Perioperative lung ultrasonography in healthy horses undergoing general anesthesia for elective surgery

Abstract

Background: Lung ultrasound (LUS) is poorly evaluated in horses, especially perioperatively.

Objectives: (1) Describe LUS findings in healthy horses before and after general anesthesia (GA), (2) evaluate if GA induces ultrasonographic changes in healthy horses, (3) suggest a LUS scoring system, (4) identify horse variables that are associated to LUS changes after anesthesia.

Animals: Twenty-five healthy adult horses undergoing elective surgery.

Methods: Prospective hypothesis-driven observational study. LUS findings were recorded before anesthesia, 5 minutes in recovery, 15 minutes, 2H, 3H, 4H, 6H, and 24H after anesthesia in 8 lung regions. Clinical data were collected perioperatively.

Results: There was a significant increase in amount of I-lines (10.8 ± 8.7 vs 15.28 ± 8.19), B-lines (3.2 ± 3.5 vs 8.72 ± 4.86), and coalescent B-lines (0.04 ± 0.2 vs 1.12 ± 1.45) after anesthesia compared to before anesthesia, and a significantly higher LUS score 2H after anesthesia (4.92 ± 8.40) compared to before anesthesia (0.9 ± 1.8; P = .02). The maximal LUS score after anesthesia was correlated to total procedure time (Pearson r = 0.4, P = .05; Spearman r = 0.44, P = .03) and was significantly higher in horses with abnormal cardiorespiratory values during anesthesia (P = .005).

Conclusions: LUS changes can be induced by GA in healthy horses. This study did not investigate if and which LUS findings indicate lesions, however, this information can aid clinicians to identify pulmonary complications after anesthesia.

Keywords: atelectasis; equine; postoperative; pulmonary; ultrasound.

FIGURE 1

Lung ultrasound regions. Location of the ultrasound regions used for the study

FIGURE 2

Lung ultrasound findings. The thorax was scanned with the transducer placed in the intercostal spaces parallel to the ribs and orientated as such that the right side of the ultrasound image corresponded with dorsal and the left side with ventral. (A) Three small lung comets visible in the left caudoventral region of the lung of Case 11, 2 hours after standing. (B) Image of a single B‐line in the left caudoventral region of the lung of Case 3, 2 hours after standing with the linear transducer. (C) Image of a single B‐line visible with the convex transducer in the cranioventral region of the lung of Case 3, 2 hours after standing. (D) Lung rockets in the left caudodorsal region of the lung of Case 10, 1 hour after standing. On the left of the image, horizontal A‐lines, which are normal ultrasonographic artifacts are evident. On the right of the image, the normal A‐lines are interrupted by lung rockets. (E) Lung rockets visible with the convex transducer in the right cranioventral region of the lung of Case 3, 2 hours after standing. (F) Coalescent B‐lines in the cranioventral region of the right lung of Case 5, 2 hours after standing. B‐lines were considered coalescent if their width was above 9 mm. (G) Small area of lung consolidation with visible shred or sub B‐lines in Case 10, 15 minutes after standing with the linear transducer. (H) Image of an I‐line on the right and 1 small lung comet in the center of the image recorded from the left caudoventral region of the lung of Case 11, 2 hours after standing. (I) Presence of irregular pleura in the caudodorsal region of left lung in Case 24 during recovery. (J) Presence of pleural effusion in the right caudoventral region of Case 25, 2 hours after standing. Note the presence of the caudoventral mediastinal reflection on the right of the image

FIGURE 3

Lung ultrasound (LUS) findings before and after anesthesia of 25 healthy horses undergoing elective surgery, illustrated per thoracic region over the different time points. Legend: LCAD, left caudodorsal region; LCAV, left caudoventral region; LCRD, left craniodorsal region; LCRV, left cranioventral region; RCAD, right caudodorsal region; RCAV, right caudoventral region; RCRD, right craniodorsal region; RCRV, right cranioventral region; Time 0, before anesthesia; 1, 5 minutes in the recovery; 2, 15 minutes after standing; 3, 2 hours after anesthesia; 4, 3 hours after anesthesia; 5, 4 hours after anesthesia; 6, 6 hours after anesthesia; 7, 24 hours after anesthesia

FIGURE 4

Evolution of the lung ultrasound (LUS) score for the entire thorax over time in 25 healthy horses undergoing elective surgery. *Statistically different (P < .05)