Objectives: Pediatric orthotopic liver transplant recipients frequently need mechanical ventilation during the immediate posttransplant period. However, intensive care unit beds are costly and scarce; therefore, anticipating which patients will require postoperative mechanical ventilation support is important. In addition, immediate postoperative extubation may reduce the incidence of postoperative respiratory complications and improve patient outcomes after orthotopic liver transplant. Here, we aimed to determine the predictors of need for mechanical ventilation after orthotopic liver transplant in pediatric patients.
Materials and Methods: We retrospectively analyzed the records of 57 pediatric patients who underwent orthotopic liver transplant (performed by the same team at Baskent University Hospital from April 1996 to August 2009). Patients were divided into 2 groups according to whether they required postoperative mechanical ventilation or not. Collected data included demographic features; comorbidities; cause of liver failure; perioperative laboratory values; intraoperative hemodynamic parameters; use and volume of crystalloids, colloids, and blood products; albumin levels; portal vein clamping time, requirement of inotropes/vasopressors; and anesthesia duration.
Results: Mean age and body weight of patients were 25.0 ± 23.1 months and 10.8 ± 5.3 kg, respectively. Of 57 patients, 26 (46%) needed postoperative mechanical ventilation. Compared with those who did not require postoperative mechanical ventilation, patients who required mechanical ventilation had growth failure (P = .03), higher mean intraoperative lactate level (P = .03), and higher mean intraoperative fresh frozen plasma/erythrocyte suspension (P = .049) and intraoperative vasopressor (P = .022) requirements. Multivariate logistic regression analysis revealed that growth failure (odds ratio = 37; P = .03) and higher intraoperative lactate level (odds ratio = 1.5; P = .03) were predictors of the need for mechanical ventilation.
Conclusions: About 46% of our pediatric orthotopic liver transplant recipients required mechanical ventilation postoperatively. Growth failure and higher intraoperative lactate levels were associated with need for postoperative mechanical ventilation.
Key words : Early extubation, Lactate, Mechanical ventilation
Pediatric recipients of orthotopic liver transplant (OLT) generally require mechanical ventilation during the early postoperative period. In recent years, there have been reports related to intraoperative early extubation in OLT patients1,2; however, these studies have included a small series of patients, and pediatric recipients of OLT were not included. It is known that prolonged mechanical ventilation not only causes diminished physical and financial hospital sources but also markedly increases the risk of infection and complications. Early extubation of patients after OLT might decrease these risks.3 It is essential to determine which patients will require postoperative ventilation to reduce the costs and incidence of early postoperative extubation-related respiratory complications and to improve the prognosis after OLT. The aim of this study was to determine the predictors of need for mechanical ventilation in young recipients (0 to 6 years old) of liver transplant by using preoperative and intraoperative data.
Materials and Methods
After we obtained approval from the Ethics Committee of our hospital (Project No. KA10/06), the records of 57 pediatric patients who underwent OLT were retrospectively analyzed. Transplant procedures were performed by the same team at Baskent University Hospital from April 1996 to August 2009. After standardization of the anesthesia and analgesia applications according to our clinic’s protocol, patients between 0 and 6 years old who had living-donor OLT were included in the study. All donors were first-degree relatives. We included PICCO system (Pulsion Medical System, Munich, Germany) measurements taken during the OLT procedure, 2 hours after the start of OLT, at the anhepatic phase and afterward, and before extubation in our analyses. Pediatric OLT recipients were categorized into 2 groups with regard to their need for postoperative mechanical ventilation, with 31 patients not requiring mechanical ventilation after transplant and 26 patients requiring mechanical ventilation after transplant.
