Ursachen perioperativer Hypothermie: Einfluss von Prämedikation und Vorwärmung auf die perioperative Körperkerntemperatur mittels nicht-invasiver SpotOn-Messung bei kardiochirurgischen Patienten
Causes of perioperative hypothermia: Influence of oral premedication and prewarming on core temperature of cardiac surgical patients measured with non-invasive SpotOn measurement
von Michaela Maria Müller
Datum der mündl. Prüfung:2020-03-12
Erschienen:2020-03-05
Betreuer:Prof. Dr. Anselm Bräuer
Gutachter:Prof. Dr. Anselm Bräuer
Gutachter:PD Dr. Alexander von Hammerstein-Equord
Dateien
Name:Dissertation MichaelaMMüller Final ohne Leb...pdf
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Zusammenfassung
Englisch
BACKGROUND: Perioperative hypothermia is still very common and associated with numerous adverse effects for example a higher risk for ischaemic cardiac events, wound infection and uncomfortable feeling of the patients. The effects of benzodiazepines, administered as premedication, on thermoregulation have been studied with conflicting results. We investigated the hypotheses that premedication with flunitrazepam would lower the preoperative core temperature and that prewarming could reduce, stop or even compensate this effect. Furthermore, it should be examined how well the new non-invasive temperature measurement method SpotOn matches with nasopharyngeal and vesical temperature measurement method. METHODS: After approval by the local research ethics committee 50 adult cardiac surgical patients were included in this prospective, randomized, controlled study with two groups. Core temperature was measured using a continuous, non-invasive zero-heat-flux thermometer (SpotOn) from approximately 30 min before administration of the oral premedication until 30 min after cardiopulmonary bypass. An equal number of patients was randomly allocated via a computer-generated list assigning them to either prewarming or control group. In the prewarming group patients received active prewarming using an underbody forced-air warming blanket. The data were analysed using Student’s t-test, Mann-Whitney U-test and Fisher’s exact test. From the beginning of surgery the forced-air warming blanket was also started in the control group. From this point on, the body core temperature was also measured nasopharyngeally and vesically. The temperature measurements were statistically evaluated using Bland and Altman. RESULTS: 24 patients per group could be analysed. Initial core temperature was 36.7 ± 0.2 °C and dropped significantly after oral premedication to 36.5 ± 0.3°C when the patients were leaving the ward and to 36.4 ± 0.3°C before induction of anaesthesia. The patients of the prewarming group had a significantly higher core temperature at the beginning of surgery (35.8 ± 0.4°C vs. 35.5 ± 0.5 °C, p = 0.027), although core temperature at induction of anaesthesia was comparable. Despite prewarming, core temperature did not reach baseline level prior to premedication (36.7 ± 0.2 °C). Incidence of Hypothermia at the beginning of surgery was significantly lower in the prewarming group (45.8%) than in the control group (79.2%). The mean difference (Bias) between forehead zero-heat-flux and nasopharyngeal temperature was 0.03°C with a precision of ±0.57°C (95% limits of agreement). The mean difference between forehead zero-heat-flux and vesical temperature was 0.1°C (95% limits of agreement ±1.57°C), the mean difference between nasopharyngeal and vesical temperature 0.07°C (95% limits of agreement ±1.78°C). CONCLUSION: Oral premedication with benzodiazepines on the ward lowered core temperature significantly at arrival in the operating room. This drop in core temperature cannot be offset by a short period of active prewarming. But prewarming significantly reduced the incidence of hypothermia. The new non-invasive core temperature measurement method SpotOn is an alternative to the nasopharyngeal measurement.
Keywords: perioperative hypothermia; premedication; prewarming; zero-heat-flux
Schlagwörter: Perioperative Hypothermie; Prämedikation; Vorwärmung; Null-Wärmefluss