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To determine the effect of snugness of cuff wrap on the accuracy of blood pressure (BP) measurements, we performed two studies on 6 healthy volunteers. In both studies, control values were obtained from the right upper arm with cuffs of appropriate size and snug fit. Study 1 had two phases. In the first, cuffs of appropriate size were wrapped snugly around the upper left arm of seated subjects. The effects of two other degrees of cuff snugness on the measurement of BP were evaluated by placing a filled 250-mL intravenous fluid bag between the cuff and arm over the triceps, measuring BP, then draining the same bag of half its contents and then all of its contents without rewrapping the cuff ("loose," "very loose" fit), each time measuring BP. The second phase of study 1 was identical in procedure, except that the cuffs used on the left arm were one size too small. In study 2, the experimental cuffs were placed just above the right ankle. To alter the signal-to-noise ratio, BP was raised or lowered: the standing position elevated mean BP by an average of 90 mm Hg, and elevation of the legs decreased mean BP by an average of 43 mm Hg. In study 1, we found that appropriately sized cuffs, whether wrapped tightly or loosely, gave correct BP readings. Cuffs snugly wrapped, but too small for the subject, gave high BP readings, on the average by approximately 10 mm Hg. Loose wrapping of small cuffs gave variable results in individual subjects that exaggerated systolic BP from 2 to 80 mm Hg. In study 2, elevating the legs or standing decreased or increased BP consistently. Loose wrapping of appropriately sized cuffs around the ankles of the subjects had no additional significant effect on BP.

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Airway pressure release ventilation is a recently described method of ventilatory support. It allows spontaneous ventilation with CPAP but differs from conventional ventilatory modes because, with APRV, peak inflation pressure never exceeds the level of CPAP, and airway pressure decreases, rather than increases, when tidal volume is delivered. The risk of pulmonary barotrauma and adverse hemodynamic effects associated with conventional modes of positive-pressure mechanical ventilation may be decreased because of lower peak inflation and mean airway pressures. We describe a patient in whom several risk factors for these complications were present who was treated successfully with APRV.

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Cardiac output during cesarean section and for 24 hours after delivery was estimated by using a noninvasive ultrasonic Doppler technique and was compared between term pregnant patients who underwent either epidural or general anesthesia. Cardiac output peaked by 36.7% and 26.3% of baseline values at 15 and 30 minutes after delivery, respectively, with epidural anesthesia and by 28% and 17.2%, respectively, with general anesthesia. From 60 minutes to 24 hours after delivery, cardiac output in both groups remained elevated at preoperative levels. This study demonstrates a similar pattern of increase in cardiac output with epidural and general anesthesia and a return by 60 minutes to preoperative levels, which persisted for up to 24 hours after delivery. The applicability of this noninvasive technique can be extended in various circumstances during pregnancy, labor, delivery, and the postpartum period to further define cardiac output in pregnancy.

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Maternal cardiac output changes were evaluated in 10 patients undergoing second-trimester abortion induced by prostaglandin E2 suppositories. The peak cardiac output increased by an average of 64.5% above preinduction values. This is similar to the percent increase described during oxytocin-induced labor at term. Inasmuch as resting cardiac output tends to be higher in midpregnancy than at term, absolute values during prostaglandin E2 induction were higher than those observed in laboring term patients.

PIP: Maternal cardiac output changes were evaluated in 10 patients undergoing 2nd trimester abortion induced by prostaglandin E2 suppositories. The peak cardiac output increased by an average of 64.5% above preinduction values. This is similar to the % increase described during oxytocin-induced labor term. Inasmuch as resting cardiac output tends to be higher in midpregnancy than at term, absolute values during prostaglandin E2 induction were higher than those observed in laboring term patients. Although the mean cardiac output increase was less among patients undergoing pregnancy termination for fetal death in utero versus viable fetus, statistical significance was not reached. Whether other methods used to induce labor for 2nd trimester abortion cause similar increases in cardiac output is unknown. With patients known or suspected to have cardiovascular disease, the increase of cardiac output that occurs during induction of labor for 2nd trimester abortion should be considered. Surgical dilatation and evacuation is an alternative, since this method may impose less cardiovascular alterations.

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Thirty-six pregnant women (ASA class I or II) at term who underwent general anesthesia and cesarean section received either ketamine, 1 mg/kg (n = 12); thiopental, 4 mg/kg (n = 13); or a combination of ketamine, 0.5 mg/kg, and thiopental, 2 mg/kg (n = 11). A blood pressure cuff inflated to 250 mm Hg isolated one arm from the effects of succinylcholine so that awareness during anesthesia could be assessed by asking the patient to move her hand. Although only one patient receiving ketamine responded to commands during anesthesia, 46% of patients receiving either thiopental or the combination responded to commands intraoperatively. No patient hallucinated, the incidence of dreams was low (11%), and no postoperative dysphoria was noted. Three patients (8%) had postoperative recall of intraoperative awareness; one had received thiopental and two the combination. Maternal intraoperative cardiovascular responses among the groups were similar, as were umbilical blood gas values, newborn Apgar scores, and neonatal neurobehavioral test scores at 4 and 24 hr. Ketamine more effectively blocked maternal responsiveness to commands and strong stimuli during the first few minutes after anesthetic induction for cesarean section than did thiopental or a combination of thiopental and ketamine, each at a lower dose.

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A variety of frequencies and percent inspiratory times (%TI) may be used for high-frequency jet ventilation (HFJV). Five physiologic criteria were used to evaluate various combinations of frequency and %TI: mean airway pressure (Paw), cardiac output, PaCO2, PaO2, and intrapulmonary shunt (Qsp/Qt). At a constant drive pressure, the effects of frequencies of 100, 200, 300, 450, 600, 750, and 900 cycle/min at %TI values of 20%, 30%, and 40% of the respiratory cycle were evaluated and compared with the effects of controlled mechanical ventilation (CMV) at 8 to 12 breath/min. Only at 200 cycle/min and 20% TI, were Paw, cardiac output, PaCO2, PaO2, and Qsp/Qt all the same as the CMV values. At 100 cycle/min and 20% TI, CO2 elimination increased without significantly affecting Paw, cardiac output, PaO2, or Qsp/Qt. These data suggest that HFJV might compromise one or more physiologic variables at certain combinations of frequency and %TI. Therefore, at a fixed drive pressure, there appears to be a narrow range of HFJV ventilator settings that should be considered.

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Many considerations resulting in the formulations of guidelines for the use of intravascular catheters in the care of critically ill patients are well explored and documented; other areas are highly conjectural, are virtually unchartered, or have not even been explored. The sterility of transducer and flush assembly over time, the use of a five-lumen PA catheter as an avenue for both hemodynamic measurement and nutritional support, and the meaningful interpretation of cultures obtained from all of the catheters are necessary areas of present research to replace theoretical concepts with data. We hope that the necessity for future research will provide data for the ICU practitioner to deliver the safest and most cost-effective methods of intravascular catheterization in a constantly changing environment.

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