The main criteria for extubation after OLT included hemodynamic stability (hypotension should not be present) and normothermia. Other criteria included patients who were awake and able to follow oral commands, sufficient ventilation (regular breathing pattern with respiratory rate of < 30 breaths/min, above 95% oxygen saturation in room air, end-tidal carbon dioxide concentration of 30-40 mm Hg), complete reversal of neuromuscular blockade, arterial blood gas analysis results in the normal range, and adequate hemostasis. For patients younger than 2 years old, crying and extremity movements were accepted as criteria. After intraoperative extubation, all patients were transferred to the intensive care unit and monitored. Measurements that were monitored included electrocardiography, peripheral oxygen saturation, respiratory rate, urine output, and radial artery and central venous pressure. In the intensive care unit, patients received respiratory physiotherapy, prophylactic antibiotherapy, nutritional support, liquid infusion, and supplemental oxygen to maintain oxygen saturation by pulse oximetry above 94%. Scanned parameters are shown in Table 1.
Data analyses were performed by using SPSS 17.0 software (Statistical Package for Social Sciences, SPSS Inc., Chicago, IL, USA). To compare the 2 patient groups, t test was used for variables that were homogeneously distributed, whereas those that were not homogeneously distributed were analyzed by using the Mann-Whitney U test. Chi-square test was used for noncontinuous (categorical) variables. To determine risk factors for postoperative mechanical ventilation requirements, logistic regression analyses were performed for parameters that showed statistically or clinically significant difference. P values < .05 were accepted as significant.
There were no significant differences in demographic features of patients with and without postoperative mechanical ventilation (for all variables compared, P > .05). Patients with and without need for postoperative mechanical ventilation had no statistically significant differences with regard to hepatic encephalopathy, ascites, growth retardation, Pediatric End-Stage Liver Disease (PELD) score, Child-Pugh score, and additional diseases (P > .05). No statistically significant differences were found between the 2 groups with regard to preoperative hemoglobin, hematocrit, blood urea nitrogen, creatinine, potassium, alanine transaminase, aspartate transaminase, albumin, direct bilirubin, prothrombin time, and international normalized ratio values (for all variables compared, P > .05). However, preoperative sodium levels were significantly lower in the group that did not require postoperative mechanical ventilation (P = .012) (Table 2).
With regard to operation duration, no significant difference was found between the 2 groups. In addition, the 2 groups had no significant differences in total volume of crystalloid and colloid solutions administered during the intraoperative period (P = .223, P = .888). There were no significant differences between the groups with regard to intraoperative maximum and minimum blood pressure levels; central venous pressure; lowest body temperature; worst oxygen saturation in arterial blood gas analysis; values of pH, oxygen and carbon dioxide partial pressures, and bicarbonate; urine output; and ratio of erythrocyte suspension and fresh frozen plasma replacement to weight. However, the group that required postoperative mechanical ventilation had significantly higher lactate levels (P = .038). Maximum intraoperative body temperature was also statistically higher in the group that required postoperative mechanical ventilation, although not to the level of clinical significance (P = .033) (Table 3).
When the 2 groups were compared with regard to mean intraoperative hypotension and bradycardia, no significant differences were found (P = .475 and P = .394, respectively); however, vasopressor needs in the group that required postoperative mechanical ventilation were significantly more frequent (P = .015). When duration of postoperative intensive care unit stay and postoperative inotrope needs were evaluated, no significant differences were found between the 2 groups (P = .953 and P = .376, respectively). Mortality in the group that required postoperative mechanical ventilation requirement was found to be statistically higher (P = .049) (Table 4).
Logistic regression analysis was used to evaluate the parameters that were considered to be clinically and statistically significant and consistent with the literature. According to the results of this analysis, growth retardation and intraoperative highest lactate level were determined as independent risk factors (Table 5).
In our study, we found that 46% of the patients required postoperative mechanical ventilation, and growth retardation and intraoperative lactate levels were shown to be independent risk factors for requiring postoperative mechanical ventilation. When duration of postoperative intensive care and inotrope needs were evaluated, no statistically significant differences were observed between the 2 groups. Mortality was found to be statistically higher in the group that required postoperative mechanical ventilation.
