Abstract
This article offers a comprehensive clinical update on best practices for neuraxial and general anesthesia in cesarean delivery, the most frequently performed major surgical procedure globally. Current evidence-based strategies to address common anesthetic challenges, such as maternal hypotension and intraoperative breakthrough pain, are discussed in detail. Practical approaches for optimizing maternal hemodynamic stability, including the use of vasopressors, fluid management and maternal positioning, are reviewed. Additionally, the article explores best practices for general anesthesia, with an emphasis on new approaches to prolonging safe apnea time, rapid sequence induction and difficult airway management.
1
Introduction
Cesarean delivery (CD) is the most common surgical procedure in United States (US) and in Europe, comprising 32.1% and 25.7% of deliveries, respectively [ , ]. Although potentially lifesaving for the mother and/or the fetus, there are concerns for overuse of CD and steadily increasing rates worldwide. The worldwide average rate is 21.1%, but rates range from 5% in sub-Saharan Africa to 42.8% in Latin America and the Caribbean [ ]. The leading indications for primary CD include labor dystocia, abnormal or indeterminate fetal heart rate tracing, fetal malpresentation, multiple gestation, and suspected fetal macrosomia [ ].
This article will provide clinical updates regarding best practices for the perioperative management of CD with regional and general anesthesia. Anesthetic care priorities include ensuring maternal physical and psychological comfort and well-being before, during and after delivery. An increasing focus on quality improvement will be highlighted [ , ].
2
Preoperative and intraoperative period
2.1
Preoperative assessment and informed consent
A focused history and physical examination are fundamental to developing an appropriate anesthetic plan. In an emergency, rapid exchange of information between interdisciplinary team members regarding the patient history and condition is crucial, especially if the patient is obtunded or has an altered mental status.
The anesthetic approach is informed by the urgency of surgery, the patient’s medical, surgical, obstetric, allergy, and anesthetic histories. Physical examination should include airway assessment, review of vital signs, a focused evaluation of the cardiovascular and respiratory systems, and examination of the lumbar spine. Patients at an elevated risk of perinatal complications due to preexisting conditions should receive an anesthetic consultation early in the antenatal period to facilitate adequate preparation, investigation, and interdisciplinary team planning. Patient informed consent should be obtained after a discussion of the risks and benefits of the anesthetic options. Shared decision-making promotes patient satisfaction and improved health outcomes [ ].
2.2
Laboratory testing
All pregnant individuals should be screened for anemia [ ]. For low-risk CDs, a blood type and screen should be performed at minimum; cross matching and preparation of blood products may be indicated in the setting of anemia and/or anticipated moderate to high risk of hemorrhage [ ]. Institutional protocols should be developed in conjunction with the local blood bank. Other laboratory studies and imaging should be guided by clinical history. Routine platelet count testing is not necessary in a healthy parturient [ ].
2.3
Fasting and aspiration prophylaxis
Fasting prior to elective surgery is recommended to limit the risk of pulmonary aspiration. American Society of Anesthesiologists (ASA) guidelines dictate a fasting period of 2 h for clear liquids and 6–8 h for solids (at least 6 h following a light meal, and 8 h following fatty food) [ , ]. Extensive periods of fasting risk the development of hypovolemia, metabolic stress and ketosis. The Society for Obstetric Anesthesia and Perinatology (SOAP) enhanced recovery after cesarean (ERAC) consensus statement recommends ingestion of a nonparticulate carbohydrate drink containing 45 g of carbohydrate (e.g., clear apple juice; 16 oz = 473 mL, 56 g of carbohydrate) up to 2 h before CD in nondiabetic parturients, extrapolated from colorectal enhanced recovery after surgery (ERAS) protocols [ ].
The use of pharmacologic gastrointestinal prophylaxis before surgical procedures is variable and includes medication from various classes: nonparticulate antacids to rapidly increase stomach pH for about an hour (e.g., oral sodium citrate-citric acid 30 mL), H2 receptor antagonists (e.g., intravenous (IV) famotidine 20 mg), prokinetic agents (IV metoclopramide 10 mg) and proton pump inhibitors (e.g., IV pantoprazole 40 mg). These medications should be administered 30–40 min in advance to be most effective [ ]. A combination of agents may have higher effectiveness than a single agent.
