Hypothermia
Conditions
Brief summary
The purpose of this study is to evaluate patients' temperatures after using one of two ventilator circuits (breathing systems): the ANAPOD™ Heat and Humidification System (ANAPOD™ system) or the standard ventilator circuit with a heat-moisture exchanger (standard ventilator). The ANAPOD™ system will provide additional heat and humidity to patients through their breathing tube while the standard ventilator will not. The investigators are doing this research study to find out if the ventilator circuit providing additional heat and humidity will keep patients warmer during surgery and after surgery.
Detailed description
Patients were randomly assigned to either the treatment group or the control group prior to surgery. Prior to induction, patients in the control group were given inspiratory gas at ambient air temperature (20-22 degrees Celsius) and patients in the treatment group were given inspiratory gas at warmed temperatures (40-41 degrees Celsius). All patients were induced with general anesthesia in the supine position and repositioned prone following endotracheal intubation and placement of an esophageal stethoscope with a temperature sensor, as per usual hospital practice. Esophageal temperatures were recorded within 30 minutes of the baseline esophageal temperature and every 10 minutes thereafter for the first hour post-induction. All patients had a blanket and forced air warming applied to their lower extremities and upper back at 43 degrees Celsius after draping. All patients had esophageal temperature measurements recorded every 30 minutes until the patient was repositioned supine. Core temperatures were recorded four hours post-induction for those patients reaching that timeframe.
Interventions
DEVICEHeated Ventilator Circuit
active heat and humidification during anesthesia by warming inspire gases without a heat-moisture exchanger
DEVICEStandard Ventilator Circuit
no active heat and humidification during anesthesia
Sponsors
Westmed, Inc.
Mayo Clinic
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
DOUBLE (Subject, Outcomes Assessor)
Masking description
Patients were randomly assigned to either the treatment group or the control group prior to surgery. Group randomization was performed using a randomization schedule prepared by the Division of Clinical Statistics with patients randomized in blocks of four. For consented and enrolled patients on the day of surgery in the admit areas, a participant was assigned the next sequential participant ID number and the appropriate sealed envelope was opened to reveal the participant's randomized intervention. This occurred before the patient was transferred to the operating suite. Individuals who performed data analysis were blinded to treatment group.
Intervention model description
randomized, trial (treatment or no treatment)
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
* Elective spine surgery anticipated greater than three hours in duration * Posterior approach * An operative site between lumbar one and sacral one * Involving two or more levels with fusion and/or instrumentation and/or revisions * American Society of Anesthesiologists (ASA) Status of I-III
Exclusion criteria
* Patients with a tracheostomy * Preoperative temperature \>38°C or \<36°C on the day of surgery * Active infection or erythema to the back * White blood cell count greater than 10,500/microliter (mcL)
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Core Body Temperature | Approximately four hours post-induction of general anesthesia (or last recorded temperature) | Core body temperature will be taken in the esophagus. The last recorded esophageal temperature will be used for surgeries not reaching 3 hours duration. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Number of Subjects With Post-operative Shivering | Approximately 2 hours after completion of the surgery | Shivering in the post-anesthesia care unit will be assessed using the Bedside Shivering Assessment Scale. This is a 4 point scale and rate shivering as the following: absent, mild, moderate, or severe. Only the highest degree of patient shivering was used in the analysis. |
| Hospital Length of Stay | Surgery to hospital discharge | Number of days in the hospital |
| Intraoperative Core Temperatures Post-induction | Approximately 30 minutes, 60 minutes, 120 minutes post-induction of general anesthesia | Core body temperature will be taken in the esophagus after general anesthesia induction. |
| Number of Participants With Transfusion Within 48 Hours of Surgery | Within 48 hours of surgery | Requirement of blood transfusion within 48 hours of surgery |
| Estimated Blood Loss | duration of surgery | The estimated blood loss per case was determined by the anesthesia provider by measuring the volume of blood in the suction canister while taking into account the amount of irrigation solution used. |
| Overall Post-operative Temperature | PACU arrival | Temperature at Post Anesthesia Care Unit (PACU) arrival. |
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Heated Ventilator Circuit Heated and humidified inspired gases using the ANAPOD™ Heat and Humidification System (Westmed; Tucson, Arizona, USA) circuit prior to induction of general anesthesia in addition to standard ventilation and temperature management.
