Transcapillary fluid balance in subcutaneous tissue of patients undergoing aortocoronary bypass with extracorporeal circulation

Fluid accumulation in the staged Fontan procedure: the impact of colloid osmotic pressures

OBJECTIVES

Despite Fontan surgery showing improved results, fluid accumulation and oedema formation with pleural effusion are major challenges. Transcapillary fluid balance is dependent on hydrostatic and colloid osmotic pressure (COP) gradients; however, the COP values are not known for Fontan patients. The aim of this study was to evaluate the COP of plasma (COPp) and interstitial fluid (COPi) in children undergoing bidirectional cavopulmonary connection and total cavopulmonary connection.

METHODS

This study was designed as a prospective, observational study. Thirty-nine children (age 3 months-4.9 years) undergoing either bidirectional cavopulmonary connection or total cavopulmonary connection procedures were included. Blood samples and interstitial fluid were obtained prior to, during and after the preoperative cardiac catheterization and surgery with the use of cardiopulmonary bypass (CPB). Interstitial fluid was harvested using the wick method when the patient was under general anaesthesia. Plasma and interstitial fluid were measured by a colloid osmometer. Baseline values were compared with data from healthy controls.

RESULTS

Baseline COPp was 20.6 ± 2.8 and 22.0 ± 3.2 mmHg and COPi was 11.3 ± 2.6 and 12.5 ± 3.5 mmHg in the bidirectional cavopulmonary connection group and the total cavopulmonary connection group, respectively. These values were significantly lower than in healthy controls. The COPp was slightly reduced throughout both procedures and normalized after surgery. The COPi increased slightly during the use of CPB and significantly decreased after surgery, resulting in an increased COP gradient and was correlated to pleural effusion.

CONCLUSIONS

Fluid accumulation seen after Fontan surgery is associated with changes in COPs, determinants for fluid filtration and lymphatic flow.

CLINICALTRIALS.GOV IDENTIFIER

NCT 02306057: https://clinicaltrials.gov/ct2/results?cond=&term=NCT+02306057.

Fluid accumulation after closure of atrial septal defects: the role of colloid osmotic pressure

OBJECTIVES

Following paediatric cardiac surgery with cardiopulmonary bypass (CPB), there is a tendency for fluid accumulation. The colloid osmotic pressure of plasma (COPp) and interstitial fluid (COPi) are determinants of transcapillary fluid exchange but only COPp has been measured in sick children. The aim of this study was to assess the net colloid osmotic pressure gradient in children undergoing atrial septal defect closure.

METHODS

Twenty-three patients had interventional and 18 had surgical atrial septal defect closures. Interstitial fluid was harvested using a wick method before and after surgery with CPB with concomitant blood samples. COP was measured using a colloid osmometer for small fluid samples. Baseline COP was compared with data from healthy children.

RESULTS

COPp at baseline was 21.9 ± 2.8 and 21.4 ± 2.2 mmHg in the interventional and surgical groups, respectively, and was significantly lower than in healthy children (25.5 ± 3.1 mmHg) (P < 0.001). In the surgical group, the use of CPB significantly reduced COPp to 16.9 ± 2.9 mmHg (P < 0.001) and the colloid osmotic gradient [ΔCOP (COPp - COPi)] to 2.9 ± 3.8 mmHg (P < 0.001) compared with interventional procedure. One hour after the procedure, COPi was 15.6 ± 3.8 mmHg and 9.9 ± 2.1 mmHg (P < 0.001) and the ΔCOP was 5.4 ± 3.0 mmHg and 9.1 ± 3.1 mmHg (P < 0.003) in the interventional and surgical groups, respectively.

CONCLUSIONS

Baseline COPp and COPi were lower in atrial septal defect patients compared with healthy children. The significantly lower COP gradient during CPB may explain the tendency for more fluid accumulation with pericardial effusion in the surgical group. The increased COP gradient after CPB may represent an oedema-preventive mechanism.

Bedside determination of fluid accumulation after cardiac surgery using segmental bioelectrical impedance

OBJECTIVES

Bioelectrical impedance analysis (BIA) is based on the physical property of tissues to conduct electrical currents, impedance being inversely related to tissue fluid content. At high frequency, the electrical current flows across both intracellular and extracellular pathways, making the assessment of fat-free mass possible while a low-frequency current flows through the extracellular space. Similarly, segmental BIA may be used to assess segmental body fluid repartition. The aim of this study was to assess fluid accumulation after cardiac surgery by multiple frequency segmental BIA.

DESIGN

Observational, clinical study.

SETTING

A 17-bed, surgical intensive care unit in a university hospital.

PATIENTS

Twenty-six patients before and after open-heart surgery with cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

After surgery, fluid accumulation resulted in a decrease in whole-body and segmental bioelectrical impedance in the arm and in the trunk. There was a good correlation between the fluid accumulation measured by fluid balance and by whole-body or segmental impedance changes. The major part (71%) of fluid accumulation occurred in the trunk. Multiple frequency measurements did not indicate a fluid shift between the intra- and extracellular compartments.

CONCLUSION

Cardiac surgery produced a significant decrease in segmental trunk BIA, reflecting fluid accumulation at the trunk level.

