Optimal Site for Precordial Stethoscope Placement in Pediatric Patients Younger than Two Years: A Preliminary Cross-sectional Study

Background: The precordial stethoscope is a traditional and non-invasive monitoring method during pediatric general anesthesia. In this preliminary cross-sectional study, we aimed to investigate the characteristics of lung and heart sounds via precordial stethoscope and determine the optimal site for auscultation in children below 2 years of age. Methods: This study involved 68 patients who underwent general anesthesia with tracheal intubation. Auscultation sounds via precordial stethoscope were recorded in MP3 format at the following three sites: Site A-region between the clavicle and nipple on the left midclavicular line; Site B-region between the nipple and costal arch on the left midclavicular line; and Site C-point on the left midaxillary line that was horizontally leveled with Site B. Eight blinded evaluators individually and randomly scored lung and heart sounds on a 10-point scale (0: cannot hear at all and 10: can hear clearly). Results: Lung sound scores at Sites A, B, and C were 8.0 (7.0–9.0), 4.5 (2.9–6.0), and 7.0 (5.5–8.5), respectively, while heart sound scores at Sites A, B, and C were 3.5 (2.0–6.0), 6.5 (4.0–8.0), and 1.0 (0.4–2.0), respectively. Statistically significant differences were found in all pairs of sites. Conclusion: We suggest that Site A, where anesthesiologists can hear both the lung and heart sounds, is the optimal site of precordial stethoscope attachment during general anesthesia for intubated children below 2 years of age.

Anesthesia for rabbits submitted to experimental surgeries: Report of a series of eight anesthesias

Anesthesia for laboratory animals is a matter of biomedical concern and one of the most present dilemmas in the current bioethical debate. The use of anesthetic agents in experimental surgery aims at analgesia and restraining the animal, in order to achieve a reasonable degree of muscle relaxation and to produce sufficient analgesia. This practice requires the use of protocols for the administration of safe and efficient doses. Eight New Zealand rabbits were submitted to laparotomies demonstrating the surgical technique discipline of the local medical course. For pre-anesthetic medication, acepromazine 1 mg.kg-1 associated with ketamine 15 mg.kg-1 was used subcutaneously. Anesthesia was maintained with isoflurane and oxygen under a laryngeal mask in a Mapleson D anesthesia system and under spontaneous breathing. Hydration was performed with 10 ml.kg-1 saline every hour. A thermal mattress was used. Precordial stethoscope, pulse oximetry and clinical parameters were used for monitoring. For euthanasia, ketamine 10 mg.kg-1 associated with potassium chloride 19.1% 1 ml.kg-1 was used intravenously. The average weight of the rabbits was 2721.25 ± 275.01 grams and the duration of the anesthetic procedure was 120 ± 87 minutes. Discussion. In long-term anesthesia, such as laparotomies, the use of pre-anesthetic medication and then anesthetic induction by the combination of agents is recommended. However, anesthetic management requires monitoring to prevent insufficient or excessive doses from occurring.

Ventilation—Observation, Capnography, and Precordial Stethoscope

A variety of monitoring techniques can be used to ensure adequate ventilation during sedation. Three of the methods are direct observation, precordial/pretracheal stethoscope, and end-tidal CO2 monitoring. Direct observation is simple and effective but may miss subtle changes and is difficult when the room is darkened or the patient is covered. Precordial stethoscopes are frequently utilized during dental procedures and can help detect changes in respiration or the need for suctioning. MRI-compatible versions are available, but the practitioner needs to be within 4 feet of the patient. End-tidal CO2 monitoring gives the most information about the adequacy of ventilation but requires costly equipment and placement of a specialized nasal cannula or mask on the child’s face. The benefit of utilizing any of these modalities is that changes in ventilation will precede changes in oxygenation. Hence, early recognition of change can help prevent respiratory compromise.

The Stethoscope: Applications and Limitations– An Analysis of 2000 Incident Reports

The first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS) were analysed with respect to the role of the oesophageal or precordial stethoscope as a continuous monitor. There were 1099 of the 1256 incidents during general anaesthesia in which one might have been used in this way, but use was reported in only 65 cases (5%), predominantly during paediatric cases. In only one report, a cardiac arrest, was the stethoscope the first to detect the incident. In a theoretical analysis it was considered that the stethoscope, used on its own for continuous monitoring, could have detected 54% of the 1256 incidents (almost 25% before any potential for organ damage), had they been allowed to evolve. However, AIMS data suggest that the actual yield using a stethoscope as a continuous monitor may be much lower than this, and that even the use of a “mobile” stethoscope can not be relied upon to detect oesophageal or endobronchial intubation. These reports confirm that there is limited use of the stethoscope for continuous monitoring in current anaesthetic practice in Australia; it has been superseded by the sophisticated electronic monitors now available. However, in areas with limited resources continuous auscultation with a stethoscope remains a basic requirement.