Blood Lactate Levels measurement during Open-Heart Surgery in Opium Addiction Patients

It is an established fact that tissue hypo perfusion is associated with lactate acidosis secondary to anaerobic metabolism. Many factors affect on blood lactate levels & type of cellular metabolism. Cardiopulmonary by-pass (CPB) is widely used to maintain systemic perfusion and oxygenation during open-heart surgery. Tissue hypo perfusion with resultant lactate acidosis during CPB may occur by hypothermia, extreme haemodilution, low flow CPB and excessive neuro-hormonal activation. The duration of CPB, body temperature, haematocrit value, patient s hemodynamic, all contribute to tissue hypo perfusion. Blood lactate level is a good marker for tissue hypo perfusion. Therefore, it is very important to detect and manage tissue hypo perfusion during Open-Heart Surgery.
Material & 50 patients undergoing open-heart surgery that had history of using opium more than 5 years included in this study. Blood lactate levels measured immediately before and after induction of anesthesia, tracheal intubation, 15, 45 minutes after institution of CPB, immediately after termination the CPB and 24 hours post-surgery. Mean arterial pressure was continuously monitored and maintained between 50 & 60 mm Hg. The haemoglobin was monitored and maintained between 6 & 8 gm/dl. Blood sugars levels were monitored and maintained between 110 to 180 mg/dl. The anesthesia protocols were similar for all patients.
The mean lactate levels were (1.08 ± 0.36) before induction of anesthesia, (1.02±0.52) after induction of anesthesia and tracheal intubation. The mean blood lactate levels at 15, 45 minutes after institution of CPB, immediately off-bypass, 24 hours post-surgery were (2.13± 0.77), (2.73±1.43), (2.73±1.43), (3.22±1.43), (2.79±1.43), respectively. There were a statistically significant differences between mean lactate levels after induction and tracheal intubation with other times of measuring blood lactate levels.(P= 0.0001) while blood lactate levels before and after induction did not have any statistically significant difference. All patients divided in two groups, less and more than 2 hours duration of CPB times. Mean blood lactate levels compared in between them. The mean blood lactate levels after intubation, immediately off-pump, 24 hours post-surgery had a statistically significant difference.(P=0.043, P=0.009, P=0.027) But there were not any statistically significant difference between two groups at 15, 45 minutes after institution of CPB.
A progressive increase in the mean lactate levels was seen after institution of CPB and blood lactate levels decreased 24 hours post-surgery. Duration of CPB time more than 2 hours increased blood lactate levels. There was no any difference between blood lactate levels before and after induction of anesthesia.