Continuous venous oximetry for hemodynamic and oxygen transport stability post cardiac surgery.

Under the diagnostic-related group (DRG) reimbursement system, hospitals are looking to decrease costs related to unnecessary laboratory measurements. To assess the efficacy of continuous SvO2 as the only means to monitor the balance of the oxygen transport of the stable postoperative cardiac patient in the ICU, we studied 26 adult patients undergoing cardiac surgery with an uneventful postoperative course. All subjects had an Opticath fiberoptic PA catheter inserted for 29.6. +/- 11.0 hours (range 16-66) and spent an average of 42.4 +/- 17.5 hours in the Intensive Care Unit (range 20-87). Cardiac output, and Hemoglobin/Hematocrit were determined serially every 2 hours during the first 6 postoperative hours and 4 hours respectively according to our ICU practice. Arterial blood gases were determined freely in relation to changes in the hemodynamic and respiratory status. No clinical decisions were undertaken on the basis of SvO2. Retrospectively it was determined whether basing decisions on the SvO2 would have reduced the number of unnecessary cardiac outputs, ABGs and Hgb/Hcts. Using the SvO2 as potential indicator of hemodynamic and oxygen transport stability it could significantly reduce the number of determinations per patient, ie, cardiac output (11.7 +/- 4.2 vs 2.1 +/- 0.3, p less than 0.05), ABGs (11.3 +/- 2.8 vs 2.8 +/- 0.4, p less than 0.05) and Hgb/Hcts (5.7 +/- 1.3 vs 2.0 +/- 0.0, p less than 0.05). The use of SvO2 would save the hospital $84.5 +/- 27.5 (range 31.5 +/- 140.9) per stable patient in the ICU and a total of 220.4 +/- 69.9 minutes (range 90-300) of ICU nursing time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mixed venous oxygen saturation as a predictor of cardiac output in the postoperative cardiac surgical patient

Mixed venous oxygen saturation (SvO2) was measured continuously with a fiberoptic pulmonary artery catheter in 25 patients during the first 24 hours after cardiac surgery and was compared with the thermodilution cardiac index (CI). The mean correlation coefficient between SvO2 and CI was 0.05 +/- 0.42, and was not significantly different from zero. Although the mean correlation coefficient between the change in SvO2 and the change in CI was significant (p less than .05), the magnitude of the coefficient (0.19 +/- 0.44) indicates poor predictive value. The correlation did not improve when adjusted for multiple clinical variables, and the SvO2 was not predictive of a CI less than 2 L/min/m2, a level of cardiac performance that might require intervention. In conclusion, SvO2 was not predictive of CI postoperatively in the cardiac surgical patient.     

Factors influencing mixed venous oxygen saturation in intensive care

Changes in mixed venous blood oxygen saturation (SvO2) were studied in 2 groups of patients. Group I patients (n = 10) were all hypoxaemic, suffering from acute respiratory failure, requiring that FIO2 be maintained at 1 throughout the study; respiratory and haemodynamic conditions were improved using PEEP and cardiovascular support. On the other hand, Group II patients (n = 13) were non-hypoxaemic patients with circulatory shock in whom FIO2 was gradually increased, and the haemodynamic status was improved using positive inotropic drugs (dopamine, dobutamine, adrenaline, amrinone). All 23 patients had a Swan-Ganz catheter set up for monitoring; all the usual haemodynamic and respiratory parameters were measured. Haematocrit values were kept at the same level throughout the study. Haemodynamic parameters were measured each time a new therapeutic procedure was carried out. No close relationship between SvO2 changes and changes in cardiac index or O2 consumption were found. However, a close relationship existed between changes in SvO2 and changes in O2 extraction (EAO2): SvO2 = -EAO2 + 102 (Group I; r = 0.90, n = 54); SvO2 = -1.2 EAO2 + 103 (Group II; r = 0.93, n = 66). A strong relationship was also found between changes in SvO2 and in FIO2 in each patient of Group II. In the complicated physiological set-up of an intensive care patient, SvO2 reflects oxygen extraction. A fall in SvO2 is related to an altered oxygen demand: oxygen supply ratio. In the most seriously ill patients, there is no relationship between changes in SvO2 and cardiac index.     

