Colloid Preload Versus Coload for Spinal Anesthesia for Cesarean Delivery: The Effects on Maternal Cardiac Output

Is crystalloid co-loading necessary to prevent spinal hypotension during elective cesarean delivery? A randomized double-blind trial

BACKGROUND

Hypotension is common during spinal anesthesia for cesarean delivery. Preventive strategies include fluid loading and phenylephrine. We hypothesized that if prophylactic phenylephrine infusion is used, omission of fluid loading would be non-inferior to fluid co-loading in maintaining cardiac output. We assumed that if there was a difference, the increase in cardiac output would be greater in the no-loading than in the co-loading group.

METHODS

Term pregnant women scheduled for elective cesarean delivery were randomized to receive 1 L crystalloid co-loading or maintenance fluids only. Phenylephrine was titrated to maintain blood pressure. Changes in cardiac output following spinal anesthesia were the primary outcome. The study was powered as a non-inferiority trial, allowing the no-loading arm to have a 50% greater change in cardiac output. Heart rate, dose of phenylephrine, occurrence of nausea and vomiting, Apgar scores and neonatal acid base status were secondary outcomes.

RESULTS

Data from 63 women were analyzed. In contrast to our hypothesis, there was 33% less increase in cardiac output with no loading (ratio 0.67, 95% CI 0.15 to 1.36), and 60% greater reduction of cardiac output with no loading (ratio 1.6, 95% CI 1.0 to 2.7). Total dose of phenylephrine was higher in the no-loading group. There may be a less favorable neonatal acid base status without volume loading.

CONCLUSION

Omission of crystalloid co-loading leads to a decrease in cardiac output which has a potentially unfavorable impact on neonatal acid base status. We conclude that crystalloid co-loading may be useful in the presence of phenylephrine infusion.

Norepinephrine prevents hypotension in older patients under spinal anesthesia with intravenous propofol sedation: a randomized controlled trial

Reducing hypotension is crucial as hypotension is the most common side effect of spinal anesthesia, and in older patients with various comorbidities, it can lead to fatality. We hypothesized that continuous infusion of norepinephrine could effectively prevent hypotension in older patients undergoing hip surgery under spinal anesthesia with propofol sedation. The study randomly assigned patients aged ≥ 70 years to either a control (Group C, n = 35) or a norepinephrine group (Group N, n = 35). After spinal anesthesia, continuous infusion of propofol and normal saline or norepinephrine was initiated. The number of hypotensive episodes, the primary outcome, as well as other intraoperative hemodynamic events and postoperative complications were compared. In total, 67 patients were included in the final analysis. The number of hypotensive episodes was significantly higher in Group C than in Group N (p < 0.001). Furthermore, Group C required a greater amount of fluid to maintain normovolemia (p = 0.008) and showed less urine output (p = 0.019). However, there was no difference in postoperative complications between the two groups. Continuous intravenous infusion of prophylactic norepinephrine prevented hypotensive episodes, reduced the requirement of fluid, and increased the urine output in older patients undergoing unilateral hip surgery under spinal anesthesia with propofol sedation.Clinical trial registration number: KCT0005046 ( https://cris.nih.go.kr ). IRB number: 2020-0533 (Institutional Review Board of Asan Medical Center, approval date: 13/APR/2020).

Preliminary study on fluid bolus administration for prevention of spinal hypotension in dogs undergoing elective cesarean section

Introduction

This study aimed to investigate the effect of fluid bolus administration during epidural anesthesia (coload) in female dogs scheduled for elective cesarean section (CS). Hypotension is one of the most common complications of epidural (EA) and spinal (SA) analgesia, and in the case of cesarean section, it may pose a significant risk for placental perfusion and subsequent fetal vitality and puppy survival.

Methods

Pregnant bitches scheduled for elective CS underwent EA with (treatment group) or without (control group) intravenous fluid bolus administration. The following parameters were measured and compared between both groups: HR, RR, etCO₂, SpO₂, systolic, diastolic and mean arterial blood pressure were measured at three time points (T1: before surgery, T2: after the last puppy removal, and T3: end of surgery) in dams; vitality (Apgar score at 0, 5, and 20 min) and umbilical cord blood parameters (pH, pCO2, HCO3, base excess, lactate and glucose) in newborns.

Results

The results indicated that crystalloid coloading increased maternal systolic, diastolic, and mean blood pressure (treatment vs. control group, 101.46 ± 9.18, 48.01 ± 13.47, and 67.07 ± 13.15 mmHg vs. 80.68 ± 7.29, 36.52 ± 8.75, and 180 52.30 ± 7.77, p < 0.05) with significantly fewer episodes of hypotension. Additionally, puppies in the treatment group received higher scores in the 5-min (7.91 ± 1.67 vs. 6.74 ± 2.20) and 20-min (9.38 ± 0.87 vs. 8.39 ± 2.50) assessments without the favorable effect on umbilical blood gas parameters.

Discussion

Based on the obtained results, it can be stated that crystalloid coload offers an effective option in cases of hypotension during cesarean section, with clear benefits for both mothers and newborns.

Fluid loading therapy to prevent spinal hypotension in women undergoing elective caesarean section: Network meta-analysis, trial sequential analysis and meta-regression

BACKGROUND

Fluid loading is one of the recognised measures to prevent hypotension due to spinal anaesthesia in women scheduled for a caesarean section.

OBJECTIVE

We aimed to evaluate the current evidence on fluid loading in the prevention of spinal anaesthesia-induced hypotension.

DESIGN

Systematic review and network meta-analysis with trial sequential analysis and meta-regression.

DATA SOURCES

Medline, Epub, Embase.com (Embase and Medline), Cochrane Central, Web of Science and Google Scholar were used.

ELIGIBILITY CRITERIA

Only randomised controlled trials were used. Patients included women undergoing elective caesarean section who received either crystalloid or colloid fluid therapy as a preload or coload. The comparator was a combination of either a different fluid or time of infusion.

RESULTS

A total of 49 studies (4317 patients) were included. Network meta-analysis concluded that colloid coload and preload offered the highest chance of success (97 and 67%, respectively). Conventional meta-analysis showed that crystalloid preload is associated with a significantly higher incidence of maternal hypotension than colloid preload: risk ratio 1.48 (95% CI 1.29 to 1.69, P < 0.0001, I² = 60%). However, this result was not supported by Trial Sequential Analysis. There was a significant dose–response effect for crystalloid volume preload (regression coefficient = −0.073), which was not present in the analysis of only double-blind studies. There was no dose–response effect for the other fluid regimes.

CONCLUSION

Unlike previous meta-analysies, we found a lack of data obviating an evidence-based recommendation. In most studies, vasopressors were not given prophylactically as is recommended. Studies on the best fluid regimen in combination with prophylactic vasopressors are needed. Due to official european usage restrictions on the most studied colloid (HES), we recommend crystalloid coload as the most appropriate fluid regimen.

TRIAL REGISTRATION

CRD42018099347.

