Niranjan Kissoon

Acid-base status of blood from intraosseous and mixed venous sites during prolonged cardiopulmonary resuscitation and drug infusions.

OBJECTIVESna) To determine the relationship of acid-base balance (pH, PCO2) of blood samples from the intraosseous and the mixed venous route during prolonged cardiopulmonary resuscitation; b) to compare the effect of separate infusions of epinephrine, fluid boluses, or sodium bicarbonate through the intraosseous sites on the acid-base status of intraosseous and mixed venous blood during cardiopulmonary resuscitation; and c) to compare pH and Pco2 of intraosseous and mixed venous blood samples after sequential infusions of fluid, epinephrine, and sodium bicarbonate through a single intraosseous site.nnnDESIGNnProspective, randomized study.nnnSETTINGnAnimal laboratory at a university center.nnnSUBJECTSnThirty-two mixed-breed piglets (mean weight, 30 kg).nnnINTERVENTIONSnPiglets were anesthetized and prepared for blood sampling and cardiopulmonary resuscitation. After anoxic cardiac arrest, ventilation was resumed and chest compression was resumed. Blood gas samples from the pulmonary artery and both intraosseous sites were obtained simultaneously at baseline, at cardiac arrest, and at 5, 10, 15, 20, and 30 mins of cardiopulmonary resuscitation for group 1 (control group) and after drug (epinephrine and sodium bicarbonate) and saline infusions via one of the intraosseous cannulas in groups 2 through 5.nnnMEASUREMENTS AND MAIN RESULTSnWe found no differences between intraosseous and mixed venous pH and Pco2 during periods of <15 mins of cardiopulmonary resuscitation. However, this relationship was not maintained during prolonged cardiopulmonary resuscitation and after bicarbonate infusion. After large volume saline infusion, the pH and Pco2 of mixed venous and intraosseous blood were similar. During epinephrine infusion, the relationship between intraosseous and mixed venous pH and Pco2 was similar to that found in the control group.nnnCONCLUSIONSnThe intraosseous blood sample could be used to assess central acid-base balance in the early stage of arrest and cardiopulmonary resuscitation of <15 mins. However, during cardiopulmonary resuscitation of longer duration, drug infusions may render the intraosseous site inappropriate for judging central acidosis.

Pharmacokinetics from multiple intraosseous and peripheral intravenous site injections in normovolemic and hypovolemic pigs.

ObjectivesTo examine: a) the rate and extent of delivery of radioactive tracers to the central circulation from the tibial, medial malleolar, distal femoral, and humeral intraosseous sites, as well as from a peripheral intravenous site; and b) the end-tidal CO2 response to injected sodium bicarbonate at these sites. DesignProspective, descriptive study. SettingAnimal laboratory at a university medical center. SubjectsTwenty anesthetized and mechanically ventilated piglets were cannulated with 18-gauge bone marrow needles at intraosseous sites and 22-gauge Teflon catheters in peripheral veins. A 22-gauge angiocath was placed in the right carotid artery of each subject. Drug kinetics were studied in the normovolemic and hypovolemic (acute bleeding of 25 mL/kg) states. InterventionsSodium bicarbonate (1 mEq/ kg) was injected into each of the three intraosseous and one intravenous sites with simultaneous monitoring of end-tidal CO2. A 10-min period for stabilization was allowed between injections. Aliquots of 99mtechnetium were injected at randomly selected sites and blood samples were obtained at 1.5-sec intervals via carotid artery for radioactive counts. Experiments were repeated after withdrawal of 25 mL/kg of blood. Measurements and Main ResultsAssessment by end-tidal CO2 monitoring after 1-mEq/kg injections of bicarbonate demonstrated a mean initial end-tidal CO2 increase at 12.8 secs and a mean maximal end-tidal CO2 increase of 8 torr (1.06 kPa), with no significant site differences noted. Radioactive tracer injections were detected in the carotid artery after 15.4 secs in normovolemic animals and after 21.4 secs in hypovolemic animals, with no significant site differences detected. The proportion of injected tracer at 2, 5, 10, 20, 30, and 40 mins identified no significant differences between various intraosseous and intravenous sites. ConclusionsOur study demonstrated similar rapid transit and proportion of bicarbonate and radioactive tracers, reaching the central circulation from multiple intraosseous sites and a peripheral intravenous site. This finding suggests that adjustments in drug dosage may not be required, using various intraosseous locations as an alternative to peripheral intravenous drug therapy. (Crit Care Med 1994; 22:838–843)

