Pilot study of closed-loop anaesthesia for liver transplantation

A system theory based digital model for predicting the cumulative fluid balance course in intensive care patients

Background: Surgical interventions can cause severe fluid imbalances in patients undergoing cardiac surgery, affecting length of hospital stay and survival. Therefore, appropriate management of daily fluid goals is a key element of postoperative intensive care in these patients. Because fluid balance is influenced by a complex interplay of patient-, surgery- and intensive care unit (ICU)-specific factors, fluid prediction is difficult and often inaccurate. Methods: A novel system theory based digital model for cumulative fluid balance (CFB) prediction is presented using recorded patient fluid data as the sole parameter source by applying the concept of a transfer function. Using a retrospective dataset of n = 618 cardiac intensive care patients, patient-individual models were created and evaluated. RMSE analyses and error calculations were performed for reasonable combinations of model estimation periods and clinically relevant prediction horizons for CFB. Results: Our models have shown that a clinically relevant time horizon for CFB prediction with the combination of 48 h estimation time and 8-16 h prediction time achieves high accuracy. With an 8-h prediction time, nearly 50% of CFB predictions are within ±0.5 L, and 77% are still within the clinically acceptable range of ±1.0 L. Conclusion: Our study has provided a promising proof of principle and may form the basis for further efforts in the development of computational models for fluid prediction that do not require large datasets for training and validation, as is the case with machine learning or AI-based models. The adaptive transfer function approach allows estimation of CFB course on a dynamically changing patient fluid balance system by simulating the response to the current fluid management regime, providing a useful digital tool for clinicians in daily intensive care.

Orthotopic Liver Transplantation in a Patient with Acutely Decompensated Liver Disease and Personal History of Malignant Hyperthermia

Introduction

Orthotopic liver transplants are characterized by sudden changes in hemodynamics, intraoperative hemorrhage, metabolic and electrolyte derangements, and arrhythmias. Many of these features are also hallmarks of malignant hyperthermia episodes and make differentiation difficult intraoperatively. Additionally, the treatment for malignant hyperthermia, dantrolene, can cause hepatotoxicity in already damaged native livers and newly reperfused organ allografts. Thus, it is imperative to avoid a triggering anesthetic in these patients. Here we report on a successful total intravenous anesthetic in a malignant hyperthermia susceptible individual undergoing an orthotopic liver transplant for acutely decompensated end-stage liver disease. Case Presentation. A 49-year-old male with a past medical history significant for malignant hyperthermia episodes as a child was admitted with decompensated alcoholic cirrhosis. He underwent uneventful total intravenous general anesthesia with propofol and sufentanil continuous infusions for an orthotopic liver transplant. He required minimal vasoactive agents to maintain a mean arterial blood pressure >65 mmHg and was extubated on postoperative day 1.

Conclusions

Total intravenous anesthesia is necessary for patients with a personal history of malignant hyperthermia. However, this type of general anesthesia is difficult in the setting of fluctuating hemodynamics, hemorrhage, and changes in drug metabolism and clearance during the anhepatic and reperfusion phases of an orthotopic liver transplant. Propofol and sufentanil continuous infusions provided stable hemodynamics and an excellent plane of anesthesia throughout the case and should be considered in other individuals undergoing this procedure who require a total intravenous anesthetic.

The Requirement of Isoflurane and Remifentanil During Liver Transplantation Using Bispectral Index and Surgical Pleth Index: An Observational Study

BACKGROUND

During liver transplantation (LT), patients and surgical factors potentially influence the pharmacokinetics of the anesthetic agents. The aim of this study was to investigate the requirement of isoflurane and remifentanil according to severity of liver disease during LT under balanced anesthesia.

METHODS

We enrolled 44 patients undergoing LT. Anesthetic depth was maintained within the bispectral index score of 40 to 60 and Surgical Pleth Index of 20 to 60. Patients were divided into 2 groups according to their median Model for End-Stage Liver Disease (MELD) score: low MELD group and high MELD group. We compared end-tidal inhaled anesthetics and remifentanil consumption.

