Bedside hand vein inspection for noninvasive central venous pressure assessment

Accepted Manuscript Bedside hand vein inspection for noninvasive central venous pressure assessment

Franziska Vogel, Daniel Staub, Markus Aschwanden, Martin Siegemund, Stephan Imfeld, Gianmarco Balestra, Hak Hong Keo, Heiko Uthoff PII: DOI: Reference:

S0735-6757(19)30269-4 https://doi.org/10.1016/j.ajem.2019.04.044 YAJEM 58207

To appear in:

American Journal of Emergency Medicine

Received date: Revised date: Accepted date:

23 January 2019 8 April 2019 25 April 2019

Please cite this article as: F. Vogel, D. Staub, M. Aschwanden, et al., Bedside hand vein inspection for noninvasive central venous pressure assessment, American Journal of Emergency Medicine, https://doi.org/10.1016/j.ajem.2019.04.044

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ACCEPTED MANUSCRIPT Bedside hand vein inspection for noninvasive central venous pressure assessment

Franziska Vogel¹, Daniel Staub¹, Markus Aschwanden¹, Martin Siegemund2, Stephan Imfeld1,

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Gianmarco Balestra2, Hak Hong Keo1, 4, Heiko Uthoff¹,3

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Affiliations

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¹Department of Angiology, University Hospital Basel, Basel, Switzerland 2

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Intensive Care Unit, University Hospital Basel, Basel, Switzerland

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Gefässpraxis am See – Lakeside Vascular Center, Clinic St. Anna, Lucerne, Switzerland

Vascular Institute Central Switzerland, Aarau, Switzerland

Corresponding author

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Word Count

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E-mail: [email protected] (HU)

Abstract: 314

Total document: 3575

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ACCEPTED MANUSCRIPT Abstract Rapid estimates of the central venous pressure (CVP) can be helpful to administer early fluid therapy or to manage cardiac preload in intensive care units, operating rooms or emergency rooms in order to start and monitor an adequate medical therapy. Invasive CVP measurements have inherent and non-negligible complication rates as well as great

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expenditures. Several noninvasive methods of CVP measurements, like ultrasound-guided techniques, are available, but require trained skills and special equipment which might not be

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at hand in all situations.

Our purpose was to evaluate the feasibility and accuracy of CVP estimates assessed upon

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the height of hand veins collapse (HVC) using invasively measured CVP as the gold standard.

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The HVC was determined by slowly lifting the patient’s hand while watching the dorsal hand veins to collapse. The vertical distance from the dorsal hand to a transducer air zero port was

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noted and converted to mmHg. The observer was blinded to the simultaneously measured

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CVP values, which were categorized as low (<7 mmHg), normal (7-12 mmHg) and high (>12 mmHg).

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Measurements were performed in 82 patients who had a median [IQR] age of 67 [60;74]. Median CVP was 12 [8;15] mmHg and the median absolute difference between the

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measured HVC and CVP was 4 [2;7] mmHg. The Spearman correlation coefficient between CVP and HVC was 0.55, 95 %-CI [0.35;0.69]. Overall CVP categorization was correct in 45 % of the cases. HVC had a sensitivity of 92 % for a low CVP with a negative predictive value of 98 %. A high HVC had a sensitivity of 29 % but a high specificity of 94 % for a high CVP. The overall performance of observing the hand vein collapse to estimate CVP was only moderate in the intensive care setting. However, the median difference to the CVP was low and HVC identifies a low CVP with a high sensitivity and excellent negative predictive value.

