The effects of intrathoracic pressure during continuous two-lung ventilation for thoracoscopy on the cardiorespiratory parameters in sevoflurane anaesthetized dogs

Positive Intrapleural Pressure with Carbon Dioxide May Limit Intraoperative Pulmonary Arterial Bleeding: Verification by Animal Model

PURPOSE

Intraoperative complications, especially unexpected bleeding, are of great concern in the safety of thoracoscopic surgery. We investigated the hemostatic efficacy and safety of positive intrapleural pressure (PIP) with carbon dioxide insufflation by assessing the amount of blood loss in a pulmonary arterial hemorrhage model.

METHODS

An ex vivo experimental model of saline flow into a swine vessel was created in a container simulating a chest cavity. From the results, in vivo experiments (swine model) were conducted to compare the pulmonary arterial bleeding volume while applying PIP.

RESULTS

In the ex vivo experiment, regardless of the incision type, the outflow volumes did not significantly differ at flow pressures of 20, 30, and 40 mmHg. At each flow pressure, the outflow volumes at 10, 15, and 20 mmHg of positive pressure in the container were significantly smaller than those of the control (p = 0.027, p = 0.002, and p = 0.005, respectively). Similarly, the in vivo experiments showed that bleeding decreased as intrapleural pressure increased (slope = -0.22, F = 55.13, p <0.0001).

CONCLUSION

It may be possible to temporarily suppress pulmonary arterial bleeding by increasing the intrapleural pressure to 10 to 20 mmHg using carbon dioxide insufflation. This method may be an adjunctive hemostatic maneuver for intraoperative bleeding.

Evaluation of the effects of intraabdominal hypertension on equine central venous pressure

OBJECTIVE

To evaluate the effect of changes in intraabdominal pressure (IAP) on central venous pressure (CVP) in normal horses.

DESIGN

Experimental, in vivo study.

SETTING

University Teaching Hospital.

ANIMALS

Convenience sample of 7 mixed breed horses-5 geldings and 2 mares.

INTERVENTIONS

Pneumoperitoneum was induced in horses under standing sedation with carbon dioxide gas using a laparoscopic insufflator for a total of 60 minutes to simulate clinical elevation in IAP. Pressure was increased stepwise to 20 mm Hg over 30 minutes, and maintained at that pressure for 30 minutes to evaluate the effect of sustained intraabdominal hypertension. CVP was obtained from the cranial vena cava, concurrent with pressure obtained from the peritoneal cavity.

MEASUREMENTS AND MAIN RESULTS

CVP increased as IAP increased up to 12 mm Hg, and declined as IAP increased further. The changes in CVP over time were significantly different (P < 0.03). Repeated measures correlation was positive, and highest, for mean CVP as IAP increased from 0 to 12 mm Hg (r = .70; 95% CI, .43-.85; P < 0.0001). Correlation of mean CVP with insufflation pressure became negative as IAP increased further from 15 to 20 mm Hg (r = -.47; 95% CI, -.66 to -.21; P = 0.0006).

CONCLUSIONS

This report provides preliminary data demonstrating a biphasic trend in equine CVP caused by changes in IAP, similar to that observed in other species. Further investigations are needed to evaluate this trend and to confirm these results in clinical patients.

Evaluation of echocardiographic variables of morphometry and function in horses submitted to minimally invasive partial pericardiotomy

ABSTRACT This study aimed to evaluate the impact of minimally invasive partial pericardiotomy on echocardiographic variables of morphometry and function in healthy horses. Minimally invasive pericardiotomy was performed in six healthy horses. Echocardiographic evaluation was executed in different moments: prior to the surgical procedure (M0); 24 hours post procedure (M1); 72 hours post procedure (M2) and 28 days post procedure (M3). The following variables were measured: Right ventricular internal diameter in diastole and systole (RVd and RVs), interventricular septum thickness in diastole and systole (IVSd and IVSs), left ventricular internal diameter in diastole and systole (LVd and LVs), left ventricular free wall thickness in diastole and systole (LVFWd and LVFWs), aortic root diameter (Ao) and left atrial diameter (LA). From this data, the following variables were calculated: fractional shortening (FS%), fractional thickening of the interventricular septum (IVS%), fractional thickening of the left ventricular free wall (LVFW%) and the relationship between left atrial and aortic diameters (LA/Ao). After 28 days, a new thoracoscopy was performed for inspection of the thoracic cavity. In M1 and M2 ECO evaluations, a statistically significant change in LVFW and a decrease in RVd, LVd, LVFWs, LA, LVs, FS% and IVS was documented. Pericardiotomy is a promising technique in horses, with minor postoperative complication. The variations in the echocardiographic parameters were transient and did not cause hemodynamic damage to the animals.

Is two lung ventilation with artificial pneumothorax a better choice than one lung ventilation in minimally invasive esophagectomy?

Two lung ventilation (TLV) with artificial pneumothorax has been introduced into MIE for several years. A few researches have reported its clinical application, and proved its safety and feasibility. However, it is still controversial whether TLV with artificial pneumothorax is a better choice than one lung ventilation (OLV). Obviously, single lumen endotracheal tube is easy for intubation and intraoperative maintenance. Potential problems during intervention include hemodynamic changes, oxygenation, and air embolism. In this paper, present literature is reviewed about two and one lung ventilation in thoracoscopy, looking for clear conclusions for future application.

