Combined Spinal-epidural Anesthesia-induced Hypotension: A Risk Comparison Between Patients With Severe Preeclampsia And Healthy Women Undergoing Cesarean Section

Study Background and PurposeSevere preeclampsia in critical condition is one of the leading cause of maternal mortality. Cesarean section is the rescue of patients with severe preeclampsia effective means. Combined spinal-epidural anesthesia(CSEA)is a new kind of anesthetic techniques in recent years. CSEA had epidural block and subarachnoid block advantages, including rapidity, sufficient block, reliability of the subarachnoid block with the flexibility of continuous epidural block to extend duration of analgesia. Based on the above-mentioned advantages, CSEA should be suitable for patients with severe preeclampsia requiring cesarean section.Hypotension was a maternal common complication of CSEA. Pronounced and lasting hypotension cause utero-plcental insufficiency, fetal hypoxia, acidosis, neonatal asphyxia. For severely preeclamptic parturients on the one hand, because of hypovolemia, anesthesia induced-vasodilation and because of the need to limit IV fluids to avoid iatrogenic pulmonary edema, they were susceptible to hypotension. On the other hand, because preeclampsia is characterized by an increased production of numerous circulating factors with a potent pressor effect, by an increased sensitivity of blood vessels to pressor drugs and because of endothelial damage, these two phenomena contribute to lower accident of hypotension observed in preeclampsia. They can resistant to the sympathetic blockade to a certain extent. Therefore, they were not prone to hypotension.In overseas, it has been reported the incidence and severity of spinal anesthesia (SA)-associated hypotension in severely preeclamptic versus healthy parturients undergoing cesarean delivery, this prospective case control study showed that the incidence of hypotension, is less in patients with severe preeclampsia undergoing spinal anesthesia for cesarean delivery, as compared with healthy parturients, the magnitude of the decrease in mean BP is smaller in severely preeclamptic patients.In China, the author compared changes in blood pressure between pregnant women with pregnancy hypertension and non-pregnant women with pregnancy hypertension in the epidural anesthesia during cesarean section, they think pregnant women with hypertension was more likely to suffer from hypotension. At present, it is scanty to compare CSEA-inducing hypotension pregnant women in severely preeclamptic to healthy parturients undergoing cesarean delivery.In a prospective study, we compared the incidence and severity of CSEA-associated hypotension in severely preeclamptic versus healthy parturients undergoing cesarean delivery. We discuss CSEA for patients with severe preeclampsia, the safety and validity, and provide the basis for clinical application.Materials and MethodsStudy objects1. Enrollment criteria: adult patients aged 21-39 years old with ASA physical statusⅠ-Ⅲclass were scheduled for elective cesarean section under combined spinal-epidural anesthesia. Informed consent anesthesia were obtained from the patient on the day before surgery. 50 severely preeclamptic patients were devided to observer group; 50 healthy parturients were devided to control group in the same period.2. According to the seventh edition Obstetrics book standards, Surgeon based on preoperative diagnosis and the naming and classification of China's current classification standards, severe preeclampsia was defined systolic blood pressure≥160 mm Hg, diastolic blood pressure (DBP)≥110 mm Hg, or both; proteinuria≥5.0g/24h, or random urine protein characterization≥(+++);serum creatinine level﹥106μmol/L; PLT﹤100*109/L;serum ALT or AST increased; persistent headache or other neurological or visual impairments; Persistent epigastric discomfort.3. Exclusion criteria 1) Patients with chronic hypertension 2) Patients with diabetes 3) Patients with multiple gestation 4) Patients with coagulopathy PLT﹤75*109/L 5) Patients with body mass index greater than 35 kg/m2 6) Patients with refusal, any contraindication to CSEA 7) Patients with active labor 8) Patients with local or generalized sepsis 9) Patients with severe cardiopulmonary dysfunction 10) Patients with less than 28 weeks'gestation 11) Patients who have allergic reaction to local anesthetics 12)Patients with abruptio placentae, placenta praeviaStudy protocol1. Patients in each group were preoperative fasting 8 hours. All patients did not use premedication. Severely preeclamptic parturients were given nitroglycerin or nitroprusside to lower blood pressure according to obstetrician requirements. Intravenous magnesium sulfate was given as seizure prophylaxis in some patients with neuromuscular hyperexcitability according to obstetrician requirements. Make preparation for maternal and neonatal resuscitation.2. Entering the operating room, venous lines were set up. Before administering combined spinal-epidural anesthesia, all patients were given an IV infusion of 500 ml of colloid solution (6% hydroxyethyl starch in balanced salt solution) over 20 min before the anesthetic. Routine monitoring of noninvasive blood pressure (NIBP), pulse oxygen saturation (SpO2), heart rate (HR), continuous electrocardiogram (ECG). Oxygen, 4-5L/min, was administered through a nasal cannula routinely.3. The patient was then placed in the left decubitus, After skin infiltration with lidocaine, the epidural space was identified with an 17G WeiSS needle using loss-of-resistance to 2 mL of air at the L2-3 interspace. Through the epidural needle, a long 