Heat loss during carbon dioxide insufflation: comparison of a nebulization based humidification device with a humidification and heating system.

INTRODUCTION: This study compared the heat loss observed with the use of MR860 AEA Humidifier™ system (Fisher & Paykel Healthcare, New Zealand), which humidifies and heats the insufflated CO(2), and the use of the AeronebPro™ device (Aerogen, Ireland), which humidifies but does not heat the insufflated CO(2). METHODS: With institutional approval, 16 experiments were conducted in 4 pigs. Each animal, acting as its own control, was studied at 8-day intervals in randomized sequence with the following four conditions: (1) control (C) no pneumoperitoneum; (2) standard (S) insufflation with nonhumidified, nonheated CO(2); (3) Aeroneb™ (A): insufflation with humidified, nonheated CO(2); and (4) MR860 AEA humidifier™ (MR): insufflation with humidified and heated CO(2). RESULTS: The measured heat loss after 720L CO(2) insufflation during the 4 h was 1.03 ± 0.75 °C (mean ± SEM) in group C; 3.63 ± 0.31 °C in group S; 3.03 ± 0.39 °C in group A; and 1.98 ± 0.09 °C in group MR. The ANOVA showed a significant difference with time (p = 0.0001) and with the insufflation technique (p = 0.024). Heat loss in group C was less than in group S after 60 min (p = 0.03), less than in group A after 70 min (p = 0.03), and less than in group MR after 150 min (p = 0.03). The heat loss in group MR was less than in group S after 50 min (p = 0.04) and less than in group A after 70 min (p = 0.02). After 160 min, the heat loss in group S was greater than in group A (p = 0.03). DISCUSSION: As far as heat loss is concerned, for laparoscopic procedures of less than 60 min, there is no benefit of using any humidification with or without heating. However, for procedures greater than 60 min, use of heating along with humidification, is superior.

Changes in core temperature during peritoneal insufflation: comparison of two CO2 humidification devices in pigs.

BACKGROUND: Various modifications of the physical status of CO2 have been used to reduce hypothermia caused by flow of insufflating gas. This animal study aimed to investigate the effects on core temperature, of insufflation with CO2 using two different humidification devices: unheated, humidified CO2 using the Modified-Aeroneb system (Nektar, San Carlos, CA) and warmed, humidified CO2 using the HME-Booster (Medisize, Hillegom, The Netherlands). METHODS: We undertook a prospective four-session study on a homogeneous group of four pigs. After general anesthesia, all animals were treated successively with the following protocols in a randomized order at 8-d intervals: Control (no pneumoperitoneum), Standard (unheated, unhumidified CO2), Modified-Aeroneb (unheated, humidified CO2 by cold nebulization), HME-Booster (heated, humidified CO2). The core temperature of the animals was recorded every 10 min. RESULTS: The temperature decrease is significantly influenced by time (P=0.0001; ANOVA), by the insufflation method (P=0.01), and by the interaction between time and the insufflation method (P=0.0001). The method of contrasts showed the following results:--The temperature decrease in the Standard group and HME-Booster group became greater than in the Control group after 40 min (P=0.02)--The temperature decrease in the Modified-Aeroneb group became greater than in the Control group after 100 min (P=0.04)--The temperature decrease in the Modified-Aeroneb group was less than in the HME-Booster group after 40 min (P=0.04) and less than in the Standard group after 60 min (P=0.01)--The temperature decrease in the Standard group was greater than in the HME-Booster group after 160 min (P=0.005). CONCLUSIONS: Compared with the HME-Booster system, the Modified-Aeroneb is at least as effective in limiting the drop in core temperature during laparoscopic insufflation.

Learning fibreoptic intubation with a virtual computer program transfers to 'hands on' improvement.

BACKGROUND AND OBJECTIVE: Fibreoptic intubation is an essential skill in anaesthesiology that is challenging to learn in the clinical setting. The goal of this study was to evaluate 'virtual fibreoptic intubation' (VFI) software as an adjunct to the traditional fibreoptic intubation teaching. METHODS: After informed consent, 42 undergraduate medical students were randomized into two groups. The 'control group' was taught conventionally by an expert bronchoscopist with a 1 h lecture. In addition to the didactic lecture by the expert, the 'VFI group' was given the VFI CD-ROM, and students self-trained with the software until they felt competent performing a virtual fibreoptic bronchoscopy on the normal patient models. Students were evaluated 2 weeks later on their first orotracheal fibreoptic intubation of an airway manikin. The primary endpoint was success, as evaluated by a staff anaesthesiologist blinded to the group of teaching. Fibreoptic intubation ability was the secondary endpoint. RESULTS: The fibreoptic intubation success rate was significantly higher in the VFI group than in the control group (81 versus 52%, P < 0.05). Among 10 failures in the control group, nine were due to oesophageal intubation as compared with only one out of four in the VFI group. Among four failures in the VFI group, three were because of taking longer than 4 min as compared with only one out of 10 in the control group. The VFI group tended towards better ability in the procedural skills of fibreoptic intubation than the control group. CONCLUSION: Self-training in fibreoptic intubation with the VFI software may improve the acquisition of fibreoptic intubation skills.