2.4
Intravenous access
Large bore IV access with a 16- to 18-gauge catheter is used for routine elective CD [ ]. Additional catheters, including rapid infusion catheters or central venous access may be indicated based on hemorrhage risk, to facilitate co-administration of non-compatible medications, or facilitate a dedicated line for agents such as insulin.
Preparation for hemorrhage, including use of quantitative blood loss estimation is well described in consensus bundles on obstetric hemorrhage [ ]. It is beyond the scope of this article to discuss obstetric hemorrhage in detail.
2.5
Monitoring
Standard ASA monitors should be used. Pulse oximetry, electrocardiography, noninvasive blood pressure and heart rate measurement should be performed. Maintaining intraoperative normothermia is a quality metric at most institutions; hence temperature measurement is also warranted. Skin, axillary or bladder temperature probes are options in the awake patient under spinal anesthesia [ ].
Active warming and maintaining operating room temperatures >72° F (22° C) are Class 1 recommendations of the SOAP ERAC pathways [ ]. Special monitors and invasive lines should be placed as needed before or after induction of anesthesia.
Healthy parturients do not require supplemental oxygen intraoperatively with neuraxial blockade [ ]. Oxygen should be applied if oxygen saturation drops under 95%. A fetal heart rate check should be performed immediately after induction of neuraxial anesthesia, and documented prior to abdominal preparation for CD.
2.6
Sedating medications
Sedating medications are typically avoided during CD to limit depressant effects for the fetus and maternal amnesia. However, small doses of sedative medications such as midazolam 0.02 mg/kg IV or 30–50% nitrous oxide may be safely administered when needed [ ]. Furthermore, some medications administered for other reasons that have sedating effects can be favorable to address intraoperative maternal anxiety, for example, IV dexmedetomidine 10 up to 30 mcg for maternal shivering and IV promethazine 25 mg for nausea [ ].
2.7
Antibiotic prophylaxis
Single dose first-generation cephalosporins (e.g., IV cefazolin 1–2g for patients <80 kg or >80 kg respectively) are the first-line antibiotic unless allergies exist [ ]. A higher dose is recommended (IV cefazolin 3g) for patients >120 kg. Alternatively, a single-dose combination of clindamycin and an aminoglycoside can be administered preoperatively. Antibiotic prophylaxis is recommended for all CDs within 60 min before the start of surgery unless the patient is already receiving antibiotics with an equivalent spectrum coverage, e.g., for chorioamnionitis [ ]. If not administered, such as in an emergency, antibiotics should be given as soon as possible after surgical incision. Surgical antimicrobial standards further dictate redosing antibiotics within 2 half-lives of the agent or at > 1500 mL blood loss [ ]. Extended-spectrum antibiotics such as azithromycin 500 mg, infused over 1 h are recommended for nonelective CD, but this remains debated [ ].
2.8
Intraoperative/postoperative nausea and vomiting prophylaxis
Steps to prevent intra- and postoperative nausea and vomiting include avoiding hypotension, avoiding uterine exteriorization and administering a combination of prophylactic IV agents, including a 5-HT3 antagonist such as ondansetron 4 mg, or a glucocorticoid such as dexamethasone 4–8 mg [ ].
2.9
Uterine contractility
To promote uterine contractility after delivery, international consensus recommendations are to provide a small initial bolus of oxytocin, followed by an infusion that is titrated to effect [ ]. Equipotent doses of carbetocin produce similar effects, without need for an infusion. Higher doses are required for intrapartum CD and likely also for patients with risk factors for uterine atony. Early consideration should be given to second-line agents (such as ergot alkaloids or prostaglandins) in the setting of inadequate tone with first-line agents [ ].
2.10
Non-neuraxial postoperative analgesia
Nonopioid analgesia is recommended to be administered in the operating room unless contraindicated. This includes IV ketorolac 15–30 mg or IV ketoprofen 50–100 mg after closure of the peritoneum and use of IV or oral acetaminophen (paracetamol) 1000 mg [ ]. In the postoperative period, scheduled non-opioid analgesics such as oral ibuprofen q6h and oral acetaminophen 650–1000 mg q6h should be established. As-needed systemic opioids should be prescribed for breakthrough pain not responsive to non-opioid analgesics. Oral opioids such as oxycodone or hydrocodone should be preferentially prescribed unless the patient is intolerant of oral intake since greater opioid side effects are associated with the IV route of administration [ ].