Because timing and criteria of extubation are critical in children, the continuation of ventilation after transplant has been frequently accepted as standard of care. The reasons that extubation are not preferred in children include concerns about graft function and small diameters of vessels, depressive effects of opiate analgesics, presence of growth retardation, and incompatibility of graft-recipient dimensions.4 Emotional and comprehension dif-ferences between children and adults and the inability of cooperation in children during the early postoperative period have generated additional concerns for postoperative early extubation. However, early extubation provides avoidance from nosocomial pneumonia, accidental extubation, aspiration of gastric content, subglottic edema, decreased blood pressure, and deterioration of splanchnic blood circulation due to forced intravenous sedation and intermittent positive pressure ventilation. For these reasons, it is crucial to determine factors that affect the timing of postoperative extubation.
Biancofiore and colleagues5 reported a model that predicted whether extubation would be successful in patients who had final-term liver disease score under 11. Mandell and colleagues6 suggested that encephalopathy and body mass index > 34 kg/m2 were predictors of failed early intubation. In another study, Mandell and colleagues1 mentioned preoperative and intraoperative criteria of successful early extubation. Preoperative criteria were described as United Network for Organ Sharing score 2B/3, absence of additional diseases, age below 50 years, lack of encephalopathy, and intraoperative criteria (including fully functioning donor liver, erythrocyte suspension need of < 10 units, no vasopressor need, and alveolar-arterial oxygen gradient < 150 mm Hg).1 Cammu and colleagues7 reported that patients could be extubated if they did not have acute hepatic failure and encephalopathy in the preoperative period and had normal donor liver function (normal pH, no sign of clinical bleeding, and prothrombin time longer than 25%), erythrocyte suspension need of < 10 units, alveolar-arterial oxygen gradient of < 200 mm Hg, and stabilized hemodynamics (adrenaline or noradrenaline infusion of < 200 ng/kg/min) during the intraoperative period. Consistent with the literature, the vasopressor need, which was included in the intraoperative criteria, was significantly higher in patients who required postoperative mechanical ventilation (P = .015) in our study. In logistic regression analysis, this factor was not found to be a significant predictor (P = .226).
Glanemann and colleagues8 reported that the presence of preoperative encephalopathy and body mass index above 34 kg/m2 were risk factors for early extubation in a study of adults. In our study, the presence of a growth retardation (according to the description in PELD score estimations) in pediatric patients was more frequently observed in the group that required postoperative mechanical ventilation; however, this finding was not significant (P = .061).
Another intraoperative parameter that may be a predictor of postoperative mechanical ventilation requirement is the body temperature. Biancofiore and colleagues5 and Mandell and colleagues1 found that the body temperature of patients who required postoperative mechanical ventilation was significantly lower at the time of admission to the intensive care unit. Although intraoperative body temperature was found to be statistically higher in patients who did not require mechanical ventilation in our study, this difference was not considered to be clinically significant (P = .02). Khosravi and colleagues9 reported that the duration of the operation was statistically longer in the group of patients who required postoperative mechanical ventilation. However, in our study, the duration of operation in both groups was statistically similar.
The limitations of our study include the small number of patients and its retrospective design.
Risk of requirement for postoperative mechanical ventilation in children was associated with growth retardation and elevated lactate levels in the intraoperative arterial blood gas analysis.
DOI : 10.6002/ect.2019.0312
From the 1Department of Anesthesiology, Acibadem Maslak Hospital, Istanbul; and
the Departments of 2Anesthesiology and 3General Surgery, Baskent University
Faculty of Medicine, Ankara, Turkey
Acknowledgements: The authors have no sources of funding for this study and have no conflicts of interest to declare.
Corresponding author: Aytekin Ünlükaplan, Acibadem Maslak Hospital, Darüssafaka, Buyukdere Cd. No:40, 34457 Sarıyer, Istanbul, Turkey
Phone: +90 532 722 82 42
Table 1. Parameters Collected From Study Patients
Table 2. Laboratory Results Collected During the Preoperative Period (mean ± SD)
Table 3. Blood Gas and Other Laboratory Results Collected During the Intraoperative Period
Table 4. Parameters Collected During the Postoperative Period
Table 5. Results of Logistic Regression Analysis