PICU Primer II
Kevin M. Creamer M.D.
Pediatric Critical Care
Walter Reed AMC
The Primer Outline
♦ Physiology
– Hypoxia / Hypoxemia– ABG’s and Acidosis
– Sodium and H2O metabolism
– Hemodynamics and Cardiopulmonary interactions
♦ ICU Care
– Postoperative issues
– Mechanical Ventilation
♦ Common Problems – Head trauma– Toxicology
Postoperative Issues
♦Borrowed in part from Akron syllabus♦Know the surgery
– what can you expect from a posterior spinal fusion is different than a tracheal reconstruction
♦Know the patient– Age, PMHx, Syndromes
♦Be there when they get out of the OR
Postoperative Evaluation
♦ABC’s♦Look at the breathing pattern♦Listen to the chest--breath sounds,
stridor?♦Listen to the heart--gallop, murmur?♦Feel the pulses--strong, weak, thready?
– Cap refill?, Extremity warmth?
The Anesthesia Report
♦“History of present illness” for surgical patients– Difficulties with induction or intubation?– Drugs used during case– Regional techniques employed?– Extubation-problems?
♦Vital signs- BP, HR, RR, SaO2, temp– Patients are frequently cold!
The Anesthesia Report
♦Ventilation parameters/difficulties♦Fluids--ins and outs♦Any “events”?♦Lines and tubes
Intraoperative Fluids
♦Pediatrician: “Why do they always get so much fluid?”
♦Anesthesiologist: “Because they need it”– maintenance + replacement of “third
space” losses• “third space” losses can be 15 cc/kg/hr
+ replacement of 3 X blood loss
Anesthesia and Fluid Balance
♦General anesthesia produces vasodilation and some decrease in myocardial contractility.
♦Increased intrathoracic pressure, and stress response to surgical stimulus, may lead to increased ADH production and decreased urine output
BLOOD loss and replacement
♦Blood loss is estimated ♦Transfusion Criteria - it depends
– Check Hct, HR, UOP, pH, ongoing loss, Hemodynamics …
♦When do you need Component Tx?– after a “massive” transfusion or
( 0.75-3.0 blood volumes)
Blood Products - How much?
♦PRBCs - 4cc/kg of will Hb 1gm/dl♦Platelets - 1unit/5kg will ⇑ count by
50000♦FFP - 10 ml/kg round up/down to
closest unit♦Cryoprecipitate - 1bag/every 5-10kg
Surgeons get extremely persnickety if you transfuse THEIR patient without letting them know ahead of time!
The Surgical Report♦ Since we are not surgeons we need to know
what they anticipate and worry about– Amount of pain – Third spacing– Possible complications
♦ Their wish list:– Extubate tomorrow, MRI at midnight– Special meds: antibiotic and stress ulcer
prophylaxis
The Surgical Report
♦What to touch and not to touch?– NG, foley, chest tube, rectum, etc.
♦Check all their orders for appropriate dosing and fluids– mg/kg/dose is not in surgical vocabulary
♦Who is in Charge? (Us vs. Them)♦Surgical POC?
– Interface with surgeons before they return to the OR in AM regarding the plan
Assessment of Fluid Balance:
♦Vital signs (HR/BP)♦Urine output♦Extremity warmth, CRT♦Acid-base status♦Occasionally invasive monitoring
– Remember the Liver!
Extubation Time?
♦Adequate airway (edema? ,Leak?)♦Maintain oxygenation and ventilation ♦Neurologically able to protect the
airway and maintain adequate drive.♦Small/young infants are at increased
risk of apnea– Especially if post-conceptual age <
50weeks
Sedation and Analgesia
♦Analgesia for painful diseases and procedures
♦Compliance with controlled ventilation and routine intensive care
♦Sedation for amnesia for the periods of noxious stimuli
♦Reduce the physiologic responses to stress
Sedation and Analgesia
♦The idea of titrating drugs to effect--there is no “dose”.– Keep in mind what the “target” response is.