Effects of colloid preload on the incidence of hypotension in spinal anesthesia for cesarean section: a systematic review and meta-analysis

Background:

Hypotension is a common complication caused by spinal anesthesia (SA), which may have adverse impacts on the condition of the parturient and fetus. Liquid infusion was found to be relatively effective for reducing the incidence of hypotension. However, the question of whether colloid preload can optimize hemodynamic variables in the cesarean section remains controversial. This study aims to determine the effects of colloid preload on the incidence of hypotension induced by SA in elective cesarean section.

Methods:

Related keywords were searched on PubMed, EMBASE, and Cochrane Library from inception dates to May 2020. Studies included were evaluated for eligibility and quality. The primary outcome was the intra-operative incidence of hypotension and severe hypotension. The secondary outcomes included the lowest intra-operative systolic blood pressure, the maximal intra-operative heart rate, the intra-operative needs of ephedrine and phenylephrine, the incidence of maternal nausea and/or vomiting, and neonatal outcomes (umbilical artery pH and Apgar scores). Apart from the above, RevMan 5.3 was used for the data analysis.

Results:

Altogether nine randomized controlled trials were included in the meta-analysis. There were no significant differences in the incidence of intra-operative hypotension, severe hypotension, or neonatal outcomes between the colloid preload group and control group, except for the umbilical artery pH.

Conclusion:

This meta-analysis suggests that colloid preload does not significantly reduce the incidence of hypotension associated with SA in elective cesarean section.

Vasopressors for the Treatment and Prophylaxis of Spinal Induced Hypotension during Caesarean Section

Vasopressors have currently become the mainstay therapy for the management of spinal-induced hypotension (SIH) as the major mechanism of hypotension after spinal anaesthesia is the loss of arteriolar tone produced by sympathetic block. Vasopressors for the prophylaxis and treatment of SIH have been the subject of a significant amount of research, yet remain an attractive and important clinical problem. This review will highlight controversies and recent research on the use of vasopressors for both prophylaxis and treatment of SIH. For decades, ephedrine was considered to be the best vasopressor for the management of maternal hypotension. However, its use has been reported to be associated with a 5-fold increased risk of foetal acidosis than phenylephrine. At present, phenylephrine is the vasopressor of choice for preventing and treating SIH at caesarean section. However, its use is often associated with a decreased heart rate and low cardiac output state owing to the lack of β-mimetic activity. Norepinephrine has been introduced as an alternative vasopressor for preventing and treating SIH because of its additional β-mimetic activity. However before its routine clinical use, a further series of studies are needed to establish its efficacy and safety for both the mother and foetus.

Techniques for preventing hypotension during spinal anaesthesia for caesarean section

BACKGROUND

Maternal hypotension is the most frequent complication of spinal anaesthesia for caesarean section. It can be associated with nausea or vomiting and may pose serious risks to the mother (unconsciousness, pulmonary aspiration) and baby (hypoxia, acidosis, neurological injury).

OBJECTIVES

To assess the effects of prophylactic interventions for hypotension following spinal anaesthesia for caesarean section.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (9 August 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials, including full texts and abstracts, comparing interventions to prevent hypotension with placebo or alternative treatment in women having spinal anaesthesia for caesarean section. We excluded studies if hypotension was not an outcome measure.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study quality and extracted data from eligible studies. We report 'Summary of findings' tables using GRADE.

MAIN RESULTS

We included 125 studies involving 9469 women. Interventions were to prevent maternal hypotension following spinal anaesthesia only, and we excluded any interventions considered active treatment. All the included studies reported the review's primary outcome. Across 49 comparisons, we identified three intervention groups: intravenous fluids, pharmacological interventions, and physical interventions. Authors reported no serious adverse effects with any of the interventions investigated. Most trials reported hypotension requiring intervention and Apgar score of less than 8 at five minutes as the only outcomes. None of the trials included in the comparisons we describe reported admission to neonatal intensive care unit. Crystalloid versus control (no fluids) Fewer women experienced hypotension in the crystalloid group compared with no fluids (average risk ratio (RR) 0.84, 95% confidence interval (CI) 0.72 to 0.98; 370 women; 5 studies; low-quality evidence). There was no clear difference between groups in numbers of women with nausea and vomiting (average RR 0.19, 95% CI 0.01 to 3.91; 1 study; 69 women; very low-quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (60 babies, low-quality evidence). Colloid versus crystalloid Fewer women experienced hypotension in the colloid group compared with the crystalloid group (average RR 0.69, 95% CI 0.58 to 0.81; 2009 women; 27 studies; very low-quality evidence). There were no clear differences between groups for maternal hypertension requiring intervention (average RR 0.64, 95% CI 0.09 to 4.46, 3 studies, 327 women; very low-quality evidence), maternal bradycardia requiring intervention (average RR 0.98, 95% CI 0.54 to 1.78, 5 studies, 413 women; very low-quality evidence), nausea and/or vomiting (average RR 0.89, 95% CI 0.66 to 1.19, 14 studies, 1058 women, I² = 29%; very low-quality evidence), neonatal acidosis (average RR 0.83, 95% CI 0.15 to 4.52, 6 studies, 678 babies; very low-quality evidence), or Apgar score of less than 8 at five minutes (average RR 0.24, 95% CI 0.03 to 2.05, 10 studies, 730 babies; very low-quality evidence). Ephedrine versus phenylephrine There were no clear differences between ephedrine and phenylephrine groups for preventing maternal hypotension (average RR 0.92, 95% CI 0.71 to 1.18; 401 women; 8 studies; very low-quality evidence) or hypertension (average RR 1.72, 95% CI 0.71 to 4.16, 2 studies, 118 women, low-quality evidence). Rates of bradycardia were lower in the ephedrine group (average RR 0.37, 95% CI 0.21 to 0.64, 5 studies, 304 women, low-quality evidence). There was no clear difference in the number of women with nausea and/or vomiting (average RR 0.76, 95% CI 0.39 to 1.49, 4 studies, 204 women, I² = 37%, very low-quality evidence), or babies with neonatal acidosis (average RR 0.89, 95% CI 0.07 to 12.00, 3 studies, 175 babies, low-quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (321 babies; low-quality evidence). Ondansetron versus control Ondansetron administration was more effective than control (placebo saline) for preventing hypotension requiring treatment (average RR 0.67, 95% CI 0.54 to 0.83; 740 women, 8 studies, low-quality evidence), bradycardia requiring treatment (average RR 0.49, 95% CI 0.28 to 0.87; 740 women, 8 studies, low-quality evidence), and nausea and/or vomiting (average RR 0.35, 95% CI 0.24 to 0.51; 653 women, 7 studies, low-quality evidence). There was no clear difference between the groups in rates of neonatal acidosis (average RR 0.48, 95% CI 0.05 to 5.09; 134 babies; 2 studies, low-quality evidence) or Apgar scores of less than 8 at five minutes (284 babies, low-quality evidence). Lower limb compression versus control Lower limb compression was more effective than control for preventing hypotension (average RR 0.61, 95% CI 0.47 to 0.78, 11 studies, 705 women, I² = 65%, very low-quality evidence). There was no clear difference between the groups in rates of bradycardia (RR 0.63, 95% CI 0.11 to 3.56, 1 study, 74 women, very low-quality evidence) or nausea and/or vomiting (average RR 0.42, 95% CI 0.14 to 1.27, 4 studies, 276 women, I² = 32%, very-low quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (130 babies, very low-quality evidence). Walking versus lying There was no clear difference between the groups for women with hypotension requiring treatment (RR 0.71, 95% CI 0.41 to 1.21, 1 study, 37 women, very low-quality evidence). Many included studies reported little to no information that would allow an assessment of their risk of bias, limiting our ability to draw meaningful conclusions. GRADE assessments of the quality of evidence ranged from very low to low. We downgraded evidence for limitations in study design, imprecision, and indirectness; most studies assessed only women scheduled for elective caesarean sections. External validity also needs consideration. Readers should question the use of colloids in this context given the serious potential side effects such as allergy and renal failure associated with their administration.

