Oxygenator exhaust capnography as an index of arterial carbon dioxide tension during cardiopulmonary bypass using a membrane oxygenator.

We have studied the relationship between the partial pressure of carbon dioxide in oxygenator exhaust gas (PECO2) and arterial carbon dioxide tension (PaCO2) during hypothermic cardiopulmonary bypass with non-pulsatile flow and a membrane oxygenator. A total of 172 paired measurements were made in 32 patients, 5 min after starting cardiopulmonary bypass and then at 15-min intervals. Additional measurements were made at 34 degrees C during rewarming. The degree of agreement between paired measurements (PaCO2 and PECO2) at each time was calculated. Mean difference (d) was 0.9 kPa (SD 0.99 kPa). Results were analysed further during stable hypothermia (n = 30, d = 1.88, SD = 0.69), rewarming at 34 degrees C (n = 22, d = 0, SD = 0.84), rewarming at normothermia (n = 48, d = 0.15, SD = 0.69) and with (n = 78, d = 0.62, SD = 0.99) or without (n = 91, d = 1.07, SD = 0.9) carbon dioxide being added to the oxygenator gas. The difference between the two measurements varied in relation to nasopharyngeal temperature if PaCO2 was not corrected for temperature (r2 = 0.343, P = < 0.001). However, if PaCO2 was corrected for temperature, the difference between PaCO2 and PECO2 was not related to temperature, and there was no relationship with either pump blood flow or oxygenator gas flow. We found that measurement of carbon dioxide partial pressure in exhaust gases from a membrane oxygenator during cardiopulmonary bypass was not a useful method for estimating PaCO2.

Adrenaline administered via a nebulizer in adult patients with upper airway obstruction.

Racemic adrenaline administered via a nebulizer has been used successfully in children with upper airway obstruction resulting from croup and postintubation oedema. We report four adult cases of upper airway obstruction of differing aetiologies successfully managed with the administration of adrenaline via a nebulizer (1 mg in 5 ml of normal saline and repeated as necessary). This appears to be safe and effective in selected cases of upper airway obstruction with immediate benefits and few cardiovascular sequelae.