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ORIGINAL RESEARCH |
From the Departments of 1Anesthesia and Pain Management and 2Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Toronto, Onatario, Canada.
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ABSTRACT |
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METHODS: This study was a randomized, single-blinded trial in 80 women undergoing elective cesarean delivery under spinal anesthesia. Patients were randomly assigned to exteriorized or in situ uterine repair. Obstetricians were asked to perform assisted delivery of the placenta. Spinal anesthesia and oxytocin management were standardized. Phenylephrine was used to maintain systolic blood pressure within 10% of the baseline. The primary outcome was intraoperative, postdelivery nausea or vomiting.
RESULTS: Postdelivery nausea or vomiting (18% compared with 38%; P=.04) and tachycardia (3% compared with 18%; P=.03) were significantly reduced in the in situ group compared with the exteriorized group. The duration of uterine repair was significantly shorter in the exteriorized group (median 10 minutes [first and third quartiles 9, 13], compared with 11 minutes [9, 15]) (P=.04). The duration of surgery (36 minutes [30, 41] compared with 37 minutes [30, 45]) and estimated blood loss (mean±standard deviation 625±489 mL compared with 653±416 mL) were similar between the in situ and the exteriorized groups. There was no correlation between duration of uterine repair and estimated blood loss.
CONCLUSION: Exteriorization of the uterus for repair is associated with an increased incidence of nausea and vomiting and tachycardia during cesarean delivery under spinal anesthesia. Uterine repair should be done in situ where possible.
CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, www.clinicaltrials.gov, NCT00452972
LEVEL OF EVIDENCE: I
Although some obstetricians remain convinced of the surgical merits of the technique of uterine exteriorization and continue to use it, the patient’s comfort remains a disputed matter. Uterine exteriorization has been associated with adverse outcomes, including nausea and vomiting, pain, hemodynamic changes, and air embolism.
This study was undertaken to compare the two techniques (exteriorized and in situ) of uterine repair with respect to patient comfort, hemodynamic changes, surgical time, and blood loss in patients undergoing elective cesarean delivery under a strictly standardized spinal anesthetic. We hypothesized that in situ uterine repair would be more comfortable for the patients.
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MATERIALS AND METHODS |
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All patients received 30 mL of sodium citrate 0.3 mol/L, orally, 30 minutes before surgery. The baseline readings of noninvasive blood pressure, heart rate, and SpO2 were taken three times, 1 minute apart, in the preoperative holding area, where an intravenous line was established and lactated Ringer’s solution started at a rate to keep the vein open.
On arrival in the operating room, patients were randomly assigned by means of a computer-generated randomization scheme into one of the two study groups: exteriorized repair or in situ repair. The group allocation was blinded by the use of sealed envelopes until that moment. Staff obstetricians who had clinical equipoise with both methods of uterine repair performed the surgery. Nineteen of 21 obstetricians agreed to randomly assign their patients and to participate in the study.
Immediately before the administration of regional anesthesia, patients were preloaded with 10 mL/kg of the lactated Ringer’s solution. Spinal anesthesia was performed in the sitting position, using a 27-gauge Whitacre needle, with 12 mg of 0.75% hyperbaric bupivacaine, 100 mcg of preservative-free morphine, and 10 mcg of preservative-free fentanyl. After the spinal injection, patients were immediately placed in the supine position with left uterine displacement. Supplemental oxygen via nasal prongs was administered at a rate of 4 L/min until delivery of the infant. A sensory block to T6 by pinprick was considered satisfactory for surgery. After the delivery of the infant, all patients received a bolus of 0.5 International Units of oxytocin intravenously, followed by an infusion of 20 International Units diluted in 1,000 mL of lactated Ringer’s at a rate of 120 mL/h (40 milli-Units/min). Incremental bolus doses of 0.5 International Units were given at the surgeons’ request. The obstetricians were asked to allow assisted spontaneous delivery of the placenta and appropriate contraction of the uterus before exteriorization, in case patients were randomly assigned for such. One gram of cefazolin diluted in 10 mL of normal saline was given as the first choice antibiotic. In cases of allergy to penicillin, 600 mg of clindamycin was given. Blood pressure was assessed every minute throughout the cesarean delivery. Any drop in blood pressure was treated with an intravenous bolus dose of 100 mcg of phenylephrine, repeated as necessary, to maintain systolic blood pressure within 10% of the baseline values. Ephedrine was used as a second choice if the patient developed persistent bradycardia (heart rate 50 beats per minute or less). Hypotension was defined as a decrease in systolic blood pressure greater than 20% of the baseline value, despite the use of prophylactic phenylephrine. In the event of discomfort requiring analgesic supplementation, the patients were given up to 100 mcg of fentanyl intravenously.
The patients were questioned intraoperatively at specific intervals and records kept of any nausea, vomiting, or pain. Pain was quantified with a verbal numerical rating scale of 0 to 10 (0 being no pain and 10 being worst pain imaginable). The duration of uterine repair and the total duration of surgery (skin incision to skin suture) were noted. Immediately before and after surgery, the level of anesthetic block was checked bilaterally by pinprick and recorded.