Heated Ventilator Circuit: active heat and humidification during anesthesia by warming inspire gases without a heat-moisture exchanger | 35 |
| Standard Ventilator Circuit Standard ventilation and temperature management
Standard Ventilator Circuit: no active heat and humidification during anesthesia | 34 |
| Total | 69 |
Baseline characteristics
| Characteristic | Standard Ventilator Circuit | Total | Heated Ventilator Circuit |
|---|---|---|---|
| Age, Continuous | 61 years STANDARD_DEVIATION 12 | 62 years STANDARD_DEVIATION 11 | 63 years STANDARD_DEVIATION 11 |
| American Society of Anesthesiologists (ASA) Status ASA III | 13 Participants | 26 Participants | 13 Participants |
| American Society of Anesthesiologists (ASA) Status ASA I or II | 21 Participants | 43 Participants | 22 Participants |
| BMI | 29.17 kg/m^2 STANDARD_DEVIATION 5.9 | 28.69 kg/m^2 STANDARD_DEVIATION 5.25 | 28.21 kg/m^2 STANDARD_DEVIATION 4.61 |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Asian | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Black or African American | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) More than one race | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 2 Participants | 3 Participants | 1 Participants |
| Race (NIH/OMB) White | 32 Participants | 66 Participants | 34 Participants |
| Region of Enrollment United States | 34 Participants | 69 Participants | 35 Participants |
| Sex: Female, Male Female | 16 Participants | 34 Participants | 18 Participants |
| Sex: Female, Male Male | 18 Participants | 35 Participants | 17 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | 0 / 35 | 0 / 34 |
| other Total, other adverse events | 5 / 35 | 3 / 34 |
| serious Total, serious adverse events | 0 / 35 | 0 / 34 |
Outcome results
Primary
Core Body Temperature
Core body temperature will be taken in the esophagus. The last recorded esophageal temperature will be used for surgeries not reaching 3 hours duration.
Time frame: Approximately four hours post-induction of general anesthesia (or last recorded temperature)
Population: One subject in the standard group was not included in any of the analyses as this subject's intraoperative temperature was unavailable as part of the anesthetic record.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Heated Ventilator Circuit | Core Body Temperature | 36.8 degrees Celsius | Standard Deviation 0.2 |
| Standard Ventilator Circuit | Core Body Temperature | 36.8 degrees Celsius | Standard Deviation 0.2 |
p-value: 0.807t-test, 2 sided
p-value: 0.35895% CI: [-0.085, 0.237]ANCOVA
Secondary
Estimated Blood Loss
The estimated blood loss per case was determined by the anesthesia provider by measuring the volume of blood in the suction canister while taking into account the amount of irrigation solution used.
Time frame: duration of surgery
Population: One subject in the standard group was not included in any of the analyses as this subject's intraoperative temperature was unavailable as part of the anesthetic record.
| Arm | Measure | Value (MEDIAN) |
|---|---|---|
| Heated Ventilator Circuit | Estimated Blood Loss | 450 milliters |
| Standard Ventilator Circuit | Estimated Blood Loss | 425 milliters |
p-value: 0.40495% CI: [-100, 250]Wilcoxon (Mann-Whitney)
Secondary
Hospital Length of Stay
Number of days in the hospital
Time frame: Surgery to hospital discharge
Population: One subject in the standard group was not included in any of the analyses as this subject's intraoperative temperature was unavailable as part of the anesthetic record.
| Arm | Measure | Value (MEDIAN) |
|---|---|---|
| Heated Ventilator Circuit | Hospital Length of Stay | 3 number of days |
| Standard Ventilator Circuit | Hospital Length of Stay | 3 number of days |
p-value: 0.67295% CI: [-1, 1]Wilcoxon (Mann-Whitney)
Secondary
Intraoperative Core Temperatures Post-induction
Core body temperature will be taken in the esophagus after general anesthesia induction.
