The impact of using NGT on PONV after cardiac surgery
The incidence of PONV after cardiac surgery can be as high as 42-71% [8,9,10,11,12,13]. Many pharmacological and non-pharmacological therapies have been applied in the treatment of PONV. However, patients that have undergone cardiac surgery are more susceptible to developing hypotension, oversedation, and cardiac arrhythmias with the use of traditional antiemetics [14,15]. Additionally, severe PONV can result in significant complications such as electrolyte disturbance, dehydration, aspiration, and myocardial ischemia due to increased myocardial oxygen consumption [16,17,18]. Similarly, gastric distention caused by increased swallowing post-operatively increases intragastric pressure which may make patients more susceptible to PONV [19]. This is further exacerbated if the gas mixture in the stomach contains elements of volatile anesthetics introduced into the stomach during manual ventilation [20]. Currently, there is conflicting evidence regarding the utility of using routine NGT in to relieve gastric distention and to reduce PONV.
In patients undergoing other general surgical procedures, it was found that gastric decompression, which NGT use is intended for, did not reduce PONV [21,22]. Furthermore, another large comparative study including patients who underwent a wide variety of non-cardiac surgical procedures found that there was no significant difference in PONV incidence in groups with or without NGT [23]. Due to the several conflicting reported results, the current consensus guidelines do not recommend the routine use of NGT to prevent PONV [24].
In a recent randomized controlled trial of 202 postoperative cardiac patients, it was found that the incidence of postoperative vomiting after cardiac surgery was higher in the control group (24%) than in the NGT group (10%, p=0.007). However, NGT use was not found to significantly impact nausea. The significant reduction in vomiting was observed within 8 hours post cardiac surgery, and there was no difference with respect to the use of antiemetics between the 2 groups. In this study, the NGT was inserted after induction of anesthesia and maintained on gravity suction until removal with extubation [3].
In their randomized cohort study of 104 patients, Burlacu et al. (2005) found that continuous gastric decompression using a NGT during coronary revascularization surgery until tracheal extubation did not reduce the incidence and severity of nausea or the incidence of vomiting or retching in these patients (Table 3) [16]. The severity of these parameters was measured for the first 24 hours postoperatively. However, Burlacu et al. (2005) reported that since the incidence of PONV after cardiac surgery was less than what is reported in the literature, this study was effectively underpowered to detect a difference in PONV despite the prospective power calculation that was done. Additionally, another study with 114 patients undergoing cardiac surgery with cardiopulmonary bypass were randomized to receive NGT after the induction of anesthesia or not, and PONV was recorded for the first 24 hours postoperatively (Table 3) [25]. It was reported that the use of NGT did not impact the incidence of PONV or requirements for antiemetics after cardiac surgery.