Determination of anaerobic threshold and influence of hemodynamics on exercise intolerance in patients after cardiac valve surgery]

In order to evaluate the exercise tolerance of the patients after cardiac valve surgery, the exercise stress test by supine bicycle ergometer was performed in 26 patients. An anaerobic threshold (AT) was determined by lactate threshold. The mixed venous oxygen saturation (SvO2) was measured simultaneously to assess the relationship between AT and SvO2 during exercise test. The study group consisted of 10 men (mean age: 46.2 years) and 16 women (mean age: 49.4 years). Each patient received either of following two programs: 1) a single step test of approximately 5 METS, which corresponded to the exercise tolerance level of NYHA functional Class II (Group A, 18 patients); and 2) a consecutive multi-staged test, which was begun at a worked of 25 W and increased by 25 W in every 3 minutes until the symptomatic maximum or ended at 100 W (Group B, 8 patients). Eleven patients (6 patients in Group A, 5 patients in Group B) had reached AT point during the test. SvO2 was 26.6 +/- 3.6% in group A patients, and 29.3 +/- 1.4% in group B patients at the point of AT. This data suggests that anaerobic metabolism begins at the level of SvO2 slightly less than 30%, and that SvO2 is a simple and usefull indicator for the estimation of AT. In patients with reduced exercise tolerance which was recognized by AT point at exercise stage of about 5 METS, the right atrial and pulmonary arterial mean pressure were higher than the others (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Monitorage de la Sv̄2 en chirurgie aortique: intérêt et limites

This study aimed to determine perioperative changes in mixed venous oxygen saturation (SvO2) in patients undergoing aortic surgery. Continuous SvO2 monitoring was carried out using an Oximetrix pulmonary catheter. Fourteen patients were randomly assigned to 2 groups, group I (n = 7) patients being given a thoracic epidural anaesthetic with a supplementary general anaesthetic, and group II (n = 7) a general anaesthetic as usual. In both groups, SvO2 increased at induction. In group I patients, SvO2 decreased during surgery to less than 60% (n = 2) and less than 70% (n = 4). This fall was corrected by volume loading and intravenous ephedrine. The intraoperative decrease in SvO2 occuring in 2 group II patients was due to a fall in haematocrit in one, and a propranolol infusion in the other. Although patients in group I were all extubated early after the end of surgery (85 +/- 35 min), the lowest value of SvO2 after extubation was always greater than 60%. Patients undergoing aortic surgery under thoracic epidural anaesthesia can be extubated early, without markedly depressing peripheral reserves in oxygen extraction.     

Detection of venous air embolism by continuous mixed venous oximetry in dogs

Continuous mixed venous oxygen saturation (SvO 2) was evaluated as a monitor of venous air embolism in a canine model. Nineteen dogs were anesthetized, paralyzed, and mechanically ventilated. Invasive monitoring included SvO 2, systemic and pulmonary artery blood pressures, and thermodilution cardiac outputs. Air boluses of 0.25 and 0.5 ml/kg were injected in six dogs and 1 ml/kg in all. All 1 ml/kg emboli were detected by greater than or equal to 5% decreases in the SvO 2. The SvO 2 decreased from 82 +/- 8% to 72 +/- 11% (mean +/- SD), an average decrease of 9 +/- 5% (p = 0.004). Time to the SvO 2 nadir was 2.6 +/- 2.5 min. Of the 0.5 and 0.25 ml/kg emboli, 50% and 17% were detected, respectively. Cardiac output decreased from 2.9 +/- 0.8 to 2.1 +/- 0.8 L/min after the 1 ml/kg emboli (p = 0.02). The 1 ml/kg emboli increased pulmonary artery pressures and decreased systemic blood pressure in 100% and 75% of animals, respectively. Peak changes in pulmonary artery pressure occurred at 1.2 +/- 0.8 min. In the present study, time to maximum change was greater for SvO 2 than for pulmonary artery pressure changes. Use of fiberoptic pulmonary artery catheters for continuous measurement of SvO 2 can add a new diagnostic modality to venous air embolism detection in patients who require a pulmonary artery catheter for other medical indications.     