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ACCEPTED MANUSCRIPT Introduction The assessment of the volume status is an important component in evaluating a patient`s condition and in providing appropriate care. Therefore, rapid estimates of the central venous pressure can be helpful to administer early fluid therapy or to manage cardiac preload in

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intensive care units, operating rooms or emergency rooms [1-3]. Several methods assessing the central venous pressure noninvasively, including

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compression ultrasound, internal jugular vein collapsibility, and inferior vena cava

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collapsibility have been tested and been rated differently in reliability and accuracy [4-8]. Nevertheless all of these methods require ultrasound equipment and related expertise of the

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examiners. Even though these methods are more rapidly performed than placing a central venous catheter, ultrasound equipment as well as skilled performers may not be available at

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all times in operating rooms, wards, emergency departments. Therefore, an easily applicable bedside method to estimate central venous pressure not depending on technical equipment,

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structural requirements or specialists’ availability would be very helpful especially in

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outpatient clinics and austere environments where such resources are seldom routinely available. Theoretically, by lifting the patient`s hand above heart level, the point of peripheral

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vein collapse indicates the corresponding central venous pressure. The aim of this study is to prospectively evaluate the feasibility and accuracy of the hand vein

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collapse (HVC) examination to estimate the central venous pressure using the current gold standard invasively measured central venous pressure (CVP) as reference.

Methods Study design and setting This study was performed at the surgical and medical intensive care units (ICU) of the University Hospital of Basel, a tertiary care teaching hospital. Enrollment to this single-center 3

ACCEPTED MANUSCRIPT prospective observational study took place at the ICU because of the high prevalence of central vein catheters. Furthermore, a completely air conditioned ICU could provide identical surrounding conditions like room temperature and humidity. The inclusion criteria were age > 18 years, preexisting central venous access with established invasive hemodynamic monitoring, at least one hand without venous or arterial access catheters or blood pressure

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cuffs and written informed consent. If the patient was unable to give informed consent (e.g. mechanically ventilated patients), the physician in charge attested to the safety of the

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investigation for the patient and gave informed consent by proxy. Because of the non-

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invasiveness of the study measurements and in accordance with the ethics committee no subsequent consent from the patient (e.g. after successful ventilator weaning) was obtained.

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Patients were ineligible if they had a known upper extremity deep vein thrombosis. The local ethics committee had approved the study and the trial was registered at ClinicalTrials.gov

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(NCT01079611).

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Invasive CVP measurement (CVP)

The minimum, maximum and mean CVP were measured electronically via an 18G central

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venous catheter by a custom monitoring kit (Hospira Inc., Lake Forest, IL, USA) including a Transpac IT transducer. The CVP was obtained simultaneously to the clinical evaluation of

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hand vein collapse by an independent physician who was blinded to the HVC measurements. The cardiovascular monitor measures CVP with a precision of 3% (product information; Agilent Technologies, Andover, Massachusetts).

Clinical evaluation of hand vein collapse (HVC) The examination was performed in a supine position, with the patient’s arm lowered below body level to ensure filling of the hand veins. By slowly lifting the patient’s hand the examiner watched carefully the best visible vein on the hand`s dorsum and gently palpated the veins to 4

ACCEPTED MANUSCRIPT notice at which height it was collapsing. Then the height of the vein in relation to the transducer air zero port which was adjusted to the phlebostatic axis (point where the fourth intercostal space and mid-axillary line cross each other = right atrium level) beforehand was measured (Fig 1). As demonstrated previously {Thalhammer, 2007, Noninvasive central venous pressure measurement by controlled compression sonography at the forearm.} the

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height of the hand vein (cm) correlates well to the corresponding hand vein pressure in cmH2O (r=0.95, p<0.001), i.e. lowering the hand 10cm below heart level reduces the hand

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vein pressure by 10cmH2O. Accordingly the height measures(cm) were converted into the

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unit mmHg (1 cm ≈ 1cm H2O 0.73 mmHg).

After measurement the examiner was asked to estimate the HVC as low (< 7 mmHg), normal

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(7-12 mmHg), and high (> 12 mmHg), based on his clinical experience, as well as to rate the

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examination quality subjectively as good, moderate, or poor. Classification in low, normal,

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and high was used as predefined elsewhere [5].

