Accidental Severe Hypercapnia During Anaesthesia

Abstract

A case report is presented which describes the development, recognition and correction of gross hypercapnia occurring during anaesthesia. The cause of hypercapnia was a high concentration of carbon dioxide in the inspired gas caused by the accidental opening of the control valve for carbon dioxide. Certain structural features of the anaesthetic apparatus facilitated this, and the construction of the Rotameter resulted in the bobbin being concealed at the top of the tube. Recognition of the condition would have been difficult without analysis of arterial blood. The patient did not appear to suffer any overt harm from the incident or its rapid correction by withdrawal of the carbon dioxide from the inspired gas. The aetiology and effects of gross hypercapnia during anaesthesia have been reviewed and special attention has been paid to the problem of measurement of the acid-base abnormality.

Occult Hypercarbia

“…17 At the cardiovascular level, this increased sympathetic activity is counterbalanced by a direct myocardial depressant effect of acidosis. Acute hypercarbia (PaC0 2 , 90 to 100 mm Hg) may lead to narcosis.…”

Respiratory flow characteristics during isoflurane/nitrous oxide anaesthesia

“…Indeed, a moderate increase seems to be beneficial to the patient since cardiac output and coronary blood flow will increase and the systemic vascular resistance drop. Even if high Paco, levels in halothane anaesthesia seem to give cardiac arrhythmias, this threshold is a mean 12.3 kPa during nonsurgical conditions (14) and > 10 kPa during halothane/nitrous oxide anaesthesia and surgery ( 15). With this background the Paco, levels found in the present study must be considered as acceptable, even ifsimilar data, to our knowledge, are lacking for isoflurane.…”

“…There seems to be no simple answer to the question of how high a Paco, is acceptable during anaesthesia with preserved spontaneous breathing. If there is good oxygenation, a moderate rise to about 7.5-8 kPa seems to be harmless ( 14). Indeed, a moderate increase seems to be beneficial to the patient since cardiac output and coronary blood flow will increase and the systemic vascular resistance drop.…”

Predicted normocapnea in infants and children using the Bain circuit with controlled ventilation

“…The high figure used for infants with a body weight of 5 kg is explained by the chosen minimum fresh gas flow of 2 l.min-I. Moderate hypercapnea, defined as a Paco, below 9.5 kPa (71 mmHg) has been found to be harmless to adults during anaesthesia as long as the oxygen saturation is high (21), and the arrhythmogenic threshold will be still higher for halothane anaesthesia (22). Normocapnea was generated in more than 8 out of 10 patients with a wide range of body weights.…”

“…Formulas and nomograms must serve only as guidlines which may be used in routine surgery and when no capnographs are available. Moderate hypercapnea, defined as a Paco, below 9.5 kPa (71 mmHg) has been found to be harmless to adults during anaesthesia as long as the oxygen saturation is high (21), and the arrhythmogenic threshold will be still higher for halothane anaesthesia (22). Due to a relatively high metabolic acidosis because of the preoperative starvation, one might suspect that children would be more sensitive to the negative effects of hypercapnea during anaesthesia than adults.…”