Local anesthetic wound infiltration, field blocks such as Ilio-inguinal, ilio-hypogastric blocks and fascial plane blocks such as transversus abdominis plane, quadratus lumborum, and erector spinae blocks should be considered when neuraxial morphine or an alternate long-acting opioid is not administered [ ].
3
Optimal anesthesia
3.1
Neuraxial anesthesia
Neuraxial anesthesia is preferred over general anesthesia for CD unless contraindicated, and includes single-shot and continuous spinal, epidural, combined spinal and dural puncture epidural techniques [ ]. In the United Kingdom (UK) about 92% of CDs are conducted under neuraxial anesthesia [ ]. The advantages over general anesthesia are (i) psychosocial – the ability to witness the delivery, facilitate presence of a support person and early maternal-neonatal bonding, and (ii) clinical – the avoidance of airway instrumentation, reduced risk of adverse anesthetic outcomes, lower risk of surgical site infection, deep venous thrombosis and pulmonary embolism, superior postoperative pain control, and lower risk of cardiac arrest and death [ , ]. The advantages of spinal anesthesia over epidural anesthesia include more rapid onset of the desired T4 – T6 sensory blockade, and more profound and reliable blockade [ ].
Bupivacaine, a long-acting local anesthetic, is the most common intrathecal agent used for CD [ ]. The hyperbaric form co-administered with opioids (ED95 11.2 mg for success) [ ] and isobaric form [ED95 13 mg for success] [ ] are similarly effective, although some evidence suggests more rapid sensory block onset with the hyperbaric formulation and one randomized control trial (n = 76) reported faster motor blockade onset and resolution with hyperbaric vs. plain intrathecal bupivacaine 9 mg with fentanyl [ ]. Clonidine and other adjuncts may be added to intrathecal solutions, particularly when prolonging the duration of spinal anesthesia is desired without resorting to a CSE technique [ ].
Less hypotension occurs with lower intrathecal doses of bupivacaine but risks intraoperative pain; a CSE technique is recommended if intrathecal bupivacaine doses lower than 10–11 mg are contemplated, or for anticipated long or complex surgical techniques [ ]. The presence of an epidural catheter facilitates raising of an inadequate level and extending the duration of the block. Modified techniques are of value in high-risk patients who may not be able to tolerate the acute onset of cardiopulmonary effects of a sympathectomy or where the sensory level may be difficult to predict, such as individuals at the extremes of height or weight. With a sequential CSE, a lower amount of spinal medication is administered, followed by 3–5 mL epidural doses of 2% lidocaine to achieve the desired level.
Continuous spinal catheter techniques are uncommon and typically utilized only after inadvertent dural puncture with an epidural needle. They may be intentionally placed for high-risk cases, the value being the ability to titrate or incrementally dose intrathecal medications to the desired effect [ ].
Epidural anesthesia is infrequently used as the initial intraoperative approach and is more commonly an extension of an in-situ catheter placed for labor analgesia. Epidural surgical anesthesia is typically achieved with titrated 5-mL doses of local anesthetic agents via the catheter after a test dose has been performed. The most commonly used agents are 2% lidocaine plain or with epinephrine 1:200,000, 0.5–0.75% ropivacaine and 3% 2-chloroprocaine, with a volume of 15–25 mL typically administered to achieve a T4 to T6 sensory level [ ]. Onset of anesthesia occurs within 5–10 min and may be hastened with lidocaine by the addition of sodium bicarbonate 8.4% 2 mL/20 mL of local anesthetic.
In an emergency, 3% 2-chloroprocaine 15–20 mL is used for rapid extension of epidural anesthesia, with greater safety margin with respect to local anesthetic systemic toxicity in case of inadvertent intravascular injection. With respect to block onset time, a non-inferiority study of 3% 2-chloroprocaine versus a mixture of 2% lidocaine, 150 mcg of epinephrine, 2 mL of 8.4% bicarbonate, and 100 mcg of fentanyl was inconclusive [ ].
