Artigos sobre anestesia obstétrica

Iniciamos divulgação de mensagens sobre anestesia obstétrica por meio do site com um clipping produzido mensalmente pela Profa. Joanne Douglas, de Vancouver – Canadá. Ela disseca alguns artigos relevantes da subespecialidade e sugere leitura de outros, sempre com comentários pertinentes e inteligentes. Garanto ser leitura rápida, atual e muito proveitosa. Enjoy!

News Item:

Case reports have always been an important part of our specialty, especially when they deal with rare conditions where management may be controversial or the effects of anesthetic agents uncertain.  In the March issue of Anesthesia and Analgesia the journal announced that case reports would no longer be published in that journal but that they were establishing a new journal titled, Anesthesia & Analgesia Case Reports.  This should be a welcome development for obstetric anesthesiologists as most main-stream journals are either not publishing case reports (e.g. Anesthesiology), publishing few case reports or insisting that all be in the Correspondence section (Anaesthesia).  It will be interesting to see what impact this new journal has.  Initially it won’t be indexed and as case reports are often included in the impact factor (a measure as to the importance of a journal – in some minds) it may not be looked on favorably by universities for purposes of promotion. 

Traditional Epidural or Combined Spinal Epidural

Arguments for and against these two techniques have occupied the minds of obstetric anesthesiologists for over 10 years.  Those for CSE argue that one can provide rapid analgesia/anesthesia through the spinal component while having the epidural component for extending the duration of the block.  Those for a traditional epidural argue that if it works then one is assured that it will continue to work well when one needs to “top” it up.  As well, it appears to have less impact on the fetal heart rate than does the CSE. 

At the 2010 annual SOAP meeting David Gambling and colleagues presented the results of their study comparing the two techniques in a private practice setting; looking at pain scores during labor (1st and 2nd stages) and at delivery.  At that meeting they were awarded the “best paper” award for their presentation.  The manuscript from that study is finally published (Anesth Analg 2013;116:636-43).

This study assessed over 800 patients (822) for eligibility for the study and excluded 20 of those.  These 802 subjects were then randomized to receive either traditional EA (400) or CSE (402) after they requested analgesia.  Blocks of subjects were stratified to account for parity and induction vs spontaneous labor.  A verbal rating scale (0-10) was documented immediately before neuraxial block, after administration of full epidural dose (epi group) or intrathecal dose (CSE group) and then after the contraction pain was 1 or 0 out of 10.  When fully dilated patients rated pain score during 1st stage of labor  (overall pain score during the period after the neuraxial block).  This was also done after delivery for the 2nd stage and then for what the pain delivering the baby.  Overall satisfaction (4 point Likert scale) was also assessed. 

All had neuraxial anesthesia inserted in the sitting position.  Women in the epidural group had 10 mL 0.125% bupivacaine with fentanyl 2 ?g/mL in two doses through the needle followed by an additional 5 mL through the catheter to initiate analgesia.  The CSE group received the same solution (2.5 mL) intrathecally.  Both groups then received PCEA with the same solution (infusion 6 mL/h, bolus 5 mL, lockout 5 min, max hourly dose 26 mL).  The authors indicate the methods used to determine sample size.

The study took place from March 26, 2007 to November 10, 2009.  Data were analyzed from 398 subjects and 402 subjects in the epidural and CSE groups respectively.  The two groups were demographically similar.  There were no differences in mode of delivery (SVD 73%), use of episiotomy, duration of second stage or time from initiation of analgesia to end of first stage of labor.    Baseline VRPS were similar between groups but the time to complete analgesia was faster in the CSE group and the VRPS for analgesia during the first stage of labor was lower in the CSE group.  The number of physician top-up doses was higher in the epidural group, need for epidural catheter replacement was similar while fetal bradycardia requiring intervention within 30 mins was 8.5% in CSE group vs 4.5%; but all resolved with conservative measures.

As the authors point out there were several important points with respect to this study.  One, it was done in a private practice setting; two the epidural group initially received analgesia through a needle; pain relief during the 1st and 2nd stages of labor were separately assessed as was; fourth, pain relief at delivery.  They feel that CSE provides more rapid and effective first stage analgesia with fewer top-ups than does the traditional epidural.

