Cardiopulmonary Effects of Intrathoracic Insufflation in Dogs

Abstract

This study was designed to quantify the effects of incremental positive insufflation of the intrathoracic space on cardiac output (CO), heart rate (HR), arterial pressure (AP), central venous pressure (CVP), and percent saturation of hemoglobin with oxygen (SPO2) in anesthetized dogs. Seven healthy, adult dogs from terminal teaching laboratories were maintained under anesthesia with isoflurane delivered with a mechanical ventilator. The experimental variables were recorded before introduction of an intrathoracic catheter, at intrathoracic pressures (IP) of 0 mm Hg, 3 mm Hg insufflation, and additional increments of 1 mm Hg insufflation thereafter until the SPO2 remained<85% despite increases in minute volume. Finally the variables were measured again at 0 mm Hg IP. The cardiac output and systolic and diastolic AP significantly (P < 0.05) decreased at 3 mm Hg IP. Significant decreases in SPO2 were seen at 10 mm Hg IP. Significant increase in CVP was noted at 6 mm Hg IP. Heart rate decreased significantly at 5 to 6 mm Hg IP but was not decreased above 6 mm Hg IP. Given the degree of CO decrease at low intrathoracic pressures, insufflation-aided thoracoscopy should be used with caution and at the lowest possible insufflation pressure. Standard anesthetic monitoring variables such as HR and AP measurements may not accurately reflect the animal's cardiovascular status.

Effect of One‐Lung Ventilation With or Without Low‐Pressure Carbon Dioxide Insufflation on Cardiorespiratory Variables in Cats Undergoing Thoracoscopy

“…These latter increases may have been because of sympathetic stimulation associated with decreased ventilation in 2 cats and a light plane of anesthesia. Central venous pressure and PAP were significantly higher compared to baseline at most time points probably because of the direct effect of the elevated intrathoracic pressure on central veins, a phenomenon also seen in canine and porcine models …”

“…Thoracic CDI has been reported rarely in the veterinary literature perhaps because of the documented evidence that it causes significant cardiorespiratory compromise even at relatively low intrathoracic pressures . This is related to collapse of thin‐walled low‐pressure vascular compartments within the thorax (right atrium, caudal and cranial vena cava) under the effects of the insufflation pressure which limits cardiac preload . In conjunction with this, pulmonary resistance increases, which further decreases CI and SV .…”

“…In an experimental porcine study, at intrathoracic pressures >5 mmHg, significantly decreased CI, MABP, and SV occurred with very profound decreases (an 81% decrease in CI) seen at 15 mmHg . The recommendation from these reports was that thoracic insufflation should be used with great caution in thoracoscopic surgery . In people, OLV is considered the modality of choice for most advanced thoracoscopic interventions as it is in veterinary medicine.…”

Video‐Assisted Thoracoscopic Resection of a Noninvasive Thymoma in a Cat with Myasthenia Gravis Using Low‐Pressure Carbon Dioxide Insufflation

“…OLV is possible in cats but technical challenges are encountered related to the small diameter of the feline large airways and the difficulty in establishing bronchoscopic visualization for positioning of specialized endotracheal tubes or blockers . Carbon dioxide insufflation has been used sparingly in dogs due to detrimental effects on cardiac output secondary to compression of low‐pressure vascular spaces within the thorax, even at very low intrathoracic pressures . The cardiopulmonary effects of low‐pressure carbon dioxide insufflation in cats have been investigated in conjunction with OLV but not in isolation .…”

Laparoscopic correction of experimentally induced diaphragmatic rupture in dogs

“…It has been demonstrated that thoracic insufflation with carbon dioxide with or without associated abdominal insufflation causes cardiopulmonary effects such as decrease in oxygen saturation, arterial blood pressure and cardiac output, and increases in peak inspiratory and central venous pressure 22,23 . One study that mentions insufflation pressure for correction of diafragmatic rupture in clinical conditions used 10 mmHg.…”