Figure 10.1

Location of the pericardium meridian point 6 acupoint.

According to Traditional Chinese Medicine (TCM) theory, surgery interrupts the balanced state of the human body by disturbing the movement of both qi (energy flow) and blood, leading to stomach qi going upward to cause nausea and vomiting[6]. By regulating the function of the stomach to reduce the adverse flow of qi, PC6 acupoint stimulation may prevent nausea and vomiting[6]. However, from a Western evidence-based medicine perspective, the mechanism by which PC6 stimulation helps manage PONV is unclear.

Prevention

In the recent update of a Cochrane systematic review[7] on the effectiveness of PC6 acupoint stimulation for the prevention of PONV, 10 types of PC6 acupoint stimulation were examined in 59 trials published between 1986 and 2015 involving 7,667 participants. The invasive types of PC6 acupoint stimulation included the following techniques that penetrated the skin: needle acupuncture (five trials), acupuncture needle infiltration of PC6 acupoint with dextrose (four trials) or droperidol (one trial), semipermanent needles (one trial) and electrical stimulation of needles (six trials). The noninvasive types of PC6 acupoint stimulation that did not penetrate the skin included the following techniques: transcutaneous electrical nerve or acupoint stimulation (five trials), laser stimulation (two trials), acustimulation device (six trials), acupressure wristbands (25 trials), capsicum plaster (two trials) and conventional peripheral nerve stimulation (three trials). PC6 stimulation was compared with six different antiemetic drugs: metoclopramide (five trials), cyclizine (one trial), prochlorperazine (two trials), droperidol (five trials), ondansetron (nine trials) and dexamethasone plus ondansetron (one trial).

Of the 59 trials, only two were considered as at low risk of bias, 32 at moderate risk of bias and 25 at high risk of bias. Thus, the results as shown in Table 10.1 should be interpreted with a degree of caution. There were wide variations in the type of surgery patients underwent, the PC6 acupoint therapy technique (type, timing and duration), comparison (sham or antiemetic) and the follow-up time for assessing PONV (from postanesthesia care unit (PACU) to 72 h). However, the risks of POV were similar between subgroups.

Table 10.1 Results of meta-analyses of PC6 acupoint stimulation trials for preventing PONV

Outcome	Studies	Patients	RR (95% CI)	Quality of evidence
Acupoint PC6 stimulation versus sham
Nausea All groups Invasive Noninvasive	40 7 33	4,742 896 3,846	0.68 (0.60–0.77) 0.56 (0.39–0.80) 0.71 (0.62–0.81)	Low^a
Vomiting All groups Children Adults Mixed age groups Invasive Noninvasive	45 6 37 2 7^b 37^b	5,147 542 4,465 410 896 4,151	0.60 (0.51–0.71) 0.67 (0.46–0.97) 0.61 (0.51–0.72) 0.24 (0.07–0.79) 0.51 (0.34–0.76) 0.60 (0.50–0.73)	Low^a
Need for rescue antiemetic	39	4,622	0.64 (0.55–0.73)	Low^a
Acupoint PC6 stimulation versus antiemetic
Nausea All groups Invasive Noninvasive	14 5 9	1,332 559 773	0.91 (0.75–1.10) 0.69 (0.41–1.14) 0.95 (0.78–1.16)	Moderate^c
Vomiting All groups Invasive Noninvasive	19 8 12	1,708 734 974	0.93 (0.74–1.17) 0.99 (0.70–1.41) 0.90 (0.67–1.21)	Moderate^c
Need for rescue antiemetic	9	895	0.87 (0.65–1.16)	Moderate^c
Combined PC6 stimulation and antiemetic versus antiemetic
Nausea	8	642	0.79 (0.55–1.13)	Very low^d
Vomiting	9	687	0.56 (0.35–0.91)	Very low^d
Need for rescue antiemetic	5	419	0.61 (0.44–0.86)	Low^e

CI, confidence interval; PC6, pericardium meridian point 6 acupoint; RR, relative risk.

^a Evidence graded low due to a large proportion of underlying trials with moderate-to-high risk of bias and moderate degree of heterogeneity.

^b Shenkman et al.[8] not included in subgroup analysis as the intervention involved the use of both acupuncture and acupressure wristband.

^c Evidence graded moderate due to a large proportion of underlying trials with moderate-to-high risk of bias.

^d Evidence graded very low due to a large proportion of underlying trials with moderate-to-high risk of bias, imprecision and moderate degree of heterogeneity.

^e Evidence graded low due to trials with imprecision and moderate-to-high risk of bias.

Most trials compared PC6 acupoint stimulation versus sham and showed that PC6 acupoint stimulation was effective for preventing PONV and reduced the need for rescue antiemetics (Table 10.1). Although the overall evidence was low due to underlying high risk of bias in a small proportion of trials and a moderate level of heterogeneity, we would expect 54 (95% confidence interval (CI), 48–62) and 48 (95% CI, 41–57) fewer nausea and vomiting episodes per 100 high-risk patients, respectively, when the underlying control risk is set at 80 per 100. In the trials directly comparing PC6 acupoint stimulation before and after induction of anesthesia against sham[9,10], the risk reduction in PONV was similar in magnitude regardless of the timing of PC6 acupoint stimulation.

