Determination of circulating blood volume by measurement of indocyanine green dye in hemolysate: a preliminary study

Reliability of indocyanine green retention and clearance rates at 15 minutes calculated by dye-dilution cardiac output flowmetry in comparison to blood sampling in patients undergoing hepatic resection

BACKGROUND

The indocyanine green retention rate at 15 min (ICGR15) is a marker of the liver function and is useful for planning hepatectomy. To clarify the ICGR15 and the related clearance value (ICGK) calculated by a dye-dilution cardiac output flowmetry (DCOF), we examined the correlation and clinical significance of the ICGR15 values determined by DCOF and those determined with the conventional blood sampling (BS) procedure.

METHODS

We extracted liver function parameters, including the ICGR15 modified value and ICGK, and the extent of hepatectomy from the clinical and surgical records of 63 patients with various liver diseases in whom the ICGR15 (actual value), R15m (mean), and K (clearance rate per minute) were measured by DCOF.

RESULTS

All the patients were classified as Child-Pugh grade A. Hepatic complications were observed in 10 (16%) patients, but there was no mortality. The mean values of ICGR15 determined by BS (R15-BS) and DCOF (R15-DCOF) were 12.2 ± 8.1% and 11.2 ± 8.7%, respectively. The mean R15m determined by DCOF (R15m-DCOF) was 15.7 ± 10.2%. Significant differences were observed between R15-BS and R15-DCOF (1.1 ± 4.8%; p = 0.002) and R15m-DCOF (4.0 ± 5.9%; p < 0.001). The difference between R15-BS and R15m-DCOF was greater than that between R15-BS and R15-DCOF. Correlation between R15-BS and R15-DCOF was significant r = 0.839 (p < 0.001).

CONCLUSIONS

The ICGR15 measured by DCOF shows comparable reliability and stability to the BS method, which is useful for planning hepatectomy.

Blood volume measurements using an integrated fiberoptic monitoring system in a porcine septic shock model

OBJECTIVES

To compare the accuracy of an integrated fiberoptic monitoring system using transpulmonary thermo-dye dilution technique to measure blood volume (BV) with standard method using chromium-51-tagged erythrocytes in septic shock.

DESIGN

Prospective blinded animal laboratory study.

SETTING

University department of anesthesiology.

SUBJECTS

Thirty-five anesthetized and mechanically ventilated pigs (21.4 +/- 2.2 kg) were investigated over a period of 6 hrs.

INTERVENTIONS

Septic shock was induced with fecal peritonitis (0.75 g . kg per body weight autologous feces). A central venous catheter was used for injection of the indicator dyes.

MEASUREMENTS AND MAIN RESULTS

BV was measured by detecting indocyanine green using a 4-Fr aortic catheter with an integrated fiberoptic and thermistor connected to a computer system for calculation of transpulmonary indicator dilution BV (BVTPID). Cr-tagged erythrocytes were used as standard method of BV measurement (BV-Cr). Hemodynamic treatment scheme was aimed at maintenance of a central venous pressure of 12 mm Hg. Data were analyzed using Bland-Altman analyses. One hundred and five data pairs of simultaneous BV measurements were yielded during hemodynamic stability with a mean BVTPID of 64.2 +/- 17.8 mL . kg. Mean BV-Cr was 83.1 +/- 17.0 mL . kg. Linear regression equation was BVTPID = 0.58 x BV-Cr + 15.8 (r = .56, p < .01). Mean bias was 18.9 mL . kg (95% confidence interval, 15.7-22.1 mL . kg), with limits of agreement of -13.9 to 51.7 mL . kg.

CONCLUSIONS

Transpulmonary indicator dilution for blood volume measurement agrees moderately with standard method using Cr-tagged erythrocytes in porcine septic shock.