♦Consider Round-the-clock Tylenol for 24-48 hours as adjunct– First PR dose may be 30-40 mg/kg
♦Anesthesia service manages Epidurals♦Consider a continuous drip
Drug Morphine Fentanyl Versed Ativan
Dose 0.05- 0.1mg/kg
0.5- 1.0mcg/kg
0.05- 0.1mg/kg
0.05- 0.1mg/kg
Timing(I/S)
5-10 min /2-4 hours
5-10 min/ 1-2
hours
5-10 min /1-2 hours
5-10 min /2-4 hours
Sideeffects
BP, H, A A, CWR BP, A BP, A
Reversal Narcan 2-10 mcg/kg
Narcan 2-10mcg/kg
Flumazenil0.1-0.2 mg
Flumazenil0.1-0.2 mg
BP: hypotension, H: Histamine, A: Apnea,
CWR: chest wall rigidity
Muscle Relaxants
♦ They provide ZERO sedation/analgesia. ♦ Indications (always relative)
– Mechanical ventilation where risk of extubation is great, or risk of baro/volutrauma is high
– Procedures such as central line placement or biopsy in the intubated patient
– Intractable intracranial hypertension (IF ICP being monitored)
Problems with Blockade
♦ Fluid retention♦ Long term weakness
– continuous infusions – most commonly the steroid based NMBs – myopathy associated with Atracurium– consider using cis-Atracurium
♦ Consider Train of Four testing♦ FREQUNTLY OVERUSED
♦NEXT UP
–Mechanical ventilation
This is not the NICU!
Lesson Learned:VALI –Predisposing Factors♦High lung Volumes
– With high peak pressure and alveolar overdistension
♦Repeated alveolar collapse and reopening
♦High inspired oxygen Concentrations♦Preexisting lung injury
Slutsky Am J Resp CCM, 1999, Dreyfuss Am J Resp CCM 1998
Mechanical Ventilation
♦Do’s and Don’ts– Avoid Overdistension and High Pressure by
limiting Tv– Avoid Hyperoxic Lung damage by turning FIO2
down (Sat 90% okay)– Avoid cyclic collapse by using PEEP to recruit
FRC and keep it above Closing volume♦ Infant high risk 2° high elastic recoil and
complaint chest wall
Zone of Overdistension
Zone of Atelectasis
Open Lung Strategy
Getting Started (Parameters)
Oxygenation Ventilation (MV)
PEEP Rate
I-time (flow) Tidal Volume (P)
FIO2
Getting Started (Mode)Volume Pressure
Pro’s Preserve MV Avoid PPEasy Familiar (NICU)
Decelerating Flow
Con’s PP ?? MV??Constant flow
Constant vs. Decelerating flow
Time
F L O w
Time
F L O w
Time
P R E S S U R E
Time
P R E S S U R E
Getting Started (Settings)
♦FIO2 - 50%, if sick 100%
♦It - minimum .5 sec, older kids 1 sec♦Rate - age appropriate 15 -30 to start♦Tv - 10ml/kg to start ♦Look / Listen / Ask♦PEEP - 4cm, higher if FRC
compromised
IT and Time Constants
• The time to fill each alveolus is determined by its time constant
• TC= Resistance X Compliance
• A Short IT decreases TV, or increases PIP
Full equilibration
IE
EI
TT
TPEEPPIPTMAP
+×+×= )()(
Mechanical Ventilation
♦First hour– CXR and “Blood Gas”– Watch peak pressures as compliance
estimate• PP << 20 ideal• PP 20-30 moderately P compliance• PP >> 30 severely P compliance• PP >> 35 high risk for VALI, DO
SOMETHING
Mechanical Ventilation
♦Change Tv only for inappropriate chest rise or for elevated inspiratory pressures (Don’t WEAN Tv)
♦Sedation to allow patient - ventilator synchrony (Paralytics aren’t required)
Monitoring adjuncts
♦Pulse oximeter♦End tidal CO2 - can use for Dead space
estimate♦ABG’s and CBG’s♦Calculate Compliance, A-a gradient,
Oxygenation Index (OI), check for Autopeep
♦Graphics - PV and flow-volume loops
Equations
♦Dead Space = 1 - (EtCO2/PaCO2)
♦Static Comp. = Tv/ (Pplat- PEEP)
♦A-a gradient =
– (Pb-PH2O) x FIO2 - (PCO2/.8) - PaO2