An accompanying editorial (Booth JL, Pan PH.  Anesth Analg 2013;116:515-6) points out that this research confirms that both techniques are effective means of providing analgesia for labor but that there still are some unanswered questions.  One concern that I have is our sterile technique when we access the intrathecal space in labor rooms.  While the epidural space is somewhat forgiving of breaches in technique the subarachnoid space is likely less so.  This issue is not addressed by this study or by the editorial.

Identifying the Midline in Obese Parturients with Ultrasound

Sahota et al (Anesth Analg 2013;116:829-35) compared the paramedian sagittal oblique to the transverse median plane as to which was most effective in identifying the midline in obese parturients. 

This observational cohort study recruited obese women (BMI>30 kg/m2 requesting epidural labor analgesia or having a cesarean delivery under CSE.  All had their lumbar spine imaged in the sitting position prior to neuraxial block.  The paramedian sagittal oblique and the transverse median planes were both scanned. 

The neuraxial block was done by an experienced anesthesiologist, who was given information about the interspace and insertion point.  As well, they were told an estimated depth to epidural space.  The needle was to be inserted in the midline, perpendicular to the skin or with minimal angle, if required.  After identifying the epidural space the Tuohy needle was marked at the skin so that the distance to the epidural space using the needle could be documented.  This depth was then compared with the estimated depth found using both ultrasound approaches.  Several other variables were collected including time to complete the procedure, need to redirect the needle, patient’s comfort during the procedure, and any complications.

 Sixty women (20 in each BMI category (30-34.9; 35-39.9; >40 kg/m2) were recruited.  The range of BMI was 30.4 to 66.2 kg/m2.  The ultrasound estimated epidural depth in the paramedian sagittal oblique plane was 6.5 cm, transverse median plane 6.5 cm and the actual needle was 6.6 cm.  The imaging quality was better in the paramedian sagittal oblique plane (good 87.6%) than the transverse median plan (68.3%).  The authors suggest that the two views can be used interchangeably but that the paramedian sagittal oblique plane may be better if visibility is poor in the transverse median plane.  The authors suggest that further studies involving more patients are required.

Intraoperative Nausea & Vomiting

Most intraoperative nausea and vomiting  (during cesarean delivery under spinal anesthesia) occurs prior to delivery and is related to hypotension secondary to sympathetic block.  With prompt treatment of hypotension or prophylaxis with phenylephrine the incidence is significantly lower.  Many will administer antiemetics to treat the nausea and vomiting, especially when it occurs after delivery of the baby or when hypotension does not appear to be the cause.

In a study by Habib et al (Obstet Gynecol 2013;121:615-23) 300 patients having cesarean delivery under spinal anesthesia were randomized into three groups.  Each group received two study solutions; one after spinal anesthesia and the second after cord clamping.  The placebo group received   placebo at both time periods; the metoclopramide group received metoclopramide 10 mg and then and the combination group received metoclopramide 10 mg and ondansetron 4 mg.  Sodium citrate antacid prophylaxis was administered to all subjects and the spinal anesthetic was standardized.  A phenylephrine infusion was started after the intrathecal injection and titrated according to an algorithm.  The primary endpoint was the incidence of nausea and vomiting defined as any nausea, vomiting or retching and there were a number of secondary endpoints.  A sample size of 100 subjects/group was estimated to provide 80% power to detect an absolute reduction in the incidence of nausea and vomiting to 20% and 15% in the two treatment arms (baseline incidence 40%).

306 patients were enrolled; 300 completed the study.  A consort diagram indicates the flow of participants and reasons for failure to complete the study.  Demographically the groups were similar (including incidence of hypotension related nausea and vomiting), with the exception that uterine exteriorization differed significantly (higher in the placebo and combination group (76%, 59%, 68% in the placebo, metoclopramide, combination groups).  Of interest, there was a higher incidence of uterine exteriorization at the North Carolina site (93%) vs the Nova Scotia site (39%). 

Intraoperative nausea & vomiting were significantly lower in both treatment groups compared to placebo but not between the two treatment groups.  This was accompanied by a lower need for rescue in the two treatment groups.  In those with intraoperative nausea and vomiting, nausea occurred before delivery 32%, after delivery 43% and both before and after in 25%.  Multivariable modelling found that intraoperative nausea and vomiting were significantly lower in the two treatment groups but exteriorization became nonsignificant in the presence of site (the two hospitals where the study was conducted).