Serial determinations of absolute plasma volume with indocyanine green during hemodialysis

Hemodynamic stability during hemodialysis depends largely on plasma volume (PV) preservation during ultrafiltration (UF). Current estimates of blood volume (BV) are indirect or involve the use of radioactive tracers, which does not allow repeated measurements during hemodialysis. Indocyanine green was used to measure PV during hemodialysis. After an initial pilot phase (phase I), PV values were determined before dialysis, repeatedly during isovolemic hemodialysis (phase II), and during stepwise UF (phase III). Absolute BV values were calculated from PV and hematocrit values. Patients were monitored for extracellular fluid volume (bioimpedance monitoring) and relative BV changes (ultrasonic monitoring). Phase I demonstrated dye stability in plasma, peak absorbance at 805 nm, and a short half-life (4.53 +/- 1.5 min). Ten milligrams of dye (2.5 mg/ml) were injected for each PV measurement. Eight plasma samples were obtained beginning 3 min after injection, at 1-min intervals, for assessment of decay characteristics. The isovolemic hemodialysis PV measurements demonstrated excellent reproducibility (r(2) = 0.98; method SD, 356 ml; mean coefficient of variation, 4.07%) and a difference of only 149 +/- 341 ml (mean +/- SD), compared with predialysis PV values (Bland-Altman method). PV values at the beginning of dialysis were significantly correlated with body surface area (r(2) = 0.82, P < 0.001) and extracellular fluid estimates (r(2) = 0.73, P < 0.001). BV prediction formulae significantly underestimated absolute BV at the start of dialysis (P < 0.0001). The findings demonstrate that this method can be used for repeated PV determinations during hemodialysis, with excellent reproducibility. It is a potential tool for further research on hemodynamic stability during UF.

Evaluation of changes in circulating blood volume during acute and very acute stages of subarachnoid hemorrhage: implications for the management of hypovolemia

OBJECT

Circulating blood volume (cBV) is reported to decrease in patients who suffer a subarachnoid hemorrhage (SAH), but little is known about the correlation between changes in cBV, and patient clinical condition and time course after SAH, especially during the very acute stage. To determine appropriate management of patients with SAH, the authors measured cBV by using pulse spectrophotometry immediately after patient admission. They also evaluated whether the timing of surgery influenced changes in cBV.

METHODS

Circulating blood volume was measured in a total of 73 patients who were divided into the following three groups: Group A (very acute SAH) consisted of 14 SAH cases, Group B (acute SAH) included 34 SAH cases, and Group C (controls) included 25 other neurosurgical cases. All patients in Group A underwent aneurysm clipping within 6 hours after onset of SAH, whereas all patients in Group B underwent aneurysm clipping within 72 hours after onset. Hypervolemic therapy was not performed in patients with SAH. Before surgery, cBV was significantly lower in patients in Group B than in those in Group C, but there was no significant difference in this parameter when comparing Groups A and C. Although there was a transient drop in cBV in Group B patients for at least 3 days after surgery, there was no significant change in cBV in Group A patients during the study period. None of the Group A patients suffered from symptomatic vasospasm; however, four Group B patients did experience symptomatic vasospasm.

CONCLUSIONS

The authors assert that normovolemic fluid management is appropriate for patients who undergo surgery during the very acute stage of SAH, whereas a relatively hypervolemic therapy is necessary for 3 to 5 days after operation to prevent early hypovolemia in patients who undergo surgery during the acute stage of SAH.

Errors of the backextrapolation method in determination of the blood volume

Backextrapolation is an empirical method to calculate the central volume of distribution (for example the blood volume). It is based on the compartment model, which says that after an injection the substance is distributed instantaneously in the central volume with no time delay. The occurrence of recirculation is not taken into account. The change of concentration with time of indocyanine green (ICG) was observed in an in vitro model, in which the volume was recirculating in 60 s and the clearance of the ICG could be varied. It was found that the higher the elimination of ICG, the higher was the error of the backextrapolation method. The theoretical consideration of Schröder et al (Biomed. Tech. 42 (1997) 7-11) was proved. If the injected substance is eliminated somewhere in the body (i.e. not by radioactive decay), the backextrapolation method produces large errors.

Extra protein loss not caused by surgical bleeding in patients with ovarian cancer

BACKGROUND

[corrected] Clinical experience in patients with ovarian cancer has shown special difficulties in maintaining cardiovascular stability during surgery.

METHODS

To evaluate the causes for this observation, 15 patients with benign ovarian tumours (group I) and 13 patients with ovarian cancer (group II) were investigated perioperatively. Plasma volume (indocyanine green-dilution technique), haematocrit, plasma protein concentration, mean arterial pressure, heart rate, and central venous pressure were measured immediately before and after cytoreductive surgery.

