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.

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.

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 After anaesthesia induction, blood was withdrawn in steps of 2% of estimated circulating blood volume (ECBV).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.

Developmental changes in the ultrastructure of the lamprey lateral line nerve during metamorphosis.

The ultrastructure of the trunk lateral line nerve of larval and adult lampreys was studied with transmission electron microscopy. We confirmed that lampreys' lateral line nerve lacks myelin. Nevertheless, all axons were wrapped by Schwann cell processes. In the larval nerve, gaps between Schwann cells were observed, where the axolemma was covered only by a basal lamina, indicating an earlier developmental stage. In the adult nerve, glial (Schwann cell) ensheathment was mostly complete. Additionally, we observed variable ratios of axons to Schwann cells in larval and adult preparations. In the larval nerve, smaller axons were wrapped by one Schwann cell. Occasionally, a single Schwann cell surrounded two axons. Larger axons were associated with two to five Schwann cells. In the adult nerve, smaller axons were surrounded by one, but larger axons by three to eight Schwann cells. The larval epineurium contained large adipose cells, separated from each other by single fibroblast processes. This layer of adipose tissue was reduced in adult preparation. The larval perineurium was thin, and the fibroblasts, containing large amounts of glycogen granules, were arranged loosely. The adult perineurium was thicker, consisting of at least three layers of fibroblasts separated by collagen fibrils. The larval and adult endoneurium contained collagen fibrils oriented orthogonally to each other. Both larval and adult lateral line nerves possessed a number of putative fascicles weakly defined by a thin layer of perineurial fibroblasts. These results indicate that after a prolonged larval stage, the lamprey lateral line nerve is subjected to additional maturation processes during metamorphosis.

Metamorphosis-related changes in the lateral line system of lampreys, Petromyzon marinus.

Lamprey metamorphosis leads to considerable changes in morphology and behavior. We have recently reported that larval lampreys possess a functional lateral line system. Here we investigated metamorphic morphological changes in the lateral line system using light and electron microscopy. Functional modifications were studied by recording the trunk lateral line nerve activity of larvae and adults while stimulating neuromasts with approximately sinusoidal water motion. We found a general re-patterning of neuromasts on the head and trunk including an increase in numbers, redistribution within the pit lines, and shifts of the pit lines relative to external features. The trunk lateral line nerve response was qualitatively similar in adults and larvae. Both showed two neuronal populations responding to opposite directions of water flow. Magnitude of the response increased monotonically with stimulus amplitude. At low frequencies, the response lag relative to the stimulus maximum was approximately 220 degrees , and the gain depended approximately linearly on frequency, confirming that superficial neuromasts are velocity detectors. Changes in phase lag with increasing stimulus frequency were steeper in larvae, suggesting slower afferent conductance. The response gain with frequency was smaller for adults, suggesting a narrower frequency discrimination range and decreased sensitivity. These changes may be adaptations for the active lifestyle of adult lampreys.

Larval lampreys possess a functional lateral line system.

Morphology of larval lampreys' neuromasts was found to be very similar to that of adults. Activity in the lateral line nerve, elicited by a vibrating ball, indicated a functional lateralis system. Analysis revealed at least two populations of afferents, responding to opposite directions of water flow, with adapting responses. The response magnitude increased monotonically with stimulus amplitude. Larval lampreys' neuromasts were less sensitive than those of teleosts. At low frequencies the response showed a phase lead of 200-220 degrees with respect to the maximum of the ball displacement and a gain that was approximately linearly proportional to frequency.

Children's and adults' models for predicting teleological action: the development of a biology-based model.

Understanding that only living things must act to gain self-beneficial goals is important for developing a theory-like understanding of the living world. This research studied the models that preschoolers, fifth graders, and adults use to guide their predictions of self-beneficial, goal-directed (i.e., teleological) action. Four possible models have been suggested: finalist, complexity based, biology based, and animal based. In Study 1, participants (N = 104) were assigned to one of two conditions that differed in whether a beneficial or neutral object was pictured; they were asked to predict whether animals, plants, machines, and simple artifacts would modify their movement in the direction of that object. Preschoolers' predictions were consistent with an animal-based model, fifth graders' predictions were consistent with biology-based and complexity-based models, and adults' predictions were consistent with a biology-based model. Analysis of both individual response patterns and explanations supported these findings, but also showed that a significant number of preschoolers and fifth graders were finalist, and that very few individual fifth graders followed a complexity-based teleology. In Study 2, participants (N = 84) reported whether the animals, plants, machines, and simple artifacts in Study 1 had psychological capacities. All age groups attributed psychological capacities to animals at levels higher than other domains and at above-chance levels. The evidence from these two studies suggests that preschoolers, unlike fifth graders and adults, predict teleological action for plants and animals on the basis of these entities' inferred psychological capacities.

Children's understanding of psychogenic bodily reactions.