AUTHORS' CONCLUSIONS

While interventions such as crystalloids, colloids, ephedrine, phenylephrine, ondansetron, or lower leg compression can reduce the incidence of hypotension, none have been shown to eliminate the need to treat maternal hypotension in some women. We cannot draw any conclusions regarding rare adverse effects associated with use of the interventions (for example colloids) due to the relatively small numbers of women studied.

Effects of isothermic crystalloid coload on maternal hypotension and fetal outcomes during spinal anesthesia for cesarean section: A randomized controlled trial

OBJECTIVE

Spinal anesthesia induced hypotension (SAIH) is a common occurrence during spinal anesthesia for cesarean section resulting in perturbing effects on maternal and fetal outcomes. Previous studies conducted to attenuate SAIH focused on the timing of intravenous fluid infusion and demonstrated the superiority of coload strategy on traditional preload strategy but neither of them focused on the effect of the temperature of crystalloid infused on SAIH and fetal outcomes. The current study aimed to assess the effect of the temperature of the crystalloid infused with coload strategy on the incidence of SAIH and fetal outcomes.

MATERIALS AND METHODS

Seventy-six parturients were enrolled into the study and data of 60 parturients were analyzed. Patients were randomly assigned to receive crystalloid coload at room temperature (Group RT, n = 30) or warmed at 37 °C (Group W, n = 30). The incidence of hypotension, cumulative hypotension episodes, heart rate, core body temperature, ephedrine dose, and fetal outcomes were recorded.

RESULTS

There was no significant difference in the incidence of maternal hypotension, cumulative hypotension episodes, and ephedrine dose (p = 0,625, p = 0,871, p = 0,460 respectively). Umbilical arterial pH and fetal Apgar scores at first and fifth minutes were higher in Group W than in Group RT (p = 0.013, p = 0.006 and p = 0.045 respectively). One fetus in Group RT but none in Group W had umbilical arterial pH lower than seven. Fetal birth weight and rectal temperature measurements were comparable in both groups (p = 0.639 and p = 0.675 respectively). Demographic data, patient characteristics, and surgery data were comparable between groups.

CONCLUSIONS

Isothermic crystalloid coload strategy results in higher umbilical pH values and Apgar scores in parturients scheduled for cesarean section under spinal anesthesia.

A Comparison Between the Effects of Preloading with Ringer's Solution and Voluven on Hemodynamic Changes in Patients Undergoing Elective Cesarean Section Under Spinal Anesthesia

Introduction

The most common complications after spinal anesthesia for Cesarean section is hypotension. Administration of intravenous crystalloid or colloid fluid before the induction of anesthesia is a way to prevent it.

Aim

The aim of this study was to compare the effects of preloading with ringer's solution and Voluven on hemodynamic changes in patients underwent elective Caesarean section under spinal anesthesia.

Methods

This study was conducted on 70 pregnant women. They were randomly divided into two groups of 35. Group I received 10 ml/kg Ringer's solution (R group) and group II received 10 ml/kg Voluven (V group) over 15 min before spinal anesthesia. Mean SBP, DBP, MAP, HR, SPO2, mean Apgar of newborn at 1 and 5 minutes after birth, mean blood pH and analysis of umbilical venous blood gases of newborns, prevalence of nausea and vomiting, and the rate of shivering and its severity were recorded in the both groups.

Results

Blood pH and analysis of blood gases and Apgar of newborn at 1 and 5 minutes after birth were similar in both groups. Shivering did not differ significantly between the two groups. Level of anesthesia and the incidence of nausea and vomiting in the R group were significantly higher than those in the V group (P=0.041 and P=0.029, respectively).

Conclusion

The administration of both crystalloid and colloid fluids were effective in preventing the hypotension, although the use of Voluven was preferred to Ringer with respect to the level of the blockade and the incidence of nausea and vomiting.

Effects of Vasoactive Medications and Maternal Positioning During Cesarean Delivery on Maternal Hemodynamics and Neonatal Acid-Base Status

Maternal hemodynamics, positioning, and anesthesia technique for cesarean delivery influence neonatal acid-base balance; direct effects from drugs that cross the placenta also have an influence. Spinal anesthesia limits fetal exposure to depressant drugs and avoids maternal airway instrumentation, but is associated with hypotension. Hypotension may be prevented/treated with vasopressors and intravenous fluids. Current evidence supports phenylephrine as the first-line vasopressor. Fifteen degrees of lateral tilt during cesarean delivery has been advocated to relieve vena caval obstruction, but routine use may be unnecessary in healthy nonobese women having elective cesarean delivery if maternal blood pressure is maintained near baseline.

Prevention of hypotension after spinal anaesthesia for caesarean section: a systematic review and network meta-analysis of randomised controlled trials

Spinal anaesthesia for caesarean section commonly causes maternal hypotension. This systematic review and network meta-analysis compared methods to prevent hypotension in women receiving spinal anaesthesia for caesarean section. We selected randomised controlled trials that compared an intervention to prevent hypotension with another intervention or inactive control by searching MEDLINE and Embase, Web of Science to December 2018. There was no language restriction. Two reviewers extracted data on trial characteristics, methods and outcomes. We assessed risk of bias for individual trials (Cochrane tool) and quality of evidence (GRADE checklist). We assessed 109 trials (8561 women) and 12 different methods that resulted in 30 direct comparisons. Methods ranked by OR (95%CI) from most effective to least effective were: metaraminol 0.11 (0.04-0.26); norepinephrine 0.13 (0.06-0.28); phenylephrine 0.18 (0.11-0.29); leg compression 0.25 (0.14-0.43); ephedrine 0.28 (0.18-0.43); colloid given before induction of anaesthesia 0.38 (0.24-0.61); angiotensin 2, 0.12 (0.02-0.75); colloid given after induction of anaesthesia 0.52 (0.30-0.90); mephentermine 0.09 (0.01-1.30); crystalloid given after induction of anaesthesia 0.78 (0.46-1.31); and crystalloid given before induction of anaesthesia 1.16 (0.76-1.79). Phenylephrine caused maternal bradycardia compared with control, OR (95%CI) 0.23 (0.07-0.79). Ephedrine lowered umbilical artery pH more than phenylephrine, standardised mean difference (95%CI) 0.78 (0.47-1.49). We conclude that vasopressors should be given to healthy women to prevent hypotension during caesarean section with spinal anaesthesia.

