Point-of-care ultrasound to assess volume status and pulmonary oedema in malaria patients

Purpose Fluid management is challenging in malaria patients given the risks associated with intravascular fluid depletion and iatrogenic fluid overload leading to pulmonary oedema. Given the limitations of the physical examination in guiding fluid therapy, we evaluated point-of-care ultrasound (POCUS) of the inferior vena cava (IVC) and lungs as a novel tool to assess volume status and detect early oedema in malaria patients. Methods To assess the correlation between IVC and lung ultrasound (LUS) indices and clinical signs of hypovolaemia and pulmonary oedema, respectively, concurrent clinical and sonographic examinations were performed in an observational study of 48 malaria patients and 62 healthy participants across age groups in Gabon. Results IVC collapsibility index (CI) ≥ 50% on enrolment reflecting intravascular fluid depletion was associated with an increased number of clinical signs of hypovolaemia in severe and uncomplicated malaria. With exception of dry mucous membranes, IVC-CI correlated with most clinical signs of hypovolaemia, most notably sunken eyes (r = 0.35, p = 0.0001) and prolonged capillary refill (r = 0.35, p = 0.001). IVC-to-aorta ratio ≤ 0.8 was not associated with any clinical signs of hypovolaemia on enrolment. Among malaria patients, a B-pattern on enrolment reflecting interstitial fluid was associated with dyspnoea (p = 0.0003), crepitations and SpO2 ≤ 94% (both p < 0.0001), but not tachypnoea (p = 0.069). Severe malaria patients had increased IVC-CI (p < 0.0001) and more B-patterns (p = 0.004) on enrolment relative to uncomplicated malaria and controls. Conclusion In malaria patients, POCUS of the IVC and lungs may improve the assessment of volume status and detect early oedema, which could help to manage fluids in these patients. Supplementary Information The online version contains supplementary material available at 10.1007/s15010-021-01637-2.


Ultrasound Protocol
3. Tap the 'Pre-sets' icon. Use the 'Cardiac' or 'Pediatric Cardiac' setting for most subjects. In larger adults, the 'Abdominal' pre-set may be used for increased depth.
4. Manually enter the subject ID number by tapping the 'Capture Reel' icon then selecting 'Associate a Patient'.
5. Place a reasonable amount of ultrasound gel onto the probe.
6. Orient the probe in the transverse plane with the probe marker pointing towards the subject's right side. Place the probe in the sub-xyphoid region in the subject's midline.
7. Use the liver as an acoustic window to identify the aorta. It should be visible as a circular structure on the right side of the screen just superior to the vertebral shadow (Figure 1a). Once the aorta is in view, tap 'Record' to capture a short video clip (5-10 seconds), then tap 'Stop' to save the video clip.
8. Once the video is saved, tap 'Freeze' to freeze the image. Remove the probe from the subject's abdomen.
9. Tap the 'Review' icon to scroll backwards through the frames. Select the frame that shows the aorta at its maximal width. Tap the 'Measurement Tools' icon then select 'Linear Measurement'. Use the touch screen callipers to measure the anterior-posterior (A-P) aorta diameter from inner wall to inner wall, then tap 'Capture' to save the image (Figure 1b).
10. Next, place the probe back on the subject's abdomen just below the subxiphoid process, this time orienting the probe in the longitudinal plane with the probe marker pointing towards the subject's head.
11. Using the liver as an acoustic window, locate the IVC as it leads into the right atrium. If the IVChepatic vein junction is not visible, gently fan the probe back and forth until it comes into view.
12. Tap the 'Modes' icon and select 'M-mode'. Use the touch screen marker to adjust the radial scan line so that it intersects the IVC approximately 2 cm distal to the IVC-hepatic vein junction. Freeze the image and remove the probe from the subject's abdomen (Figure 2a).
13. Use the 'Linear Measurement' tool to measure the maximal and minimal A-P IVC diameters from inner wall to inner wall. Select 'Capture' to save the image (Figure 2b).
14. The IVC collapsibility index will be calculated according to the following formula: ([max IVCmin IVC]/max IVC × 100%). The IVC-to-aorta ratio will be calculated by dividing the maximal A-P diameter of the IVC by the maximal A-P diameter of the aorta.   2. Each lung region will be scored based on four pre-defined aeration patterns of which the most abnormal score will be recorded; sub-pleural nodules and pleural effusions and will be separately noted (Table 1; Figure 3). Bilateral interstitial syndrome will be defined as having bilaterally ≥2 areas showing a B-pattern (either B1 or B2 pattern).
3. Image quality is documented as 'good' (pleural line, A-lines and/or findings clearly visible in all views), 'moderate' (pleural line, A-lines and/or findings clearly visible in most but not all views), or 'poor' (pleural line, A-lines and/or findings not clearly visible in most views).
5. At the end of the bedside ultrasound examination the gel will be wiped off the patient and the ultrasound probe will be cleaned. Presence of a sub-pleural, echo-poor, tissue-like area >0.5 cm with or without air bronchograms and causing disruption of the pleural line.

Sub-pleural nodule
Presence of a sub-pleural consolidation <0.5 cm causing disruption of the pleural line Pleural effusion Anechoic collection between the pleural line and chest wall