Oxygen IS a drug, use it with caution, only when is needed.

This is a quick review on the potentially harmful effects of too much oxygen, published in this month's EPM magazine. 

THE POTENTIAL HARM OF OXYGEN THERAPY IN MEDICAL EMERGENCIES
Cornet, A.D., et al, Crit Care 17(2):313, April 18, 2013
These Dutch authors comment on possible harm from routine use of supplemental oxygen in patients with a medical emergency. Several early studies reported high-flow oxygen in myocardial infarction patients was associated with reduced cardiac output and stroke volume with an increase in systemic vascular resistance and arterial blood pressure, largely due to vasoconstriction, with no evidence of a benefit of hyperoxia on myocardial ischemia. Clinical trials of supplemental oxygen in patients with cardiac emergencies are limited, but a 2010 Cochrane review reported increased mortality in MI patients receiving supplemental oxygen (RR 3.0). Experimental evidence also suggests an adverse hemodynamic effect of oxygen in patients with congestive heart failure. The adverse effects of supplemental oxygen are more widely appreciated in patients with chronic obstructive pulmonary disease (COPD), and a recent randomized trial noted decreased mortality in COPD patients receiving titrated rather than high-concentration oxygen. 

Hyperoxia in stroke has been noted to be associated with a decrease in cerebral blood flow and increased mortality, and use of supplemental oxygen for most ischemic stroke patients is not supported in American Stroke Association guidelines. Several large studies reported increased mortality and poor neurologic outcomes in hyperoxic patients after resuscitation from cardiac arrest. Although it is possible that vasoconstriction due to hyperoxia might be beneficial in patients with shock, no studies have demonstrated a benefit of supranormal oxygen levels in this setting. The authors advise caution with the routine use of supplemental oxygen for medical emergencies. While hypoxemia should be treated promptly, they recommend slow stepwise titration and feel that an oxygen saturation of 90-94% may be reasonable. 61 references (cornet@vumc.nl – no reprints)

Conclusions:
- Oxygen IS toxic when used in high concentrations and for prolonged periods of time.
- Hyperoxia causes cellular dysfunction 
- Use it only when patient is hypoxic and when hypoxia has been corrected, titrate down to maintain normoxia.
- Share the knowledge and stop the ritual of putting every patient on oxygen !

Emergency Contraception.. the only "REAL" emergency!

You: Hi.. I am Dr X, what can I do for you today?

Patient: Uhhh... my boyfriend and I were... uhhh, you know... (silence)

You: Yes...

Patient: My boyfriend and I were having sex and... (silence)

You: Uh-hu....

Patient: You know, he didn't pull out on time. (in soft voice)

Boyfriend: I told you do move, but you didn't move! (Obviously angry)

Patient: Shut up! Do you think I want to be here?

You: It's OK, no need to argue. You want to make sure you don't get pregnant, correct?

Patient: YES !! That's right doc. You gotta help me. I am going to school, work 2 jobs, my mom is going to kill me and .... and....

You get the idea!

Emergency contraception is one of those issues that sound simple, but it is not. Matching the right method to the right patient requires some understanding of the pharmacology of these agents and also knowing more about your patient's history. Here is a review from this months, NEJM. Enjoy!

Oral emergency contraceptive pills are the most commonly used form of emergency contraception. Two regimens are currently marketed in the United States: ulipristal acetate (30 mg) and levonorgestrel (1.5 mg). In 39 clinical trials that included a combined total of more than 18,000 women, rates of pregnancy after use of one of these two regimens ranged from 0 to 6.5%. Interpretation of these numbers is problematic because the likelihood of pregnancy in the absence of emergency contraception was not directly assessed; estimates that were based on the days of the menstrual cycle on which the participants had sex suggest that use of each of these regimens reduces the risk of pregnancy after a single sex act by 40 to 90%. In the United States, products containing 1.5 mg of levonorgestrel in one tablet may legally be sold over the counter to women and men of all ages. Although the ulipristal regimen was recently approved for nonprescription sale in Europe, it still requires a prescription in the United States; consequently, use of this regimen in the United States is limited. Some but not all data suggest reduced efficacy of the levonorgestrel regimen in obese women with BMI’s as low as 25. If you think about it, it is not that much!

The levonorgestrel regimen is effective for at least 4 or 5 days after sex but may be more effective the sooner it is taken; data on the ulipristal regimen have not indicated a decrease in efficacy through 120 hours after sex. However, since both regimens work largely by delaying or inhibiting ovulation, and since women are usually unaware of whether ovulation is imminent, prompt use is prudent. Neither of these two oral emergency contraceptive regimens has any recognized contraindications.

The most effective form of emergency contraception is the copper IUD. A review of 42 studies showed that, of 7034 women who received IUDs up to 10 days after unprotected sex, only 0.09% subsequently became pregnant. Recent analyses suggest that the IUD is effective for emergency contraception throughout the menstrual cycle and can be inserted at any point if pregnancy is ruled out. A key advantage of the IUD over oral emergency contraceptive pills is that the IUD can provide ongoing contraception for at least 10 years. Almost all women can safely use an IUD for emergency contraception; the only recognized contraindications are pregnancy, cancer of the genital tract, uterine malformation preventing device placement, copper allergy, mucopurulent cervicitis, current pelvic inflammatory disease, and known current cervical infection with chlamydia or gonorrhea. These conditions can be reasonably ruled out on the basis of interview, examination, and, if indicated, pregnancy test; routine testing for cervical infection is not necessary.

No deaths or serious complications have been causally linked to either oral emergency contraception regimen. Previous studies over the past decades have not revealed adverse effects of levonorgestrel exposure during pregnancy on either the woman or the conceptus. Data on ulipristal exposure during pregnancy are limited, but combined data from postmarketing surveillance and clinical trials showed that among 232 pregnancies with a known outcome in which the woman and conceptus were exposed to ulipristal, no teratogenic effects were seen. The incidence of pelvic inflammatory disease after IUD insertion is less than 5% even when the device is inserted through an infected cervix; whether IUD insertion itself increases this incidence has not been definitively established. IUD insertion can be uncomfortable, and some women have vaginal bleeding and cramping after insertion. In the one published study of IUD insertion for emergency contraception, which was conducted in community clinics, the IUD insertion attempt was unsuccessful in 18% of women; this proportion is higher than that reported in clinical trials of IUD insertion for routine contraception.

Key points:

- IDU is the king of emergency contraception. However, not for all women.

- Oral hormonal options, mainly levonogestrel and ulipristal, have failure rates that vary from 0-6%.

- Women with higher BMI's are at risk for failure of the oral forms.

- The sooner you take them, the better.

- It is good to have a plan C and D, when B doesn't work.