11/6/2013 Oxygen Hemoglobin Carbon Monoxide CO-Hgb 4 11/6/2013 - - PowerPoint PPT Presentation

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11/6/2013 Oxygen Hemoglobin Carbon Monoxide CO-Hgb 4 11/6/2013 - - PowerPoint PPT Presentation

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11/6/2013 Disclosures Smoke inhalation No financial relationship to any commercial products discussed in this Craig Smollin MD talk Associate Medical Director, California Poison Control Center, SF Assistant Professor of Emergency

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SLIDE 1

11/6/2013 1

Smoke inhalation

Craig Smollin MD

Associate Medical Director, California Poison Control Center, SF Assistant Professor of Emergency Medicine University of California, San Francisco

Disclosures

  • No financial relationship to any

commercial products discussed in this talk

  • Fires account for approx 3,250 U.S.

deaths/yr

  • Majority due to smoke inhalation
  • Associated with high morbidity and

mortality

Smoke Inhalation

Station night club fire Rhode Island February 20, 2003 100 killed 230 injured

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SLIDE 2

11/6/2013 2

Kiss nightclub fire Jan, 2013 233 killed Many from smoke inhalation

Case Study

  • 40-year old male pulled from an enclosed fire.

He is confused and agitated. He arrives in your emergency department disoriented and in moderate distress, coughing up soot and complaining of difficulty breathing.

  • VS: BP 90/60, HR 120, RR 30, O2 sat 95%

From http://lifeinthefastlane.com/

What type of injuries do you expect?

  • Thermal burns to the upper airway
  • Chemical injury to the upper airway
  • Chemical injury to the lower airway
  • Systemic affects of absorbed poisons
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SLIDE 3

11/6/2013 3 Objectives for this talk

  • We will focus on the systemic toxicity of

inhaled toxic gases

  • Carbon Monoxide
  • Cyanide

Carbon monoxide (CO)

  • Colorless, odorless, non-irritant gas
  • Produced anytime a carbon-

containing substance is burned

  • House fires, leaking furnaces,

portable generators

Carbon monoxide (CO)

  • Common serious poisoning
  • 15,000 - 40,000 cases/year in U.S
  • Over 2,000 deaths
  • High incidence of permanent

neurologic sequelae

CO Pathophysiology

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SLIDE 4

11/6/2013 4

Hemoglobin Oxygen Carbon Monoxide CO-Hgb

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11/6/2013 5

  • 1. Functional Anemia
  • 2. Shift in Oxygen Hgb

Dissociation Curve

40 80 120 50 100

Oxygen Partial Pressure (mmHg) Percent Saturation Hgb

40 80 120 50 100

Oxygen Partial Pressure (mmHg) Percent Saturation Hgb alveoli

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11/6/2013 6

40 80 120 50 100

Oxygen Partial Pressure (mmHg) Percent Saturation Hgb alveoli tissues

40 80 120 50 100

Oxygen Partial Pressure (mmHg) Percent Saturation Hgb alveoli tissues

40 80 120 50 100

Oxygen Partial Pressure (mmHg) Percent Saturation Hgb alveoli tissues

40 80 120 50 100

Oxygen Partial Pressure (mmHg) Percent Saturation Hgb alveoli tissues

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SLIDE 7

11/6/2013 7

40 80 120 50 100

Oxygen Partial Pressure (mmHg) Percent Saturation Hgb alveoli tissues

CO Pathophysiology

  • Binds to hemoglobin
  • 250:1 compared wtih O2
  • Functional anemia
  • Changes hemoglobin such that it

wont give up oxygen

CO Pathophysiology

  • Binds to hemoglobin
  • 250:1 compared wtih O2
  • Functional anemia
  • Shifts O2-Hemoglobin dissociation

curve to left

  • Other toxic effects
  • Intracellular myoglobin?
  • Intracellular cytochrome?
  • Post anoxic inflammatory injury

Symptoms and Signs

  • Nonspecific
  • Headache
  • Dizziness
  • Malaise
  • Nausea and vomiting
  • Confusion
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SLIDE 8

11/6/2013 8

Pitfall

  • The diagnosis of carbon monoxide

poisoning is easily overlooked!

