Hyperventilation versus standard ventilation for infants in postoperative care for congenital heart defects with pulmonary hypertension.
OBJECTIVE
In infants undergoing surgery for cardiac defects with left-to-right shunt, a hyperventilation strategy has been applied to prevent pulmonary hypertensive crisis (PHC). Hyperventilation with a large tidal volume and/or higher airway pressure, however, may be detrimental to the lung. This randomized study compared the effects of hyperventilation versus standard ventilation.


METHODS
We enrolled 22 infants with a preoperative pulmonary-to-systemic blood pressure ratio of more than 0.7. Hyperventilation, with a tidal volume of 10-12 ml x kg(-1) to keep Pa(CO2) between 30 and 35 mmHg, was randomly applied in 11 patients for 16 h or more. The other 11 patients were randomly assigned to standard ventilation, with a 6- to 8- ml x kg(-1) tidal volume.


RESULTS
The peak inspiratory pressure was higher (20 +/- 3 vs 18 +/- 2 cmH2O; P = 0.018), and Pa(CO2) (34 +/- 5 vs 42 +/- 7 mmHg; P = 0.003) and positive end-expiratory pressure (3 +/- 0 vs 5 +/- 0; P < 0.0001) were significantly lower in the hyperventilation than in the standard ventilation group. The Pa(CO2)/inspiratory fraction of oxygen Pa(CO2) ratio decreased from 244 +/- 160 mmHg at the onset of postoperative ventilation, to 177 +/- 96 mmHg at 24 h (P = 0.038) in the hyperventilation group, versus a decrease from 240 +/- 89 to 220 +/- 97 mmHg in the standard ventilation group not significant (NS). Serum interleukin (IL)-6 level, measured at 24 h postoperatively, was significantly lower (P = 0.02) in the standard ventilation than in the hyperventilation group, suggesting an attenuated postoperative systemic inflammatory response. A single patient in each group developed PHC.


CONCLUSIONS
Hyperventilation may cause lung injury and systemic inflammation in infants with pulmonary hypertension undergoing corrective heart surgery.
Umenai
Takako
T
Department of Anesthesiology and Intensive Care, University Hospital, Kyoto Prefectural School of Medicine, Kyoto, Japan.
Shime
Nobuaki
N
Hashimoto
Satoru
S
D001794:Blood Pressure / Q000502:physiology; D002097:C-Reactive Protein / Q000378:metabolism; D002245:Carbon Dioxide / Q000097:blood; D006348:Cardiac Surgical Procedures / Q000379:methods*; D005260:Female; D006330:Heart Defects, Congenital / Q000601:surgery*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000601:surgery*; D006985:Hyperventilation; D007223:Infant; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D010100:Oxygen / Q000097:blood; D010865:Pilot Projects; D011175:Positive-Pressure Respiration; D011182:Postoperative Care / Q000379:methods*; D011652:Pulmonary Circulation; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial; D016896:Treatment Outcome
D015850:Interleukin-6; D002245:Carbon Dioxide; D002097:C-Reactive Protein; D010100:Oxygen