Estimation of total body fluid shifts between plasma and interstitium in man during extracorporeal circulation

Fluid transport between plasma and interstitium during extracorporeal circulation was studied in seven patients undergoing aortocoronary bypass grafting. The absolute shifts in plasma volume during hypothermia were determined as the difference between input and loss of fluid and the changes in blood volume. The change in haemoglobin concentration due to acute haemodilution when starting extracorporeal circulation was used to calculate the absolute blood and plasma volume. The Starling equation for exchange across the capillary wall was used to describe fluid shifts. The total fluid filtered during the 60- to 90-min period of extracorporeal circulation averaged 34.1 +/- 11.1 (s.d.) ml/min. The total body filtration coefficient from the Starling relationship averaged 0.046 +/- 0.012 ml/kg.mmHg.min (0.354 +/- 0.092 ml/kg.kPa.min). Haemodilution, reducing colloid osmotic pressure in plasma (COPP) by approximately 10 mmHg (1.3 kPa) will result in a loss of plasma fluid of around 2 1 per hour. When corrected for lower fluid viscosity due to hypothermia during extracorporeal circulation, CFC would be about 40% higher, and a filtered volume of nearly 3 1 in a normothermic 70-kg person would be expected. Crystalloid haemodilution for shorter periods of time does not produce excessive oedema and thus may be well tolerated.

Sepsis after coronary bypass grafting: evidence for loss of the gut mucosal barrier

Postoperative infections may originate from a patient's gastrointestinal tract. We studied infections after coronary artery revascularization. Three hundred twenty-nine patients underwent coronary artery revascularization from January 1987 to March 1990. Eight of the 329 (2.4%) died; none of the deaths were infection related. Fifty-five culture-proven infections were identified in 22 of 321 survivors (6.8%); 9 infections (16%) were gram-positive, 5 (9%) were fungal, and 41 (75%) were gram-negative. Site of infections were respiratory tract, 58%; urinary tract, 18%; blood, 13%; and mediastinum, 11%. Ninety-six percent of respiratory tract and all urinary tract infections were gram-negative or fungal. There was no significant difference between infected and noninfected groups in sex, age, smoking history, preoperative hematocrit or leukocyte count, serum albumin level, or time on extracorporeal bypass. The infected group required intubation and nasogastric suction for a significantly longer time than the noninfected group (p less than 0.001). Time to enteral alimentation was significantly longer in the infected group (p less than 0.02). We were unable to correlate the number of infections with the lengths of intubation, nasogastric suction, or time to enteral alimentation. This study supports the concept of postoperative infections arising from bacterial translocation across the patient's gastrointestinal tract. The most significant risk factor is the length of the gastrointestinal tract disuse.

Thermal skin injury: effect of fluid therapy on the transcapillary colloid osmotic gradient

The effects of fluid therapy on interstitial colloid osmotic and hydrostatic pressures in thermally injured skin were investigated in anesthetized rats subjected to full-thickness scald burns to 40% of the body surface area and resuscitation for 3 hr by either lactated Ringer's or plasma. Interstitial fluid hydrostatic pressure (Pif) was reduced from -2 mm Hg to -20 to -40 mm Hg after injury, which will profoundly increase transcapillary filtration. Following the onset of fluid therapy, Pif increased to slightly positive values. In control, colloid osmotic pressure in plasma (COPp) was 20.6 +/- 0.4 mm Hg and in interstitial fluid (COPif) 13.7 +/- 0.3 mm Hg (means +/- SEM). The transcapillary oncotic pressure gradient (COPgrad = COPp-COPif) was 6.9 +/- 0.4 mm Hg. Following nonresuscitated thermal injury, COPp declined to 18-19 mm Hg (P less than 0.05) and COPif was reduced to 10.4 +/- 0.5 mm Hg (P less than 0.05). Fluid therapy by lactated Ringer's markedly reduced COPp (12.3 +/- 0.3 mm Hg; P less than 0.05), and COPgrad was almost abolished (2.6 +/- 0.7 mm Hg; P less than 0.05). In contrast, plasma infusion maintained COPp, whereas COPgrad increased significantly (11.1 +/- 1.2 mm Hg; P less than 0.05). Noncolloid saline solutions have been preferred for the initial fluid therapy for burns. The present study provides evidence that this will reduce both COPp and COPgrad, a situation in which edema formation will be favored.

Time-related changes in the Starling forces following extracorporeal circulation

The intra- and postoperative variations of the transcapillary forces [colloid osmotic pressure of plasma (COPpl), colloid osmotic pressure of interstitial fluid (COPif), average hydrostatic pressure in the interstitium (Pif)] were studied in the subcutaneous tissue as a function of time in 13 patients operated on for coronary artery disease using extra-corporeal circulation (ECC). The measurements were performed before operation, during ECC, and during the first 24 hours postoperatively. COPif was measured subcutaneously on the chest both by the wick method and by a noninvasive blister suction method. The latter technique allowed several consecutive measurements in the same individual during the postoperative period. Pif was measured by "wick-in-needle" technique in the same area as the COPif measurements. COPpl was measured in a blood sample collected from a cubital vein. COPpl was reduced about 50% during ECC returned to pre-ECC level within the first 6 hours postoperatively. During ECC COPif was higher than COPpl, reaching its minimum level 4 to 5 hours postoperatively. Measurements performed following ECC showed return of the transcapillary COP-gradient to the normal direction (COPpl greater than COPif). Pre-ECC level of COPif was not entirely obtained during the first postoperative day. Pif increased gradually during ECC and continued to increase the first 2 to 3 hours following ECC. Pre-ECC level was reached within 24 hours postoperatively. The present investigation has demonstrated major dynamic variations in the transcapillary forces in patients undergoing open heart surgery with ECC. There was an increased net capillary filtration (F) intraoperatively predisposing to interstitial edema formation in subcutaneous tissue until several hours following the termination of ECC.