Most pregnant patients request and receive regional anesthesia for cesarean section. Unfortunately, the cesarean section experience under spinal anesthesia is often marred by maternal nausea and vomiting. Lussos et al.  reported that 80% of patients at their institution who received spinal anesthesia for cesarean section complained of intraoperative nausea and vomiting, unless they were pretreated with a pharmacologic antiemetic. The use of metoclopramide to reduce intraoperative nausea and vomiting during cesarean section under regional anesthesia has been evaluated, and several authors have reported that this drug is an effective antiemetic that does not depress neonatal neurobehavioral function [2,3]. It is not, however, a drug without side effects, including dystonic reactions, restlessness, and tachycardia.
Acupressure, a noninvasive variation of acupuncture involving constant pressure on the wrist, has been reported as a possible nonpharmacologic method to prevent nausea and vomiting. Both acupuncture and acupressure are based on the belief that an individual's well-being depends on the balance of energy in the body as well as the overall energy level. It is hypothesized that energy flows within the body along paths referred to as meridians and that these techniques restore the balance of energy flow by manipulating these meridians . In acupressure, pressure is exerted on the Neiguan (P6) acupuncture points, located on the anterior surface of the wrists, three fingers breadth above the distal skin crease of the wrist joint between the tendons of the palmaris longus and flexor carpi radialis muscles . There have been reports suggesting that acupressure can decrease the nausea due to morning sickness , general anesthesia , cytotoxic therapy , and postoperative morphine administration . However, acupressure previously has not been described to decrease the intraoperative nausea and vomiting associated with cesarean section. This study was designed to compare acupressure and intravenous metoclopramide prophylaxis for nausea and vomiting during elective cesarean section under spinal anesthesia.
The study was approved by our institutional review board and written, informed consent was obtained from each patient. The patient sample consisted of 75 healthy patients undergoing elective cesarean section during spinal anesthesia. Patients were prospectively randomized via an envelope system into one of three groups, 25 patients per group. Group I patients received acupressure bands and 2 mL of intravenous saline. The acupressure bands used in this study contained a small button that exerted pressure on the P6 point. Group II patients (metoclopramide group) received placebo wrist bands (a wrist band without a pressure button) and 10 mg of metoclopramide by slow intravenous administration. The patients in Group III (control group) received placebo wrist bands and 2 mL of intravenous saline.
For patients in Group I, a closed elastic acupressure band (Sea Band[TM]; Sea Band UK Ltd, Leicestershire, UK) was slipped over the fingers and hands like a bracelet. Occasionally a problem arose when attempting to slip the acupressure band past the intravenous catheter. In such cases, an adjustable Velcro acupressure band (Acuband[TM]; Lifestyle Enterprises, Little Silver, NJ) allowed the band to be placed regardless of intravenous site or size of patient hand. Acupressure bands were placed snugly around the wrist so that the patient felt gentle pressure without discomfort. Pulse oximetry was placed on the index finger of the same hand and confirmed that blood flow to the digits was unimpeded. Bands were considered too loose and were tightened if a wedge of paper fit between the acupressure band and skin. Despite the fact that the intravenous catheter was often placed distal to the band, at no time did the pressure of the bands interfere with IV fluid administration. At least 15 min before the induction of anesthesia, wrist bands were placed bilaterally by an anesthesiologist not directly involved in the patient's care. The acupressure bands were loosely covered with gauze and tape so they could not be distinguished from the placebo bands. All intravenous injections were administered in the operating room, just prior to induction of the spinal anesthetic. Patients were excluded from the study if they had a history of nausea and vomiting associated with previous surgery or anesthesia, nausea or vomiting within the 24 h prior to the cesarean section, a history of diabetes mellitus, or morbid obesity. Patients, anesthesiologists, obstetricians, and nurses were all blinded to treatment group.
