The effect of epidural analgesia in labour on maternal respiratory function

Use of a novel non-invasive respiratory monitor to study changes in pulmonary ventilation during labor epidural analgesia

Measuring continuous changes in maternal ventilation during labor neuraxial analgesia is technically difficult. Consequently, the magnitude of pulmonary minute ventilation (MV) alterations following labor analgesia remains unknown. We hypothesized that a novel, bio-impedance based non-invasive respiratory monitor would provide this information. Furthermore, we sought to determine if an association between changes in MV and maternal temperature existed. Following calibration with a Haloscale Standard Wright Respirometer, the ExSpiron respiratory volume monitor (RVM) measured MV, respiratory rate (RR), and tidal volume (TV) in 41 term parturients receiving epidural analgesia. Simultaneously, maternal oral temperatures were recorded at pre-specified hourly intervals after epidural analgesia initiation until delivery. Cumulative MV changes were calculated as the integral of MV change over time: MV [Formula: see text], where T represents the time between epidural placement and variable measurement. The association between changes in MV and cumulative MV versus maternal temperature was determined by comparing patients whose temperature did or did not increase by ≥ 0.5 °C. After initiation of epidural analgesia, MV decreased by 11.1 ± 27.6% [mean ± SD] at 30 min, p = 0.006, and 19.8 ± 26.1% at 2 h compared to baseline (12.6 ± 7.3 L/min at baseline vs. 15.3 ± 6.3 L/min at 2 h, p < 0.001), Minute ventilation remained decreased at 4 h by 14.3 ± 31.4% (p = 0.013). The cumulative MV also decreased by 437 ± 852 L [mean ± SD], p = 0.009) at 2 h and by 795 ± 1431 L, p < 0.001) at 4 h following epidural analgesia initiation, compared to baseline. The association between changes in cumulative MV and maternal temperature following epidural placement was weak (R < 0.3); however, a decrease in MV at 30 min (p = 0.002) and cumulative MV at 2 h (p = 0.012) was observed in women whose temperature increased by at least 0.5 °C during labor. Our findings suggest that RVM can be a useful noninvasive technology to investigate pulmonary physiology during labor. The association between maternal MV and temperature change during labor analgesia deserves further investigation.Trial Registrationwww.clinicaltrials.gov (NCT02339389).

Maternal Body Mass Index and Use of Labor Neuraxial Analgesia: A Population-based Retrospective Cohort Study

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Neuraxial labor analgesia may benefit obese women by optimizing cardiorespiratory function and mitigating complications related to emergency general anesthesia. We hypothesized that obese women have a higher rate of neuraxial analgesia compared with nonobese parturients.

METHODS

Using U.S. natality data, our cohort comprised 17,220,680 deliveries, which accounts for 61.5% of 28 million births in the United States between 2009 and 2015. We examined the relationships between body mass index class and neuraxial labor analgesia, adjusting for sociodemographic, antenatal, pregnancy, and peripartum factors.

RESULTS

The study cohort comprised 17,220,680 women; 0.1% were underweight, 12.7% were normal body mass index, 37% were overweight, and 28.3%, 13.5%, and 8.4% were obesity class I, II, and III, respectively. Rates of neuraxial analgesia by body mass index class were as follows: underweight, 59.7% (9,030/15,128); normal body mass index, 68.1% (1,487,117/2,182,797); overweight, 70.3% (4,476,685/6,368,656); obesity class I, 71.8% (3,503,321/4,881,938); obesity class II, 73.4% (1,710,099/2,330,028); and obesity class III, 75.6% (1,089,668/1,442,133). Compared to women with normal body mass index, the likelihood of receiving neuraxial analgesia was slightly increased for overweight women (adjusted relative risk, 1.02; 95% CI, 1.02 to 1.02), obese class I (adjusted relative risk, 1.04; 95% CI, 1.04 to 1.04), obese class II (adjusted relative risk, 1.05; 95% CI, 1.05 to 1.05), and obese class III (adjusted relative risk, 1.06; 95% CI, 1.06 to 1.06).