Comparison of pH and carbon dioxide tension values of central venous and intraosseous blood during changes in cardiac output

ObjectiveTo compare the pH and Pco2 values determined from of simultaneously corrected samples of central venous and intraosseous blood during sequential changes in cardiac output. DesignProspective, descriptive study. SettingAn animal laboratory in a university medical center. SubjectsFourteen mixed breed 4-wk-old piglets. InterventionsAnimals were anesthetized with ketamine hydrochloride and neuromuscular blockade was induced by the administration of pancuronium bromide. After endotracheal intubation and the institution of mechanical ventilation, a 4-Fr pulmonary artery catheter and a carotid artery cannula were inserted via a cutdown into the right neck of each piglet. A 16-gauge intraosseous needle was inserted into the anteromedial surface of the right tibia. Measurements and Main ResultsCentral venous and intraosseous blood gas samples were obtained simultaneously with thermodilution cardiac output measurements. Cardiac output measurements were as follows: during steady state (0.80 ± 0.14 L/min), after volume loading of 15 mL/kg (1.00 ± 0.25 L/min), after three successive bleeds of 15 mL/kg each at 30-min intervals (0.70 ± 0.28, 0.54 ± 0.22, and 0.43 ± 0.16 L/min, respectively) and at exsanguination (unrecordable). Paired t-tests demonstrated no significant differences in pH and Pco2 values between intraosseous and central venous samples under all study conditions. Limits of agreement for difference in Pco2 between sites, within the range of cardiac outputs studied, were −12.86 to 11.38 torr (-1.71 to 1.46 kPa) and for pH were −0.09 to 0.15. ConclusionsIntraosseous blood samples can be obtained without difficulty even during extreme hypovolemia. The pH and Pco2 values of intraosseous and central venous blood samples were similar under all study conditions. Intraosseous blood may be a useful alternative to central venous blood to assess tissue acid-base status during hemorrhagic shock and other low-flow states. (Crit Care Med 1994; 22:1010–1015)

Comparison of the acid-base status of blood obtained from intraosseous and central venous sites during steady- and low-flow states

Objective:To compare the acid-base status of blood obtained from the tibial intraosseous site with that status obtained from a central venous site during steady- and low-flow states in a piglet model. Design:A prospective, observational study. Setting:Animal laboratory at a university medical center. Subjects:Nine 2-day-old piglets. Interventions:Animals were anesthetized, intubated, and mechanically ventilated. A thermodilution pulmonary artery catheter was inserted via the right internal jugular vein and directed into the pulmonary artery. An arterial catheter was inserted into the right carotid artery and an intraosseous needle was inserted into the proximal tibial marrow cavity. Cardiorespiratory arrest was induced by discontinuation of ventilation. The animals were subsequently resuscitated by precordial compressions and ventilation. Blood samples were obtained from central venous and intraosseous sites during steady state and during resuscitation (low-flow state). Results:No significant differences (p < .05) were found for pH, PCO2, and bicarbonate concentration when values that were obtained from the central venous and intraosseous sites were compared during steady- and low-flow states. Conclusions:The acid-base status of intraosseous blood is similar to that status of central venous blood. Intraosseous blood gas values may be an acceptable alternative to central venous blood gas values in judging central acid-base status during cardiopulmonary resuscitation. (Crit Care Med 1993; 21:1765–1769)

Intraosseous and central venous blood acid-base relationship during cardiopulmonary resuscitation

