Mechanical ventilation and RAD

Dr Satish Deopujari

Prof. K. Chellum Oration / CMC Vellore

26th June 2004

Incidence of M.V. in RAD in India ?

Do we under ventilate these patients.

Aggressive management ………..

Proper oxygenation warmed and humidified

Continuous nebulization what dose ?

Look for hypokalemia

Steroids / Ipatropium bromide / MgSO4

Hydration / Ensure good Hemoglobin level.

Avoiding agitation

Ketamine

Newer modalities

MgSO4

Mechanism of Action Antagonizes translocation of Ca across cell

membrane, leads to SM relaxation and Inhibits degranulation of mast cells

Decreases release of ACH (decreases excitability of muscle fibre membranes)

Side Effects: Facial warmth/flushing, hypotension, nausea, emesis,

muscle weakness, sedation, loss of DTRs, resp depression

Dose: 20-40mg/kg IV over 30 min

• The decision to intubate pt in SA , is made on the basis clinical

deterioration,

• Altered level of consciousness

• Exhaustion / P. paradoxus

• Inability to protect airway

• Increasing arterial PCO2.

• Quiet chest, absence of audible wheezing

• PaO2 < 60 mmHg : not responding to adequate oxygenation

• PaCO2 > 50 mmHg and rising more than 5 mmHg/ hour

• Zimmerman et al, reported that one or

more complications occurred in 46% of

intubated asthmatics.

• More than one-third of all complications

occurred during intubation.

• 47 % of complications during the

intensive care unit stay

• Difficult and esophageal intubations

occurred in about 15% of all patients

Standard preparation for rapid sequence

intubation .

cardio-respiratory and blood pressure

monitoring

Assistance

monitoring of oxygen saturation

careful aspiration of oropharynx

bag and mask ventilation with 100% oxygen

emptying of the stomach by nasogastric tube

benzodiazepine should be considered (e.g.,

midazolam 0.1 - 0.2 mg/kg) permitting

relaxation during preoxygenation

Ketamine hydrochloride (1 to 3 mg/kg)

Good choice for its sedative and

analgesic effects as well as its

bronchodilating characteristics.

Concomitant use of a benzodiazepine

can suppress the dysphoric effects of

Ketamine.

Ketamine increases laryngeal secretions

but does not block pharyngeal and

laryngeal reflexes, increasing the risk of

laryngospasm and aspiration in the

preintubation period

Endotracheal tube…………….

largest endotracheal tube…..

lower airflow resistance

Suctioning of thick mucosal secretions

Fiber optic bronchoscopy : facilitated

A cuffed endotracheal tube

Sometimes useful even in small children

(<5 years)

when insufflation pressures become very

high (Hubert 1996).

Intubation………….

oxygenation

H2 blockers , prokinetics . atropine

Lignocaine 4 % neb. 4mg / kg ( 1ml = 40 mg )

Sedation midazolam + ketamine / cricoid

pressure

Paralysis ( Vecuronium .1 to .2 mg / kg )

Intubation

Suction

Confirmation of tube and proper fixation

Avoid positive pressure V. without cricoid P.

Proper monitoring

Oxygenation & Circulation status

Fluid bolus for circulation

Lt heart pumps what

the

right heart gives it

Ventilatory strategy

Permissive hypercapnia

low rate 50 % for the age

low pressure

Avoiding barotrauma

low pressure

Minimal PEEP

Intrinsic PEEP

Dynamic hyperinflation (DHI)

PEEP

Controversies remain about the role of PEEP in

status asthmaticus.

Majority of cases, no PEEP should be applied

during mechanical ventilation (0 3 cm H2O

maximum)

PEEP

Intrinsic PEEP

Air leak syndrome

A 'rapid sequence' for

extubation is justified

by the risk of further

bronchoconstriction

induced by the

presence of the

endotracheal tube.

• Adding adjuvant therapy despite lack of

evidence is reasonable given the risks

associated with intubation and mechanical

ventilation

• More research is required in childhood status

asthmaticus!

M. Ventilation is a BLEND of Art and science

TH

AN

KS

• Adding adjuvant therapy despite lack of

evidence is reasonable given the risks

associated with intubation and

mechanical ventilation

• More research is required in childhood

status asthmaticus!

Mechanical ventilation

• Less than 5% of patients with SA

required intubation and MV, “braman et

al, jama 1990”

• Indications: • To decrease work of breathing.

• To maintain adequate oxygenation .

• Augment alveolar ventilation in face of airway

edema and diffuse mucus plugging of of the

small airways…

Indications of mechanical ventilation

Not governed by numbers but by the clinical conditions.

PaO2 < 60 mmHg or cyanosis not corrected by oxygen administration

PaCO2 > 50 mmHg and rising more than 5 mmHg/ hour

The decision to intubate and ventilate a child with status asthmaticus

is primarily based on clinical criteria:

respiratory muscle fatigue, obvious exhaustion, disappearance of

pulsus paradoxus

diminution of thoracic amplitude during respiratory movements

diminution of air entry in the lungs : quiet chest, absence of audible

wheezing

pulsus paradoxus > 20 - 40 mmHg (inspiratory decline in systolic

blood pressure)

deterioration of mental status (lethargy, agitation, confusion, coma)

diaphoresis in recumbent position

•ideal ventilator settings reduce dynamic hyperinflation

(DHI): limited minute ventilation (MV) using an

appropriately low but adequate tidal volume (Vt) and

respiratory rate, with an extended expiratory time (TE)