Oxytocin protocols during cesarean delivery: time to acknowledge the risk/benefit ratio?

Uterotonics, magnesium sulphate and antibiotics during childbirth and peripartum: Important obstetric drugs for the anaesthesiologist

The main causes of maternal mortality are comorbidities, hypertensive pregnancy syndrome, obstetric haemorrhage, and maternal sepsis. For this reason, uterotonics, magnesium sulphate, and antibiotics are essential tools in the management of obstetric patients during labour and in the peripartum period. These drugs are widely used by anaesthesiologists in all departments, and play a crucial role in treatment and patient safety. For the purpose of this narrative review, we performed a detailed search of medical databases and selected studies describing the use of these drugs in patients during pregnancy, delivery and the pospartum period. Uterotonics, above all oxytocin, play an important role in the prevention and treatment of pospartum haemorrhage, and various studies have shown that in obstetric procedures, such as scheduled and emergency caesarean section, they are effective at lower doses than those hitherto accepted. We also discuss the use of carbetocin as an effective alternative that has a therapeutic advantage in certain clinical circumstances. Magnesium sulphate is the gold standard in the prevention and treatment of eclampsia, and also plays a neuroprotective role in preterm infants. We describe the precautions to be taken during magnesium administration. Finally, we discuss the importance of understanding microbiology and the pharmacology of antibiotics in the management of obstetric infection and endometritis, and draw attention to the latest trends in antibiotic regimens in labour and caesarean section.

The minimum effective dose (ED90) of prophylactic oxytocin infusion during cesarean delivery in patients with and without obesity: an up-down sequential allocation dose-response study

BACKGROUND

Obesity is associated with greater oxytocin requirement during labor induction or augmentation. There are scant data exploring the intra-operative requirement during cesarean delivery in patients with obesity, and none comparing it with those without obesity. We evaluated the minimum effective dose (ED90) of an oxytocin infusion to achieve adequate uterine tone during cesarean delivery in patients with and without obesity.

METHODS

Patients (body mass index ≥30 kg/m2 represented patients with obesity) undergoing cesarean delivery using subarachnoid block were included. This prospective dual-arm dose-finding study used a 9:1 biased sequential allocation design. Oxytocin infusion was initiated at 13 IU/h at cord clamping in the first patient of each group. Uterine tone was graded as satisfactory or unsatisfactory by the obstetrician four minutes after initiation of the infusion. The dose of oxytocin infusion for subsequent patients was determined according to the response of the previous patient in the group. Oxytocin-associated side effects were evaluated. Dose-response data for the groups was evaluated using log-logistic function and ED90 estimates derived from fitted equations using the delta method.

RESULTS

The ED90 of oxytocin was significantly higher for patients with obesity (n = 40) compared with those without obesity (n = 40) [25.7 IU/h, 95% CI 18.6 to 32.9) vs. 16.6 IU/h, 95% CI 14.9 to 18.3)]; relative ratio 1.55 [95% CI 1.09 to 2.01] (P = 0.019).

CONCLUSIONS

Patients with obesity require a higher intra-operative oxytocin infusion dose rate to achieve a satisfactorily contracted uterus after fetal delivery when compared with patients without obesity.

Effect of an oxytocin protocol on secondary uterotonic use in patients undergoing Cesarean delivery

PURPOSE

Protocol-driven oxytocin regimens can reduce oxytocin administration compared with a nonprotocol free-flow continuous infusion. Our aim was to compare secondary uterotonic use between a modified "rule of threes" oxytocin protocol and a free-flow continuous oxytocin infusion after Cesarean delivery.

METHODS

We conducted a retrospective before-and-after study to compare patients who underwent Cesarean delivery between 1 January 2010 and 31 December 2013 (preprotocol) with patients who underwent Cesarean delivery between 1 January 2015 and 31 August 2017 (postprotocol). The preprotocol group received free-flow oxytocin administration and the postprotocol group received oxytocin according to a modified rule of threes algorithm. The primary outcome was secondary uterotonic use and the secondary outcomes included blood transfusion, hemoglobin value < 8 g·dL-1, and estimated blood loss.

