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 PP

Easy 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 compliance• PP >> 30 severely 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 1996Khan, 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

Variable Low Tv Group

Traditional Tv Group

P - value

Death 31% 39.8% 0.007

Off Vent by 28th Day

65.7% 55% 0.001

Organ failure free days

15 12 0.006

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 1994Arnold, CCM 1994

Ventilation Simulator

Not for the weak of heart

The EndMind what you have

learned. Save you it can.

Questions?