♦ OI = (Paw x FIO2 x 100)/ PaO2
When things go wrong♦ Don’t be a DOPE♦ Hypoxemia - PEEP to ⇑ FRC, to allow FIO2
wean to < 50%♦ Elevated peak pressures - suction, adopt
Permissive hypercapnia, consider changing to pressure mode
♦ Check circuit size– an inappropriately large circuit can gobble up
lots of tidal volume
PEEP
PIP
TI
RateFlow
Pressure
TimeTI TE
PEEP
PIP
Paw (Area Under Curve )increases with increasing:PIP, PEEP, TI/TE Ratio, Rate, and
Flow
Circuit compliance
♦When using volume ventilation the ventilator circuit or tubing will stretch – Neonatal 0.35 ml / cm H2O
– Pediatric 1.4 ml / cm H2O
– Adult 2.8 ml / cm H2O
♦This means the stiffer the lung the more volume is lost in the circuit
Mechanical Ventilation
♦ First day and beyond– Watch for fluid overload
• all patients on positive pressure ventilation retain lung water
– Assist patient efforts• Pressure support or volume support• Trigger sensitivity (age and disease appropriate)
– Treat underlying condition– Feed patient
Weaning
♦ Get condition under control♦ Stop paralytics (PEEP < 8)♦ Encourage patient’s efforts
�⇓ Rate (slow then fast)– add Pressure support (2/3 ∆P)
♦ Wean PEEP and PS slowly in 1-2 cm H2O increments
♦ Wean FIO2 to 30% if possible
Signs of weaning failure
♦Increased Work of breathing– fast spontaneous RR
– small spontaneous Tv
♦Increased FIO2requirement
♦Hemodynamic compromise
Time for Extubation?
♦Think SOAP–Secretions / Sedation / Spontaneous Tv
(>5ml/kg)
–Oxygenation <35%
–Airway - Maintainable?, Leak? , Steroids?
–Pressures - PP <25, PEEP < 5
Extubation success predictors
Variable Low risk <10% High Risk >25%
VTspont
>6.5 ml/kg <3.5 ml/kg
FIO2 <.30 >.40
OI <1.4 >4.5
PIP <25 >30
Khan, CCM 1996
Special situations I
♦Obstructive Diseases– Asthma and RSV Bronchiolitis
– Watch for air trapping / breath stacking• Low rate, larger Tidal volume, long
Expiratory time• check Autopeep• preserve I-time • Consider Heliox, Ketamine, Halothane
Special situations II
♦ARDS– Limit Tv accept hypercapnia– Increase PEEP for FRC– Prone positioning�⇑ CaO2 and tolerate lower Sat %
– consider High Frequency Oscillatory Ventilation>>> Surfactant>>> Nitric Oxide
Volutrauma
0.0061215Organ failure free days
0.00155%65.7%Off Vent by 28th Day
0.00739.8%31%Death
P - value
Traditional Tv Group
Low Tv Group
Variable
861 patients 6ml/kg vs 12ml/kg Tv
ARDS Study Group, NEJM, 2000
Biotrauma
♦ RCT 44 adults with ARDS– TV 7.6 vs. 11.1
– PP 24 vs. 31 cm H2O
♦ At 36° patients in low TV group had significantly lower levels of TNF and IL-1ra in both plasma and BAL fluid
0
5
10
15
20
25
30
35
40
StandardTV
Low TV
Organ Failure
Entry
3-4 days
Ranieri, JAMA,1999; Ranieri JAMA, 2000
Organ Failure
Special situations III
♦Head Trauma– Avoid Hypercarbia (PCO2 < 35)
– Avoid Hypoxemia
– PEEP may adversely effect venous return and ⇑ ICP
– Coughing/gagging extremely bad (Use paralytics)
Special situations IV
♦HFOV Indications– ARHF with OI > 13 for 6 hours– Contraindicated in High airway
resistance, ⇑ ICP, unstable hemodynamics
♦Part of an Open lung strategy with ⇑ Mean airway pressure and Tv < dead space
HFOV vs. CMV
♦Crossover study acute hypoxemic respiratory failure in children
♦HFOV 17/29 responded, 0/17 died♦CMV 10/29 responded, 4/10 died♦X-over to HFOV 11/19 survived♦X-over to CMV 2/11 survived
Arnold, CCM 1994
The EndMind what you have
learned. Save you it can.
Questions?