RESULTS

In total, 4,010 Cesarean deliveries were performed in 3,637 patients (2,262 preprotocol and 1,748 postprotocol). The odds of receiving secondary uterotonic drugs were increased in the postprotocol group (odds ratio [OR], 1.33; 95% confidence interval [CI], 1.04 to 1.70; P = 0.02). Patients in the postprotocol group were less likely to receive a blood transfusion. Nevertheless, the two groups were similar for the composite end point of transfusion or hemoglobin < 8 g·dL-1 (OR, 0.86; 95% CI, 0.66 to 1.11; P = 0.25). The odds of an estimated blood loss greater than 1,000 mL were reduced in the postprotocol group (OR, 0.64; 95% CI, 0.50 to 0.84; P = 0.001).

CONCLUSIONS

Patients in the modified rule of threes oxytocin protocol group were more likely to receive a secondary uterotonic than those in the preprotocol group. Estimated blood loss and transfusion outcomes were similar.

Intravenous oxytocin regimens in patients undergoing cesarean delivery: a systematic review and network meta-analysis of cluster-based groups

Information on evaluations of different oxytocin regimens used to prevent post-partum hemorrhage during cesarean delivery is scarce, and there is a lack of statistically pooled results for comparative doses. In this review, we aimed to analyze the effectiveness of different oxytocin regimens used and rank them accordingly. We performed a meta-analysis of randomized controlled trials (RCTs) reporting the incidence of additional uterotonic (AUT) use or amount of blood loss during cesarean delivery, where different oxytocin regimens were compared. Cluster analysis was used to define different clusters of oxytocin therapy based on the identified variable regimens. During the frequentist network meta-analysis, all clusters were compared to bolus clusters of dose range 3-5 IU. Data from 33 RCTs (6741 patients) to 26 RCTs (5422 patients) were assessed for AUT use and blood loss, respectively. Pairwise meta-analysis revealed a significant reduction in the use of AUTs or blood loss was recorded for bolus-infusion combination regimens. The network meta-analysis found that combined bolus-infusion regimens of (i) 3-5 IU and 0.25-1 IU/min or (ii) 3-5 IU and < 0.25 IU/min had statistically significant results for lowest consumption of AUTs (Ranks 1 and 2, respectively); whereas with the latter's use, the lowest blood loss (Rank 2) was observed. In contrast, the dose range, > 5 IU regimen was associated with higher side effects (lowest rank). During cesarean delivery, a significant reduction in the use of AUTs or blood loss (Rank 2) was recorded for bolus-infusion combination regimens. High doses did not have enough evidence to draw meaningful conclusions.

Route of oxytocin administration for preventing blood loss at caesarean section: a systematic review with meta-analysis

OBJECTIVES

Assess the effects of different routes of prophylactic oxytocin administration for preventing blood loss at caesarean section (CS).

DESIGN

Systematic review and meta-analysis.

METHODS

Medline, EMBASE, CINAHL, Cochrane Library, BVS, SciELO and Global Index Medicus were searched through 24 May 2020 for randomised controlled trials (RCTs) comparing different routes of prophylactic oxytocin administration during CS. Study selection, data extraction and quality assessment were conducted by two investigators independently. We pooled results in fixed effects meta-analyses and calculated average risk ratio (RR), mean difference (MD) and 95% CI. We used GRADE to assess the overall quality of evidence for each outcome.

RESULTS

Three trials (180 women) were included in the review. All studies compared intramyometrial (IMY) versus intravenous oxytocin in women having prelabour CS. IMY compared with intravenous oxytocin administration may result in little or no difference in the incidence of postpartum haemorrhage (RR 0.14, 95% CI 0.01 to 2.70; N=100 participants; 1 RCT), hypotension (RR 1.00, 95% CI 0.29 to 3.45; N=40; 1 RCT), headache (RR 3.00, 95% CI 0.13 to 69.52; N=40; 1 RCT) or facial flushing (RR 0.50, 95% CI 0.05 to 5.08; N=40; 1 RCT); IMY oxytocin may reduce nausea/vomiting (RR 0.13, 95% CI 0.02 to 0.69; N=140; 2 RCTs). We are very uncertain about the effect IMY versus intravenous oxytocin on the need for additional uterotonics (RR 0.82; 95% CI 0.25 to 2.69; N=140; 2 RCTs). IMY oxytocin may reduce blood loss slightly (MD -57.40 mL, 95% CI -101.71 to -13.09; N=40; 1 RCT).

