Overview
During long operations on the abdomen, patients often get cold. Doctors call this perioperative hypothermia. Even a small drop in body temperature can cause problems, such as more bleeding, wound infection, and a longer stay in hospital.
To keep patients warm during surgery, doctors usually blow warm air over the body through a special blanket. However, the fluids that patients receive through a vein during surgery are normally at room temperature. These cool fluids may lower the body temperature from the inside.
This study compares two ways of keeping patients warm during operations on the abdomen that last three hours or longer.
Everyone taking part receives warm air blown over the body. In addition, one group receives fluids into a vein at room temperature, about 23 °C, which is the usual practice. The other group receives the same fluids warmed to 39 °C by a special device just before the fluid enters the vein.
Participants are placed into one of the two groups by chance, like flipping a coin. Because of the nature of the treatment, the doctors caring for the patient know which group the patient is in.
The researchers measure body temperature before, during, and at the end of surgery. They also record blood pressure, the medicines used to support blood pressure, the amount of fluid given, the amount of urine produced, and blood tests taken on the day after surgery.
This is a pilot study. Its main purpose is to find out whether a larger study would be possible. The researchers want to learn how many patients can be enrolled, whether the treatment can be given exactly as planned, and how complete the collected information is. The results will be used to plan a larger study.
Description
Design and setting.
Single-centre, randomised, parallel-group, open-label pilot trial conducted at a regional clinical hospital in Saint Petersburg, Russian Federation. Participants are allocated in a 1:1 ratio to a control group or a study group.
Anaesthesia and warming protocol.
All participants receive general anaesthesia according to a standardised institutional protocol, and ambient operating room temperature is kept constant. In both groups, forced-air warming is applied through an upper body blanket at an airflow temperature of 37 °C from induction of anaesthesia until the end of surgery. In the control group, balanced crystalloid solutions are stored at 23 °C and infused without additional warming. In the study group, the same solutions are actively warmed to a target temperature of 39 °C using a medical fluid warmer positioned as close as possible to the venous access site.
Measurements.
Axillary and oesophageal temperature are recorded before induction of anaesthesia, hourly during surgery, and at transfer to the intensive care unit. Haemodynamic variables, the use and infusion rate of norepinephrine, intraoperative crystalloid volume and urine output are recorded throughout surgery. Stroke volume, cardiac output and extracellular fluid volume are assessed by tetrapolar impedance rheography. Base excess, plasma lactate, C-reactive protein and the SOFA score are recorded on the first postoperative day.
Randomisation and allocation concealment.
The allocation sequence is generated using random number tables. Allocation is concealed by sequentially numbered, sealed, opaque envelopes, opened after eligibility is confirmed and written informed consent is obtained. Blinding of the anaesthesia team is not feasible because of the nature of the intervention.
Withdrawal criteria.
Participants are withdrawn from analysis in case of withdrawal of informed consent, errors in data recording, or intraoperative change in the extent of the planned surgical procedure.
Feasibility assessment.
In addition to the clinical outcome measures, the following feasibility parameters are recorded: the proportion of screened patients who are eligible and randomised, the proportion of eligible patients who consent, adherence to the allocated intervention, the proportion of randomised participants with analysable data, and completeness of data for the primary outcome measure. These parameters will be used to determine whether a definitive multicentre trial is feasible and to inform its sample size.
Eligibility
Inclusion Criteria:
- Signed written informed consent
- Age 18 years or older
- Scheduled abdominal surgery with an expected duration of at least 3 hours
Exclusion Criteria:
- Pregnancy or breastfeeding
- End-stage chronic somatic disease
- Axillary temperature above 37.0 °C before surgery
- Documented thermoregulatory disorder of any origin, including disorders due to ongoing infectious or autoimmune disease or traumatic brain injury
- Chronic heart failure stage 2 according to the classification of the Russian Society of Cardiology
- Active infection before surgery