Effect of Glucose Containing Crystalloid Infusion on Maternal Hemodynamic Status After Spinal Anesthesia for Cesarean Section

Background

Despite preventive strategies, hypotension is the most common complication of spinal anesthesia in cesarean section.

Objectives

The aim of this study was to assess the effect of glucose-containing crystalloid infusion on maternal hemodynamic status after spinal anesthesia for cesarean section.

Methods

In this prospective, randomized, double-blind clinical trial, 80 parturients undergoing elective cesarean section with spinal anesthesia were studied. In group A (n = 40) ringer with 1% glucose solution (10 gr glucose in 1000 mL ringer) and in group B (n = 40) only ringer solution infused before and after spinal anesthesia. Demographic data, hemodynamic change, complications and their treatments, maternal blood sugar level and neonatal APGAR (appearance, pulse, grimace, activity and respiration) score, intraoperative fluid, duration of surgery, and anesthesia were recorded in the two groups.

Results

The incidence of hypotension in group A was significantly lower than group B (27.5% vs 75%) (P = 0.002). Other complications (sustained hypotension, nausea, pallor, and shivering were significantly lower in parturients of the group A (P < 0.05). Maternal blood sugar (BS), before and after surgery, was not significantly different in the two groups (P = 0.207 and P = 0.239, respectively). There was no statistically significant difference in the APGAR score of neonates at the 1st and 5th minutes of the birth between the two groups (P = 0.076).

Conclusions

It seems that adding 1% glucose to crystalloid solution improves the hemodynamic status and decreases post-spinal anesthesia complications without significant changes in the maternal blood sugar level and APGAR score of neonates.

Pleth variability index can predict spinal anaesthesia-induced hypotension in patients undergoing caesarean delivery

BACKGROUND

Spinal anaesthesia carries a risk of hypotension. We hypothesized that pleth variability index and perfusion index would assess maternal volume status, and thus, allow identification of patients at higher risk of developing hypotension after spinal anaesthesia for caesarean delivery.

METHODS

Fifty patients undergoing elective caesarean delivery were enrolled. All patients received spinal anaesthesia with 0.5% hyperbaric bupivacaine (10 mg) and fentanyl (10 mcg). Blood pressure was measured every minute. Pleth variability index and perfusion index were automatically measured throughout the procedure using pulse oximetry on the index finger. In case of hypotension (systolic blood pressure below 90 mmHg or 80% of the baseline value), ephedrine 5 mg was administered. Receiver-operating characteristic and multivariate logistic regression analyses for spinal anaesthesia-induced hypotension were performed.

RESULTS

Hypotension occurred in 32 patients (64%). The areas under the receiver-operating characteristic curve were 0.751 (95% confidence interval: 0.597-0.904) for pleth variability index before anaesthesia, 0.793 (95% confidence interval: 0.655-0.930) for pleth variability index after anaesthesia and 0.731 (95% confidence interval: 0.570-0.892) for perfusion index change (percent change in perfusion index induced by spinal anaesthesia). The optimal threshold value of pleth variability index (after anaesthesia) for predicting hypotension was 18% (sensitivity: 78.1%, specificity: 83.3%). Pleth variability index after spinal anaesthesia was an independent factor for hypotension (odds ratio: 1.21, P = 0.041).

CONCLUSIONS

Pleth variability index after spinal anaesthesia was a good predictor of spinal anaesthesia-induced hypotension in patients undergoing caesarean delivery. In addition, perfusion index change after spinal anaesthesia has the potential to predict hypotension.

Techniques for preventing hypotension during spinal anaesthesia for caesarean section

BACKGROUND

Maternal hypotension is the most frequent complication of spinal anaesthesia for caesarean section. It can be associated with nausea or vomiting and may pose serious risks to the mother (unconsciousness, pulmonary aspiration) and baby (hypoxia, acidosis, neurological injury).

OBJECTIVES

To assess the effects of prophylactic interventions for hypotension following spinal anaesthesia for caesarean section.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (9 August 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials, including full texts and abstracts, comparing interventions to prevent hypotension with placebo or alternative treatment in women having spinal anaesthesia for caesarean section. We excluded studies if hypotension was not an outcome measure.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study quality and extracted data from eligible studies. We report 'Summary of findings' tables using GRADE.