CONCLUSIONS

There is limited, low to very low certainty evidence on the effects of IMY versus intravenous oxytocin at CS for preventing blood loss. The evidence is insufficient to support choosing one route over another. More trials, including studies that assess intramuscular oxytocin administration, are needed on this relevant question.

PROSPERO REGISTRATION NUMBER

CRD42020186797.

Effective Dose of Prophylactic Oxytocin Infusion During Cesarean Delivery in 90% Population of Nonlaboring Patients With Preeclampsia Receiving Magnesium Sulfate Therapy and Normotensives: An Up-Down Sequential Allocation Dose-Response Study

BACKGROUND

Oxytocin administration during cesarean delivery is the first-line therapy for the prevention of uterine atony. Patients with preeclampsia may receive magnesium sulfate, a drug with known tocolytic effects, for seizure prophylaxis. However, no study has evaluated the minimum effective dose of oxytocin during cesarean delivery in women with preeclampsia.

METHODS

This study compared the effective dose in 90% population (ED90) of oxytocin infusion for achieving satisfactory uterine tone during cesarean delivery in nonlaboring patients with preeclampsia who were receiving magnesium sulfate treatment with a control group of normotensives who were not receiving magnesium sulfate. This prospective dual-arm dose-finding study was based on a 9:1 biased sequential allocation design. Oxytocin infusion was initiated at 13 IU/h, on clamping of the umbilical cord, in the first patient of each group. Uterine tone was graded as satisfactory or unsatisfactory by the obstetrician at 4 minutes after initiation of oxytocin infusion. The dose of oxytocin infusion for subsequent patients was decided according to the response exhibited by the previous patient in the group; it was increased by 2 IU/h after unsatisfactory response or decreased by 2 IU/h or maintained at the same level after satisfactory response, in a ratio of 1:9. Oxytocin-associated side effects were also evaluated. Dose-response data for the groups were evaluated using a log-logistic function and ED90 estimates were derived from fitted equations using the delta method.

RESULTS

The ED90 of oxytocin was significantly greater for the preeclampsia group (n = 27) than for the normotensive group (n = 40) (24.9 IU/h [95% confidence interval {CI}, 22.4-27.5] and 13.9 IU/h [95% CI, 12.4-15.5], respectively); the difference in dose requirement was 10.9 IU/h (95% CI, 7.9-14.0; P < .001). The number of patients with oxytocin-related hypotension, defined as a decrease in systolic blood pressure >20% from baseline or to <90 mm Hg, was significantly greater in the preeclampsia group (92.6% vs 62.5%; P = .030), while other side effects such as ST-T depression, nausea/vomiting, headache, and flushing, were not significantly different. There was no significant difference in the need for additional uterotonic or uterine massage, estimated blood loss, and need for re-exploration for uncontrolled bleeding.

CONCLUSIONS

Patients with preeclampsia receiving preoperative magnesium therapy need a greater intraoperative dose of oxytocin to achieve satisfactory contraction of the uterus after fetal delivery, as compared to normotensives.

Efficacy of different infusion rates of oxytocin for maintaining uterine tone during elective caesarean section: A randomised double blind trial

Most research in this field has focused on finding oxytocin doses for initiating uterine contractions. Only limited data are available regarding the optimal rate of oxytocin infusion to maintain adequate uterine tone. This randomised, double blind study included 120 healthy term pregnant patients with uncomplicated, singleton pregnancy undergoing elective caesarean section under spinal anaesthesia. Following an initial 1 IU bolus, the patients received oxytocin infusion at 1.25 IU/hour (group 1.25), 2.5 IU/hour (group 2.5) or 5.0 IU/hour (group 5) for four hours. Uterine tone was assessed as adequate or inadequate at various intervals. If found inadequate, additional uterotonics were administered. Estimated blood loss was mean (standard deviation) 499 (172) ml, 454 (117) ml and 402 (151) ml in groups 1.25, 2.5 and 5, respectively (P value groups 1.25 versus 5 = 0.012). Oxytocin infusion at 5 IU/hour resulted in a significantly lower incidence of minor postpartum haemorrhage, defined as blood loss greater than 500 ml, than 1.25 IU/hour (P = 0.009). No patient had major/severe haemorrhage (>1000 ml blood loss). No significant difference was seen in haemoglobin levels (P = 0.677) and uterine tone. Fifteen, six and nine patients, respectively, required additional oxytocin (P = 0.151). The incidence of tachycardia (P = 0.726), hypotension (P = 0.321) and nausea/vomiting (P = 0.161) was comparable. To conclude, 5 IU/hour was more effective than 1.25 IU/hour in reducing total blood loss and the incidence of minor postpartum haemorrhage. Thus 5 IU/hour appears to be an optimal oxytocin infusion rate following 1 IU slow intravenous oxytocin injection for the maintenance of adequate uterine contraction in patients undergoing elective caesarean section under spinal anaesthesia.