RESULTS

Normal values of blood-, plasma-, and red cell volume were determined preoperatively in both groups, and in relation to body surface area there were no intergroup differences of these parameters. In group I, the significant decrease in red cell volume of 313 ml postoperatively was compensated for by an increase in plasma volume of 371 ml (median values). In contrast to group I, the decrease in red cell volume of 328 ml in group II was not related to a significant increase in plasma volume, so that blood volume postoperatively was 483 ml lower than preoperatively, although the same standardized infusion regimen as in group I was applied. Patients of group II had a significantly higher loss of intravascular protein (49 g vs 13 g in group I), which left the intravascular space by another way than by surgical bleeding. This extra protein loss is termed Intraoperative Protein Shift (IPS).

CONCLUSION

IPS could be an important quantity in perioperative fluid balance. We assume that different surgical procedures predispose to occurrence of differing amounts of IPS.

Accuracy and reproducibility of the measurement of actively circulating blood volume with an integrated fiberoptic monitoring system

OBJECTIVE

Bedside monitoring of circulating blood volume has become possible with the introduction of an integrated fiberoptic monitoring system that calculates blood volume from the changes in blood concentration of indocyanine green dye 4 mins after injection. The aim of this investigation was to compare the blood volume estimate of the integrated fiberoptic monitoring system (group 1) with the standard methods of blood volume measurement using Evans blue (group 2), and indocyanine green measured photometrically (group 3).

DESIGN

Prospective laboratory study.

SETTING

Animal laboratory of a University's institute for experimental surgery.

SUBJECTS

Eleven anesthetized, paralyzed, and mechanically ventilated piglets.

INTERVENTIONS

A central venous catheter was used for the injection of the indicator dyes (Evans blue and indocyanine green). A fiberoptic thermistor catheter was advanced into the thoracic aorta. The fiberoptic catheter detects indocyanine green by reflection densitometry for the estimation of blood volume of the integrated fiberoptic monitoring system. Samples for the determination of Evans blue and indocyanine green concentrations were drawn from an arterial catheter in the femoral artery over a period of 17 mins after injection.

MEASUREMENTS AND MAIN RESULTS

Measurements were performed during normovolemia, hypovolemia (blood withdrawal of < or = 30 mL/kg), and hypervolemia (retransfusion of the withdrawn blood plus an infusion of 10% hydroxyethyl starch [45 mL/kg]). Linear regression, correlation, and bias were calculated for the comparison of the blood volume estimates by the fiberoptic monitoring system (group 1) vs. the total blood volume estimates using Evans blue (group 2) and indocyanine green (group 3): group 1 = 0.82.group 2-26 mL; r2 = 82.71%; r = .91; n = 40; group 1-group 2 +/- 1 SD = -435 +/- 368 mL; group 1 = 0.79.group 3 + 50 mL; r2 = 74.81%; r = .87; n = 28; group 1-group 3 +/- 1 SD = -506 +/- 374 mL.

CONCLUSIONS

The results demonstrate that the blood volume estimate of the fiberoptic monitoring system (group 1) correlates closely with the total blood volume measurement using Evans blue (group 2) and indocyanine green (group 3). Trapped indicator in the packed red cell column after centrifugation of the blood samples may account for an overestimation of group 2 and group 3 of approximately 10% to 14%, but there still remains a proportional difference of 10% between group 1 vs. group 2 and vs. group 3. This difference is due to the longer mixing times of group 3 (16 mins) and group 2 (17 mins), during which they are distributed in slowly exchanging blood pools. It seems that the blood volume estimate of the fiberoptic monitoring system (group 1) represents the actively circulating blood volume and may be useful for bedside monitoring.

Plasma volume estimation using indocyanine green. A single intravenous injection method

The validity and reliability of plasma volume estimation using indocyanine green were investigated in five in vitro experiments and in three in vivo series. The in vitro measurements reflected real volumes with an error of about 1%. Comparative measurements in the same patients using indocyanine green or Cr51 labelled red cells differed by 1.7% (r = 0.97). The mean (SD) plasma volume difference between two successive plasma volume measurements using indocyanine green was 38 (43) ml (r = 0.99). Plasma volume measured before and about 7 min after a hyperosmolar saline bolus (100 ml, 1 molar) was increased by 223 (102) ml and 286 (49) ml when determined by indocyanine green and plasma protein changes respectively. Nevertheless, the necessity for central venous injection and arterial sampling restricts the possible application of the method to intra-operative or emergency care use.

