The hemodynamic effects of intravenous ranitidine in intensive care unit patients: a double-blind prospective study.

The hemodynamic effects of intravenous ranitidine were studied in a prospective double-blind fashion in postoperative intensive care unit patients to determine if this H2 blocker produced the same transient fall in mean arterial pressure and systemic vascular resistance known to occur with cimetidine infusion. We found no statistically significant hemodynamic changes from baseline associated with infusion of 50 mg ranitidine over a 5-minute period. The different chemical ring structure of ranitidine and its effect on H2 vascular and cardiac receptors may account for these observations.

Cardiopulmonary effects of the head-down tilt position in elderly postoperative patients: a prospective study.

We studied the use of the head-down tilt position (Trendelenburg) in elderly postoperative patients in the intensive care unit to determine its effect upon cardiac and pulmonary function. Twenty-two patients (mean age 68.4 years) were placed in a 12 degrees head-down tilt position for 15 minutes. No deterioration was shown in any measured cardiac parameter; mean arterial pressure, cardiac index, and right and left ventricular stroke work increased significantly (P less than .05). Further, there were no observed changes in arterial or venous oxygenation, or in venous admixture. Because of the uncertain effect of the head-down tilt position upon cerebral blood flow, the routine use of this position is not recommended for the treatment of hypotension or during cardiopulmonary resuscitation. The results of this study, however, show that the cardiopulmonary effects are well tolerated if the position is required, as during central venous access procedures.

Effects of sodium bicarbonate in canine hemorrhagic shock.

We studied the use of sodium bicarbonate administration in a canine model of hemorrhagic shock to determine its effect on hemodynamics, arterial and venous blood gases, respiratory gases, and blood lactate levels. Thirteen dogs were anesthetized, paralyzed, mechanically ventilated, and hemodynamically monitored. Hypotension was induced and maintained at a mean arterial pressure of 40 to 45 mm Hg using controlled hemorrhage and reinfusion. After 2.5 h of shock, the dogs were randomized into two groups: one group (n = 6) received NaCl infusion; the other (n = 7) received sodium bicarbonate (1 mEq/kg followed by a continuous infusion of 2.5 mEq/kg.h for 2.5 h). CO2 production was increased in the alkali group, but there was no statistically significant difference between groups in any measured hemodynamic, blood gas, or respiratory gas variable. These included heart rate, BP, cardiac output, arterial and venous pH, CO2 production, and bicarbonate levels. Blood lactate levels, however, in the bicarbonate treated animals were significantly (p less than .01) higher than in the group treated with NaCl alone (10.1 +/- 3.2 vs. 5.1 +/- 1.2 mEq/L). These results are similar to the effects of bicarbonate found in other models of lactic acidosis, and suggest that bicarbonate therapy may have limited usefulness in the treatment of lactic acidosis.

Use of percutaneous gastrostomy in the intensive care patient.

We evaluated the use of percutaneous endoscopic gastrostomy in 30 ICU patients. There was a 14% incidence of minor complications, no major complications, and no mortality. We conclude that percutaneous endoscopic gastrostomy is a useful alternative to operative gastrostomy in the ICU patient.

A simple technique to accurately determine intra-abdominal pressure.

The determination of intra-abdominal pressure (IAP) may be useful in a variety of clinical situations. Despite this, invasive IAP monitoring is seldom performed due to the risks involved. Using a standard canine model of increased IAP, we evaluated the accuracy of transurethral bladder catheter pressure in reflecting IAP. Throughout the range of IAP studied (10 +/- 5 to 70 +/- 10 mm Hg), bladder pressure did not differ significantly from the direct measurement of IAP. We conclude that the measurement of bladder pressure using a standard transurethral bladder catheter provides an accurate determination of IAP.

Thrombocytopenia following peritonitis in surgical patients. A prospective study.

Thrombocytopenia is commonly found in patients with serious infection. To investigate this phenomenon, 14 consecutive patients (68 +/- 10 years) who underwent laparotomy for bowel perforation and culture-proven peritonitis were prospectively studied. Ten noninfected laparotomy patients served as a control group. None of the 10 control patients developed thrombocytopenia. Of the infected group, 12 of 14 patients (85%) developed thrombocytopenia (less than 100,000/mm3). One patient (9%) developed disseminated intravascular coagulation (DIC). Of the remaining 11 patients with thrombocytopenia, platelet counts fell from preoperative level of 350,000 +/- 166,000 to 54,000 +/- 30,000 (p less than 0.001) and reached this nadir 4.3 +/- 2 days after surgery. There was no statistically significant difference in prothrombin time, partial thromboplastin time, or fibrinogen levels before versus after operation in this group. Bleeding times in seven patients were 5.5 +/- 2 minutes, and bone marrow examination in five patients with platelet counts of less than 50,000/mm3 revealed normal or increased megakaryocytes. No patient in this group bled, had medications held, or received platelet transfusions. Platelet counts increased greater than 100,000/mm3 at a mean of 8.9 +/- 4.1 days after operation. It is concluded that thrombocytopenia is common following surgery for intra-abdominal infection, is not usually associated with DIC, clinical bleeding, or coagulation abnormalities, does not commonly result from bone marrow suppression, and is transient and does not require routine platelet transfusions.

Use of constant-infusion verapamil for the treatment of postoperative supraventricular tachycardia.

The effects of constant-infusion verapamil were studied in ten postoperative ICU patients who developed supraventricular tachycardia (atrial fibrillation) with rapid ventricular response rates. A 5-mg iv bolus dose of verapamil was followed by a 5-mg/h infusion that continued for 8 h. Ventricular rates were significantly (p less than .005) reduced from a pretreatment mean of 156 +/- 14 (SD) to 104 +/- 9 beat/min on constant-infusion therapy. This therapy was well tolerated without observed side-effects. Moreover, constant-infusion verapamil might avoid the hypotension and wide range of ventricular rates frequently encountered with repeated bolus doses of verapamil.