MAIN RESULTS

We included 126 studies involving 9565 participants. Interventions were to prevent maternal hypotension following spinal anaesthesia only, and we excluded any interventions considered active treatment. All the included studies reported the review's primary outcome. Across 49 comparisons, we identified three intervention groups: intravenous fluids, pharmacological interventions, and physical interventions. Authors reported no serious adverse effects with any of the interventions investigated. Most trials reported hypotension requiring intervention and Apgar score of less than 8 at five minutes as the only outcomes. None of the trials included in the comparisons we describe reported admission to neonatal intensive care unit. Crystalloid versus control (no fluids)Fewer women experienced hypotension in the crystalloid group compared with no fluids (average risk ratio (RR) 0.84, 95% confidence interval (CI) 0.72 to 0.98; 370 women; 5 studies; low-quality evidence). There was no clear difference between groups in numbers of women with nausea and vomiting (average RR 0.19, 95% CI 0.01 to 3.91; 1 study; 69 women; very low-quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (60 babies, low-quality evidence). Colloid versus crystalloidFewer women experienced hypotension in the colloid group compared with the crystalloid group (average RR 0.68, 95% CI 0.58 to 0.80; 2105 women; 28 studies; very low-quality evidence). There were no clear differences between groups for maternal hypertension requiring intervention (average RR 0.64, 95% CI 0.09 to 4.46, 3 studies, 327 women;very low-quality evidence), maternal bradycardia requiring intervention (average RR 0.99, 95% CI 0.55 to 1.79, 6 studies, 509 women; very low-quality evidence), nausea and/or vomiting (average RR 0.83, 95% CI 0.61 to 1.13, 15 studies, 1154 women, I² = 37%; very low-quality evidence), neonatal acidosis (average RR 0.83, 95% CI 0.15 to 4.52, 6 studies, 678 babies; very low-quality evidence), or Apgar score of less than 8 at five minutes (average RR 0.24, 95% CI 0.03 to 2.05, 11 studies, 826 babies; very low-quality evidence). Ephedrine versus phenylephrineThere were no clear differences between ephedrine and phenylephrine groups for preventing maternal hypotension (average RR 0.92, 95% CI 0.71 to 1.18; 401 women; 8 studies; very low-quality evidence) or hypertension (average RR 1.72, 95% CI 0.71 to 4.16, 2 studies, 118 women, low-quality evidence). Rates of bradycardia were lower in the ephedrine group (average RR 0.37, 95% CI 0.21 to 0.64, 5 studies, 304 women, low-quality evidence). There was no clear difference in the number of women with nausea and/or vomiting (average RR 0.76, 95% CI 0.39 to 1.49, 4 studies, 204 women, I² = 37%, very low-quality evidence), or babies with neonatal acidosis (average RR 0.89, 95% CI 0.07 to 12.00, 3 studies, 175 babies, low-quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (321 babies; low-quality evidence). Ondansetron versus controlOndansetron administration was more effective than control (placebo saline) for preventing hypotension requiring treatment (average RR 0.67, 95% CI 0.54 to 0.83; 740 women, 8 studies, low-quality evidence), bradycardia requiring treatment (average RR 0.49, 95% CI 0.28 to 0.87; 740 women, 8 studies, low-quality evidence), and nausea and/or vomiting (average RR 0.35, 95% CI 0.24 to 0.51; 653 women, 7 studies, low-quality evidence). There was no clear difference between the groups in rates of neonatal acidosis (average RR 0.48, 95% CI 0.05 to 5.09; 134 babies; 2 studies, low-quality evidence) or Apgar scores of less than 8 at five minutes (284 babies, low-quality evidence). Lower limb compression versus controlLower limb compression was more effective than control for preventing hypotension (average RR 0.61, 95% CI 0.47 to 0.78, 11 studies, 705 women, I² = 65%, very low-quality evidence). There was no clear difference between the groups in rates of bradycardia (RR 0.63, 95% CI 0.11 to 3.56, 1 study, 74 women, very low-quality evidence) or nausea and/or vomiting (average RR 0.42 , 95% CI 0.14 to 1.27, 4 studies, 276 women, I² = 32%, very-low quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (130 babies, very low-quality evidence). Walking versus lyingThere was no clear difference between the groups for women with hypotension requiring treatment (RR 0.71, 95% CI 0.41 to 1.21, 1 study, 37 women, very low-quality evidence).Many included studies reported little to no information that would allow an assessment of their risk of bias, limiting our ability to draw meaningful conclusions. GRADE assessments of the quality of evidence ranged from very low to low. We downgraded evidence for limitations in study design, imprecision, and indirectness; most studies assessed only women scheduled for elective caesarean sections.External validity also needs consideration. Readers should question the use of colloids in this context given the serious potential side effects such as allergy and renal failure associated with their administration.

AUTHORS' CONCLUSIONS

While interventions such as crystalloids, colloids, ephedrine, phenylephrine, ondansetron, or lower leg compression can reduce the incidence of hypotension, none have been shown to eliminate the need to treat maternal hypotension in some women. We cannot draw any conclusions regarding rare adverse effects associated with use of the interventions (for example colloids) due to the relatively small numbers of women studied.

Effects of hydroxyethyl starch 6 % (130/0.4) on blood loss during cesarean delivery: a propensity-matched analysis

BACKGROUND

Hydroxyethyl starch is commonly used in the obstetric patient population to prevent hypotension during cesarean delivery. Evidence suggests hetastarch is associated with a dysfunction in coagulation cascade. We hypothesized that hetastarch use to prevent spinal hypotension during cesarean delivery would be associated with an increase in blood loss when compared to crystalloid use.

METHODS

We performed a retrospective review of patients who underwent elective cesarean delivery under spinal anesthesia at the University of Virginia between 2011 and 2014. Data from 819 patients was used. Blood loss was the primary outcome. Propensity score-matching was used to match patients who received hetastarch (treatment group) with those who did not receive hetastarch (control group).

RESULTS

Genetic matching resulted in 196 patients in the hetastarch group and 182 patients in the control group. There was no difference in estimated blood loss (p = 0.068), calculated blood loss (p = 0.720), total intraoperative fluid intake (p = 0.289), urine output (p = 0.421), Apgar 1 min (p = 0.830), Apgar 5 min (p = 0.138), phenylephrine consumption (p = 0.742), postoperative day 1 (POD1) hematocrit (p = 0.070) and POD1 platelets (p = 0.233). However, there was a statistically significant difference (but clinically irrelevant) in hematocrit difference between the day of admission and POD1 (mean difference 0.47, p = 0.024), and ephedrine consumption (mean difference 2 mg, p = 0.017) in favor of the control group.

CONCLUSIONS

Our study did not find an association between increased perioperative blood loss and hetastarch use in patients presenting for elective cesarean delivery.

Efficacy of different fluids preload on propofol injection pain: A randomized, controlled, double-blinded study

Injection pain of propofol remains a common clinical problem. Previous studies demonstrated that propofol injection pain was alleviated by applying nitroglycerin ointment to the skin of injection site, which inspires us to test whether venous vasodilation induced by fluid preload could alleviate the pain. Different types or volumes of fluid preload were compared. 200 ASA I-II adult patients were randomly assigned to five groups of 40 each. A 20 G cannula was established on the dorsum or wrist of the hand. When fluid preload given with Plasma-Lyte A 100 mL (P100 group), 250 mL (P250 group), 500 mL (P500 group), 0.9% saline 500 mL (N500 group) or Gelofusine 500 mL (G500 group) was completed within 30 min, respectively, Propofol (0.5 mg/kg, 1%) was injected at a rate of 0.5 mL/s. A blind investigator assessed the pain using a four-point scale. Incidence of pain in P100, P250, and P500 groups was 87.5%, 57.5% and 35%, respectively (P<0.05). The median pain intensity score was significantly lower in P500 group than that in P250 and P100 groups (P<0.05 and P<0.01, respectively). Comparison of the effect of different types of solution preload indicated that the highest incidence of pain was in N500 group (62.5%) (N500 vs. P500, P=0.014; N500 vs. G500, P=0.007). The median pain intensity score in N500 group was higher than that in P500 group (P<0.05) and G500 group (P<0.05). There was no significant difference between P500 and G500 groups. It is suggested that Plasma-Lyte A or Gelofusine preload with 500 mL before propofol injection is effective in alleviating propofol-induced pain.

Six percent hetastarch versus lactated Ringer's solution - for preloading before spinal anesthesia for cesarean section

BACKGROUND

Regional anesthesia has been the choice of preference for elective cesarean sections. This study was designed to determine whether preoperative administration of 6% hetastarch decreases the incidence of hypotension.

MATERIALS AND METHODS

This study was conducted on 50 nonlaboring American Society of Anesthesiologists class I and II women undergoing elective cesarean section. Patients were randomly divided into two groups and were preloaded either with 1000 ml Ringer's lactate (RL) or 500 ml of 6% hetastarch 30 min prior to the surgery. Spinal anesthesia was performed with patients in the left lateral position and 2 cc (10 mg) of 0.5% of bupivacaine injected into subarachnoid space. Hemodynamic variables (heart rate, noninvasive blood pressure, and SpO2) were recorded from prior to preloading until the recovery from the subarachnoid blockade.

