Do no harm?

If you do something in good faith that it might help make someone better but they die as a result, is it manslaughter?
Last night at the end of my on call I was called to an HIV positive male, with active pulmonary TB who was fitting. He was unconcious and seemed to be having a one sided seizure. We gave him some medicine to stop this but needed to figure out why it had happened. The commonest causes out here are bacterial meningitis, TB meningitis, cryptococcal and toxoplasmosis (all basically infections of the brain, but all treated with different medicines). The best way to determine the cause is to take some fluid from around the spinal cord (a lumbar puncture) and test it. However this can be dangerous as there is a risk of causing 'coning' which is where the brain comes down through the skull and the patient dies. Various things suggest that you are more at risk of this, including focal neurology. In the UK you would hardly ever do an LP on this sort of patient without first doing a CT scan of the brain. If you had to, you would look at the back of their eyes first as this can also give you a clue. But 'urgent' CTs out here take days to weeks to happen and there is no opthalmoscope in the hospital. So general consensus is that you do more good by doing the LP and starting treatment. However, last night's patient died just hours after I had done the LP (which confirmed that he had TB meningitis and was therefore already on the correct treatment). With no post-mortem, we will never know for sure the cause of his death but given the timing, you have to be suspicious that it was a direct result of my actions.
Death is a daily occurence out here, but today is the first time that I have felt that it was truly at my hands.