ABSTRACT
To determine whether end-tidal PCO2 (PETCO2) measurements obtained with two infrared capnometers accurately approximates the arterial PCO2 (PaCO2) in critically ill neonates, simultaneous measurements of PETCO2 were obtained from the distal and proximal ends of the tracheal tube with a sidestream capnometer (Puritan Bennett/Datex--BP/D) and from the proximal end with a mainstream capnometer (Hewlett-Packard-HP) in 20 intubated neonates. Distal sidestream PETCO2 and mainstream PETCO2 correlated with the PaCO2 (r2 = 0.66 and 0.61, respectively) within the range of 26-57 mmHg PaCO2. However, proximal PETCO2 with the sidestream capnometer correlated very poorly (r2 = 0.09) with PaCO2. The slope of the least square regression line for the distal sidestream capnometer, 0.67, was significantly less than that for the mainstream capnometer, 0.78 but both were significantly greater than that for the proximal sidestream capnometer, 0.39 (P less than 0.05). The slope of the regression for the proximal sidestream capnometer did not differ significantly from horizontal. Insertion of the mainstream sensor for the HP capnometer significantly increased the transcutaneous CO2 when compared with preinsertion values. We conclude that both distal sidestream and mainstream capnometry provide accurate estimates of the PaCO2 in critically ill neonates.
Subject(s)
Carbon Dioxide/blood , Intensive Care Units, Neonatal , Spirometry/instrumentation , Humans , Infant, Newborn , Monitoring, Physiologic/instrumentation , Partial PressureABSTRACT
To determine the fresh gas flow (FGF) requirements in paediatric patients, we measured the FGFs needed to maintain distal end-tidal PCO2 (PETCO2) values at 30 and 38 mmHg in patients weighing between 3.8 and 20 kg ventilated with either a Sechrist Infant Ventilator IV-100B or an Air-Shields Ventimeter and a Mapleson D circuit. The FGF requirement was 500 ml.kg-1.min-1 to maintain a PETCO2 of 30 mmHg and 250 ml.kg-1.min-1 to maintain a PETCO2 of 38 mmHg when minute ventilation greater than or equal to FGF. When these formulae were used in a subsequent group of similar patients, a wide variation in PETCO2 measurements were obtained. We conclude that the safest and most accurate approach to determine the FGF requirement of paediatric patients is to continuously monitor the PETCO2 in each patient and to adjust the FGF accordingly.
Subject(s)
Anesthesia, General , Carbon Dioxide/blood , Respiration, Artificial , Body Weight , Child , Child, Preschool , Gases , Humans , Infant , Infant, NewbornABSTRACT
Severe liver disease is not a common problem in patients presenting for anaesthesia and surgery. However, because many vital functions are performed by the liver, impairment of these has important implications for the anaesthetist. In addition, since the metabolism and elimination of drugs may be altered, the response of the patient to anaesthetic agents may be unpredictable.