RESULTS

Our study showed the incidence of hypotension to be 28% in the hetastarch group and 80% in the RL group. Rescue ephedrine requirements for the treatment of hypotension were significantly less in patients who were preloaded with 6% hetastarch prior to cesarean section. The neonatal outcome, as determined by Apgar scores was good and similar in both groups.

CONCLUSION

Hence, we conclude that 6% hydroxyl ethyl starch is more effective than lactated Ringers solution and that its routine use for preloading prior to spinal anesthesia should be considered.

The Effect of Ringer versus Haemaccel Preload on Incidence of Postoperative Nausea and Vomiting

INTRODUCTION

Postoperative nausea and vomiting (PONV) is the most common and unpleasant postoperative complication. There is much controversy on preoperative fluid therapy. The aim of this study was to examine the effect of crystalloid fluid (Ringer solution) versus colloid (Haemaccel solution) on the incidence of postoperative nausea and vomiting in patients receiving spinal anesthesia.

METHODS

In this double-blinded clinical trial, 46 patients were selected according to the inclusion and exclusion criteria. Patients were randomly allocated to one of two groups. The crystalloid group received Ringer solution at a volume of 7 ml/kg and colloid group received 7ml/kg of 3% Modified Gelatin (Haemaccel) as a preoperative intravenous bolus. We used a Verbal Rating Scale (VRS) for assessing the nausea and vomiting occurrence. Data were analyzed using SPSS software ver.13 and χ(2) test and independent t-test.

RESULTS

The result showed that the incidence of PONV was less frequent in both Ringer and Haemaccel groups, but the incidence of vomiting and the intensity of nausea was not significantly different in any time point after anesthesia.

CONCLUSION

We conclude that preoperative fluid administration decreases the incidence of PONV, and both Crystalloids (Ringer) and colloids (haemaccel) solution were found to be equivalent in prevention of PONV. Therefore using of either Ringer or haemaccel solution is recommended for prevention of PONV.

Fluid Administration Before Caesarean Delivery: Does Type and Timing Matter?

BACKGROUND

The effectiveness of fluid preloading is in doubt, so co-loading has been attempted to reduce the incidence of spinal anaesthesia induced hypotension in caesarean patients.

AIM

To compare crystalloid preloading, colloid preloading and colloid co-loading for prevention of maternal hypotension in caesarean delivery.

SETTINGS AND DESIGN

Study conducted in tertiary level hospital on 90 ASA I/II term parturients posted for elective caesarean section. Patients were randomly allocated to three Groups.

MATERIALS AND METHODS

Group A (n=30) was given 10 ml/kg of 6% hydroxyethyl starch (HES) 20 minutes prior to spinal anaesthesia, Group B (n=30) was given 10 ml/kg of 6% HES by rapid infusion in 10 minutes immediately after spinal anaesthesia and Group C (n=30) was given 10 ml/kg of Ringer's Lactate 20 minutes prior to spinal anaesthesia. Intraoperatively, Heart rate, systolic, diastolic and mean arterial pressure were recorded every five minutes. Episodes of hypotension were recorded and treated with bolus of 5 mg of ephedrine and total amount of ephedrine was noted. Adverse effects, if any were recorded.

STATISTICAL ANALYSIS

ANNOVA for Quantitative Analysis and chi-Square test and Z-test for Qualitative Analysis.

RESULTS

Baseline parameters were similar in all the three Groups. Heart rate decreased from the baseline in all the three Groups, however, mean heart rate was highest in Group C. Heart rate was statistically similar in Groups A and B. MAP decreased in all three Groups from baseline, however, highest fall was recorded in Group C whereas, MAP was statistically similar in Groups A and B. Incidence of hypotension was 66.66% in Group C as compared to 36.66% in Groups A and 40% in Group B respectively. Group C patients received 5.33±4.54 mg of ephedrine as compared to 2.00±2.82 mg in Group A and 2.33±3.14 mg in Group B. Thus, the incidence of hypotension and ephedrine consumption was significantly higher in Group C as compared to Groups A and B whereas, this difference was statistically not significant among Groups A and B.

CONCLUSION

Colloid preloading and co-loading are equally effective and both are superior to crystalloid preloading for prevention of maternal hypotension in caesarean section patients.

Comparison of colloid preload versus coload under low dose spinal anesthesia for cesarean delivery

Background:

Although fluid bolus is considered as a conventional prophylactic measure to prevent spinal-induced hypotension; vasopressors are nevertheless required. Low dose spinal anesthetics could markedly reduce such episodes of hypotension, by minimizing sympathetic blockade.

Aims:

We chose to compare the relative efficacy of colloid preload versus coload under low dose spinal anesthesia, for elective cesarean delivery.

Settings and Design:

A prospective, randomized, double-blinded study.

Materials and Methods:

In total, 42 parturients were randomized to receive a preload (Group P) of hydroxyl ethyl starch (10 ml/kg) over 20 min before initiation of low dose spinal anesthesia (hyperbaric bupivacaine 5.5 mg with fentanyl 25 μg) or coload (Group C) of an identical fluid over 5 min, starting at the time of identification of cerebrospinal fluid. Our primary outcome included hemodynamic parameters and the incidence of hypotension. The neonatal outcome and side-effects were also monitored.

Statistical Analysis:

Mann-Whitney U test and Fisher's exact/Chi-square test, whichever appropriate. A P < 0.05 was considered to be significant.

Results:

The incidence of hypotension was lower in Group P (10%) when compared with Group C (25%), though insignificant statistically. The hemodynamic parameters were better in Group P, though intergroup statistical differences were not observed. The time to the first episode of hypotension was longer in the Group P (17 min) as compared with Group C (14 min). No notable side-effects or adverse neonatal outcome was noted.

Conclusion:

Colloid preload has a clinical advantage over the coload strategy, in reducing hypotensive episodes under low dose spinal anesthesia. Preload is better under large hemodynamic fluctuations while coload is preferable for emergency scenarios.

Co-loading or pre-loading for prevention of hypotension after spinal anaesthesia! a therapeutic dilemma

Neuraxial blockade such as spinal anaesthesia can cause severe hypotension due to pharmacological sympathectomy resulting in potential deleterious consequences for the patient. Prevention of this spinal anaesthesia induced hypotension is of utmost importance especially in pregnant population as the life of mother as well as fetus is at risk. Several techniques and methodologies have been adopted for the prevention of this neuraxial hypotension with varying degree of success. The administration of intravenous fluids to optimize the blood volume during sympathectomy has been the most popular and widely used as the first line of therapy among these techniques. The intravenous fluids can be used both before and during the administration of spinal anaesthesia, the techniques appropriately named as pre-loading and co-loading respectively. Numerous research studies and available literary evidence suggests that both of these techniques can be equally effective in prevention of hypotension. The use of colloids has been observed to be more effective for pre-loading due to their longer half-life in the intravascular compartment. However, it has also been suggested that no technique is efficient in preventing the hypotension alone and has to be coupled with judicious use of vasopressors.