A noninvasive estimation of mixed venous oxygen saturation using near-infrared spectroscopy by cerebral oximetry in pediatric cardiac surgery patients

BACKGROUND: Near-infrared spectroscopy (NIRS) is a noninvasive optical monitor of regional cerebral oxygen saturation (rSO2). The aim of this study was to validate the use of NIRS by cerebral oximetry in estimating invasively measured mixed venous oxygen saturation (SvO2) in pediatric postoperative cardiac surgery patients. METHODS: Twenty patients were enrolled following cardiac surgery with intraoperative placement of a pulmonary artery (PA) or superior vena cava (SVC) catheter. Five patients underwent complete biventricular repair--complete atrioventricular canal (n=3) and other (n=2). Fifteen patients with functional single ventricle underwent palliative procedures--bidirectional Glenn (n=11) and Fontan (n=4). Cerebral rSO2 was monitored via NIRS (INVOS 5100) during cardiac surgery and 6 h postoperatively. SvO2 was measured from blood samples obtained via an indwelling PA or SVC catheter and simultaneously correlated with rSO2 by NIRS at five time periods: in the operating room after weaning from cardiopulmonary bypass, after sternal closure, and in the CICU at 2, 4, and 6 h after admission. RESULTS: Each patient had five measurements (total=100 comparisons). SvO2 obtained via an indwelling PA or SVC catheter for all patients correlated with rSO2 obtained via NIRS: Pearson's correlation coefficient of 0.67 (P<0.0001) and linear regression of r2=0.45 (P<0.0001). Separate linear regression of the complete biventricular repairs demonstrated an r=0.71, r2=0.50 (P<0.0001). Bland-Altman analysis showed a bias of +3.3% with a precision of 16.6% for rSO2 as a predictor of SvO2 for all patients. Cerebral rSO2 was a more accurate predictor of SvO2 in the biventricular repair patients (bias -0.3, precision 11.8%), compared with the bidirectional Glenn and Fontan patients. CONCLUSIONS: Regional cerebral oximetry via NIRS correlates with SvO2 obtained via invasive monitoring. However, the wide limits of agreement suggest that it may not be possible to predict absolute values of SvO2 for any given patient based solely on the noninvasive measurement of rSO2. Near-infrared spectroscopy, using the INVOS 5100 cerebral oximeter, could potentially be used to indicate trends in SVO2, but more studies needs to be performed under varying clinical conditions.     

Continuous monitoring of mixed venous oxygen saturation in anesthesia in pulmonary surgery

The multiplicity of potential causes of variations in mixed venous oxygen saturation (SvO2) during one lung ventilation (OLV), including a constant ventilation/perfusion mismatch, explains that it has been suggested as a routine monitoring procedure. To assess its usefulness, 12 adults undergoing OLV were monitored during surgery with an Oximetrix pulmonary catheter, placed on the side opposite to the surgical field under fluoroscopic control. Seventy two complete sets of haemodynamic measurements were obtained at 6 different times during surgery. We studied the ability of changes in SvO2 to predict changes in arterial oxygen saturation (SaO2), cardiac output (CO), and venous admixture (VA) by calculating sensitivities (Se), specificities (Sp) and predictive values with regard to these variables. There were no complications due to the protocol. However left-sided catheter placement failed in four cases. Correlation between optical and measured SvO2 was very strong (r = 0.94; p less than 0.001). SvO2, oxygen consumption (VO2) and the rate of oxygen extraction remained constant throughout the procedure, even when CO, mean arterial pressure, VA, SaO2 and PaO2 varied. Clamping the pulmonary artery returned VA, SaO2 and PaO2 values to those found before OLV, but produced a significant decrease in CO. SvO2 had low Se and Sp for changes in other variables (CO: 76 +/- 7, 48 +/- 9; PaO2: 79 +/- 6, 59 +/- 9; VA: 54 +/- 7, 48 +/- 7 respectively). In this type of surgery, alterations in variables related to oxygen are probably balanced by haemodynamic changes. In fact, according to Fick's formula, SvO2 is almost completely determined by SaO2 and CO, when VO2 and haemoglobin remain stable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glucose tolerance and insulin secretion in infants with the left to right shunt congenital heart disease]