All patients received 30 mL of orally administered 0.3 M sodium citrate solution preoperatively and were hydrated with 15-20 mL/kg of intravenous lactated Ringer's solution immediately prior to induction of anesthesia. Oxygen at a rate of 5 L/min was administered via disposable face mask to each patient. After placement of standard monitors, all patients were placed in the sitting position for initiation of the spinal anesthetic. Subarachnoid puncture was performed with a 24-gauge Sprotte needle through a midline approach at the L2-3 or L3-4 interspace. Each patient received a spinal injection of 1.5 mL of spinal bupivacaine 0.75% plus dextrose 8.25% with 10 micro g fentanyl. Immediately after the subarachnoid injection, patients were placed supine with left uterine displacement to approximately 25 degrees using a right hip wedge. After delivery, oxytocin 20 U/L was given by slow intravenous infusion to all patients.
Noninvasive blood pressure measurements were taken every minute from completion of the spinal injection until delivery of the neonate and then every 3 min until admission to the recovery room. Any decrease in systolic blood pressure >20% from baseline or to less than 100 mm Hg was treated with intravenous ephedrine in 5- to 10-mg increments. To avoid the confounding influences of other drugs, ephedrine was the only drug administered to these patients prior to delivery. Patients were questioned every 5 min concerning their general well being. Nausea and sedation were assessed using a visual analog scale (0-10). Patients who reported a score greater than 2 for nausea or sedation on this scale were considered positive for these conditions. Any patient who volunteered that she was anxious was considered positive for anxiety. Univariate statistical tests included one-way analysis of variance ANOVA (continuous data) and chi squared (categorical data). These tests were evaluated at the 0.05 level of significance. Multivariate logistic regression evaluated the independent contributions of mode of treatment and systolic blood pressure to risk of nausea. All statistical analyses were performed with version 5.02 of the SPSS[R] for Windows[TM] software (Chicago, IL, 1993).
Mean age was 30.8 +/- 6.3 yr, mean weight was 76.2 +/- 12.8 kg for all patients. Of the 75 women (73.3%), 55 had experienced at least one previous birth. The groups did not differ statistically with respect to these characteristics. All patients received 1500-2000 mL lactated Ringer's solution, and all achieved a T2-4 block. No patient requested supplemental medication to treat intraoperative pain. None of the patients delivered a child with an Apgar score of <7 at 1 or 5 min. Overall, 52 of the 75 patients (69.3%) manifested hypotension. The incidence of hypotension was similar among the three groups-64.0%, 68.0%, and 76.0% in the acupressure, metoclopramide, and placebo groups, respectively.
As shown in Table 1, patients who received either acupressure or metoclopramide during spinal anesthesia for cesarean section had much less nausea than patients in the placebo group (24% vs 76%, P < 0.001; 16% vs 76%, P < 0.001, respectively). There was no difference in the occurrence of nausea between patients who received acupressure and patients who received metoclopramide (24% vs 16%, P > 0.05).
Although the groups did not differ overall in the proportion of patients experiencing vomiting, fewer patients who received metoclopramide vomited when compared to the placebo group (one-tailed Fisher's exact P value = 0.049). Acupressure was not as effective as metoclopramide in decreasing vomiting (acupressure versus placebo, one-tailed Fisher's exact P = 0.23).
As shown in Table 2, when the analysis was restricted to hypotensive patients (systolic blood pressure <100 mm Hg), the proportion of patients with nausea was significantly less among patients who received acupressure than among patients who received placebo (37.5% vs 78.9%, P < 0.05), and less among patients who received metoclopramide than among patients who received placebo (23.5% vs 78.9%, P < 0.01). Again, there was no difference in the occurrence of nausea between patients who received acupressure and patients who received metoclopramide (37.5% vs 23.5%, P > 0.05).
Although anxiety is a known side effect of metoclopramide, in this study very few patients stated that they were anxious. Four patients in the metoclopramide group (16%) experienced anxiety compared with one patient (4%) in each of the other two groups. Anxiety was not significantly increased in the metoclopramide group compared with the other two groups (P > 0.05).
