HBOT Safety/Review Questions
A 12-year-old Fes Schnauzer with a chronic history of Cushing's and diabetes mellitus is referred for adjuvant HBOT in the management of severe pancreatitis [which began shortly after she was observed eating garbage from the trash can].
At morning rounds you discussed pre-HBOT management in this patient. What adjustment do you have to make to this patient’s medications prior to an HBOT session?
ANSWER: Reduce the immediate pre-treatment insulin dosage by 33% of the usual dose.
The clinician should consider checking blood glucose measurements in Diabetics undergoing HBOT before and after treatment sessions to help decide how much the individual patient's blood glucose is affected by HBOT. In a study on human Diabetics, insulin dosages were reduced by significant amounts in over 60% of patients treated by HBOT. (Reference: Kakhnovski et al, Biochemical Indices in Diabetes Mellitus Patients Undergoing Hyperbaric Oxygenation. Sov Med 10: 33-37)
A 10 month old feline is being treated with HBOT for a non-healing axillary wound which had not responded to graft/flap surgery. The wound has been present for 7 months. Biopsies and cultures did not reveal etiologic agents (including Mycobacterium). The kitten has a short generalized seizure during HBOT at 2 ATA observed by the attending technician.
The technician should:
Press the Emergency Button and immediately/ rapidly decompress, then notify the attending doctor.
Initiate an immediate gradual decompression over 10-15 minutes to terminate the session, then contact the attending doctor.
Adjust the treatment pressure down to 1.5 ATA gradually, and promptly contact the attending doctor.
Notify the attending doctor, and begin to time the seizure. If the seizure is short (less than two minutes), start to reduce the pressure gradually down to 1.5 ATA.
ANSWER: 4.
Seizures are infrequently encountered during HBOT, and may be a sign of “oxygen toxicity”. They are usually short in duration, and without sequellae. They typically occur at a slightly greater frequency during higher ATA treatment pressures, such as 2.5 or 3 ATA. Most seizures observed in the chamber are short. If this is the case, wait until the seizure ends, then begin a gradual reduction in pressure to 1.5 ATA. Rapid decompression is NOT recommended as the expanding pulmonary gases during rapid decompression could theoretically rupture lung tissue during the tonic phase of the seizure. If the seizure ends quickly the treatment session may be completed at the reduced ATA if the patient appears stable. The attending doctor may consider giving future sessions at the reduced ATA, prescribing pre- treatment anticonvulsants such as benzodiazapines, or both.
Known epileptics or patients with CNS diseases at risk for seizures may receive HBOT, however the attending clinician should consider lower treatment pressures and/or pre-treatment anticonvulsants. [reference Kindwall, EP. Whelen HT, Hyperbaric Medicine Practice, Second Edition Revised, Best Publishing, 2004, page 77].
The attending doctor and technician should be aware that hypoglycemia may also occur in the chamber, and manifest as a seizure in some patients.
A 10-year-old canine was referred for possible adjuvant HBOT in the treatment of presumed pancreatitis. The patient is critically ill, and has multiple criteria supporting this diagnosis, including vomiting, lipemia, anterior abdominal pain, “strawberry milkshake” abdominal effusion with no evidence for infectious organisms, radiographic and ultrasonographic imaging typical for pancreatitis, and extremely elevated cPLI.
However, the patient has a history of malignant Mast Cell Tumor and is currently being treated with Palladia®.
The referring doctor asks you, “Is the presence of malignant neoplasia a contraindication for HBOT?” You answer:
Yes
No
ANSWER: 2. No
In light of HBOT's upregulation of Vasculogenesis, many clinicians express hypothetical concern that treating a cancer patient with HBOT will increase the rate of tumor growth or stimulate metastasis. This has NOT been observed in large numbers of humans treated with HBOT for radionecrosis (Reference, Kindwall, E.P. and Whelan, H.T., "Hyperbaric Medical Practice", Second Edition Revised, Best Publishing, 2004, pages 86-89)
A nude mice model implanted with human Squamous Cell Carcinoma showed no difference in tumor growth or metastasis between controls and HBOT treated subjects at six week follow up (Reference, Sklizovic, D. et al. "Hyperbaric Oxygen Therapy and Squamous Cell Carcinoma Growth", Head and Neck, 1993; 15 (3): 236-240)
A 3 year old pregnant female champion breeding bitch is presented to you on emergency with a fresh wound on the lower mandible and severe facial swelling. The owner witnessed a rattlesnake biting the dog as it sniffed around a large rock during a walk. The bitch is due to whelp in approximately two weeks. You want to use adjuvant HBOT in this patient, but are concerned about HBOT's effect on the feti, or premature closure of the fetal ductus arteriosi. Is HBOT contraindicated in pregnancy?
Yes
No
ANSWER: 2. No
There appears to be no established contraindication to treatment with HBOT in pregnancy. It takes prolonged exposure times, 12 consecutive hours or more, to result in closure of a ductus arteriosus. Likewise, the retrolental fibroplasia / retinopathy of neonatal humans associated with prolonged hyperoxemia has not been associated with the relatively short HBOT sessions.
Reviews of the human medical literature reported in Russia and the US have resulted in recommendations that HBOT can be used in pregnant females without harm to the fetuses or mothers [references Pobendinsky, NM et al “Hyperbaric Oxygen in the Treatment of Reproductive Function of Women” Proceedings of the Seventh International Congress on Hyperbaric Medicine. Van Hoesen, KB et al, “Should hyperbaric oxygen be used to treat the pregnant patient for acute carbon monoxide poisoning?" JAMA. 1989; 261[7]: 1039-1043]
Which of the following is allowed to be included with a feline patient inside the chamber or treatment module during an HBOT session?
A cell phone on speaker mode so the owner can speak to the cat during the treatment
A stuffed toy which jumps up and down when batted by the cat
An Ipod music player with speakers
A 100% cotton garment recently worn by the owner
ANSWER: 4. A 100% cotton garment recently worn by the owner. 100% cotton is allowed in the chamber. Electronic, battery operated, or wind-up devices would be a combustion hazard, and are not permitted in the chamber.
A veterinary hyperbaric technician is monitoring a canine patient being treated for Immune Mediated Hemolytic Anemia [IMHA] in a monoplace chamber. Which one of these situations calls for an early end to the treatment session?
The hair on the patients ears and nose is beginning to stand straight up and out.
The patient is licking repeatedly at his forepaws.
The cotton bandage on his paw is starting to unravel.
The patient vomits his morning meal.
ANSWER: 1. This rare situation of excessive static formation requires standard, gradual decompression and an early end to the session, as static buildup could lead to a spark, with increased risk of combustion. Static buildup can be minimized by gently wiping down the haircoat of the patient with a moistened, 100% cotton towel prior to the session.
Treatment with HBOT is valuable in IMHA, as it allows delivery of oxygen to systemically hypoxic tissues, and helps rapidly lower carbon monoxide (CO) levels, which are a by-product of Heme Catabolism. This endogenously produced CO binds to remaining RBCS, causing reduction in RBC deformability, and shifts the oxygen dissociation curve to the left. CO induces increased platelet aggregation. In addition, CO combines with myoglobin, cytochrome c-oxidase and cytochrome P-450, which may inhibit the mitochondrial respiratory chain. An evidence-based approach review of peer reviewed publications concluded that all articles reported a positive result when HBOT is given for treatment of severe anemia in humans.
Van Meter KW, Undersea Hyperb Med 2005 Jan-Feb; 32 (1) 61-83
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