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Rodent study shows that chronic drinking can lead to severe pneumonia after surgery

February 04, 2008

Rodent study shows that chronic drinking can lead to severe pneumonia after surgery

* Consistent alcohol consumption can impair immunity functions following surgery.
* A new rodent study has found that chronic drinking can result in a severe form of pneumonia following surgery.
* Study authors recommend that patients considering surgery control their drinking habits, and also be very honest with their doctors about their drinking habits, prior to surgery.

People who drink often have immune-function problems following surgery. For example, patients who consume alcohol long-term have a two- to five-fold greater chance of post-operation infection complications. A new rodent study has found that chronic consumption - in this case, the equivalent of prolonged moderate drinking - can result in a more severe form of pneumonia following surgery.

Results are published in the February issue of Alcoholism: Clinical & Experimental Research.

Surgery can be scheduled or the result of an accident, said Claudia Spies, medical associate director of the department of anesthesiology and intensive care medicine at the University Hospital Charité, Universitaetsmedizin Berlin. In either case, complications can arise because of prior alcohol consumption.

"A significantly high rate of complications can develop in patients who consume alcohol at levels that are less than excessive," Spies explained. "Some 20 percent of the adult population admitted to a general hospital drinks three beers or two glasses of wine on a daily basis for a prolonged period. These patients can exhibit a higher rate of pneumonia after surgery, a higher rate of cardiomyopathy or heart muscle disease, a higher rate of confusion post surgery, and significant increased bleeding complications. In addition, some 50 percent of patients who are committed to hospitals after an accident suffered their injuries under the influence of alcohol. Consequently, the rate of immune-system complications in emergency medicine is also very high."

"More alcohol abusers die of pulmonary infections than liver cirrhosis," added Elizabeth J. Kovacs, director of the Alcohol Research Program at Loyola University Medical Center. "Although a good deal of clinical and experimental evidence suggests that chronic alcohol exposure is detrimental to the health of the subject, only recently has it been suggested that acute alcohol exposure has comparable effects on immune responses to an infectious challenge. By acute alcohol exposure, I mean a single exposure at binge levels - greater than four drinks in a female or greater than five drinks in a male - or multi-day binge drinking."

For this study, researchers gave 32 female mice either alcohol (3.8 mg/kg body weight) or saline for eight days. On the eighth day, all mice underwent abdominal surgery. On the 10th day, the mice were nasally exposed to either K. pneumoniae or saline (referred to as "sham infection"). This led to four groups: alcohol/infection, alcohol/sham infection, saline/infection, saline/sham infection. Two days later, the mice were euthanized: their lungs, spleen and liver were extracted for assessment, and levels of cytokines interleukin-6 (IL-6) and IL-10 were measured.

IL-6 is a pro-inflammatory cytokine, meaning it initiates or perpetuates an inflammatory response, seen after an overwhelming infection. IL-10 is an anti-inflammatory cytokine, activated in order to turn off the pro-inflammatory response. If the inflammation is not turned off, tissue damage can result.

Results showed worse clinical outcomes among the alcohol-exposed mice than the saline-exposed mice. More specifically, they had greater tissue destruction and higher levels of both IL-6 and IL-10, which indicates a severe pulmonary infection with K. pneumoniae.

"Apparently the immune system of the alcohol-exposed mice tried in vain to fight off the infection and produced excessive amounts of IL-6 and IL-10 in the process," said Spies. "The pneumonia was also more severe in the alcohol-exposed mice than in the animals that had only been exposed to the bacteria but not to the alcohol."

"These data are consistent with other observations showing that alcohol impairs immunity after infection," said Kovacs. "The observation that cytokines are produced at higher levels in the lung following the combined insult of alcohol exposure and infection suggest that the return to homeostasis or normality may be delayed in this group of subjects."

"These same high levels of the mediators, interleukin 6 and 10, have been seen in patients with severe pneumonia," added Spies. "We know already that patients with particularly nasty pneumonias are often medium to high alcohol users. Patients who are considering surgery should definitely control their drinking habits in advance."

Kovacs wholeheartedly concurred: "Don't drink in excess before surgery, after surgery, or for that matter ever," she said.

"Furthermore," said Spies, "individuals should - in addition to monitoring their alcohol habits with a view to surgery - be honest about the level of their drinking when asked by a doctor. The information could be potentially lifesaving, because knowing about the elevated risk, the anaesthetist and the surgeon can take precautions. And doctors should make it a rule to question each and every patient about their drinking habits. That means they should not only ask them if they drink, but also specifically what amounts per day."

Alcoholism: Clinical & Experimental Research