Invasive Versus Non-invasive Assessment of Blood Pressure in Hypertensive Disorders of Pregnancy
Condition: Hypertension in Pregnancy
MeSH terms: Toxemia; Hypertension, Pregnancy-Induced; Hypertension
Study type: Interventional

Summary: 
      Hypertensive disorders of pregnancy are important causes of maternal morbidity and mortality
      worldwide. Hypertension is one of the most commonly reported health conditions among pregnant
      women and complicates 5-10% of all pregnancies.(Martin et al., 2009) (Wagner et al., 2007)
      The measurement of central BP in hypertensive patients became more important because of its
      predictive value for cardiovascular events. Direct intra-arterial readings are considered to
      be the gold standard method for blood pressure measurement but because arterial cannulation
      is associated with risks, alternative non-invasive blood pressure measurements may be used.
      (Araghi et al., 2006) In our study, the investigator aimed to assess the accuracy of
      non-invasive central blood pressure by oscillometric automated device (Mobil O graph) in
      comparison to the invasive blood pressure measurement by arterial cannulation in patients
      with hypertensive disorders in pregnancy.

      the investigators enrolled 100 pregnant women and 10 healthy non-pregnant women as a control
      group, central blood pressure was measured invasively by arterial cannula and non-invasively
      by oscillometric automated device (Mobil O Graph).

      the investigatorshave found a high correlation between non-invasive central blood pressure
      measurements and invasively measured both systolic (r 0.968, p=0.000) and diastolic (r 0.687,
      p=0.000).
    

Detailed description: 
      Study Methods:

      All patients included in our study were subjected to the following:

        1. Full history taking including:

           Age, full obstetric history including (number of previous pregnancies and abortions),
           history of previous illness, duration of pregnancy.

           Risk factors for developing hypertension as Diabetes Mellitus (DM), history of chronic
           hypertension, anti-hypertensive treatment, history of HTN during previous pregnancies.

        2. Full physical examination:

           On admission: Patient's weight and height were obtained to calculate Body surface area
           (BSA) Vital signs assessment regarding arterial pulse, arterial blood pressure
           measurement using mercury sphygmomanometer and proper arm cuff according to the recent
           guidelines of arterial hypertension General and local cardiac examination.

        3. Investigations : the followings were done at time of hospital admission:

             1. Urine analysis: was done to all participants to exclude the presence of albuminuria

             2. Echocardiography:

      All participants underwent resting transthoracic 2D echocardiography, Scans were acquired by
      a standard parasternal/apical views using (VIVID S5 instrument, GE Medical Systems, Horten,
      Norway) with subjects in the left lateral decubitus position.

      4) Blood pressure assessment: was done after control of blood pressure by different
      anti-hypertensive drugs mostly on 3rd- 4th day of admission.

        1. Office blood pressure measurement: BP in pregnancy was measured in the sitting position
           (or the left lateral recumbent during labour) with an appropriately sized arm cuff at
           heart level and using Korotkoff V for DBP. Manual auscultation was the only method used
           as it remains the gold standard for BP measurement in pregnancy, because automated
           devices tend to under-record the BP and are unreliable in severe preeclampsia.

        2. Non-invasive central BP monitoring: measured by MOBIL-O-GRAPH:

             -  The non-invasive assessment of estimated PWV was performed in a quiet,
                temperature-controlled examination room

             -  Three measurements were taken with a 2-min break between them. The procedure was
                performed with the patient in a sitting position and using an adequately sized
                cuff. The Mobil-O-Graph 24h NG (IEM, Stolberg, Germany) with inbuilt ARCSolver
                (Austrian Institute of Technology, Vienna, Austria) This device is a commercially
                available brachial oscillometric blood pressure monitor with Food and Drug
                Administration and Conformite´ Europe´enne approval. Its blood pressure detection
                unit is validated according to the British Hypertension Society and European
                Society of Hypertension recommendations. Algorithms were used to obtain
                conventional blood pressure readings such as brachial systolic and diastolic
                pressures. In the second step, the brachial cuff is inflated to the diastolic blood
                pressure level and held for about 10s to record the pulse waves. Subsequently,
                central pressure curves obtained through a transfer function from the peripheral
                reading are plotted. To estimate aPWV, the ARCSolver method utilizes several
                parameters from pulse wave analysis and wave separation analysis combined in a
                proprietary mathematical model, whereby the major determinants are age (Mendes,
                2015) , central pressure, and aortic characteristic impedance.

        3. Invasive blood pressure measurement:

      Cannulation technique:

      Percutaneous cannulation is performed under aseptic conditions, using the radial artery. The
      hand and forearm are affixed to an arm board, with the wrist dorsiflexed over a bandage roll.
      The thumb should be immobilized as well, to ensure proper anchorage of the artery. the
      investigators infiltrate subcutaneously with 2% lidocaine as a local anaesthetic, it helps
      also to minimize arterial spasm.

      Using palpation of the artery as a guide, the cannula (20-gauge Teflon cannula) is advanced
      at a 20° angle to the skin until the arterial wall is pierced. The stylet is then held fixed
      and the cannula advanced up the arterial lumen.

      The cannula was connected to a disposable tubing system and flushed intermittently with
      heparinized 0.9% saline solution. This helped prevent occlusion of the cannula by thrombus
      .The tubing should be stiff and not contain any bubbles in order to minimize resonance and
      damping.

      The liquid within the tubing was connected to a transducer (Auto Transducer®; ACE Medical,
      Inc., Goyang, Korea). The transducer needs to be kept horizontally level with the patient;
      traditionally, the right atrium because raising or lowering the transducer relative to the
      patient will alter the reading. Zeroing was performed by opening the transducer to
      atmospheric pressure and electronically zeroing the system.

      The arterial blood pressure signals were recorded and displayed on a bedside monitor (GE
      Datex-Ohmeda S/5TM Anaesthesia Monitor, Helsinki, Finland).The whole tubing system was
      flushed with sterile normal saline to eliminate air bubbles and tested for system loss.
    

Intervention name(s): Invasive blood pressure assessment by radial artery canulation
Intervention type(s): Diagnostic Test
Intervention description(s): radial artery canula used to measure central blood pressure compared to non invasive automated device to measure BP in pregnant females
Other intervention name(s): non invasive assement of BP by automated ossilometric M-Moblie graph
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: invasive blood pressure; non-invasive blood pressure