Apnea testing in suspected brain dead children - physiological and mathematical modelling

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Abstract

Objective: To study the validity and safety of the traditional apnea test in children, and to evaluate a mathematical equation estimating the hemodynamic response to the apnea test. Design: A prospective clinical study. Setting: Pediatric ICU Patients and participants: 38 pediatric patients suffering severe brain injury aged 2 months to 17 years, undergoing apnea testing for brain death. Measurements and results: Apnea tests were performed 61 times (once in 19 patients, twice in 15, and 3 times in 4 patients). Mean PaCO2 was 41.1±10.6 mmHg before apnea and increased to 68.0±17.6 at 5 min. PaCO2 increased to 81.8±20.1 and 86.0±25.6 at 10 and 15 min, respectively. There was a mean PaCO2 increase by 5.38±1.4 mmHg/min in the first 5 min, and 2.75±0.5 mmHg/min during the next 5 min. We found a statistically significant (p<0.05) linear relationship between the natural logarithm of PaCO2, time, and the logarithm of the initial level of PaCO2. An inverse linear relationship (p<0.05) was found between systemic mean arterial pressure (MAP) and initial level of PaCO2 presented as mathematical correlations and nomograms. Conclusions: By using our model for predicting MAP and PCO2 prior to apnea testing, hemodynamic embarrassment can be anticipated and prevented, thus allowing a safer procedure in the detection of brain death. Despite the fact that continuous cardiorespiratory monitoring is important, hemodynamic disturbances can be estimated before the apnea test, thus allowing a safer approach to brain death detection.

Original languageEnglish
Pages (from-to)247-252
Number of pages6
JournalIntensive Care Medicine
Volume21
Issue number3
DOIs
StatePublished - Mar 1995

Keywords

  • Apnea test
  • Brain death
  • Hypercapnia

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