Hypotension during gradual blood loss: waveform variables response and absence of tachycardia.

BACKGROUND: Variation in arterial pressure and plethysmographic waveforms has been shown to be predictors of cardiac output response to fluid challenge. The objective of this study was to evaluate the ability of arterial and plethysmographic waveform variables to predict hypotension during blood loss. METHODS: Patients undergoing autologous haemodilution were studied. After anaesthesia induction, blood was withdrawn in steps of 2% of estimated circulating blood volume (ECBV). Arterial and plethysmographic waveforms were recorded and analysed offline at each step of blood withdrawal. RESULTS: Thirty-four (29%) out of 118 studied patients tolerated 20% ECBV withdrawal without hypotension. Patients who tolerated 20% ECBV withdrawal were younger than those who did not [mean (sd): 53.8 (11.1) vs 62.7 (10.7); P<0.0001]. Patients with hypertension developed hypotension earlier than healthier patients did. There were no differences at the baseline in arterial and plethysmographic waveform variables between those who did and those who did not tolerate 20% of ECBV withdrawal. All values of variables increased significantly from the baseline after the withdrawal of 4% of ECBV (P<0.005). There were no changes in heart rate (HR), 73 (12) at the baseline and 76 (13) after 20% of ECBV withdrawal (P=0.4). CONCLUSIONS: Arterial and plethysmographic waveform variables were augmented with increasing blood loss in all patients. Older patients, patients who received anti-hypertensive drugs, or both developed hypotension earlier than others. Baseline values were weak predictors of hypotension during stepwise blood withdrawal. No clinically significant increase in HR was observed, regardless of tolerance of arterial pressure to blood withdrawal.

The venous system during pregnancy. Part 1: physiologic considerations.

An essential contributor to the hemodynamic responses observed during pregnancy, the venous system is affected by hormones, blood volume, flow rates, and an enlarging uterus. The venous system is a dynamic reservoir for blood volume, within which a virtual point of conversion between unstressed volume (Vu) and stressed volume (Vs) exists. The physiologic importance of the venous system during pregnancy is best understood when the basic concepts, functional characteristics, and alterations in pregnancy are reviewed.

The venous system during pregnancy. Part 2: clinical implications.

Maternal positioning, medications, and other modulations to the venous system can affect maternal and fetal well-being. The venous system is a dynamic reservoir for blood volume, in which a virtual point of conversion between unstressed volume (Vu) and stressed volume (Vs) exists. The anatomic and physiologic changes associated with hypotension (e.g. supine and neuraxial technique-induced), hypertension (e.g. preeclampsia), and fluid management (e.g. early recovery after cesarean delivery protocols) are opportunities to consider the important role of the venous system in pregnancy.

Insides and essences: early understandings of the non-obvious.

Insides and essences are both critical concepts for appreciating the importance of non-obvious entities: neither are observable, both contrast with external appearances, and both can be more important than external appearances. The present research examined understandings of insides and essences in 3- to 5-year-old children. In Study 1, children were asked questions requiring them to think about both the insides and the outer appearances of a series of objects. In Study 2, children were tested on their understanding that insides are typically more important than outer surfaces for an object's identity and functioning. In Studies 3, 4, and 5, children were tested on their understanding of innate potential, a concept that reflects understanding of an inborn essence. Contrary to the traditional view of children as externalists (cf. Piaget, 1951), these studies demonstrate that by age 4 children have a firm grasp of the importance of both insides and essences. Even by age 3 children reason clearly about the inside-outside distinction. These results suggest that preschool children attend to non-obvious features and realize their privileged status. They may also indicate a more basic predisposition toward psychological essentialism in young children.

Young children are sensitive to how an object was created when deciding what to name it.

How do young children extend names for human-made artifacts, such as knife, toy, and painting? We addressed this issue by showing 3-year-olds, 5-year-olds, and adults a series of simple objects and asking them for each, 'What is this?' In one condition, the objects were described as purposefully created; in another, the objects were described as being created by accident. This manipulation had a significant effect on the participants' responses: even 3-year-olds were more likely to provide artifact names (e.g. 'a knife') when they believed the objects were intentionally created and material-based descriptions (e.g. 'plastic') when they believed the objects were accidentally created. This result supports a theory of artifact naming in which intuitions about intention play an important role.

