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.