HBOT Safety/Review Questions #3
You are treating a 6 year old MN feline who was referred immediately following a urinary obstruction episode.
Cystocentesis had been performed when the initial attending doctor was unsuccessful in passing a catheter, and the bladder had ruptured during that procedure. The cat was initially extremely azotemic and hyperkalemic, and at emergency surgery the bladder wall was very distended, bruised, edematous, and appeared atonic. A Foley catheter was placed during the bladder repair, and a few days later a pharyngostomy feeding tube was placed due to anorexia and liver biopsy results which revealed marked hepatic lipidosis.
You are using BID HBOT at 2 ATA as adjuvant therapy to enhance would healing. The cat is prepared for the sessions by wrapping the IV catheter and feeding tube in 100% cotton gauze. What special consideration must be undertaken (and why) when preparing the Foley catheter for the sessions?
ANSWER: The balloon cuff in the Foley catheter must be checked to see that it is filled with fluid, such as sterile water or saline, rather than air. This is another practical example of Boyle's Law. If the cuff is filled with air, when the patient is treated in the chamber, the cuff will collapse during compression, and the catheter may change position or dislodge as the patient moves (Reference, Bakker and Cramer et al, Hyperbaric Surgery Perioperative Care, Best Publishing, 2002, pages 128-129).
You are treating a 10 year old F/S canine patient for severe burns resulting from a brush fire.
The E/CC clinicians placed a central venous line this morning to aid them in monitoring CVP, obtaining multiple blood samples, and administering aggressive crystalloid and colloid fluid therapy. What diagnostic is necessary (and why) prior to HBOT based on the Criticalists' actions this morning?
Answer: The clinician should take chest radiographs following the placement of any central line, as there exists a chance that pneumothorax could follow as a mechanical complication of insertion. [Reference, Eisen LA, et al. Mechanical Complications of Central Venous Catheters, J Intensive Care Med, 2006 Jan-Feb;21(1):40-6]. Untreated pneumothorax is a contraindication for hyperbaric oxygen therapy. The clinician should consider chest radiographs on all patients to be given HBOT, especially with a history of trauma such as HBC, "high rise syndrome", or wounds secondary to a fight.
A 4 week old female Pug puppy is referred for treatment of severe purulent omphalophlebitis.
She has swollen joints, with suppurative cytology on joint fluid. Her temperature is 102.9 F. You suspect sepsis, and recommend HBOT in addition to parenteral antibiotic therapy.
The client is a pediatric neonatal ICU nurse at your local human hospital. She is determined to treat this puppy, but is concerned about "oxygen toxicity to the developing eyes" if adjuvant HBOT is employed.
What should you tell her?
ANSWER: This is an interesting issue. Her question likely comes from the belief that prolonged exposures in premature and newborn human infants to high concentration of oxygen at sea level pressure (normobaric, not hyperbaric) is a cause of blindness. The syndrome was called retrolental hyperplasia (now called retinopathy of prematurity). It was first noted in the 1950's in large numbers of premature human babies. When oxygen supplementation was restricted to less than 40% in premature infants the incidence promptly decreased. More recently physicians have questioned and debated the actual cause(s) for the syndrome, and whether oxygen restriction is advisable. (Reference: Editorial, Oxygen Restriction and Retinopathy of Prematurity. Lancet 1992, 339: 961-962). Others have actually advised intermittent oxygen in the treatment of this syndrome (Reference: Tanabe Y. Intermittent Oxygen for the Treatment of Retinopathy of Prematurity, Nippon Ganka Gakkai Zasshi, 1972 May 76:5 316-21).
In any event, most evidence suggests the continuous use of oxygen in perinatal patients modulates the incidence of this disease. However, intermittent hyperbaric oxygen therapy is, by definition, not continuous. HBOT has been employed in neonate humans since 1963 for a variety of conditions, including birth apnea, sepsis and hemolytic disease of the newborn, without development of retinopathy of the newborn (Reference: Jain, KK, Texbook of Hyperbaric Medicine, 5th Edition, Hofgrefe, 2009, page 424).
A 7 year old MN Greyhound is referred to you with leukocytosis, thrombocytopenia, fever, and increasing bilirubin.
He maintains a normal and steady PCV. You suspect sepsis. The fever is controlled with IV fluids and antibiotics. You want to add adjuvant HBOT. You review the thoracic radiographs (at right). Will you add HBOT?
Yes or no – and why?
ANSWER: No. The radiographs reveal pulmonary bullae. This patient is at risk for rupture of the bullae at pressure, and tension pneumothorax could subsequently develop while in the chamber. During decompression free air in thorax would actually further expand in volume, resulting in more serious pulmonary atelectasis. (References: Kindall, E.P., Whelan, H.T., Hyperbaric Medical Practice, Second Edition Revised, Best Publishing, 2004, Page 492: Steenblock, D.A., Hyperbaric Oxygen for Treatment of Stroke and Traumatic Brain Injuries, National Stroke Association Conference, Boston, MA, 1997).
You are consulting on a Great Dane post GDV surgery.
The attending surgeon informs you that the stomach tissue appeared poorly perfused even after decompression and gastropexy, and there are currently runs of VPC's on the ECG. Review of the history reveals that the patient recently underwent a "limb sparing" procedure, and is being treated by an oncologist with chemotherapy for osteosarcoma. The surgeon is inquiring about the potential benefits of a short course of HBOT as adjuvant therapy for the ischemia-reperfusion issues associated with the GDV. You check the current/recent medication list.
Which of the following is a relative contraindication for HBOT?
Omeprazole
Metaclopramide
Cis-platinum
Enrofloxacin
ANSWER: 3. Cis-platinum
This chemotherapeutic drug interferes with DNA synthesis, thus delaying fibroplast production and collagen generation. In a controlled study (in mice) wound breaking strength under the influence of both Cis-platinum and HBOT was adversely affected when compared to the control group of Cis-platinum alone (Nemiroff, P.R., "Effects of Cis-platinum and Hyperbaric Oxygen on Wound Healing in Mice", Undersea Biomedical Research (Supp: 40 1988: 15). Thus, the use of adjuvant HBOT may actually retard wound healing in this individual case.
An 8 year old canine has been referred for adjuvant HBOT in the management of non-healing foot wounds (of a six-year duration).
You obtain current blood tests, biopsies and cultures, and prepare to begin therapy. The owner presents the dog for its first session with an air-filled "inner-tube" type of Elizabethan collar to prevent licking at the wounds and self mutilation.
Please discuss the issue with this particular collar and HBOT.
ANSWER: This is another Boyle's Law example. As the pressure increases in the chamber, the air in the "inner tube" E-collar compresses and shrinks the size of the collar. It may slip off or re-position itself in an undesirable manner. Then, as the pressure decreases at the end of the session it will expand. If it has slipped into an unacceptable position it may cause the patient discomfort or anxiety. The "balloon" inside the tube could also burst under the influence of increased pressure during a session. It is best to replace this E-collar with a standard plastic E-collar if the protection of an E-collar is necessary during an HBOT session.