The Lack of Effect of Routine Magnesium Administration on Respiratory Function in Mechanically Ventilated Patients: Results
We completed 21 separate studies on a total of 20 patients admitted to our ICU. One patient was included twice for two separate episodes of respiratory failure. The average age was 59 years (range, 22 to 84 years) and there were 14 men and 6 women. The admitting diagnoses to ICU were as follows: eight chronic obstructive pulmonary disease in exacerbation, four postoperative (bowel obstruction, motor vehicle accident, coronary artery bypass, and biliary peritonitis), three pneumonia, two sepsis, and one each of the myeloblastic leukemia, idiopathic pulmonary fibrosis, tuberculosis, and squamous cell carcinoma. We noted that 8 patients had received aminoglycosides, 12 had received diuretics, 3 had a history of diabetes, and 1 had a history of alcohol abuse. Of these, four patients had at least two risk factors (aminoglycosides plus diuretics) with one of the four also abusing alcohol. Table 1 shows the values of electrolytes in the patients receiving magnesium on day 1 and day 2. There was a transient elevation of serum magnesium level following magnesium infusion and this returned to baseline values within 28 h following the infusion. There were other significant differences in any other values of biochemical variables over the course of the study. canadian pharmacy mall
Figure 2 illustrates the mean values of VC, PEmax, and Pimax obtained immediately prior to the start of the magnesium infusion (Pre) compared to the first set of measurements obtained following completion of the magnesium infusion (Post). Mean values of VC, PEmax, Pimax, and handgrip for the entire group did not change significantly (p>0.05) following magnesium infusion. However, we had prospectively expected to find that only a subgroup of patients would show any changes with magnesium infusion, te, only those with intracellular magnesium deficiency would demonstrate any changes. We therefore analyzed these changes to determine if there was a separate subgroup of patients who showed large increases in these parameters following magnesium infusion. We found that the change in values from before to after magnesium infusion followed a pattern best described by a normal distribution for VC and Pimax (Fig 3). The changes in PEmax did not follow a normal distribution (p<0.05 by Shapiro-Francia test). We did not find a significant correlation between any combination of our evaluated factors and any improvement in VC seen following magnesium infusion. Most of our patients had reduced Pimax and PEmax prior to commencing the magnesium infusion.
Table 1—Biochemical Measurements in Patients Receiving Magnesium
Day 1 | Day 2 | |||||
Pre | Post | Post | Pre | Post | Post | |
Ionized calcium, mmol/L | 1.15 ±0.23 | 1.13±0.23 | 1.14±0.22 | 1.14±0.05 | 1.04±0.35 | 1.12 ±0.07 |
Total calcium, mmol/L | 1.93±0.28 | 1.91±0.28 | 1.89 ±0.26 | 2.08±0.11 | 2.08 ±0.14 | 2.05 ±0.12 |
Phosphate, mmol/L | 0.87 ±0.19 | 1.01 ±0.22 | 0.99 ±0.12 | 0.99 ±0.35 | 1.13±0.33 | 1.30±0.43 |
Sodium, mmol/L | 139 ±5 | 139 ±5 | 137 ±5 | 140 ±4 | 140 ±5 | 139 ±4 |
Potassium, mmol/L | 4.0±0.5 | 4.0±0.5 | 4.0±0.5 | 3.9±0.5 | 3.9±0.5 | 4.0±0.4 |
Bicarbonate, mmol/L | 31±6 | 33±6 | 32 ±5 | 32 ±7 | 32 ±5 | 33±4 |
Total protein, mmol/L | 52 ±5 | 54±5 | 52 ±5 | 46 ±20 | 51 ±21 | 52 ±22 |
Albumin, mmol/L | 24±4 | 25±3 | 24±4 | 23±3 | 23±4 | 23±3 |
Magnesium, mmol/L | 0.82 ±0.14 | 1.18±0.14t | 0.87 ±0.13 | 0.82 ±0.11 | 0.81 ±0.10 | 1.21 ±.13f |
Figure 2. Values of Pimax, PEmax, and VC in all patients before and after magnesium infusion. Vital capacity was measured in liters while Pimax and PEmax were measured in cm H20. These values were not significantly different following magnesium infusion.
Figure 3. The distribution in values of the change in PEmax, Pimax, and VC following magnesium infusion. The histograms for Pimax and VC followed a normal distribution while values for PEmax were not normally distributed. Note that there is no discernible bimodal pattern in any of the histograms.