| Abstract|| |
Context: The concomitant use of cuffed endotracheal tubes (ETT) and transesophageal echocardiography (TEE) probes increases ETT cuff pressures (CP), which may contribute to mucosal ischemia and perioperative complications such as failed extubation. Aims: To assess changes in ETT CP after TEE insertion in patients of different age groups undergoing congenital heart surgery and examine the relationship between ETT CP and postoperative extubation failure. Settings and Design: Single-center quality improvement project. Subjects and Methods: ETT CP was measured with a manometer following intubation and again after TEE insertion. Tracheal perfusion pressure was then calculated and postoperative extubation failures were recorded. Statistical Analysis: Chi-square testing, Fisher's-exact testing, one-way analysis of variance testing or Kruskal–Wallis testing with Dunn's pairwise, and student's t-test or Wilcoxon rank-sum testing were used to analyze the data. Results: Median ETT CP increased significantly after TEE insertion in each age group, with infants showing a smaller magnitude of increase (+2 [1-6] cm H2O, P < 0.001) than adults (+12 [8-14] cm H2O, P = 0.008) (intergroup comparison P = 0.002). Five patients (9%) failed extubation, all of which were infants. Within the infant subgroup, no significant difference existed between failed vs successful extubation regarding ETT CP during bypass (15 ± 1 vs 16 ± 2 mmHg, P = 0.206) or tracheal perfusion pressure pre-bypass (34 ± 9 vs 38 ± 11 mmHg, P = 0.518), during bypass (20 ± 9 vs 22 ± 6 mmHg, P = 0.697), or post-bypass (42 ± 9 vs 41 ± 9 mmHg, P = 0.923). There was a significant difference in cardiopulmonary bypass duration (151 ± 29 vs 85 ± 32 min, P < 0.001). Conclusion: Factors beyond intraoperative ETT CP likely play a larger role in postoperative extubation failure.
Keywords: Congenital cardiac anesthesia, endotracheal cuff pressure, extubation failure, transesophageal echocardiography
|How to cite this article:|
Pan SJ, Frabitore SZ, Ingram AR, Nguyen KN, Adams PS. Transesophageal probe placement increases endotracheal tube cuff pressure but is not associated with postoperative extubation failure after congenital cardiac surgery. Ann Card Anaesth 2020;23:447-52
|How to cite this URL:|
Pan SJ, Frabitore SZ, Ingram AR, Nguyen KN, Adams PS. Transesophageal probe placement increases endotracheal tube cuff pressure but is not associated with postoperative extubation failure after congenital cardiac surgery. Ann Card Anaesth [serial online] 2020 [cited 2020 Nov 30];23:447-52. Available from: https://www.annals.in/text.asp?2020/23/4/447/298521
| Introduction|| |
Congenital heart disease (CHD) is the most common congenital defect in newborns affecting approximately 8 per 1,000 live births. Nearly 25% will have critical CHD and require cardiac surgery within their first year of life. Cuffed endotracheal tubes (ETT) and transoesophageal echocardiography (TEE) have become standard practices in congenital cardiac surgery., Although inflating the ETT cuff has been shown to reduce mucosal blood flow in animal studies,, many clinical studies have failed to definitively demonstrate increased airway complications between cuffed versus uncuffed ETTs in humans undergoing surgery.
Adult studies have shown that TEE probe placement significantly increases ETT cuff pressure (CP)., Similar findings have been observed in children during esophagogastroduodenoscopy and TEE probe insertion., Given that neonates and infants are often perfused at a lower blood pressure than adults during cardiopulmonary bypass (CPB) for cardiac surgery, increases in CP from the TEE probe could result in significantly diminished tracheal perfusion. However, the effect of this on postoperative airway complications remains unclear. Because children undergoing cardiac surgery have high extubation failure rates in pediatric intensive care units, which then lead to longer lengths of hospitalization, it is imperative to continue to investigate contributing factors in order to continue to improve outcomes. Currently, our cardiac intensive care unit has an approximate 10% extubation failure rate.
