Arterial oxygenation and one-lung anesthesia

Nonintubated Video-Assisted Thoracic Surgery for the Management of Primary and Secondary Spontaneous Pneumothorax

Nonintubated video-assisted thoracoscopic surgery for the treatment of primary and secondary pneumothorax was first reported in 1997 by Nezu. However, studies on this technique are few. Research in the past 20 years has focused on the perioperative outcomes, including the surgical duration, length of hospital stay, and postoperative morbidity and respiratory complication rates, which appear to be better than those of surgery under intubated general anesthesia. This study provides information pertaining to the physiologic, surgical, and anesthetic aspects and describes the potential benefits of nonintubated thoracoscopic surgery for the management of primary and secondary spontaneous pneumothorax.

[Anesthesia, ventilation and pain treatment in thoracic trauma]

The management of anesthesia plays a central role in the treatment of thoracic trauma, both in the initial phase when safeguarding the difficult airway and in the intensive care unit. A rapid transfer to a trauma center should be considered in order to recognize and treat organ dysfunction in time. Development of atelectasis, pneumonia and acute lung failure are common pulmonary complications. Non-invasive ventilation combined with physiotherapy and respiratory training can help to minimize these pulmonary complications. If single lung ventilation is necessary as part of the operative patient care, a double-lumen tube, a bronchial blocker and the Univent®-Tubus (Fuji Systems Corporation, Tokyo, Japan) can be used. Special attention should be paid to the hypoxic pulmonary vasoconstriction that occurs in this maneuver. Pain therapy is ideally carried out patient-adapted with epidural anesthesia. In addition, intraoperatively inserted catheters in the sense of a continuous intercostal block or serratus plane block are good alternatives. The aim of these therapies should be early mobilization and transfer of the patient to rehabilitation.

Evolution of regional oxygen saturation in the peri-operative of thoracic surgery and its relationship with central venous saturation

OBJECTIVE

To study the relationship between the values of SvcO2 and SrcO2 in lung resection with one lung ventilation (OLV) and changes in these variables and mean arterial pressure (MAP) and arterial oxygen saturation (SpO2) during the perioperative period.

MATERIAL AND METHODS

Prospective, observational study of 25 patients in whom pulmonary resection was performed with OLV. The values of MAP, SpO2, SvO2, and SrcO2 were recorded at 6 different times: 1)baseline; 2)double-lung ventilation before the OLV (VBP1); 3)during OLV; 4)after double-lung ventilation (VBP2); 5)30minutes after surgery, and 6)6hours after surgery.

RESULTS

The SrcO2 showed a significant increase from baseline to starting ventilation (65.72±9.05% vs 70.44±7.24%; P<.01). There were no significant changes in their values at the different intraoperative times. Post-operatively, as in the case of the SvcO2, a significant decrease (P<.001) of its value compared with the previous value was observed.

CONCLUSIONS

SrcO2 showed a significant increase after induction of anaesthesia and initiation of mechanical ventilation compared to baseline, and a significant decrease at the end of surgery after extubation in the immediate postoperative period. Being a tissue monitoring, non-invasive technique and with continuous values it can alert the clinician of changes in the ratio of oxygen consumption (VO2) to oxygen delivery (DO2) at times of greatest risk, such as OLV, extubation, and the early postoperative period.

Comparison of Minimally and More Invasive Methods of Determining Mixed Venous Oxygen Saturation

OBJECTIVE

To investigate the accuracy of a minimally invasive, 2-step, lookup method for determining mixed venous oxygen saturation compared with conventional techniques.

DESIGN

Single-center, prospective, nonrandomized, pilot study.

SETTING

Tertiary care hospital, university setting.

PARTICIPANTS

Thirteen elective cardiac and vascular surgery patients.

INTERVENTIONS

All participants received intra-arterial and pulmonary artery catheters. Minimally invasive oxygen consumption and cardiac output were measured using a metabolic module and lithium-calibrated arterial waveform analysis (LiDCO; LiDCO, London), respectively. For the minimally invasive method, Step 1 involved these minimally invasive measurements, and arterial oxygen content was entered into the Fick equation to calculate mixed venous oxygen content. Step 2 used an oxyhemoglobin curve spreadsheet to look up mixed venous oxygen saturation from the calculated mixed venous oxygen content. The conventional "invasive" technique used pulmonary artery intermittent thermodilution cardiac output, direct sampling of mixed venous and arterial blood, and the "reverse-Fick" method of calculating oxygen consumption.

MEASUREMENTS AND MAIN RESULTS

LiDCO overestimated thermodilution cardiac output by 26%. Pulmonary artery catheter-derived oxygen consumption underestimated metabolic module measurements by 27%. Mixed venous oxygen saturation differed between techniques; the calculated values underestimated the direct measurements by between 12% to 26.3%, this difference being statistically significant.

CONCLUSION

The magnitude of the differences between the minimally invasive and invasive techniques was too great for the former to act as a surrogate of the latter and could adversely affect clinical decision making.

Effects on respiration of nonintubated anesthesia in thoracoscopic surgery under spontaneous ventilation

Thoracoscopic surgery without tracheal intubation [nonintubated video-assisted thoracoscopic surgery (VATS)] is an emerging treatment modality for a wide variety of thoracic procedures. By surgically induced open pneumothorax, the operated lung collapse progressively while the dependent lung is responsible for sufficiency of respiratory function, including oxygenation and ventilation. Encouraging results showed that ventilatory changes and oxygenation could be adequately maintained in major lung resection surgery and in patients with impaired respiratory function. In spite of a relative hypoventilation, mild hypercapnia is inevitable but clinically well tolerated. An understanding the respiratory physiology during surgical pneumothorax, either in awake or sedative status, and an established protocol for conversion into tracheal intubation are essential for patient safety during nonintubated VATS.

