Respiratory problems in the OB PACU Tom Archer, MD, MBA Director, OB Anesthesia UCSD Hillcrest August 16, 2012

Vast subject for one hour Keep it practical and clinical. Keep it focused on OB and PACU. Enough anatomy and pathophysiology to give background and depth.

What we like from nurses and OBs: Get us involved early! –We should never be upset with your getting us involved early in patient care! Morbid obesity Asthma Anesthesia fears, Hx of problems Any significant medical problem

Use simple observation Talk with and examine the patient. Don’t think too much about fancy tests.

Signs and symptoms What is the patient experiencing? Talk to her! Is she cyanotic? Put her on O2! What is her voice like? Does sitting up make it better (diaphragm descends, lung expands)? Can the patient move her arms and legs?

Signs and symptoms How much air is the patient moving? Put your hand to her mouth. What do you hear when you ask her to take a rapid, deep breath? Has she had breathing problems in the past (asthma)? What does she usually use (rescue inhaler)?

Signs and symptoms What is the SpO2? Is the sensor applied properly? Same side as BP cuff? What do you hear on auscultation? Listen in all lung fields. Anything? Rales, wheezes, stridor?

Signs and symptoms Rales: too much fluid in the alveoli. Wheezes: (expiratory sound) narrowed intra-thoracic (bronchial) tubes Stridor : (inspiratory sound): narrowed extra-thoracic trachea or larynx.

Signs and symptoms What are the neck veins like? CXR– essential for any serious problem ABG– nice if you can get it, but don’t waste time and effort if you can’t. Think arterial line for serial ABGs.

What is the patient experiencing? Talk to her! Don’t forget to talk with the patient! When did the problem start? Has this ever happened before? Does she have chest pain?

Put her on O2! Is she cyanotic? Cyanosis means there is de-oxygenated blood, blood is not “matched” with O2. Blood that passes through the lung without getting exposed to oxygen. “Shunt” or “low V/Q”

The dance of pulmonary physiology— Blood and oxygen coming together. ml

Sometimes the match between blood and oxygen isn’t perfect!

Alveolar dead space High V/Q Shunt Low V/Q Diffusion barrier Failures of gas exchange alveolus capillary

ABGs In respiratory distress, we expect both PO2 and PCO2 to be decreased. If PO2 is decreased and PCO2 is increased, this is a true emergency! Normally, hyperventilated parts of lung will compensate for hypoventilated parts of lung for CO2, but not for O2

Respiratory changes of pregnancy: Mother-to-be is consuming more O2, producing more CO2 and is breathing harder!

Feto-placental unit 12 ml O2 / kg / min Mom 4 ml O2 / kg / min Mother is consuming and delivering oxygen for two!

At term, mother has respiratory alkalosis with metabolic compensation (less HCO3- buffer). ABGsNon- pregnant At term PaCO24030 PaO pH HCO Chestnut

Functional residual capacity (FRC): gas left in the lung after we breathe out.

Functional residual capacity (FRC) is our “air tank” for apnea. from Google images

Pregnant Mom has a smaller “air tank”. Non-pregnant woman /blog/images/scuba- web.jpg

Pregnant patient has less “margin of safety” for apnea. If pregnant patient stops breathing she will desaturate faster than non-pregnant patient. Apnea from: hypotension, seizure, anesthesia induction, high spinal, magnesium overdose, etc.)

“Ramping up” the obese patient to facilitate intubation. Sitting up will also help any respiratory problem in the PACU.

Specific respiratory problems

Asthma-- has she had breathing problems in the past?

Wheezing Expiratory sound. Worse with low lung volumes. Smooth muscle contraction + airway edema + secretions Sit patient up / beta agonist rescue inhaler / steroid?

Wheezing is not a complete diagnosis Smooth muscle spasm (bronchospasm) can cause wheezing. Airway edema can cause wheezing (fluid overload, CHF)

All That Wheezes Is Not Asthma: Diagnosing the Mimics asp?template=0&pag...

