ANAESTHETIC ANAESTHETIC CONSIDERATION IN CONSIDERATION IN

ALTERED ENVIRONMENTALTERED ENVIRONMENT

INTRODUCTIONINTRODUCTION

Hyperbaric oxygen therapy means in a Hyperbaric oxygen therapy means in a pressurized chamber patient is exposed to pressurized chamber patient is exposed to oxygen tensions exceeding the ambient oxygen tensions exceeding the ambient barometric pressure(>760 mm Hg at sea barometric pressure(>760 mm Hg at sea level).level).

Until 20Until 20thth century hyperbaric treatment century hyperbaric treatment involved the use of air. clinical application involved the use of air. clinical application of hyperbaric oxygen therapy (HBO) began of hyperbaric oxygen therapy (HBO) began in late 1950s,in parallel to increase in late 1950s,in parallel to increase understanding of blood gas analysis and gas understanding of blood gas analysis and gas exchange physiology.exchange physiology.

PHYSIOLOGICAL EFFECT OF PHYSIOLOGICAL EFFECT OF INCREASED GAS PRESSUREINCREASED GAS PRESSURE

Increased barometric pressureIncreased barometric pressure Increased partial pressure of oxygen.Increased partial pressure of oxygen. It shows four pharmacological effectsIt shows four pharmacological effects1.1. Increased oxygen content of blood.Increased oxygen content of blood.2.2. VasoconstrictionVasoconstriction3.3. Antibacterial actionAntibacterial action4.4. Inhibition of endothelial leucocytic adhesions in Inhibition of endothelial leucocytic adhesions in

injured tissueinjured tissue Elevation of inert gas pressureElevation of inert gas pressure

CONTD….CONTD….

Elevation of absolute pressure during compression phase of Elevation of absolute pressure during compression phase of deep diving.deep diving.

Pressure reversal of anesthesiaPressure reversal of anesthesia

Animal studies have shown that high pressure (50ATA) has a Animal studies have shown that high pressure (50ATA) has a tendency to reverse general anesthesia.tendency to reverse general anesthesia.

Effect of hyper baric exposure on drug dispositionEffect of hyper baric exposure on drug disposition

Major pharmacokinetic or pharmacodynamic differences Major pharmacokinetic or pharmacodynamic differences wont be expected for most drugs up to the pressure used for wont be expected for most drugs up to the pressure used for most clinical purposes (6 ATA).most clinical purposes (6 ATA).

Indication of HBO therapyIndication of HBO therapy

1.1. Gas bubble diseaseGas bubble disease

2.2. PoisoningPoisoning

3.3. InfectionInfection

4.4. Acute ischemiaAcute ischemia

5.5. Chronic ischemiaChronic ischemia

6.6. Acute hypoxiaAcute hypoxia

7.7. Thermal injuryThermal injury

8.8. EnvenomationEnvenomation

RATIONAL FOR TREATMENT OF RATIONAL FOR TREATMENT OF SPECIFIC SYNDROMESSPECIFIC SYNDROMES

CO POISONING:CO POISONING: Pathophysiology:Pathophysiology: Functional anaemia Functional anaemia Shift of O-D curve to leftShift of O-D curve to left Binding with intracellular pigments.Binding with intracellular pigments. DiagnosisDiagnosis:: H/o exposure H/o exposure Carboxy Hb level in bloodCarboxy Hb level in blood Brain imagingBrain imaging

CO POISONINGCO POISONING

Role of HBO therapy – guidelines Role of HBO therapy – guidelines

1.1. H/o neurological impairmentH/o neurological impairment

2.2. Evidence of cardiac abnormalitiesEvidence of cardiac abnormalities

3.3. Carboxy Hb >25%Carboxy Hb >25%

4.4. Pregnant woman who fulfills the above criteriaPregnant woman who fulfills the above criteria Mechanism:Mechanism:

1.1. Half life of carboxy Hb is greatly reduced Half life of carboxy Hb is greatly reduced

2.2. Increased dissolved oxygen in plasmaIncreased dissolved oxygen in plasma

GAS EMBOLISM AND DECOMPRESSION GAS EMBOLISM AND DECOMPRESSION SICKNESSSICKNESS

Etiopathogenesis:Etiopathogenesis:1.1. Scuba divers during ascent from a dive while Scuba divers during ascent from a dive while

breathing compressed gas.breathing compressed gas.2.2. Iatrogenic causes like diagnostic Iatrogenic causes like diagnostic

arteriogram,heamodialysis,neurosurgical arteriogram,heamodialysis,neurosurgical procedures, total hip replacement,arthroscopy.procedures, total hip replacement,arthroscopy.

Effects :Effects :1.1. Obstruction of vesselsObstruction of vessels2.2. Bubble endothelial interactionBubble endothelial interaction3.3. Cerebral microcirculation impaired vaso regulationCerebral microcirculation impaired vaso regulation

CONTD….CONTD….