25G Whitacre pencil-point spinal needle was introduced. On puncturing the dural, the spinal needle was securely docked. After verifying free flow of cerebrospinal fluid (CSF), 0.5% isobaric bupivacaine (7.5mg at the discretion of the anesthesiologist, Injection time more than 20 seconds ) was administered with the spinal needle orifice facing right. Before removing the 17GWeiSS needle, a 20-gauge epidural catheter was inserted 3cm into the epidural space facing cephalad. Patients were immediately positioned supine with a 10°–15°left lateral tilt. If unintentional dural puncture with the epidural needle occurred, the epidural catheter was threaded into the subarachnoid space and intrathecal drugs were administered via the catheter.4. To prevent supine syndrome, the patient was then returned to the supine position with left uterine displacement or the bed tilted 10°–15°left. The maximum level of sensory block was checked at 10 min after the spinal injection using pinprick skin. If the upper sensory level did not achieve T8 , 1.5% lidocaine 3ml as test dose were injected into epidural space via the epidural catheter,when no blood and cerebrospinal fluid have been pumpbacked from epidural catheter. Excluding total spinal anesthesia, 2%lidocaine 2-15ml intermittently were given. Electrocardiogram, heart rate and oxygen saturation were monitored preblock and continuously throughout the study.Observed indexes and time point1. The values of pulse oxygen saturation (SpO2),heart rate (HR), mean arterial pressure (MAP), systolic blood pressure(SBP), diastolic blood pressure(DBP) and electrocardiogram(ECG)were recorded when entering the operating room and before induction of anesthesia .Baseline BP and HR were obtained before induction of anesthesia.2. The values of SBP, DBP, MAP, HR, SpO2 were recorded at 2-min intervals from the spinal injection to the 10th min and then at 5-min intervals until the end of the surgery respectively. Lowest BP and HR after CSEA and intraoperative highest BP and HR were recorded.3. The other study variables included demographic data; gestational age; the maximum level of sensory block at 10 min after the spinal injection; neonatal weight; and 1- and 5-min Apgar scores; the volume of fluids administered; the incidence of ephedrine administration and the dosage of ephedrine given; the dosage of lidocaine, incidence of hypotension (systolic BP﹤100 mm Hg or decrease﹥20% from baseline BP), nausea, vomiting, and shivering (defined as involuntary contraction or twitching of themuscles).Statistical methodsAll data were analyzed by statistical software SPSS14.0. Measurement data were expressed by mean±standard deviation ( x±s). Count data indicated by the percentage. Mean values of most quantitative study variables were compared by using the unpaired Student's t-test. Count data was analyzed byⅹ2 test, A P value of <0.05 considered that there was a significant difference. The largest and smallest values of BP and HR were compared with corresponding baseline values in each study group by using the paired Student's t-test. Odds ratios were calculated to estimate the relative risk of hypotension between the groups.Results1. The general and demographic data One hundred patients were enrolled in this study, ASA physical status of all the patients wereⅠ-Ⅲclass. There were 50 severe preeclampsia and 50 healthy parturients. The patients'age was between 21-39 years, the average age was 29.9±3.5 years in group healthy parturients and 30.2±3.9 years in group severe preeclampsia. The average weight was 66.2±8.3 kg in group healthy parturients and 67.5±8.7 kg in group severe preeclampsia. There were 43 nullipara in group healthy parturients and 32 nullipara in group severe preeclampsia. Patients with severe preeclampsia had a younger gestational age than healthy parturients(P﹤0.05).2. The volume of IV fluid administered and the dosage of 2% lidocaine were smaller in the severely preeclamptic group than healthy parturients(P﹤0.05).The height of the CSEA blockade was similar in both groups(P﹥0.05). The incidence of ephedrine administration and the dosage of ephedrine given was smaller in the severely preeclamptic group than healthy parturients(P﹤0.05).3. Neonatal weight was smaller in the severely preeclamptic group than healthy parturient(sP﹤0.05). 1-min Apgar scores of their neonates and 5-min Apgar scores of their neonates was similar in both groups(P﹥0.05). 1-min Apgar scores≤7 and 5-min Apgar scores≤7 was similar in both groups(P﹥0.05).4. Mean baseline values of SBP, DBP, and mean BP were larger in the severely preeclamptic group(P﹤0.05). The magnitude of the decrease in SBP, DBP and mean BP was significantly larger in patients with severe preeclampsia than healthy parturients (P﹤0.05). The incidence in hypotension were more in the severely preeclamptic group(P﹤0.05). The increase in HR was of larger magnitude in patients with severe preeclampsia(P﹤0.05). Odds ratio calculation suggested that the risk of hypotension was almost six times more in patients with severe preeclampsia (odds ratio, 3.768; 95% confidence interval, 1.647-8.620; P = 0.001).Conclusions1. This prospective case control study shows that the incidence and severity of hypotension are more in severely preeclamptic patients, as compared with healthy parturients, undergoing CSEA for cesarean delivery.2. Severe preeclampsia, undergoing CSEA for cesarean delivery, should note that adjusting the dosage of anesthetic, strengthening intraoperative monitoring, and intraoperative fluid administration, were important measures to prevent and treat the severe complications on parturient and neonate.