Positional Blood Pressure Change and the Risk of Hypotension During Spinal Anesthesia for Cesarean Delivery

Risk factors of more severe hypotension after spinal anesthesia for cesarean section

BACKGROUND

The aim of this study was to examine the risk factors associated with the use of vasopressors to prevent hypotension that occurs after spinal anesthesia during cesarean section. Although the prophylactic use of vasopressors is already suggested as routine care in many parts of the world, the occurrence of spinal anesthesia-induced hypotension (SAIH) is still common in parturients.

METHODS

This retrospective study included parturients receiving elective cesarean deliveries under spinal anesthesia from April 2016 to March 2020. Risk factors related to ephedrine dosage were analyzed using a hurdle model, and risk factors related to SAIH were further analyzed with logistic regression.

RESULTS

Five risk factors, namely maternal body mass index (BMI, p < 0.001), baseline systolic blood pressure (SBP, p < 0.001), baseline heart rate (HR, p = 0.047), multiparity ( p = 0.003), and large fetal weight ( p = 0.005) were significantly associated with the requirement for ephedrine. Furthermore, a higher ephedrine dosage was significantly associated with maternal BMI ( p < 0.001), baseline SBP ( p < 0.001), baseline HR ( p < 0.001), multiparity ( p = 0.027), large fetal weight ( p = 0.030), maternal age ( p = 0.009), and twin pregnancies ( p < 0.001). Logistic regression analysis also showed that the same five risk factors-maternal BMI ( p = 0.030), baseline SBP ( p < 0.001), baseline HR ( p < 0.001), multiparity ( p < 0.001), and large fetal weight ( p < 0.001)-were significantly associated with SAIH, even in cases where vasopressors were administered.

CONCLUSION

These findings can be useful for clinicians when deciding the dose of prophylactic ephedrine or phenylephrine to prevent SAIH.

Risk Factors in Administering Spinal Anesthesia: A Comprehensive Review

Numerous advantages, including a quick start and consistent anesthesia, are provided by spinal anesthesia, a method often utilized in contemporary medicine for various surgical operations. However, it has some hazards, just like any medical procedure. With an emphasis on identifying and assessing the risk factors associated with administering spinal anesthesia, the review analyzes published literature and clinical investigations carried out in the field of anesthesia. Various key factors, including technique-related procedural and patient-related aspects, can influence the effectiveness of spinal anesthesia. Among these factors are age, sex, body mass index, concurrent conditions (such as cardiovascular disease, diabetes, and respiratory problems), pre-existing neurological issues, allergies, and a history of adverse responses to anesthesia drugs. Additionally, the chance of problems might be increased by physical abnormalities or malformations in the spinal canal and vertebral column. The safety and effectiveness of spinal anesthesia depend significantly on procedural factors, such as the type and dosage of anesthesia agents administered and the patient's position and alignment maintained during the entire surgical procedure and the injection rate. Increased risks can also be caused by inadequate monitoring and a slow response to unfavorable circumstances. Risk factors related to the technique include the expertise and competency of the anesthesiologist or medical professional carrying out the procedure. Inadequate post-procedure monitoring, inadvertent dural puncture, and improper needle placement might lead to complications during or after the spinal anesthesia administration. This review emphasizes the need for a complete preoperative assessment, suitable patient selection, and rigorous procedural planning to reduce the likelihood of problems during the administration of spinal anesthesia. It also emphasizes the significance of ongoing monitoring and timely management of adverse events to guarantee patient safety and the best results. Healthcare professionals may put preventative measures in place and follow best practices to limit possible consequences efficiently by recognizing the risk factors associated with spinal anesthesia. This review helps encourage safer anesthesia practices and improve patient care as medical knowledge and technology advance. However, further study and evidence-based recommendations are required to enhance patient outcomes and risk assessment.