Methylene blue dye, an accurate dye for sentinel lymph node identification in early breast cancer.

PURPOSE: The aim of this prospective study was to analyze the safety of methylene blue dye (MBD) and compare its efficacy with that of isotopic mapping for sentinel lymph node (SLN) identification in breast cancer. PATIENTS AND METHODS: The SLN procedure, involving isotopic mapping and MBD (subareolar intraparenchymal injections of 2 mL, 10 mg/mL), was performed on 100 patients with early breast cancer. RESULTS: The procedure was safe with a success rate of 99%; SLNs were, respectively, found in 65% by MBD, in 73% by lymphoscintigraphy and in 94% by gamma-probe. Out of 40 metastatic SLNs, 37 were "hot" and 32 stained. Digital examination allowed the detection of 2 additional metastatic LNs. CONCLUSION: MBD is safe and combination mapping associated with digital examination is the superior method. Modification of the procedure, favouring injections of dilute MBD (4 mL, 1.25 mg/mL) increases MBD efficiency (90%) and maintains low rates of complications.

Cold nebulization used to prevent heat loss during laparoscopic surgery: an experimental study in pigs.

BACKGROUND: Prolonged abdominal laparoscopy is responsible for a significant drop in core body temperature. Various modifications of the conditioning for the insufflating carbon dioxide (CO(2)) to prevent the specific hypothermia related to the insufflated gas have been tested. This study aimed to investigate the effects on core temperature of insufflation with unheated humidified CO(2) using the Aeroneb system compared with the use of standard gas and gas made hot and wet using a warming and humidifying system (Pall system). METHODS: A prospective four-session study was conducted to investigate a homogeneous group of four pigs. After inducation of general anesthesia, all the animals were treated successively with the following protocols in a randomized order at 8-day intervals: control (no pneumoperitoneum), standard (unheated, unhumidified CO(2)), Aeroneb (unheated, humidified CO(2) by cold nebulization), and Pall (heated, humidified CO(2)). The core temperature of the animals was recorded every 10 min. RESULTS: Analysis of variance (ANOVA) confirmed a difference between the insufflation conditions in the evolution of temperature over time (p = 0.004). The method of contrast showed the following results. After 30 min, the core temperature of the Aeroneb group fell significantly less than that of the standard group (p = 0.036). After 100 min, the core temperature of the Pall group fell significantly less than that of the standard group (p = 0.024). After 80 min, the core temperature of the standard group fell significantly more than that of the control group (p = 0.035). In the Aeroneb group, the core temperature dropped less than in the Pall and control groups, but the difference did not reach statistical significance. CONCLUSIONS: Cold humidification of insufflating CO(2) prevents heat loss associated with pneumoperitoneal insufflation at least as efficaciously as warmed humidification of the gas.

Calibrated pneumoperitoneal venting to prevent N2O accumulation in the CO2 pneumoperitoneum during laparoscopy with inhaled anesthesia: an experimental study in pigs.

UNLABELLED: Nitrous oxide (N2O) accumulates in the CO2 pneumoperitoneum during laparoscopy when N2O is used as an adjuvant for inhaled anesthesia. This may worsen the consequences of gas embolism and introduce a fire risk. In this study, we quantified the pneumoperitoneal gas venting necessary to prevent significant contamination by inhaled N2O. Four domestic pigs (26-30 kg) were anesthetized and ventilated with 66% N2O in oxygen. A CO2 pneumoperitoneum was insufflated and maintained at a pressure of 12 mm Hg. Each animal underwent three experimental conditions, in random sequence, for 70 min each: 1) no pneumoperitoneal leak, 2) leak of 2 L every 10 min (12 L/h), and 3) leak of 4 L every 10 min (24 L/h). Every 10 min, pneumoperitoneal gas samples were analyzed for fractions (FPn) of N2O and CO2. Without leaks, FPnN2O increased continually and reached 29.58% +/- 3.15% at 70 min. With leaks of 2 and 4 L every 10 min (12 and 24 L/h), FPnN2O reached a plateau of <10% after 30 min. We conclude that calibrated pneumoperitoneal venting of 12 or 24 L/h is enough to prevent the constitution of potentially dangerous pneumoperitoneal gas mixtures if venting is constant. IMPLICATIONS: External venting calibrated at four or eight initial pneumoperitoneal volumes per hour with compensation by fresh CO2 is sufficient to prevent nitrous oxide buildup of more than 10% in the pneumoperitoneum during laparoscopy with inhaled general anesthesia if venting is constant.