3.1.1
Opioid adjuvants
Local anesthetic agents are typically co-administered with opioids to improve the quality of intraoperative anesthesia and postoperative analgesia. The short-acting opioids adjuvants most commonly used are fentanyl (intrathecal dose 10–25 mcg, epidural dose 50–100 mcg) or sufentanil (intrathecal dose 2.5–5 mcg, epidural dose 10 mcg). Fentanyl or sufentanil decrease the need for intraoperative supplemental analgesia and nausea/vomiting [ ]. The most commonly used long-acting opioid is morphine (intrathecal dose 50–300 mcg, epidural dose 2–3 mg) [ , ]. Intrathecal diamorphine 300 mcg or epidural diamorphine 2–3 mg are recommended by the National Institute of Health and Care Excellence (NICE) guidelines as an alternative to morphine [ ], and epidural hydromorphone 0.6–1.0 mg is another alternative [ ]. Long-acting opioids such as intrathecal morphine produce postoperative analgesia lasting 13–33 h [ ]; although the 50-mcg morphine dose has shown similar effectiveness to the 100 and 150 mcg dose with less pruritus and also likely less risk of respiratory depression, higher doses may benefit patients anticipated to have more severe pain, such as patients with a history of chronic pelvic pain [ ].
The SOAP task force suggests that no further respiratory monitoring is needed in low-risk healthy parturients beyond routine institutional postoperative CD monitoring after administration of ultra-low-dose neuraxial morphine (≤0.05 mg (50 mcg) intrathecally or ≤1 mg epidurally) [ ]; in Europe, no further respiratory monitoring is usually implemented for intrathecal dose of morphine up to 0.1 mg (100 mcg) for low-risk healthy non-obese parturients [ ]. After administration of low-dose neuraxial morphine (>0.05 mg and ≤0.15 mg intrathecally or >1 mg and ≤3 mg epidurally), the SOAP task force suggests respiratory rate and sedation measurement every 2 h for 12 h [ ]. High-risk patients or patients with relatively high doses of neuraxial morphine (>0.15 mg intrathecally or >3 mg epidurally) should have respiratory monitoring at least once per hour for the first 12 h and at least once every 2 h from 12 to 24 h after administration [ , ].
3.1.2
Testing the adequacy of the block
Appropriate sensory level testing is crucial to determine the adequacy of blockade prior to starting surgery. The rapid and dense block from spinal anesthesia is easier to assess than epidural anesthesia; assessment may be particularly challenging if a catheter previously used for labor analgesia has been dosed to provide a surgical anesthetic.
The onset of sensory blockade to cold occurs before and at a higher level than pinprick, and both before and higher than touch, corresponding to inhibition of C, A delta and A beta fibers respectively [ ]. For this reason, light touch has been advocated as primary testing modality [ ]. Motor block assessment tests efferent function and can be used to supplement the evaluation of block adequacy. Lumbosacral plexus motor blockade may be crudely assessed with a modified Bromage score; the ability to straight leg raise indicates inadequacy of the block. Evidence of S1 block (plantar flexion) is common with spinal anesthesia but infrequent with epidural anesthesia. Inadequate sacral anesthesia may be present if normal ankle motor function is observed and is likely to result in intraoperative pain [ ].
3.1.3
Intraoperative pain
Breakthrough pain may occur despite an apparently adequate block. Intraoperative pain risks negative psychological consequences, including post-traumatic stress disorder, and is a cause of successful medicolegal claims [ ]. The Obstetric Anaesthetists’ Association recommends that the upper and lower limit of the sensory block and motor block should be tested, that complaints of pain should be acknowledged and managed with IV supplementation of opioids that have rapid onset including fentanyl or remifentanil with low-dose ketamine. Conversion to general anesthesia should be discussed with the patient and performed if effective analgesia is not achieved [ ].
3.2
Hemodynamic control during CD under spinal anesthesia
Spinal anesthesia for CD causes a very extensive sympathetic blockade, which commonly results in maternal arterial hypotension. In the absence of prophylactic treatment, it occurs in 50–90% of cases [ , ]. The occurrence of maternal nausea-vomiting (often accompanied by dyspnea) is closely correlated with these hemodynamic variations [ ] and profound and/or prolonged maternal low blood pressure could have a negative impact on neonatal pH and/or can be associated with transient tachypnea of the newborn [ ]. Other maternal side effects due to hypotension can be as severe as loss of consciousness, pulmonary aspiration, cardiovascular collapse and myocardial infarction. Therefore, one of the anesthesiologist’s main goals during CD is to avoid hypotension or to correct it promptly to minimize maternal and neonatal morbidity. Many definitions of maternal hypotension have been used in the literature. Even though mean arterial pressure (MAP) is a major physiological determinant of organ perfusion, one of the most widely used definition of hypotension is maternal systolic blood pressure (SBP) less than 80% of the baseline SBP value measured prior to spinal anesthesia induction (i.e., a 20% decrease from baseline). This definition has been endorsed by the 2018 International Consensus Statement on the Management of Hypotension with vasopressors during CD under spinal anesthesia [ ].