Clues to the diagnosis

Cherry-red color Multiple victims Pulse oximetry? ABGs?

Pulse oximetry

Pitfall - Pulse oximetry reading will be normal in CO poisoning

Arterial blood gas

Pitfall - pO2 by arterial blood gas will be normal in CO poisoning

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SLIDE 9

11/6/2013 9 Traditionally CO only measurable through CO-oximetry

Pearl

CO-oximetry can be performed on either venous

  • r arterial blood samples

Clues to the diagnosis

Cherry-red color Multiple victims Pulse oximetry? ABGs?

Pearl

You must have a high index of suspicion and send a CO-Hgb level by CO-oximetry

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SLIDE 10

11/6/2013 10

Carboxyhemoglobin levels

COHgb %

< 5% 10-20% 30-40% 40-50% 50-60%

Symptoms*

None, or mild headache Headache, dyspnea on exertion Severe headache, fatigue, irritability, dizziness Confusion, collapse Coma, convulsions

*Note: correlation between COHgb levels and symptoms is poor

Outcome after CO Poisoning

  • Survivors of severe poisoning may have

permanent “hard” sequelae.

  • Vegetative state
  • Parkinsonism
  • Survivors of severe poisoning may have

permanent “hard” sequelae.

  • Vegetative state
  • Parkinsonism
  • Subtle cognitive deficits
  • Memory impairment
  • Irritability
  • Moodiness
  • Difficulty concentrating

Outcome after CO Poisoning

Case Continued...

  • Laboratory Data:
  • VBG: pH 6.8, pO2 = 75,
  • Lactate = 16 mmol/L
  • COHgb = 20%
  • CXR negative
  • Head CT negative
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11/6/2013 11

Pitfall

  • Tendency to focus on CO as the diagnosis

San Francisco 1906 - Great Earthquake and Fire

Question: are there any other systemic toxins found in smoke?

Consider this…

  • Hydrogen cyanide gas produced in combustion of :

Consider this…

  • Hydrogen cyanide gas produced in combustion of :
  • Probability of HCN production/exposure is high

Paper Silk Wool Plastic Cotton

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SLIDE 12

11/6/2013 12

Pitfall

Dont forget about Cyanide !! Patients exposed to carbon monoxide are likely to be exposed to cyanide

Cyanide: Pathophysiology

Electron Transport Chain

Mitochondrial Matrix

Electron Transport Chain

NADH

e-

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11/6/2013 13

Electron Transport Chain

NADH

e-

H+ H+ H+

Electron Transport Chain

NADH

H+ H+ H+

e-

Electron Transport Chain

NADH

H+ H+ H+

ADP ATP

Electron Transport Chain

NADH ADP ATP cytochrome aa3

CN

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11/6/2013 14

Electron Transport Chain

NADH ADP ATP cytochrome aa3

CN

Symptoms and Signs

  • Dizziness
  • Headache, nausea, vomiting
  • Dyspnea
  • Tachycardia, hypotension
  • Coma, seizures, death

Pitfall

  • Cyanide levels are not readily available!

Clinical clues to the diagnosis

Lactic Acidosis Elevated mixed venous pO2 Cardiovascular collapse

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11/6/2013 15

Pearl

Consider CN toxicity in the smoke inhalation patient with lactate > 10

Case Continued...

Our patient likely exposed to both CO and CN!

Laboratory Data: VBG: pH 6.8, pO2 = 75, Lactate = 16 mmol/L COHgb = 20% CXR negative HCT negative

Treatment

Which of the following treatments should be rendered to our patient?