A cross-linguistic comparison of generic noun phrases in English and Mandarin.

Generic noun phrases (e.g. 'bats live in caves') provide a window onto human concepts. They refer to categories as 'kinds rather than as sets of individuals. Although kind concepts are often assumed to be universal, generic expression varies considerably across languages. For example, marking of generics is less obligatory and overt in Mandarin than in English. How do universal conceptual biases interact with language-specific differences in how generics are conveyed? In three studies, we examined adults' generics in English and Mandarin Chinese. The data include child-directed speech from caregivers interacting with their 19-23-month-old children. Examples of generics include: 'baby birds eat worms' (English) and da4 lao3shu3 yao3 bu4 yao3 ren2 ('do big rats bite people or not?') (Mandarin). Generic noun phrases were reliably identified in both languages, although they occurred more than twice as frequently in English as in Mandarin. In both languages, generic usage was domain-specific, with generic noun phrases used most frequently to refer to animals. This domain effect was specific to generics, as non-generic noun phrases were used most frequently for artifacts in both languages. In sum, we argue for universal properties of 'kind' concepts that are expressed with linguistically different constructions. However, the frequency of expression may be influenced by the manner in which generics are expressed in the language.

Shape and representational status in children's early naming.

Why are ontological distinctions commonly ignored in ordinary language use? For example, why is a toy bear called a 'bear'? Jones and Smith argue that shape is central to the semantic representations of both children and adults (Jones, S.S., Smith, L.B., 1993. The place of perception in children's concepts. Cognitive Development 8, 113-139). In contrast, Soja et al. suggest that children do not rely on shape per se, but rather name representations, which are often indexed by shape (Soja, N.N., Carey, S., Spelke, E.S. 1992. Perception, ontology, and word meaning. Cognition 45, 101-107). Two studies were designed to test the latter hypothesis. Forty-seven children (2 years 5 months-3 years 11 months) and 32 adults participated. Each saw a series of line-drawings roughly shaped like various namable objects (e.g. a man). For half the participants, each line-drawing was described as depicting a shape that was created intentionally (e.g. someone painted a picture). For the remaining participants, each drawing was described as depicting a shape that was created accidentally (e.g. someone spilled some paint). Participants were simply asked to name each picture. We hypothesized that subjects would use shape as the basis of naming primarily when the shapes were intentional (and thus plausibly representations). The findings supported the predictions, for both children and adults. These results suggest that, although shape does play an important role in children's early naming, other factors are also important, including the mental state of the picture's creator (intentional vs. not). Thus, the data suggest that from an early age, children's picture naming incorporates their theory of mind.

The role of covariation versus mechanism information in causal attribution.

Traditional approaches to causal attribution propose that information about covariation of factors is used to identify causes of events. In contrast, we present a series of studies showing that people seek out and prefer information about causal mechanisms rather than information about covariation. Experiments 1, 2 and 3 asked subjects to indicate the kind of information they would need for causal attribution. The subjects tended to seek out information that would provide evidence for or against hypotheses about underlying mechanisms. When asked to provide causes, the subjects' descriptions were also based on causal mechanisms. In Experiment 4, subjects received pieces of conflicting evidence matching in covariation values but differing in whether the evidence included some statement of a mechanism. The influence of evidence was significantly stronger when it included mechanism information. We conclude that people do not treat the task of causal attribution as one of identifying a novel causal relationship between arbitrary factors by relying solely on covariation information. Rather, people attempt to seek out causal mechanisms in developing a causal explanation for a specific event.

Causal status effect in children's categorization.

The current study examined the causal status effect (weighing cause features more than effect features in categorization) in children. Adults (Study 1) and 7-9-year-old children (Study 2) learned descriptions of novel animals, in which one feature caused two other features. When asked to determine which transfer item was more likely to be an example of the animal they had learned, both adults and children preferred an animal with a cause feature and an effect feature rather than an animal with two effect features. This study is the first direct demonstration of the causal status effect in children.