The goal of hemodynamic optimization during CD is to maintain organ perfusion pressure and sufficient oxygen supply to maternal tissues and to the fetus by targeting blood pressure, on an individualized basis. Several strategies can optimize maternal hemodynamics. While contemporary use of norepinephrine or phenylephrine prophylaxis can nearly eliminate maternal hypotension in isolation during spinal anesthesia for CD, we recommend adjunctive methods to lower the total maternal exposure to vasopressors and further improve hemodynamic control. Vasopressors and crystalloid co-loading at least should be combined to better prevent both hypotension occurrence and its severity. The benefit of adding left lateral tilt, ondansetron and/or lower limb compression is more debated.
3.2.1
Vasopressors (see Table 1 )
3.2.1.1
History
Ephedrine was the vasopressor of choice to treat and/or prevent maternal hypotension during CD for decades. Early animal studies in pregnant ewes comparing IV ephedrine to alpha-agonists demonstrated that ephedrine increased uterine blood flow without increasing uterine vascular resistance [ , ]. However, subsequent studies in pregnant women suggested high placental transfer of ephedrine leading to a beta-adrenergic-mediated increase in CO 2 and lactate production [ , , ], particularly with doses above 15 mg [ ]. With this finding, alpha-agonists were reintroduced in the 1990s despite initial reluctance, and one study using phenylephrine in combination with ephedrine demonstrated less maternal hypotension and better neonatal arterial pH values compared to ephedrine alone [ ].
| Vasopressor Concentration | Infusion Rate at spinal induction | Increasing/decreasing dose increment | Bolus rescue for severe or symptomatic hypotension | Goal |
|---|---|---|---|---|
| NOREPINEPHRINE a 5 mcg/mL | 30 mL/h = 2.5 mcg/min | ±10–20 mL/h | 2.5–5 mcg | SBP maintained >90% of baseline SBP |
| PHENYLEPHRINE 100 mcg/mL | 30 mL/h = 50 mcg/min | ±10–20 mL/h | 50-100 mcg | |
| EPHEDRINE 3 mg/mL | 0 | 0 | 3–9 mg for hypotension with bradycardia, maximum total dose = 15 mg |
a Norepinephrine (NE) concentration is expressed here as NE base, which is twice as potent as when it is expressed as NE bitartrate (i.e., 5 mcg/mL of NE base = 10 mcg/mL of NE bitartrate) [ , ].
Subsequent studies highlighted the superiority of phenylephrine over ephedrine regarding hemodynamic control [ , ]. A widespread adoption of phenylephrine for spinal hypotension was confirmed with 2 meta-analyses in the 2010s [ , ] and it has been recommended since 2018 by an international consensus statement in this context [ ]. Nevertheless, phenylephrine as a powerful alpha-agonist effect can lead to maternal bradycardia in response to high afterload in up to 50% of cases [ ], with potential associated reduction in maternal cardiac output.
Norepinephrine, named noradrenaline in the EU, has been evaluated as an alternative to phenylephrine since 2015, with mild beta-agonist properties that may limit reactive maternal bradycardia [ ]. With favorable efficacy and safety data from recent randomized controlled trials (RCTs) and meta-analyses[ ], the use of norepinephrine has increased for the prevention of maternal hypotension during CD under spinal anesthesia.
3.2.1.2
Vasopressor mode of administration
Vasopressors can be administered prophylactically from the induction of spinal anesthesia to prevent hypotension, or therapeutically to treat hypotension once it occurs. Data on the neonatal benefits (Apgar, arterial pH, base excess) of prophylactic maternal spinal hypotension prevention before delivery are relatively scarce, and suggest only mild benefit of prophylaxis with the alpha-agonist phenylephrine [ ]. Conversely, many studies comparing these two strategies using either phenylephrine or norepinephrine clearly show lower maternal morbidity with a prophylactic strategy: less hypotension, nausea/vomiting, tachycardia, dizziness and shortness of breath [ , ].