  • (A) Nitrites
  • (B) Sodium thiosulfate
  • (C) Hydroxocobalamin
  • (D) Hyperbaric oxygen therapy
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SLIDE 16

11/6/2013 16 Treatment of CN Poisoning

  • Removal from source
  • 100% oxygen by tight-fitting mask/ET

tube

  • Cyanide antidote kit?
  • Hydroxocobalamin?

Cyanide Antidote Kit Cyanide Antidote Kit Nitrites

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11/6/2013 17

Nitrites Nitrites Nitrites

Problem: (1) Hypotension (2) Methemoglobinemia

Pitfall

  • Administration
  • f

nitrites to the patient with concurrent CO and CN poisoning

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11/6/2013 18

Cyanide Antidote Kit Sodium thiosulfate Sodium thiosulfate Hydroxocobolamin

  • Combines with CN to form

Vitamin B12.

  • Appears to be effective and safe
  • Preferred drug for CN due to

smoke inhalation (safer than nitrites)

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11/6/2013 19

73

Hydroxocobolamin

  • Side effects:

– Red Skin, secretions 2-7 days – Nausea, vomiting – Occasional HTN and muscle twitching

from Clin Toxicol 2006; 14.17

Treatment of CO Poisoning

  • Removal from source
  • 100% oxygen by tight-fitting mask/ET

tube

  • Hyperbaric oxygen?

Oxygen Treatment Approx T1/2 of COHgb ¥ Room air 5-6 hrs ¥ 100% Oxygen 45-90 min ¥ Hyperbaric oxygen 20-30 min

Hyperbaric oxygen

  • Speedier removal of CO
  • Provides oxygen independent of Hgb
  • Benefit to the injured brain?
  • About 1500 patients treated/year in

U.S.

  • Million dollar question:
  • Does HBO therapy reduce the

incidence of subtle cognitive deficits?

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11/6/2013 20

Multiplace chamber - Jacobi Hospital NY Multiplace chamber - Jacobi Hospital NY Monoplace chamber Monoplace chamber

Weighing the Evidence: HBO vs NBO

YES NO

Thom et. al. Weaver et al. Raphael et. al Scheinkestel et. al.

YES NO

Thom et. al. Weaver et al. Raphael et. al Scheinkestel et. al.

?

Naturally, experts disagree on interpretation!

Weighing the Evidence: HBO vs NBO

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SLIDE 21

11/6/2013 21 Consider HBO if:

  • Loss of consciousness (1,2)
  • COHbg > 25% (1,2)
  • Age > 36 yrs (1)
  • Metabolic acidosis
  • Cerebellar findings on Exam (2)

(1) Weaver et al: Am J Resp Crit Care Med 2008; 178:314 (2) Weaver et al: NEJM 2002; 347:1057

  • Also, pregnancy (fetus more at risk)

Which of the following treatments should be rendered to our patient?

  • (A) Nitrites
  • (B) Sodium thiosulfate
  • (C) Hydroxocobalamin
  • (D) Hyperbaric oxygen therapy

Which of the following treatments should be rendered to our patient?

  • (A) Nitrites (no)
  • (B) Sodium thiosulfate (maybe)
  • (C) Hydroxocobalamin (probably better)
  • (D) Hyperbaric oxygen therapy (consider)

Case Conclusion...

Patient intubated and placed on 100% oxygen. Received hydroxocobalamin for presumed CN exposure (lactate >10 mmol/L). HBO was considered but decided against because nearest chamber was at great distance and patient unstable.

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SLIDE 22

11/6/2013 22 Take home points

  • Carbon monoxide
  • Nonspecific symptoms
  • pO2 and conventional pulse ox

normal

  • Treat with oxygen
  • Consider HBO

Take home points

  • Cyanide
  • Often accompanies CO in smoke

inhalation

  • Elevated lactate and mixed venous

pO2

  • Avoid nitrites in smoke inhalation

victims

  • New antidote: hydroxocobalamin

Questions?