Inferior and superior vena caval blood flows during cross-clamping of the thoracic aorta in pigs.

Changes in blood flow through the inferior and superior venae cavae during cross-clamping of the thoracic aorta just above the diaphragm were studied in 28 miniature pigs anesthetized with enflurane titrated to maintain systemic arterial blood pressure close to normal values. Surgical preparation included sternotomy with subsequent placement of a noncannulating electromagnetic probe around the ascending aorta and a cannulating electromagnetic probe in the transected inferior vena cava. Superior vena caval flow was calculated as the difference between aortic flow and inferior vena caval flow. Clamping of the thoracic aorta alone (n = 10) was accompanied by severe arterial hypertension, a dramatic decrease in inferior vena caval flow, and an increase in superior vena caval flow, which resulted in a moderate increase in aortic flow. Simultaneous clamping of the thoracic aorta and inferior vena cava (n = 13) was accompanied by no significant change in arterial pressure or superior vena caval flow. The oxygen content in mixed venous blood significantly (p less than 0.05) increased from 9.5 +/- 1.1 to 13.4 +/- 1.8 ml.dl-1 in animals undergoing clamping of the thoracic aorta only, but did not change significantly in animals subjected to simultaneous clamping of the aorta and inferior vena cava. The study demonstrates a substantial increase in superior vena caval flow during cross-clamping of the thoracic aorta. Further studies elucidating the mechanism of the observed changes are required.

Effects of crossclamping the descending aorta on the high-energy phosphates of myocardium and skeletal muscle. A phosphorus 31-nuclear magnetic resonance study.

The study was designed to test the hypothesis that a moderate decrease in upper body oxygen consumption observed during crossclamping of the thoracic aorta represents tissue hypoxia (possibly as a result of microcirculatory disorders) and results in adenosine triphosphate homeostasis disturbances. We averaged phosphorus 31-nuclear magnetic resonance spectroscopy measurements for 10 minutes with the use of a surface coil on the left ventricle and on the deltoid muscle during a 1-hour period before aortic crossclamping, during aortic crossclamping, and after aortic unclamping. Skeletal muscle creatine phosphate levels decreased 3.1% (p < 0.01), whereas the ratio of creatine phosphate to adenosine triphosphate decreased 2.2% (p < 0.05); glycolytic intermediates increased 70% (p < 0.01) and intracellular inorganic phosphate decreased 9% (p < 0.01). Myocardial creatine phosphate decreased 15% (p < 0.01), whereas the ratio of creatine phosphate to adenosine triphosphate decreased 5.3% (p < 0.01); glycolytic intermediates did not change, but intracellular inorganic phosphate almost doubled (p < 0.05). These data suggest that observations of reduced upper body oxygen consumption after aortic crossclamping are consistent with the effects of skeletal muscle hypoxia. Changes in myocardial metabolites may result from transient ischemia caused by the increased wall stress.

Hemodynamics and oxygen uptake below and above aortic occlusion during crossclamping of the thoracic aorta and sodium nitroprusside infusion.

The effects of controlled vasodilation on blood flow and oxygen consumption above and below the aortic occlusion during crossclamping of the thoracic aorta were examined in 16 mongrel dogs anesthetized with halothane. Blood flow in the inferior vena cava was measured with an electromagnetic cannulating flow probe, and cardiac output was measured by thermodilution. The animals were divided into two groups. In the control group the thoracic aorta was crossclamped at the diaphragmatic level for 30 minutes. In the sodium nitroprusside group the aorta was also crossclamped for 30 minutes, but an infusion of sodium nitroprusside was initiated after 10 minutes of occlusion to decrease systemic blood pressure. Measurements were made before and at 10, 20, and 30 minutes after aortic crossclamping, and at 10 minutes after aortic unclamping. Crossclamping of the thoracic aorta was associated with marked decreases in blood flow and oxygen consumption in organs and tissues below the aortic occlusion in both groups. Above the occlusion, blood flow increased but oxygen uptake decreased. Sodium nitroprusside increased cardiac output and blood flow above the aortic occlusion even more than crossclamping alone while it decreased blood flow and oxygen consumption below the crossclamp.