Objective The objectives of this study were: 1) to determine whether obtaining intraosseous (IO) blood samples was practical during cardiopulmonary resuscitation (CPR), and 2) to compare the acid-base status (pH and partial pressure of CO2 (Pco2) of venous and IO blood during CPR. Design A prospective repeated measure study. Setting An animal laboratory at a university medical center. Interventions Nine mixed breed piglets (mean weight 43 kg) were anesthetized, tracheotomized, and placed on a ventilator (Siemens 900C Elema, Sweden). Placement of a pulmonary artery catheter was done via a surgical incision in the neck. An IO cannula was then placed in the tibial marrow cavity. The animals were positioned under a mechanical thumper (Thumper,™ Michigan Instruments, Grand Rapids, MI) for chest compressions. Blood gases were analyzed during steady state (baseline) after five minutes of ventricular fibrillation and during CPR at seven, nine, 11, 13, 15, and 18 minutes. Main results Blood samples for acid-base analysis were easily obtained from the IO sites during all sampling times. Mixed venous blood was slightly more acidic than IO blood, especially at 13, 15, and 18 minutes. However, there were no significant differences in pH and Pco2 values between IO and central venous (CV) gases at all time intervals except the Pco2. At nine minutes, a significant difference (P < 0.006) was found in Pco2 (59 ± 4 vs 47 ± 5 torr) for the CV versus IO sample, respectively. As the duration of CPR progressed, the differences in PCO2 between IO and CV sites were clinically relevant (though not statistically significant). Conclusion Obtaining blood from the IO site is practical during CPR. The divergence in values as CPR progresses suggests that, during longer periods of CPR, IO blood may reflect local acidosis and yield lower Pco2 and higher pH values that CV blood. This finding may limit the usefulness of IO blood to judge acid base status as CPR progresses.

Choosing a volume expander in critical care medicine.

The debate concerning the choice of crystalloids or colloids for resuscitation of the critically ill child is still unsettled. Moreover, the use of albumin in critically ill patients has been increasingly questioned because of the lack of clear-cut advantages over crystalloids as well as the concern for cost and the very minor risk of infection. Despite several meta-analyses addressing these issues, there is no data that supports the use of albumin unequivocally in any specific disease states. The suggestion that the use of albumin increases mortality in critically ill patients is not supported by data. There may be niche areas such as hypoalbuminic states, cirrhosis and burns where albumin may have distinct benefits. Alternatively synthetic colloids may be useful, however, concerns about coagulation problems and organ dysfunction persists.

Child with absent vital signs.

The outcome of cardiopulmonary resuscitation in the child with absent vital signs is dismal. Best outcomes therefore should rely on early recognition and aggressive management of critical illness to interrupt deterioration to cardiorespiratory arrest. Moreover, resuscitation entails a spectrum of care starting with cardiopulmonary resuscitation at the site of injury through critical care and post resuscitation rehabilitation. The resources required to provide this level of care is not available in many parts of the world. Therefore, resuscitation skills should be taught to caregivers at a level which is congruent to their role in the continuum of care and the use of aggressive resuscitation needs to be tailored based on geography, risk to medical personnel, preservation of resources, transplantation issues and expected outcomes. In some cases, the most prudent decision may be not to attempt resuscitation of the child with absent vital signs.

Cardiopulmonary resuscitation/Emergencies

The records of hospital in-patients at King Faisal Specialist Hospital and Research Center who received external cardiac massage as part of their cardiopulmonary resuscitation were reviewed. Success of resuscitation was analyzed as (1) short term (restoration of spontaneous circulation), and (2) long term (discharge from hospital). Of 234 such patients, 171 (73.1%) survived the initial resuscitation, and 66 (28.2%) were discharged. Success of outcome was not related to age, location of patient, time of day, or rhythm at arrest, including asystole. Longer resuscitation time was associated with less chance of restoration of spontaneous circulation (p<0.001), but not associated with Hospital discharge rate. Results for patients with congenital heart disease were similar to those with other medical or surgical conditions. In this series, 36.7% of ward in-patients survived to discharge, compared to two other series where the results were 9% and 15% Overall, 38 7% of patients who survived the initial resuscitation were discharged from hospital Where resuscitation continued for more than 30 minutes, 18.9% of patients had long term survival. Outcome from asystole was no worse than for other cardiac rhythms. We believe that previous reports of poor outcome from asystole in pediatric cardiac arrest should not influence decisions to stop resuscitation for pediatric in-patients prematurely. Successful restoration of spontaneous circulation with long term survival can be achieved after prolonged resuscitation. 045