In contrast, there was a moderate level of evidence to support PC6 acupoint stimulation being comparable to an antiemetic to prevent PONV (Table 10.1). There is also emerging evidence, albeit low quality, to suggest that the combined effect of P6 acupoint stimulation and antiemetic was more effective than an antiemetic alone in reducing the risk of vomiting and the need for a rescue antiemetic. The risk reduction associated with the combined effect of the PC6 acupoint stimulation and an antiemetic was consistent with the multimodal concept of using a combination of antiemetic therapy to provide a “synergistic” effect. Overall, the side effects associated with PC6 acupoint stimulation were minor and self-limiting.

Treatment

Few trials have been conducted to examine the use of PC6 acupoint stimulation for the management of established PONV. One trial showed that, for established postoperative nausea associated with the use of morphine patient-controlled analgesia, a greater reduction was observed in the severity of nausea on a 100-mm visual analog scale with bilateral PC6 acupuncture for 2 min compared with sham acupuncture (mean difference 29; 95% CI, 16–43)[11]. Rescue metoclopramide was more likely to be required in the sham acupressure group (100%) than in the PC6 acupressure group (47%; P = 0.001). Another trial showed that, in addition to intravenous (IV) metoclopramide 10 mg or droperidol 0.625 mg prophylaxis after induction of anesthesia, the combination of a wristband acustimulation device and ondansetron for the treatment of established emetic symptoms was more effective than the acustimulation device group, but was similar in the effectiveness to the ondansetron group (complete response rate without need for rescue therapy 73%, 40% and 57%, respectively)[12]. The results of these two trials suggest that PC6 acupoint stimulation may be a promising nonpharmacologic technique for the treatment of established PONV in those patients who may have had contraindications to taking an antiemetic.

Whilst many different techniques of PC6 acupoint stimulation have been examined in approximately 7,800 patients, there is currently a lack of widespread uptake of the technique. This may be due to a lack of evidence in the optimal timing, duration and method of PC6 acupoint stimulation[13]. In addition, invasive PC6 acupoint stimulation requires trained professionals to administer the technique that often takes up to 30 min; in contrast, the pharmacologic effect of an antiemetic is immediate. New research methods, such as network meta-analysis, may offer fresh insights into the comparative effectiveness of PC6 acupoint stimulation techniques against sham or antiemetics to answer the question of which types of PC6 acupoint stimulation technique are most effective to prevent PONV .

Ginger

Prevention

Ginger (Zingiber officinale) is a common herb used in TCM. The pharmacologically active component of ginger, 6-gingerol, has antiserotonin and anticholinergic actions in the gastrointestinal tract[14]. As with all herbs, it is difficult to standardize the active extracts, which may partly explain the mixed results from clinical trials. A pharmacokinetic analysis showed that the half-lives of ginger metabolites were 1–3 h in human plasma and did not accumulate after multiple daily dosing of 2 g over 1 month[15]. It appears that ginger supplements do not have clinically important anticoagulant effects[16].

This section reviews the RCTs of ginger powder in capsules on the prevention of PONV and updates the published trials included in a 2006 systematic review[17]. There were 11 oral ginger trials[14,18–27] published between 1990 and 2014 involving 1,228 participants. In all trials, the oral ginger, placebo and antiemetics (metoclopramide, dexamethasone and droperidol) were given 1 h before induction of anesthesia. The dose of ginger powder ranged from 0.3 g[21] to 2 g[27], with one trial[19] comparing 0.5 g and 1 g against a placebo. Trials were mainly conducted in women undergoing gynecologic surgery[14,18–21,24,25,27]. Follow-up time for PONV ranged from 2 to 24 h. Of the 11 trials, only two were considered as at low risk of bias[19,21], seven at moderate risk of bias and two at high risk of bias[18,23].

The results of meta-analyses of ginger comparisons are shown in Table 10.2. In comparing ginger with placebo, there was no subgroup difference on nausea by dose (P = 0.17). However, there was a subgroup difference on vomiting by dose (P < 0.01), with a significant risk reduction in trials with doses 1 g or above compared to placebo (P = 0.001). A sensitivity analysis based on low-to-moderate risk of bias trials with ginger doses 1 g or above showed that ginger was more effective than placebo in reducing the risk of vomiting (relative risk (RR) 0.66; 95% CI, 0.49–0.88). The effects of ginger or combined ginger with an antiemetic were similar to the antiemetic control group (Table 10.2). The reported side effects (abdominal discomfort and heartburn) associated with ginger were infrequent[18,19,25].

Table 10.2 Results of meta-analyses of oral ginger capsules for preventing PONV

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