Xanthine oxidoreductase release after descending thoracic aorta occlusion and reperfusion in rabbits.

Cardiopulmonary and other organ dysfunction often occurs after operation on the descending thoracic aorta. Though there are multiple causes of organ dysfunction in this setting, free radical injury may play a prominent role. Xanthine oxidoreductase, an enzyme that generates oxidants after exposure to ischemia, could be released from ischemic liver and intestine during reperfusion. To test this hypothesis, we created aortic occlusion in eight rabbits for 40 minutes by inflation of a 4F Fogarty balloon catheter in the descending thoracic aorta. Eight sham-operated rabbits served as a control group. Two hours of reperfusion followed removal of the balloon catheter. Hemodynamic and acid-base status were maintained near baseline values during reperfusion. Plasma samples were obtained for determination of the activity of the hepatocellular enzymes xanthine oxidoreductase, aspartate aminotransferase, alanine transferase, and lactate dehydrogenase. Plasma xanthine oxidoreductase activity increased significantly (p < 0.001) during reperfusion (729 +/- 140 microU/ml, mean +/- standard error of the mean) compared with baseline (132 +/- 18 microM/mL). The other enzymes followed a similar pattern of release. We report the release of xanthine oxidoreductase in an animal model that simulates the situation of human thoracic aorta operations. The oxidants produced by the circulating xanthine oxidoreductase observed during reperfusion would likely be toxic to vascular endothelium, potentially contributing to multiple organ dysfunction.

Regional blood flow during cross-clamping of the thoracic aorta and infusion of sodium nitroprusside.

Labeled microspheres, 15 microns in diameter, were used to determine cardiac output and regional blood flow response to cross-clamping of the midthoracic aorta and subsequent sodium nitroprusside (SNP) infusion in 11 dogs. During aortic cross-clamping, mean arterial pressure above the occlusion (MAPa) increased 30% to 35%, mean arterial pressure below the occlusion (MAPb) decreased 87%, cardiac index decreased 12% to 14%, left atrial pressure (LAP) doubled, and renal and spinal cord (lower part) blood flows decreased substantially (85% to 94%). SNP infusion returned MAPa to baseline values, decreased MAPb by half, and substantially and further decreased renal blood flow (to 3% to 5% of baseline values). Myocardial and cerebral blood flows increased substantially (up to 250% to 400%). An increase in preload (fluid load) was accompanied by an increase in LAP, cardiac index, and myocardial blood flow only but not in renal or spinal cord flow. There was a strong association between cortical renal blood flow and MAPb (r2 = 0.92; p less than 0.0001), which suggests that blood flow through organs and tissues below the occlusion is pressure dependent. The data show that SNP infusion during thoracic aortic cross-clamping improves systemic and regional circulation above the occlusion but decreases MAPb and therefore blood flow below the occlusion. SNP infusion should be used with caution during aortic cross-clamping, since arterial hypotension of any degree may be deleterious to organs below the cross-clamp.

Correlation of cerebral blood flow and EEG during carotid occlusion for endarterectomy (without shunting) and neurologic outcome.

One hundred twenty-nine consecutive carotid endarterectomies performed for atherosclerotic ulcerative stenosis without the use of intraoperative shunting were analyzed prospectively in an effort to determine the significance of intraoperative ischemia. Intraoperative EEG and regional cerebral blood flow measurements were used to monitor these patients. Ten of the patients were excluded because of inadequate data, but none of these 10 patients experienced a complication. Factors analyzed included preoperative risk assessment according to the Mayo Clinic system of Sundt et al., intraoperative regional cerebral blood flow measurements, and intraoperative EEG changes. The overall mortality rate was 2.5%, the major morbidity rate was 2.5%, the minor morbidity rate was 1.7%, and the rate of transient neurologic dysfunction was 1.7%. The patients' preoperative state as determined according to the Mayo Clinic system of Sundt et al. was more useful in identifying patients at risk than was intraoperative EEG and regional cerebral blood flow monitoring.

