The aim of the study is to evaluate a patient prewarming concept following the recommendations of the S3-guideline "Prevention of perioperative hypothermia" with respect to incidence and complications of perioperative hypothermia. The study hypothesis is that postoperative core temperature in adult patients after prewarming is significantly higher than in patients who were treated following actual standard protocol (passive insulation).

The aim of the study is to evaluate a patient prewarming concept following the recommendations of the new german S3-guideline "Prevention of perioperative hypothermia" with respect to incidence and complications of perioperative hypothermia. Prewarming should enable the patients to preserve their core temperature for a longer period and to avoid perioperative hypothermia.The study hypothesis is that postoperative core temperature in adult patients after prewarming is significantly higher than in patients who were treated following the actual standard protocol (passive insulation).

Inclusion Criteria:

• patients scheduled for elective general or orthopedic surgery with expected duration > 45 min
• American Society of Anesthesiologists physical status 1-3
• age > 17 years

Exclusion Criteria:

• emergency surgery
• patient's denial
• unexpected decrease of duration of anesthesia < 45 min
• preoperative body temperature > 38 °C

Patients of FEK Hospital Neumünster scheduled for elective surgery under defined conditions (see below)