Author Samee, S ; Altes T ; Powers P ; de Lange EE ; Knight-Scott J ; Rakes G Title Imaging the lungs in asthmatic patients by using hyperpolarized helium-3 magnetic resonance: assessment of response to methacholine and exercise challenge Journal Title Journal of Allergy & Clinical Immunology Volume 111 Issue 6 Date 2003 Pages: He3 MR showing ventilation defects in a normal subject and in increasingly severe asthmatics.

Pulmonary edema

Pulmonary edema is not a complete diagnosis! Too much water in the lung. Hydrostatic pressure: heart failure or simple fluid overload. Alveolar capillary damage and fluid leak: aspiration, sepsis (both lead to ARDS).

Pulmonary edema Hydrostatic– too much pressure in the alveolar capillaries (normal lung + too much fluid pressure). –Too much IV fluid (pre-eclampsia) –Congestive heart failure (peripartum cardiomyopathy? LV failure with pre- eclampsia?) –Renal failure

Pulmonary edema Increased capillary permeability (lung damage). –Pre-eclampsia –Aspiration (usually with GA) –Sepsis (chorioamnionitis) –Anaphylaxis (antibiotics) –Pulmonary embolus –Amniotic fluid embolus (very rare)

Atelectasis An area of lung is compressed. –External compression (obesity, pregnancy, supine posture) –Gas absorption (mucus plug) or after right mainstem bronchus intubation. –Treatment is upright posture, deep breathing and removal of mucus plugs.

Atelectasis in obesity– dependent regions

Atelectasis– left upper lobe

Right mainstem bronchus intubation

Has her voice changed? Does she have stridor? Voice change– larynx change –Edema from ETT trauma –Edema from pre-eclampsia –Allergic reaction (hereditary angioedema).

The AIRWAY can be closed off by swelling of tongue or larynx.

Normal larynx

Laryngeal edema– voice change or stridor

Elective/images/anesth0018.jpg

Stridor Inspiratory “crow”. Listen with stethoscope over the neck as part of your exam. Stridor suggests obstruction in the trachea, vocal cords or throat.

Neuromuscular paralysis: can the patient move her arms and legs? Did she recently get a dose of epidural local anesthetic (for post-op pain relief)? Does she have a “high spinal” or epidural? Did she get a GA? Does she have residual neuromuscular blockade?

Can the patient move her arms and legs? Magnesium will exacerbate neuromuscular disease or neuromuscular blocking agents. Does she have unrecognized neuromuscular disease? Myasthenia gravis?

Pulmonary embolus

Can have normal chest x-ray. Can have pain, or not. Spiral CT is fancy test of choice. V/Q scan is not nearly as good a test.

Pulmonary embolus May be associated with hypotension. May be associated with distended neck veins.

Pneumothorax After GA and intubation Feel for subcutaneous emphysema (air). Rice crispies at base of neck. Tension pneumothorax would have distended neck veins and hypotension.

Tension pneumothorax

Distended neck veins

General measures Put her on oxygen by mask, at least 6 L/min (but increasing rate beyond 6 makes little difference). Sit her up in bed (but watch for hypotension if neuraxial block is in place). Make sure SOB is not due to hypotension.

How much air is the patient moving? Put your hand to her mouth. With chest wall numbness patient does not feel herself breathing, but can be breathing very well. If tidal volume really is decreased, this is a true emergency!

Respiratory emergency Respiratory rate > Cyanosis or low sats Rising CO2 (arterial) Patient tiring out. Change in consciousness. Seizure (think hypoxia and / or aspiration)

Respiratory emergency Think: anesthesiologist, oxygen, intubation, crash cart, Ambu bag, suction, getting to head of bed, call for ventilator, CXR. But get patient well oxygenated before intubation, if possible, because of delay in intubation and rapid desaturation.

Summary Respiratory problems are infrequent in OB– young, healthy patients. Take a good history. Make simple, systematic observations. Is the patient in bad trouble?

Summary Please get us anesthesiologists involved early. Thank you!

The End