Comparison of the hemodynamic changes between preeclamptic and normotensive parturients who underwent cesarean section under spinal anesthesia at North Showa zone public hospitals, Oromia region, Ethiopia, 2022: a prospective cohort study

BACKGROUND

Spinal anaesthesia complicates maternal hemodynamic and may expose the parturient to dangerous cardiovascular problems. Up to 7% to 89.2% of pregnant women can suffer from spinal anaesthesia-related hypotension. The aim of this study to compare the hemodynamic changes between preeclamptic and normotensive parturients who underwent caesarean section under spinal anaesthesia at North Showa Zone Public Hospitals, Oromia Region, from February 15 to May 15, 2022.

METHODS

A prospective cohort study was conducted on a total of 140 parturients (70 in each group) who underwent cesarean delivery under spinal anesthesia. The study participants were chosen using a consecutive sampling technique. Data were collected from patient charts and intraoperative observations and entered into the Epi Data software version 4.6 and exported to the Statistical Package for the Social Sciences version 25 software. Hemodynamic change = (baseline value-current value/baseline value) * 100. The independent t-test, Mann-Whitney U test, two ways mixed ANOVA, chi-square, and Fisher's exact test was used to analyze the data as appropriate. A P < 0.05 was statistically significant.

RESULTS

The mean percentage change in SBP, DBP, and MAP after spinal anaesthesia was a statistically significant difference between the normotensive and preeclamptic groups, except MAP at 15 min was comparable between the two groups with p = 0.638. The proportion of preeclamptic parturients who develop hypotension was 47%, compared to 74% of normotensive parturients, and the RR of developing hypotension, if participants were preeclamptic, was 0.63, with a 95% confidence interval of 0.412 to 0.978 and a p = 0.039. The mean change in heart rate during the first 15 min was comparable between the groups.

CONCLUSION

In contrast to normotensive parturients undergoing caesarean section under spinal anaesthesia, our study found that the hemodynamic change was lower in preeclamptic parturients. The proportion of preeclamptic women who develop hypotension was 47%, compared to 74% of normotensive parturients.

A Study of the Clinical Effects of Sequential Combined Spinal Epidural Anesthesia and Spinal Anesthesia in Patients Undergoing Orthopedic Surgeries

BACKGROUND

In orthopedic surgeries, there has been an increase in the usage of the neuraxial blockade to provide excellent surgical conditions and prolonged postoperative analgesia. The introduction of the sequential combined spinal epidural anesthesia (SCSEA) technique provides benefits for both spinal anesthesia (SA) and epidural anesthesia. The focus of this study was to analyze the time needed to attain a desired level of sensory block, to compare the period of sensory block, and to study the intraoperative hemodynamics in the SCSEA and SA groups.

MATERIALS AND METHODS

The study was conducted on patients admitted for elective lower limb orthopedic surgeries. The sample size for this prospective randomized study is two groups of 67 subjects each. Patients aged between 18 and 65 years, posted for orthopedic surgeries for two to three hours, and of American Society of Anaesthesiologists (ASA) Grades 1 and 2 were included and divided into two groups. Group A patients received SCSEA with an epidural-test dose of 3 ml lignocaine (2%) with adrenaline and spinal bupivacaine (0.5%) of 1.5 ml-7.5 mg + fentanyl .25 mic if the sensory level was below T8. An epidural top-up was given with 2 ml per segment of 0.5% bupivacaine to bring the sensory level to T8. Group B patients received SA with spinal bupivacaine (0.5%) of 3 ml-15 mg + fentanyl .25 mic. Intraoperative hemodynamics, the duration to achieve a sensory level of T8, the time for two-segment regression of sensory block, and the complications that occurred were recorded.

RESULTS

The study included a total of 134 subjects with each group having 67 subjects admitted for lower limb surgery. The mean value (SD) of the time taken to attain sensory block in the SCSEA group was prolonged when compared to the SA group (7.15 ± 0.75 and 5.01 ± 0.88). The time for two-segment regression in the SCSEA group was 86.77 ± 3.60 and the SA group was 106.4 ± 8.01, which indicated that the SA group has a longer and better sensory block. Substantially, the study shows that the SCSEA group (P < 0.05) has better hemodynamics when compared to the SA group.