Between 1980 and 1988, 32 infants under three years of age with left to right shunt congenital heart disease underwent cardiac catheterizations, and their glucose tolerance and insulin secretion were investigated. These patients were divided into three groups by weight and compared. Group I consisted of 11 patients whose weights were 80% or more of the ideal body weight (IBW) for their age. Group II consisted of 10 patients whose weights were between 70% and 80% of the IBW. Group III consisted of 11 patients whose weights were less than 70% of the IBW. The CTR and biochemical blood studies showed no difference. By cardiac catheterization, Group III showed higher pulmonary/systemic vascular pressure ratio (Pp/Ps) than Group I. The mixed venous O2 saturation (SvO2) were 69.5 +/- 6.41% in Group I, 64.8 +/- 5.78% in Group II, 57.2 +/- 3.59% in Group III. Group III showed the lowest SvO2 of the three. Group III also showed the lowest arterial O2 saturation (SaO2). This indicates that the patients of Group III had the most serious congestive heart failure. In the 0.5 g/kg intravenous glucose tolerance tests, the K values (glucose disappearance rates) were as follows: Group I: 3.30 +/- 0.597, Group II: 2.91 +/- 0.624, Group III: 2.48 +/- 0.417. Group III showed the lowest values of the three. This indicates the deterioration of glucose tolerance in Group III. In the examination of serum insulin secretion, Group III showed the lowest serum insulin levels: 26.6 +/- 18.3 mmu/ml at 3-minute intervals, 22.8 +/- 14.3 mmu/ml at 5-minute intervals. After cardiac catheterization, corrective operations were performed on 17 patients out of 32. Fifteen patients survived, though 2 patients of Group III died early postoperatively. The results of glucose tolerance test and serum insulin levels before and after operation in 12 survivors were compared. Although the K values had been 2.8 +/- 0.41 before operation, it rose up to 3.81 +/- 0.81 three to four weeks after operation. The serum insulin levels at 3, 5, 10 and 15-minute intervals also rose after operation. This indicates the improvement of glucose tolerance and insulin secretion due to the improved circulation. It is suggested that the adequate nutritional management before and after operation on infants with serious congestive heart failure, because they tend to have malnutrition before operation. Aggressive and careful nutritional management is advisable.     

Effect of reduction of postoperative days in the intensive care unit after coronary artery bypass

The high cost of medical care prompted us closely to evaluate our practice of keeping all coronary artery bypass patients in the postoperative intensive care unit a minimum of 2 days. Thirty-seven patients were randomly assigned to a 1 or 2 day postoperative stay in the intensive care unit after routine bypass grafting. Nineteen patients in Group I stayed 1 day and 18 in Group II stayed 2 days. Eighteen Group I and 17 Group II patients were evaluated. No differences in type or rate of complications occurred in either group. No deaths occurred. Total hospital costs were $340 less for Group I (not statistically significant, p greater than 0.4), room costs were $361 less for Group I (p less than 0.01), total laboratory costs were $165 less for Group I (p greater than 0.5), and costs for arterial blood gases were $325 less for Group I (p less than 0.001). No adverse effect on patient safety was found by reducing the stay in the intensive care unit from 2 days to 1 day. This and other economies can significantly reduce hospital costs for this group of patients.     

Perioperative evaluation of a new mixed venous oxygen saturation catheter in cardiac surgical patients.

Fiberoptic pulmonary artery flotation catheters have gained clinical acceptance for continuous monitoring of mixed venous oxygen saturation (SvO2), especially in the management of hemodynamically unstable patients. Therefore, the performance of the oximetry system used is extremely important. The accuracy and stability of a new two-wavelength oximetry pulmonary artery catheter and SAT-2 oximeter were assessed in adult patients during and following cardiac surgery. After in vitro calibration of the system, the catheter was inserted through the right internal jugular vein and positioned in the pulmonary artery prior to induction of anesthesia. During the study period, the system was updated for hemoglobin changes of 1.8 g/dL or more. In vivo SvO2 values obtained by the oximetry catheter were compared with those determined with a reference oximeter from simultaneously drawn mixed venous blood specimens at different intervals. A total of 604 paired data points from 52 patients were analyzed, 572 (94.7%) of which were within the 95% confidence interval. Overall bias was -1.7% +/- 3.5% (SD). The results suggest that over the time course of the study, in vivo SvO2 values obtained with the two-wavelength catheter and the SAT-2 oximeter closely approximated SvO2 measured with a reference oximeter from mixed venous blood samples (r = 0.917; SEE 3.5%) in cardiac surgical patients in whom marked physiological changes occur.     