A randomised double-blind trial of minimal bolus doses of oxytocin for elective caesarean section under spinal anaesthesia: Optimal or not?

Background

Oxytocin administration regimens are arbitrary and highly subjective. Hence, it is essential to reinvestigate the appropriate dose for effective uterine contraction with minimal bleeding and adverse effects.

Aim

To determine the optimal dose of bolus oxytocin for uterine contractions for elective caesarean section under spinal anaesthesia.

Methods

Ninety term mothers (37 to 41 weeks) undergoing caesarean section electively under spinal anaesthesia were considered for the trial and divided into three groups to receive oxytocin bolus of one, two or three units. The uterine tone was assessed at 2 min after oxytocin administration. Intraoperative blood loss, mean arterial pressure, heart rate and possible side effects were also compared. Paired t-test, Kruskal-Wallis test, Chi-square test and analysis of variance (ANOVA) test with Scheffe multiple comparisons were used as inferential statistics.

Results

Adequate uterine contraction was seen in 66% of participants who received one unit of oxytocin, and in 83.3% of participants who received two units of oxytocin. All those who received three units of oxytocin had an adequate uterine contraction. Blood loss was inversely related to the bolus dose of oxytocin.

Conclusions

Lower bolus oxytocin doses of one and two units were inadequate for uterine contraction at elective caeserean section, while three units appeared to be effective in terms of adequate uterine contraction, reduced blood loss and stable haemodynamic system and absent side effects.

Management of the third stage of labour: (for the Optimal Intrapartum Care series edited by Mercedes Bonet, Femi Oladapo and Metin Gülmezoglu)

The physiology of the third stage of labour is described. Active management reduces the risk of postpartum haemorrhage (PPH), due to the use of a uterotonic agent. Intramuscular Oxytocin 10 IU has the highest efficacy and lowest side effect profile, although ergometrine, carbetocin and misoprostol are also effective. The appropriate uterotonic in different settings such as home birth by unskilled attendants and at caesarean section is discussed. For the latter, there is less consensus on the optimal dose/route of oxytocin, this topic remaining on the research agenda. Delayed cord clamping enables transfusion of blood to the neonate and is recommended rather than early clamping. Controlled cord traction should only be performed by skilled birth attendants and confers minimal advantage in preventing retained placenta. The importance of early recognition of PPH, and preparedness, is emphasised. An approach to medical and surgical management of PPH is presented.

Oxytocin in cesarean-sections. What's new?

Oxytocin is the uterotonic agent of choice in the prevention and treatment of postpartum uterine atony. Nevertheless, there is no consensus on the optimal dose and rate for use in cesarean sections. The use of high bolus doses (e.g., 10IU of oxytocin) can determine deleterious cardiovascular changes for the patient, especially in situations of hypovolemia or low cardiac reserve. Furthermore, high doses of oxytocin for prolonged periods may lead to desensitization of oxytocin receptors in myometrium, resulting in clinical inefficiency.

Oxytocin use during Caesarean sections in Denmark - are we getting the dose right?

BACKGROUND

In Denmark, an iv bolus of 10 IU oxytocin was traditionally given after delivery to prevent atony during caesarean sections. Randomized controlled trials have shown that lower iv bolus doses have same efficacy with fewer side effects and many countries now recommend a 5 IU maximum dose. The aims of this study were to investigate whether patients referred for allergy testing after oxytocin exposure had dose-related side effects to oxytocin rather than true allergic reactions and to investigate whether updated international recommendations on lower bolus doses had been implemented in practice.