3.2.1.3
Choice of vasopressor
Two meta-analyses have demonstrated that ephedrine is less effective in preventing hypotension than phenylephrine and norepinephrine [ , ], and a network meta-analysis with vasopressor ranking also suggested that ephedrine is the least effective vasopressor in preventing maternal hypotension [ ]. Furthermore, two meta-analyses showed that ephedrine was much less effective than phenylephrine to prevent neonatal acidosis [ , ]. These data should therefore discourage anesthesiologists from using ephedrine as a prophylactic vasopressor during CD.
Conversely, data on the phenylephrine efficacy are clearly favorable: a meta-analysis has shown that the incidence of hypotension is lower with phenylephrine than placebo or no vasopressor [ ], and these results were confirmed by two subsequent RCTs [ , ]. Phenylephrine also reduced the incidence of maternal nausea and vomiting [ ] and improved neonatal arterial lactatemia in comparison with placebo or no vasopressor [ ].
Since the international consensus statement guideline recommendation for phenylephrine in 2018, new studies have confirmed that prophylactic norepinephrine is also an effective strategy to prevent maternal spinal hypotension. Indeed, 3 RCTs have shown a lower incidence of hypotension with prophylactic norepinephrine than placebo or no vasopressor [ ].
3.2.1.4
Should norepinephrine replace phenylephrine for optimal hemodynamic management?
Available safety data about low concentration/dilute norepinephrine (5–10 μg/mL) are reassuring. Even if some reluctance exists about norepinephrine use through peripheral venous catheters due to fear of ischemic complications in case of extravasation, ischemic risk with norepinephrine is similar to phenylephrine at equipotent concentrations, and several large-scale operating room/intensive care unit (ICU) studies have shown a low incidence of extravasation and severe complications [ ].
Two meta-analyses and a more recent RCT demonstrated a lower incidence of maternal bradycardia with norepinephrine compared to phenylephrine [ , , ]. In addition, two other RCTs suggested a significantly higher maternal cardiac output with norepinephrine than phenylephrine [ , ]. Despite these data in favor of norepinephrine, there is a substantial body of literature showing a similar impact of phenylephrine and norepinephrine on more clinically relevant outcomes, especially hypotension and neonatal well-being. Two meta-analyses showed that the incidence of hypotension did not differ between the 2 vasopressors [ , ] and this was confirmed by a subsequent RCT [ ]. In addition, one meta-analysis and 3 subsequent RCTs showed that neonatal 5-min Apgar scores were similar between phenylephrine and norepinephrine groups[ , ]; many studies also suggested no difference in terms of arterial pH [ , , , ] and base excess [ ] between these two vasopressors. A potential downside of norepinephrine is the risk of drug dilution error if prepared from concentrated vials manufactured for the ICU. Use of pre-made compounded dilute solutions may minimize the risk of dosing errors.
Overall, even if norepinephrine efficacy and its specific benefits on maternal bradycardia and cardiac output are well documented and make it a suitable alternative to phenylephrine [ ], current data are still insufficient to strongly recommend norepinephrine over phenylephrine for the hemodynamic management of CD under spinal anesthesia.
3.2.2
Fluid loading
Crystalloid fluids are rapidly distributed in the interstitial space during pre-loading, while their volume expansion power is better in rapid co-loading just after intrathecal injection of local anesthetics due to the vasodilation induced by the sympathetic block. While a low volume (500 mL) of Hydroxy-Ethyl-Starches in pre-loading had proven efficacy on hemodynamic control in a multicenter study, it can no longer be recommended due to safety concerns in ICU setting issued by both the Federal Drug Agency (FDA) and the European Medicines Agency (EMA) [ ]. Therefore, only crystalloid co-loading can be recommended. One study has evaluated the efficacy of crystalloid co-loading (2 L) in conjunction with the use of prophylactic phenylephrine. Compared to phenylephrine prophylaxis alone, it showed a significant decrease in the incidence of hypotension (1.9 vs 28.3%, p = 0.0001) and phenylephrine requirement (1160 vs 1400 μg, p = 0.008) although no further benefit on neonatal parameters [ ]. Similarly, crystalloid co-loading combined to norepinephrine prophylaxis also decrease norepinephrine requirement [ ].