CONCLUSIONS

Our findings suggest that the likelihood of receiving neuraxial analgesia is only marginally increased for morbidly obese women compared to women with normal body mass index.

Anesthesia for the morbidly obese parturient

PURPOSE OF REVIEW

Obesity is a growing healthcare problem worldwide, which also affects the pregnant population. Obesity occurs with increasing frequency during pregnancy. Obesity increases the maternal, fetal and neonatal risks. Also, the anesthesiologist is confronted with significantly more problems when the parturient is overweight or obese. The present review focuses on the anesthetic implications of obesity in pregnancy.

RECENT FINDINGS

In recent years, many authors have stressed the consequences of obesity in pregnancy. More pregnancy-associated complications such as preeclampsia occur, and more medical interventions are also required such as operative delivery, when patients are obese compared with the nonobese population. Recent anesthetic evidence also shows that obese parturients are at increased risk of anesthesia-related complications such as failed intubation and aspiration.

SUMMARY

Anesthesia-related complications are more frequent in obese parturients. Most authors and opinion leaders agree that regional anesthesia is the preferred technique for Cesarean section in obese patients, and that efforts to place early labor epidural analgesia should be optimized in order to be able to avoid general anesthesia when unplanned Cesarean section is required.

Comparison between intubation and the laryngeal mask airway in moderately obese adults

BACKGROUND

Obesity is a well-established risk factor for perioperative pulmonary complications. Anaesthetic drugs and the effect of obesity on respiratory mechanics are responsible for these pathophysiological changes, but tracheal intubation with muscle relaxation may also contribute. This study evaluates the influence of airway management, i.e. intubation vs. laryngeal mask airway (LMA), on postoperative lung volumes and arterial oxygen saturation in the early postoperative period.

METHODS

We prospectively studied 134 moderately obese patients (BMI 30) undergoing minor peripheral surgery. They were randomly assigned to orotracheal intubation or LMA during general anaesthesia with mechanical ventilation. Premedication, general anaesthesia and respiratory settings were standardized. While breathing air, we measured arterial oxygen saturation by pulse oximetry. Inspiratory and expiratory lung function was measured preoperatively (baseline) and at 10 min, 0.5, 2 and 24 h after extubation, with the patient supine, in a 30 degrees head-up position. The two groups were compared using repeated-measure analysis of variance (ANOVA) and t-test analysis. Statistical significance was considered to be P<0.05.

RESULTS

Postoperative pulmonary mechanical function was significantly reduced in both groups compared with preoperative values. However, within the first 24 h, lung function tests and oxygen saturation were significantly better in the LMA group (P<0.001; ANOVA).

CONCLUSIONS

In moderately obese patients undergoing minor surgery, use of the LMA may be preferable to orotracheal intubation with respect to postoperative saturation and lung function.

The effect of intrathecal fentanyl added to hyperbaric bupivacaine on maternal respiratory function during Cesarean section

BACKGROUND

Subarachnoid blockade with local anesthetics induces respiratory depression. Although the addition of fentanyl to bupivacaine has become popular in subarachnoid blockade for Cesarean section, there is no information on the effect of intrathecal fentanyl on maternal spirometric respiratory function in parturients undergoing Cesarean section.

METHODS

We tested the effect of the addition of intrathecal fentanyl to hyperbaric bupivacaine on maternal spirometric performance in 40 consenting parturients undergoing Cesarean section. The parturients were randomized into two groups: those receiving 2.0 ml of hyperbaric bupivacaine 0.5% and 0.4 ml of saline intrathecally and those receiving 2.0 ml of hyperbaric bupivacaine and 0.4 ml of fentanyl (20 microg) intrathecally. We performed spirometry on arriving at the operation room and 15 min after subarachnoid blockade.