[Prevention of hypotension during spinal anesthesia for elective caesarean section: coloading with HAE 130/0.4 vs normal saline solution]

OBJECTIVE

The aim of this study was to compare the efficacy of HES 130/0.4 coloading compared to normal saline solution for prevention of hypotension during spinal anesthesia for elective caesarean section.

STUDY DESIGN

Prospective, randomized.

PATIENTS AND METHODS

One hundred and twenty ASA I and II patients scheduled for elective caesarean section were recruited. Patients were randomized to receive either 500mL of HES 130/0.4 (Voluven(®)) coloading (GroupV) or 500mL of normal saline solution coloading (GroupC). Spinal anesthesia technique and ephedrine administration were standardized in both groups. The primary endpoint was the incidence of maternal hypotension during spinal anesthesia for elective caesarean section.

RESULTS

Hypotension occurred in 43 patients in group C and 24 patients in group V (p=0.001). Ephedrine consumption was significantly lower in group V (P=0.005). Nausea, vomiting and headache incidence was higher in group C (p=0.006). Apgar scores and umbilical blood gazes were comparable between groups.

CONCLUSION

HES 130/0.4 coload was more effective than normal saline solution to prevent hypotension following spinal anesthesia for elective cesarean section. HES 130/0.4 coload reduced the incidence, the duration of longest hypotension, the need for ephedrine and the adverse maternal effects.

Update on volume therapy in obstetrics

Symptomatic hypotension (maternal nausea, vomiting, dizziness and dyspnoea) during spinal anaesthesia for caesarean delivery remains a prevalent clinical problem. Severe and sustained hypotension can lead to impairment of uteroplacental perfusion, foetal hypoxia, acidosis, neonatal depression and further adverse maternal outcomes of unconsciousness, pulmonary aspiration, apnoea and cardiac arrest. Mechanical methods aimed at countering the effects of aortocaval compression do not reliably prevent maternal hypotension. Intravenous crystalloid preloading (given prior to administration of spinal anaesthesia) has poor efficacy, and focus has changed towards decreased use of crystalloid preload and ephedrine, to increased use of coload (given at the time of spinal administration) with colloids or crystalloids, and early use of phenylephrine. The recent multicentre, randomised, double-blinded CAESAR trial demonstrated the efficacy of a mixed 500 ml 6% hydroxyethyl starch (HES) 130/0.4 + 500 ml Ringer's lactate (RL) preload in significantly reducing hypotension, compared to a 1-l RL preload, without adverse effects on coagulation and neonatal outcomes in healthy parturients undergoing caesarean delivery under spinal anaesthesia.

Influence of the timing of administration of crystalloid on maternal hypotension during spinal anesthesia for cesarean delivery: preload versus coload

Background

Prophylactic fluid preloading before spinal anesthesia has been a routine procedure to prevent maternal hypotension during cesarean delivery. Unlike colloid, timing of infusion of crystalloid may be important because of its short stay in intravascular space. We hypothesized that crystalloid loading just after intrathecal injection compared to preload would be more effective in preventing maternal hypotension.

Methods

In this prospective controlled study, sixty parturients were randomized to receive 15 ml/kg of crystalloid before (preload group) or after (coload group) intrathecal drug injection for spinal anesthesia. Hypotension was defined if systolic arterial pressure decreased below 80% of baseline and ephedrine was administered to treat hypotension. The incidence of hypotension and the total dose of ephedrine were checked. Blood pressure, heart rate and nausea before childbirth were assessed. Neonatal outcomes were evaluated with Apgar scores and umbilical blood gas analysis.

Results

The incidence of hypotension was lower in the coload group compared to the preload group (53% vs. 83%, P = 0.026). The blood pressure showed the bigger drop during spinal anesthesia in the preload group (34 ± 13 vs. 25 ± 10 mmHg, P = 0.002) and smaller dose of ephedrine was required in the coload group (7.5 [0–30] vs. 15 [0–40] mg, P = 0.015). The incidence of nausea was also lower in the coload group (27% vs. 60%, P = 0.019). Neonatal outcome measures were comparable between two groups.

Conclusions

In case of using crystalloids for cesarean delivery, coload is more effective than preload for the prevention of maternal hypotension after spinal anesthesia.

Trial registration

Clinical Research Information Service KCT0000324 (Jan 12^th, 2012)

A prospective observational study of stroke volume responsiveness to a passive leg raise manoeuvre in healthy non-starved volunteers as assessed by transthoracic echocardiography

Current guidelines for intra-operative fluid management recommend the use of increments in stroke volume following intravenous fluid bolus administration as a guide to subsequent fluid therapy. To study the physiological premise of this paradigm, we tested the hypothesis that healthy, non-starved volunteers would develop an increment in their stroke volume following a passive leg raise manoeuvre. Subjects were positioned supine and stroke volume was measured by transthoracic echocardiography at baseline, 30 s, 1 min, 3 min and 5 min after passive leg raise manoeuvre to 45°. Stroke volume was measured at end-expiration during quiet breathing, as the mean of three sequential measurements. Seventeen healthy volunteers were recruited; one volunteer in whom it was not possible to obtain Doppler measurements and a further five for reasons of poor Doppler image quality were not included in the study. Mean (SD) percentage difference from baseline to the largest change in stroke volume was 5.7 (9.6)% (p = 0.16). Of the 11 volunteers evaluated, five (45%) had stroke volume increases of greater than 10%. Mean (SD) maximum percentage change in cardiac index was 14.8 (9.7)% (p = 0.004). A wide variation in baseline stroke volume and response to the passive leg raise manoeuvre was seen, suggesting greater heterogeneity in the normal population than current clinical guidelines recognise.

Colloid cohydration and variable rate phenylephrine infusion effectively prevents postspinal hypotension in elective Cesarean deliveries

Background:

Prevention of post-spinal hypotension in obstetric patients can be accomplished using intravenous fluid expansion and prophylactic use of sympathomimetic drugs. The affect of combination of colloids and phenylephrine infusion on maternal hemodynamics has not been widely studied and there is no consensus about the dosage required and time of starting its administration.

Materials and Methods:

This prospective, randomized, double-blind study enrolled 90 healthy term parturients undergoing elective Cesarean delivery under lumbar subarachnoid block (0.5% hyperbaric bupivacaine 10 mg with fentanyl 25 μg). Patients in Group A received prophylactic intravenous phenylephrine infusion (60 μg/minute) along with hydroxyl-ethyl-starch cohydration (6% HES 130/0.42;15 ml/kg) immediately after subarachnoid block. In Group B, patients received 6% HES cohydration and intermittent intravenous 50 μg boluses of phenylephrine. The efficacy of these in maintaining maternal SBP at 90-110% of baseline and neonatal well-being was evaluated.