CONCLUSION

The SCSEA technique has better intraoperative hemodynamic stability with a longer analgesic effect when compared to SA. SA shows a sudden change in hemodynamics but reveals a greater sensory block.

Performance of the Hypotension Prediction Index With Noninvasive Arterial Pressure Waveforms in Awake Cesarean Delivery Patients Under Spinal Anesthesia

BACKGROUND

Arterial hypotension is common after spinal anesthesia (SA) for cesarean delivery (CD), and to date, there is no definitive method to predict it. The hypotension prediction index (HPI) is an algorithm that uses the arterial waveform to predict early phases of intraoperative hypotension. The aims of this study were to assess the diagnostic ability of HPI working with arterial waveforms detected by ClearSight system in predicting impending hypotension in awake patients, and the agreement of pressure values recorded by ClearSight with conventional noninvasive blood pressure (NIBP) monitoring in patients undergoing CD under SA.

METHODS

In this retrospective analysis of pregnant patients scheduled for elective CD under SA, continuous hemodynamic data measured with the ClearSight monitor until delivery were downloaded from an Edwards Lifesciences HemoSphere platform and analyzed. Receiver operating characteristic (ROC) curves were constructed to evaluate the performance of HPI algorithm working on the ClearSight pressure waveform in predicting hypotensive events, defined as mean arterial pressure (MAP) <65 mm Hg for >1 minute. The sensitivity, specificity, positive predictive value, and negative predictive value were computed at the optimal cutpoint, selected as the value that minimizes the difference between sensitivity and specificity. ClearSight MAP values were compared to NIBP MAP values by linear regression and Bland-Altman analysis corrected for repeated measurements.

RESULTS

Fifty patients undergoing CD were included in the analysis. Hypotension occurred in 23 patients (48%). Among patients experiencing hypotension, the HPI disclosed 71 alerts. The HPI predicted hypotensive events with a sensitivity of 83% (95% confidence interval [CI], 69-97) and specificity of 83% (95% CI, 70-95) at 3 minutes before the event (area under the curve [AUC] 0.913 [95% CI, 0.837-0.99]); with a sensitivity of 97% (95% CI, 92-100) and specificity of 97% (95% CI, 92-100) at 2 minutes before the event (AUC 0.995 [95% CI, 0.979-1.0]); and with a sensitivity of 100% (95% CI, 100-100) and specificity 100% (95% CI, 100-100) 1 minute before the event (AUC 1.0 [95% CI, 1.0-1.0]). A total of 2280 paired NIBP MAP and ClearSight MAP values were assessed. The mean of the differences between the ClearSight and NIBP assessed using Bland-Altman analysis (±standard deviation [SD]; 95% limits of agreement with respective 95% CI) was -0.97 mm Hg (±4.8; -10.5 [-10.8 to -10.1] to 8.5 [8.1-8.8]).

CONCLUSIONS

HPI provides an accurate real time and continuous prediction of impending intraoperative hypotension before its occurrence in awake patients under SA. We found acceptable agreement between ClearSight MAP and NIBP MAP.

Prediction of spinal anesthesia-induced hypotension during elective cesarean section: a systematic review of prospective observational studies

BACKGROUND

Spinal anesthesia is the standard for elective cesarean section but spinal anesthesia-induced hypotension remains an important problem. Accurate prediction of hypotension could enhance clinical decision-making, alter management, and facilitate early intervention. We performed a systematic review of predictors of spinal anesthesia-induced hypotension and their predictive value during cesarean section.

METHODS

PubMed, Embase, Cochrane Library, Google Scholar and Web of Science databases were searched for prospective observational studies assessing the diagnostic accuracy of predictors of spinal anesthesia-induced hypotension in elective cesarean section. The quality of studies was assessed and predictors were grouped in domains based on the type of predictor.