Time frame: Approximately 30 minutes, 60 minutes, 120 minutes post-induction of general anesthesia
Population: One subject in the standard group was not included in any of the analyses as this subject's intraoperative temperature was unavailable as part of the anesthetic record.~Data was obtained from 33 subjects in the treatment group at 60 minutes post-induction.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Heated Ventilator Circuit | Intraoperative Core Temperatures Post-induction | ~30 minutes | 36.1 degrees Celsius | Standard Deviation 0.5 |
| Heated Ventilator Circuit | Intraoperative Core Temperatures Post-induction | ~60 minutes | 35.8 degrees Celsius | Standard Deviation 0.6 |
| Heated Ventilator Circuit | Intraoperative Core Temperatures Post-induction | ~120 minutes | 36.1 degrees Celsius | Standard Deviation 0.5 |
| Standard Ventilator Circuit | Intraoperative Core Temperatures Post-induction | ~30 minutes | 36.1 degrees Celsius | Standard Deviation 0.4 |
| Standard Ventilator Circuit | Intraoperative Core Temperatures Post-induction | ~60 minutes | 35.8 degrees Celsius | Standard Deviation 0.5 |
| Standard Ventilator Circuit | Intraoperative Core Temperatures Post-induction | ~120 minutes | 36.1 degrees Celsius | Standard Deviation 0.4 |
Comparison: \~30 minutes post-inductionp-value: 0.82395% CI: [-0.3, 0.2]t-test, 2 sided
Comparison: \~60 minutes post-induction. Data was obtained from 33 subjects in the treatment group.p-value: 0.85395% CI: [-0.2, 0.3]t-test, 2 sided
Comparison: \~120 minutes post-inductionp-value: 0.98695% CI: [-0.2, 0.2]t-test, 2 sided
Secondary
Number of Participants With Transfusion Within 48 Hours of Surgery
Requirement of blood transfusion within 48 hours of surgery
Time frame: Within 48 hours of surgery
Population: One subject in the standard group was not included in any of the analyses as this subject's intraoperative temperature was unavailable as part of the anesthetic record.
| Arm | Measure | Group | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|---|
| Heated Ventilator Circuit | Number of Participants With Transfusion Within 48 Hours of Surgery | No transfusion | 21 Participants |
| Heated Ventilator Circuit | Number of Participants With Transfusion Within 48 Hours of Surgery | Transfusion | 14 Participants |
| Standard Ventilator Circuit | Number of Participants With Transfusion Within 48 Hours of Surgery | No transfusion | 23 Participants |
| Standard Ventilator Circuit | Number of Participants With Transfusion Within 48 Hours of Surgery | Transfusion | 11 Participants |
p-value: 0.61995% CI: [0.5, 3.7]Fisher Exact
Secondary
Number of Subjects With Post-operative Shivering
Shivering in the post-anesthesia care unit will be assessed using the Bedside Shivering Assessment Scale. This is a 4 point scale and rate shivering as the following: absent, mild, moderate, or severe. Only the highest degree of patient shivering was used in the analysis.
Time frame: Approximately 2 hours after completion of the surgery
Population: One subject in the standard group was not included in any of the analyses as this subject's intraoperative temperature was unavailable as part of the anesthetic record.
| Arm | Measure | Group | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|---|
| Heated Ventilator Circuit | Number of Subjects With Post-operative Shivering | Post-operative shivering | 8 Participants |
| Heated Ventilator Circuit | Number of Subjects With Post-operative Shivering | No post-operative shivering or not assessed | 27 Participants |
| Standard Ventilator Circuit | Number of Subjects With Post-operative Shivering | Post-operative shivering | 5 Participants |
| Standard Ventilator Circuit | Number of Subjects With Post-operative Shivering | No post-operative shivering or not assessed | 29 Participants |
Comparison: Post-operative shivering observedp-value: 0.5495% CI: [0.5, 5.9]Fisher Exact
Secondary
Overall Post-operative Temperature
Temperature at Post Anesthesia Care Unit (PACU) arrival.
Time frame: PACU arrival
Population: One subject in the standard group was not included in any of the analyses as this subject's intraoperative temperature was unavailable as part of the anesthetic record.~Data was obtained from 32 subjects in the treatment group.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Heated Ventilator Circuit | Overall Post-operative Temperature | 36.6 degrees Celsius | Standard Deviation 0.4 |
| Standard Ventilator Circuit | Overall Post-operative Temperature | 36.6 degrees Celsius | Standard Deviation 0.4 |
Comparison: Data was obtained from 32 subjects in the treatment group.p-value: 0.57195% CI: [-0.2, 0.1]t-test, 2 sided