Design and participants
In this prospective, single-center, randomized, controlled trial, cardiac surgery patients were screened at the Fujian University Affiliated Union Hospital from October 2021 to February 2022. The inclusion criteria were as follows: patients undergoing elective cardiac surgery; aged ≥ 18 years; no dysphagia during preoperative screening; capability to communicate and understand instructions; and no pneumonia before surgery. The following patients were excluded: history of neurological diseases (dementia, cerebral infarction, etc.); open injuries in the oral cavity before surgery (such as mandible injury), and history of cancer.
In this study, the method of continuous sampling was adopted. The researcher screened the patients before surgery, invited the patients who met the inclusion criteria to participate, and informed them of the purpose, method, and significance of this study. Once the patients agreed to participate, they immediately signed the informed consent form.
All voluntary participants could withdraw from the study at any time. The study design followed the CONSORT guidelines and was approved by the Ethics Committee of the Union Hospital affiliated with Fujian Medical University (2021KY105).
Randomization and allocation concealment
The patients were divided into EOH and COH groups using the block randomization method. In order to ensure the random distribution of subjects, a nurse, who did not participate in any other work related to the study, generated random numbers using IBM windows SPSS statistics version 23.0. The 84 subjects were divided into 14 block groups; the 6 subjects in each block group were numbered, and then randomly divided into either the EOH group, with numbers of 1–3, or the COH group with numbers of 4–6. The nurse put them into sequentially coded, sealed, and opaque envelopes. Once informed consent was sought and provided, the envelopes were opened in sequence, and the subjects were randomly assigned to one of the two groups in a 1:1 ratio. The researchers and subjects could not predict the distribution sequence. All data of patients were input and analyzed by a nurse with a master's degree. Because the patients signed informed consent forms and the researchers were two trained nurses, the EOH and COH groupings were obvious and could not be blinded. However, the two nurses responsible for data collection and the nurse in charge of data input and analysis were blinded.
Intervention
Both groups received oral care (brushing and gargling) immediately post-extubation. First, the thirst intensity of patients in the EOH group was evaluated using a numerical rating scale (NRS) [13], a straight 10-cm line, equally divided into ten parts. The NRS increases successively from 0 on the left, which represents no thirst, to 10 on the right, which represents intense thirst. Patients were requested to answer the following questions: “If 0 represents no thirst and 10 represents intense thirst, what do you consider as the most severe thirst, how would you rate your current thirst?” Second, patients were assessed for safety using the Safety Protocol for Thirst Management (SPTM) [14], which was authorized by Professor Fonseca and included three evaluation indicators: (1) level of awareness: asking the patient’s name; (2) airway protection: placing hands on the chest or abdomen to make the patient cough and swallow, and (3) nausea and vomiting: asking the patient about whether they felt nauseous. If one of the indicators failed, patients did not receive thirst management. Finally, patients who passed the SPTM at 1 h post-extubation were asked to perform a water-drinking test. In the test, the patient was in a 45° semi-decubitus position and allowed to drink 30 mL of warm water. The following observations indicated dysphagia: patients could swallow once but with choking; patients could swallow twice or more but with choking or frequent choking; or patients could not swallow. Patients with dysphagia had to retain the nil per OS (NPO) status. Without signs of dysphagia, the reported risk of aspiration is minimal when the gastric volume does not exceed 50 mL [15]. Therefore, 50 mL of warm boiled water was administered hourly over a period of 4 h, vaseline was then applied to the lips every hour after the intervention. If the patient experienced gastrointestinal adverse events, including nausea and vomiting, at any time during the intervention, the patient’s status was changed to NPO. Patients evaluated by SPTM could receive or reject the intervention at any time.
The patients in the COH group retained the NPO status for 4 h post-extubation. During that time, the researchers applied cotton swabs with water to the patients' lips every hour, followed by vaseline. Then, the patient was placed in a 45° semi-recumbent position for a 30-mL water-swallow test. If dysphagia, nausea, or vomiting occurred post-extubation, the patient’s status was changed to NPO, and the responsible nurse had to contact the attending physician for further instructions. Without adverse events, the patient was instructed to drink the water slowly. The SPTM assessment was required before all interventions.
Before leaving the ICU, the patients used the 5-point Likert scale [16] to score satisfaction with the thirst management intervention: 1, clearly dissatisfied; 2, somewhat dissatisfied; 3, neutral; 4, satisfied; 5, very satisfied. The Likert scale is widely used to evaluate postoperative satisfaction in various fields, including thirst and fluid management. Moreover, this simple assessment tool does not significantly increase the nursing workload in high-intensity ICUs.
In this study, basic patient information and perioperative clinical characteristics were extracted from electronic medical records. The blood gas index was the latest blood gas analysis report before extubation. During the 4 h post-extubation period, data on gastrointestinal adverse reactions, aspiration pneumonia, thirst intensity, unstimulated saliva flow rates (USFR), saliva pH, oropharyngeal comfort (halitosis and oral mucosal moisture level), and patient satisfaction were collected by two nurses who had worked for > 5 years and were uniformly trained before data collection.
