CO2 Versus Lund De-airing Technique in Heart Surgery
Condition: Aortic Valve Disorder
MeSH terms: Aortic Valve Disease
Study type: Interventional

Summary: 
      To evaluate which of the two de-airing methods (CO2 insufflation vs. Lund de-airing
      technique) can shorten the left heart de-airing time and prevent or minimize cerebral air
      emboli during open surgery involving exposure of the left heart to the ambient air.

      To evaluate the cost effectiveness and possible side effects of CO2 de-airing technique
      compared to Lund de-airing technique.
    

Detailed description: 
      Study design:

      Prospective, randomized and controlled study involving 20 patients, 10 in each group. The
      de-airing time and the efficiency of the techniques will be assessed by trans-esophageal
      echocardiography (TEE) and trans-cranial echo-doppler monitoring (TCD). The cardiologists
      analyzing the TEE recordings will be blinded to the de-airing technique used (the recorded
      videos will be analyzed at the end of the study). The TCD monitoring will be done by on-line
      automatic recording of the micro embolic signals (MES) from the right and or left middle
      cerebral arteries and performed by single surgeon. The CO2 insufflation of the operating
      field will be performed according to manufacturer's guide lines. During entire study course
      one type of extracorporeal perfusion system will be used.The study will be registered in the
      international database. A prior approval will be sought from the hospital ethical committee
      for the study.

      Patient selection:

      Patients planned for aortic valve/root replacement or repair will be selected for the study

      Exclusion criteria:

      Patients with known: a) chronic obstructive pulmonary disease, b) emphysema, c) previous
      thoracic or cardiac surgery, d) history of CVA or stroke and e) evidence of intraoperative
      pleural adhesions will be excluded from the study. Patients requiring internal mammary artery
      coronary bypass will also be excluded.

      Patient consent:

      A written consent previously approved by the hospital ethical committee will be obtained from
      all patients before they are enrolled in the study (enclosure 3).

      De-airing procedure:

      Enrolled patients will be assigned randomly to one of the two following groups:

      Control group ( newly developed de-airing technique in Lund ) :

      In these patients (n=10) the pleura will be opened on both sides and the ventilator will be
      disconnected before aorta is cross-clamped and cardioplegia administered. At the end of the
      cardioplegic arrest, the aortic root and the LV will be actively vented and aortic cross
      clamp released. The time will be noted down (T1). The heart will be defibrillated to sinus or
      pacemaker induced rhythm. The heart will be kept empty by the LV vent and ejection avoided as
      monitored by continual intraoperative TEE and systemic arterial pressure tracing. At 35
      Celsius body temperature, as measured from the thermistor in the urinary bladder, and with
      apparently good cardiac contraction the de-airing will begin. Inotropic drugs or systemic
      arterial vasodilators will be used as and when necessary to achieve good cardiac contraction.
      The time will be noted down (T2) (T2 - T1 = Pre ejection de-airing time). The LV preload will
      first now be successively increased by reducing the venous return from the heart-lung machine
      to raise CVP between 5-10 cm water. LV vent will be continuously regulated depending upon the
      amount of residual air showing in the left heart. When no air is seen on TEE monitoring in
      the left heart (LA, LV & Aorta), half the calculated minute ventilation with 100% oxygen and
      a PEEP of 5 cm H2O will be started. De-airing will be continued and when the TEE shows no or
      minimal air in left heart, full ventilation with unchanged PEEP will be restored. The patient
      will be weaned successively from the CPB thereby ensuring that entire cardiac output is
      diverted through the native fully ventilated lungs. When TEE will show no air in the left
      heart, the de-airing will be considered complete and the time noted again (T3) (T3 - T2 =
      Post ejection de-airing time).

      All cardiac cannulae including the LV vent will be left in situ but clamped, patient weaned
      completely from the cardiopulmonary bypass and monitored for residual air by TEE & TCD for 10
      minutes continually. The LV vent will be re-opened whenever the residual air in the left
      heart exceeds grade II. The frequency of theses measures will be noted in the protocol. If
      the patient has by now achieved 36 Celsius core temperature, the heart will be decannulated
      and CPB removed. Otherwise CPB will be restarted and patient warmed to 36 Celsius before
      final weaning and decannulation.

      Study group ( CO2 insufflation ):

      In these patients (n=10) the pleurae will not be opened. During aortic cross-clamp period the
      ventilator will be adjusted to provide dead space ventilation only i.e. 5cm PEEP, ventilator
      frequency 5/min and the minute ventilation = 1,5 liter. Fio2 = 50%. The operating field will
      be insufflated with CO2 at a flow rate of 10 L / minute starting 2 minutes before cardiac
      cannulation and continued until 10 minutes after termination of the CPB.