Results:

In Group B, 75.5% of patients required rescue phenylephrine boluses to maintain SBP while maternal hemodynamics were well maintained in Group A and rescue drug was not needed. Reactive hypertension occurred in one patient (2.2%) and bradycardia in two patients (4.4%) in Group A. Six patients complained of nausea in Group B (13.3%) compared to one in Group A. All the newborns had normal Apgar scores and Umbilical arterial pH > 7.2.

Conclusion:

A combination of colloid cohydration and prophylactic phenylephrine infusion initiated at 60 μg/minute maintained maternal hemodynamics and neonatal well-being during Cesarean deliveries requiring minimum interventions by the anesthesiologist.

Crystalloid and colloid preload for maintaining cardiac output in elderly patients undergoing total hip replacement under spinal anesthesia

The aim of the present study was to compare the effects of colloid and crystalloid preload on cardiac output (CO) and incidence of hypotension in elderly patients under spinal anesthesia (SA). A randomized, double-blinded study was conducted including 47 elderly patients undergoing scheduled total hip replacement (THR), who were randomized to three groups: the control group (C group, n = 15), crystalloid (RS group, n =16) and colloid group (HES group, n = 16). An intravenous preload of 8 mL/kg of either lactated Ringer's solution in the RS group or 6% hydroxyethyl starch in the HES group was infused within 20 min before SA induction, while no intravenous preload was given in the C group. There was a trend of decrease in CO and systolic blood pressure after SA with time in the C group. In the RS and HES groups, CO increased significantly after fluid preloading as compared with baseline (P < 0.01). Thereafter, CO remained higher than baseline until 30 min after SA in the HES group. The change of systolic blood pressure was similar to CO, but no significant difference from baseline was observed in each group. Hypotension occurred in 3 patients in the C group and one each in the RS and HES group, respectively (P = 0.362). Intravascular volume preload with colloid is more effective than crystalloid solution in maintaining CO, which may be improved the hemodynamic stability in elderly patients during SA.

Colloid or crystalloid solution on maternal and neonatal hemodynamics for cesarean section: a meta-analysis of randomized controlled trials

AIM

To compare the effect of colloid and crystalloid on maternal and neonatal hemodynamics in cesarean section.

MATERIAL AND METHODS

We searched MEDLINE (PubMed, 1966-2011), EMBASE (1974-2011), http://www.clinicaltrials.gov, the Cochrane Controlled Clinical Trials Register Database, Biosis Preview, and the Chinese Biomedical Database (1980-2011). Randomized controlled trials involving healthy term patients undergoing scheduled cesarean delivery that compared the effect of colloid and crystalloid on hypotension, need for vasopressors, cardiac output, neonatal outcomes, and other adverse effects were analyzed.

RESULTS

Ten trials of 853 patients were eligible for analysis. When colloid was used, significantly fewer hypotensive events occurred (odds ratio [OR] 3.21, 95% CI 2.15-4.53, number needed to treat = 4), less demand for vasopressors (standard mean difference [SMD] 0.77, 95% CI 0.34-1.21) and improved cardiac output (SMD -1.08, 95% CI -2.00 - -0.17). In subgroup analysis, the use of colloid reduced hypotensive events and adverse effects in Asian patients.

CONCLUSION

Colloid hydration should be considered first, especially in Asian patients, focusing on dosage and type of fluids. Preventive or therapeutic vasopressors may be required in a significant proportion of patients.

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.

The median effective volume of crystalloid in preventing hypotension in patients undergoing cesarean delivery with spinal anesthesia

BACKGROUND AND OBJECTIVES

Spinal anesthesia-associated maternal hypotension in Cesarean delivery is the most frequent and troublesome complication, posing serious risks to mothers and compromising neonatal well-being. The effective volume of intravenous crystalloid as the preventive strategy in this context has not been estimated.

METHODS

Eighty-five parturients with ASA physical status I/II undergoing elective Cesarean delivery were screened and 67 eligible women were assigned to receive pre-spinal crystalloid loading. Hyperbaric 0.5% bupivacaine 2mL (10mg) plus morphine 50μg was given to all patients. The volume of crystalloid was determined by an up-and-down sequential method. The crystalloid was infused at a rate of 100-150mL.min(-1) prior to the spinal anesthetic injection. The initial volume of crystalloid was 5mL.kg(-1). Volume-effect data were fitted to a sigmoidal maximum efficacy model and the median effective volume (EV(50)) and corresponding 95% confidence interval (95% CI) were estimated using maximum likelihood estimation and logistic regression with Firth's correction.

RESULTS

A total of 67 subjects completed the study and were analyzed. Twenty-eight (41.8%) patients developed hypotension with their systolic blood pressure (SBP) decreasing > 20% of baseline. The EV(50) of crystalloid were 12.6mL.kg(-1) (95% CI, 11.6 to 14.8mL.kg(-1)). With Firth's correction, the pooled probability of an effective preventive volume of crystalloid at 13mL.kg(-1) was 50.2% (95% CI, 30% to 83.1%).

CONCLUSIONS

The estimated EV(50) of the preloaded crystalloid required to prevent spinal anesthesia-induced hypotension in a Cesarean section is, approximately, 13mL.kg(-1). However, prophylactic or therapeutic vasoconstrictors should also be prepared and administered at an appropriate time.

Fluid and vasopressor management for Cesarean delivery under spinal anesthesia: continuing professional development

PURPOSE

The purpose of this Continuing Professional Development module is to review the physiology of maternal hypotension induced by spinal anesthesia in pregnant women, and the effects of fluids and vasopressors.

PRINCIPAL FINDINGS

Maternal hypotension induced by spinal anesthesia is caused mainly by peripheral vasodilatation and is not usually associated with a decrease in cardiac output. Although the intravenous administration of fluids helps to increase cardiac output, it does not always prevent maternal hypotension. Three strategies of fluid administrations are equivalent for the prevention of maternal hypotension and a reduced need for vasopressors: (1) colloid preload; (2) colloid coload; and (3) crystalloid coload. Crystalloid preload is not as effective as any of those three strategies. Unlike phenylephrine, ephedrine can cause fetal acidosis. Therefore, phenylephrine is recommended as first line treatment of maternal hypotension. A phenylephrine infusion (25-50 μg x min(-1)) appears to be more effective than phenylephrine boluses to prevent hypotension, and nausea and vomiting. In pre-eclamptic patients, spinal anesthesia produces less hypotension than in normal pregnant women and fluid volumes up to 1,000 mL are usually well tolerated. Therefore mild to moderate intravascular volume loading is recommended, keeping in mind the increased risk for pulmonary edema in this population. In pre-eclamptic patients, hypotension can be treated either with ephedrine or phenylephrine, and phenylephrine infusions are not recommended.

CONCLUSION

A volume loading regimen other than crystalloid preload should be adopted. A phenylephrine infusion during elective Cesarean delivery is beneficial for the mother and safe for the newborn.