Postural hypotension in late pregnancy. "The supine hypotensive syndrome"

Impact of Prone Jackknife Position on Intraoperative Hypotension During Percutaneous Nephroscopy: A Retrospective Matched Analysis

Objective

To investigate the potential relationship between the prone jackknife position during percutaneous nephroscopy and the occurrence of intraoperative hypotension.

Methods

A retrospective analysis was conducted on 651 patients who underwent percutaneous nephroscopy at the Second Affiliated Hospital of Hainan Medical University. The primary focus was to investigate the occurrence of hypotension during the surgical procedure and assess the duration of hypotensive episodes. Patients were categorized into the prone jackknife position group and the lateral position group. To compare the incidence of intraoperative hypotension between the two groups, a 1:1 propensity match was performed. Following the matching process, intraoperative hypotension was assessed and compared between the two groups before and after the match. The binary logistic regression analysis determined the probability of intraoperative hypotension occurred in each group. Furthermore, linear regression analysis was used to analyze the duration of hypotensive episodes experienced by patients in both groups.

Results

After propensity score matching, a total of 272 patients with similar characteristics were obtained (136 in each group). The prone jackknife group had a significantly higher incidence of intraoperative hypotension than the lateral group after the match, with an odds ratio of 2.71 (95% confidence interval: 1.595-4.605). Binary logistic regression analysis showed that age and body position exhibited statistical significance as risk factors. Linear regression analysis before and after the match indicated that the duration of hypotension was associated with age, surgical time, and a history of hypertension.

Conclusion

The prone jackknife position syndrome after general anesthesia could occur in surgeries. The position could contribute to the development of hypotension during the percutaneous nephroscopy procedure.

Rehabilitation of anterior knee pain in the pregnant athlete: Considerations and modifications by trimester

BACKGROUND

Anterior knee pain is a common symptom many females experience during pregnancy. There are several musculoskeletal changes that occur in anatomy and physiology throughout the course of pregnancy that impact the lower extremity kinetic chain. Pregnant athletes, recreational through competitive, who attempt to maintain a high activity level through each trimester may be at increased risk for anterior knee pain due to a greater demand for lumbopelvic and hip stabilization.

CLINICAL QUESTION

What are the evidence-driven rehabilitation guidelines and specific modifications needed to treat anterior knee pain in the female athlete during each trimester of pregnancy?

KEY RESULTS

We aim to provide an overview of rehabilitation treatment guidelines for pregnant females with anterior knee pain, presenting specific physiological changes and rationale for modifications, discussed by trimester. We recommend our program be conducted under the supervision of a physical therapist working closely with the athlete's obstetrics and sports medicine team.

CLINICAL APPLICATION

The number of women who are active during pregnancy is increasing. We provide an overview of the guidelines and considerations for treating women with anterior knee pain during a healthy and uneventful pregnancy.

The effect of body position on maternal cardiovascular function during sleep and wakefulness in late pregnancy

INTRODUCTION

An association between the increased risk of late stillbirth and the maternal supine sleeping position has been recently established. The risk of stillbirth following supine sleep has been suspected to occur as a result of aortocaval compression by the gravid uterus. A number of studies conducted during wakefulness have reported compromised cardiovascular function during supine rest, as demonstrated by reductions in cardiac output, blood pressure and utero-placental blood flow. It remains unclear whether similar effects are also present during sleep, due to the presence of key sleep-specific changes in cardiovascular function.

OBJECTIVE

To investigate the changes in maternal cardiovascular function between the supine and left-lateral positions during wakefulness and non-rapid eye movement (NREM) sleep in late pregnancy.

METHODS

Twenty-nine women with a singleton pregnancy between 24.7 and 36.7 weeks' gestation participated in a single overnight sleep study. Physiological measures (blood pressure, heart rate, heart rate variability - HRV, and pulse arrival time - PAT) were measured and recorded throughout the night using standard polysomnography equipment and the Portapres Model-2 device. As the present study evaluated cardiovascular changes during natural rest and sleep in pregnancy, participants were not given explicit instructions on which position to adopt. Body position was continuously recorded using a position monitor and verified with video recording.

RESULTS

No changes in systolic, diastolic or mean arterial blood pressure were observed between the left-lateral and supine positions during wakefulness or sleep. However, heart rate was significantly higher in the supine position compared to the left during wakefulness (p= .03), with a similar trend present during sleep (p= .11). A significantly shorter PAT was measured in the supine position (compared to the left) during wakefulness (p= .01) and sleep (p= .01). No change in HRV measures was observed between the left and supine positions in either state.

CONCLUSION

Blood pressure did not appear to differ significantly between the left-lateral and supine positions during wakefulness and sleep. The lack of blood pressure differences may reflect elevated sympathetic activity during rest and sleep in the supine position (compared to the left), suggesting that some degree of compensation for aortocaval compression may still be possible during sleep.

Awareness and Aortocaval Obstruction in Obstetric Anesthesia

Awareness during general anesthesia for cesarean delivery continues to be a major problem. The key to preventing awareness is strict attention to anesthetic technique. The prevalence and implications of aortocaval compression have been firmly established. Compression of the vena cava is a real occurrence when assuming the supine position. Relief of this compression most likely does not occur until the patient is turned 30°, which is not feasible for performing cesarean delivery. Although it is still wise to tilt the patient, the benefit of this tilt may not be as great as once thought.