METHODS

Medical notes of patients tested with oxytocin as part of investigations in the Danish Anaesthesia Allergy Centre from May 2004 to January 2014 were reviewed retrospectively. A telephone survey of on-duty obstetricians at all Danish obstetric departments was performed and most recent online recommendations from the Danish societies of obstetrics and anaesthesia about the use of oxytocin were identified.

RESULTS

In total 30 women were tested with oxytocin as part of investigations. None were allergic to oxytocin but 19 had symptoms consistent with dose-related side effects on iv provocation. The telephone survey revealed that iv doses of 10 IU oxytocin were still used and recommendations on the websites were not updated.

CONCLUSION

Too high oxytocin doses are still used in Denmark leading to dose-related side effects mimicking allergic reactions. Coordination between obstetricians and anaesthesiologists on producing common updated guidelines on the administration of oxytocin and dissemination of this information to obstetric and anaesthetic departments in Denmark is needed.

A Randomized, Double-blinded Trial of a "Rule of Threes" Algorithm versus Continuous Infusion of Oxytocin during Elective Cesarean Delivery

BACKGROUND

The administration of uterotonic agents during cesarean delivery is highly variable. The authors hypothesized a "rule of threes" algorithm, featuring oxytocin 3 IU, timed uterine tone evaluations, and a systematic approach to alternative uterotonic agents, would reduce the oxytocin dose required to obtain adequate uterine tone.

METHODS

Sixty women undergoing elective cesarean delivery were randomized to receive a low-dose bolus or continuous infusion of oxytocin. To blind participants, the rule group simultaneously received intravenous oxytocin (3 IU/3 ml) and a "wide-open" infusion of 0.9% normal saline (500 ml); the standard care group received intravenous 0.9% normal saline (3 ml) and a "wide-open" infusion of oxytocin (30 IU in 0.9% normal saline/500 ml). Uterine tone was assessed at 3, 6, 9, and 12 min, and if inadequate, additional uterotonic agents were administered. Uterine tone, total dose and timing of uterotonic agent use, maternal hemodynamics, side effects, and blood loss were recorded.

RESULTS

Adequate uterine tone was achieved with lower oxytocin doses in the rule versus standard care group (mean, 4.0 vs. 8.4 IU; point estimate of the difference, 4.4 ± 1.0 IU; 95% CI, 2.60 to 6.15; P < 0.0001). No additional oxytocin or alternative uterotonic agents were needed in either group after 6 min. No differences in the uterine tone, maternal hemodynamics, side effects, or blood loss were observed.

CONCLUSION

A "rule of threes" algorithm using oxytocin 3 IU results in lower oxytocin doses when compared with continuous-infusion oxytocin in women undergoing elective cesarean delivery.

[An update of the obstetrics hemorrhage treatment protocol]

Obstetric hemorrhage is still a major cause of maternal and fetal morbimortality in developed countries. This is an underestimated problem, which usually appears unpredictably. A high proportion of the morbidity of obstetric hemorrhage is considered to be preventable if adequately managed. The major international clinical guidelines recommend producing consensus management protocols, adapted to local characteristics and keep them updated in the light of experience and new scientific publications. We present a protocol updated, according to the latest recommendations, and our own experience, in order to be used as a basis for those anesthesiologists who wish to use and adapt it locally to their daily work. This last aspect is very important to be effective, and is a task to be performed at each center, according to the availability of resources, personnel and architectural features.

Anaesthesia for Caesarean Delivery in a Pregnant with Acute Type B Aortic Dissection