Effects of a 1:1 inspiratory to expiratory ratio on respiratory mechanics and oxygenation during one-lung ventilation in the lateral decubitus position

Prolonged inspiratory to expiratory (I:E) ratio ventilation may have both positive and negative effects on respiratory mechanics and oxygenation during one-lung ventilation (OLV), but definitive information is currently lacking. We therefore compared the effects of volume-controlled ventilation with I:E ratios of 1:1 and 1:2 on respiratory mechanics and oxygenation during OLV. Fifty-six patients undergoing thoracoscopic lobectomy were randomly assigned volume-controlled ventilation with an I:E ratio of 1:1 (group 1:1, n=28) or 1:2 (group 1:2, n=28) during OLV. Arterial and central venous blood gas analyses and respiratory variables were recorded 15 minutes into two-lung ventilation, at 30 and 60 minutes during OLV, and 15 minutes after two-lung ventilation was re-initiated. Peak and plateau airway pressures in cmH2O [standard deviation] during OLV were significantly lower in group 1:1 than in group 1:2 (P <0.01) (19 [3] and 23 [4]; 16 [3] and 19 [5], respectively). The arterial to end-tidal carbon dioxide tension difference was significantly lower in group 1:1 than in group 1:2 (P <0.01), (0.5 [0.3] and 1.1 [0.5]). There were no significant differences in PaO2 during OLV between the two groups (OLV30, P=0.856; OLV60, P=0.473). In summary, volume-controlled ventilation with an I:E ratio of 1:1 reduced peak and plateau airway pressures improved dynamic compliance and efficiency of alveolar ventilation, but it did not improve arterial oxygenation in a substantial manner. Furthermore, the associated increase in mean airway pressure might have reduced cardiac output, resulting in a lower central venous oxygen saturation.

Anesthesia management of totally endoscopic atrial septal defect repair with a robotic surgical system

STUDY OBJECTIVE

To investigate anesthetic techniques for robot-assisted endoscopic atrial septal defect (ASD) repair.

DESIGN

Clinical observational study.

SETTING

Operating room of a general military hospital.

PATIENTS

56 adult, ASA physical status 1 and 2 patients undergoing elective general anesthesia.

INTERVENTIONS

After induction of general anesthesia, a left-sided, double-lumen endotracheal tube was positioned to allow single left-lung ventilation and contralateral CO(2) pneumothorax (capnothorax). With ultrasound guidance, peripheral cardiopulmonary bypass (CPB) catheters were placed.

MEASUREMENTS AND MAIN RESULTS

All patients tolerated single left-lung ventilation before CPB; however, hypoxia (oxygen saturation < 90%) occurred in 11 (19.6%) patients post-CPB, which required treatment with continuous positive airway pressure. Fifteen (26.8%) patients had hypotension secondary to capnothorax, which was treated with transfusion and vasopressors. Aortic cross-clamp time was 43.6 ± 11.2 minutes, and CPB time was 106.7 ± 12.4 minutes. The median intensive care unit stay was 21 hours and postoperative hospital stay was 4 to 7 days.

CONCLUSIONS

The key issue for anesthetic management of robot-assisted totally endoscopic ASD repair is maintaining stable hemodynamics and oxygenation, especially during one-lung ventilation and capnothorax.

[Hemodynamic monitoring in one-lung ventilation]

One-lung ventilation causes adverse effects in pulmonary gas exchange and cardiocirculatory function. These adverse effects become particularly important for patients with underlying cardiopulmonary comorbidities. Alterations in pulmonary gas exchange have been investigated in several experimental and clinical trials. However, the hemodynamic consequences of one-lung ventilation are to a great extent unknown. Furthermore, no conclusive recommendations exist as to which kind of hemodynamic monitoring should be preferred in the situation of one-lung ventilation. Many issues regarding hemodynamic monitoring in one-lung ventilation remain unacknowledged. This article will review the current literature on hemodynamic monitoring in one-lung ventilation in order to derive recommendations for the application of hemodynamic monitoring in this specific peri-operative situation.

Update on one-lung ventilation: the use of continuous positive airway pressure ventilation and positive end-expiratory pressure ventilation--clinical application

PURPOSE OF REVIEW

The purpose of this review is to examine the evidence for and the clinical use of continuous positive airway pressure (CPAP) and positive end-expiratory pressure (PEEP) for the management of one-lung ventilation during thoracic surgery. CPAP and PEEP use are important as we are increasingly challenged with patients with less respiratory reserve and greater comorbidity leading to the need for greater clinical management and more interventions during one-lung ventilation for thoracic surgery to prevent perioperative complications.

RECENT FINDINGS

The focus of this article is on the most recent literature with selected classic articles. First, the supportive literature and rationale for application of PEEP, CPAP or both during thoracic surgery are reviewed, relative to the threats of hypoxemia, hyperoxia and mechanical lung injury. The second part of the article focuses on the clinical use of PEEP and CPAP. Algorithms for the application of CPAP and PEEP to patients both at risk and not at risk of acute lung injury are presented.

SUMMARY

CPAP and PEEP are useful not only to treat hypoxia and atelectasis as the consequence of one-lung ventilation, perhaps more importantly, also as part of a protective lung-ventilation strategy to ameliorate mechanical stress and prevent acute lung injury.