Determination of plasma volume with indocyanine green in man

We investigated the feasibility of using indocyanine green (ICG) for plasma volume (PV) determination in man. Duplicate PV measurements were carried out in 23 healthy subjects to test repeatability. ICG (0.25 mg/kg) was injected intravenously into one arm and venous blood was withdrawn from the opposite arm. Optical density of plasma samples from minute 3 to 9 was measured in a densitometer. ICG concentration at injection time was determined by monoexponential extrapolation. The mean (SD) difference (MD) was -23 ml (183) or -0.6% (5.7%). Linear regression revealed PV2 = 0.92.PV1 + 226 (r = 0.92). The PV values corresponded well with data from other studies. In 26 surgical patients PV was determined using two methods: 1) the same as in healthy subjects and 2) using a modification of this method in whole blood (PVB). For PVB measurement blood was drawn through a cuvette-densitometer from an arterial line. Calculations were the same as in PV determination except for the use of hematocrit to achieve plasma concentrations of ICG from whole blood. In patients MD were -53 ml (144) or -1.3% (4.3) for PV and -19 ml (161) or -0.3% (5.1) for PVB. Comparing PVB and PV revealed MD = -113 ml (149) or -3.3% (4.2). The whole blood method is easier to perform and reduces blood waste to almost zero. In conclusion, ICG is a suitable tracer for PV determination.

The use of radioisotopes in haematology

Radioisotopes used in haematology may be divided into four groups: 1. those used for in vivo studies, involving the labelling of cells in the blood or bone marrow and the use of labelled plasma albumin; 2. investigations involving surface counting over organs such as the bone marrow, spleen, liver and heart; 3. in vitro use of radioisotopes in the haematology laboratory and 4. isotopes used as part of imaging procedures. The shorter the half life of the isotope, the more limited patient exposure to radioactivity will be, but the greater the problems of starting and completing the investigation before the isotope has decayed. Isotopes studies should not be carried out in children or pregnancy unless there are exceptional clinical indications.

Measurement of plasma volume in neonates

There is no reliable and safe method for measuring plasma volume in ill newborn infants. We describe an adaptation of the dye dilution technique using indocyanine green as the plasma label, which can be used in the sickest and smallest of infants with the minimum of disturbance. To avoid the need to take large volumes of blood from the infant, samples were diluted 1:1 with distilled water and pooled adult sera was used to construct the dye dilution standard curves. Eighteen preterm and fullterm infants were studied on 30 occasions. The measured plasma volume ranged between 21.4 and 106 ml/kg. Paired measurements were performed within 30-90 minutes of each other in seven infants. In five infants estimations of plasma volume were made shortly before and 30 minutes after the infusion of a known quantity of plasma. In eight out of 12 infants who had two measurements made there was close agreement between the second measured volume and the first measured volume, taking into account how much plasma had been given to or taken from the infant between the two measurements. The error ranged from 0.2 to 5.2 ml and the plasma recovery error ranged from -2.9% to +4.7%. In the remaining four infants the errors ranged from 2.1 to 9.5 ml and -14.2% to +8.8%. Errors in the measurement of plasma volume may arise as the result of sampling too early before full mixing of the dye has occurred, and there is a potential error in the measurement due to the distribution of albumin in the extracellular space in sick infants resulting in an overestimation of the plasma volume. Proposals for reducing sources of errors are discussed.

Plasma volumes, blood volumes, and plasma protein concentrations after moderate haemodilution with fluosol-DA or normal saline in the rat

Plasma volumes, blood volumes, and plasma total protein, albumin, and bilirubin concentrations have been determined in rats for 72 h following 20 or 40 mL kg-1 haemodilution with Fluosol-DA or 0.9% NaCl. Haemodilution with 20 mL kg-1 of either haemodiluent had no influence on the measured values. Plasma and blood volumes did not change after Fluosol-DA haemodilution at 40 mL kg-1, but albumin and bilirubin concentrations were decreased for 72 h. Only bilirubin concentrations were decreased for 72 h following haemodilution with 40 mL kg-1 of 0.9% NaCl. It was concluded that changes in a drug's plasma protein binding, and not the plasma or blood volume, are responsible for the reported alterations in a drug's apparent volume of distribution after haemodilution.