Thus, the primary objective of this quality improvement project was to objectively monitor changes in ETT CP after TEE insertion in patients of different age groups undergoing congenital cardiac surgery with CPB to ensure high CP would be avoided. Second, we followed patients postoperatively to examine if intraoperative tracheal perfusion pressure (assumed to be the mean arterial pressure minus the ETT CP) was associated with postoperative extubation failure and if by checking and resetting the CP, we could reduce the extubation failure rate of our cardiac ICU.
| Subjects and Methods|| |
This was a quality improvement project that occurred at a single institution. This project was approved by the institution's Quality Improvement Review Committee and as a quality improvement project, patient consent was waived. All data were obtained during a single perioperative encounter. All patients regardless of age, who underwent cardiac surgery with CPB and intraoperative TEE were included. Patients with preexisting tracheal or esophageal pathology that precluded the use of TEE could not be included. Our aim was to determine if objective CP measurement would result in reduced postoperative extubation failure. Additional outcome measures included measuring the change in ETT CP after insertion of the TEE probe and to also examine the relationship between tracheal perfusion pressure and postoperative extubation failure. This manuscript adheres to the Standards for QUality Improvement Reporting Excellence (SQUIRE) guidelines for reporting quality improvement projects.
After anesthetic induction, patients were intubated with a cuffed ETT (Mallinckrodt Pharmaceuticals, Staines-Upon Thames, United Kingdom). The ETT cuffs were then inflated to a point where there was a cessation of air leak. For those without an audible air leak with the ETT cuff down, ETTs were exchanged for an ETT one half-size smaller. The ETT CP was then measured using a Posey Cufflator™ ETT Inflator and Manometer (JT Posey Company, Arcadia, CA, USA).
Study of the intervention and measures
The initial post-intubation ETT CP was recorded and then reset between 20 and 25 cm H2O for pressures exceeding that range. Next, the CP was remeasured after TEE probe insertion (resting with the probe tip in the stomach) and the change in pressure recorded. Any pressures exceeding 25 cm H2O were again reset to be between 20 and 25 cm H2O (these pressures were considered to be the ETT CP during CPB). For any patient remaining intubated postoperatively, the CP was measured at the end of the operation and reset to be no greater than 20–25 cm H2O just prior to transport and admission to the intensive care unit.
Demographic variables included age, sex, weight, and body surface area. Preexisting airway abnormalities and the number of intubations attempts were documented. Patients were grouped based on the National Institute of Child Health and Human Development suggestions for pediatric trials: Infants (inclusive of neonates up through 12 months), young children (inclusive of toddlers and early childhood, 1–5 years old), middle childhood (6–11 years old), adolescents (12–18 years old), and adults (>18 years old).
Additional intraoperative covariables recorded include the duration of CPB, use of deep hypothermic circulatory arrest, and extracorporeal membrane oxygenation, mean arterial blood pressure, hemoglobin, arterial oxygen partial pressure, and saturation, and whether the patients were extubated immediately in the operating room prior to intensive care unit admission.
An estimate of tracheal perfusion pressure was calculated by subtracting the ETT CP (after conversion from cm H2O to mmHg using the formula: 1.36 cm H2O = 1 mm Hg) from the average mean arterial pressure for three intraoperative time intervals: pre-bypass, during CPB, and post-bypass. Additionally, the arterial oxygen content (CaO2) was calculated for the same intraoperative time intervals utilizing each patient's average hemoglobin, arterial oxygen partial pressure (PaO2), and oxygen saturation (SaO2) using the equation:
CaO2= (1.36 × hemoglobin (g/dL) × arterial oxygen saturation) + (PaO2 × 0.003)
Patients were followed up during their initial postoperative intensive care unit stay. All postoperative extubation failures were recorded. Extubation failure events that occurred after the patient was transferred to the ward following their initial intensive care unit admission were not considered given that these events were far removed from the effects of intraoperative events.