RESULTS

Subarachnoid blockade with bupivacaine significantly decreased the peak expiratory flow rate, but did not induce significant changes in vital capacity and forced vital capacity. The addition of intrathecal fentanyl to bupivacaine improved the quality of subarachnoid blockade, but did not lead to a deterioration in respiratory function compared with intrathecal bupivacaine alone.

CONCLUSIONS

The addition of intrathecal fentanyl to hyperbaric bupivacaine did not lead to a deterioration in maternal spirometric respiratory function in parturients undergoing Cesarean section.

Impact of spinal anaesthesia on peri-operative lung volumes in obese and morbidly obese female patients*

Although obesity predisposes to postoperative pulmonary complications, data on the relationship between body mass index (BMI) and peri-operative respiratory performance are limited. We prospectively studied the impact of spinal anaesthesia, obesity and vaginal surgery on lung volumes measured by spirometry in 28 patients with BMI 30-40 kg.m(-2) and in 13 patients with BMI > or = 40 kg.m(-2). Vital capacity, forced vital capacity, forced expiratory volume in 1 s, mid-expiratory and peak expiratory flows were measured during the pre-operative visit (baseline), after effective spinal anaesthesia with premedication, and after the operation at 20 min, 1 h, 2 h, and 3 h (after mobilisation). Spinal anaesthesia and premedication were associated with a significant decrease in spirometric parameters. Spinal anaesthesia and premedication were associated with a significant decrease in spirometric parameters; mean (SD) vital capacities were - 19% (6.4) in patients with BMI 30-40 kg.m(-2) and - 33% (9.0) in patients with BMI > 40 kg.m(-2). The decrease of lung volumes remained constant for 2 h, whereas 3 h after the operation and after mobilisation, spirometric parameters significantly improved in all patients. This study showed that both spinal anaesthesia and obesity significantly impaired peri-operative respiratory function.

Obesity and obstetric anaesthesia

The prevalence of obesity continues to increase despite preventive strategies. Obese parturients are at increased risk of having either concurrent medical problems or superimposed antenatal diseases such as pre-eclampsia and gestational diabetes. Moreover, they have a tendency to labour abnormally contributing to increased instrumental delivery and Caesarean section. Obesity is a risk factor for anaesthesia related maternal mortality. Morbidly obese women must be considered as high-risk and deserve an anaesthetic consultation during their antenatal care. The significant difficulty in administering epidural analgesia should not preclude their use in labour. A more liberalised use of regional techniques may be a means to further reduce anaesthesia-related maternal mortality in the obese population. The mother's life should not be jeopardised to save a compromised fetus. Prophylactic placement of an epidural catheter when not contraindicated in labouring morbidly obese women would potentially decrease anaesthetic and perinatal complications associated with attempts at emergency provision of regional or general anaesthesia. Early mobilisation, aggressive chest physiotherapy and adequate pain control are essential components of effective postoperative care.

Comparison of perioperative spirometric data following spinal or general anaesthesia in normal-weight and overweight gynaecological patients

BACKGROUND

There is limited data comparing the impact of spinal anaesthesia (SA) and general anaesthesia (GA) on perioperative lung function. Here we assessed the differences of these two anaesthetic techniques on perioperative lung volumes in normal-weight (BMI < 25) and overweight (BMI 25-30) patients using spirometry.

METHODS

We prospectively studied 84 consenting patients having operations in the vaginal region receiving either GA (n = 41) or SA (n = 43). Both groups (GA and SA) were further divided into two subgroups each (normal-weight vs. overweight). We measured vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), midexpiratory (MEF25-75) and peak expiratory flow rates (PEFR) at the preoperative assessment (baseline), after premedication, after effective SA, and 20 min, 1 h, 2 h and 3 h after the operation (last measurement after patient mobilization).