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Fig 1 Set-up site of HVC evaluation at intensive care unit. Transducer air zero port was set at heart height. The level rod indexes height of vein collaps which was investigated by lifting the

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patient`s hand and observing the dorsum`s veins.

Study procedure

After obtaining written informed consent, demographic and clinical parameters were recorded on a dedicated data sheet by an independent investigator. Subsequently, HVC measurements were performed by one of two experienced vascular specialists (>5 years of clinical experience) in a random sequence according to their availability. CVP values were simultaneously recorded during the measurement to account for potential hemodynamic changes. The examiner was blinded to the CVP. All data, including the time needed for each measurement (starting with the first grip of the patient`s hand and ending with the report of 5

ACCEPTED MANUSCRIPT the measurement result), were recorded on a standardized form by an independent investigator.

Statistical analysis

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Demographic and clinical parameters are expressed as mean ± standard deviation or median ± interquartile range [IQR] as appropriate. According to previously published data of

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our study group [5], sample size calculation indicated that 70 eligible subjects are needed to

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detect a clinically significant difference in bias of 3.5 mmHg with a power of 0.9 at a significance level of 0.05. All pair-wise examination combinations were tested on the log-

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scale using the honest significance difference by Tukey. The spearman correlation coefficient between CVP and HVC was calculated together with bootstrap confidence intervals.

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Agreement and systematic bias between CVP and HVC, was analyzed using Bland-Altmanplots. Conversion of each measurement into comparable values to identify predefined CVP

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categories (low [< 7 mmHg], normal [7-12 mmHg] and high [> 12 mmHg]) were assessed as

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predefined. Analyses were performed with SPSS (version 22.0, IBM Corp., Armonok, NY),

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Results

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and p-values < 0.05 were considered significant.

A total of 135 patients were enrolled between March 2010 and March 2014 and informed consent was obtained for all patients. HVC measurements could be successfully obtained in 82 (60.7%) of the patients. Reasons for the inability to perform the HVC measurement were patients’ inability to lie in a supine position for the duration of the examination (n=2) and lack of a suitable hand vein due to e.g. massive hand edema and/or peripheral vein catheters (n=51).

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ACCEPTED MANUSCRIPT Baseline characteristics of all patients are presented in Table 1. Patients in whom the HVC measurement could be performed had a significant higher systolic blood pressure a lower PEEP (positive end-expiratory pressure in ventilated patient) and a lower mean/minimal CVP than patients in whom the measurement could not be performed. All further analyses were

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performed only in patients in whom HVC could be obtained.

(n = 82) 67 [60;74]

Non included Patients (n = 53) 69 [59;77]

66 (81%)

39 (74%)

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42 (31%) 93 (69%)

30 (37%) 52 (63%)

12 (23%) 41 (77%)

0.089

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Table 1 Baseline Characteristics

34 (25%) 26 (19%) 19 (14%) 9 (7%) 5 (4%) 2 (2%) 10 (7%) 5 (4%) 25 (19%)

19 (23%) 14 (17%) 11 (13% 6 (7%) 3 (4%) 2 (2%) 6 (7%) 3 (4%) 18 (22%)

15 (28%) 12 (23%) 8 (15%) 3 (6%) 2 (4%) 0 (0%) 4 (8%) 2 (4%) 7 (13%)

17 [13;26] 23 [17;28]

17 [14;22] 21 [17;26]

20 [12;30] 23 [17;33]

0.121 0.113

5 [0;10]

5 [0;8]

7 [5;12]

0.005

515 [433;600] 89 [77:89]

520 [450;610] 88 [75;94]

498 [406;580] 89 [80;95]

0.268 0.134

110 [95;124]

116 [98;129]

101 [88;118]

0.002

56 [50;65]

56 [50;67]

56 [53;62]

0.959

15 [12;19] 12 [8;15] 8 [5;11]

15 [10;18] 11 [8;14] 7 [5;10]

