Effects of pulse-delivered inhaled nitric oxide administration on pulmonary perfusion and arterial oxygenation in dorsally recumbent isoflurane-anesthetized horses

Tamara L. Grubb Department of Animal Environment and Health, Swedish University of Agricultural Sciences, 53223 Skara, Sweden.
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164.

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Peter F. Lord Department of Clinical Sciences, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.

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Mieth Berger University Veterinary Hospital, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.

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Christina Larsson University Veterinary Hospital, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.

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Anneli Rydén Department of Clinical Sciences, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.

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Jan Frendin Department of Clinical Sciences, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.

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Pia Funkquist Department of Clinical Sciences, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.

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Anna Edner Department of Clinical Sciences, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.

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Görel Nyman Department of Animal Environment and Health, Swedish University of Agricultural Sciences, 53223 Skara, Sweden.

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Abstract

Objective—To image the spatial distribution of pulmonary blood flow by means of scintigraphy, evaluate ventilation-perfusion (VA/Q) matching and pulmonary blood shunting (Qs/Qt) by means of the multiple inert gas elimination technique (MIGET), and measure arterial oxygenation and plasma endothelin-1 concentrations before, during, and after pulse-delivered inhaled nitric oxide (PiNO) administration to isoflurane-anesthetized horses in dorsal recumbency.

Animals—3 healthy adult Standardbreds.

Procedures—Nitric oxide was pulsed into the inspired gases in dorsally recumbent isoflurane-anesthetized horses. Assessment of VA/Q matching, Qs/Qt, and Pao2 content was performed by use of the MIGET, and spatial distribution of pulmonary blood flow was measured by perfusion scintigraphy following IV injection of technetium Tc 99m–labeled macroaggregated human albumin before, during, and 30 minutes after cessation of PiNO administration.

Results—During PiNO administration, significant redistribution of blood flow from the dependent regions to the nondependent regions of the lungs was found and was reflected by improvements in VA/Q matching, decreases in Qs/Qt, and increases in Pao2 content, all of which reverted to baseline values at 30 minutes after PiNO administration.

Conclusions and Clinical Relevance—Administration of PiNO in anesthetized dorsally recumbent horses resulted in redistribution of pulmonary blood flow from dependent atelectatic lung regions to nondependent aerated lung regions. Because hypoxemia is commonly the result of atelectasis in anesthetized dorsally recumbent horses, the addition of nitric oxide to inhaled gases could be used clinically to alleviate hypoxemia in horses during anesthesia.

Abstract

Objective—To image the spatial distribution of pulmonary blood flow by means of scintigraphy, evaluate ventilation-perfusion (VA/Q) matching and pulmonary blood shunting (Qs/Qt) by means of the multiple inert gas elimination technique (MIGET), and measure arterial oxygenation and plasma endothelin-1 concentrations before, during, and after pulse-delivered inhaled nitric oxide (PiNO) administration to isoflurane-anesthetized horses in dorsal recumbency.

Animals—3 healthy adult Standardbreds.

Procedures—Nitric oxide was pulsed into the inspired gases in dorsally recumbent isoflurane-anesthetized horses. Assessment of VA/Q matching, Qs/Qt, and Pao2 content was performed by use of the MIGET, and spatial distribution of pulmonary blood flow was measured by perfusion scintigraphy following IV injection of technetium Tc 99m–labeled macroaggregated human albumin before, during, and 30 minutes after cessation of PiNO administration.

Results—During PiNO administration, significant redistribution of blood flow from the dependent regions to the nondependent regions of the lungs was found and was reflected by improvements in VA/Q matching, decreases in Qs/Qt, and increases in Pao2 content, all of which reverted to baseline values at 30 minutes after PiNO administration.

Conclusions and Clinical Relevance—Administration of PiNO in anesthetized dorsally recumbent horses resulted in redistribution of pulmonary blood flow from dependent atelectatic lung regions to nondependent aerated lung regions. Because hypoxemia is commonly the result of atelectasis in anesthetized dorsally recumbent horses, the addition of nitric oxide to inhaled gases could be used clinically to alleviate hypoxemia in horses during anesthesia.

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