Cardiac output distribution and regional blood flow during hypocarbia in monkeys.

Cardiac output distribution and regional blood flow were studied during hypocarbia independent of changes in ventilatory parameters. Fifteen cynomolgus monkeys were anesthetized with methohexital sodium (8 mg/kg im) and hyperventilated through an endotracheal tube. Hypocarbia at two levels, 28 +/- 1.8 and 17 +/- 0.6 Torr, was achieved by a stepwise decreasing CO2 flow into the semiclosed system. Regional blood flow was determined with labeled microspheres. At each stage of experiments two sets of microspheres (9 and 15 microns diam) were used simultaneously. The use of two microsphere sizes allowed evaluation of the relationship between total (nutritive and nonnutritive) tissue blood flow, determined with 15-microns spheres, and nutritive blood flow, determined with 9-microns spheres. There was no change in cardiac output or arterial pressure during both degrees of studied hypocarbia. Hypocarbia was accompanied by a decrease in myocardial blood flow determined with 15-microns spheres and preservation of the flow determined with 9-microns spheres. Splenic blood flow was decreased, whereas hepatic arterial blood flow was increased during both levels of hypocarbia. Blood flow through the brain, renal cortex, and gut showed a biphasic response to hypocarbia: during hypocarbia at 28 +/- 1.8 Torr, blood flow determined with 15-microns spheres was unchanged (in the gut) or decreased (in the brain and kidneys), whereas blood flow determined with 9-microns spheres was decreased. During hypocarbia at 17 +/- 0.6 Torr, blood flow determined with 9-microns spheres had a tendency to restore to base-line values.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of ultrasonography in the management of endometritis/salpingitis/peritonitis.

Ultrasonography has been used as an adjunct in managing pelvic infections when culdocentesis is contraindicated. Twenty-three of 42 women presenting with endometritis/salpingitis/peritonitis (ESP) had ultrasonographic masses. The erythrocyte sedimentation rate (ESR), white blood cell count (WBC), and the highest temperature in the first 24 hours failed to distinguish those with sonographic masses from 19 patients without pelvic masses. The clinical parameter that tended to distinguish patients with masses versus no masses occurred in individuals who had an IUD at the time of admission. If a patient had an ESR greater than 65 mm/hr and an IUD, sonography demonstrated a mass in 71.4% of the cases. The clinical response to multidrug therapy (bactericidal-bacteriostatic, bactericidal-bactericidal, and triple-drug therapy) were comparable in the patient populations with or without a sonographic mass. Sonography is of little use in the acute phase of ESP. It is best reserved for those patients who do not respond to adequate antibiotic therapy and for the serial evaluation of a large tubo-ovarian complex when conservative management is indicated.

Fetal movements and placental lactogen levels for fetal-placental evaluation. A preliminary report.

Fetal movements were measured by 37 pregnant women during a 10-minute period while they were lying on their left side at various times during the day with the highest rates in the evening. Preliminary assessments of fetal movement and serum hPL levels in pregnant women suggest that the two tests might complement each other in providing more information about the status of the placenta and fetus.

Comparison of fetal maturity evaluation with ultrasonic biparietal diameter and amniotic fluid lecithin-sphingomyelin ratio.

Fetal head biparietal (BP) measurements by ultrasonic techniques and amniotic fluid lecithin-sphingomyelin (L/S) ratios were simultaneously determined (within 2 days) on 84 occasions in 72 women. Using the criteria for maturity of an L/S ratio of 2.0 or more or a BP measurement of 9.0 cm or more, there was agreement between these test results in 66.7% of the cases. The BP incorrectly predicted the L/S ratio 33.3% of the time, with a false positive rate of 27.3% and a false negative rate of 6.0%. If an L/S ratio of 1.5 were used as the critical determinant, the BP false positive rate remained high (9.5%). A high false negative error (21.4%) occurred if a BP value of 9.3 cm was used. These results suggest that ultrasonic BP measurements should not be used as the only criteria of fetal maturity in the management of high-risk pregnancies.