This case report describes our experience using HBOT in a patient who underwent cardiac surgery due to native-valve endocarditis infected with C. acnes and experienced a post-surgery ischemic stroke. Based on pathophysiological principles and our clinical experience, we believe that HBOT benefited our patient.
Possible mechanisms for the development of post-cardiac surgical strokes include atheromatous plaque fragments dislodged from the aorta during cross-clamping, decreased cerebral perfusion, and gas embolisms [6, 7, 13]. Cerebral edema and neuronal apoptosis follow the passage of air bubbles, inducing endothelial damage and an inflammatory response. This may lead to endothelial swelling, increased vascular resistance, leucocyte and platelet adherence, and damage to the blood-brain barrier. There is a major risk of significant air embolisms during procedures in which the left ventricle or aorta are opened, such as in valve replacement surgery , which could explain why our patient experienced a post-operative stroke. Similar Gibson et al , HBOT was administered for our patient in treating post-cardiac surgical stroke, basing on the reason that cerebral air embolism is the likely etiology theoretically and the nature of the operation the patient had received.
HBOT also has bactericidal and bacteriostatic effects on both aerobic and anaerobic bacteria . HBOT may have a direct antimicrobial effect, enhance the antimicrobial effects of the immune system, or work synergistically with certain antimicrobial agents . The culture from the patient tissue showed the presence of C. acnes, a gram-positive anaerobic bacillus that is ubiquitous in the skin flora. Banzon et al  reported that the most common antibiotics used for the treatment of C. acnes infection were vancomycin (59%) and ceftriaxone (25%). Furthermore, the use of beta-lactams (benzylpenicillin was the most frequently used) and the addition of rifampicin or aminoglycosides for cases of C. acnes endocarditis have been elucidated in previous studies . The antimicrobial therapy for C. acnes in combination with HBOT has not been previously addressed, and our case was the first to apply HBOT in this setting.
HBOT has proven effective adjunctive treatment in chronic Lyme disease, clostridial myonecrosis, necrotizing fasciitis, and refractory osteomyelitis [9, 17]. The antimicrobial effects of HBOT are believed to result from the formation of reactive oxygen species (ROS) , the reactive radicals that are continually produced as alternative metabolites of several cell biological pathways. HBOT promotes aerobic metabolism, leading to enhanced ROS production in bacteria. HBOT aims to induce the aerobic metabolism of bacteria and to reoxygenate the O2-depleted infectious tissues, thereby increasing the microbial susceptibility to antibiotics. In our patient, there was not enough evidence of IE preoperatively until the tissue culture was obtained. We believe that the debridement was not performed completely, and the bacteria were still present. Consequently, HBOT was considered an effective adjunctive therapeutic option in our case.
Finally, HBOT facilitates wound healing by inducing angiogenesis [18, 19] and suppressing interferon-γ and proinflammatory cytokines such as interleukin (IL)-1, IL-6, and tumor necrosis factor-α . HBOT induces partial high tension of oxygen in the circulating plasma and stimulates oxygen-dependent collagen matrix formation, an essential phase in wound healing . Our patient had undergone major open-heart surgery, including pericardiotomy and sternotomy, aortic valve replacement, tricuspid annuloplasty, mitral annuloplasty, and aortotomy. We believe that HBOT accelerated his wound healing and recovery, benefiting our patient enough for him to participate in rehabilitation programs within first month, which is considered the gold recovery phase after a stroke.
In conclusion, our patient demonstrated good recovery from ischemic stroke related to post-cardiac surgery due to IE infection by C. acnes despite a delay of one week before HBOT initiation. HBOT was effective as an adjunctive therapeutic option in our setting, However, evidence on when to apply HBOT and the number of intervention cycles for effective therapeutic outcomes requires further studies.