About 50% of aortic dissections in women younger than 40 years occur during pregnancy; mostly in the 3rd trimesters and postpartum period. Aortic dissection in pregnancy creates a serious mortality risk for both mother and the foetus. The ultimate goal is to ensure the safety of both the mother and the foetus. In such cases, the best method of anaesthesia for caesarean delivery is still controversial. The first aim of anaesthetic management is to reduce the effect of cardiovascular instability on the dissected aorta. Here, we report the anaesthetic management of a 36 year-old pregnant woman who developed acute type B aortic dissection in the 30(th) gestational weeks and scheduled for caesarean section. Since hemodynamic stability could not be achieved despite nitro-glycerine and esmolol infusions, together with invasive arterial monitoring, the decision for caesarean delivery was taken. A team of Cardiovascular Surgeons and an operating room were prepared because of the risks of aortic rupture and hemodynamic collapse during operation. Combined-spinal epidural anaesthesia was administered using 5 mg hyperbaric bupivacaine and 20 μg fentanyl given at the L3-4 spinal level in the side lying position. After achieving T4 sensory block level, the operation proceeded and a baby weighing 1432 grams was delivered in 4 min with a median subumbilical incision. Epidural patient controlled analgesia was applied to the patient during follow-up with medical treatment at postoperative period. In pregnant women with acute Type B aortic dissection, if adequate sensory block level cannot be achieved despite using a combination of low dose local anaesthetic (spinal use) and opioids, we are in the opinion that combined spinal-epidural anaesthesia, which allows the use of additional doses can be a decent choice.

Controversies in obstetric anesthesia

Obstetric anesthesia has become a widely evidence-based practice, with an increasing number of specialized anesthesiologists and a permanent research production. We believe that with the review of commonly discussed and controversial points the reader will be able to incorporate an evidence-based practice into their routine and offer to parturients and their babies a safe, reliable and consistent anesthesia care.

Systematic Review of Oxytocin Dosing at Caesarean Section

We undertook a systematic review to determine the optimal dose of oxytocin after elective caesarean section or caesarean section in labouring women. We identified seven trials. These trials raise questions about the use of high dose (10 international units; IU) or moderate dose (5 IU) oxytocin in both settings and provide evidence that lower doses are equally effective but associated with significantly fewer side-effects. For elective caesarean section, a slow 0.3 to 1 IU bolus of oxytocin over one minute, followed by an infusion of 5 to 10 IU.h−1 for four hours represents an evidence-based approach to dosing for women at low risk of postpartum haemorrhage. For the labouring parturient a slow 3 IU bolus of oxytocin, followed by an infusion of 5 to 10 IU.h−1 for four hours is supported by limited evidence. These doses represent a starting point in the control of postpartum haemorrhage after caesarean section and do not reduce the need for mandatory active observation of the clinical situation, to detect situations that require additional doses of oxytocin or other uterotonic drugs. These doses of oxytocin minimise the risk of adverse haemodynamic changes as well as the unpleasant side-effect of nausea.

[Update on the use of uterotonic agents]

Postpartum haemorrhage (PPH) is defined by the WHO as a blood loss >500mL after vaginal delivery or >1000mL after caesarean section during the first 24hours post-delivery. Although the incidence of maternal mortality caused by PPH has decreased, it continues to be the major cause of maternal mortality due to obstetric haemorrhage. Furthermore, the incidence of uterine atony, which is the most prevalent cause of PPH, is still increasing in both vaginal delivery and caesarean section. Although PPH occurs in more than two thirds of patients without any identifiable risk factor, a prolonged third stage of labour is the main risk factor. Active management of the third stage of labour has been postulated to reduce the risk of bleeding in this period. It includes the administration of uterotonic agents after the birth of the baby. Uterotonic agents are defined as drugs that produce adequate uterine contraction. These drugs can be used as prophylactic therapy or treatment. The prophylactic use of uterotonic agents has been reported to be associated with a shorter third stage of labour, less risk of PPH and less need of additional uterotonic agents. There are currently four drugs or groups of drugs with uterotonic action: oxytocin, carbetocin, ergot derivatives and prostaglandins. The literature on this subject is extensive, heterogeneous and sometimes discordant. Oxytocin is still the first-line uterotonic drug for prophylaxis and treatment of uterine atony. There is a common trend to use high doses of uterotonics for fear of inadequate uterine contraction, but the current literature recommends its reduction. Methylergonovine continues being the second-line uterotonic agent in the prophylaxis and treatment of PPH, because of its side effects. Despite carboprost (PGF2α) side effects, it is still the first-line prostaglandin for PPH treatment. Misoprostol may be an alternative to oxytocin when it is not available, although it needs further studies to support this. Finally, the prophylactic use of carbetocin should be individualised.