RESULTS

Premedication was associated with a small but significant decrease in lung volumes in direct correlation with BMI (-5%). Spinal anaesthesia resulted in a significant reduction in lung volumes in overweight as opposed to normal-weight patients. Postoperatively, lung volumes were significantly more reduced following GA than SA as indicated by differences in mean VC (SD) of -12 (6)% vs. -6 (5)% 20 min after the end of the operation in the normal-weight and -18 (5)% vs. -10 (5)% in the overweight patients. There was a significant impact of BMI on postoperative respiratory function, which was significantly more important in the GA group than in the SA group, and recovery of lung volumes was more rapid in the normal-weight patients than in the overweight patients, particularly in the SA group.

CONCLUSION

In gynaecological patients undergoing vaginal surgery, the impact of anaesthesia on postoperative lung function as assessed by spirometry was significantly less after SA than GA, particularly in overweight patients.

Analgesia and Anesthesia in Labor

Whether given as an epidural, spinal, or combination, regional anesthesia is an integral part of obstetrics in the United States. A variety of drugs and dosages are used in various combinations, with no one protocol exceeding others in terms of efficacy and safety. The availability of anesthesia and analgesia has had an extraordinary impact on the field of obstetrics in the twentieth century. Knowledge of the techniques and medications used, their potential toxicities, and effects on the labor process itself can only enhance obstetricians' management of the parturient in labor.

Effect of obesity and thoracic epidural analgesia on perioperative spirometry

BACKGROUND

Lung volumes in obese patients are reduced significantly in the postoperative period. As the effect of different analgesic regimes on perioperative spirometric tests in obese patients has not yet been studied, we investigated the effect of thoracic epidural analgesia and conventional opioid-based analgesia on perioperative lung volumes measured by spirometry.

METHODS

Eighty-four patients having midline laparotomy for gynaecological procedures successfully completed the study. Premedication, anaesthesia and analgesia were standardized. The patients were given a free choice between epidural analgesia (EDA) (n=42) or opioids (n=42) for postoperative analgesia. We performed spirometry to measure vital capacity (VC), forced vital capacity, peak expiratory flow, mid-expiratory flow and forced expiratory volume in 1 s at preoperative assessment, 30-60 min after premedication and 20 min, 1 h, 3 h and 6 h after extubation.

RESULTS

Baseline values were all within the normal range. All perioperative spirometric values decreased significantly with increasing body mass index (BMI). The greatest reduction in VC occurred directly after extubation, but was less in the EDA group than in the opioid group: mean of -23(sd 8)% versus -30(12)% (P<0.001). In obese patients (BMI>30) the difference in VC was significantly more pronounced than in patients of normal weight (BMI<25): -45(10)% versus -33(4)% (P<0.001). Recovery of spirometric values was significantly quicker in patients receiving EDA, particularly in obese patients.

CONCLUSION

We conclude that EDA should be considered in obese patients undergoing midline laparotomy to improve postoperative spirometry.

Impact of spinal anaesthesia and obesity on maternal respiratory function during elective Caesarean section*

Spinal anaesthesia for Caesarean section has gained widespread acceptance. We assessed the impact of spinal anaesthesia and body mass index (BMI) on spirometric performance. In this prospective study, we consecutively assessed 71 consenting parturients receiving spinal anaesthesia with hyperbaric bupivacaine and fentanyl for elective Caesarean section. We performed spirometry during the antepartum visit (baseline), immediately after spinal anaesthesia, 10-20 min, 1 h, 2 h after the operation, and after mobilisation (3 h). Baseline values were within normal ranges. There was a significant decrease in all spirometric parameters after effective spinal anaesthesia that persisted throughout the study period. The decrease in respiratory function was significantly greater in obese (BMI > 30 kg x m(-2)) than in normal-weight parturients (BMI < 25 kg x m(-2)), e.g. median (IQR) vital capacity directly after spinal anaesthesia; -24 (-16 to -31)% vs. -11 (-6 to -16)%, p < 0.001 and recovery was significantly slower. We conclude that both spinal anaesthesia and obesity significantly impair respiratory function in parturients.