The aim of this prospective observational study is to evaluate the role of a convective warming blanket to prevent hypothermia during sedation for an endoscopic retrograde cholangiography (ERC).

During endoscopic retrograde cholangiography (ERC), deep medical sedation of the patient is routinely perform. Since ERC is a complex examination and in addition sometimes several intervention steps are necessary (bougienage, dilatation, brush cytology, specimen collection, insertion of plastic and metal stent prostheses), the sedation time is almost always > 30min, in many cases even up to one hour or longer. These patients are at risk for developing hypothermia (drop in core body temperature below 36 degrees Celsius).

It is well known from anesthesiologic research that even moderate perioperative hypothermia, however, can have potentially serious complications. These include increased mortality, cardiac complications such as arrhythmias and infarctions, coagulation disorders, and increased transfusion requirements and wound infections. Changes in serum concentrations of potassium and peripheral vasoconstriction with decrease in subcutaneous partial pressure of oxygen are also clinically important side effects of perioperative hypothermia.

However, the current 2014 German S3 guideline "Sedation in gastrointestinal endoscopy" does not mention peri- or intra-interventional temperature measurement or temperature management.

The aim of this prospective observational study is to evaluate the role of a convective warming blanket to prevent hypothermia during sedation for an ERC. From the description of various clinical endpoints, we seek to obtain sufficient evidence to support routine use of such a system in ERC examinations. This study has the potential to set the new standard for modern sedation during ERC interventions that recognizes the risk of hypothermia and identifies a strategy to avoid it.

For this purpose, we will use a device, that is already routinely used in all operation rooms in Germany, the so-called warm air device "Twinwarm, Generation III". This device has a valid CE mark and will be used according to its purpose "pre-, intra- and postoperative maintenance of the normothermic body temperature of the patient". The device will be used strictly in accordance with the existing in-house SOP "Heat Management" of 04/2021 of the Department of Anesthesiology and Intensive Care Medicine of Hannover Medical School (MHH).

Inclusion criteria:

• Indication to receive repeat (≥ 2 expected interventions) endoscopic retrograde cholangiography (ERC) (The following underlying conditions may be considered as indications for repeat ERC to be performed:
• Primary sclerosing cholangitis (PSC)
• Ischemic type biliary lesion (ITBL) after liver transplantation (LTX)
• Anastomotic stenosis after LTX
• Secondary sclerosing cholangitis (SSC))
• necessary intravenous medical sedation is expected to be required >30min (female and male, age ≥ 18 years).

Exclusion Criteria:

• Patients < 18 years
• Pregnant women

IPD will be shared on reasonable request.