One hundred twenty-eight children in preschool through fifth grade (range = 4,3-11,4) and 76 adults serving as a comparison group participated in two studies that examined how children reason about psychogenic bodily reactions, that is, ailments or nonconscious physiological responses with origins in the mind (e.g., stress-induced headache). Psychogenic bodily reactions provide an opportunity to study how children integrate knowledge between the domains of bodily response and psychology. In Study 1, participants were asked whether various familiar psychogenic bodily reactions were possible (e.g., can someone get a tummyache from worrying?). In Study 2, participants were presented with a novel domain (hypothetical "aliens" from outer space) and were asked whether various unfamiliar bodily conditions (e.g., toes swelling) could arise from various physical or psychological causes. As predicted, adults typically reported that psychogenic bodily reactions were possible, and that unfamiliar bodily conditions could result from either psychological or physical causes. In contrast, young children typically denied that psychogenic bodily reactions could occur and predicted that unfamiliar bodily conditions resulted from physical causes only. The results support a developmental path: younger children view psychogenic bodily responses as wholly physical, but with age, view them as both physical and psychological phenomena.

Prospective double-blind study of effect of ketorolac administration after laparoscopic urologic surgery.

BACKGROUND AND PURPOSE: To decrease postoperative dependence on narcotics for analgesia, we have evaluated ketorolac as an adjunct to perioperative pain control in patients undergoing laparoscopic urologic surgery. PATIENTS AND METHODS: Sixty-five patients (34 male, 31 female) were randomized to receive either ketorolac tromethamine (15-30 mg IV q 6 h) or placebo prior to laparoscopic surgery. Patient-controlled analgesia in the form of morphine sulfate was provided. Operative factors such as the type of surgery, operative time, and estimated blood loss were recorded. Postoperative factors such as analog pain score (range 0-10), narcotic usage, and length of stay were evaluated. RESULTS: Fifty-five patients completed the study. The average pain score was 2.2 and 4.5 for the ketorolac and placebo groups, respectively (P < 0.005). The mean amounts of total morphine used were 39.2 mg (ketorolac) and 62.5 mg (placebo) (P = 0.077). The length of stay was not significantly different in the ketorolac (2.5 days) and placebo (2.6 days) groups (P = 0.74). Operative times (P = 0.21) and estimated blood loss (P = 0.60) were not significantly different in the two groups. Ketorolac did not adversely affect renal function; serum creatinine changes were not significantly different from those in the patients receiving placebo (P = 0.50). Laparoscopic pyeloplasty necessitated more narcotic analgesia than did other laparoscopic procedures (P = 0.05). CONCLUSION: Ketorolac decreases the subjective perception of pain after laparoscopic urologic surgery. It is suggested that ketorolac administration decreases the amount of narcotic usage as well. Time to resumption of oral intake and length of hospital stay were not influenced by use of ketorolac.

The role of animacy in children's understanding of 'move'.

Animals are distinctive in that they are the causal agents of their own actions (e.g. a dog moves itself), whereas artifacts generally are not (e.g. a marble doesn't move itself). We examined whether children make use of this conceptual link between animacy and agency when interpreting the verb 'move' in English. Specifically, we hypothesized that the semantic interpretation of 'move' would differ, depending on whether the subject noun refers to an animal or to an inanimate object. We hypothesized that, for in animates, children would allow 'move' to have a patient subject (e.g. 'the marble moved' could mean 'the marble was moved by someone else') but not so for animates (e.g. 'the dog moved' could not mean 'the dog was moved by someone else'). In two studies, 65 three-year-olds, 57 five-year-olds, and 74 adults viewed video clips of animals or inanimate objects being transported by a person. For each clip, the child was asked whether the animal or object was moving. A 'yes' response would indicate acceptance of a patient subject (e.g. 'the dog/marble moved' means 'the dog/marble was moved by someone else'). Both five-year-old children and adults more often reported that the toys were moving, than that the animals were moving. However, three-year-olds showed no animacy effects. Thus, between the ages of three and five, children begin to link animacy and agency in language. These findings suggest that children's language use is guided by similar conceptual constraints as those of adults, and/or that children are sensitive to distributional information linking form and meaning in the input language.

Preschool children's use of trait labels to make inductive inferences.

One hundred one preschool children (ages 3 years 5 months to 4 years 10 months) participated in 3 studies examining the tendency to use verbal labels versus appearance information in making novel inductive inferences. A triad task analogous to that of S. A. Gelman and E. M. Markman (1986) was devised. Participants learned a different property for each of 2 children, and were asked which of the properties was true of a third child. One of the first 2 children was identified with the same label as the third child (e.g., both were labeled as shy) but looked different, and the other was identified with a different label than the third child but looked very similar. Results of Study 1 revealed that participants tended to use the trait labels, rather than superficial resemblance, in making psychological inferences. Studies 2 and 3 suggest that these results cannot be attributed to biases on the task. Study 4 provided a replication of the results of Study 1 in a context in which appearance information was explicitly pointed out and in which different trait labels were used.

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.

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.