Antero-cervical thermophysiological characterization of obstructive sleep apnea patients.

PURPOSE: Obstructive sleep apnea syndrome (OSAS) is characterized by upper airway inflammation. The aim of this study was to characterize thermal profile of the antero-cervical region in OSAS patients through medical thermal imaging and to compare the respective subjects with non-OSAS individuals. METHODS: Image capture followed the Glamorgan Protocol. A dynamic thermographic examination of the anterior cervical region (at baseline and after a cold stimulus) was conducted in 26 patients diagnosed with overnight polysomnography (PSG). PSG results stratified the subjects into OSAS and non-OSAS groups and their thermograms were compared. RESULTS: Eleven non-OSAS and 15 OSAS subjects were evaluated. Antero-cervical right side (RS) temperature was higher in OSAS group at baseline (p = 0.014). Right side index (RSI) temperature-the difference between RS and submental region, considered as control-was lower in OSAS subjects at baseline (p = 0.020) and 10 min after the cold stimuli was applied (p = 0.008), indicating higher absolute temperatures in this group. Left side index (LSI) was also lower at 10 min in OSAS group (p = 0.021). Statistical correlation was found between apnea-hypopnea index and RS at baseline (r = 0.424, p = 0.031) and at 10 min (r = 0.403, p = 0.041) and RSI at baseline (r = - 0.458, p = 0.019) and 10 min after cold provocation was applied (r = - 0.435, p = 0.025). CONCLUSIONS: OSAS patients have shown higher antero-cervical temperatures compared with non-OSAS counterparts and temperature was associated with severity of the condition. Medical thermography may be a suitable tool in the setting of OSAS suspicion.

Patterns of Hysteresis Between Induction and Emergence of Neuroanesthesia Are Present in Spinal and Intracranial Surgeries.

BACKGROUND: Recovery of consciousness is usually seen as a passive process, with emergence from anesthesia depicted as the inverse process of induction resulting from the elimination of anesthetic drugs from their central nervous system sites of action. However, that need not be the case. Recently it has been argued that we might encounter hysteresis to changes in the state of consciousness, known as neural inertia. This phenomenon has been debated in neuroanesthesia, as manipulation of the brain might further influence recovery of consciousness. The present study is aimed at assessing hysteresis between induction and emergence under propofol-opioid neuroanesthesia in humans using estimated propofol concentrations in both spinal and intracranial surgeries. METHODS: We identified the moments of loss (LOR) and recovery of responsiveness (ROR) in 21 craniotomies and 25 spinal surgeries. Propofol was given slowly until loss of responsiveness and stopped at the end of surgery. An opioid was present at induction and recovery. Propofol infused was recorded and plasma and effect-site concentrations were estimated using 2 pharmacokinetic models. Dose-response curves were generated. Estimated propofol plasma and effect-site concentrations were compared to assess hysteresis. RESULTS: Estimated propofol concentrations at LOR and ROR showed hysteresis. Whether for spinal or intracranial surgeries, the EC50 of propofol at which half of the patients entered and exited the state of responsiveness was significantly different. CONCLUSIONS: Hysteresis was observed between propofol concentrations at LOR and ROR, in both patients presenting for spinal and intracranial surgeries. Manipulation of the brain does not appear to change patterns of hysteresis, suggesting that neural inertia may occur in humans, in a way similar to that found in animal species. These findings justify performing a clinical study in patients using measured propofol concentrations to assess neural inertia.

[Evaluation of Bispectral Index time delay in response to anesthesia induction: an observational study]. / Avaliação do tempo de atraso do índice bispectral na resposta à indução da anestesia: estudo observacional.

BACKGROUND AND OBJECTIVES: According to the manufacturer, the Bispectral Index (BIS) has a processing time delay of 5-10s. Studies addressing this have suggested longer delays. We evaluated the time delay in the Bispectral Index response. METHODS: Based on clinical data from 45 patients, using the difference between the predicted and the real BIS, calculated during a fixed 3minutes period after the moment the Bispectral Index dropped below 80 during the induction of general anesthesia with propofol and remifentanil. RESULTS: The difference between the predicted and the real BIS was in average 30.09±18.73s. CONCLUSION: Our results may be another indication that the delay in BIS processing may be much longer than stated by the manufacture, a fact with clinical implications.

Evaluation of Bispectral Index time delay in response to anesthesia induction: an observational study / Avaliação do tempo de atraso do índice bispectral na resposta à indução da anestesia: estudo observacional

Abstract Background and objectives According to the manufacturer, the Bispectral Index (BIS) has a processing time delay of 5-10 s. Studies addressing this have suggested longer delays. We evaluated the time delay in the Bispectral Index response. Methods Based on clinical data from 45 patients, using the difference between the predicted and the real BIS, calculated during a fixed 3 minutes period after the moment the Bispectral Index dropped below 80 during the induction of general anesthesia with propofol and remifentanil. Results The difference between the predicted and the real BIS was in average 30.09 ± 18.73 s. Conclusion Our results may be another indication that the delay in BIS processing may be much longer than stated by the manufacture, a fact with clinical implications.

Resumo Justificativa e objetivos De acordo com o fabricante, o índice bispectral (BIS) tem um tempo de processamento de cinco a dez segundos. Estudos que avaliaram esse tempo de processamento sugeriram atrasos mais longos. Nós avaliamos o tempo de atraso na resposta do BIS. Métodos Com base em dados clínicos de 45 pacientes, calculamos a diferença entre o tempo de atraso previsto e real do índice bispectral durante um período fixo de três minutos após o momento em que o BIS caiu abaixo de 80 durante a indução da anestesia geral com propofol e remifentanil. Resultados A diferença entre o BIS previsto e real foi em média 30,09 ± 18,73 segundos. Conclusão Nossos resultados sugerem que o atraso no processamento do índice bispectral pode ser muito maior do que o declarado pelo fabricante, um fato com implicações clínicas.