Electrical impedance tomography: changes in distribution of pulmonary ventilation during laparoscopic surgery in a porcine model

BACKGROUND

Because of the creation of a pneumoperitoneum, impairment of ventilation is a common side-effect during laparoscopic surgery. Electrical impedance tomography (EIT) is a method with the potential for becoming a tool to quantify these alterations during surgery. We have studied the change of regional ventilation during and after laparoscopic surgery with EIT and compared the diagnostic findings with computed tomography (CT) scans in a porcine study.

MATERIALS AND METHODS

After approval by the local animal ethics committee, six pigs were included in the study. Two laparoscopic operations were performed [colon resection (n=3) and fundoplicatio (n=3)]. The EIT measurements (6th parasternal intercostal space) were continuously recorded by an EIT prototype (EIT Evaluation Kit, Dräger Medical, Lübeck, Germany). To verify ventilatory alterations detected by EIT, a CT scan was performed postoperatively.

RESULTS

Ventilation with defined tidal volumes was significantly correlated to EIT measurements (r2=0.99). After creation of the pneumoperitoneum, lung compliance typically decreased, which agreed well with an alteration of the distribution of pulmonary ventilation measured by EIT. Elevation of positive end-inspiratory pressure reopened non-aerated lung areas and showed a recovery of the regional ventilation measured by EIT. Additionally, we could detect pulmonary complications by EIT monitoring as verified by CT scans postoperatively.

CONCLUSION

EIT monitoring can be used as a continuous non-invasive intraoperative monitor of ventilation to detect regional changes of ventilation and pulmonary complications during laparoscopic surgery. These EIT findings indicate that surgeons and anesthetists may eventually be able to optimize ventilation directly in the operating theatre.

Post-dural puncture headache in young adults: comparison of two small-gauge spinal catheters with different needle design

BACKGROUND

To reduce the risk of post-dural puncture headache (PDPH) in continuous spinal anaesthesia, small-gauge spinal catheter systems with different techniques of dural perforation have been developed.

METHODS

Two systems, the catheter through-needle technique (MicroCatheter, Portex, UK) and the catheter over-needle technique (22G Spinocath, B. Braun, Germany), were used in 18 young healthy volunteers (age 18-30 yr), who were enrolled in a neuroendocrinological investigation for analysis of neuropeptides in cerebrospinal fluid (CSF). After intermittent sampling of CSF (17 x 0.5 ml over 4 h), the catheter was removed and the development of PDPH and pain intensity were documented prospectively by the subjects in a standardized headache assessment (11-point numerical rating scale [NRS]).

RESULTS

The study revealed a high overall incidence of PDPH (78%) with no significant differences between groups (P=0.26). However, the over-needle group showed a significantly shorter duration of PDPH (2.4 [SD 2.3] vs 5.1 [3.1] days, P=0.050) and lower maximum pain intensity (3.1 [2.9] vs 7.3 [3.4] NRS, P=0.014) than the through-needle group.

CONCLUSIONS

The results demonstrate a potential benefit of the catheter over-needle technique for the reduction of the duration and intensity of PDPH.