Continuous monitoring of mixed venous oxygen saturation during aortofemoral bypass grafting

Measurement of mixed venous oxygen saturation (SvO2) may be helpful in the care of critically ill patients. Serial determinations of SvO2 give an index of the relationship between oxygen delivery and tissue oxygen consumption. Continuous monitoring of SvO2 is now readily available with the Shaw Oximetrix pulmonary artery catheter (Oximetrix Inc., Mountain View, CA). This system has provided useful information in the high risk cardiac surgery patient. Continuous monitoring of mixed venous saturation may be helpful in high risk or critically ill general and peripheral vascular surgery patients both in the intensive care unit and in the operating room. The following clinical report is presented to illustrate the usefulness of continuous SvO2 monitoring in a high risk vascular surgery patient.     

Routine SvO2 measurement after CABG surgery with a surgically introduced pulmonary artery catheter.

OBJECTIVE: It has been argued that the poor correlation between cardiac output and mixed venous oxygen saturation (SvO2) reduces the value of SvO2. Routine use of Swan Ganz catheters is also controversial in cardiac surgery. Here our clinical experience with a simplified method for routine hemodynamic monitoring and the short-term prognostic value of SvO2 after CABG surgery is presented. METHOD: Peroperatively an epidural catheter is routinely introduced through the outflow tract of the right ventricle into the pulmonary artery for monitoring of pressure and blood sampling. Clinical data were retrospectively retrieved from the records and related to SvO2 routinely obtained on admission to the ICU after 488 CABG procedures. RESULTS: Average SvO2 on arrival to ICU was 67+/-7%. The SvO2 value of 55% represented a cut off point below which a high incidence of complications were found. Outcome after 456 procedures with SvO2 > or = 55% compared with 32 procedures with SvO2 < 55%: mortality 0 vs. 9.4% (P = 0.0003), perioperative myocardial infarction 6.2 vs. 29% (P < 0.0001), ventilator treatment 8.9+/-10.1 vs. 25.7+/-54.9 h (P = 0.0074), ICU stay 1.4+/-1.2 vs. 2.1+/-1.7 days (P = 0.0010). CONCLUSIONS: SvO2 was of prognostic value and due to its specificity it seems particularly useful for telling which patients are unlikely to develop cardiorespiratory problems. Thus, this simple method for hemodynamic monitoring could contribute to cost containment as it seems that we can safely reserve Swan Ganz catheters for high-risk patients.     

Continuous monitoring of mixed venous oxygen saturation during orthotopic liver transplantation.

Hemodynamic management is an important issue concerning anesthesia for orthotopic liver transplantation (OLT). Mixed venous oxygen saturation (SvO2) is considered a good index of tissue oxygenation, but controversy exists about the usefulness of monitoring this parameter in different types of surgery. Therefore, a prospective study was performed to determine changes in SvO2 during OLT and to study the correlation between SvO2 and hemodynamic measurements. Thirty patients undergoing transplantation for end-stage liver disease were divided into two groups: group 1 (n = 15, aged 42 +/- 11 years [mean +/- SD]) without venovenous bypass (VVB), and group 2 (n = 15, aged 43 +/- 10 years) with VVB. SvO2 was greater than 74% throughout the procedure and remained stable during dissection and the anhepatic phase. There was a significant increase in SvO2 after unclamping the portal vein in group 1, whereas a significant decrease was observed during the first hour following reperfusion in group 2. There was no correlation among SvO2 and oxygen consumption, arterial oxygen saturation, (SaO2), or hemoglobin concentrations. A statistically significant correlation was found between SvO2 and cardiac index in both groups (group 1: r = 0.58, P = 0.01; group 2: r = 0.51, P = 0.01), but the correlation was relatively poor. Continuous monitoring of SvO2 may be useful, but cannot substitute for intermittent determinations of other hemodynamic or oxygenation parameters.     

Venous oxygen saturation during normovolaemic haemodilution in the pig

BACKGROUND: Hypovolaemia may be considered to represent a volume-restricted cardiac output (CO), but CO varies inversely with the haemoglobin concentration (Hb) and a maximal mixed venous oxygen saturation (SvO2) may be a better target for volume administration than a maximal CO. METHODS: In 10 anaesthetized pigs, volume loading with 6% hydroxyethyl starch was performed to obtain a maximal SvO2 followed by normovolaemic haemodilution with 6% hydroxyethyl starch. RESULTS: Volume loading increased SvO2 from 55.0+/-5.2% to 64.8+/-9.0% (mean+/-SD) associated with an increase in CO (2.3+/-0.4 to 3.5+/-0.9 l/min) and central venous oxygen saturation (ScvO2; 68.2+/-9.3% to 79.4+/-7.2%; P<0.05). Heart rate (HR), mean arterial (MAP), central venous (CVP), pulmonary arterial mean (PAMP), and occlusion pressures (PAOP) increased as well (P<0.05). In contrast, during progressive haemodilution, SvO2 and ScvO2 remained statistically unchanged until the haemoglobin concentration had decreased from 5.5+/-0.4 to 2.9+/-0.2 mM, while CO and HR increased at a haemoglobin value of 4.4+/-0.4 and 4.0+/-0.4 mM and CVP and PAOP decreased at a haemoglobin of 4.0+/-0.4 and 2.9+/-0.2 mM, respectively (P<0.05) leaving MAP unaffected. CONCLUSION: This study found that volume loading increased cardiac output and mixed and central venous oxygen saturations in parallel, but during normovolaemic haemodilution an increase in cardiac output left mixed and central venous oxygen saturations statistically unchanged until haemoglobin concentration was reduced by approximately 50%. Accordingly, volume therapy should be directed to maintain a high venous oxygen saturation rather than a change in cardiac output.     

Mixed venous oximetry

We now have the technology through reflectance spectrophotometry to evaluate and display continuously mixed venous oxygen saturation SvO2 through use of a modified pulmonary artery catheter. Adding this method of assessing the balance of oxygen supply and demand to our standard armamentarium of hemodynamic monitoring may improve our ability to diagnose and treat cardiovascular aberrations at an earlier stage than was previously possible. Through analysis of the Fick equation, it can be seen that SvO2 depends upon the cardiac output, the arterial oxygen saturation, the hemoglobin level, and the rate of oxygen consumption. These are, in turn, affected by a great number of factors (see Fig 8). As seen in the variety of patient care examples cited above, the usefulness of SvO2 monitoring continues to grow. It appears that there are no intrinsic risks associated with SvO2 monitoring beyond those of customary PA monitoring. This new technology provides us with online information not previously available, at an associated cost that needs to be further examined.     

The hemodynamic effects of propofol in children with congenital heart disease

We studied the hemodynamic effects of propofol during elective cardiac catheterization in 30 children with congenital heart disease. Sixteen patients were without cardiac shunt (Group I), six had left-to-right cardiac shunt (Group II), and eight had right-to-left cardiac shunt (Group III). The mean (+/-SD) ages were 3.8+/-3.1 yr (Group I), 3.2+/-3.7 yr (Group II), and 1.0+/-0.6 yr (Group III). After sedation and cardiac catheter insertion, hemodynamic data and oxygen consumption were measured before and after the administration of propofol (2-mg/kg bolus, 50- to 200-microg x kg(-1) x min(-1) infusion), and values were compared by using a paired t-test (significance: P < 0.05). After the propofol administration, systemic mean arterial pressure and systemic vascular resistance decreased significantly and systemic blood flow increased significantly in all patient groups; heart rate, pulmonary mean arterial pressure, and pulmonary vascular resistance were unchanged. Pulmonary to systemic resistance ratio increased (Group I, P = 0.005; Group II, P = 0.03; Group III, P = 0.10). In patients with cardiac shunt, propofol resulted in decreased left-to-right flow and increased right-to-left flow; the pulmonary to systemic flow ratio decreased significantly (Group II, P = 0.005; Group III, P = 0.01). Clinically relevant decreases in Pao2 (P = 0.008) and Sao2 (P = 0.01) occurred in Group III patients. We conclude that propofol can result in clinically important changes in cardiac shunt direction and flow. IMPLICATIONS: The principal hemodynamic effect of propofol in children with congenital heart defects is a decrease in systemic vascular resistance. In children with cardiac shunt, this results in a decrease in the ratio of pulmonary to systemic blood flow, and it can lead to arterial desaturation in patients with cyanotic heart disease.     

Mixed venous oxygen saturation during mobilization after cardiac surgery: are reflectance oximetry catheters reliable?

BACKGROUND: Oximetry catheters immediately reflect changes in mixed venous oxygen saturation (SvO2). We have used the Baxter 2-SAT system to register changes in SvO2 during early mobilizations after cardiac surgery. To assess catheter reliability, readings were compared to blood gases. METHODS: A total of 352 paired catheter and bench haemoximetry measurements were obtained at the expected highest and lowest levels of SvO2 during the mobilization procedures. The agreement between methods was explored by a Bland-Altman plot. The influence of haemoglobin (Hgb), pH, cardiac output (CO), posture, catheter identity and catheter calibration on agreement was assessed through analysis of covariance. RESULTS: Data included a substantial number of low SvO2 values, 95 paired means of SvO2 < or = 50% and 37 paired means < or = 40%. Mean oxygen saturation difference between catheter and haemoximeter readings was -1.6 +/- 5.7% (SD). Agreement between the methods depended upon the level of SvO2. At SvO2 of 65%, the two methods were virtually identical. Below 65%, the catheters increasingly underestimated the corresponding haemoximetric values by 1.5% for every 10% reduction in SvO2. Agreement was to some degree dependent on individual calibrations and catheter identity, but to a lesser extent on Hgb, CO and posture. CONCLUSION: The two methods are interchangeable for most clinical purposes. Catheter readings are, however, substantially lower than the corresponding haemoximetric measurements at low SvO2 values. Careful interpretation of the absolute values resulting from catheter measurements is recommended, especially when SvO2 readings are low.     

A case-control comparison of durability and cost between implanted reservoir and percutaneous catheters in cancer patients.

A case-control study was performed to compare the durability and cost of implanted reservoir catheter systems with percutaneous central venous catheters. Twenty cancer patients had reservoir systems placed in 1985 for chemotherapy delivery. The control group consisted of 60 cancer patients, matched according to age, sex, and diagnosis who were part of a group of more than 700 patients with percutaneous catheters inserted during the same period. The reservoir catheters were found to function for a significantly (P less than 0.0001) longer time (495 +/- 54 days) compared to the percutaneous catheters (197 +/- 22 days). The total cost for each system was calculated by adding the charges for an average insertion (reservoir = $1738, percutaneous = $562) to the maintenance charges accumulated over the catheters' lifespan. Reservoir catheters were associated with a significantly greater total cost than percutaneous catheters ($2233 +/- 54, $1453 +/- 102, respectively) but, if the total cost was spread out over the lifespan of the catheter by dividing the total cost by duration of use, reservoir catheters can be less expensive on a per diem basis. The break point occurs at approximately 6 months. For use less than 6 months, percutaneous catheters are cheaper primarily because of their lower insertion costs, but, for longer periods, reservoir catheters become cheaper because of lower maintenance costs and because a second percutaneous catheterization would likely be necessary.     

Total anomalous pulmonary venous connection in adults. Long-term follow-up.

Between 1961 and 1989, 19 patients with total anomalous pulmonary venous connection underwent surgical correction. Ages ranged from 18 to 38 years (mean 26.2 +/- 6.5 years). The anatomic variants included 10 patients with total anomalous pulmonary venous connection to the vertical vein, 6 patients with total anomalous pulmonary venous connection to the coronary sinus, and 2 with total anomalous pulmonary venous connection directly to the right atrium. The last patient had mixed connection to the coronary sinus and left vertical vein. Two patients died, one because of left atrial rupture and another of low cardiac output. Long-term follow-up after surgical repair ranged from 2 to 24 years (mean 7 +/- 6.2 standard deviation). Preoperative disability, assessed according to New York Heart Association criteria, showed 12 patients in functional class II and seven in class III. After treatment, 16 patients were in class I and one in class II (p less than 0.001). Echocardiographic evaluation of six patients revealed in all a normal left ventricular ejection fraction; the diastolic function was also normal except in one patient. The postoperative evaluation of the pulmonary arterial systolic pressure performed by both Doppler echocardiography and right cardiac catheterization in 14 patients showed a significant reduction of the mean pulmonary arterial systolic pressure from 51.1 +/- 3.4 to 37.4 +/- 14.4 mm Hg (p less than 0.01). The remaining three patients evaluated in the follow-up period only by clinical examination are in New York Heart Association functional class I. The anatomic characteristics of our patients were responsible for the long-term outcome without correction. Surgical treatment of older patients can be performed with satisfactory results and excellent long-term survival.