Acute hyperventilation increases the central venous-to-arterial PCO2difference in stable septic shock patients.
BACKGROUND
To evaluate the effects of acute hyperventilation on the central venous-to-arterial carbon dioxide tension difference (∆PCO2) in hemodynamically stable septic shock patients.


METHODS
Eighteen mechanically ventilated septic shock patients were prospectively included in the study. We measured cardiac index (CI), ∆PCO2, oxygen consumption (VO2), central venous oxygen saturation (ScvO2), and blood gas parameters, before and 30 min after an increase in alveolar ventilation (increased respiratory rate by 10 breaths/min).


RESULTS
Arterial pH increased significantly (from 7.35 ± 0.07 to 7.42 ± 0.09, p < 0.001) and arterial carbon dioxide tension decreased significantly (from 44.5 [41-48] to 34 [30-38] mmHg, p < 0.001) when respiratory rate was increased. A statistically significant increase in VO2(from 93 [76-105] to 112 [95-134] mL/min/m2, p = 0.002) was observed in parallel with the increase in alveolar ventilation. While CI remained unchanged, acute hyperventilation led to a significant increase in ∆PCO2(from 4.7 ± 1.0 to 7.0 ± 2.6 mmHg, p < 0.001) and a significant decrease in ScvO2(from 73 ± 6 to 67 ± 8%, p < 0.001). A good correlation was found between changes in arterial pH and changes in VO2(r = 0.67, p = 0.002). Interestingly, we found a strong association between the increase in VO2and the increase in ∆PCO2(r = 0.70, p = 0.001).


CONCLUSIONS
Acute hyperventilation provoked a significant increase in ∆PCO2, which was the result of a significant increase in VO2induced by hyperventilation. The clinician should be aware of the effects of acute elevation of alveolar ventilation on ∆PCO2.
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France. mallatjihad@gmail.com.|Intensive Care Unit, Centre Hospitalier d'Arras, Boulevard Georges Besnier, 62022, Arras Cedex, France. mallatjihad@gmail.com.
Jihad
http://orcid.org/0000-0001-6372-7360
J
Mallat
Intensive Care Unit, Centre Hospitalier d'Arras, Boulevard Georges Besnier, 62022, Arras Cedex, France.
Usman
U
Mohammad
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.|Intensive Care Unit, Centre Hospitalier d'Arras, Boulevard Georges Besnier, 62022, Arras Cedex, France.
Malcolm
M
Lemyze
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.
Mehdi
M
Meddour
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.|Intensive Care Unit, Centre Hospitalier d'Arras, Boulevard Georges Besnier, 62022, Arras Cedex, France.
Marie
M
Jonard
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.
Florent
F
Pepy
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.
Gaelle
G
Gasan
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.
Stephanie
S
Barrailler
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.
Johanna
J
Temime
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.
Nicolas
N
Vangrunderbeeck
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.
Laurent
L
Tronchon
Department of Anesthesiology and Critical Care Medicine, Service de Réanimation polyvalente, Centre Hospitalier du Dr. Schaffner, 99 route de La Bassée, 62307, Lens Cedex, France.|Intensive Care Unit, Centre Hospitalier d'Arras, Boulevard Georges Besnier, 62022, Arras Cedex, France.
Didier
D
Thevenin
Acute hyperventilation; Central venous oxygen saturation; Central venous-to-arterial CO2 tension gap; Oxygen consumption; Septic shock