It is therefore relevant, in the current state of the literature and regulatory data, to recommend the use of crystalloid co-loading. In view of the potentially negative impact of overload on early post-CD rehabilitation strategies including early removal of urinary catheter in PACU whenever possible in uneventful CD, crystalloid co-loading should be limited to 500–1000 mL and infused quickly within the first 5–10 min after the induction of spinal anesthesia.
3.2.3
Other measures that may optimize hemodynamic control
3.2.3.1
Uterine displacement
When pregnant women in the third trimester are lying in the supine position, the enlarged uterus may compress the inferior vena cava (IVC), thereby reducing venous return and resulting in hypotension in 10% of women [ ]. This IVC compression may aggravate the decrease in preload induced by spinal anesthesia and may increase both the incidence and the severity of hypotension. Left-sided tilt may reduce the pressure on the IVC, thereby improving venous return and therefore maternal cardiac output, uterine blood flow and fetal oxygen supply.
Lee et al. measured cardiac output, stroke volume and systemic vascular resistances by suprasternal Doppler ultrasound in term healthy parturients with four angles of left lateral tilt (0°, 7.5°, 15° and 90°) and showed that aortocaval compression can be effectively minimized with 15° or greater [ ]. It is thus recommended in many anesthesiology references. Nevertheless, this dogma has been challenged over the past few years [ ]. A landmark RCT using prophylactic phenylephrine and crystalloid co-loading failed to find benefit of 15° left-sided tilt position neither on neonatal status nor on systolic blood pressure (SBP); nevertheless, 15° left lateral tilt reduced phenylephrine requirement and improved maternal cardiac output [ ]. This was confirmed in another study when using 15° left lateral tilt; whereas incidence of hypotension was decreased only with 30° left lateral tilt [ ]. Importantly, these findings may not be generalizable to emergency situations or non-reassuring fetal status [ ]. Moreover, impact of such measures on maternal side effects such as nausea, vomiting, dyspnea, have not been studied.
Thus, it is now suggested that tilt position may not be necessary during elective CD of healthy women with uncomplicated pregnancies if maternal blood pressure is adequately supported with vasopressors and a fluid co-load [ ]. An alternative may be to maintain the tilt position at onset of sympathetic blockade, but then removing it partly or fully at skin incision if well tolerated hemodynamically and requested by the obstetrician or the parturient [ ].
3.2.3.2
Ondansetron
One meta-analysis in 2020 (8 studies, 740 women) found that intravenous ondansetron given before spinal anesthesia was more effective than placebo to prevent hypotension requiring treatment (RR 0.67, 95% CI 0.54 to 0.83) [ ]. Nevertheless, the studies provided low-quality evidence and also did not include a vasopressor prophylaxis with either phenylephrine or norepinephrine, nor a crystalloid co-loading. When combining norepinephrine prophylaxis and crystalloid co-loading, ondansetron decreased norepinephrine requirement but no differences were found in the incidence of hypotension, bradycardia, and more surprisingly nausea and vomiting [ , ]. Earlier or later intravenous injection of ondansetron (i.e., 15 vs. 5 min prior to spinal anesthesia) did not affect the dose of phenylephrine needed to prevent spinal hypotension [ ].
The inconsistency of ondansetron to decrease the incidence of hypotension and bradycardia, and to a less extent the vasopressor requirements or even nausea and vomiting, prevent strong recommendation for its routine use before spinal anesthesia to avoid hypotension [ , ].
3.2.3.3
Lower limb compression
Different methods to achieve lower extremity compression such as bandages, stockings and inflatable devices have been assessed. Lower limb compression has been found more effective than control (no compression) for preventing hypotension (average RR 0.61, 95% CI 0.47–0.78) in 11 studies including 705 women, but the quality of evidence remains very low because of the studies’ heterogeneity [ ]. In addition, those preventive measures are not convenient to implement for most institutions on a routine basis.
3.3
General anesthesia
Despite the strong preference for neuraxial anesthesia for CD, general anesthesia is indicated in certain scenarios ( Table 2 ). CD rates have decreased in recent decades and there is a lack of consensus about the ideal rate of general anesthesia. An analysis of the US National Anesthesia Clinical Outcomes Registry found an overall general anesthesia rate of 5.8% for all CDs and of 14.6% for emergent CDs [ ].
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