Naproxen suppositories were administered rectally at the end of the surgery as an adjunct to postoperative analgesia. Patients were observed for 2 hours in the postanesthesia care unit. The oxytocin infusion was continued at the rate of 40 milli-Units/min until discharge from the postanesthesia care unit. Hemoglobin and hematocrit were recorded before surgery and within 48 hours after surgery. The estimated blood loss was calculated according to the following formula:
Estimated blood loss=EBV (pre-op Hct– post-op Hct)/pre-op Hct
Where EBV is estimated blood volume (mL)=(body weight in kilogramsx85); pre-op, preoperative; post-op, postoperative; Hct, hematocrit.
The primary outcome in our study was intraoperative, postdelivery nausea or vomiting. Based on a previous study conducted at Mount Sinai Hospital, the incidence of nausea during cesarean deliveries under spinal anesthesia using exteriorized repair is 35%. We estimated that 36 patients per group would be needed to show a 75% reduction in nausea and vomiting with in situ repair as compared with exteriorized repair, assuming a statistical power of 80% at an alpha level of 0.05%. We planned to enroll 80 patients. The analysis was done by intention to treat.
Data were summarized by using descriptive statistics. Continuous outcome variables were analyzed with independent t test or the Mann-Whitney nonparametric test, as appropriate. Appropriateness of the Mann-Whitney test was determined by nonnormal distribution of the residues. Bonferroni correction was used to adjust for multiple testing. Chi-square and Fisher exact tests were used for testing association between categorical variables. Spearman rank correlation was used to investigate the correlation between the duration of uterine repair or surgery and the estimated blood loss. All the analyses were done in SAS 8.2 (SAS Institute Inc, Cary, NC).
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RESULTS |
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Patient demographics were similar in both groups, except for patients in the exteriorized group being taller (Table 1). There was a statistically significant increase in postdelivery nausea or vomiting (odds ratio [OR] 2.95, 95% confidence interval [CI] 1.04–8.34) and tachycardia (OR 8.53, 95% CI 0.99–394.12) in the exteriorized group compared with the in situ group (Table 2). The incidence of pain and hypotension was higher in the exteriorized group, but these differences were not significant between groups (Table 2).
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Patients in the exteriorized group exhibited complications (hypotension, tachycardia, pain, and nausea and vomiting) during uterine repair, immediately after exteriorization, and then again at the time of the required repositioning of the uterus into the abdominal cavity (Tables 3 and 4). Patients in the in situ group, however, exhibited such complications typically during uterine repair.
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DISCUSSION |
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Our study exclusively investigated intraoperative complications related to uterine repair, particularly patient comfort, and we shall limit our discussion to that scope. It is important to highlight that the existing studies on the subject lack standardization of the anesthetic management, which plays a key role in the development of intraoperative complications. The standardization of the anesthetic procedure in our patients is one of the highlights of this study. On the other hand, it has the weakness of being single-blinded and of not being powered for variables other than nausea and vomiting, which was our primary outcome. According to our results, the incidence of intraoperative, postdelivery nausea or vomiting was significantly higher when uterine repair was performed exteriorized, compared with in situ (37.5% and 15%, respectively).
The overall incidence of intraoperative nausea and vomiting during regional anesthesia for cesarean delivery is highly variable, up to 80%, depending on the anesthetic technique used (spinal, epidural, or combined spinal-epidural) and on the preventive and therapeutic measures taken. Different factors have been implicated in the etiology of intraoperative nausea and vomiting. Hypotension and visceral pain are among the most important ones and are to a great extent preventable.9
We attempted to meticulously control intraoperative blood pressure by means of preload, left uterine displacement, and liberal use of vasopressors, particularly phenylephrine, which has become the vasopressor of choice in obstetrics. We aggressively treated any decrease in systolic blood pressure to minimize hypotension as a cause of nausea and vomiting. Recent studies have consistently shown the superiority of the pure 
-agonists, phenylephrine and metaraminol, over ephedrine for the control of maternal hypotension, and for improved fetal acid-base balance.10 Phenylephrine was the first-line vasopressor in our patients. In addition, studies have shown that there is distinct association of nausea and vomiting with the degree of maternal hypotension, and strict control of blood pressure can dramatically reduce intraoperative emetic symptoms. Ngan Kee et al11 observed that, when phenylephrine was titrated with the aim of maintaining maternal blood pressure at 100% of baseline, the incidence of nausea and vomiting was only 4%, compared with 16% when the blood pressure was maintained at 90% and 40% when it was 80% of baseline, during spinal anesthesia for cesarean delivery. We believe that our efforts to maintain blood pressure at 90–100% of the baseline values throughout the procedure minimized the contribution of hypotension to the development of nausea and vomiting. This is probably one of the most important differences between the current study and previous publications. In addition to the prophylactic use of vasopressors, oxytocin was judiciously used to reduce oxytocin-induced hypotension. Although not recommended for use as a bolus injection, our obstetricians usually request an intravenous bolus of oxytocin. We have used a very small bolus dose, which is close to what we have recently demonstrated to be the minimum effective dose of oxytocin to produce an adequate response in 90% of women (ED90) in elective cesarean deliveries.12