Comparison of the Effect of Maternal Rest in Alternative Lateral Decubitus Positions on the Amniotic Fluid Index: A Randomized Controlled Trial

OBJECTIVES

To analyze the effect of maternal rest in the left and right lateral decubitus positions and resting alone on the amniotic fluid index (AFI).

METHOD

Sixty-nine women with singleton pregnancies and an AFI of 6 to 24 cm at 36 to 40 weeks' gestation were included in this randomized controlled trial. The women were randomized into 2 intervention groups. After initial AFI measurements, group 1 (n = 35) rested in the left lateral position for 15 minutes and then rested in the right lateral position for another 15 minutes. Group 2 (n = 34) rested in the right lateral position for 15 minutes and then rested in the left lateral position for another 15 minutes. To compare differences between groups, AFIs were measured at the end of each 15-minute period while the participants were kept on their backs in a semirecumbent position.

RESULTS

The demographic data, gestational ages, and initial AFI values did not differ between groups (P > .05). In group 1, the initial mean AFI ± SD of 12.25 ± 3.81 increased significantly during the first 15 minutes to 15.17 ± 4.27 and decreased significantly during the second 15 minutes to 13.30 ± 4.29 (P< .001); however, the 30-minute AFI was still significantly higher than the initial value (P = .008). In group 2, the initial AFI change during the first 15 minutes, from 12.83 ± 3.99 to 12.72 ± 3.87, was not significant (P> .05); however, it increased significantly to 15.63 ± 4.14 during the second 15 minutes (P< .001). The 30-minute AFI was still significantly higher than the initial value (P< .001).

CONCLUSIONS

Maternal rest in the right lateral decubitus position does not seem to either increase or decrease the AFI, and resting alone does not increase the AFI in the short term.

Hemodynamic changes and baroreflex gain in the supine hypotensive syndrome

OBJECTIVE

The purpose of this study was to determine whether supine hypotensive syndrome is caused by a decreased baroreflex gain that results in inadequate compensatory responses to restore cardiac output.

STUDY DESIGN

Ten third-trimester gravid women with symptoms that were suggestive of supine hypotensive syndrome and 10 control subjects without symptoms were studied. Patients were studied initially for 30 minutes in the lateral recumbent position with continuous heart rate, blood pressure, external cardiotocography, and cardiac output determinations every 5 minutes. After 30 minutes, the patient was repositioned supine for up to an additional 30 minutes, and all measurements were repeated similarly. This lateral-supine sequence was repeated twice or until symptoms precluded further testing.

RESULTS

The two groups were demographically similar. With maternal position change to supine, cardiac output (-2.7 L/min vs -1.0 L/min, P =.04) and mean arterial blood pressure (-10.7 mm Hg vs -2.5 mm Hg, P =.03) were respectively lower, and heart rate (+26.9 vs +14.4 beats/min, P =.04) was higher in the subjects with supine hypotensive syndrome than in the control subjects. Baroreflex gain, however, did not differ between the subjects with supine hypotensive syndrome and control subjects (P =.26).

CONCLUSION

We were unable to demonstrate a decrease in baroreflex gain as a possible cause of supine hypotensive syndrome. Inadequate pelvic collateral circulation that leads to a greater decrease in cardiac output may be causative in the syndrome.

Semi-Fowler's positioning, lateral tilts, and their effects on nonstress tests

OBJECTIVE

To determine whether a lateral tilt for women in semi-Fowler's position for antepartum nonstress tests (NSTs) (a) promotes NST reactivity or (b) shortens testing time required to obtain a reactive tracing.

SETTING

An antepartum fetal assessment unit of a tertiary care facility in eastern Canada.

DESIGN

In this prospective, randomized study, a computer analysis of the NSTs was used to obtain an objective, standardized interpretation of fetal heart rate reactivity. Participants were randomly assigned to two experimental groups using semi-Fowler's position with a 45-degree tilt to either the left or right, or to a control group using semi-Fowler's position with no lateral tilt.

PARTICIPANTS

A convenience sample of 823 nonstress tests was obtained from women with singleton pregnancies, intact amniotic membranes, and gestations between 32 and 42 weeks. The final sample available for analysis totaled 738 nonstress tests from 573 pregnancies.

MAIN OUTCOME MEASURES

Percentage of reactive nonstress tests and the number of minutes required for tests to be reactive.

RESULTS

The rate of reactive NSTs and the time to achieve a reactive NST did not differ statistically for any of the three study groups. Likewise, NST outcomes were similar when the left-tilt group was compared with the right-tilt group. Although no significant differences were found between study groups, less than 2% of the women in the control group (semi-Fowler's position without a lateral tilt) experienced symptoms consistent with supine hypotensive syndrome.

CONCLUSIONS

No statistically or clinically significant differences were found in nonstress tests between the three groups. Lateral tilting did not shorten test time. Results do suggest that hemodynamic changes can occur in 3rd trimester women who are in semi-Fowler's position without a lateral tilt. Lateral tilting of gravidas in semi-Fowler's position during nonstress testing is thus supported to avoid hypotensive symptoms.