16 [13;20] 14 [9;17] 11 [7;13]

0.152 0.017 0.001

HVC patients

(n = 135) 69 [60;76]

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105 (77.8%)

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Male Type of ICU Medical ICU Surgical ICU Critical Illness Coronary Surgery Heart Valve Replacement Sepsis Abdominal Surgery Abdominal Aneurysm Multiple Trauma Pneumonia/ARDS Congestive Heart Failure Other Mechanical Ventilation Respiratory Rate (l/min) Peak Pressure (cm H2O) Positive Endexspiratory Pressure (cm H2O) Tidal Volume (ml) Heart rate (beats per minute)

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Age (years)

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Systolic blood pressure (mmHg)

Diastolic blood pressure (mmHg) Invasive measured CVP (mmHg) Maximum Mean Minimum

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All patients

Significance level p 0.76

0.248

Data are presented as n (%) or median [interquartile range], significant differences in italics.

The distribution of mean CVP values simultaneously measured during HVC examination is shown in Fig 2. The median [interquartile range] invasive reference CVP was 12 mmHg [8;15] with 14.5 % of values classified as low (<7 mmHg), 51.2% medium (7-12 mmHg), and 7

ACCEPTED MANUSCRIPT 34.2% high (>12 mmHg) according to the predefined categories. During examination of each patient the median fluctuation between minimally and maximally measured CVP within the respiratory cycle was 7 mmHg [4;10]. There was no significant difference between ventilated and spontaneously breathing patients (7 mmHg [5;9] vs. 7 mmHg [4;10], p = 0.827). The

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mean CVP was used for all analysis unless stated otherwise.

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Fig. 2 Invasive CVP distribution. Distribution of mean invasive CVP values in mmHg

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measured in 82 consecutive intensive care patients

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The measurement of the HVC took 106 seconds (median, [60;180]). Exam quality was rated poor in 13 (16 %), moderate in 25 (30 %) and good in 44 (54 %) of the study subjects. The

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patient body mass index (BMI) had no significant effect on the feasibility (mean ± SD BMI feasible 24.0±3.9 vs. not feasible 27.1±1.3; p=0.453) and examination quality (poor 23.5±2.2,

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moderate 23.3±3.9 and good 25.7±4.9; p=0.753).

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The median absolute difference between the measured HVC and CVP was 4 mmHg [2;7]. HVC shows a modest correlation with the mean CVP with a correlation coefficient of rs =

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0.548 (95%-CI 0.348-0.694) (Fig 3). The HVC correlations to the minimum and maximum CVP values were 0.443 (95 %-CI 0.232-0.626) and 0.551(95 %-CI 0.360-0.699),

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respectively.

Fig. 3 Relationship between HVC and CVP

The Bland-Altman plot shows a consistent underestimation of the CVP using HVC by 3.4 mmHg (Fig 4). However, the absolute difference between the HVC and CVP values depended on the exam quality. In patients where the exam quality was rated good, medium and poor, the median absolute difference was 3 [1;5], 5 [2;7], and 8 [5;11] respectively, 8

ACCEPTED MANUSCRIPT p=0.0068 (Fig 5). Accordingly, if the exam quality was rated good, 59.5 % of the HVC estimates were within the CVP-range (minimal to maximal CVP value) measured simultaneously during the HVC examination. In contrast, if the exam quality was rated poor only 38.5% were within the measured CVP-range.

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Fig. 4 Bland-Altman plot. HCV and CVP plotted against their mean

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Fig. 5 Boxplot showing the overall range, 25. quartile, median and 75. quartile of the different

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rated exam qualities of HCV

Table 2 shows the performance of HVC only to categorize the CVP as low, normal or high

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(low [< 7 mmHg], normal [7-12 mmHg] and high [> 12 mmHg]). Overall, CVP categorization using HVC was correct in 45 percent of the patients. If the patient`s CVP value was low, HVC

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was correctly categorized in 93 % of the cases, whereas the accordance in patients with a

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normal or high CVP was only 42 % and 29 %. Restricting the analysis to the values obtained in patients with a good HVC examination quality, concordance was 100 %, 56 % and 38 %

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for the low, normal and high CVP categories.

