Carbon Dioxide Tensions During Anesthesia in the Prone Position

The effect of spinal versus general anesthesia on intraocular pressure in lumbar disc surgery in the prone position: A randomized, controlled clinical trial

OBJECTIVE

To compare IOP changes between spinal anesthesia (SA) and general anesthesia (GA) in patients who underwent lumbar disc surgery in the prone position.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Operating room.

PATIENTS

Forty ASA I-II patients scheduled for lumbar disc surgery in prone position.

INTERVENTION

Patients were randomly allocated to the SA or GA groups.

MEASUREMENTS

IOP was measured before anesthesia (IOP1), 10 min after spinal or general anesthesia in supine position (IOP2), 10 min after being placed in the prone position (IOP3), and at the end of the operation in the prone position (IOP4).

MAIN RESULTS

There was no significant difference between baseline IOP1 (group GA = 19.4 ± 3.2 mmHg; group SA = 18.6 ± 2.4 mmHg) and IOP2 values (group GA = 19.7 ± 4.1 mmHg; group SA = 18.4 ± 1.9 mmHg) between and within the groups. IOP values after prone positioning and group GA measurements (IOP3 = 21.6 ± 3.1 mmHg; IOP4 = 33.9 ± 3.1 mmHg) were significantly higher when compared with the SA group (IOP3 = 19.3 ± 2.7 mmHg, IOP4 = 26.9 ± 2.4 mmHg) (p = 0.018 and p < 0.001, respectively). Furthermore, IOP3 was significantly increased when compared with IOP2 in the GA group but not in the SA group (p = 0.019 and p = 0.525, respectively). In both groups, IOP4 values were significantly higher than the other three measurements (p < 0.001).

CONCLUSION

The results indicated that IOP increase is significantly less in patients who undergo lumbar disc surgery in the prone position under SA compared with GA.

The Effect of Pressure-Controlled Ventilation and Volume-Controlled Ventilation in Prone Position on Pulmonary Mechanics and Inflammatory Markers

The aim of this present study is to compare the effect of pressure-controlled ventilation and volume-controlled ventilation on pulmonary mechanics and inflammatory markers in prone position. The study included 41 patients undergoing to vertebrae surgery. The patients were randomized into two groups: Group 1 received volume-controlled ventilation, while group 2 received pressure-controlled ventilation. The demographic data, pulmonary mechanics, the inflammatory marker levels just after the induction of anesthetics, at the 6th and 12th hours, and gas analysis from arterial blood samples taken at the beginning and the 30th minute were recorded. The inflammatory marker levels increased in both groups, without any significant difference among groups. Peak inspiratory pressure level was higher in the volume-controlled ventilation group. This study revealed that there is no difference regarding inflammatory marker levels between volume- and pressure-controlled ventilation.

Effects of prone position on alveolar dead space and gas exchange during general anaesthesia in surgery of long duration

BACKGROUND AND OBJECTIVE

We investigated the effects of prone position on respiratory dead space and gas exchange in 14 anaesthetized healthy patients undergoing elective posterior spinal surgery of more than 3 h of duration.

METHODS

The patients received a total intravenous anaesthetic with propofol/remifentanil/cisatracurium. They were ventilated at a tidal volume of 8-10 mL kg(-1), zero positive end-expiratory pressure and an inspired oxygen fraction of 0.4. Physiological, airway and alveolar dead spaces were calculated by analysis of the volumetric capnography waveform. Measurements were made in supine position (20 min after the beginning of mechanical ventilation) and 30, 120 and 180 min after turning to prone position.

RESULTS

We found that the alveolar dead space/tidal volume ratio did not change. PaO(2)/F(i)O(2) increased, although not statistically significantly. Dynamic compliance was reduced due to a reduction in tidal volume and an increase in plateau pressure.

CONCLUSIONS

Patients undergoing surgery in prone position for a duration of 3 h under general anaesthesia including muscle relaxation and mechanical ventilation without positive end-expiratory pressure have stable haemodynamics and no significant changes in the alveolar dead space to tidal volume ratio. Oxygenation tended to improve.