Nausea, vomiting, and aspiration pneumonia in “non-fasting” patients undergoing non-emergent contrast-enhanced computed tomography scan and relation to food intake

INTRODUCTION

Fasting before contrast-enhanced computed tomography (CECT) has been traditionally considered necessary due to concerns about acute adverse reactions (AARs) (especially emetic complications) and aspiration pneumonitis.¹ In the era of first-generation ionic, high-osmolality contrast media (HOCM), the frequency of nausea and vomiting was 4.58% and 1.84%, respectively.¹ With the extensive use of non-ionic iodinated contrast media (ICM), HOCM has been gradually phased out from the market.² Non-ionic ICMs have been shown to reduce the frequency of AARs, including nausea and vomiting, to 0.013% and 0.059%, respectively.²

The driving factor of preparatory fasting orders prior to CECT was based on a logical assumption by practitioners and policymakers that vomiting is more likely to occur when the stomach is full.³ Fasting accelerates the emptying of gastric contents and prevents aspiration and subsequent aspiration pneumonia when patients receive contrast in a supine position.³

Patients are generally instructed to fast for 4-6 hours prior to CECT in most of the medical institutions throughout the world.⁴

The “mandatory preparation regimen” is arbitrary and unjustified, and the existing fasting strategies can reasonably be made less restrictive.⁵ However, most institutions appear hesitant to “deviate from the fasting dogma,” which can be attributed to their reliance on deep-rooted clinical experience patterns and a lack of evidence-based knowledge.²

Excessive fasting can produce a series of negative effects on patients, including general discomfort (e.g., hunger, thirst, dehydration) or hypoglycemia (a risk in diabetic patients), and may even increase the risk of adverse events.⁶ Excessive fasting can increase the patient’s stress responses into a catabolic state, disrupt the body’s internal environment and metabolic balance, and increase the risk of AAR after ICM injection.⁶ Fasting patients present with poor compliance and non-operation as they are more susceptible to irritability and anxiety during the waiting period or the examination process.^7,8 In addition, patients usually stop routine medications during the fasting period, which may aggravate the health risks for patients with diabetes, hypertension, and those who need continuous medication.

The latest American Committee of Radiology (ACR) 2021 guidelines and European Society of Urogenital Radiology (ESUR) guidelines (2018) V10.0 clearly state that fasting is not recommended before routine intravenous ICM administration.^9,10

As per our institutional policy, patients are instructed to report fasting for non-emergent CECT, but some patients fail to comply. This results in their scan being deferred, delayed, or rescheduled; and hampers the patient workflow in CT scan. This study was designed to conduct CECT in such patients who reported without fasting, and assess the incidence of AARs in them.

MATERIAL AND METHODS

Case proforma

Clinical details, diagnosis, vital parameters, and inclusion and exclusion criteria were recorded in the case proforma. Body parts imaged on CT, time of food ingestion prior to CECT, type of food, and quantity of food ingested were also recorded. Type of AAR, time of occurrence, management, and outcome were also recorded [Figure 1].

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Figure 1:

Flow diagram of methodology. CECT: Contrast-enhanced computed tomography, AAR: Acute adverse reactions, ESUR: European Society of Urogenital Radiology.

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RESULTS

DISCUSSION

This prospective study evaluated the effect of non-fasting on the occurrence of nausea, vomiting, aspiration pneumonia, and other AARs in patients undergoing non-emergent CECT, and correlations with the time, type (solid/liquid), and quantity of ingested food. The overall incidence of AAR was 4% in our study and consisted of nausea and vomiting in one non-fasting patient each following intravenous contrast injection. None of the patients developed aspiration pneumonia.

A retrospective study by Liu et al. (2022) in 127,200 participants concluded that there was no statistical difference in the overall prevalence of AARs (0.211% 0.254%, p=0.126) between the fasting and non-fasting patients.² Our incidence of AARs is higher, probably because of the smaller sample size. Wagner et al. (1997)reported that there was no significant difference in the incidence of AARs between patients who underwent 4 hours of fasting and those who did not.¹¹ In our study, no statistically significant difference was noted between the incidence of AARs amongst the patients who underwent the CECT between 0.5-2 hours of food intake.

In a randomized clinical trial by Neeman et al.¹² (2021)1011 non-fasting patients were given non-ionic contrast (iopromide 370 mgI/mL), and rates of nausea and vomiting in non-fasting patients (7.6% and 3%, respectively) were much higher than in our study (2% and 2%). This may be attributed to higher rates of contrast injection, for lower limb angiography and CECT abdomen in their study. Neither of these types of CT examinations was done in our study.¹² Neeman et al. (2021) concluded that withholding fasting orders was not associated with an increased risk of aspiration pneumonia or increased incidence of emetic complications.¹² Similarly, Liu et al. (2022) in a retrospective study of 1,27,200 participants, found no statistical difference in the overall prevalence of emetic complications (0.030% vs. 0.046%, p=0.158) between the fasting and non-fasting patients.²

Oowaki et al. (2021) reported that preparatory fasting increased the incidence of nausea and vomiting with high-osmolality ICM (6.7%) but not with low-osmolality ICM (1.4%).¹³ In our study, we found 4% incidence of nausea and vomiting with low osmolality ICM. Li et al. (2018) also found less incidence (.08%) of nausea and vomiting in non-fasting patients using low-osmolar non-ionic contrast media.¹⁴