Exteriorization of the uterus, intraabdominal manipulation or exploration, and peritoneal traction during uterine repair and abdominal closure can cause pain or discomfort. Visceral pain, carried by the unmyelinated C-fibers, is typically poorly localized, dull and deep, and is a potent stimulus for intraoperative nausea and vomiting. In the absence of epidural narcotics, a level of anesthesia up to and including T5 is required to prevent pain during cesarean delivery.13 The addition of lipophilic neuraxial opioids to the local anesthetic solution can effectively reduce visceral pain by depressing the C-fiber–mediated response.14 Even in the presence of a seemingly dense conduction block, vigorously manipulated tissues may be the cause of postdelivery emetic symptoms. During our study, we strictly followed the strategy to prevent nausea and vomiting during cesarean delivery by ensuring an adequate spinal anesthetic level (T4-T5) and optimal use of neuraxial opioid. One may argue that the dose of local anesthetic used in our study was inadequate to produce a dense enough block to blunt the nausea and vomiting response during exteriorized uterine repair. Ginosar et al15 have recently conducted a dose-response study under similar conditions and determined that the ED95 of hyperbaric bupivacaine for a successful cesarean delivery was 11.2 mg when used in association with 10 mcg of fentanyl. The dose of bupivacaine (12 mg) that we used in our study was therefore in keeping with the most recent information available in the literature, although we recognize that this information is based on a small sample of patients and may need to be further adjusted in more widespread use. Additional studies with a higher dose of local anesthetic are warranted to investigate whether the quality of block can be further improved to reduce nausea and vomiting during exteriorization and repositioning of the uterus during cesarean delivery.
It is interesting to observe that the group that underwent exteriorized uterine repair exhibited a significantly higher incidence of tachycardia and a nonsignificant increase in the incidence of hypotension and pain. These events tended to coincide with the repositioning of the uterus into the abdominal cavity. The repositioning of the uterus can be, at times, a very intense stimulus, which could explain the pain and tachycardia. However, we also hypothesize that this procedure can determine a hemodynamic effect, with transient compression of the inferior vena cava and a decrease in preload, due to the space-occupying effect of the now repositioned uterus. This effect seems transient but important enough to induce hemodynamic changes and also cause nausea and vomiting.
Exteriorization of the uterus for repair is thought to be associated with easier and faster uterine repair and less blood loss.1,2 The literature, however, is controversial on those matters. In our study, the duration of uterine repair was marginally shorter when the uterus was exteriorized for repair, and it is unlikely that it played any role in decreasing blood loss. In addition, no correlation could be found between duration of uterine repair and blood loss. Magann et al16 and Baksu et al17 found that blood loss at cesarean delivery is greater with manual removal than with spontaneous detachment of the placenta from the uterine wall. In both studies, however, the site of the uterine repair, in situ or exteriorized, did not seem to affect blood loss. The reason for increased bleeding with manual removal is that the placenta is detached before uteroplacental blood flow decreases, thus increasing the hemorrhage from dilated sinuses. In the current study, the obstetricians performed assisted delivery of the placenta in all patients, and oxytocin infusion was started immediately after the delivery of the anterior shoulder, producing early contraction of the uterus and facilitating placental detachment. Under such circumstances, we could find no difference in estimated blood loss between the two groups. These results, however, should be interpreted with caution for two reasons: 1) the estimation of blood volume as adjusted to weight in kilograms in pregnant patients has limitations, and 2) the study was not powered to study differences in blood loss.
In summary, exteriorization of the uterus for repair increases the incidence of nausea or vomiting during cesarean delivery under spinal anesthesia. It also induces more hemodynamic changes, particularly tachycardia. Uterine repair at cesarean delivery should be done in situ, unless there is a surgical reason for exteriorization.
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Footnotes |
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Presented at the 37th Annual Meeting of the Society for Obstetric Anesthesia and Perinatology, Palm Desert, California, May 4–7, 2005.
Corresponding author: Jose C. A. Carvalho, MD, PhD, Department of Anesthesia and Pain Management, Mount Sinai Hospital, 600 University Avenue, Room 781, Toronto, ON M5G 1X5, Canada; e-mail: jose.carvalho{at}uhn.on.ca.
Financial Disclosure The authors have no potential conflicts of interest to disclose.
doi:10.1097/01.AOG.0000277712.67230.22
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REFERENCES |
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2. Wahab MA, Karantzis P, Eccersley PS, Russell IF, Thompson JW, Lindow SW. A randomized, controlled study of uterine exteriorization and repair at caesarean section. Br J Obstet Gynaecol 1999;106:913–6.[Medline]
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  I. C. Coutinho, M. M. Ramos de Amorim, L. Katz, and A. A. Bandeira de Ferraz Uterine Exteriorization Compared With In Situ Repair at Cesarean Delivery: A Randomized Controlled Trial Obstet. Gynecol., March 1, 2008; 111(3): 639 - 647. [Abstract] [Full Text] [PDF]
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