RESULTS

Thirty-eight studies (n=3086 patients) were included. In most studies, patients received 500-1000 mL crystalloid preload or 500-2000 mL crystalloid coload. Vasopressors for post-spinal hypotension were boluses of ephedrine 5-15 mg and/or phenylephrine 25-100 µg in most studies. The hypotension rate varied from 29% to 80% based on the definition. For analysis, >30 predictors were classified into seven domains: demographic characteristics, baseline hemodynamic variables, baseline sympathovagal balance, postural stress testing, peripheral perfusion indices, blood volume and fluid responsiveness indices, and genetic polymorphism.

CONCLUSIONS

Environmental and individual factors increased outcome variability, which restricted the value of the autonomic nervous system and peripheral perfusion indices for prediction of spinal anesthesia-induced hypotension. Supine stress tests may reflect parturients' cardiovascular tolerance during hemodynamic fluctuations and may optimize the predictive value of static state predictors. Future research for predicting spinal anesthesia-induced hypotension should focus on composite and dynamic parameters during the supine stress tests.

Large dose bupivacaine 0.5% versus small dose in elective cesarean section

Background and Aim:

The spinal anesthesia in a cesarean section is still presenting a challenge to the anesthetist in the form of either severe hypotension from large bupivacaine dose or insufficient satisfactory anesthesia level conditions as a result of small bupivacaine dose. In this study, we tried to solve this challenge by increasing the dose of bupivacaine to achieve a proper spinal level accompanied by prolonged sitting up to avoid hypotension.

Patients and Methods:

We included 53 patients in this study whom were randomly divided into two groups, namely Group B and Group C. In Group B (25 patients), each patient received 3 mL of bupivacaine and left 5 min sitting up, whereas in Group C (28 patients), each patient received 2.5 mL of bupivacaine and was asked to lie supine immediately. Both groups were tested for hypotension, ephedrine dose, and sensory block level.

Results:

The present study showed a statistically significant lower dose of ephedrine which was given in Group B (7.2 ± 15.684 mg in Group B versus 27.86 ± 12.04 mg in Group C with P < 0.05). The proper anesthesia level was achieved equally in both groups.

Conclusions:

Large dose 15 mg of bupivacaine with the prolonged sitting position will lead to fewer incidences of hypotension and proper anesthesia block.

A three minutes supine position test reveals higher risk of spinal anesthesia induced hypotension during cesarean delivery. An observational study

Background: Cesarean delivery is performed under spinal anesthesia, and vasodilation is the main cause for a drop in blood pressure. The compression of the aorta and inferior vena cava by the gravid uterus is of additional clinical importance. Hypotension may occur during cesarean delivery even if prophylactic infusion of phenylephrine is practiced. We have tested if a 3 minute supine observation, can identify a subset of women with decreasing systolic arterial pressure (SAP) under spinal anesthesia. Methods: We performed a prospective observational study at Oslo University Hospital on healthy pregnant women for planned cesarean delivery. Continuous measurements of calibrated invasive SAP and estimated cardiac output were recorded for 76 women in a 3 minutes measurement with the woman in the left lateral position, followed by supine position for 3 minutes. Using functional data clustering, principal component analysis and curve smoothing, to filter way noise and reduce the dimensionality of the signal, we clustered the women into separate SAP groups.   Results: We identified two significantly different groups of women during supine position; one characterized by initial drop in SAP, the other showed initial increase. After spinal anesthesia, the mean SAP curve of the women in the first group showed a drop in blood pressure, which was more rapid than for the other women. A minor difference in cardiac output was observed between the two groups of women with the mean cardiac output curve for the first group being higher. Conclusions: This work indicates that supine position affect clinically relevant cardiovascular measurements in pregnant women. A simple test may identify patients with increased risk of spinal anesthesia induced hypotension.