CO2 during single incisional thoracoscopic bleb resection with two-lung ventilation

Background

CO₂ insufflation could provide a better surgical field during single-incision thoracoscopic surgery (SITS) with small tidal two-lung ventilation (ST-TLV). Here we compared the surgical field and physiological effects of ST-TLV with and without CO₂ during SITS.

Methods

Patients underwent scheduled SITS bullectomy. Surgery under ST-TLV general anesthesia performed without CO₂ (group NC) or with CO₂ insufflation (group C). The surgical field was graded at thoracoscope introduction and at bulla resection as follows: good (more than half of the 1st rib visible; bleb easily grasped with the stapler), fair (less than half of the 1st rib visible; some manipulation needed to grasp the bleb with the stapler), or poor (1st rib non-visible; bleb ungraspable). Vital signs, arterial blood gas analysis (ABGA), and mechanical ventilation parameters, postoperative chest tube indwelling duration, length of hospital stays, and complications were recorded.

Results

A total of 80 patients were ultimately included. The surgical field at thoracoscope introduction was better in group C (P=0.022). However, at bleb resection, the surgical fields did not differ (P=0.172). The operation time was significantly longer in group C (P=0.019) and anesthesia recovery time was not different (P=0.369). During the CO₂ insufflation, the airway pressure was higher in group C (P=0.009). Mean PaCO₂ was significantly higher (P=0.012) and mean PaO₂ was significantly lower (P=0.024) in group C, but both values were within the physiologically normal range. Postoperative chest tube indwelling duration and length of hospital stays were not statistically different (P=0.234 and 0.085 respectively). Postoperative complication frequencies were similar (12.5% for group NC, 10.0% for group C, P=0.723).

Conclusions

SITS with CO₂ insufflation during ST-TLV did not produce a superior surgical field except at the beginning of surgery. CO₂ insufflation required more time and resulted in higher mean PaCO₂ and peak airway pressure.

Current concepts in minimally invasive surgery of the thorax

Thoracoscopy is a technique that has been shown to decrease patient morbidity and is rapidly becoming more diversely applied for diagnostic and therapeutic interventions in veterinary medicine. This article describes the basic equipment and application of thoracoscopy in small animal surgery. The diagnostic and therapeutic applications are introduced and briefly described.

Cardiac preload: hemodynamic physiology during thoracic surgery

PURPOSE OF REVIEW

Operations in pleural cavity have circulatory effects both in pulmonary and systemic circulations. Nevertheless studies of these effects have yielded conflicting results. The importance of good understanding of hemodynamic changes during the operation in pleural cavity consists in fact that they are one of the factors influencing postoperative course of operated patients.

RECENT FINDINGS

Dominating changes in the hemodynamics are represented by an increase of the cardiac output after opening the pleura. Changes in the arterial pressure are clinically unimportant and decreased cardiac output cannot be explained by preload as the preload is almost constant during the whole operation procedure. Arterial pressures in the pulmonary circulation are also increased after opening of pleura but only in the hip position so it depends on the body position rather than on the operation itself.

SUMMARY

As far as it is known, circulatory and ventilatory consequences of thoracotomy are influenced particularly by the position of the patient's body on the operation table. During operation performed on the lung hemodynamics are influenced particularly by the individual steps of the operation procedure and by the position of the body. The hemodynamics are also influenced by metabolic functions of lungs particularly by the increased turnover of catecholamines in the lungs (increased total peripheral resistance and arterial pressures).

Cardiopulmonary effects of thoracoscopy in anesthetized normal dogs

OBJECTIVE

To evaluate the effect of an open-chest condition on oxygen delivery in anesthetized dogs.

STUDY DESIGN

Prospective, controlled experimental study.

ANIMALS

Eight clinically normal adult Walker Hound dogs weighing 25.6-29.2 kg.

METHODS

Eight anesthetized dogs underwent an open-chest operation after the insertion of thoracoscopy cannulae in the lateral chest walls. A Swan Ganz catheter was used to both measure hemodynamic parameters and obtain mixed venous blood samples for blood gas analysis. A dorsal pedal catheter was placed to both measure arterial blood pressure and obtain blood samples for blood gas analysis. Oxygen delivery index and oxygen extraction ratio were calculated. A randomized block anova for repeated measures was used to evaluate the effect of the treatment on hemodynamic and pulmonary parameters.

RESULTS

Creation of an open chest did not significantly affect oxygen delivery index (DO(2)I; p = 0.545). It induced a significant decrease in arterial oxygen partial pressure (PaO(2); p = 0.018) and arterial oxygen content (CaO(2); p = 0.025). It induced a significant increase in shunt fraction (p = 0.023), physiologic dead space (p = 0.015), and alveolar-arterial oxygen difference (p = 0.019). Arterial partial pressure of carbon dioxide (PaCO(2); p = 0.766) and arterial hemoglobin oxygen saturation (SaO(2); p = 0.178) were not significantly affected. Diastolic (DPAP; p = 0.050) and mean (MPAP; p = 0.033) pulmonary arterial pressures were significantly increased by opening the chest. Other hemodynamic parameters were not significantly affected.

CONCLUSIONS

Opening the thoracic cavity is not detrimental to hemodynamic function and oxygen delivery in normal dogs, although impaired gas exchange does occur.

CLINICAL RELEVANCE

Close monitoring of patients is recommended during open-chest thoracoscopy as adverse effects on gas exchange can contribute to hypoxemia.