Galvagno: Patient-ventilator interactions, perfusion-protection strategies

Today we welcome back Samuel M. Galvagno, DO, PhD, Associate Professor of Anesthesiology & Chief, Division of Critical Care Medicine, University of Maryland School Of Medicine. Dr. Galvagno has an extremely impressive resume, including a Ph.D. from The Johns Hopkins Bloomberg University School of Public Health as well as over 60 peer reviewed publications coupled with years of clinical expertise in airway and ventilator management. Today he is gracious to share some pearls of wisdom to guide the average intensivist in the management of a newly ventilated patient. There is so much information in this lecture that I am certain you will want to watch it multiple times!

Please note, the slides do have some edges cut off, but the information is so important and Dr. Galvagno is such an amazing speaker that we are certain it will not effect your learning! 

Clinical Pearls (assisted by Dr. Ram Baalachandran)

Physiology:

  • Normal intra-thoracic pressure is zero to negative
    • Positive pressure ventilation (PPV) reverses this physiology, making intra-thoracic pressure positive
  • Afterload Reduction
    • Negative intra-thoracic pressure contributes to afterload
      • PPV decreases afterload by increasing intra-thoracic pressure
  • Hypovolemia
    • Induction agents cause venodilation and decrease mean systemic pressure
      • Results in collapse of inferior vena cava and decreased venous return (coupled with PPV leads to a decrease in Preload)
      • Can result in complete CV collapse!

Post-intubation hypotension

  • Positive pressure ventilation + drugs → hypotension
    • Incidence: 9.6-60%
  • Predictors:
    • Use of Neuro-muscular blockade – OR 2.7 (1.12-6.53)
    • Pre-existing low mean arterial pressure – OR 1.25 (1.01-1.55)
    • Shock index (HR/SBP) >0.8 – 67% sensitivity, 80% specificity
    • ESRD
    • Age
    • mSI (HR/MAP) >1.3 – more sensitive and specific than SI

Prevention:

  • Remifentanil 4 mcg/kg (super potent opioid and broken down by esterases)
    • +/- NMB
    • +/- propofol
  • Premedication: Fentanyl:Ketamine:Rocuronium (3:2:1 vs 1:1:1)
    • Ketamine associated with less myocardial depression, less AV dissociation and arrhythmias
  • Pre-intubation volume resuscitation
  • Awake intubation
  • Have a push-dose pure vasoconstrictor ready (phenylephrine, epinephrine)
  • Proper PPV settings
    • PEEP: 5
    • Tidal Volume: 6-8 ml / kg PBW

Case 1:  82 year-old with h/o alcohol abuse, spinal stenosis, cerebral atrophy, transferred for esophageal perforation to the ICU. P-peak=15 and decreasing.

  • Differential Diagnosis
    • Air leak, BP fistula
  • Ventilator pressures:
    • Peak Pressure (P-peak)
      • Indicates airways resistance and elastance
    • Plateau pressure (P-plat) (occlude ETT at end-inspiration)
      • Marker of compliance
  • Increased P-peak (normal P-plat):
    • Aspiration
    • Bronchospasm
    • Secretions
  • Increased P-plat→ Decreased compliance
    • Abdominal distention
    • Atelectasis
    • PTX
    • ARDS
    • Pulmonary edema

Case 2: 39 year-old female with postpartum hemorrhage, with irregular and rapid RR (42) and her flow/time curve shows lack of return to baseline

  • Auto-PEEP:
    • Preventing Auto-PEEP is one of the important goals of ventilation
      • Increased RR→ decreased expiratory time → increased risk of Auto-PEEP
    • Detection:
      • Flow wave: failure of flow to return to baseline at end expiration
      • Pressure-time curve: steady increase baseline pressure
      • Volume wave: lack of return to baseline
      • Flow-volume loop: end-expiration flow does not return to baseline
      • Pressure-volume loop: incomplete loop
    • Treatment:
      • Disconnect the ventilator + Observe blood pressure
      • Decrease I-time
      • Increase expiratory time
      • Decrease TV
      • Sedation/NMB

Case 3: 18 yo male in CSICU awaiting heart transplantation, echo reveals severely depressed LV function, EF 20%

  • Patient is intubated, milrinone and epinephrine infusions started
    • Follow up echo shows moderately depressed LV function
  • Following extubation patient becomes hypotensive, tachycardic. What is most likely cause?
    • Hypotension most likely caused by increase in LV afterload after extubation

Case 4: 45 year olds male with h/o liver transplantation for amyloidosis+ cardiomyopathy (EF = 25%), patient has been on and off milrinone “for weeks”. Intubated for respiratory distress and subsequently became profoundly hypotensive shortly after intubation. Swan-Ganz catheter is inserted: PA pressure 60/42 and CO 2.9.

  • Right Heart Failure – highly preload dependent
    • PPV decreases preload, resulting in hypotension
  • Prevention of hypotension after intubation in right heart failure:
    • Maintain preload
    • Normal to slow heart rate
    • Maintain afterload
    • Maintain contractility
    • PVR – maintain to decrease if possible

Case 5: 76 year-old woman with 60 pack-years smoking history is admitted to SICU following exploratory laparotomy for small bowel obstruction. Patient is dys-synchronous with ventilator. PaO2 is 66 on Fio2 70%, high P-peak is noted.

  • Problems in COPD patients + MV:
    • Dynamic hyperinflation (auto-PEEP ↑, compliance ↓)
    • Displacement of P-V curve to upper flat portion
    • High alveolar pressure (WEST zones 1,2)
    • Narrow ETT
    • Decreased respiratory system compliance
    • Insensitive triggering
  • Goals of ventilation in COPD:
    • Decrease RR to avoid dynamic hyperinflation
    • Use controlled modes of ventilation for limited time only
      • Potential for respiratory muscle atrophy
    • Adjust vent based on dynamic hyerinflation, NOT PaCO2
      • Allow permissive hypercapnia
    • AC/PC with prolonged I:E preferred
    • Add low levels of PEEP
      • Improves triggering and synchrony
    • Controlled hypoventilation
      • Ph>7.20 is ok
      • Moderate academia ok
    • Avoid over-ventilation
  • DON’T try to normalize ABGs

Suggested Reading

  1. Lyon RM, Perkins ZB, Chatterjee D, Lockey DJ, Russell MQ. Significant modification of traditional rapid sequence induction improves safety and effectiveness of pre-hospital trauma anaesthesia. Crit Care. 2015; 19(1): 134. [Pubmed Link]
  2. Price B, Arthur AO, Brunko M, Frantz P, Dickson JO, Judge T, Thomas SH. Hemodynamic consequences of ketamine vs etomidate for endotracheal intubation in the air medical setting. Am J Emerg Med. 2013 Jul;31(7):1124-32. [Pubmed Link]
  3. Smischney NJ, Demirci O, Diedrich DA, Barbara DW, Sandefur BJ, Trivedi S, McGarry S, Kashyap R. Incidence of and Risk Factors For Post-Intubation Hypotension in the Critically Ill. Med Sci Monit. 2016 Feb 2;22:346-55. [Pubmed Link]
About the Author

Jim Lantry

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Just your average critical care doc: Wandering the ED and ICUs for the USAF down in the San Antonio Military Medical Center, traveling the globe to cannulate for ECLS wherever the need arises, and trying to keep up with great minds of today. E: JlantryMD@gmail.com

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Comments

  1. Adrian

    Do you have a link or citation of the Ko article you mention? It sounds like it was about COPD management for ventilated patients.

    1. Author
      Jim Lantry

      I will look for the article as well as contact the speaker in case they have a reliable location for it.

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