Decompression sicknessDecompression sickness

The gas bubbles in this situation occur because of a The gas bubbles in this situation occur because of a

decrease in ambient pressure at a rate sufficient to decrease in ambient pressure at a rate sufficient to induce local inert gas super saturation and induce local inert gas super saturation and subsequent formation of bubble insitu.subsequent formation of bubble insitu.

The decision to administer recompression treatment The decision to administer recompression treatment should be based on clinical evaluation.should be based on clinical evaluation.

TREATMENT:TREATMENT:

1.1. Fluid resuscitationFluid resuscitation

CONTD….CONTD….

2.2. High inspired oxygen concentrationHigh inspired oxygen concentration

3.3. HBO therapy will cause diminution of gas volumeHBO therapy will cause diminution of gas volume ACUTE INFECTION:ACUTE INFECTION: Clostridial myonecrosis Clostridial myonecrosis

1.1. Etiological agent – C.perfringensEtiological agent – C.perfringens

2.2. ManifestationManifestation

3.3. Treatment - surgical debridement, antibiotics , Treatment - surgical debridement, antibiotics , HBO therapy HBO therapy

SUPPORT OF ARTERIAL OXYGENATIONSUPPORT OF ARTERIAL OXYGENATION

In cases of cyanotic heart diseaseIn cases of cyanotic heart disease In Open heart surgery with the advantage of reduction In Open heart surgery with the advantage of reduction

in transfusion requirementsin transfusion requirements During therapeutic lung lavage performed under GA During therapeutic lung lavage performed under GA

with one lung ventilation.with one lung ventilation.

MAINTENANCE OF OMAINTENANCE OF O2 2 TRANSPORT IN TRANSPORT IN

SEVERE ANAEMIASEVERE ANAEMIA

Ability of hyperbaric oxygen to increase arterial Ability of hyperbaric oxygen to increase arterial content of oxygen in plasma to clinically useful level content of oxygen in plasma to clinically useful level may allow support of tissue oxygen delivery even in may allow support of tissue oxygen delivery even in absence of Hb temporarily pending the availability of absence of Hb temporarily pending the availability of definitive therapy in the form of cross matched blooddefinitive therapy in the form of cross matched blood

THERAPEUTIC SYSTEMSTHERAPEUTIC SYSTEMS

Multiplace chamber – Multiplace chamber – 1.1. These chamber are compressed with air and patient These chamber are compressed with air and patient

breathes oxygen with a head tent.breathes oxygen with a head tent.2.2. Monitoring is relatively easy.Monitoring is relatively easy.3.3. Expensive and large space needed.Expensive and large space needed. Monoplace chamber –Monoplace chamber –1.1. Compressed with 100% oxygen.Compressed with 100% oxygen.2.2. Low cost and easy installation.Low cost and easy installation.3.3. Monitoring and emergency care difficultMonitoring and emergency care difficult

MULTI PLACE CHAMBERMULTI PLACE CHAMBER

MONOPLACE CHAMBERMONOPLACE CHAMBER

HYPERBARIC TREATMENT SCHEDULEHYPERBARIC TREATMENT SCHEDULE

Factors limiting dose and duration of HBO therapyFactors limiting dose and duration of HBO therapy Oxygen toxicity, decompression obligation for nursing staff, Oxygen toxicity, decompression obligation for nursing staff,

difficulty in monitoring, patient boredom.difficulty in monitoring, patient boredom. Gas embolism and Decompression sicknessGas embolism and Decompression sickness

1.1. U.S Navy Table 6 U.S Navy Table 6

2.2. U.S Navy Table 6AU.S Navy Table 6A Clostridial myonecrosis Clostridial myonecrosis

Duke therapeutic protocolDuke therapeutic protocol Osteoradio necrosisOsteoradio necrosis

THERAPEUTIC SCHEDULETHERAPEUTIC SCHEDULE

PATIENT EVALUATIONPATIENT EVALUATION

Whether a sufficient elevation in PaOWhether a sufficient elevation in PaO2 2 can be can be

obtained.obtained. Whether pt can equilibrate middle ear pressure.Whether pt can equilibrate middle ear pressure. Adequacy of control of seizure disorder.Adequacy of control of seizure disorder. Presence of pulmonary bullae or blebs.Presence of pulmonary bullae or blebs. Hyperoxic myopia.Hyperoxic myopia. Whether claustrophobia might occur during Whether claustrophobia might occur during

treatment.treatment.

REFERENCES:REFERENCES:

MILLER’S anesthesia 6MILLER’S anesthesia 6thth edition: edition: MORGAN’S clinical anesthesiology MORGAN’S clinical anesthesiology

44thth edition: edition: GUYTON and HALL physiology:GUYTON and HALL physiology: