Venous Blood Oxygen Saturation Research Articles

Analysis of thoracic aortic blood flow during off-pump coronary artery bypass surgery.

The non-invasive monitoring of thoracic aortic blood flow (TABF) during off-pump coronary artery bypass (OPCAB) surgery is becoming more commonly used and proved to be invaluable in the early detection of haemodynamic compromise due to heart displacement. The aim of this study was to analyze the changes in the TABF during OPCAB using transoesophageal Doppler and compare them with the changes observed by other monitoring methods as cardiac output, invasive pulmonary and radial pressures and mixed venous oxygen saturation. The measurements obtained from classic haemodynamic monitoring methods including the radial artery line and the pulmonary artery catheter with continuous monitoring of the cardiac output and mixed venous blood oxygen saturation were compared to the measurements of TABF obtained from a transoesophageal Doppler probe in 15 consecutive patients who underwent OPCAB surgery. The TABF decreased significantly during the construction of coronary anastomoses from 3.42 +/- 0.94 l/min (baseline) to 2.2 +/- 0.8 l/min during the first coronary anastomosis and then to 2.14 +/- 1.12 l/min during the second coronary anastomosis (F=4.29, P=0.008). TABF returned to the baseline values (2.85 +/- 1.19 l/min) at chest closure. The cardiac output measurement showed no significant decrease compared to baseline. Low TABF occurred without significant changes in the measurements obtained from classic haemodynamic monitoring methods during OPCAB surgery. This finding could be of vital importance in helping improve the monitoring and consequently the management of patients undergoing OPCAB surgery.

Myocardial ischemia in intestinal postischemic shock: the effect of hypoxemic reperfusion.

The circulatory shock following intestinal ischemia-reperfusion injury has been attributed to hypovolemia. The purpose of the current study is to clarify the pathophysiology of this type of shock and to test the hypothesis that hypoxemic compared with normoxemic reperfusion improves hemodynamics. Randomized animal study. Medical school laboratory. Twenty-one pigs. Pigs were subjected to 120 mins of intestinal ischemia by clamping the superior mesenteric artery. Upon declamping, the animals were randomized into two groups: a group that received hypoxemic reperfusion (HR group, n = 8) with a PaO2 = 30-35 and a control group reperfused with PaO2 = 100 mm Hg (control group, n = 13). Measurements included mean arterial pressure, cardiac index, pulmonary artery occlusion pressure, and requirements for fluids and epinephrine. Biopsies from the terminal ileal mucosa were taken for malondialdehyde measurements at baseline, at 120 mins of ischemia, and at 30 and 60 mins of reperfusion. A piece of left ventricle was obtained after 120 mins of reperfusion for histologic studies. Five of 13 animals of the control group died in intractable shock; no animal of the HR group died (p =.11). The decrease in the mean arterial pressure during reperfusion was more pronounced in the control group (p <.008) despite the larger doses of epinephrine administered, compared with the HR group (p <.02). During reperfusion, both groups exhibited a decrease in cardiac index; this was more pronounced in the control group (p =.0007). Pulmonary artery occlusion pressure increased during reperfusion in both groups and was more pronounced in the control group (p =.04 at 60 mins). Although mixed venous blood oxygen saturation of the control animals was higher at 30 mins of reperfusion (p =.005), it declined after 60 mins and became lower than that of HR animals at the end of reperfusion (p <.02). The myocardial histopathologic injury score was higher in the control group (2.0 +/- 0.69 and 3.4 +/- 0.89 for the HR and control groups, respectively; p <.03). The concentrations of intestinal mucosa malondialdehyde were significantly higher in the control group at 60 mins of reperfusion (p <.03). Acute myocardial ischemia and left heart failure significantly contribute to the circulatory shock that follows intestinal ischemia/reperfusion injury and are attenuated by hypoxemic reperfusion.

Donitriptan selectively decreases jugular venous oxygen saturation in the anesthetized pig: further insights into its mechanism of action relevant to headache relief.

The effects of donitriptan on systemic arterial-jugular venous oxygen saturation difference were evaluated in pentobarbitone-anesthetized pigs. Oxygen and carbon dioxide partial pressures in systemic arterial and jugular venous blood as well as hemoglobin oxygen saturation were determined by conventional blood gas analysis. Vehicle (40% polyethyleneglycol in saline, n = 9) or donitriptan (0.01, 0.04, 0.16, 0.63, 2.5, 10, and 40 microg/kg, n = 7) were cumulatively infused over 15 min/dose. The involvement of 5-hydroxytryptamine(1B) (5-HT(1B)) receptors was assessed in the presence of the 5-HT(1B/1D) receptor antagonist, GR 127935. Donitriptan decreased markedly and dose dependently jugular venous oxygen saturation [ED(50) 0.5 (0.3-1.1) microg/kg], in parallel with increases in carotid vascular resistance [ED(50) 0.9 (0.7-1.1) microg/kg]. Since arterial oxygen saturation and partial pressure remained unchanged, donitriptan significantly increased arteriovenous oxygen saturation difference from 0.63 microg/kg (maximal variation: 57 +/- 18%, P < 0.05 compared with vehicle). Unexpectedly, donitriptan from 2.5 microg/kg induced marked and significant increases in carbon dioxide partial pressure (pVCO(2)) in venous blood (maximal increase 18.8 +/- 5.7%; P < 0.05 compared with vehicle). Pretreatment with GR 127935 (0.63 mg/kg, n = 5) abolished the fall in venous oxygen saturation and the increase in carotid vascular resistance and reduced the increases in pVCO(2) induced by donitriptan. The results demonstrate that donitriptan, via 5-HT(1B) receptor activation, decreases the oxygen saturation of venous blood draining the head, concomitantly with cranial vasoconstriction. Since donitriptan also increased pVCO(2), an effect upon cerebral oxygen consumption and metabolism is suggested in addition to cranial vasoconstriction, which may be relevant to its headache-relieving effects.

Methylmercaptan Poisoning: Usefulness Of Monitoring Jugular Venous Oxygenation

A 47-year-old man admitted for a confused state and severe metabolic acidosis shortly after exposure to methylmercaptan. To treat methylmercaptan-induced cytotoxic hypoxia and resultant confusion status, mechanical ventilation was performed to maintain an adequate oxygen supply to organs, especially to the brain. Sodium nitrite (3%, total 40ml), which caused methemoglobinemia (maximally 22%), was given intravenously to remove methylmercaptan from the cytochrome oxidase complex. Oxygen content in arterial blood was maintained at over 15ml/dl throughout the time course in our intensive care unit. Jugular venous oxyhemoglobin (Hbo2) decreased to 60%; Sjvo2 (oxygen saturation in the jugular venous blood) was maintained at over 75%. His level of consciousness improved on the next day. The treatment for methylmercaptan poisoning is similar to that for hydrogen sulfide poisoning. Excessive sodium nitrite treatment might cause hypoxic hypoxia due to induced methemoglobinemia. Jugular venous Hbo2 may indicate the adequate degree of induced methemoglobinemia at a point of the balance between oxygen delivery and consumption in the brain.

Usefulness of venous oxygen saturation in the jugular bulb for the diagnosis of brain death: report of 118 patients.

To assess the usefulness of venous oxygen saturation in the jugular bulb (SjO(2)) as a complementary test for the diagnosis of brain death. Prospective observational study. Polytrauma intensive care unit (ICU) of an acute-care teaching hospital in Santander, Spain. We studied 118 (44%) out of 270 patients with severe head injury and intracranial hemorrhage meeting criteria of brain death (lack of cardiac response to atropine, unresponsive apnea, and iso-electric EEG in the absence of shock, hypotension and treatment with muscle relaxants and/or central nervous system (CNS) depressant drugs). At the moment at which clinical diagnosis of brain death was made and an iso-electric EEG was obtained, simultaneous oxygen saturation in central venous blood (right atrium) (SvO(2)) and jugular venous bulb (SjO(2)) samples was measured. The ratio between SvO(2) and SjO(2), expressed as CvjO(2) (the so-called central venous-jugular bulb oxygen saturation rate; CvjO(2) = SvO(2)/SjO(2)) was calculated. CvjO(2) less than 1 was obtained in 114 patients [mean (SD): 0.89 (0.02)], whereas CvjO(2) greater than 1 was obtained in only 4 (3.38%). In the group of 152 survivors, a single patient was discharged from the ICU in a vegetative state in which CvjO(2) was below 1. CvjO(2)as a complementary test for the diagnosis of brain death showed 96.6% sensitivity, 99.3% specificity, and 99.1% and 97.4% positive and negative predictive values, respectively. Central venous-jugular bulb oxygen saturation rate below 1 together with accepted clinical criteria (unresponsive coma with brainstem areflexia) provides non-invasive assessment of cerebral circulatory arrest that can help to suspect brain death.

Recirculation in double lumen catheter veno-venous extracorporeal membrane oxygenation measured by an ultrasound dilution technique.

Recirculation is a limiting factor for oxygen delivery in double lumen catheter veno-venous extracorporeal membrane oxygenation (DLVV-ECMO). This study compares three different methods for the determination of the recirculation fraction during double lumen catheter veno-venous ECMO at ECMO flow rates of 150, 125, 100, 75, and 50 ml/kg.min in nine lambs: (1) an ultrasound dilution method, in which the change in ultrasound velocity in blood after injection of a saline bolus as a marker is used for determination of recirculation; (2) an SvO2 method using real mixed venous blood oxygen saturation, the gold standard, for determination of recirculation fraction; and (3) the CVL method, in which oxygen saturation of a blood sample of the inferior vena cava is considered to represent mixed venous oxygen saturation. In all methods, the recirculation fraction increased with increasing ECMO flow rate. The correlation coefficient between the ultrasound dilution method and the SvO2 method was 0.68 (p < 0.01); mean difference was -2.4% (p = 0.6). Correlation coefficient between the ultrasound dilution method and the CVL method was 0.48 (p < 0.01); mean difference was -18.1% (p < 0.01). The correlation coefficient between the SvO2 method and the CVL method was 0.51 (p < 0.01); mean difference was -15.7% (p < 0.01). The ultrasound dilution method is a useful method for measurement of the recirculation fraction in DLVV-ECMO and is easier to use than the other methods.

A low-cost transmittance transducer for measurement of blood oxygen saturation in extracorporeal circuits.

Designs for a low-cost dual wavelength transducer based on light transmittance and a disposable cuvette for monitoring oxygen saturation (SO2) in extracorporeal arterial and venous blood are presented. The transducer utilizes red and infrared light-emitting diodes and a large photodiode; it is designed to attach to a flow-through cuvette modified from 3/8-in x3/8-in bypass-circuit connectors. A mock extracorporeal circulation system was assembled to evaluate operation of the transducer at a controlled blood SO2 and the relationship between light transmittance and hemodilution. SO2 was calculated based on multiple linear regression analyses. The results show a high correlation between the SO2 obtained with the equipment designed and values measured with commercial gasometric equipment in the range of 50% to 100% (r2 = 0.976, error <2%). The method presented allows continuous and real time measurement of whole blood SO2 with a low-cost transmittance transducer.

Neurochemical monitoring in the management of severe head-injured patients with hypothermia

The neuroprotective action and effect of hypothermia on the neurochemical system is not well understood. The present study was performed using six patients with GCS scores of 5 or less to clarify the relationship between monitored brain temperature, intracranial pressure (ICP), cerebral perfusion pressure (CPP) and oxygen saturation of the jugular venous blood (SjO2). Changes in concentration of excitatory amino acids, glutamate (CLU) and aspartate (ASP), and NO2 were studied using intracerebral microdialysis as well as in jugular venous blood and cerebrospinal fluid (CSF). Changes in brain temperature, CPP and SjO2 resulting from hypothermia and brain death associated with markedly higher concentrations of and fluctuations in the concentrations of CLU, ASP and NO2 were observed in the dfalysate than in the jugular venous blood or CSF. Hypothermic treatment significantly reduces excitatory amino acid and NO2 concentrations, a finding which was associated with an improvement in CPP and SjO2. Measurement of CLU and ASP using intracerebral microdialysis is a clinically useful method for clarifying abnormal neurochemical events associated with severe head injury and for evaluating the effects of hypothermia. [Neurol Res 2000; 22: 657-664]

Development of a new instrument to measure oxygen saturation and total hemoglobin volume in local skin by near-infrared spectroscopy and its clinical application.

The oxygen saturation (StO2) and total hemoglobin volume in cutaneous blood are closely related to cutaneous metabolism and are important factors in determining the skin color. Most conventional apparatuses for the measurement of cutaneous metabolism have been designed to evaluate qualitative changes in the oxyhemoglobin volume, deoxyhemoglobin volume, and their sum (total Hb volume) relative to their baseline values. In this study, we developed an instrument for non-invasive evaluation of individual and regional differences in StO2 and Hb volume, a system unaffected by melanin (Kao PSA system model III), and examined the validity of its application. First, changes in StO2 and total Hb volume in the antebrachial region during venous occlusion and devascularization by compression of the brachial region were evaluated. Changes in total Hb volume following venous occlusion were found to reflect the cutaneous blood flow. Also, StO2 was considered to reflect the state of oxygen consumption by the skin, because it was markedly reduced during devascularization. Next, the subjects were exposed to graded hypobaric conditions, and the relationships among StO2, arterial blood oxygen saturation (SaO2), and venous blood oxygen saturation (SvO2) were studied. StO2 showed significant positive correlations with SaO2 (r=0.811, P<0.001) and SvO2 (r=0.966, P<0.001), and its correlation with SvO2 was particularly strong. Therefore, StO2 was found to be closely dependent on SvO2. Lastly, StO2, total Hb volume, and other parameters were measured in healthy women (aged 20-69 years), and their regional differences and age-associated changes were evaluated. These regional differences (angle of mouth > cheek > forehead) and age-associated decreases in StO2 are considered to be caused by the age-associated decreases in the cutaneous blood flow.

Hemodynamic Classification in Acute Myocardial Infarction

Current mortality (M(1)) in hemodynamic subgroups of patients with acute myocardial infarction (AMI) was compared to that observed 30 years ago (M(0)), when hemodynamic classification was established. The prognostic value of oxyhemodynamic indexes in predicting M(1) for patients receiving right heart catheterization (RHC) was investigated.We assigned 393 patients with AMI (mean age, 72 +/- 10 years) to four Killip categories. A fiberoptic reflectance catheter was inserted in the pulmonary artery (PA) in 136 patients. Cardiac index (CI), PA wedge pressure (PWP), PA mixed venous blood oxygen saturation (SvO(2)), oxygen extraction ratio (O(2)ER), and normalized CI (NCI; CI/O(2)ER) were measured. Catheterized patients were classified into four Forrester groups, and M(1) and M(0) were compared. Survivors (group S) were compared to nonsurvivors (group NS), and the prognostic value of oxyhemodynamic parameters in predicting M(1) was estimated.A significant decline in total mortality was observed (M(1) of 8% vs M(0) of 34%; p < 0.0001). In catheterized patients, total M(1) was also decreased (M(1) of 15% vs M(0) of 26%; p < 0.05). Compared with group S, group NS had lower (mean +/- SD) CI (1.8 +/- 0.4 L/min/m(2) vs 2.4 +/- 0.6 L/min/m(2); p < 0.01), SvO(2) (46.1 +/- 10.6% vs 59.9 +/- 10.0%; p < 0.01), NCI (4.2 +/- 1.4 vs 7.4 +/- 4.1 L/min/m(2); p < 0.01), and higher PWP (22.7 +/- 6.8 mm Hg vs 14. 4 +/- 4.7 mm Hg; p < 0.01). NCI presented the best sensitivity (81%), specificity (78%), and predictive value (40%), in predicting M(1).The historical AMI hemodynamic classification has lost its semiquantitative value, since mortality has decreased. RHC does not compromise the outcome. NCI has a high prognostic value in predicting early mortality.

Experimental determination of the safe minimum perfusion flow rate for low-flow hypothermic cardiopulmonary bypass

This study investigated the safe minimum perfusion flow rate for low-flow hypothermic cardiopulmonary bypass in a canine model. The adequacy of cerebral oxygenation was determined from the adenosine concentration, the oxygen saturation of cerebral venous blood and brain oxyhemoglobin level. In experiment 1, nine beagles were cooled on bypass to a nasopharyngeal temperature of 18°C and the perfusion flow rate was reduced in a stepwise fashion every 30 min from 100 to 50, 30, 20 and 10 ml/kg per min. In experiment 2, six beagles were cooled on bypass as in experiment 1, and flow was maintained at 30 ml/kg per min for 120 min. At a perfusion flow rate of 30 ml/kg per min, adequate cerebral oxygenation was maintained for 120 min. In contrast, perfusion flow rates of 20 and 10 ml/kg per min were associated with cerebral ischemia.

Does gastric tonometry monitor splanchnic perfusion?

To define whether the gastric mucosal-arterial PCO2 gradient (PCO2 gap) reliably reflects hepatosplanchnic oxygenation in septic patients. Prospective observational clinical study. An adult, 31-bed medical/surgical department of intensive care of a university hospital. A total of 36 hemodynamically stable, invasively monitored, mechanically ventilated, sedated, paralyzed patients with severe sepsis. In each patient, hepatosplanchnic blood flow was determined by the continuous indocyanine green infusion technique and gastric mucosal PCO2 by the saline tonometry technique. Suprahepatic venous blood oxygen saturation and PCO2 also were measured. The mesenteric veno-arterial PCO2 gradient was determined as the difference between the suprahepatic venous blood PCO2 and the arterial blood PCO2. There were significant correlations between the hepatosplanchnic blood flow and the suprahepatic venous blood oxygen saturation (r2 = .56; p<.01), between the hepatosplanchnic blood flow and the mesenteric veno-arterial PCO2 gradient (r2 = .55; p<.01), and also between the suprahepatic venous blood oxygen saturation and the mesenteric veno-arterial PCO2 gradient (r2 = .64; p<.01). There was no statistically significant correlation between the PCO2 gap and the hepatosplanchnic blood flow, the suprahepatic venous blood oxygen saturation or the mesenteric veno-arterial PCO2 gradient. In stable septic patients, the PCO2 gap is not correlated with global indexes of gut oxygenation. The interpretation of PCO2 gap is more complex than previously thought.

Quantitative magnetic resonance imaging in experimental hypercapnia: improvement in the relation between changes in brain R2 and the oxygen saturation of venous blood after correction for changes in cerebral blood volume.

Acute hypercapnia simultaneously induces increases in regional cerebral blood volume (rCBV) and the oxygen saturation of cerebral venous blood (Yv). Changes in both physiologic parameters may influence the changes in R2 (deltaR2) that can be measured in the brain with gradient echo magnetic resonance imaging. The authors examined the effect of incorporating independent measurements of the change in rCBV (deltarCBV) on the fidelity of the relation between deltaR2 and deltaYv in the setting of experimental hypercapnia. A two-dimensional T2-weighted gradient echo sequence was used to measure deltaR2 in the brain parenchyma of anesthetized rats in response to hypercapnia with respect to the control state. In parallel, estimates of rCBV were obtained using a three-dimensional steady-state approach in conjunction with a paramagnetic contrast agent during both control and hypercapnic states so that a deltarCBV could be calculated. Regional CBV values of 2.96 +/- 0.82% and 5.74 +/- 1.21% were obtained during the control and hypercapnic states, respectively, and linear relations between rCBV and CO2 tension in both arterial (r = 0.80) and jugular venous (r = 0.76) blood samples were obtained. When correlating deltaR2 directly with deltaYv, no clear relation was apparent, but a strong linear relation (r = 0.76) was observed when correction for deltarCBV was incorporated into the data analysis. These results are consistent with the current understanding of the mechanisms of blood oxygen level-dependent (BOLD) contrast and underscore the potential importance of taking into account deltarCBV when quantitative estimates of deltaYv from the "BOLD effect" are intended.

Assessment of myocardial response to pharmacologic interventions using an improved MR imaging technique to estimate T2 values.

Our objective was to improve a previously developed MR imaging sequence for the in vivo estimation of the myocardial T2* value and to evaluate, in healthy human subjects, the response of myocardial T2* value to two different pharmacologic interventions. The modified technique improved the quality of the images obtained and increased the reliability of myocardial T2* measurements. Using the modified technique, the myocardial T2* value increased significantly over baseline values after the administration of dipyridamole but did not significantly change after the administration of dobutamine. These observations are consistent with the expected response of myocardial venous blood oxygen saturation levels to the infusion of the two pharmacologic agents.

Retinal oxygen consumption during hyperglycemia in patients with diabetes without retinopathy

This study aimed to determine whether retinal oxygen consumption in patients with diabetes without retinopathy is affected by acute changes in blood glucose. The study design was a nonrandomized, interventional clinical study. The study consisted of 12 patients with diabetes without ophthalmoscopically visible diabetic retinopathy whose ages were 20 to 59 years (mean, 33.7 years). Retinal vessel oximetry was performed on subjects during normoglycemia and during acutely induced hyperglycemia. Hyperglycemia was achieved with the ingestion of an oral glucose load. Changes in retinal arterial and venous blood oxygen saturation resulting from systemic blood glucose changes were measured. Measurements were made using a noninvasive, two-wavelength digital imaging retinal vessel oximeter. In each subject, the measured retinal venous blood oxygen saturation decreased significantly during hyperglycemia. The amount of decrease in venous oxygen saturation associated with hyperglycemia was positively correlated with the duration of diabetes. The measured retinal arterial oxygen saturation did not change significantly during hyperglycemia. These results, taken with the observations of numerous other investigators that show increased blood flow during acute hyperglycemia, provide evidence of substantially increased retinal oxygen consumption during hyperglycemia. The results also complement previous observations of the effect of diabetes on retinal autoregulation.

The effect of position on intracranial pressure

The question as to whether the head and trunk of neurosurgery patients should be elevated remains controversial. This question is particularly important when intracranial hypertension is present. Head up position may have beneficial effects on intracranial pressure (ICP) via changes in mean arterial pressure (MAP), airway pressure, central venous pressure and cerebro spinal fluid displacement. However, in some circumstances, head up position may decrease MAP which in turn will result in a paradoxical rise in ICP through autoregulation mechanisms. Therefore, the degree of head elevation has to be titrated by evaluating the most adequate cerebral perfusion pressure (CPP) for each patient by means of transcranial Doppler or measurement of jugular venous blood oxygen saturation. Head elevation above 30 degrees should be avoided in all cases. In most patients with intracranial hypertension, head and trunk elevation up to 30 degrees is useful in helping to decrease ICP, providing that a safe CPP of at least 70 mmHg or even 80 mmHg is maintained. Patients in poor haemodynamic conditions are best nursed flat. CPP is thus the most important factor in assessment and monitoring when considering head elevation in patients with increased ICP.

Use of jugular venous blood, compared with mixed venous blood, for measurement of venous oxygenation indices in a porcine model of endotoxic shock

Abstract Objective To evaluate the reliability of oxygen saturation and oxygen content values measured from jugular venous blood in estimating values measured from mixed venous blood during endotoxic shock. Animals 14 random-bred 10- to 15-kg Yorkshire pigs. Procedure 60 pairs of heparinized blood samples were simultaneously collected from the pulmonary artery and right jugular vein during an independent study, using a porcine model of endotoxic shock. Endotoxic shock was induced by infusion of Escherichia coli endotoxin. Eighteen of the sample pairs were obtained from pigs prior to infusion of endotoxin or from control pigs. Oxygen saturation and venous oxygen content were measured by direct oximetry. Analysis of bias and precision was used to compare jugular venous blood values with values obtained from mixed venous blood. Samples from endotoxemic pigs were subclassified on the basis of abnormal states of global oxygen imbalance associated with septic shock. Results Indices of venous oxygenation measured from jugular venous blood were an imprecise method of estimating values measured from mixed venous blood. There was no significant difference in bias between nonendotoxemic and endotoxemic pigs, regardless of abnormal hemodynamic states. Conclusion Jugular venous blood oxygen saturation and oxygen content values should not be used to assess global oxygen transport during endotoxic shock. (Am J Vet Res 1997;58:910–914)

Predictive Factors for Usefulness of Fiberoptic Pulmonary Artery Catheter for Continuous Oxygen Saturation in Mixed Venous Blood Monitoring in Cardiac Surgery

The main goal of this prospective study was to identify among cardiac surgery patients, usually monitored through a standard pulmonary artery catheter (PAC), those in whom a fiberoptic catheter oximeter to measure oxygen saturation in mixed venous blood (SVO2 PAC) would be most useful.Data from 286 patients who underwent coronary artery bypass graft (50%) or valvular surgery were recorded, including ASA physical status, New York Heart Association (NYHA) classification, and Parsonnet score (PS). Hemodynamic events and SVO2 changes were collected intra- and postoperatively until weaning from mechanical ventilation. The anesthesiologist in charge graded the usefulness of SVO2 PAC, and another anesthesiologist carried out a blindly controlled overall evaluation. Usefulness was defined as the presence of a change in therapeutic maneuver triggered solely by continuous SVO2 data that would not have occurred based on other routine parameters. SVO2 was also considered useful if earlier recognition of significant adverse events occurred. SVO2 PAC was useful in 57% of the patients. Independent predictive factors (multivariate analysis) for the perioperative usefulness of SVO2 in the whole population consisted of ASA class >or=to4 (P < 10-5; relative risk [RR] 1.78, 1.51-2.07), mitral surgery (P < 10-4; RR 1.72, 1.4-2.02), and NYHA score >or=to3 (P < 0.01; RR 1.66, 1.35-2.05). Independent predictive factors for the perioperative usefulness of SVO2 in the coronary artery bypass graft population were NYHA score >or=to 3 (P < 10-5; RR 1.90, 1.42-2.55) and ASA class >or=to 4 (P < 0.01; RR 1.99, 1.51-2.63). The presence of three stenosed coronary arteries showed borderline significance (P < 0.06), Independent predictive factors for perioperative usefulness of SVO2 in the valvular population were mitral pathology (P < 10-5) and ASA class >or=to 4 (P < 0.01). The receiver operator characteristic curve assessed the predictivity of the PS. SVO2 PAC was more useful in the group of patients with the greatest severity of illness (PS in useful group 17.0 +/- 10.3; in nonuseful group 8.7 +/- 6.6; P < 10-4). Intensive care unit duration and hospital stay in the useful group was prolonged compared with the nonuseful group. Similarly, morbidity was frequent in the useful group, although it was not always significantly different from the nonuseful group according to the type of complications. Mortality was comparable in the groups despite their different degree of illness and was reduced when taking into account the predictive and observed mortality provided by the PS. This study defined independent preoperative factors associated with SVO2 PAC monitoring and proposed a cutoff point above which SVO2 may be useful. (Anesth Analg 1997;85:2-10)

Predictive factors for usefulness of fiberoptic pulmonary artery catheter for continuous oxygen saturation in mixed venous blood monitoring in cardiac surgery.

The main goal of this prospective study was to identify among cardiac surgery patients, usually monitored through a standard pulmonary artery catheter (PAC), those in whom a fiberoptic catheter oximeter to measure oxygen saturation in mixed venous blood (SVO2 PAC) would be most useful. Data from 286 patients who underwent coronary artery bypass graft (50%) or valvular surgery were recorded, including ASA physical status, New York Heart Association (NYHA) classification, and Parsonnet score (PS). Hemodynamic events and SVO2 changes were collected intra- and postoperatively until weaning from mechanical ventilation. The anesthesiologist in charge graded the usefulness of SVO2 PAC, and another anesthesiologist carried out a blindly controlled overall evaluation. Usefulness was defined as the presence of a change in therapeutic maneuver triggered solely by continuous SVO2 data that would not have occurred based on other routine parameters. SVO2 was also considered useful if earlier recognition of significant adverse events occurred. SVO2 PAC was useful in 57% of the patients. Independent predictive factors (multivariate analysis) for the perioperative usefulness of SVO2 in the whole population consisted of ASA class > or = 4 (P < 10(-5); relative risk [RR] 1.78, 1.51-2.07), mitral surgery (P < 10(-4); RR 1.72, 1.4-2.02), and NYHA score > or = 3 (P < 0.01; RR 1.66, 1.35-2.05). Independent predictive factors for the perioperative usefulness of SVO2 in the coronary artery bypass graft population were NYHA score > or = 3 (P < 10(-5); RR 1.90, 1.42-2.55) and ASA class > or = 4 (P < 0.01; RR 1.99, 1.51-2.63). The presence of three stenosed coronary arteries showed borderline significance (P < 0.06). Independent predictive factors for perioperative usefulness of SVO2 in the valvular population were mitral pathology (P < 10(-5)) and ASA class > or = 4 (P < 0.01). The receiver operator characteristic curve assessed the predictivity of the PS. SVO2 PAC was more useful in the group of patients with the greatest severity of illness (PS in useful group 17.0 +/- 10.3; in nonuseful group 8.7 +/- 6.6; P < 10(-4)). Intensive care unit duration and hospital stay in the useful group was prolonged compared with the nonuseful group. Similarly, morbidity was frequent in the useful group, although it was not always significantly different from the nonuseful group according to the type of complications. Mortality was comparable in the groups despite their different degree of illness and was reduced when taking into account the predictive and observed mortality provided by the PS. This study defined independent preoperative factors associated with SVO2 PAC monitoring and proposed a cutoff point above which SVO2 may be useful.

Open-chest cardiac massage without major thoracotomy: metabolic indicators of coronary and cerebral perfusion

Objective: to compare the coronary and cerebral perfusion achieved using a novel method of minimally-invasive, direct cardiac massage to that obtained using bimanual, open-chest cardiac massage. Design: prospective, controlled animal study with repeated measures. Setting: university research laboratory. Subjects: large domestic swine. Interventions: aortic, coronary sinus, jugular venous and pulmonary artery catheters were placed. Following an equilibration period, ventricular fibrillation was induced. After 4 min of untreated ventricular fibrillation, animals underwent bimanual, open-chest cardiac massage ( N=6) or minimally-invasive, direct cardiac massage using a novel device for direct cardiac compression ( N=6). Adrenaline was administered at a dose of 1 mg intravenously every 5 min. Measurements: systemic metabolic parameters, (arterial P O 2 , P CO 2 and lactate concentration) and coronary sinus and jugular venous metabolic parameters (pH, PV O 2 , SV O 2 , PV CO 2 and lactate concentration) were measured and calculated (coronary sinus/jugular-arterial SV O 2 , coronary sinus/jugular-arterial P CO 2 and lactate differences) at baseline and at 10, 20 and 30 min following induction of ventricular fibrillation. Animals were euthanised after 30 min with no attempt at defibrillation. Main Results: oxygen tension and oxygen saturation of coronary sinus blood declined significantly during the experimental period, but no differences were noted between treatment groups. The coronary sinus-arterial oxygen saturation difference increased during the study with no significant differences between groups. Coronary sinus P CO 2 and the coronary sinus-arterial P CO 2 difference increased significantly in both experimental groups during cardiac massage. No inter-group differences were noted. A similar relationship was noted in coronary sinus lactate values. The coronary sinus-arterial lactate difference displayed a positive balance at all intervals with no differences noted between group values. The oxygen tension and oxygen saturation of jugular venous blood, were reduced from baseline levels with both treatments. The jugular-arterial oxygen saturation difference increased in both groups compared to baseline values. Between group values were significantly different only at the 20 min interval. Both the jugular venous P CO 2 and the jugular-arterial P CO 2 gradient were elevated at all intervals, but no inter-group differences were noted. Jugular venous lactate concentration rose steadily with time in both groups. No significant increase in the jugular-arterial lactate gradient was noted at any time point. Conclusions: minimally-invasive, direct cardiac massage provides coronary and cerebral perfusion similar to that achieved using standard open-chest cardiac massage. This method may provide a more effective substitute for standard, closed-chest cardiac massage in cases of refractory cardiac arrest.