A logistic regression analysis was performed to examine the independent contributions of systolic blood pressure and mode of treatment to the risk of nausea. The logistic regression confirmed the univariate analyses. As expected, there was an inverse relationship between systolic blood pressure and nausea. After controlling for systolic blood pressure, there remained a marked protective effect for acupressure and metoclopramide with regard to nausea. Compared with patients given placebo, acupressure decreased the risk of nausea by 93%; metoclopramide by more than 95%.
The unmedicated pregnant patient is prone to nausea and vomiting during spinal anesthesia for cesarean section . The etiology of these emetic symptoms is multifactorial and varies among patients. The progesterone-induced smooth muscle relaxation, decreased gastrointestinal motility, and the reduced lower esophageal sphincter tone of pregnancy may precipitate these emetic symptoms. Kang et al.  reported that the incidence of intraoperative emetic symptoms during spinal anesthesia for cesarean delivery correlated with the development of hypotension. This hypotension may, in turn, cause brainstem hypoxia and thus trigger the vomiting center to induce emesis. The rate of intraoperative nausea in unpremedicated patients for cesarean section under spinal anesthesia was >75%. Ratra et al.  have suggested that supplemental oxygen may decrease the incidence of nausea despite hypotension. Therefore, as is our routine practice, all patients enrolled in this study received supplemental oxygen delivered by face mask.
Previous studies have demonstrated that metoclopramide decreases the incidence of nausea and vomiting in the patient undergoing cesarean delivery. This drug, however, is not without possible side effects, including anxiety, agitation, sedation and dystonic reactions . In a recent sheep study, Eisenach and Dewan  reported that metoclopramide may exaggerate tachycardia after stress, encountered frequently both during and after cesarean section. In addition, supraventricular tachycardia has been reported after administration of 10 mg of intravenous metoclopramide . The present study was prompted by a desire to find a "complication-free" method to reduce nausea and vomiting during cesarean section in the awake patient under spinal anesthesia.
An attempt was made to control factors known to be responsible for intraoperative nausea and vomiting. For instance, to prevent motion-related emetic symptoms from occurring during transport to the operating room, all patients, regardless of group, were wheeled to the operating room on a stretcher with their gaze in the direction of travel. Although subarachnoid narcotics are systemically absorbed and may cause emesis, all patients in this study received the same dose of subarachnoid fentanyl. Therefore, the effects of fentanyl would have been uniform across groups.
The patient population was a homogeneous group of healthy women scheduled for elective cesarean sections under spinal anesthesia. All 75 patients requested regional anesthesia and all were accompanied by a support person in the operating room. No intravenous narcotics, sedatives, or anxiolytic drugs were administered intraoperatively to any patient in this study and thus these drugs were not considered in the analysis. Although the exteriorization of the uterus during cesarean section may precipitate nausea and vomiting, all patients underwent cesarean section with this technique.
Patients were randomized to a treatment group regardless of their requests to receive the "real band." One possible bias, however, is that patients may have been able to distinguish the presence or absence of pressure on the wrist. For example, one patient stated, "I must be in the placebo group because I thought that these things were worn on the inside of the arm and I don't feel any pressure there." This patient, however, did not complain of intraoperative nausea or vomiting. There were no similar reports from other patients.
Acupressure causes low-frequency electrical stimulation of the skin sensory receptors that may activate A-beta and A-delta fibers . These fibers all synapse within the dorsal horn and may in turn cause a release of endorphin from the hypothalamus. In addition, serotonergic and norepinephrinergic fibers may be activated. Although there is no clear explanation for the antiemetic effects of acupuncture and acupressure, a possible explanation lies in this change in serotonin transmission.
In summary, both acupressure and metoclopramide, administered prophylactically, reduced the incidence of nausea in patients undergoing elective cesarean section under spinal anesthesia. A 60% reduction was observed in the incidence of intraoperative nausea with metoclopramide and a 52% reduction with acupressure. Although acupressure may not have been as effective at preventing intraoperative vomiting associated with spinal anesthesia-induced hypotension as metoclopramide, acupressure was found, in this study, to be without side effect or complication. For this reason, acupressure is an important tool for the anesthesiologist when administering a spinal anesthetic for elective cesarean section.
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