The investigators concluded that metoclopramide and a combination of metoclopramide and ondansetron (remember when they were given) together with a prophylactic phenylephrine infusion decreased the incidence of intraoperative nausea and vomiting in women having cesarean delivery under spinal anesthesia.  They note that the incidence of intraoperative nausea and vomiting is still high and that more studies are needed to decrease this.

In the discussion the authors point out that there was a higher rate of intraoperative nausea and vomiting at the North Carolina site which was the site where uterine exteriorization was more likely to occur.  As they suggest this indicates that surgical factors probably play a significant role in intraoperative nausea and vomiting.  One issue that is not discussed is the effect of repeatedly asking subjects to indicate whether they had nausea (verbal nausea scores 0-10) every 5 minutes for the first 10 minutes and then every 10 minutes.  As any nausea score greater than 0 was considered nausea some may have interpreted any sensation as nausea.  Even though they had a strict definition of nausea, subjects might have misinterpreted any sensation.  Although a possible issue this only would have impacted their overall nausea and vomiting rates as randomization would have evened this out among the groups.  As any investigator knows this can be a real challenge in a study.  

Some Other Articles of Interest

  1. Roos-Hesselink JW et al.  Outcome of pregnancy in patients with structural or ischaemic heart disease:  results of a registry of the European Society of Cardiology.  Eur Heart J 2013;34:657-65.  Although there is nothing really new in this report it does confirm that good management and care leads to safe outcomes in the majority of women with structural heart disease.  Cardiomyopathy still has a poor outcome.
  2. Orbach H et al.  Hypertension and antihypertensive drugs in pregnancy and perinatal outcomes.  Am J Obstet Gynecol 2013;208:301.e1-6.  Again, nothing new but it confirms that chronic hypertension with or without treatment is a risk to the developing fetus.  This impacts us in a higher incidence of preterm delivery.
  3. George JW et al.  A randomized controlled trial comparing a multimodal intervention and standard obstetrics care for low back and pelvic pain in pregnancy.  Am J Obtet Gynecol 2013;208:295.e1-7.  Guess what?  Multimodal approach is better than standard obstetric care.  169 women studied prospectively by a multidisciplinary group where the lead author is from the College of Chiropractic.  There is an accompanying editorial on pregnancy-related lumbopelvic pain (Am J Obstet Gynecol 2013;208: 242).
  4. Carvalho B et al.  Evaluation of experimental pain tests to predict labour pain and epidural analgesic consumption.  Br J Anaesth 2013;110:600-6.  A major problem for investigators is trying to predict who will develop pain and who will not.  This study of 50 healthy pregnant women sought to answer that question.
  5. Cho CE, Normal M.  Cesarean section and development of the immune system in the offspring.  Am J Obstet Gynecol 2013;208;249-54.  This review looks at the relationship between mode of delivery and the immune system in the offspring.  Although short-term effects are seen and there is an apparent greater risk of asthma, allergies type I diabetes and celiac disease; there is no evidence re other long-term effects.  The authors suggest that more discussion is necessary on this topic with parturients who may desire a cesarean delivery.
  6. Mashour GA, et al.  Assessment of intraoperative awareness with explicit recall:  a comparison of two methods.  Anesth Analg 2013;116:889-91.  These authors compared the modified Brice interview (day 28-30) vs quality assurance techniques (day 1, did you have any problems with the anesthesia for your surgery).  They found the modified Brice interview was better than the open-ended question.  We use the modified Brice interview at BCW but usually use it on day 1 or 2.  Studies seem to indicate that some cases are not detected on early interview but only on follow-up interview (e.g. 1-4 wks.)  Perhaps, any GA cesarean delivery should have the Brice interview a second time.
  7. Ngamprasertwong P et al.  Effects of maternal anesthesia on intraoperative fetal outcomes in a sheep model.  Anesthesiology 2013;118:796-808.  Tran KM et al.  Anesthesia for fetal surgery.  Miles to go before we sleep.  (editorial)  Anesthesiology 2013;118:772-4.  This article and editorial seem to indicate that high-dose volatile anesthetics may not be the technique of choice for fetal surgery.  Obviously more study is needed.
  8. Singh-Radcliffe N.  Best practices for handover communication.  ASA Newsletter March 2013;77:20-21  Solid, common sense recommendations for handover – not only in OR but also in OB.

Joanne Douglas, MD
Vancouver, BC