RESULTS

Patients were divided into 2 groups according to median value of MELD score: MELD score <16 (low MELD group; n = 20) or MELD ≥16 (high MELD group; n = 20). There was no significant difference between the 2 groups in end-tidal concentration of isoflurane during 3 phases. However, the remifentanil requirement was lower in the high MELD group during the dissection and anhepatic phases (mean (SD), 0.105 (0.067) vs 0.064 (0.055) µg/kg/min; P = .037, and 0.167 (0.096) vs 0.108 (0.079) µg/kg/min; P = .039, respectively; low MELD group vs high MELD group) with no significant difference during the neohepatic phase.

CONCLUSIONS

The severity of liver dysfunction based on MELD score affected the intraoperative remifentanil requirement during LT. Patients with cirrhosis are required to use analgesics appropriate to their individual patient characteristics in clinical practice.

Nociceptive stimulation during Macintosh direct laryngoscopy compared with McGrath Mac videolaryngoscopy: A randomized trial using indirect evaluation using an automated administration of propofol and remifentanil

BACKGROUND

Decrease of the nociceptive stimulation induced by laryngoscopy could be an advantage for patients without risk of difficult intubation. The present study aimed to compare the difference in nociceptive stimulation between the use of a conventional laryngoscope or of a videolaryngoscope. Amount of nociception was assessed indirectly using the peak remifentanil concentration determined by a closed-loop administration of propofol and remifentanil with bispectral index (BIS) as the input signal (target 50).

METHODS

A prospective single-center randomized study was performed including surgical patients without predictable risk of difficult mask ventilation or of difficult tracheal intubation. Forty consecutive surgery patients were randomly assigned to CL group (conventional laryngoscope) or VL group (McGrath Mac videolaryngoscope). Induction of anesthesia was performed automatically using the closed-loop system and myorelaxation with atracurium. The allocation was revealed just before tracheal intubation. The primary outcome was the peak plasma remifentanil concentration observed during the 5-minute period which followed intubation.

RESULTS

Sixteen patients in the CL group and 11 in the VL group were analyzed. Plasmatic remifentanil and propofol concentrations were similar in both groups either before tracheal intubation or during the 5 minutes following intubation. There was a nonsignificant between-group difference (P = .09) for the peak concentration of remifentanil. A comparable result was observed for other outcomes except for the heart rate which increased in the CL group.

CONCLUSION

Use of the videolaryngoscope McGrath Mac did not reduce the nociceptive stimulation induced during intubation as evaluated by the automatically administered remifentanil concentration.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02245789.

Association of Polymorphisms in Pharmacogenetic Candidate Genes with Propofol Susceptibility

Significant individual susceptibility to intravenous anesthetic propofol exists. The etiology of individual variability in the response to propofol may be influenced by genetic polymorphisms in metabolic and functional pathways. With current pharmacogenetics and modern molecular biology technologies, it is possible to study the influence of genetic polymorphisms on susceptibility to propofol. When inducing general anesthesia with intravenous propofol, high individual susceptibility to propofol was found. Using Sequenom MassARRAY single-nucleotide polymorphism (SNP) genotyping, we identified a mutation (rs6313) in the 5HT2A gene that was correlated to individual susceptibility to propofol effect-site concentration (Cep) and onset time of propofol induction. Carriers of the minor allele (G) of 5HT2A rs6313 required less propofol (20% decrease in Cep) and less time (40% decrease in onset time) to induce anesthesia. Moreover, associations were found between the gamma-aminobutyric acid (GABA) receptor SNP rs2279020 and the SCN9A SNP rs6746030 and the susceptibility of bispectral index (BIS) after propofol-induced anesthesia. In addition, dominant mutations in GABAA1 rs2279020, GABAA2 rs11503014, and CHRM2 rs1824024 were putatively associated with cardiovascular susceptibility to propofol anesthesia. No gene-gene interactions were found through a standardized measure of linkage disequilibrium and a multifactor dimensionality reduction analysis. Our results suggest that genetic polymorphisms related to mechanisms of propofol anesthesia are involved in propofol susceptibility.