Table 2 Categorial Comparison

HVC in %

CVP in %

Categorization

Low

Normal

High

Low Normal High Sum

13 (93) 1 (7) 0 (0) 14 (100)

26 (50) 22 (42) 4 (8) 52 (100)

8 (24) 16 (47) 10 (29) 34 (100)

Calculated percentages of HVC pressure categories in relation to CVP pressure categories. Numbers in parentheses indicate the percentages of categorized HVC in respect to the 9

ACCEPTED MANUSCRIPT categorical column of CVP. Bold numbers indicate the percentages of identical categorization between both measurements.

Sensitivity, specificity, positive and negative predictive value of HVC to discriminate low (<7

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mmHg) versus normal/high (≥7 mmHg) CVP was 92%, 60%, 28% and 98%, respectively. Accordingly, sensitivity, specificity, positive and negative predictive value of HVC to

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discriminate high (>12 mmHg) versus normal/low (≤12 mmHg) CVP was 29%, 94%, 73%

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and 72%. (Table 3)

Table 3 Sensitivity, Specificity, Positive Predictive Value and Negative Predictive Value of

Sensitivity

Specificity

Positive Predictive Value

Negative Predictive Value

Low (< 7 mmHg)

92 %

60 %

28 %

98 %

High (≥ 12 mmHg)

29 %

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73 %

72 %

94 %

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HCV

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detecting a low (< 7 mmHg) and a high (≥ 12 mmHg) CVP using the HCV method

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Discussion

This prospective study provides several interesting insights into the accuracy of simple hand

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vein inspection for CVP estimation in everyday clinical practice. First, an HVC examination seems to be feasible only in a limited number of tertiary care center ICU patients as reflected by the inability to perform the examination in approximately 40% of the patients at all. Furthermore, hand vein visibility in the remaining patients in whom the measurement finally was performed was only low to moderate in another 50%. Clearly, the poor health status of our ICU patients contributed to the overall poor feasibility of the HVC measurement. Patients after major thoracic surgery precluded a supine position which made it impossible to recline the patient for our study examination or volume overload after 10

ACCEPTED MANUSCRIPT cardiac surgery with consecutive hand edema made it impossible to reliably examine or even see a vein at the patient`s hand. But this might also be the reason why included and excluded patients showed a significant different CVP. The volume overloaded patients with a consecutively elevated CVP rarely show hand veins on the dorsum of the hand and therefore could not be included in our study. No doubt, in these challenging patients several ultrasound

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guided techniques show a higher rate of assessable patients which is in the range of 82 %99.3 % as reported previously [5, 9-11]. However, our ICU study subjects do not represent

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the average emergency patient or patient on the ward who might be in need of a quick

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estimation of the CVP. Based on our clinical experience it is thus reasonable to argue that in these patients the visibility of the hand veins might be better and the HVC examination easier

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to perform.

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Accordingly, Rizkallah and colleagues who also evaluated the HVC in patients scheduled for a regular echocardiography did not report problems to examine the hand veins in their patient cohort [12]. In this study, the authors categorized the HVC as high if, in a supine

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patient, the hand veins remain distended while rested on top of the sternum. An

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echocardiography derived CVP categorization was used as reference (low/normal versus high CVP, a high CVP of >10mmHg was assumed if an IVC diameter >2.1cm or collapsing

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<50% with sniff). A low overall sensitivity of 25% to detect an elevated CVP but a specificity of 86 % for detecting a low/normal CVP were reported. Unfortunately, as Rizkallah and

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collegues did not use the gold standard of invasive CVP measurement, a direct comparison to our results is not feasible. In our cohort, we observed a high sensitivity for detecting a CVP <7 mmHg (92%) and high specificity for a CVP >12 mmHg (94%). Thus, our results indicate that HVC is potentially most useful in 2 clinical settings. First, if the HVC indicates a high CVP, it is reasonable to assume that the patient`s CVP is indeed high (specificity 94%, positive predictive value 73%). Second, if HVC is indicating a normal/high CVP it is very unlikely that the patients CVP is low (sensitivity 92% and negative predictive value of 98%).