Use of a minimally invasive uncalibrated cardiac output monitor in patients undergoing cesarean section under spinal anesthesia: report of four cases

BACKGROUND AND OBJECTIVES

Hemodynamic changes are observed during cesarean section under spinal anesthesia. Non-invasive blood pressure (BP) and heart rate (HR) measurements are performed to diagnose these changes, but they are delayed and inaccurate. Other monitors such as filling pressure and cardiac output (CO) catheters with external calibration are very invasive or inaccurate. The objective of the present study was to report the cardiac output measurements obtained with a minimally invasive uncalibrated monitor (LiDCO rapid) in patients undergoing cesarean section under spinal anesthesia.

CASE REPORT

After approval by the Ethics Commission, four patients agreed to participate in this study. They underwent cesarean section under spinal anesthesia while at the same time being connected to the LiDCO rapid by a radial artery line. Cardiac output, HR, and BP were recorded at baseline, after spinal anesthesia, after fetal and placental extraction, and after the infusion of oxytocin and metaraminol. We observed a fall in BP with an increase of HR and CO after spinal anesthesia and oxytocin infusion; and an increase in BP with a fall in HR and CO after bolus of the vasopressor.

CONCLUSIONS

Although this monitor had not been calibrated, it showed a tendency for consistent hemodynamic data in obstetric patients and it may be used as a therapeutic guide or experimental tool.

Oxytocin for labour and caesarean delivery: implications for the anaesthesiologist

PURPOSE OF REVIEW

The implications of the obstetric use of oxytocin for obstetric anaesthesia practice are summarised. The review focuses on recent research on the uterotonic effects of oxytocin for prophylaxis and management of uterine atony during caesarean delivery.

RECENT FINDINGS

Oxytocin remains the first-line agent in the prevention and management of uterine atony. In-vitro and in-vivo studies show that prior exposure to oxytocin induces uterine muscle oxytocin receptor desensitization. This may influence oxytocin dosing for adequate uterine tone following delivery. Oxytocin has important cardiovascular side-effects (hypotension, tachycardia and myocardial ischaemia). Recent studies suggest that the effective dose of oxytocin for prophylaxis against uterine atony during caesarean delivery is significantly lower than the 5-10 IU historically used by anaesthesiologists. Slow administration of small bolus doses of oxytocin minimises maternal haemodynamic disturbance. Continuous oxytocin infusions are recommended for maintaining uterine tone after bolus administration, although ideal infusion rates are still to be established. The efficacy of the long-acting oxytocin analogue carbetocin requires further investigation. Recommendations are presented for oxytocin dosing during caesarean delivery.

SUMMARY

Oxytocin remains the first-line uterotonic after vaginal and caesarean delivery. Recent research elucidates the therapeutic range of oxytocin during caesarean delivery, as well as receptor desensitization. Evidenced-based protocols for the prevention and treatment of uterine atony during caesarean delivery are recommended.

[Efficacy of low-dose oxytocin during elective cesarean section]

BACKGROUND AND OBJECTIVE

In cesarean section, the optimal dose of oxytocin to reduce the risk of hemorrhage with the least risk of adverse effects has yet to be defined. We studied the effects of using 2 different doses of oxytocin in women undergoing elective cesarean section under spinal anesthesia. The women had had no prior labor.

MATERIAL AND METHODS

Randomized multicenter trial enrolling 104 patients classified as ASA 1. Following fetal extraction and coinciding with umbilical cord clamping, a group of 52 women received 1 IU of oxytocin followed by an infusion of 2.5 IU x h(-1); a second group of 52 women received a continuous infusion of 20 IU at a rate of 700 mlU x min(-1) followed by 10 IU x min(-1). We compared uterine contractility (assessed as absent, moderate, satisfactory), postoperative vaginal bleeding (absent, light, moderate, heavy), hemodynamics, and adverse effects after administration of oxytocin and fetal extraction (electrocardiographic abnormalities, nausea, vomiting, discomfort, headache, blushing, trembling, chills, or chest pain).

RESULTS

No significant between-group differences in patient, obstetric, or anesthetic variables were detected. Uterine contraction was satisfactory in over 90% of the patients in both groups on initial assessment during surgery. After surgery, vaginal bleeding was absent or light in over 90% of the women. No significant differences in adverse events were detected between groups.

CONCLUSIONS

The incidence of obstetric bleeding is not higher when a lower dose of oxytocin is used; the rate of postoperative adverse events also does not increase.