride increased to maximum levels of 148 (1.5) and 112 (1.6) mmol/l in Group H. To conclude: addition of 7.2% hypertonic saline and 6% poly(O-2-hydroxyethyl) starch solution to crystalloid CPB prime reduces fluid needs and FER during tepid CPB.

Elevated flow rate during cardiopulmonary bypass is associated with fluid accumulation

OBJECTIVE

High flow rates during cardiopulmonary bypass are assumed to increase fluid accumulation. This study aimed to determine whether two different flow rates during cardiopulmonary bypass alter the intraoperative fluid balance and extravasation rate.

METHODS

Sixteen pigs underwent 60 minutes of normothermic bypass, followed by 90 minutes of hypothermic bypass. A high-flow group (HF group, n = 8) had a cardiopulmonary bypass flow rate of 110 mL x kg(-1) x min(-1) and a low-flow group (LF group, n = 8) had a rate of 80 mL x kg(-1) x min(-1). Blood chemistry, hemodynamic parameters, plasma and interstitial colloid osmotic pressure, net fluid balance, plasma volume, fluid extravasation rate, and total tissue water content were measured or calculated. Results are presented as mean (standard deviation).

RESULTS

The average net fluid balance during cardiopulmonary bypass was 1.02 (0.25) and 0.73 (0.23) mL x kg(-1) x min(-1) in the HF group and LF group, respectively (P < .05). The average fluid extravasation rate was 0.98 (0.22) and 0.77 (0.22) mL x kg(-1) x min(-1) in the HF group and the LF group (P = .07). Total water content was higher in the kidneys (P < .05) and tended to be higher in the lungs (P = .05), liver (P = .07), and brain (P = .07) of the HF group than in those of the LF group. The between-group differences in net fluid balance and fluid extravasation rate were present during the first 30 minutes of normothermic cardiopulmonary bypass. Thereafter, the values stabilized and remained similar in the two groups. Plasma volume and systemic vascular resistance differed between the groups.

CONCLUSION

Cardiopulmonary bypass flow rate of 110 mL x kg(-1) x min(-1) was associated with higher positive net fluid balance and fluid extravasation rate than 80 mL x kg(-1) x min(-1). The effect was mainly observed in the initial phase of cardiopulmonary bypass.