Can point-of-care ultrasound predict spinal hypotension during caesarean section? A prospective observational study

Spinal anaesthesia for elective caesarean section is associated with maternal hypotension, secondary to alteration of sympathetic tone and hypovolemia, in up to 70% of cases. Measurement of the subaortic variation in the velocity time integral (VTI) after passive leg raising allows prediction of fluid responsiveness. Our objective, in this prospective single-centre observational study, was to assess the ability of change in VTI after 45° passive leg raising to predict hypotension after spinal anaesthesia. Ultrasound measurements were performed just before elective caesarean section. Anaesthesia, intravenous coloading and prophylactic vasopressor treatment were standardised according to current guidelines. We studied 40 women. Hypotension occurred in 17 (45%) women. The area (95%CI) under the receiver operating characteristics (ROC) curve for the prediction of spinal hypotension was 0.8 (0.6-0.9; p = 0.0001). Seventeen women had a change in VTI with leg elevation ≤ 8%, which was predictive for not developing hypotension, and 11 had a change ≥ 21%, predictive for hypotension. The grey zone between 8% and 21%, with inconclusive values, included 12 women. We suggest that cardiac ultrasound provides characterisation of the risk of hypotension following spinal anaesthesia at elective caesarean section, and therefore may allow individualised strategies for prevention and management.

Effect of Lateral Tilt Angle on the Volume of the Abdominal Aorta and Inferior Vena Cava in Pregnant and Nonpregnant Women Determined by Magnetic Resonance Imaging

Background:

Left-lateral tilt position is used to reduce assumed aortocaval compression by the pregnant uterus.

Methods:

Magnetic resonance images of 10 singleton parturients at full term and 10 healthy nonpregnant women were obtained for measurement of the abdominal aorta and inferior vena cava volume between the L1–L2 disk and L3–L4 disk levels in both the supine and left-lateral tilt positions (15°, 30°, and 45°) maintained by insertion of a 1.5-m-long polyethylene foam placed under the right side of the parturient’s body.

Results:

Aortic volume did not differ significantly between parturients and nonpregnant women in the supine position (12.7 ± 2.0 vs.12.6 ± 2.1 ml, mean ± SD; mean difference, –0.1; 95% confidence interval [CI], −2.0 to 1.9; P = 0.95). Inferior vena cava volume in the supine position was significantly lower in parturients than in nonpregnant women (3.2 ± 3.4 vs.17.5 ± 7.8 ml; mean difference, 14.3; 95% CI, 8.3–20.2; P &lt; 0.001). Aortic volume in parturients did not differ among left-lateral tilt positions. Inferior vena cava volume in the parturients was not increased at 15° (3.0 ± 2.1 ml; mean difference, −0.2; 95% CI, −1.5 to 1.2; P &gt; 0.99), but was significantly increased at 30° (11.5 ± 8.6 ml; mean difference, 8.3; 95% CI, 2.3–14.2; P = 0.009) and 45° (10.9 ± 6.8 ml; mean difference, 7.7; 95% CI, 2.2–13.1; P = 0.015).

Conclusions:

In parturients, the aorta was not compressed, and a 15° left-lateral tilt position did not effectively reduce inferior vena cava compression.

Caesarean delivery vasopressor management

PURPOSE OF REVIEW

This review assesses the maternal and fetal effects of vasopressor administration during spinal anaesthesia for caesarean delivery, with emphasis on recent findings.

RECENT FINDINGS

Maternal heart rate is a good surrogate for cardiac output. The initial hypotensive effect of spinal anaesthesia is caused by a rapid decrease in systemic vascular resistance, which makes α-agonists the logical first-line therapy. Effective prophylactic phenylephrine administration can be associated with reduced maternal cardiac output, but this has not been associated with adverse maternal or fetal effects. Prophylactic phenylephrine infusion can cause hypertension if increasing arterial pressure does not trigger a timely reduction in the rate of administration. Phenylephrine has been used safely in mothers with cardiac disease and in pregnancies with suspected fetal compromise. Fetal genotype may increase resistance to ephedrine-induced acidosis. The combination of vagolytics and vasopressors has caused maternal hypertensive crises with serious adverse outcome.

SUMMARY

Phenylephrine is the current vasopressor of choice for the prevention of maternal hypotension and nausea. Phenylephrine regimens need to be developed that can reliably and safely be used with noninvasive blood pressure cycle times less frequent than every minute. Further vasopressor should be used with caution when vagolytic therapy is, quite rightly, used to treat bradycardia associated with hypotension.