Outcomes
Primary outcome
The primary outcome was the thirst intensity, which was assessed using the NRS before the hourly intervention as follows: 0, not thirsty; 1–3, mild thirst; 4–6, moderate thirst; and 7–10, severe thirst. In the EOH group, the thirst intensity was evaluated before the intervention every hour; the COH group maintained the NPO status 4 h after extubation, and the thirst intensity was evaluated every hour.
Secondary outcomes
The secondary outcomes were adverse gastrointestinal reactions, aspiration pneumonia, USFR, salivary pH, oral odor, oral mucosal moisture, and patients' satisfaction. Gastrointestinal adverse reactions mainly included nausea and vomiting. Nausea is a subjective, unobservable, unpleasant sensation in the back of the throat and upper abdomen that may or may not cause vomiting and is known as “feeling sick in the stomach.” Vomiting is the oral expulsion of gastrointestinal contents [17]. Nausea and vomiting symptoms of the patients after the intervention were evaluated using the WHO classification standard [18] as follows: 0, no nausea or vomiting; I, mild symptoms, nausea only, no vomiting; II, moderate symptoms, transient vomiting with nausea; III, moderate symptoms, vomiting requiring treatment, and IV, severe symptoms, uncontrollable vomiting. After the intake of water by the patients, the incidence of adverse gastrointestinal reactions was recorded in both groups. If the result of evaluation is greater than 0, the intervention cannot be continued.
Aspiration pneumonia refers to the inflammation of pulmonary parenchymal lesions caused by inhalation of oropharyngeal secretions, food or gastric contents, and other irritants. In addition to considering the risk factors for aspiration (dysphagia, impaired consciousness, impaired cough reflex, nasal feeding, and vomiting) and meeting the diagnostic criteria for pneumonia, the diagnosis of aspiration pneumonia was performed. Chest X-ray film or lung CT scan often shows new infiltration shadows in the posterior segment of the upper lobe or the dorsal segment of the lower lobe and the posterior basal segment, and the right lung is more commonly affected than the left lung. Symptoms can be mild or severe, depending on the amount and nature of inhaled substances. Using chest auscultation, wet rales, burst sounds, or bronchial breathing sounds can be heard. Chest X-ray films can be negative, but infiltration shadows often appear 24–72 h after aspiration; leukopenia (white blood cell count < 4.0 ⋅ 109/L) or leukocytosis (white blood cell count > 10.0 ⋅ 109/L) can repeatedly occur [19]. Pneumonia data were collected within 72 h post-intervention.
The USFR is the volume of saliva obtained per minute (unit: mL/min) without exogenous or drug-induced stimulation; the amount of non-stimulated saliva is measured by spitting the saliva [20]. Within 4 h post-intervention, the patients were instructed to take a semi-reclining position to accumulate saliva, avoid saliva swallowing, and spit saliva in a weighed test tube (including cotton swab) once per minute. The residual saliva in the mouth was wiped with a cotton swab for 5 min, and then the total weight of the saliva was calculated. The saliva density is approximately equal to the density of water. Thus, the USFR was calculated using 1 g/mL. A USFR < 0.1 mL/min indicated insufficient salivary secretion [21]. The saliva pH was tested using precision pH test paper (pH 4.5–9.0, Taizhou Oak Filter Paper Co., Ltd., China). Oral odor was assessed using a halitosis detector (Shenzhen Micro Technology Co., Ltd., China). Patients were instructed to start blowing when the mouth was approximately 5 cm away from the blowing hole. Halitosis is divided into five levels, using scores of 0, 1, 2, 3, and 4; the higher the score, the heavier the halitosis. The state of the lips and mouth was assessed using the oral mucosal moisture score scale: 1, moist lips, moist mouth; 2, dry lips, moist mouth; 3, dry lips, dry mouth; 4, chapped lips, dry mouth [22]. All outcome indexes were evaluated at 1 h post-extubation, immediately before the intervention, and at 4 h post-intervention. Before leaving the ICU, the patients used the 5-point Likert scale [16] to score their satisfaction.
Sample size calculation
In this study, thirst intensity was taken as the primary outcome. Based on the change in the mean ± standard deviation of thirst intensity from 7.4 ± 3.4 pre-intervention to 5.1 ± 3.2 post-intervention [5], the sample size was calculated using the formula that compares the mean of two independent samples. It was concluded that 42 people were needed in each group to provide a two-sided alpha of 0.05 and a one-sided power of 0.9.
Data analysis
Excel was used for data collection and management. Statistical analysis was performed using SPSS 23.0. Continuous variables (age, height, weight, body mass index, arterial blood gas index, thirst intensity, salivary pH, unstimulated saliva flow rate, objective oral mucosa scale, bad breath score, patient satisfaction) with normal distribution are expressed as mean ± standard deviation; whereas those with skewed distribution (endotracheal tube size, intubation duration) are expressed as median and quartile (range). Categorical variables (sex, history of smoking, family history of heart disease, history of diabetes, New York Heart Association class, type of surgery, surgery mode, perioperative and postoperative medications, gastrointestinal adverse reactions, aspiration pneumonia) were expressed as frequency using the chi-square test or Fisher’s exact test. In addition to ANOVA for repeated measurement for thirst intensity, independent sample T test was used for other normally distributed data. Mann–Whitney U test was applied to non-normally distributed data. Results with P < 0.05 were considered statistically significant.