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ACCEPTED MANUSCRIPT So it is conceivable to use this quick and easy method as first line bedside test before administration of (high dose) diuretics. Another noninvasive way to assess CVP is the classic technique of estimating jugular venous pressure by watching the neck vein collapse while inclining the upper part of the body. Older and newer studies of validation of this method report a sensitivity >80 % and a

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specificity >90 % [13, 14]. But the classic method seems not to be used very often during

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physical examination due to the complicated procedure or lack of training [15, 16].

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In a previously published trial of our study group three different ultrasound methods have been compared to assess CVP [5]. One of the methods showed a slight superiority over the

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others: compression ultrasound of a forearm vein (CUS). If we compare our results with the results of the CUS method we can assert that the correlation of our results is better (0.548

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vs. 0.485), the median absolute difference of CVP values is the same (3 mmHg of CUS vs. 4 mmHg of HVC) but has a lower CVP categorization match (45 % vs. 61 %). The duration of

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examination time (106 sec) was not shorter than the fastest method of that trial (internal

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jugular vein collapsibility with 60 sec), but was clearly better than the average of the three

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methods (127 sec) (Table 4).

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Table 4 Comparison of CVP with different ultrasound guided techniques

HVC

CUS

IVC-C

IJV-C

Spearman correlation coefficient between method and CVP

0.548

0.485

-0.186

-0.485

Examination time in sec [IQR]

106 [60;180]

188 [125;270]

133 [100;211]

60 [50;109]

Median absolute difference to CVP in mmHg [IQR]

4 [2;7].

3 [2;6.75]

n/a

n/a

Comparison of correlation coefficient, examination time and median absolute difference. CUS: compression ultrasound of a forearm vein, IVC-C: inferior vena cava collapsibility measurement, IJV-C: internal jugular vein collapsibility measurement [5] 12

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Limitations Measurements were performed by one of two clinicians. Inter-and intraobserver variability were not assessed so the results may depend on the observer`s ability to localize and

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inspect patient`s hand veins. However, the described technique is simple and both investigators were experienced vascular specialists, so that the performing manner and

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observer quality is not likely to have been substantial different between the investigators.

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However, it is reasonable to assume that every clinician would have to “train” this new physical examination tool, learning to determine the optimal tactile and visual vein collapse

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using a simultaneously measured invasive CVP pressure as guiding reference.

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As mentioned above, the assessed study subjects were ICU patients that are not representable to the average patient group in e.g. an emergency department. Many ICU patients in our study were at least partially mechanically ventilated. Though we could not

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detect a significant influence of ventilation on the results, controlling of the various ventilation

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parameters is difficult and it cannot be ruled out completely. Performing the study in the ICU setting with relatively stable humidity, temperature and air conditioning we cannot exclude

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that these factors potentially can influence the HCV measurement in the field or other austere environments (i.e. that cold induced peripheral vasoconstriction reduces the

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examination quality).

Further evaluation of this easy bedside examination in other settings e.g. in patients undergoing right heart catheterization seems to be reasonable.

Conclusion Observing the hand veins collapse to estimate CVP showed only a moderate performance in the intensive care setting. In patients with a good examination quality the median difference 13

ACCEPTED MANUSCRIPT to the CVP was negligible low and the negative predictive value of a low HVC was excellent. Further evaluation of this easy bedside examination in other settings e.g. in patients undergoing right heart catheterization seems to be reasonable to clarify its potential role in

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everyday practice.

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