The goal of this observational study is to learn about the effect of menstrual cycle on postoperative shivering in women of fertile age. The main question it aims to answer is:

- Do women in the luteal phase have less postoperative shivering? Participants will have their intraoperative body temperature recorded and will be observed for postanesthetic shivering, depending on whether they are in the luteal phase or follicular phase.

Postoperative shivering is a protective mechanism that the body uses to raise body temperature by rhythmic muscle contractions during hypothermia. Peroperative hypothermia is the most important cause of shivering after recovery. Shivering not only causes a decrease in patient comfort and discomfort but also increases metabolic demand by increasing oxygen consumption. This is an undesirable situation.

Women's hormonal status affects body temperature control. During the luteal phase, progesterone levels increase and this results in a 0.4 °C increase in core body temperature. The threshold for vasodilation also increases during this phase. Therefore, thermoregulation also changes during the luteal phase. Core body temperature in the follicular and luteal phase does not change with exposure to cold. However, under general anesthesia, core temperature is significantly reduced in both the luteal and follicular phase. Thermoregulatory vasoconstriction is less inhibited during luteal phase anesthesia.

The primary aim of our study was to determine the relationship between different phases of the menstrual cycle and the frequency of postoperative shivering. The secondary aim was to evaluate the incidence of intraoperative hypothermia and the duration of onset of intraoperative hypothermia in different phases of the menstrual cycle.

The study is planned as a prospective cross-sectional observational study. Female patients aged 18-45 years with ASA (American Society of Anesthesiology) score I-II who will undergo elective surgery for open technique septoplasty or rhinoplasty will be included in the study. They will be recorded in two groups as follicular group (F) and luteal group (L).

Patients data will be recorded;

• Demographic data
• Primary disease
• Comorbidities
• American Society of Anesthesiologists (ASA) Physical Status Classification
• The phase of the menstrual cycle (luteal or follicular phase) according to the patient's medical history
• Core body temperatures will be noted in the preoperative waiting area, before induction of general anesthesia, 1st hour under general anesthesia, 2nd hour under general anesthesia, 3rd hour under general anesthesia and in the postanesthetic recovery unit.
• Anesthesia and duration of surgery
• Infusion fluid quantity
• Pain level in the postoperative recovery unit (numerical rating scale-NRS)
• Postoperative tremors
• PAS (postanesthetic shivering scale) value SPSS statistical program for Windows will be used for statistical analysis of the results. Considering the number of surgeries performed in previous periods, it was predicted that approximately 100 patients could be included in the study within this period. This period, which was determined to ensure homogeneous distribution of the groups, will be extended if necessary and more patients will be included in the study. Parametric descriptive values will be given as mean and standard deviation, and non-parametric values will be given as n (%) and median and IQR (interquartile range). The conformity of the data to normal distribution will be evaluated by one sample Kolmogorov-Smirnov test. Comparisons of quantitative data conforming to normal distribution will be made with Student T test and comparisons of data not conforming to normal distribution will be made with Mann Whitney U test. Chi-Square test will be used to compare qualitative data. For the analyses, the significance level will be accepted as p<0.05 at 95% confidence interval.

Inclusion Criteria:

• Female patients undergoing elective open technical septoplasty or rhinoplasty
• 18-45 years of age
• ASA score I-II

Exclusion Criteria:

• Patient-legal representative does not want to be included in the study
• Emergency surgery
• Use of drugs that affect cardiovascular function, heat balance and hormone levels (e.g. combined oral contraceptives)
• Menstrual irregularity
• Polycystic ovary syndrome
• Thyroid disease
• Autonomic disease
• Reyno disease
• Uncontrolled diabetes mellitus
• Uncontrolled hypertension
• Surgeries where the duration of anesthesia is less than 1 hour
• Patients with NRS pain score above 7 in the recovery unit after anesthesia
• Core body temperature below 36°C before induction of general anesthesia

Female patients scheduled for elective nose surgery