All data were recorded as count with percentage, mean with standard deviation, or median with interquartile range for non-normally distributed data. The normality of data was assessed using Shapiro–Wilk testing and histograms. No data were transformed. Chi-square testing was used to examine differences in categorical variables with Fisher's exact testing used when appropriate. Multigroup continuous variable differences were analyzed using one-way analysis of variance testing or Kruskal–Wallis testing with Dunn's pairwise comparisons for non-normally distributed data. Bonferroni adjustment of the P value was made for all post hoc pairwise comparisons. Student's t-test or Wilcoxon rank-sum testing were used for pairwise comparison analysis. Statistical analysis was completed using Stata/SE™ 14.2 (StataCorp, College Station, TX, USA).
| Results|| |
Initially, we found that a small amount of air would leak from the ETT cuff with each manometer measurement, especially in the neonates and infants. This resulted in the need for multiple measurements and multiple adjustments of the ETT CP. However, we quickly observed that by leaving the manometer attached to the ETT pilot balloon, as opposed to removing after each measurement, the air leak was eliminated.
A total of 58 patients were included [Table 1]. Initial post-intubation ETT CPs were significantly different between the five age groups with infant initial pressures being significantly lower than all other age groups [Table 2]. There were also significant differences in the proportion of patients with initial CP ≥30 cm H2O between the five age groups [Figure 1]a. After insertion of the TEE probe, all age groups experienced a significant increase in ETT CP (within-group change-in-pressure P value listed within the table cell), however, the magnitude of the ETT CP increase was significantly smaller for the infants when compared against the increase in the adolescents and adults [Table 2]. Similar to the initial ETT CP assessments, there were significant differences in the proportion of patients within each age group who experienced an increase in pressure to ≥30 cm H2O after TEE probe insertion [Figure 1]b.
|Figure 1: Proportion of patients with endotracheal tube (ETT) cuff pressures ≥30 cm H2O. (a) Immediately after intubation. Cuff pressures were then adjusted to be between 20–25 cm H2O prior to transesophageal (TEE) probe insertion. (b) After insertion of the TEE probe|
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Five of the 58 patients studied (9%) failed extubation postoperatively, which was not substantially different than our historic observation of 10% extubation failures. All five of the extubation failure patients were infants. Considering there were 22 infants included (thus 5/22, or 25% of infants experienced extubation failure), we elected to only examine the infant subgroup regarding factors associated with extubation failure [characteristics presented in [Supplemental Table 1]. Only CPB duration was significantly different between the failed versus successful extubation infants, with those failing extubation having nearly twice as long of a bypass duration [Table 3]. Three of the five (60%) extubation failure infants had an ETT in situ at the time of their operation as compared to only 2/17 (12%) of the infants without extubation failure (P = 0.055) [Table 3]. All other infants were successfully intubated on the first attempt. Tracheal perfusion pressure and CaO2 did not differ between the two groups in any of the three intraoperative time intervals [Table 3]. Given the sample size of our infant age group, we were 80% powered to detect a 15 mmHg difference in tracheal perfusion pressure for each of the three intraoperative time intervals (pre-, during, and post-CPB) at an alpha error = 0.05 (logistic regression models for extubation failure for the entire sample with all variables in [Table 3] adjusted for age presented in [Supplemental Table 2]. Characteristics of each of the extubation failure infants are presented in [Table 4].
|Table 3: Characteristics of infants with postoperative extubation failure compared to infants with successful extubation|
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|Table 4: Characteristics of infants who failed extubation postoperatively|
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| Discussion|| |
We observed a statistically significant increase in ETT CP after TEE probe insertion among all age groups, which is consistent with prior studies. Overall, 9% failed extubation, which was similar to our historic outcomes. Infants experienced the smallest magnitude increase in CP with less than 25% experiencing increases to ≥30 cm H2O, which is possibly explained by the high compliance of the newborn's trachea.