      At the end of the cardioplegic arrest, the aortic root and the LV will be actively vented and
      the time noted down (T1). The LV preload will be successively increased by reducing the
      venous return from the heart-lung machine to raise CVP between 5-10 cm water. LV venting will
      be continued and when no air bubbles are seen in the left heart (LA, LV & Aorta) under TEE
      monitoring, the calculated minute ventilation with 100% oxygen and PEEP of 5 cm H2O will be
      restored. De-airing will be continued and when no or minimal air is seen in the left heart
      the time will be noted down (T2) (T2 - T1 = Pre ejection de-airing time). Aortic cross-clamp
      will be released now and heart defibrillated to sinus or pacemaker induced rhythm and
      de-airing continued. At 35 Celsius body temperature, as measured from the thermistor in the
      urinary bladder, and with apparently good cardiac contraction the patient will be weaned
      successively from the CPB ensuring thereby that the entire cardiac output is diverted through
      the native fully ventilated lungs. Inotropic drugs or systemic arterial vasodilators will be
      used as and when necessary to achieve good cardiac contraction. When TEE will show no air in
      the left heart, the de-airing will be considered complete and the time noted again (T3) (T3 -
      T2 = Post ejection de-airing time). The patient will be weaned completely from the
      cardiopulmonary bypass and all cardiac cannulae including the LV vent will be left in situ
      but clamped. The patient will be monitored now for residual air by TEE & TCD for 10 minutes
      continually. The LV vent will be re-opened whenever the residual air showing on TEE in the
      left heart exceeds grade II. The frequency of theses measures will be noted in the protocol.
      The C02 insufflations will continue until the 10- minute post CPB monitoring interval is
      completed. If patient by now has achieved 36 Celsius core temperature, the heart will be
      decannulated and CPB removed. Otherwise CPB will be restarted and patient warmed to 36
      Celsius before final weaning and decannulation.

      Trans-esophageal echocardiographic study (TEE):

      After completion of the cardioplegic arrest and for 10 minutes after termination of the CPB,
      all the patients will be monitored by TEE for air in the left heart. The residual air showing
      on TEE after the termination of CPB will be quantified in 4 grades depending upon presence of
      air in LA, LV and aortic root during one cardiac cycle (grade 0 = no or occasional air in LA,
      grade 1 = air showing in LA only, grade 2 = air showing simultaneously in LA and LV, grade 3
      = air showing simultaneously in LA, LV and the aortic root). The 10-minute post CPB TEE
      recording will be saved on a video-tape.

      Trans-cranial echo-doppler study (TCD):

      After release of the aortic cross clamp and for 10 minutes after the patient has been weaned
      off from the CPB, the patient will be continuously monitored for micro embolic signals by
      on-line automatic TCD placed on middle cerebral arteries.

      Blood gases will be monitored in all patients as following:

      Blood gas analysis from arterial & venous blood of the patient every 15 minutes in the
      operating room in both groups until 15 minutes post CPB) - following attached tables
      (Anesthesia, Perfusion and TCD & Invous monitoring)

      Measurement of end-tidal PCO2 and volume of expired CO2 every 15 minutes after the patient is
      intubated and till the time patient leaves the operating room in both groups. (No
      measurements possible in the control group during cardioplegic arrest)

      Blood gas analysis from arterial & venous blood lines of the oxygenator and from the LV vent
      line every 15 minutes while the patient is on CPB in both groups.

      Continuous on-line monitoring of CO2 content and PCO2 in the blood at the inflow and outflow
      ports of the oxygenator in both groups using CDI & new machine. Variations in gas flow and
      the FiO2 needed to adjust PaCO2 to within a fixed desirable range will be recorded and extra
      blood gas sample will be taken whenever any such adjustment is made.

      Alfa stat will be employed for blood gas analysis. A core temperature at 30 C will be used
      for all patients unless positively indicted.
    

Intervention name(s): Lund de-airing technique; carbon-dioxide insufflation
Intervention type(s): Procedure; Drug
Intervention description(s): In these patients the pleura will be opened on both sides and the ventilator will be disconnected before aorta is cross-clamped and cardioplegia administered. At the conclusion of the surgical procedure, the LV preload will first now be successively increased. When no air is seen on TEE monitoring in the left heart (LA, LV & Aorta), half the calculated minute ventilation with 100% oxygen and a PEEP of 5 cm H2O will be started. Deairing will be continued and when the TEE shows no or minimal air in left heart, full ventilation with unchanged PEEP will be restored. The patient will be weaned successively from the CPB. When TEE will show no air in the left heart, the de-airing will be considered complete.; In these patients (n=10) the pleurae will not be opened. During aortic cross-clamp period the ventilator will be adjusted to provide dead space ventilation only i.e. 5cm PEEP, ventilator frequency 5/min and the minute ventilation = 1,5 liter. Fio2 = 50%. The operating field will be insufflated with Co2 at a flow rate of 10 L / minute starting 2 minutes before cardiac cannulation and continued until 10 minutes after termination of the CPB.At the end of the cardioplegic arrest, the de-airing procedure is similar to that in the Lund de-airing group.
Other intervention name(s): cardiac de-airing; cardiac venting; Cardiac de-airing; Cardiac venting
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Cardiac de-airing; CO2 insufflation; Air emboli; Trans cranial doppler; Intraoperative echocardiography