In our study, emetic complications occurred immediately following intravenous contrast injection on the CT table; however, symptoms were self-limiting and subsided within 30 minutes of observation. In a study by Li et al. (2018), nausea and vomiting occurred during the injection of ICM and within 15 minutes after intravenous injection.¹⁴ Similarly, in a prospective study by Kim et al. (2018), amongst 34 out of 1175 patients who complained of nausea, 19 patients experienced nausea during ICM administration, and 15 patients developed nausea after 5 minutes of contrast administration.^15,16

One of the patients who developed nausea after contrast injection was a 19-year-old female who had tachycardia (PR=110/min), prior to CECT, which persisted even after reassurance. She was a known case of epilepsy, on medication (Levetiracetam 500 mg BD) for 1 year. She underwent CECT chest after 20 minutes of intake of 90 g of solid fatty food and complained of nausea immediately following the contrast injection [Figure 2]. After verbal reassurance, the CECT was completed successfully and revealed a diagnosis of pulmonary TB. No antiemetic drugs had to be administered, and no further AARs occurred. After CECT, her nausea and tachycardia resolved within 10 minutes, and she revealed that she had unknowingly missed her daily morning dose of anticonvulsant and was therefore anxious that she may have a convulsion.

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Figure 2:

A 19-year-old female presented for CECT chest after consumption of solid fatty food 20 minutes before the scan. (a) Axial NCCT scan through the lower thoracic cavity shows a well-distended stomach (black arrow) with hyperdense solid food contents. She was administered 70.0 mL iohexol-350 mgI/mL intravenously at 3.0 mL/sec and developed nausea on the CT table following contrast injection. (b) Axial CT scan reveals multiple centrilobular nodules with tree-in-bud appearance (black arrow) in the right upper lobe, suggestive of active pulmonary Koch’s. CECT: Contrast-enhanced computed tomography, NCCT: Non-contrast computed tomography scan.

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Another patient who had vomiting following contrast injection was a 50-year-old male who presented for CECT thorax 55 minutes after ingestion of 250 g of solid fatty food [Figure 3]. He had tachycardia (PR=115/min) prior to CECT. There was no aspiration, and no anti-emetics were administered. His CECT chest was completed without any further adverse reaction, and the diagnosis of mediastinal lymph nodal tuberculosis was confirmed on CECT. His tachycardia resolved spontaneously. The other patients complained of nausea and vomiting after CECT, which resolved spontaneously after 30 minutes of observation.

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Figure 3:

A 50-year-old male presented for CT chest after intake of 250 g of solid fatty food 55 minutes before CT. (a) Axial NCCT shows food contents in the stomach (white arrow). He was administered 70 mL iohexol-350 mgI/mL intravenously at 3.0 mL/sec. His baseline pulse rate was 116/min. His tachycardia persisted during the observation period of 60 minutes. (b) CECT coronal MPR revealed multiple conglomerated necrotic lymph nodes (white arrow) suggestive of mediastinal nodal tuberculosis. CECT: Contrast-enhanced computed tomography, NCCT: Non-contrast computed tomography scan.

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In a study by Neeman et al.¹² (2021), of 1011 non-fasting patients, 18.3% patients ingested solid/liquid within 1 hour before CT scan, while the remaining 81.7% patients had taken solid/liquid during 1 to 4 hours before CT scan. Nearly two-thirds had only liquid within 1 hour prior to the CT scan, while 54.1% ingested only liquids within 1-4 hours. The rates of emetic complications were comparable between these two groups (within 1 hour and between 1-4 hours). Nausea following solid food intake was 8.5% and 7.6%; following liquid intake, 7.1% and 7.6% respectively in the 2 groups (within 1 hour and between 1 to 4 hours) [p = 0.9].¹² In our study, 4% patients developed emetic complications within one hour (20 and 55 minutes, respectively) after intake of solid fatty food. Only 12% patients had taken a liquid diet (50-500 ml) between 0.5 to 2 hours before undergoing CECT [Table 2], however, none of them developed any AARs. In our study, no statistically significant correlation was found between the type of food or the time of intake of food with AARs. (p – 0.61, 0.388)

No statistically significant correlation was found between the quantity of solid food ingested and AAR (p = 0.255) using ANOVA. To the best of our knowledge, no literature is available exploring the relationship between the quantity of food consumption and the occurrence of AAR.

Liu et al. (2021) found dermatological, neurological, and cardiovascular adverse reactions in 80.00%, 8.60%, and 4.6% patients, respectively, and bronchospasm in 8.10%.⁵ None of the patients showed urticaria, bronchospasm, neurological, or cardiovascular adverse reactions in the present study.

The main limitation of our study was that it was a single-center study conducted in one institution, limiting external validity and possibly introducing a selection bias. Another limitation was the small sample size in this prospective design, because very few patients reported for CECT abdomen in a non-fasting state. So there is a need for multicenter prospective studies with larger sample sizes in the future.

CONCLUSION

After taking a meticulous history to exclude allergic diseases and recording a detailed and thorough medical history in non-fasting patients undergoing CECT, no moderate AAR and severe AARs or aspiration pneumonia were observed irrespective of the time of ingestion of food, type, and quantity of food. Thus, non-emergent contrast-enhanced CT scans can be successfully conducted in non-fasting patients, thereby ensuring a smooth workflow in a busy radiology department and the convenience of the sick patients.