Of the five infant extubation failures, none appeared to be correlated with ETT CP, tracheal perfusion pressure, or CaO2. A focused chart review of each of the five postoperative courses revealed that each extubation failure was complicated by a pulmonary and/or cardiac pathologies such as pleural effusion, pneumonia, mucus plugging, hemidiaphragm paralysis, and pericardial effusion as per intensive care unit documentation [Table 4]. Also, a higher proportion of infants with extubation failure had been intubated preoperatively, which may suggest further evaluation of the cumulative duration of intubation and/or requirement for mechanical ventilation preoperatively for infants at risk for postoperative extubation failure are warranted. Additionally, these infants with longer CPB times may have had relatively more complex lesions and therefore may have been more technically challenging to repair from a surgical perspective. These longer bypass times may have resulted in prolonged exposure to the systemic inflammation associated with CPB, perhaps affecting airway/respiratory physiology. The optimal tracheal perfusion pressure during CPB is unknown. While it has been suggested that tracheal capillary perfusion may be occluded at CPs of 25–30 cm H2O in adults,, similar studies in neonates and infants are lacking and therefore we cannot be sure what the “safe” ETT CP is in these age groups. Until these threshold pressures are determined, CP measurements may be a poor surrogate for the evaluation of the anatomic and physiologic causes that lead to extubation failure in infants undergoing congenital cardiac surgery with CPB.
Our observations contradict a recent study by Shinkawa et al. who did not find a relationship between CPB time and extubation failure following pediatric cardiac surgery. Additionally, evidence from Kamata et al. showed that the increases in CP following TEE insertion are transient with the CP returning to values similar to those at baseline when the tip of the TEE probe was advanced into the stomach at the completion of the TEE examination. However, our observations somewhat differed in that the elevated CP we measured were observed while the probe tip was in the stomach. Our data suggest that the presence of the probe within the esophagus, regardless of the tip location, may still cause an increased CP. Thus, it remains inconclusive whether the CP changes recorded with TEE insertion/removal are temporary and/or insignificant, which may help to explain the lack of correlation we observed between tracheal perfusion and extubation failures. Given that many of the studies regarding postoperative extubation failure are from an overall pediatric intensive care unit population with recognition of post-cardiac surgery as a risk factor, more studies aimed at investigating extubation failure specifically in the CHD population are warranted. This population is particularly fragile to the effects of hypercarbia and hypoxia and often undergo extreme operative conditions making them highly vulnerable and highlighting the need for focused studies.
Overall, failed extubation and tracheostomy occur at a rate of 6–13% and 0.2%, respectively, after CHD surgery, and therefore all efforts for optimizing conditions conducive to successful extubation should be implemented at every stage of each patient's perioperative course. Additional studies are warranted to examine intraoperative nonsurgical factors that may contribute to postoperative extubation failure so that management strategies can be optimized to improve postoperative extubation success.
Our project was limited by a presumption that ETT CP remained constant throughout each operation. Kako et al. revealed a drop in ETT CP during hypothermia with a return to baseline pressure with rewarming such that it is likely that when blood pressure is lower during CPB, the ETT CP is lower and therefore tracheal perfusion likely remains fairly constant. Thus, we acknowledge that our tracheal perfusion pressures are not a definitive value, but rather an estimation to be used in an attempt to identify trends. Additionally, while the low variation in our ETT CP data allowed us to have sufficient power to detect significant increases in ETT CP with TEE insertion, we were underpowered to detect clinically relevant differences in tracheal perfusion pressure before, during, and after CPB between those infants with postoperative extubation failures versus those without. Given we were powered to detect an effect size of 15 mmHg, we would have needed to observe mean arterial blood pressures 11, 13, and 16 mmHg, respectively, lower in the extubation failure group during the pre-bypass, bypass, and post-bypass phases to yield statistically significant differences. We do note that a higher proportion in the extubation failure group had undergone deep hypothermic arrest but again we were underpowered to detect whether this and its contribution to low tracheal perfusion was significantly associated with postoperative extubation failure.
| Conclusion|| |
In conclusion, our objective monitoring of the ETT CP and adjustments to keep the ETT CP within the proposed safe range did not substantially reduce our observed postoperative extubation failure rate. TEE probe placement significantly increased the ETT CP in all age groups, although the magnitude of increase was smaller in infants compared to adolescents and adults. It is unclear what effect, if any, this has on the airway and perioperative extubation complications. It appears that time on CPB affects the likelihood of postoperative extubation failure in infants but further studies on the specific mechanism and role of tracheal ischemia are warranted.
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Conflicts of interest
There are no conflicts of interest.
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Phillip S Adams
A-1305 Scaife Hall, 3550 Terrace Street, Pittsburgh - 15261, PA
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2], [Table 3], [Table 4]